ISMRM 23rd Annual Meeting & Exhibition • 30 May - 05 June 2015 • Toronto, Ontario, Canada

Traditional Poster Session • Pulse Sequences & Reconstruction
2370 -2375 Pulse Sequences - Spectroscopy
2376 -2386 B1 Imaging
2387 -2402 RF Pulse Design
2403 -2412 Multi-Band MRI
2413 -2452 Parallel Imaging
2453 -2470 Encoding & Reconstruction
2471 -2483 Image Processing and Analysis
2484 -2489 Novel Computing Frameworks
2490 -2498 Image Quality Assessment
2499 -2504 Dictionary-Based Reconstruction
2505 -2516 Imaging Near Metal
2517 -2530 Elastography
2531 -2531 Mapping Magnetism using Magnetoencephalography
2532 -2546 Multi-Scale Motion
2547 -2564 Motion Correction Head
2565 -2579 Motion Correction - Body

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2370.   Ultra-High Resolution 3D 1H-MRSI of the Brain: Subspace-Based Data Acquisitions and Processing
Fan Lam1, Bryan Clifford1, Chao Ma2, Curtis L. Johnson2, and Zhi-Pei Liang1
1Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 2Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, United States

This paper presents a novel data acquisition and processing method for subspace-based MRSI to enable ultra-high resolution 3D 1H-MRSI of the brain. Results from both phantom and in vivo experiments will be shown to demonstrate the unprecedented capability of the proposed method.

2371.   Acceleration of Chemical-Shift Imaging by Applying True 3D Compressed Sensing
Jian-Xiong Wang1,2, Matthew E Merritt1,2, A Dean Sherry1,2, and Craig R Malloy1,2
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States, 2Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, United States

By applying 3D compressed sensing (CS) method to accelerate the acquisition time of chemical-shift imaging (CSI) which doesn’t possess the sparseness required by conventional 2D slice type CS. When the entire CSI data set is treated as one unity, CS can be satisfactorily applied to spectroscopic CSI to reduce acquisition time which is very desirable for possible multiple CSI acquisition during the lifetime of hyperpolarized agent for metabolic dynamic analysis such as Hyperpolarized 13C metabolism research.

2372.   Fast Sodium MRI of the Human Brain Using a Balanced Steady-State Free Precession Sequence
Ruomin Hu1, Simon Konstandin2, and Lothar R. Schad1
1Computer Assisted Clinical Medicine, Heidelberg University, Mannheim, Baden-Württemberg, Germany, 2MR-Imaging and Spectroscopy, University of Bremen, Bremen, Bremen, Germany

Sodium magnetic resonance imaging sets its focus of research primarily on the measurement of tissue sodium concentration with the attempt to distinguish between intra- and extracellular space. An alternative is represented by sodium imaging exhibiting relaxation-based contrast. The main goal of this work is to develop a sequence to explore the feasibility and properties of relaxation-based sodium imaging using phantoms as well as in vivo. Structural changes of the macromolecular environment such as the demyelination of axons and the degradation of cartilage might be highlighted using this contrast-generating technique.

2373.   SPatiotemporal ENcoded Spectroscopic Imaging (SPENSI) a New Approach for Multi & Single Scan Spectral Imaging
Amir Seginer1, Rita Schmidt1, and Lucio Frydman1
1Chemical Physics Department, Weizmann Institute of Science, Rehovot, Israel

We introduce a new method for fast spectral-imaging which avoids folding-in of spetra from outside of the spectral-BW, and which can be accelerated to a single-shot acquisition when specific spectral points are of intereset. The new method borrows a spectral encoding block from ultrafast 2D NMR spectroscopy (Frydman et al.), allowing a 1D-spatial / 1D-spectral “image” to be collected using an EPI-like acquisition with blips along the “spectral” dimension. Examples are given for breast imaging at 3T, separating tissue, fat, and silicone implant; and at 14T, separating five peaks spanning about 3kHz. Under work is an application to hyperpolarized dynamic imaging.

2374.   Model-Based Reconstruction of Hyperpolarized [1-13C]-Pyruvate
James Bankson1, Christopher Walker1, Wolfgang Stefan1, David Fuentes2, Matthew Merritt3, Yunyun Chen4, Craig Malloy3, Dean Sherry3, Stephen Lai4, and John Hazle1
1Department of Imaging Physics, UT MD Anderson Cancer Center, Houston, TX, United States, 2UT MD Anderson Cancer Center, Department of Imaging Physics, Houston, TX, United States, 3Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States, 4Department of Head & Neck Surgery, UT MD Anderson Cancer Center, Houston, TX, United States

Hyperpolarized (HP) MRI has enabled observation of biochemical processes in vivo with unprecedented resolution and specificity. These measurements are challenging due to the transient and non-renewable nature of HP signal enhancement, and the need to distribute dynamic spatial observations over a sufficient span of time to allow substrate interaction with biological targets. We have developed a kinetic model to describe the evolution of HP [1-13C]-pyruvate in vivo, and integrated this model into a constrained reconstruction algorithm exploits prior information from 1H MRI and allows estimation of under-sampled dynamic HP imaging data as continuous functions of position and time.

2375.   Efficient detection of bound potassium and sodium using TQTPPI pulse sequence
Victor D. Schepkin1, Boris M. Odintsov2, Ilya Litvak1, Peter L. Gor'kov1, William W. Brey1, Andreas Neubauer3, and Thomas F. Budinger4
1NHMFL/FSU, Tallahassee, Florida, United States, 2UIUC, Illinois, United States, 3Heidelberg University, Germany, 4LBNL/UCB, California, United States

A novel way to detect bound potassium and sodium in vivo was explored based on triple quantum signals without filtration. The method is based on time proportional phase increments, allowing the detection of bound ions as a separate peak on triple frequency relative to single quantum MR signals. Bound ions signals are acquired in the same way and efficiently for a wide range of binding strengths. This is advantageous compared to typical TQF methods, especially during diseases or interventions. A comparison of TQTPPI signals in rat head revealed almost two times more effective binding of potassium relative to sodium.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2376.   Transmit Field Estimation from K-space Data
Yu Ding1 and Jinghua Wang2
1Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio, United States, 2Center for Cognitive and Behavioral Brain Imaging, The Ohio State University, Columbus, Ohio, United States

Imaging of large objects at high field generally introduces large signal inhomogeneity associated with wavelength effect, object configuration and object electromagnetic properties. Estimating transmit field B1+ maps is prerequisite for various techniques (such as RF shimming, parallel excitation and inhomogeneity correction) to mitigate signal inhomogeneity, quantitative MR imaging and electrical property mapping. The status quo gold standard utilizes pixel-wise division which could be problematic when the image SNR is low. Here we explored the feasibility of estimating B1+ maps accurately, rapidly and robustly in k-space domain using a convolution kernel.

2377.   Slice profile corrections in the XFL (magnetization-prepared turbo-FLASH) B1-mapping sequence
Alexis Amadon1, Franck Mauconduit2, Alexandre Vignaud1, and Nicolas Boulant1
1I2BM / NeuroSpin / UNIRS, CEA, Gif-sur-Yvette, France, France, 2Siemens Healthcare, Saint-Denis, France, France

The XFL sequence is a very fast 2D multi-slice B1-mapping sequence relying on the measurement of the magnetization Flip Angle (FA) of a selective preparation saturation pulse immediately preceding a centric-ordered FLASH readout. Like most 2D B1-mapping sequences, imperfect slice profiles introduce biases in the B1 measurement. Here we correct for this bias by taking into account the preparation & imaging slice profiles as well as the B0 offset map.

2378.   Fast 3D Algorithm for Coil Localization as an Aid in Estimation of B1 Distribution
Parnian Zarghamravanbakhsh1, John M Pauly1, and Greig Scott1
1Electrical Engineering, Stanford University, Stanford, CA, United States

Prior knowledge of magnetic field distribution is necessary for RF shimming and calibration.In practice, sample loading change coil current ,also field pattern tends to vary with relative location of coil to sample. In this study, we assess a method to localize transmit coil in imaging space by placing fiducial markers on known location of coils. Then the optimal rotation and translation matrix is calculated for mapping the target regions from simulation to imaging space. knowing coil location B1 estimation of region of interest can be computed by FDTD based simulation. Knowledge of field pattern estimation along coil current sensor can be used in auto-calibration PTx systems.

2379.   In vivo comparison of B1 mapping techniques for hip joint imaging at 7 Tesla
Oliver Kraff1, Andrea Lazik1,2, Daniel Brenner3, Desmond H.Y. Tse4,5, Qi Duan6, Soeren Johst1, Harald H. Quick1,7, and Mark E. Ladd1,8
1Erwin L. Hahn Institute for MRI, University Duisburg-Essen, Essen, Germany, 2Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Germany, 3German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany, 4Neuropsychology and Psychopharmacology, Maastricht University, Netherlands,5Radiology, Maastricht University MC, Netherlands, 6Adv. MRI Section, LFMI, NINDS, National Institutes of Health, MD, United States, 7Highfield and Hybrid MR Imaging, University Hospital Essen, Germany, 8Medical Physics in Radiology, German Cancer Research Center (DKFZ), Germany

Three well-established B1 mapping techniques (AFI, BSS, and DREAM) were evaluated regarding quality and reproducibility for large cross-section mapping in vivo at 7 Tesla. B1 maps were obtained in 6 healthy volunteers with two standard RF shims applied (CP+ and CP2+) using an eight-channel transmit/receive RF body coil. Deviation between scan and rescan for mean B1 and maximum B1, as well as the mean ratio of zero to nonzero values within the maps were assessed to compare the methods and to rate their applicability for functional imaging of the hip joints at 7T.

Optimal flip angle and signal shaping for single-shot volumetric DREAM B1 mapping
Rüdiger Stirnberg1, Daniel Brenner1, and Tony Stöcker1,2
1German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany, 2Department of Physics and Astronomy, University of Bonn, Bonn, Germany

The use of a unique steady-state flip angle for optimal signal shaping in 3DREAM, a volumetric single-shot B1 mapping method, is investigated. While free-induction-decay signals are shaped constantly when employing the proposed flip angle, the predictable exponential decay of stimulated echoes is shown to act as a 2D Gaussian filter on the stimulated echo image due to a spiral-out k-space view-ordering. This filter can be well estimated and employed post-hoc to the free-induction-decay image to equalize resolution properties. This is shown to improve derived B1 maps. The findings are transferable to conventional, slice-selective DREAM B1 mapping.

2381.   Robust implementation of 3D Bloch Siegert B1 mapping
Andreas Lesch1, Andreas Petrovic1, and Rudolf Stollberger1
1Department for Medical Engineering, Graz University of Technology, Graz, Styria, Austria

This work describes time varying systematic errors of the Bloch-Siegert B1 mapping technique resulting from system instabilities and describes a robust implementation. The drift in resonance frequency due to hardware imperfections is shown for different preloads of the scanner and the corresponding measurement errors are determined for the conventional Bloch-Siegert acquisition and comparison with a reference method. By appropriate implementation the adverse influences can be suppressed.

2382.   Fast Low-Angle B1 Mapping
Caroline Le Ster1,2, Giulio Gambarota1, Eric Brillet3, Olivier Beuf4, and Hervé Saint-Jalmes1,5
1INSERM UMR 1099, Université de Rennes 1, Rennes, France, 2Siemens Healthcare, Saint-Denis, France, 3Department of Imaging, Rennes University Hospital, Rennes, France, 4Université de Lyon, CREATIS, CNRS UMR 5220, INSERM U1044, INSA-Lyon, Université Lyon 1, Villeurbanne, France, 5Centre Eugène Marquis, CRLCC, Rennes, France

Quantitative MR methods often require the knowledge of the local B1 field. Many B1 mapping methods have been developed, but few of them are suited to measure low flip angles. Here we use the Low Angle Method1 coupled with EPI (LAM EPI) to acquire multislice B1 maps on a phantom and in vivo on the brain and the abdomen (breathold acquisition). We compare our results to the reference B1 mapping Double Angle Method² (DAM) and the classical LAM method (LAM FLASH).

2383.   Spin echo B1+ mapping in high susceptibility tissues
Eamon Doyle1,2, Jonothan Chia3, Krishna Nayak1,4, and John C Wood1,2
1Biomedical Engineering, University of Southern California, Los Angeles, CA, United States, 2Cardiology, Children's Hospital of Los Angeles, Los Angeles, CA, United States,3Philips Healthcare, Cleveland, OH, United States, 4Electrical Engineering, University of Southern California, Los Angeles, CA, United States

Phase-based B1+ mapping methods fail in high susceptibility tissues with rapid decay. We propose using spin echo-based magnitude B1+ mapping techniques to map iron-loaded tissues incompatible with other methods.

2384.   Comparing Bloch-Siegert B1+ Mapping using Single Channel and Channel Combination Tx Methods
Mohammad Mehdi Khalighi1, Gaohong Wu2, and Qin Liu2
1Applied Science Lab, GE Healthcare, Menlo Park, CA, United States, 2MR Engineering, GE Healthcare, Waukesha, WI, United States

The adiabatic Bloch-Siegert B1 mapping is optimized for single channel transmit and channel combination transmit methods. Phantom comparison shows that single channel transmit has a better SNR for B1+ magnitude and phase. The two methods are also compared in parallel transmit application with a 3-spoke pTx RF pulse design where it is shown that single channel transmit method results in a better homogeneity. It is concluded that unlike DAM and AFI, the single channel transmit method is preferred over channel combination for B-S B1 mapping.

2385.   Characterizing in vivo B1 Maps at 7T using the Kolmogorov-Smirnov Test
Douglas A C Kelley1
1Neuro Apps and Workflow, GE Healthcare, San Francisco, CA, United States

At 7T and higher field strengths, mapping the B1 field is generally required to optimize the transmitter gain for a particular application. Characterizing these maps -- both determining whether the map is "normal" and identifying the relevant gain setting -- requires a simple, fast, and robust statistical analysis. The Kolmogorov-Smirnov test is here shown to be a good candidate for such a test.

2386.   B1 mapping of the breast with a reference tissue method
Federico D Pineda1, Milica Medved1, Xiaobing Fan1, and Gregory Karczmar1
1Radiology, The University of Chicago, Chicago, IL, United States

Accurate measurements of the B1 field are critical in DCEMRI of the breast as small errors in the flip angle can lead to significant bias in measurements of T1, contrast media concentration, and pharmacokinetic parameters. We present a novel method for mapping the B1 field across the breast. This method is based on the fact that the T1 of fat in the breast can be accurately measured and has very low inter/intra-patient variability. The reference T1 in each image voxel is used to calculate local B1. Then the full B1 map is estimated. These maps were used to produce improved estimates of native T1

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2-spoke placement optimization under explicit SAR and power constraints in parallel transmission at ultra-high field
Laura Dupas1, Aurélien Massire1, Alexis Amadon1, Alexandre Vignaud1, and Nicolas Boulant1
1NeuroSpin, CEA, Saclay, Ile de France, France

The simultaneous optimization of 2-spoke trajectories and RF-waveforms in the Magnitude Least Squares problem in parallel transmission is performed under explicit SAR and power constraints for axial slices of the human brain at 7 T. After making the observation that only the vector between the 2 spokes is relevant for the MLS cost-function, an active-set algorithm optimizes both the RF-weights and this vector starting from a large set of initial k-space candidates. A final normalized root mean square error of less than 2 % is systematically returned for 4 volunteers’ datasets. Bloch simulations and in-vivo T2*-weighted images validate the approach.

2388.   Does the best distance beween 2 spokes match the inverse RF wavelength ?
Alexis Amadon1, Laura Dupas1, Alexandre Vignaud1, and Nicolas Boulant1
1I2BM / NeuroSpin / UNIRS, CEA, Gif-sur-Yvette, France, France

The spoke pair k-space trajectory is known to be efficient to compensate for B1 inhomogenity in tailored slice selection at ultra high field. In the Magnitude Least Squares problem, the parameter of interest is the distance between the 2 spokes. The optimal distance is analysed across different human brains and slices at 7T. It seems to be fairly constant and its inverse is shown to roughly match the RF wavelength in the human brain.

2389.   Off-resonance compensated velocity selective RF pulse design for reducing signal dropout in vessel wall imaging
Yunduo Li1, Shuo Chen1, Zechen Zhou1, Rui Li1, and Chun Yuan1,2
1Center for Biomedical Imaging Research, Beijing, Beijing, China, 2Department of Radiology, University of Washington, Seattle, Washington, United States

In this study, we improved the design of velocity-selective RF pulse to compensate signal dropout due to off-resonance effect and evaluated its feasibility in carotid vessel wall imaging. Simulation and in-vivo studies showed that the new VS pulse can partially compensate the signal dropout in static tissue, which results in better image quality and contrast. As improved VS pulse widened the pass band of VS profile, which sacrificed blood suppression efficiency in case of slow blood flow causing image artifacts (Fig.4). A trade-off between off-resonance compensation and blood suppression efficiency should be considered to relief off-resonance with efficient blood suppression.

2390.   Parallel 2D excitation of thin limited slice profiles
Denis Kokorin1, Jürgen Hennig1, and Maxim Zaitsev1
1Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany

The concept of parallel excitation allows for substantial shortening of multidimensional pulses designed for selection of arbitrarily-defined regions of interests. In this work, the use of accelerated 2D pulses is investigated experimentally for excitation of slice profiles with a limited FOV. The excitation trajectories used were based on EPI traversals in transmit k-space and were undersampled by skipping the PE lines. The feasibility of PEX was tested in a phantom on a 3T MRI system with 8 RF channels. The advantages and disadvantages of different Cartesian encoding schemes are compared based on the experimental data obtained.

2391.   Hybrids of Static and Dynamic RF Shimming for Body Imaging at 7T
Martina Flöser1,2, Andreas Bitz1, Sören Jost2, Stephan Orzada2, Marcel Gratz2, Oliver Kraff2, and Mark Ladd1,2
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Erwin L. Hahn Institute for MRI, University Duisburg-Essen, Essen, Germany

Dynamic RF shimming can mitigate B1+ inhomogeneities that hamper body imaging at high field strength. A large number of independent transmit channels offers more degrees of freedom but makes the system complex and expensive. Therefore, we propose to combine several transmit elements to adaptive elements that are excited by fully modulated Tx channels. The amplitude and phase weightings within an adaptive element, but not the pulse shape, are variable. We present a method to optimize the amplitude and phase weightings and evaluate the performance of the hybrid shimming strategy based on simulated B1 maps.

2392.   Influence of 2-spoke pulses k-space placement in different optimization strategies and cost functions
Laura Dupas1, Alexis Amadon1, Aurélien Massire1, Alexandre Vignaud1, and Nicolas Boulant1
1NeuroSpin, CEA, Saclay, Ile de France, France

The impact of 2-spoke k-space placement is investigated for different pulse performance metrics and algorithms (under strict SAR and power constraints): the Least Squares problem with the Active-Set (AS) algorithm, the Magnitude Least Squares (MLS) problem with the Variable-Exchange method and the MLS problem with AS. After demonstrating that the MLS cost-function depends only on the vector between the two spokes in the small tip angle approximation, numerical simulations with in vivo data acquired at 7T on a human brain show that RF pulse performance is excellent and robust over surprisingly large regions of k-space.

2393.   Slice-selective adiabatic T2 preparation using a modified STABLE pulse
Hadrien Dyvorne1 and Priti Balchandani1
1Radiology, Icahn School of Medicine at Mount Sinai, New York, NY, United States

We propose a new adiabatic T2 preparation module that achieves B1-insensitive slice-selective T2 contrast by employing a modified slice-selective tunable-flip adiabatic low peak-power excitation (STABLE) RF pulse. We investigate the performance of STABLE T2 preparation against conventional non-selective T2 preparation for T2-weighted brain imaging at 7T.

2394.   Multiband arbitrary-phase SLR RF pulse with generalized flip angle via convex optimization
Hong Shang1,2, Peder E.Z. Larson1,2, Adam B. Kerr3, Galen Reed4, Adam Elkhaled1,2, Jeremy W. Gordon1, Cornelius von Morze1, Michael Lustig5, and Daniel B. Vigneron1
1Radiology and Biomedical Imaging, UCSF, San Francisco, California, United States, 2UCSF-UC Berkeley Graduate Program in Bioengineering, San Francisco/Berkeley, California, United States, 3Electrical Engineering, Stanford University, Stanford, California, United States, 4HeartVista, Menlo Park, California, United States, 5Electrical Engineering and Computer Science, UC Berkeley, Berkeley, California, United States

A framework for general RF pulse design is developed based on convex optimization. It can create an RF pulse with multiband magnitude profile, arbitrary phase profile and generalized flip angle. Spectral profile sparsity is exploited to further optimize pulse characteristics such as duration, transition width and SAR with flexible trade-off among them. Designs for specialized excitation RF pulses for balanced SSFP C-13 MRI and a dualband saturation RF pulse for H-1 MR spectroscopy were developed and tested.

2395.   Design and optimization of fast imaging pulse sequences using optimal control theory.
Oleksandr Khegai1, Jiun-Jie Wang2, Steffen J Glaser3, and Florian Wiesinger4
1Healthy Aging Research Center, Chang Gung University, Taipei, Taiwan, 2Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taipei, Taiwan,3Department of Chemistry, Technische Universität München, Munich, Germany, 4Diagnostics and Biomedical Technologies Lab, GE Global Research Europe, Munich, Germany

In this work we demonstrate the feasibility of the optimal control pulse sequence optimization, which allows to design as an energetically favorable RF pulse sequence that generates stable echo train with a high total or predefined MR signal at acquisition time points and brings the magnetization to the desired final distribution for certain CS offset and B1 field inhomogeneity.

2396.   Fully-refocused SPatio-temporal ENcoding (SPEN) MRSI using Fourier-Encoding Polychromatic Spectral Pulses
Zhiyong Zhang1,2 and Lucio Frydman1
1Chemical Physics Department, Weizmann Institute of Science, Rehovot, Israel, 2Department of Electronic Science, Xiamen University, Xiamen, Fujian, China

Fully refocused SPatiotemporal ENcoding (SPEN) imaging has recently been shown to provide a robust alternative to EPI –erasing T2* and chemical-shift effects from a single-scan image. Despite this cancelling of shift effects, we show how utilizing a polychromatic refocusing pulse can lead to a Fourier-encoded fully refocused SPEN sequence which can map chemical shifts with high temporal efficiency while maintaining the robustness of fully-refocused SPEN. These SPEN spectroscopic images are decoded by a Fourier transform procedure into resonance-specific images. The usefulness of this PC-SPEN approach is demonstrated on a metabolite phantom and in vivo water-fat separation imaging at 7 T.

2397.   SAR reduced excitation by joint design of RF pulse and slice selective gradient shape
Christoph Stefan Aigner1, Christian Clason2, Armin Rund3, and Rudolf Stollberger1
1Institute of Medical Engineering, Graz University of Technology, Graz, Austria, 2Faculty of Mathematics, University of Duisburg-Essen, Essen, Germany, 3Institute for Mathematics and Scientific Computing, University of Graz, Graz, Austria

Radio frequency (RF) pulses are essential in MRI to excite and alter magnetization. We present a flexible approach based on optimal control of the full time-dependent Bloch equation for joint optimization of RF pulse and slice selective gradient. A globally convergent trust-region Newton method with exact derivatives via adjoint calculus allows the efficient computation of optimal pulses. The results are validated on a 3T scanner and demonstrate the ability to generate optimized waveforms for large flip angles with highly reduced RF power.

2398.   Optimized Amplitude Modulated Multi-Band RF pulses
Shaihan J Malik1,2, Anthony N Price2, and Joseph V Hajnal1,2
1Division of Imaging Sciences and Biomedical Engineering, Kings College London, London, London, United Kingdom, 2Centre for the Developing Brain, Kings College London, London, United Kingdom

The modulation required to produce multi-band RF pulses can lead to unacceptably high peak RF power. This can be alleviated by optimising the phase of each simultaneously excited slice. The result is typically a rapid amplitude and phase modulation. Faithful reproduction of rapid phase modulation can be error prone, especially on systems requiring frequency modulation to be defined by the pulse designer. These issues can be sidestepped if pulses are amplitude modulated (AM) only; here we identify optimal slice phases that reduce peak RF power using strictly AM MB pulses and compare them with the more general solutions.

2399.   SLR Pulse Implementation in Multi-Slice 2D FLASH Pulse Sequence for 3T MRI and Beyond
A Alhamud1, Jay Moore2, Neal Derman1, Ernesta Meintjes1, and Marcin Jankiewicz1
1Human Biology,MRC/UCT Medical Imaging Research Unit, University of Cape Town, Cape Town, Western Cape, South Africa, 2Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States

Excitation part of 2D FLASH multi-slice sequence is replaced by a train of slice-selective SLR-pulses with built-in |B1+|-insensitivity. Performance of the re-designed sequence, measured in SNR gain over sequence with a standard excitation waveform, is verified in-vivo experiment in human head at 3 Tesla. The gain is substantial (up to 60% more SNR is observed) in inhomogeneity-challenged areas even when slice-profile of the standard waveform favors it over the optimized alternative . This modification to FLASH sequence represents a simple way in which image quality can be improved in various MR modalities (including fMRI, DTI and spectroscopy) in case where quality is corrupted byRF and static field inhomogeneities.

2400.   Rapid 3D-FFE MR Image Acquisition using Aliased k-space Acquisitions
Indrajit Saha1 and Rakesh Kumar Gupta2
1Philips Healthcare, Philips India Ltd, Gurgaon, Haryana, India, 2fortis memorial research institute, Gurgaon, India

ewly developed MRI scan acceleration method RATE showed promises to speed-up MRI scans while preserving acquisition SNR through simultaneous acquisitions of distinct k-space phase encodes. We present our ongoing work of implementation of aliased k-space acceleration techniques in 3D MRI acquisitions with the goal of accelerating 3D dynamic MRI acquisitions. Our preliminary implementation of RATE to accelerate 3D-FFE sequence was able to produce two fold of reduction in scan time. Our ongoing work will involve developing strategy to achieve even higher acceleration factors for 3D T1 acquisitions including testing the performance of the sequence on healthy subjects.

2401.   Contrast Variation in UTE imaging with very short RF pulse duration
Chanhee Lee1, Soon Ho Yoon2, Jin Mo Goo2, and Jang-Yeon Park1
1Biomedical Engineering, IBS Center for Neuroscience Imaging Research, Sungkyunkwan University, Suwon, Gyeonggi, Korea, 2Radiology, Seoul National University College of Medicine, Seoul, Korea

In this study, we show that image contrast in UTE imaging can also be affected by changing RF pulse type and its duration, not solely by changing TR, and FA, due to the magnetization-transfer (MT) effect. This was demonstrated by simulation and human brain imaging.

2402.   Steady-state imaging with 3D inner volume excitation
Hao Sun1, Jeffrey A. Fessler1, Douglas C. Noll2, and Jon-Fredrik Nielsen2
1Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, United States, 2Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States

Steady-state gradient echo sequences are generally not suitable for reduced field of view (rFOV) imaging using 3D tailored excitation pulses, due to the long duration of conventional 3D RF pulses. Recently, a method for joint RF pulse and continuous k-space trajectory design was proposed that produces tailored RF pulses capable of exciting a non-smooth 3D pattern even with a single RF coil and short pulse duration (e.g., 4 ms). However, it is unknown whether this RF pulse is sufficiently accurate for rFOV steady-state imaging since even small residual flip angles outside the rFOV can lead to relatively large steady-state signal. In this work, we evaluate using the joint RF pulse design method in for Inner Volume excitation (IVex) in three steady state sequences: RF-spoiled gradient echo (SPGR), balanced SSFP (bSSFP), and the recently proposed Small-Tip Fast Recovery (STFR) sequence. STFR can produce similar tissue signal and contrast as bSSFP, however we hypothesized that the outer-volume signal for IVex-STFR and IVex-bSSFP may differ.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

Multiband Imaging Method for Metal Artifact Correction with 3D Multi-Spectral Imaging
JaeJin Cho1, Dongchan Kim1, Hyunseok Seo1, and HyunWook Park1
1Department of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Chungcheong, Korea

In conventional MRI, metallic implants generate severe geometric artifacts so that images cannot be used in diagnosis. In recent years, 3D-MSI methods such as SEMAC and MAVRIC have significantly improved image quality near metallic implants. However, 3D-MSI needs very long imaging time to acquire several spectral bins for covering whole distorted magnetic field. Multiband imaging technique could be one of the solutions for shortening the imaging time of 3D-MSI. Multiband imaging acquires the signal of multiple spectral bins simultaneously so that the number of excitations decreases. In this paper, multiband 3D-MSI method will be proposed for accelerating the imaging speed.

2404.   A multi-band spatial spectral selective excitation RF design
Yajun Ma1, Bing Wu2, Wentao Liu1, Weinan Tang1, and Jia-Hong Gao1
1Center for MRI, Peking University, Beijing, Beijing, China, 2GE Healthcare MR Research China, Beijing, China

we propose a RF design that may achieve both multi-band as well as SPSP selection to meet the needs of fast imaging and fat saturation while improving the time-bandwidth efficiency compared to conventional SPSP approach.

2405.   caipirinha using the RF pulse modulation with random phase for multiband imaging
Changheun Oh1, Dongchan Kim2, and HyunWook Park2
1Korea advanced institute of science and technology, Daejeon, Daejeon, Korea, 2Korea advanced institute of science and technology, Daejeon, Korea

In multi-band imaging technique, we propose a new multi-band imaging technique by using the RF pulse modulation with random phase to make uncorrelated aliasing pattern. To make the controlled aliasing for multi-band imaging, we make the RF pulse modulated with random phases. The phases are increasing by Golden Ratio, and the sets of phases are segmented by Fibonacci numbers and randomly reordered. Randomly distributed aliasing pattern can be reduced by using CS reconstruction. In this paper, experimental results with acceleration factor 6 are shown.

2406.   Pre-scan with half-sized phase encoding blips reducing ghost and slice leakage artifacts in dual-band EPI
Hiroshi Toyoda1, Naoya Yuzuriha2, Sosuke Yoshinaga2, and Hiroaki Terasawa2
1Center for Information and Neural Networks, National Institute of Information and Communications Technology, Suita, Osaka, Japan, 2Department of Structural BioImaging, Kumamoto University Graduate school of Pharmaceutical Sciences, Kumamoto, Japan

The purpose of this study was to reduce ghost artifacts due to phase correction error and to reduce slice leakage artifacts in dual-band EPI, using pre-scans with a half-sized phase encoding (PE) blips technique. A phantom and in vivo rat brains were scanned using a custom single-shot dual-band 2D-EPI sequence with blipped-controlled aliasing (CAIPI) on a 7T animal scanner. The pre-scans with half-sized PE blips were useful to achieve accurate phase correction in EPI, and to estimate coil sensitivity profiles for each slice, resulting in the reduction of slice leakage artifacts in dual-band EPI with CAIPI.

2407.   Hadamard and Sensitivity Encoding (H-SENSE) for Simultaneous Multi-Slice MR Imaging
Jong-Min Kim1, Junyong Park2, Chulhyun Lee2, and Chang-Hyun Oh1
1Electronic and information engineering, Korea University, Seongbuk-Gu, Seoul, Korea, 2The MRI Team, Korea Basic Science Institute, Chungchungbuk-Do, Korea

A new two-step approach to simultaneously acquire multi-slice MR images (SMI) is proposed. Simultaneously excited slices are simultaneously encoded by using Hadamard matrix (HE)1 and parallel encoding method such as SENSE2. As previously reported, HE and SENSE for SMI is useful in many applications3, 4. However these method has low temporal resolution and/or high g-factors. The proposed Hadamard and Sensitivity encoding (H-SENSE) for SMI seems to be useful to overcome these limitations by optimally choosing slice combinations for SENSE coding. Furthermore, an optimal Hadamard coding combination for better SNR with g-factor reduction.

2408.   A GRAPPA Reconstruction for Simultaneous Multi-Slice Radial Acquisition
Weiran Deng1, Kyoko Fujimoto1, and V. Andrew Stenger1
1University of Hawaii JABSOM, Honolulu, HI, United States

The prolonged scan time in radial imaging can be reduced using a Simultaneous Multi-Slice (SMS) CAIPIRINHA-like acquisition. A reconstruction based on the framework of GRAPPA for SMS radial acquisition is presented. This reconstruction method is computationally fast and practical for online implementation on the MRI scanner.

2409.   Ghost-correcting SENSE reconstruction for multi-band EPI
Franciszek Hennel1, Aline Seuwen1, Constantin von Deuster1, and Klaas P. Pruessmann1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

Separation of slices simultaneously acquired in multi-band EPI is problematic when the “N/2 ghost” needs different correction parameters for different slices. We present a straightforward manner of combining the slice-dependent ghost correction with multiband SENSE. The method inverts the sensitivity encoding equations for separately reconstructed even- and odd-echo data. It achieves a significant complexity reduction compared to the previously proposed k-space-based approach.

2410.   2D-SENSE-GRAPPA For Fast, Ghosting-Robust Reconstruction of In-Plane and Slice Accelerated Blipped-CAIPI-EPI
Peter Jan Koopmans1, Benedikt A Poser2, and Felix A Breuer3
1FMRIB Centre, University of Oxford, Oxford, United Kingdom, 2Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands, 3Research Center Magnetic Resonance Bavaria, Wurzburg, Germany

2D-SENSE-GRAPPA is presented as a method to reconstruct in-plane accelerated simultaneous multislice data in a single step rather than sequentially unaliasing each dimension. Following a recent adaptation of Sice-GRAPPA by Setsompop et al, the method uses different kernels for the odd and even lines of k-space to ensure robustness against EPI N/2 ghosting. Reconstruction quality is very similar to Sice-GRAPPA but owing to its one-step approach, 2D-SENSE-GRAPPA has the potential to reduce calculation times which are becoming a problem in fMRI and DTI.

2411.   Multi-band PROPELLER Imaging with Auto-calibration
Mengye Lyu1,2, Yilong Liu1,2, Victor B. Xie1,2, ErPeng Dai3, Hua Guo3, and Ed X. Wu1,2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, HKSAR, China, 2Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, HKSAR, China, 3Center for Biomedical Imaging Research, Tsinghua University, Beijing, Beijing, China

PROPELLER MRI is widely used nowadays for motion correction. One major drawback of PROPELLER MRI is the long scan time. Previous studies have investigated in-plane acceleration (SENSE and GRAPPA) in PROPELLER1,5. However, multi-band (MB) simultaneous multi-slice acquisition, without SNR penalty proportional to square root of acceleration ratio, can be a more suitable solution for accelerating PROPELLER. In addition, MB acquisition combining PINS RF pulses2 can reduce RF pulse power deposition, which is particularly useful for alleviating the SAR issue in FSE-PROPELLER at high field. A considerably low g-factor is possible in MB PROPELLER because its rotating phase encoding directions can consequently lead to a well-conditioned unwrapping problem. Another advantage of MB PROPELLER is that 3D coil sensitivity maps (CSMs) can be directly estimated from the oversampled k-space center, without acquiring additional calibration data.

2412.   Dynamic compressed sensing for multiband MRI
Huisu Yoon1, Dong-wook Lee1, Juyoung Lee1, Seung Hong Choi2, Sung-Hong Park1, and Jong Chul Ye1
1Dept. of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Daejeon, Korea, 2Dept. of Radiology, Seoul National University College of Medicine, Seoul, Korea

The applications of dynamic compressed sensing MRI include cardiac imaging, fMRI, angiography, and perfusion imaging. Recently, by exploiting the diversities in coil sensitivity maps across the z-slice, simultaneous multislice imaging (SMS) or multi-band imaging (MB) have been extensively investigated for accelerated acquisition in brain imaging studies. By synergistically combining the two approaches, we propose a dynamic compressed sensing multi-band MR imaging technique for further acceleration in 3-D + t MR acquisition.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2413.   Iterative GRAPPA using Wiener filter
Wan Kim1 and Yihang Zhou1
1The State University of New York at Buffalo, Buffalo, NY, United States

We present a new iterative method using Wiener filter. In contrast to the conventional GRAPPA where only the auto calibration signals (ACS) are used to find the convolution weights, our proposed method iteratively updates the convolution weights using both the acquired and reconstructed data from previous iterations in the entire k-space. To avoid error propagation, the method applies adaptive Wiener filter on the reconstructed data. Experimental results demonstrate that even with a smaller number of ACS lines the proposed method improves the SNR when compared to GRAPPA.

2414.   Single-Slab 3D TSE with CAIPIRINHA Acquisition Mode
Zhang Qiong1, Sun Zhi guo1, and Liu Wei1
1Siemens, ShenZhen, GuangDong, China

The CAIPIRINHA (controlled aliasing in parallel imaging results in higher acceleration) technique has been successfully applied to 3D parallel imaging [1]. By shifting the phase encoding strategy, CAIPIRINHA can provide an optimal phase encoding pattern with minimum g-factor, which leads to higher SNR in comparison to the traditional GRAPPA. In this work, we demonstrate the feasibility of using CAIPIRIHNA technique for potential scan time reduction in single-slab 3D TSE (SPACE) imaging.

2415.   Fast G-factor Estimation in Multi-band Acquisition Based on Sum of Inverse Distance Model
Mengye Lyu1,2, Victor B. Xie1,2, Patrick P. Gao1,2, Yilong Liu1,2, and Ed X. Wu1,2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, Hong Kong, China, 2Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, Hong Kong, China

Inter-slice shift is one of the most important factors for reducing g-factor in multi-band (MB) simultaneous multi-slice acquisition. Previous study1 has shown that the optimal distance of slice shift can deviate away from intuitive choices such as FOV/Nslice However, optimizing shift pattern is time-consuming because iterative algorithms have to be used. In this study, we propose a fast g-factor estimation model that can approximately estimate g-factor versus slice shift distance with closed form formula, with input of slice number and one parameter quantifying the coil sensitivity in slice direction.

2416.   Dual Asymmetric Echo Steady State Imaging with CAIPIRINHA Acquisition Mode
Zhang Qiong1 and Sun Zhi guo1
1Siemens, Shen Zhen, Guang Dong, China

The Caipirinha concept has been successfully transferred in 3D parallel imaging [1]. By shifting the phase encoding strategy, CAIPIRINHA can provide the optimal phase encoding pattern with lowest g-factor; therefore gain higher SNR comparing with traditional GRRAPA technology. In this work, with specific tricks, we explorer the potential speed benefits of Caipirinha applying on 3D variable flip angle Tse.

2417.   Automatic Coil Compression for Parallel MRI based on Noise Variance Estimation
Allan Raventos1, Tao Zhang1, and John M. Pauly1
1Electrical Engineering, Stanford University, Stanford, California, United States

Coil compression methods combine parallel MRI data from large coil arrays into few virtual coils, and therefore significantly speed up the reconstruction. Coil compression is usually achieved by singular value decomposition, where the number of virtual coils can be determined by thresholding the singular values. However, the thresholds have to be manually tuned for different datasets or coil geometries. Here, a new approach based on noise variance estimation is proposed to automatically select the number of virtual coils. The proposed method is validated on datasets from different coil geometries.

2418.   Parallel MRI Reconstruction by Direct Convex Optimization
Cishen Zhang1 and Ifat-Al Baqee1
1Swinburne University of Technology, Hawthorn, Victoria, Australia

The proposed direct convex optimization approach to parallel magnetic resonance imaging (pMRI) is to provide a computational algorithm for efficient processing of undersampled k-space data and accurate reconstruction of magnetic resonance images. It is based on an analysis that the magnitude image to be solved is contained in a convex hull in the solution space of the image function and the sensitivity encoded image functions. This analysis enables a novel formulation of the pMRI reconstruction problem into direct convex optimization.

2419.   Effects of Motion on Coupling of Coil Elements and Parallel Imaging Reconstruction at 3T and 7T
Qiyuan Tian1, Enhao Gong1, Christoph W.U. Leuze2, John Pauly1, and Jennifer McNab2
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Radiology, Stanford University, Stanford, CA, United States

We studied how subject motion between the acquisition of reference data and under-sampled images can affect the quality of parallel imaging reconstruction.

2420.   Investigation of GRAPPA g-factor dependence on calibration scan phase errors and SNR
S. L. Talagala1, J. E. Sarlls1, and S. J. Inati2
1NMRF/NINDS, National Institutes of Health, Bethesda, MD, United States, 2FMRIF/NIMH, National Institutes of Health, Bethesda, MD, United States

Recent work indicates that the temporal SNR of GRAPPA EPI data can be significantly compromised when using an EPI based GRAPPA calibration scan and that a FLASH based calibration scan can be used to correct this problem. In this work, we verify this observation with simulated data and show that phase inconsistencies in the calibration scan can lead to high g-factor and hence, lower temporal SNR in the GRAPPA EPI data. The simulations also show that the detrimental effect of calibration scan phase error is more prominent at higher SNR.

2421.   Parallel magnetic resonance imaging via dictionary learning
Shanshan Wang1,2, Xi Peng1, Jianbo Liu1, Yuanyuan Liu1, Pei Dong2, and Dong Liang1
1Paul C. Lauterbur Research Centre for Biomedical Imaging, Chinese Academy of Sciences, Shenzhen, GuangDong, China, 2School of Information Technologies, University of Sydney, Sydney, New South Wales, Australia

This work proposes a dictionary learning (DL) based sensitivity encoding (SENSE) approach to accurately reconstruct parallel MR images. Specifically, we regularizes the targeted image with sparse representation over an adaptive learned dictionary and formulates the reconstruction as an L2-DL minimization problem. A "divide and conquer" strategy is used to solve the proposed formulation by addressing two subproblems i.e. dictionary learning and image updating. Meanwhile, k-space data is updated as well to add more fine details back. Experimental results show that the proposed method improves the reconstruction accuracy in terms of detail preserving and outperforms the state-of-the-art SparseSENSE based approach.

2422.   Smallest Singular Value: a metric for assessing k-space sampling patterns
Andrew T Curtis1 and Christopher K Anand1
1Computing and Software, McMaster University, Hamilton, Ontario, Canada

A new metric for assessing k-space sampling patterns is presented, which analyzes the smallest singular values (SSV) of the image reconstruction linear operator. The SSV is described along with an efficient means of calculation. It is compared to the gold-standard g-factor, and ranks candidate sampling patterns very similarly. SSV can assess patterns in seconds to minutes, allowing for several interesting applications. We describe one application: assessing random sampling distributions for incoherent aliasing – statistics on uniform and poisson-disk sampling patterns are easily computed over thousands of random patterns, and interesting trends arise!

2423.   STEP: Self-supporting Tailored k-space Estimation for Parallel imaging reconstruction
Zechen Zhou1, Jinnan Wang2,3, Niranjan Balu3, Rui Li1, and Chun Yuan1,3
1Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, 2Philips Research North America, Briarcliff Manor, NY, United States, 3Vascular Imaging Lab, Department of Radiology, University of Washington, Seattle, WA, United States

Parallel Imaging (PI) has been widely used for MR imaging acceleration in clinical applications. However, current subspace based PI methods may not provide accurate reconstruction when it comes to spatially variant correlations due to the varying signal-to-noise characteristics. In this work, we developed a Self-supporting Tailored k-space Estimation for Parallel imaging reconstruction (STEP) technique to further improve the subspace PI reconstruction and the proposed algorithm has demonstrated its performance of reduced noise amplification, less aliasing artifacts and better structure preservation when compared to the existing PI algorithms.

2424.   Highly Accelerated 3D Parallel Imaging with Transitional Auto-calibration (3D-PITA)
Ren He1, Jingyuan Lyu1, and Leslie Ying2
1Department of Electrical Engineering, University at Buffalo, Buffalo, NY, United States, 2Department of Electrical Engineering, Department of Biomedical Engineering, University at Buffalo, Buffalo, NY, United States

A novel 3D-PITA method is proposed for volumetric auto-calibrated parallel imaging. The method introduces a transition region between the ACS region and the highly reduced outer region [3], where the sampling pattern is specially designed to have a lower reduction factor than the outer region. We then perform a two-step calibration/reconstruction, one step with nonlinear GRAPPA and the other with GRAPPA, to obtain the final full k-space data. Experimental results demonstrate the proposed method is able to achieve high reconstruction quality at reduction factors higher than 5 and is superior to the conventional 3D GRAPPA.

2425.   Generalized Direct Virtual Coil (DVC) with SPIRiT kernel for arbitrary sampling pattern
Yuxin Hu1, Tao Zhang2, Kui Ying3, and John M. Pauly2
1Biomedical Engineering, Tsinghua University, Beijing, Beijing, China, 2Electrical Engineering, Stanford University, CA, United States, 3Engineering Physics, Tsinghua University, China

This work generalized direct virtual coil (DVC) using SPIRiT kernel and generalized DVC can be used for arbitrary sampling pattern. In the generalized DVC, SPIRiT kernel and coil combination kernel are combined. Sensitivity map could be also estimated from coil combination kernel. Virtual coil data can be got through convolution between the combined kernel and the under sampled kspace data from all source coils. The results of the generalized DVC are nearly the same as SPIRiT and ESPIRiT and are better than those of DVC.

2426.   Considerations for Parallel Imaging when using High Permittivity Pads in the Thighs at 3 T
Wyger Brink1, Maarten J Versluis1,2, Johannes M Peeters2, Peter Börnert1,2, and Andrew Webb1
1Radiology, Leiden University Medical Center, Leiden, Netherlands, 2Philips Healthcare, Best, Netherlands

The use of dielectric pads substantially improves transmit homogeneity in the thighs. However, it compromises the receive homogeneity of the body coil. If uncorrected, this can degrade image quality when using parallel imaging techniques which rely on body coil information for calibration purposes. A correction procedure using prior knowledge of the body coil reception profile confirms this effect and restores image uniformity.

2427.   Anatomically constrained magnetic resonance inverse imaging for human brain
Kevin Wen-Kai Tsai1,2 and Fa-Hsuan Lin3
1Department of Biomedical Engineering and Computational Science, Aalto University School of Science, Espoo, Finland, 2Brain Research Unit (BRU), Low Temperature Laboratory, Aalto University School of Science, Espoo, Finland, 3Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan

The under-determined inverse problem solved in InI coursed the source localization uncertainty. We proposed an anatomically constrained InI to mitigate this problem by using the high spatial resolution anatomic image as the prior information in reconstruction. Without and with the anatomical constrain in reconstruction, the spatial resolution was improved from 1.9 to 1.2 pixels in the simulation, and also has a better source localization in simulated activation at the thalamus. We conclude that anatomically constrained InI provide the better source localization accuracy than InI.

2428.   Sensitivity improvement under parallel detection in CW-EPR imaging
Ayano Enomoto1 and Hiroshi Hirata1
1Division of Bioengineering and Bioinformatics, Hokkaido University, Sapporo, Hokkaido, Japan

The purpose of this study was to improve the signal-to-noise ratio (SNR) in the parallel EPR detection scheme using multiple channels and to demonstrate the feasibility of in vivo EPR imaging with parallel EPR detection. This improvement in sensitivity leads to a decrease in the image acquisition time in three-dimensional EPR imaging. EPR imaging of 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (3-CP) in a subject mouse was demonstrated with a surface coil array and a parallel detection scheme. In addition to in vivo mouse imaging, tests were also performed with phantoms filled with nitroxyl radical solutions.

2429.   COMPASS – Guiding Reconstruction with Parallel MRI Signal Structure
Yudong Zhu1
1Zhu Consulting, Scarsdale, NY, United States

In this work we show that one can directly identify a parallel MRI signal structure based on imaging physics, elucidate relevant rank/dimensionality with physical parameters, practice reconstruction by finding spectra/images that conform to both the signal structure and acquired spectra samples, and improve SNR by emphasizing conformity to the signal structure.

2430.   AC-LORAKS: Autocalibrated Low-Rank Modeling of Local k-Space Neighborhoods
Justin P. Haldar1
1Electrical Engineering, University of Southern California, Los Angeles, CA, United States

Low-rank modeling of local k-space neighborhoods (LORAKS) is a recent framework for constrained MRI. While LORAKS is powerful, flexible, and enables the simultaneous use of support, phase, and parallel imaging constraints, previous implementations depended on the use of time-consuming low-rank matrix completion algorithms. In this work, we show that fast LORAKS reconstructions are possible if the sampling scheme contains an autocalibration region. Results are shown with real data to demonstrate the advantages of the proposed approach relative to previous LORAKS methods. The approach can also be used as a powerful alternative to autocalibrated parallel imaging methods like SPIRiT and PRUNO.

2431.   KerNL: Parallel imaging reconstruction using Kernel-based NonLinear method
Jingyuan Lyu1, Yihang Zhou1, Ukash Nakarmi1, Chao Shi1, and Leslie Ying1,2
1Department of Electrical Engineering, State University of New York at Buffalo, Buffalo, NY, United States, 2Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, NY, United States

The linear model cannot describe the relationship between the missing and acquired k-space data in GRAPPA. Here we propose a more general nonlinear framework for auto-calibrated parallel imaging. In this framework, kernel tricks are employed to represent the general nonlinear relationship between acquired and unacquired k-space data without increasing the computational complexity. Identification of the nonlinear relationship is still performed by solving linear equations. We name the proposed method Kernel-based NonLinear (KerNL) method. Experimental results demonstrate that the proposed method is able to improve both image quality and computation efficiency at high reduction factors, compared with GRAPPA and nonlinear GRAPPA.

2432.   A Theory for Sampling in k-Space - Parallel Imaging as Approximation in a Reproducing Kernel Hilbert Space
Vivek Athalye1, Michael Lustig1, and Martin Uecker1
1Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, United States

We show that parallel imaging can be formulated as an approximation of vector-valued functions in a Reproducing Kernel Hilbert Space (RKHS). This formulation provides new theoretical insights into sampling and reconstruction in k-space. In particular, we derive local bounds for the approximation error and noise amplification maps in k-space. These new metrics complement the existing g-factor maps and explain the effect of different sampling schemes on reconstruction quality. This is demonstrated for several sampling patterns using numerical experiments.

2433.   Clinical Feasibility of Accelerated TOF MR Angiography with Sparse Undersampling and Iterative Reconstruction: Comparison with Conventional Parallel Imaging
Takayuki YAMAMOTO1, Koji FUJIMOTO1, Tomohisa OKADA1, Yasutaka FUSHIMI1, Akira YAMAMOTO1, Aurelien F. STALDER2, Yutaka NATSUAKI3, Michaela SCHMIDT2, and Kaori TOGASHI1
1Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, Japan, 2Siemens Healthcare, Erlangen, Germany, 3Siemens Medical Solutions USA, Inc, Pennsylvania, United States

Due to the relatively lower CNR, application of sparse MRI techniques to non-contrast enhanced Time-of-Flight (TOF) MRA of the brain is still challenging and hence previous reports are limited. In this study, the sparse MRI technique to TOF-MRA (sparse TOF) and conventional parallel imaging (GRAPPA) was performed for 9 healthy volunteers at 3.0T MRI scanner. Two radiologists made a subjective assessment of overall impression and the visualization of distal segments of the arteries. The result indicates that sparse TOF-MRA achieved higher acceleration while maintaining visual quality and can thus be used in a clinical setting.

2434.   Ultra short echotime MRI to locate foreign objects: Initial phantom results
Karl-Heinz Herrmann1, Anusch Mheryan2, Martin Stenzel2, Hans-Joachim Mentzel2, Ulf Teichgräber2, and Jürgen R Reichenbach1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany, 2Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany

Especially in pediatric radiology locating foreign objects with CT is not desirable due to ionising radiation. A radial 3D ultra short echotime (UTE) sequence with 0.66mm isotropic resolution, both with and without the use of a long T2 tissue suppression pulse, was evaluated for wooden and glass foreign objects in a phantom (pig feet). Especially the UTE sequence with long T2 suppression seems ideal as a search modality for wood due to the excellent contrast while CT images provide very poor contrast for biological material. In the case of glass, CT image quality is cleary superior, but the UTE sequence should still be able to provide the exact location of a glass splinter in most cases.

2435.   SNR-Efficient Anisotropic 3D Ultra-Short Echo Time Sequence for Sodium MRI with Retrospective Gating
Simon Konstandin1 and Matthias Günther1,2
1MR-Imaging and Spectroscopy, Faculty 01 (Physics/Electrical Engineering), University of Bremen, Bremen, Germany, 2Fraunhofer MEVIS, Bremen, Germany

Most sodium MR studies are performed using 3D ultra-short echo time (UTE) sequences with isotropic resolution. For some applications, however, anisotropic resolution is preferred to reduce partial-volume effects that hamper sodium quantification. No analytical formula could be found for the azimuth angle to acquire k-space uniformly on an ellipsoidal surface using the golden ratio (GR). In this work, a 3D acquisition scheme is presented to achieve high SNR efficiency for UTE imaging with anisotropic resolution and retrospective gating using the GR. This SNR gain can be invested in higher resolutions and/or measurement time, which is important for sodium MRI.

2436.   T2-selective excitation with UTE imaging for bone imaging
Ethan M Johnson1, Urvi Vyas2, Kim Butts Pauly2, and John M Pauly1
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Radiology, Stanford University, Stanford, CA, United States

This work describes a method for creating short-T2-selectivity in excitation without preparatory pulses and demonstrates its use with UTE imaging. The method described is also appropriate for controlling short-T2 contrast in ZTE imaging. Bone structure imaged using a multi-echo UTE sequence with multiple T2-selective excitation pulses to highlight short-T2 components. The structures represented in MRI are verified by comparison to CT images of the same subjects.

2437.   Anisotropic Field-of-View Support for Golden Angle Radial Imaging
Ziyue Wu1 and Krishna S. Nayak1
1University of Southern California, Los Angeles, CA, United States

Radial sampling techniques are often used in dynamic MRI because they are robust to flow and motion, support short echo times, and have a diffuse aliasing pattern. One drawback is that standard implementations do not support anisotropic field-of-view (FOV). Larson et al. has provided a simple and intuitive scheme for supporting anisotropic FOV in static radial imaging. In this work,We extend that approach and demonstrate a simple solution to enable 2D anisotropic FOV with GA radial imaging, which can significantly reduce imaging times in many scenarios (abdomen, spine, etc.) where the object dimensions are anisotropic, while still allowing arbitrary temporal window reconstruction.

2438.   Gradient-modulated PETRA
Naoharu Kobayashi1, Luning Wang1, and Michael Garwood1
1Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States

We introduce a novel PETRA technique with gradient modulation (GM) which enables higher readout bandwidth while keeping the missing center k-space region small. GM enables use of higher readout bandwidth while keeping excitation bandwidth relatively low, which reduces off-resonance blurring in images. The proposed sequence was evaluated by comparing PETRA techniques with and without GM for an equine knee sample in a human 7T scanner. GM-PETRA showed significantly less off-resonance blurring compared to the conventional PETRA technique under the same excitation bandwidth condition. GM can improve the PETRA image quality without any special hardware modification of clinical scanners.

2439.   Segmented Golden Ratio Radial Reordering for Dynamic Cardiac MRI with Variable Temporal Resolution
Fei Han1, Ziwu Zhou1, Stanislas Rapacchi1, Paul Finn1, and Peng Hu1
1Radiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States

Golden angle radial reordering (GA) could provide a near-uniform k-space within a single reconstruction window with arbitrary position and duration. However, when applied with ECG-gated segmented acquisition where a single reconstruction window breaks into several temporally isolated k-space data, the k-space coverage of GA may not be as uniform as GA without ECG gating. Therefore, we sought to investigate the image artifacts caused by applying GA to ECG-gated cardiac imaging and propose a segmented GA method to address this issue.

2440.   3D Through Time GRAPPA For Dynamic Distributed Spirals
Dallas C Turley1 and Jim Pipe1
1Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, United States

This work presents an implementation of through-time GRAPPA in the Distributed Spirals trajectory to improve temporal resolution of 3D dynamic acquisitions.

2441.   CODEC: Covariance-driven Parallel Imaging for NonCartesian Sampling Trajectories
James G Pipe1
1Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, United States

This work presents a new parallel imaging method. It is a k-space convolution method that is quite independent of the sampling geometry, and does not require training, and therefore is quite suitable for nonCartesian sampling. The method is described, and 2D and 3D examples are shown.

2442.   Rapid 3D Spoiled Steady-State Imaging with Yarn-Ball Acquisition
Robert W. Stobbe1 and Christian Beaulieu1
1University of Alberta, Edmonton, Alberta, Canada

A novel multi-shot 'Yarn-Ball' technique is presented which facilitates efficient 3D k-space sampling through large loops with low acceleration. The differential equations underpinning this technique are described, and the number of trajectories required to fully sampling 3D k-space are compared to standard gradient echo. Unlike gradient echo, trajectory requirements can be dramatically reduced by >100x with readout duration increase. In the context of 3D spoiled steady-state imaging, Yarn-Ball allows the generation of much higher resolution images than is possible with standard gradient echo for the same TR and scan duration.

2443.   Density-Adapted Spiral MRI sequence for 23Na imaging
Maria Engel1, Nadia Benkhedah1, and Armin M. Nagel1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

This study developed a 3-D density adapted spiral sequence, which handles the high dependency on the slewrate limit of the MRI scanners gradient system. It was found to attain a radial fraction of up to 0.21, leading to a time saving of almost 80% compared to commonly used radial projection sequences. 23Na-MRI of head was conducted using a 7-Tesla whole body MR system.

2444.   A Spiral Spin-Echo Sequence for Fast T2-Weighted Imaging with Improved Contrast
Zhiqiang Li1, Dinghui Wang1, John P Karis2, and James G Pipe1
1Imaging Research, Barrow Neurological Institute, Phoenix, AZ, United States, 2Neuroradiology, Barrow Neurological Institute, Phoenix, AZ, United States

T2-weighted TSE is a routine clinical tool for neuroimaging. TSE generates slightly different contrast than conventional SE. TSE can also incorporate the mDixon technique to provide fat/water imaging, but at the cost of prolonged scan time. In this project, we propose a spiral SE sequence for enhanced T2 contrast and fast scan speed. Preliminary results showed increased T2 contrast with spiral SE in tissues with increased ion deposition. It’s also demonstrated that the SNR of spiral SE is close to TSE even its scan time is shorter. Therefore, spiral SE is a potential alternative to TSE for T2-weighted imaging.

2445.   Analytic form 3D radial sampling strategy for maintaing the uniformity of k-space coverage with increasing interleaves
Jinil Park1, Tae-Hoon Shin2, and Jang-Yeon Park1
1Biomedical Engineering, IBS Center for Neuroscience Imaging Research, Sungkyunkwan University, Suwon, Gyungki-do, Korea, 2Diagnostic Radiology and Nuclear Medicine, University of Maryland, Baltimore, Maryland, United States

In this study, we propose a modified version of Wong's method that is able to almost maintain the uniformity of k-space coverage even in the event that imax increases, providing an analytic form for the coordinates of all views in terms of the readout gradient strengths in the x-, y-, and z- axes. Our suggestion was validated by simulation and phantom experiments.

2446.   In-vivo brain fast Rosette Spectroscopic Imaging (RSI) with reduced gradient demands/improved patient comfort and a processing pipeline with automated LCModel quantification, for all acquired voxels
Claudiu Schirda1, Tiejun Zhao2, Ovidiu Andronesi3, James Mountz1, Fernando Boada1, and Hoby Hetherington1
1Radiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States, 2Siemens Medical Solutions, Pittsburgh, PA, United States, 3Radiology, Massachusetts General Hospital, Boston, MA, United States

The rosette trajectory design flexibility is used to decrease the demands on scanner gradient system for the Rosette Spectroscopic Imaging (RSI) sequence. The reduced gradient readout strength and slew rate results (in addition to decreased Eddy currents and decreased frequency drift) in decreased acoustic noise and decreased scanner vibrations, which improves patient comfort. A 2D RSI acquisition with in-plane resolution of 8mm and a 20x20x12 3D RSI acquisition with nominal isotropic resolution of 8mm and effective voxel size of 0.55cc are demonstrated in-vivo with slew rate of 45mT/m/ms and gradient of 5.8mT/m in 32 sec and 5-10 mins, respectively.

Single-shot spiral imaging using the gradient impulse response for trajectory prediction
Signe Johanna Vannesjo1, Nadine N Graedel2, Lars Kasper1, Simon Gross1, Christoph Barmet1,3, and Klaas P Pruessmann1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, 2FMRIB Centre, University of Oxford, Oxford, United Kingdom, 3Skope Magnetic Resonance Technologies, Zurich, Switzerland

Spiral imaging theoretically yields more time-efficient k-space coverage and increased robustness against flow and motion compared to Cartesian acquisitions. In practice however, the use of spiral acquisitions has been hampered by gradient system limitations causing deviations to the sampling trajectories. It has recently been proposed to perform image reconstruction based on trajectories predicted by a linear time-invariant model of the gradient system. Here, the method is shown to yield high-quality reconstructions of single-shot spiral images. We furthermore show high reproducibility of the gradient system characterization over years. The method holds promise to yield spiral imaging feasible on standard MR systems.

2448.   Dynamic Volumetric MRI using Golden-Angle Variable Density Spiral Acquisition with Sparse Parallel Imaging Reconstruction
Lyu Li1, Xiaodong Ma1, Pascal Spincemaille2, Yi Wang2,3, Huijun Chen1, and Hua Guo1
1Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, 2Radiology, Weill Cornell Medical College, New York, United States, 3Biomedical Engineering, Cornell University, New York, United States

High resolution dynamic volumetric MRI is crucial for the accurate clinical diagnosis. Several studies have proposed some data acquisition and image reconstruction strategies such as TRACER and GRASP. The reconstruction of TRACER is sensitive to motion so breath hold is needed. GRASP is very motion insensitive, but its data acquisition efficiency is not high enough. In this study, we aim to investigate a method combining golden angle variable density spiral data acquisition with sparse and parallel imaging reconstruction, which could achieve high spatial and temporal resolution when free breathing.

2449.   L1-ESPIRiT Reconstruction for Accelerating 3D UTE and Denoising
Wenwen Jiang1, Frank Ong2, Roland Henry3, Michael Lustig2, and Peder E.Z. Larson3
1Bioengineering, UC Berkeley/UCSF, Berkeley, CA - California, United States, 2EECS, UC Berkeley, Berkeley, California, United States, 3Radiology and Biomedical Imaging, UCSF, San Francisco, CA - California, United States

Ultrashort echo time (UTE) imaging has shown promise for imaging tissues with ultrashort T2 values. UTE with a 3D radial trajectory requires π times the number of phase-encodings as the Cartesian counterpart, requiring long scan times. Practically, ~π times undersampling can be used for acceleration without noticeable streak aliasing artifacts with gridding reconstruction. However, the undersampling-induced aliasing results in noise-like artifacts. We propose using L1-ESPIRiT on 3D UTE for effectively removing streak and noise-like undersampling artifacts, and allowing for high acceleration factors with robustness. The in vivo applications for brain imaging shows the benefits of L1-ESPIRiT for 3D UTE.

2450.   Proton-constrained CMRO2 Quantification with direct 17O-MRI at 3 Tesla
Dmitry Kurzhunov1, Robert Borowiak1,2, Philipp Wagner1, Marco Reisert1, and Michael Bock1
1Department of Radiology · Medical Physics, University Medical Center Freiburg, Freiburg, Baden-Württemberg, Germany, 2German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Baden-Württemberg, Germany

In this work iterative proton-constrained reconstruction of 17O MR data set using an anisotropic non-homogeneous diffusion operator is proposed. It was tested on a 17O brain phantom and on a data set obtained from a dynamic 17O MRI experiment. 17O images show a higher SNR and superior quality compared to Kaiser-Bessel re-gridding method. Localized CMRO2 quantification with 1H constrained in a human frontal lobe and in a brain phantom show most precise CMRO2 values in GM and WM. For GM it is in good agreement with literature 15O-PET data.

2451.   Comparison of Pre-reconstruction Interpolation Methods for Rapid Compressed Sensing Reconstruction of Non-Cartesian k-Space
KC Erb1, Ganesh Adluru1, Srikant Kamesh Iyer1, Devavrat Likhite1, John A Roberts1, and Edward DiBella1
1UCAIR, University of Utah, Salt Lake City, Utah, United States

Pre-reconstruction cartesian-interpolation (gridding) algorithms are used to interpolate non-cartesian data onto a cartesian grid for simple cartesian reconstruction. In this work, we compare 3 such interpolation methods to the Non-Uniform Fast Fourier Transform (NUFFT). Two of the methods are simple single-coil interpolators (nearest neighbor and 3-point interpolation) and the other is a newer multi-coil method called GRAPPA Operator Regridding (GROG). We demonstrate that GROG is able to produce images which are quantitatively more similar to NUFFT reconstructed images than the other single-coil methods. We also demonstrate that GROG continues to outperform the other methods, even on highly undersampled datasets.

2452.   Density compensation for iterative reconstruction from under-sampled radial data
Boris Mailhe1, Qiu Wang1, Robert Grimm2, Marcel Dominik Nickel2, Kai Tobias Block3, Hersh Chandarana3, and Mariappan S. Nadar1
1Imaging and Computer Vision, Siemens Corporation, Corporate Technology, Princeton, NJ, United States, 2MR Application & Workflow Development, Siemens Healthcare, Erlangen, Germany, 3Department of Radiology, New York University School of Medicine, New York, NY, United States

Density compensation is a mandatory step for direct reconstruction of radial MRI data. We interpret density compensation as a left-hand-side preconditioner of the measurement operator. We propose an alternative formulation as a right-hand-side preconditioner compatible with regularized iterative reconstruction. In the case of under-sampled radial trajectories, we show that a ramp filter overemphasizes high frequencies. Instead, we calibrate the preconditioner offline. We show that preconditioning accelerates the reconstruction and improves the sharpness of the reconstructed images.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2453.   CAIPIRINHA acceleration enables rapid high-spatial-resolution isotropic 3D SPACE of the knee: Comparison with conventional SPACE and 2D TSE
Esther Raithel1, Gaurav Thawait2, Shivani Ahlawat2, Shadpour Demehri2, Zhang Qiong3, and Jan Fritz2
1Siemens AG, Healthcare Sector, Erlangen, Bavaria, Germany, 2Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Maryland, United States, 3Siemens AG, Guang Dong, China

While 2D TSE MRI is standard in musculoskeletal MRI, similar performance was shown for 3D TSE-type sequences (SPACE) before; however, long acquisition times may limit its clinical use. In contrast to one-dimensional acceleration, a 2x2 CAIPIRINHA pattern can yield substantial acceleration of 3D data acquisition. We demonstrate the implementation of a 4-fold CAIPIRINHA acceleration pattern into a 3D SPACE sequence with a resultant 50-60% decrease of the acquisition time when compared to a standard 2-fold accelerated SPACE. A 5-min CAIPIRINHA SPACE sequence can produce near identical image quality in the knee as 11-min SPACE and 10-min three plane 2D TSE sequences.

Rapid Fast Field-Cycling MRI using Keyhole Imaging
Peter James Ross1 and David J. Lurie1
1Aberdeen Biomedical Imaging Centre, University of Aberdeen, Aberdeen, Aberdeen City, United Kingdom

In this work we describe a new method of field-cycling relaxometric imaging based on the view-sharing technique known as keyhole imaging. We have employed this technique to generate images containing a new form of endogenous contrast based on the variation of R1 with the external magnetic field. Relaxometric imaging results are presented from a phantom study and a human volunteer in order to demonstrate the accuracy and practicality of the method.

2455.   Robust and Automatic Polarity Determination for Phase-Sensitive Inversion Recovery (PSIR) Imaging
Deqing Chen1 and Weiguo Zhang1
1Shanghai United Imaging Healthcare Co. Ltd., Shanghai, Shanghai, China

Ambiguity in global polarity can lead to wrong final image contrasts in PSIR. Current methods for determining polarity either rely on a priori assumptions or require reference data that add significant scan time, making them susceptible to errors under diverse clinical circumstances. Here we report an efficient, reliable and fully automatic method for determining the global polarity for PSIR imaging. The method makes no assumptions and requires practically no extra time.

2456.   An integrated approach of interactive land-marking and auto coil detection
Jia Guo1, Yongchuan Lai1, Xiaocheng Wei1, Nan Cao1, and Bing Wu1
1GE Healthcare, Beijing, China

This method makes landmark very simple, and provides coverage knowledge of floating coil. The overall scan was just over 10 seconds, and all the information were gathered and processed during the move-in of table, no extra time was added to the scan process and when the operator returns to the operator console, the graphical information is already available on the screen for placing localizer. In this way, improper coverage of localizer scan, unnecessary body contacts with patients and blind knowledge of the location of the coil are all avoided. This method was also silent in nature that ensures patient¡¯s comfort.

2457.   Acquisition and Reconstruction Effects on Image Quality in Variable-Density Sparse MRI
Dimitris Mitsouras1, Onur Afacan2, Robert V Mulkern3, and Dana H Brooks4
1Radiology, BWH/Harvard Medical School, Boston, MA, United States, 2Children's Hospital Boston, MA, United States, 3Childrens' Hospital Boston, MA, United States,4Northeastern University, Boston, MA, United States

We systematically compared undersampled variable density sampling schemes in conjunction with linear and compressed sensing (CS) reconstruction methods. Simulated and experimental results showed trajectory choice had minimal effect on carefully-defined SNR and RMSE metrics compared to reconstruction method, and that while CS outperformed linear reconstruction, there is tradeoff in terms of noise-driven uncertainty of individual image values that is spatially related to the transform domain chosen. The CS transform domain and reconstruction parameter selection is likely important to avoid uncertainty in clinically-relevant image features; for example, minimum-L1 reconstruction should be avoided when signal hyper-intensities in homogenous hypo-intense backgrounds are relevant.

Optimal Spread Spectrum for Enhanced Multi-Receive Compressed Sensing MRI
Sulaiman A Al Hasani1, Gary F Egan2, and Jingxin Zhang3
1Electrical and Computer Systems Engineering, Monash University, clayton, VIC, Australia, 2Monash Biomedical Imaging, Monash University, VIC, Australia, 3School of Software and Electrical Engineering, Swinburne University of Technology, VIC, Australia

The reconstruction quality of CS is highly dependent on the level of signal (image) sparsity as well as the level of incoherent In conventional MRI, Fourier encoding concentrates the energy of MR signal in the center of k-space, this limits the incoherent sampling and hence hinders the performance of CS reconstruction. In this work, we propose a practical encoding scheme, based on the spread spectrum analysis of Chirp modulated Fourier sensing matrix, to enhance the incoherent sampling of multi-receive MRI. The proposed method outperforms Fourier encoding in preserving image quality at high acceleration factors.

2459.   Image Reconstruction of Under-sampled Signal at Equal Interval using Quadratic Phase Scrambling
Satoshi Ito1, Shungo Yasaka1, and Yoshifumi Yamada1
1Utsunomiya University, Utsunomiya, Tochigi, Japan

Sparse MRI has been introduced to reduce the acquisition time and raw data size by randomly undersampling the k-space data. However, the image quality depends on the randomness or signal trajectory in k-space even if the reduction factor of signal is the same. In other words, the best signal trajectory depends on the object to be imaged, however, it is impossible in general to know the best signal trajectory for unknown image data. In this paper, we propose a novel image reconstruction technique in which undersampled signal at equal interval is adopted in image reconstruction. To reduce the aliasing artifact due to equally-spaced undersampled signal, we used the phase-scrambler in the acquisition.

2460.   Improved Partial Fourier Reconstruction Using Two Reverse Polarity Echoes in a Single GRE Acquisition
Ehsan Hamtaei1,2, Saifeng Liu3, Yongquan Ye2, Dongmei Wu4, and E. Mark Haacke1,2
1MR Innovations Inc., Detroit, MI, United States, 2Radiology, Wayne State University, Detroit, MI, United States, 3MRI Institute of Biomedical Research, Ontario, Canada,4East China Normal University, Shanghai, China

A new approach is proposed for improving the Partial Fourier reconstruction in asymmetrically collected double echo gradient echo data with two reverse polarity echoes. Comparison is made with conventional Partial Fourier reconstruction (POCS). The high resolution phase estimate obtained using the proposed method, helps POCS converge more efficiently.

2461.   Non-linear TRASE
Somaie Salajeghe1, Paul Babyn2, Jonathan C. Sharp3, and Gordon E. Sarty1
1Division of Biomedical Engineering, University of Saskatchewan, Saskatoon, SK, Canada, 2Medical Imaging, University of Saskatchewan, Saskatoon, SK, Canada,3Department of Oncology, University of Alberta, Edmonton, AB, Canada

Transmit array spatial encoding (TRASE) uses spatial RF phase gradients in place of main field gradients to encode image information. When the RF gradients are linear the image may be reconstructed using the Fourier transform. Since linear gradients may be somewhat expensive to achieve, we investigated the possibility of using least squares to reconstruct data from non-linear TRASE. Our results indicate that this is a feasible approach.

2462.   Enhanced FRONSAC Encoding with Compressed Sensing
Haifeng Wang1, R. Todd Constable1, and Gigi Galiana1
1Yale University, New Haven, CT, United States

Nonlinear spatial encoding magnetic (SEM) fields have been studied to reduce the number of echoes needed to reconstruct a high quality image, but optimal schemes are still unknown. Previously, we showed that adding a rotating nonlinear field of modest amplitude, which we call the FRONSAC (Fast ROtary Nonlinear Spatial Acquisition) imaging, greatly improved the reconstructions obtained from highly undersampled conventional linear trajectories. However, since the ultimate goal is to acquire these highly undersampled trajectories in a single short TR, still lower amplitude FRONSAC gradients are desirable. FRONSAC creates undersampling artifacts that are relatively incoherent and well suited to CS reconstruction. Compressed sensing (CS) is a sparsity-promiting convex algorithm to reconstruct images from highly undersampled datasets. In this paper, we present a hybrid, CS-FRONSAC, which combines these two methods. The simulation results illustrate that the proposed method improves incoherence between the sensing and sparse domains, and it ultimately improves image quality compared with results recovered by the Kaczmarz algorithm. The resulting improvement allows us to consider FRONSAC gradients with lower amplitudes and frequencies, lowering hardware demands as well as dB/dt burden.

2463.   Improved Scan Efficiency of 3D Fast Spin Echo with Subspace-Constrained Reconstruction
Jonathan I. Tamir1, Weitian Chen2, Peng Lai2, Martin Uecker1, and Michael Lustig1
1Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, United States, 2Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States

Scan efficiency plays a major role in 3D Fast Spin Echo because of the tradeoff between image blurring and SNR. The number of echo trains during a scan is limited by the TR interval, which is often much longer than the prescribed echo train length (ETL). Here we explore the benefit of using the extra time in the TR to increase the ETL. We show that a model-based, subspace-constrained reconstruction is able to use the additional data to increase SNR. The approach has a fixed SNR cost independent of ETL compared to a reconstruction where the relaxation parameters are known.

2464.   In-vivo High Resolution Imaging of Fine-Scale Anatomical Structures at 3T with Simultaneous Bias/Variance Reduction
Aymeric Stamm1, Onur Afacan2, Benoit Scherrer2, Jolene M Singh1, and Simon K Warfield1
1Computational Radiology Laboratory, Department of Radiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States, 2Boston Children's Hospital, Harvard Medical School, Boston, MA, United States

High resolution imaging has an important role to play in the detection of malformations of cortical development, and can dramatically improve the prospect of a surgical cure in epilepsy, or in the detection of brain lesions. We propose a novel, unified reconstruction strategy that overcomes prior limitations and show that the strategy can be applied to imaging the stria of Gennari in vivo in a reasonable amount of time on a conventional 3T magnet. Our proposed technology enables image reconstruction from inter-session and intra-session k-space data, that overcomes intra-session and inter-session phase variation to enable arbitrarily high SNR imaging.

2465.   rOi-Space: Accelerated imaging of sub-volumes using ROI focused O-Space
Emre Kopanoglu1, Haifeng Wang1, Yuqing Wan1, Dana C. Peters1, Gigi Galiana1, and Robert Todd Constable1
1Diagnostic Radiology, Yale University, New Haven, Connecticut, United States

Nonlinear gradient fields encode spatial information along multiple directions simultaneously. Using a receiver-array, the spatial information along different directions can be recovered. O-Space imaging exploits this idea to perform accelerated data acquisitions. In standard O-Space imaging, the full field-of-view is encoded, which results in acquisition of redundant data when the region-of-interest is a sub-volume. In this study, we propose a novel O-Space implementation that focuses the encoding effort to the region-of-interest. With a typical O-Space acquisition, the acceleration factor may exceed the number of receiver coils whereas the proposed method can further reduce the imaging time by up-to 25%.

2466.   Scan Time Reduction for Non-CPMG 3D FSE Imaging Based on Phase Cycling
Weitian Chen1, Rob Peters2, Suchandrima Banerjee1, Misung Han3, Roland Krug3, Garry Gold4, and Yuval Zur5
1Global Applied Science laboratory, General Electric, Menlo Park, CA - California, United States, 2Global Applied Science laboratory, General Electric, Waukesha, WI, United States, 3Department of Radiology and Biomedical Imaging, UCSF, San Francisco, CA - California, United States, 4Radiology, Stanford University, Palo Alto, CA - California, United States, 5Healthcare Magnetic Resonance, General Electric, Haifa, Israel

Fast spin echo (FSE) imaging plays a central role in clinical MRI. When combined with flip angle modulation, very long echo train can be used without excessive blurring, which makes 3D FSE imaging feasible in clinical setting. FSE requires CPMG condition. However, this condition can be violated in a number of applications due to system imperfection and result in image artifacts. We recently proposed a non-CPMG FSE acquisition based on a phase cycling method. However, this approach doubles scan time. Here we discussed the methods to reduce the scan time of this approach.

2467.   Accelerating MRI by quadratic phase encoding
Lin Chen1, Congbo Cai2, Shuhui Cai1, and Zhong Chen1
1Department of Electronic Science, Xiamen University, Xiamen, Fujian, China, 2Department of Communication Engineering, Xiamen University, Xiamen, Fujian, China

Reducing the number of measurements required by Nyquist sampling theorem is one way to accelerate MRI acquisition at the cost of introducing aliasing artifacts. Various approaches have been proposed to eliminate aliasing artifacts, such as parallel imaging and non-Cartesian sampling. However, the higher hardware requirement of parallel imaging and complicated trajectory design and image reconstruction of non-Cartesian sampling limit their wide applications. In this abstract, we propose an MRI approach based on quadratic phase encoding, which can accelerate acquistion with efficient aliasing artifacts suppresion using a single receiver coil and uniform sampling.

2468.   High-resolution fMRI using Accelerated EPIK for Enhanced Characterisation of Functional Areas at 3T
Seong Dae Yun1 and N. Jon Shah1,2
1Institute of Neuroscience and Medicine, Medical Imaging Physics (INM-4), Forschungszentrum Juelich, Juelich, Germany, 2Faculty of Medicine, Department of Neurology, JARA, RWTH Aachen University, Aachen, Germany

EPIK had been previously validated both at 1.5T and 3T. The method was shown to provide a higher temporal resolution and less image distortions than single-shot EPI whilst maintaining comparable performance for the detection of BOLD-based signals. This work aims to perform high-resolution visual fMRI based on EPIK and evaluate its performance in direct comparison to comparable EPI; each method was accelerated with parallel imaging and partial Fourier techniques for resolution improvement. The obtained results showed that EPIK outperformed single-shot EPI in terms of imaging resolution and capability of identifying relatively small functional regions such as LGN and SC.

Simultaneous Imaging of Myelin and Iron using Ultrashort Echo Time (UTE) MRI
Vipul R Sheth1, Jacopo Annese1, Hongda Shao1, Qun He1, Jody Corey-Bloom2, Graeme M Bydder1, and Jiang Du1
1Radiology, University of California, San Diego, CA, United States, 2Neurosciences, University of California, San Diego, CA, United States

An inversion recovery ultrashort echo time (IR-UTE) MRI pulse sequence is used to detect myelin lesions and iron deposition in multiple sclerosis patients. The mechanism by which the IR-UTE pulse sequence detects myelin and iron deposition is explored.

2470.   Spatial localization of relaxation dispersion by field-cycling with one-dimensional projection
Kerrin J Pine1, Gareth R Davies1, and David J Lurie1
1Aberdeen Biomedical Imaging Centre, University of Aberdeen, Aberdeen, Scotland, United Kingdom

In field-cycling MRI, the normally stable main magnetic field B0 is manipulated during an examination to explore the field strength dependency of relaxation rate. Clinical adoption relies on finding alternatives to T1 dispersion imaging which is associated with lengthy scan times. A pulse sequence is described for rapid measurement of T1dispersion with one-dimensional projection. Results are presented demonstrating the 1D spatial variation of dispersion in a phantom. The sequence could be used to rapidly locate pathology of known dispersion for further inspection by other methods.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2471.   Multivariate asymmetry analysis (MVAA): applications in temporal lobe epilepsy
Diego Cantor-Rivera1, Terry M. Peters2, and Ali R. Khan2
1Biomedical Engineering Graduate Program, Western University, London, ON, Canada, 2Medical Biophysics, Western University, London, ON, Canada

This work presents a novel multivariate asymmetry analysis for investigating focal structural abnormalities. The novel method uses multi-parametric imaging data non-rigidly registered to a symmetric template to estimate asymmetry measures using locally-sampled cumulative distribution functions (Kolmogorov-Smirnov test). We applied it to investigate structural abnormalities in temporal lobe epilepsy using quantitative relaxometry, diffusion tensor imaging, and voxel-based morphometry. Whole brain Mahalanobis distance maps were employed in a support vector machine classification to show that the use of asymmetry significantly improves discrimination between temporal lobe epilepsy patients and healthy controls.

2472.   Polyhedral Phantom Framework with Analytical Fourier Transform with Intensity Gradients
Shuo Han1 and Daniel A. Herzka1
1Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, Maryland, United States

Analytical phantoms with closed form solutions for their Fourier Transforms (FT) enable accurate and arbitrary sampling of k-space. Though most phantoms are limited to simple shapes such as rectangles or ellipsoids, we have recently presented an expression for the 3D FT of a polyhedron of uniform intensity. This work provides the mathematical framework that extends the original polyhedral FT to account for linear gradients in intensity. A computationally efficient implementation is demonstrated.

2473.   A Hybrid Approach to Intensity Normalization of Brain MRI based on Gaussian Mixture Model and Histogram Matching
Xiaofei Sun1, Lin Shi2,3, Yishan Luo1, Winnie CW Chu1, and Defeng Wang1,4
1Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, 2Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, 3Chow Yuk Ho Technology Centre for Innovative Medicine, The Chinese University of Hong Kong, Shatin, NT, Hong Kong,4Department of Biomedical Engineering and Shun Hing Institute of Advanced Engineering, The Chinese University of Hong Kong, Shatin, NT, Hong Kong

Intensity of similar tissues on brain MRIs is often inhomogeneous because of the various acquisitions. It is problematic since the analysis of MR images (registration, segmentation and volumes statistics) may depend on the hypothesis that corresponding anatomical locations have a similar intensity level. In this study, a new hybrid approach based on Gaussian mixture model and histogram matching to normalize for intensity differences on MR images is presented. This method does not require spatial alignment. The effectiveness of intensity normalization is validated on real data, and the results show that intensity normalization significantly improves the accuracy of tissues segmentation results.

2474.   Concentration maps improve detection of gray matter alteration in cerebellum and deep gray matter structures
Guillaume Bonnier1,2, Jean-Philippe Thiran2, Gunnar Krueger1,2, Tobias Kober1,2, Bénédicte Mortamet1,2, Cristina Granziera1,3, and Alexis Roche1,2
1Siemens ACIT – CHUV Radiology, Siemens Healthcare IM BM PI & Department of Radiology CHUV, Lausanne, Vaud, Switzerland, 2LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland, 3Department of Clinical Neurosciences, Laboratoire de recherche en neuroimagerie and Neuroimmunology Unit, Lausanne, Vaud, Switzerland

Gray-matter (GM) segmentation in brain MRI is challenged by the presence of more than one tissue type in a voxel, an effect known as partial volume. This problem is particularly evident in regions such as the lateral part of the central nuclei (CN) or in the cerebellum. In this study, we used GM concentration maps showing good qualitative results compared with histological data to improve GM segmentation and quantitative analysis in the CN and cerebellum. Our results showed that GM analysis using concentration maps has higher sensitivity than binary masks to detect T1 changes.

2475.   Iterative Residual Based Deconvolution Partial Volume Correction for Brain PET- MRI
Chenguang Peng1, Huayu Zhang1, Jinchao Wu1, Xingfeng Shao1,2, Yingmao Chen3, Quanzheng Li4, Georges El Fakhr4, and Kui Ying1
1Key Laboratory of Particle and Radiation Imaging, Ministry of Education, Department of Engineering, Beijing, China, 2Department of Bioengineering, UCLA, California, United States, 3Department of Nuclear Medicine, The general hospital of Chinese People's Liberation, Beijing, China, Beijing, China, 4Department of Radiology, Division of Nuclear Medicine and Molecular Imaging, Harvard Medical School, Boston, United States

With the implement of PET-MRI, simultaneously MRI and PET image acquisition becomes real. Researchers have been wondering how to use high resolution MRI image to improve the PET image quality. In this work, we proposed a iterative residual based deconvolution method using MRI information for PET partial volume effect correction which is one of the major causes for PET low spatial resolution. Proposed method perform well in lesion contrast enhancement without introducing additional noise to image. Both phantom simulation and in-vivo result is shown in this work.

2476.   Processing Induced Spatial Correlations Are Quantified With A Temporal Frequency Representation in Complex-Valued fMRI
Mary C. Kociuba1 and Daniel B. Rowe1,2
1Department of Mathematics, Statistics, and Computer Science, Marquette University, Milwaukee, Wisconsin, United States, 2Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States

To remove variability, from image acquisition artifacts and unwanted physiological sources, inherent within an acquired functional MRI (fMRI) signal, the data is preprocessed before statistical analysis is performed. Although, it is well known that preprocessing operations modify a voxel’s temporal spectrum and induce correlations. In this study, spatial correlations are described in terms of overlapping temporal frequency content between voxels. Identifying the location and extent of the induced correlations is the first step to compensate for unwanted variability, leading to more accurate interpretations from the data.

2477.   Influence of Anisotropic Blood Vessels Modeling in the EEG/MEG Forward Problem Using MRI.
Ernesto Cuartas-M1, Angel Torrado-C2,3, Juan A Hernandez-T2,3, José Ángel Pineda4, Eva Manzanedo-S2, and German Castellanos-D1
1Universidad Nacional de Colombia, Manizales, Caldas, Colombia, 2Medical Image Analysis and Biometry Lab, Rey Juan Carlos University, Madrid, Spain, 3Madrid-MIT M+Vision Consortium, Madrid, Spain, 4Centre for Biomedical Technology-U.P.M, Pozuelo de Alarcón, Spain

We analyzed the influence of neglect important tissue in the EEG/MEG forward problem using an anisotropic finite difference method. Specifically, we study the EEG/MEG dipole source estimation in the presence of an anisotropic blood vessels model. We used patient specific head models MRI-based, together with DWI tensor imaging to calculate anisotropic tensors in the white matter. The results shows that neglect the anisotropic blood vessels may induce significant errors in the source estimation for deep brain areas. It could potentially be an important drawback for source localization in focal temporal epilepsy.

2478.   Partial Volume Correction based on Spatial Variant Point Spread Function for Simultaneous PET-MR Imaging
Chenguang Peng1, Jinchao Wu1, Xingfeng Shao1,2, Yingmao Chen3, Quanzheng Li4, Georges El Fakhr4, and Kui Ying1
1Key Laboratory of Particle and Radiation Imaging, Ministry of Education, Department of Engineering, Beijing, China, 2Department of Bioengineering, UCLA, California, United States, 3Department of Nuclear Medicine, The general hospital of Chinese People's Liberation, Beijing, China, Beijing, China, 4Department of Radiology, Division of Nuclear Medicine and Molecular Imaging, Harvard Medical School, Boston, United States

PET image has relatively low resolution, and partial volume effect (PVE) is one of the major reason for this. Hybrid PET-MRI system offers us a great opportunity to synthesis PET and MRI, and MRI can provide PET with high resolution anatomical image which is a great supplementary information to correct PVE. In traditional method, point spread function is usually used to described PVE and is regarded as a spatial invariant constant which is not true in real PET system. In this work, we proposed a new method that considered spatial variant point spread function.

2479.   Weighted echo sharing technique (WEST) for highly undersampled multi-echo T2(*) weigthed data in Cartesian domain
Taejoon Eo1, Jinseong Jang2, and Dosik Hwang2
1Yonsei University, Seoul, Seoul, Korea, 2Yonsei University, Seoul, Korea

This study demonstrates that the accurate T2* weighted images can be obtained from highly undersampled Cartesian MGRE data by using WEST. While conventional method such as model-based fitting or CS are work with the reduction factor up to 5, the WEST can increase the reduction factor up to 16 in Cartesian trajectory. This method will be well applied for other various multi-contrast imaging such as DTI, SWI, etc.

2480.   Rapid segmentation of the cervical spinal cord on 3D MRI data with cord image analyzer (cordial): application to three-year follow-up data of MS patients with a progressive disease course
Michael Amann1, Simon Pezold2, Yvonne Naegelin3, Ketut Fundana2, Michaela Andelova3, Katrin Weier3, Christoph Stippich4, Ludwig Kappos3, Philippe Cattin2, and Till Sprenger1
1Neurology/Neuroradiology, University Hospital Basel, Basel, BS, Switzerland, 2Medical Image Analysis Center (MIAC), University of Basel, Basel, BS, Switzerland, 3Neurology, University Hospital Basel, Basel, BS, Switzerland, 4Neuroradiology, University Hospital Basel, Basel, BS, Switzerland

The "cord image analyzer (cordial)" pre-segments the spinal cord (SC) based on the continuous max-flow-approach, combined with a cross-sectional similarity prior. The SC surface is reconstructed by locating SC boundary based on image intensities. The cervical SC volume (CSCV) is defined by cutting planes perpendicular to the SC centerline. Reliability of cordial was assessed on controls with coefficients-of-variation of less than 1%. Applicability to clinical data was tested on a cohort of 48 MS patients. Multiple regression analysis revealed significant relation between CSCV loss and EDSS change.

2481.   Abnormal brain anatomy can introduce considerable bias to studies relying on FIRST – An improved segmentation pipeline
Xiang Feng1, Andreas Deistung1, Jesper Hagemeier2, Michael Dwyer2, Robert Zivadinov2,3, Juergen R. Reichenbach1, and Ferdinand Schweser2,3
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany, 2Buffalo Neuroimaging Analysis Center, Dept. of Neurology, School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, United States, 3MRI Molecular and Translational Imaging Center, Buffalo CTRC, State University of New York at Buffalo, Buffalo, NY, United States

In this study we show that the linear registration associated to the standard FIRST pipeline fails in the case of abnormal anatomy, potentially introducing a serious bias to clinical studies. To overcome this issue, we present an improved framework for FIRST segmentation that incorporates both a hybrid contrast generation and a non-linear registration.

2482.   Semi-automatic Prostate Segmentation via a Hidden Markov Model with Anatomical and Textural Priors
Christian Scharfenberger1, Dorothy Lui1, Farzad Khalvati2, Alexander Wong1, and Masoom Haider2,3
1Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada, 2Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada, 3Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada

The contouring and segmentation of the prostate gland is an important task in computer-aided prostate cancer screening using MRI. To assist medical professionals with the segmentation process, we propose a novel user-guided approach to prostate segmentation in MR images. The approach optimizes the energy components of a modified Decoupled Active Contour framework based on a Hidden Markov Model and a Rician likelihood to explicitly consider user guidance and textural and anatomical priors. Extensive experiments based on 10 patient cases and a variety of evaluation metrics showed that our approach provides a significant improvement over an existing semi-automatic segmentation approach.

2483.   Magnetic resonance Neurography (MRN) of brachial plexus at 1.5 T: Comparative evaluation of 3D SHINKEI versus DWIBS, our initial experience
Prashant Nair1, Rajagopal K V1, Rolla Narayana2, Indrajit Saha3, and Satish M1
1KMCH Hospital, Manipal University, Manipal, India, 2Philips Healthcare, Philips India Ltd, Bangalore, India, 3Philips Healthcare, Philips India Ltd, Gurgaon, Haryana, India

The purpose of our study was to compare 3D SHINKEI based MRN with the DWIBS neurography in the anatomical visualization of the brachial plexus at 1.5T. MRN image quality generated by 3D SHINKEI and DWIBS in five healthy volunteers was studied and was scored by two radiologists. While both the techniques were scored similar in visualization of the root, SHINKEI based MRN scored higher in depicting the trunk and cord area of brachial plexus with respect to DWIBS neurogrphy. Our ongoing work will include further optimization of SHINKEI based MRN at 1.5 T to improve brachial plexus visualization.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

A hardware-independent environment for MR acquisition and simulation
Kelvin Layton1, Stefan Kroboth1, Jochen Leupold1, Huijun Yu1, Feng Jia1, Sebastian Littin1, Tony Stöcker2, and Maxim Zaitsev1
1Medical Physics, University Medical Center Freiburg, Freiburg, BW, Germany, 2German Center for Neurodegenerative Diseases, Bonn, NRW, Germany

This work presents a sequence programming environment that is vendor-independent and supports rapid sequence prototyping through simulation and acquisition. The environment provides a drag-and-drop programming interface that allows researchers to run sequences on any hardware platform. Central to this work, is a new hardware-independent sequence file format that can easily be converted into hardware-dependent instructions for execution on an MR scanner. This is demonstrated by using a single sequence file to obtain experimental data using scanners from two different MR manufacturers. The improved workflow dramatically reduces sequence development time, provides new teaching opportunities and promotes vendor-independence across institutions.

2485.   Sub-second Compressed Sensing Reconstruction for Large Array Data Using GPUs
Ching-Hua Chang1 and Jim Ji1
1Texas A&M University, College Station, Texas, United States

Combining compressed sensing (CS) MRI with parallel imaging can reduce the scan time and/or improve reconstruction quality. However, the iterative reconstruction algorithm required by compressive sensing is time-consuming. Several groups have reported using graphics processing units (GPUs) to accelerate CS reconstruction. However, none has been applied to CS-MRI with parallel imaging. This paper presents a method that uses an alternating direction algorithm and GPUs for CS reconstruction from parallel receive channels, which is particularly suitable for large array data. Experiments show that it takes less than a second to reconstruct a 128×128×16 3-D image from 8-channel data, which is more than 20 times faster than a quad-core, high-end commodity CPU.

2486.   Berkeley Advanced Reconstruction Toolbox
Martin Uecker1, Frank Ong1, Jonathan I Tamir1, Dara Bahri1, Patrick Virtue1, Joseph Y Cheng2, Tao Zhang2, and Michael Lustig1
1Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA, United States, 2Department of Radiology, Stanford University, Stanford, United States

The high complexity of advanced reconstruction algorithms poses challenges for development and application of new reconstruction methods. Here, we present the Berkeley Advanced Reconstruction Toolbox, a framework for iterative image reconstruction. It consists of a programming library and a toolbox of command-line programs. The library provides common numerical operations and important algorithms including generic implementations of several iterative optimization algorithms. It supports parallel computation using multiple CPUs and GPUs. The command-line tools provide direct access to a wide range of functionality from basic operations on multi-dimensional arrays to complete implementations of advanced calibration and reconstruction algorithms for MRI.

2487.   Customized CPU Accelerated CS-based MRI Reconstruction Platform
Kyunghyun Sung1,2, Di Wu3, Fei Han1,2, Ziwu Zhou1,2, Peng Hu1,2, Holden Wu1,2, Alex Bui1,2, and Jason Cong3
1Radiological Sciences, University of California, Los Angeles, Los Angeles, CA, United States, 2Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States, 3Computer Science, University of California, Los Angeles, Los Angeles, CA, United States

Compressed sensing (CS) is an emerging technique that can reduce the imaging time at the cost of increased reconstruction runtime (i.e. time to reconstruct MRI images from raw k-space data). New algorithmic and acceleration approaches are needed to translate CS-based MRI methods into clinical practice. We propose to develop a new low cost CS-based MRI reconstruction platform using customized CPU accelerated implementation.

2488.   Faster-than-acquisition 4D sparse reconstruction for Cartesian 2D SENSE-type acquisition
Eric A. Borisch1, Joshua D. Trzasko1, Adam T. Froemming2, Roger C. Grimm1, Akira Kawashima2, Armando Manduca1, Phillip M. Young2, and Stephen J. Riederer1
1Mayo Clinic, Rochester, MN, United States, 2Radiology, Mayo Clinic, Rochester, MN, United States

A description of the successful implementation and integration into clinical workflow of a faster-than-acquisition sparse sampling reconstruction is presented, with DCE perfusion imaging of the prostate as an example application. A 4D time series with 55 timeframes is acquired with 2D SENSE acceleration in under 6 minutes, with the reconstruction completing in under 5 minutes; a reconstruction time of less than 5 seconds per 3D volume. Improved SNR and retained sharpness are observed relative to a traditional SENSE reconstruction of the same acquired data.

A low-cost flexible non-linear parallelized MR image reconstruction system
Fei Han1, Ziwu Zhou1, Kyunghyun Sung1, J Paul Finn1, and Peng Hu1
1Radiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States

Despite tremendous recent advances in non-linear image reconstruction methods, their clinical utility has been significantly held back by the limited computational power and development flexibility provided by the MRI system manufacturer. We developed a MR image reconstruction framework in which any custom made algorithms can be implemented on custom built computer nodes connected to the MR scanner such that k-space data is sent to the nodes for calculation and reconstructed images are sent back to the scanner system as part of the default pipeline. In this work, we demonstrate the benefit of this framework on 12 pediatric congenital heart disease patients who underwent cardiac MRI using a highly accelerated 4D cardiac phase-resolved contrast-enhanced MRA sequence.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2490.   Standardization and Automatization of Quality Assurance in Structural and Dynamic MRI.
Robin Antony Birkeland Bugge1, Atle Bjørnerud1, Wibeke Nordhøy1, and Øystein Bech Gadmar1
1Intervention Center, Oslo University Hospital, Oslo, Oslo, Norway

Quality assurance is essential both for MRI clinic and for research. Yet, the extent to which QA is performed varies significantly. The Norwegian Radiation Protection Authority made recommendations in 2005 that urged all clinics and centers using MRI to have at their disposal a quality assurance methodology that is independent of the MRI vendor. The MRI_QAP is an open source software designed to address these issues, expand on the existing procedures, remove subjective assessments and ensure consistent reports. The software consist of various seperated modules that perform different tasks; Geometric distortion, Signal to noise ratio, uniformity and dynamic stability analysis.

2491.   Exploring quality metrics for MRI imaging: comparing multiple reconstructions and measuring instrument calibration using low cost phantoms
Brian Hanna1, Naoharu Kobayashi1, Djaudat Idiyatullin1, Curtis Andrew Corum1, Brad Weegman1, Jinjin Zhang1, and Michael Garwood1
1Radiology, University of Minnesota, Minneapolis, MN, United States

A study of image quality metrics and calibration for MRI. We compared reconstruction methods and measured instrument calibration using low cost Lego phantoms with a short T2 relaxation time.

2492.   Extending BrainWeb for Evaluating Methods of Brain Volume Change: Simulation of Central and Peripheral Brain Atrophy
Kunio Nakamura1, Vladimir S. Fonov1, Nicolas Guizard1, Sridar Narayanan1, Douglas L. Arnold1, and D. Louis Collins1
1Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada

We have developed simulate MRI datasets with simulated atrophy that allows accuracy evaluation of image analysis methods in detecting volume changes in whole brain, gray matter, and white matter. We have simulated 3 types of atrophy (central, peripheral, and combination). We applied standard techniques as well as our in-house method to detect brain volume changes and quantitatively compared these methods. The results showed that SIENA in FSL tended to overestimate central brain atrophy and that tensor-based morphometry developed locally performed well in the combination of atrophy. The dataset will be publicly available as a part of BrainWeb.

2493.   A new approach for automatic image quality assessment
Thomas Küstner1,2, Parnia Bahar2, Christian Würslin1, Sergios Gatidis1, Petros Martirosian3, Nina Schwenzer1, Holger Schmidt1, and Bin Yang2
1Department of Radiology, University Hospital of Tübingen, Tübingen, Baden-Württemberg, Germany, 2Institute of Signal Processing and System Theory, University of Stuttgart, Stuttgart, Baden-Württemberg, Germany, 3Diagnostic and Interventional Radiology, University Hospital of Tübingen, Tübingen, Baden-Württemberg, Germany

A reliable and meaningful image quality assessment can be very demanding, especially when there is no reference or gold-standard available. Evaluation mainly depends on human observers, but due to the huge amount of acquired data, this task can be very time-consuming and costly. Hence an automatic evaluation is desired. We therefore propose a robust, accurate and flexible automatic evaluation system which is based on a machine-learning approach to evaluate certain diagnostic questions dependent on the chosen application and trained input data. Our framework achieves a test accuracy of 91.2% and hence can be used for automatic quality classification.

2494.   A generalized method for automated quality assessment in brain MRI
Bénédicte Maréchal1,2, Stephan Kannengiesser3, Kaely Thostenson4, Peter Kollasch5, Pavel Falkovskyi1,2, Jean-Philippe Thiran2, Reto Meuli6, Matt A. Bernstein4, and Gunnar Krueger1,2
1Siemens ACIT – CHUV Radiology, Siemens Healthcare IM BM PI & Department of Radiology CHUV, Lausanne, Switzerland, 2LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 3Siemens Healthcare, Erlangen, Germany, 4Department of Radiology, Mayo Clinic, Rochester, MN, United States, 5Siemens Healthcare, MN, United States,6CHUV Radiology, Lausanne, Switzerland

Automated quality assessment of MRI is of great importance to derive reliable diagnostic information. In this work, a synthetic noise-based method is proposed which allows automated data quality classification. Only a “prescan” measurement of noise and a single image acquisition are required. The validation based on 764 head scans confirms the robustness and reliability of the method. As integrated as a prototype in online image reconstruction, it can greatly improve clinical workflow as MR technologist is provided with immediate feedback and can potentially repeat low-quality scans within the same session.

2495.   Semi-automatic quantification of long-term stability and image quality of a parallel transmit system at 7T
Marcel Gratz1,2, Maximilian Völker2, Sören Johst2, Mark E Ladd2,3, and Harald H Quick1,2
1High Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany, 2Erwin L. Hahn Institute for Magnetic Resonance Imaging, University of Duisburg-Essen, Essen, Germany, 3Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany

An image-based approach to quantify the performance and long-term stability of parallel transmit (pTx) MR systems is presented that uses a specific target excitation. Semi-automatic analysis is performed with a custom-written Matlab software that automatically segments the acquired image and aims to obtain reference points as well as characteristic image properties that are compared to target parameters. Thus, the system performance can be tracked with multiple parameters quantitatively over time and compared to other pTx systems without further requirements. Moreover, fluctuations and drifts of the transmit power as well as timing problems may be detected.

2496.   Comparison of BRISQUE and SSIM as Image Quality Assessment (IQA) on MR optic nerve images.
Li Sze Chow1, Raveendran Paramesran1, and Martyn Paley2
1Electrical Engineering, University of Malaya, Kuala Lumpur, Wilayah Persekutuan, Malaysia, 2Academic Radiology, University of Sheffield, Sheffield, South Yorkshire, United Kingdom

A new No-Reference Image Quality Assessment (NR-IQA) model called Blind/referenceless image spatial quality evaluator (BRISQUE) uses scene statistics of locally normalized luminance coefficients to quantify possible losses of “naturalness” in the image. Structural Similarity Index (SSIM) is one of the most commonly used Full-Reference IQA (FR-IQA) method. This study employed the BRISQUE and SSIM methods in comparison in assessing the quality for four types of MR optic nerve images. It was verified that BRISQUE is more appropriate than SSIM in evaluating the quality of MR images; however modification will be required to re-train the SVM library.

2497.   Radiological and quantitative assessment of Compressed Sensing reconstruction of undersampled 3D brain images
Ian Marshall1, Gabriel Rilling1, Yuehui Tao2, Chaoran Du1, Samarth Varma1, Dominic Job1, Andrew Farrall1, and Mike Davies1
1University of Edinburgh, Edinburgh, United Kingdom, 2University of Oxford, Oxford, United Kingdom

Compressed Sensing (CS) has been shown to provide significant speed up of MRI with sufficient accuracy when judged by 'image error' against known ground truths. To be clinically useful, the images must also be of diagnostic quality and acceptable to radiologists. Very few reports have considered this crucial issue. In this study of 3D brain scanning, we found that radiologists rated 4-times and 6-times undersampled data reconstructed by CS higher than conventional least squares reconstruction. However, subtle artefacts made interpretation of deep brain structures difficult and caused significant differences in measurement of brain tissue volumes.

2498.   How to improve the accuracy of total water content measured using T2 relaxation
Sandra M. Meyers1, Shannon H. Kolind2, and Alex L. MacKay1,3
1Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada, 2Medicine, University of British Columbia, Vancouver, BC, Canada, 3Radiology, University of British Columbia, Vancouver, BC, Canada

Multi-component T2 relaxation is widely used to measure the myelin water fraction, but it can also be applied to measure the total water content (TWC). This work is the first to estimate theoretical errors in T2-based TWC measurement with simulations, and determine the impact of factors including the signal to noise ratio, flip angle inaccuracies (B1+ inhomogeneity), and Rician noise on the accuracy of TWC estimation. Simulations demonstrated that TWC could be measured with T2 to a high degree of accuracy (<3%), even in the presence of B1+ inhomogeneity and Rician noise, and suggestions are given to improve accuracy further.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2499.   Efficient Dictionary Design for MR Fingerprinting using Tree-Structured Vector Quantization
Zhitao Li1, Benjamin Paul Berman2, Diego R Martin3, Maria I Altbach3, and Ali Bilgin1,4
1Electrical and Computer Engineering, University of Arizona, Tucson, Arizona, United States, 2Applied Mathematics, University of Arizona, Tucson, Arizona, United States,3Department of Medical Imaging, University of Arizona, Tucson, Arizona, United States, 4Biomedical Engineering, University of Arizona, Tucson, Arizona, United States

Accurate parameter estimation in MR Fingerprinting (MRF) requires large dictionaries with many atoms, each with thousands of time points. Storage of such dictionaries require large memory and the matching process becomes increasingly demanding with increasing dictionary size. We propose a Tree Structured Vector Quantizer based clustering approach for MRF dictionary design. The proposed approach allows significant reduction in dictionary dimensions and can enable clinically relevant reconstruction accuracy and time which is a major bottleneck for clinical usefulness of MRF.

2500.   Fast reconstruction of highly-undersampled dynamic MRI using random sampling and manifold interpolation
Kanwal K Bhatia1, Anthony N Price2,3, Joseph V Hajnal2,3, and Daniel Rueckert1
1Biomedical Image Analysis Group, Imperial College London, London, United Kingdom, 2Centre for the Developing Brain, Kings College London, London, United Kingdom,3Biomedical Engineering Department, Kings College London, London, United Kingdom

This work describes an algorithm for fast dynamic MRI reconstruction based on random sampling and manifold-based interpolation. Results are demonstrated on both cardiac real-time and cardiac cine MRI, showing how the proposed algorithm performs at varying undersampling rates. The algorithm is fast, reconstructing 200 frames of real-time MRI in under 60 seconds, and can also be used as an initialisation to speed up convergence of more complex compressed sensing strategies.

2501.   Fast dictionary learning-based compresssed sensing MRI with patch clustering
Zhifang Zhan1, Yunsong Liu1, Jian-Feng Cai2, Di Guo3, Jing Ye1, Zhong Chen1, and Xiaobo Qu1
1Department of Electronic Science, Xiamen University, Xiamen, Fujian, China, 2Department of Mathematics, University of Iowa, Iowa City, Iowa, United States, 3School of Computer and Information Engineering, Xiamen University of Technology, Xiamen, Fujian, China

Compressed sensing (CS) exploit the sparsity of magnetic resonance (MR) images to realize accurate reconstruction from the undersampled k-space data. Recently, there has been a growing interest in the study of adaptive sparse representation of MR images to achieve better reconstructions. However, most adaptive dictionary training processes are based on all the image patches and usually time-consuming. In this work, we proposed a fast dictionaries learning method that takes advantage of the geometric directions in classified similar patches. Experiments on T2-weighted brain image data show our proposed method improve the reconstruction quality both on reducing artifacts and minimizing reconstruction errors.

2502.   Dictionary Learning for Compressive T2 Mapping with Non-Cartesian Trajectories and Parallel Imaging
Benjamin Paul Berman1, Mahesh Bharath Keerthivasan2, Zhitao Li2, Diego R. Martin3, Maria I. Altbach3, and Ali Bilgin2,4
1Program in Applied Mathematics, University of Arizona, Tucson, Arizona, United States, 2Electrical & Computer Engineering, University of Arizona, Tucson, Arizona, United States, 3Medical Imaging, University of Arizona, Tucson, Arizona, United States, 4Biomedical Engineering, University of Arizona, Tucson, Arizona, United States

A non-Cartesian and multi-channel method of dictionary learning and compressed sensing reconstruction leads to improved T2 parameter mapping. The imaging problem is constrained to have a sparse representation within a dictionary. The principal components of the T2 decay are reconstructed, and the addition of the dictionary constraint leads to a reduction in noise and artifacts.

2503.   Sparsity-Promoting Orthogonal Dictionary Updating for Highly Undersampled MRI Reconstruction
Jinhong Huang1,2, Xiaohui Liu1, Wufan Chen1, and Yanqiu Feng1
1Guangdong Provincial Key Laborary of Medical Image Processing, School of Biomedical Engineering, Southern Medical University, Guangzhou, Guangdong, China, 2School of Mathemtics and Computer Science, Gannan Normal University, Ganzhou, Jiangxi, China

Image reconstruction employing adaptive sparsifying transform has demonstrated promising performance in compressed sensing magnetic resonance imaging. However, conventional overcomplete dictionary learning based methods are computationally expensive. In this work, we present a novel sparsity-promoting orthogonal dictionary updating method (SPODU) for efficient image reconstruction from highly undersampled MRI data. To further improve reconstruction, the deterministic annealing like strategy is combined into the algorithm. Experimental results demonstrate that the proposed SPODU algorithm is more efficient and accurate than the dictionary learning based method which using K-SVD for sparse coding, and thus has potential application in practice.

Accelerating MR Parameter Mapping Using Manifold Recovery
Chao Shi1, Yihang Zhou1, Yanhua Wang1, Dong Liang2, Xiaojuan Li3, and Leslie Ying1,4
1Electrical Engineering, University at Buffalo, SUNY, Buffalo, New York, United States, 2Paul C. Lauterbur Research Center for Biomedical Imaging, Shenzhen Institute of Advanced Technology, Shenzhen, Guangdong, China, 3Department of Radiology and Biomedical Imaging, University of California at San Francisco, San Francisco, California, United States, 4Biomedical Engineering, University at Buffalo, SUNY, Buffalo, New York, United States

We propose a novel method to accelerate parameter mapping in this abstract. We model MR parameter mapping as a problem to recover a parametric manifold. An iterative algorithm is proposed to recover the manifold from undersampled data based on the parametric model. The method iteratively alternates between reconstructing the image series and recovering the parameters. Both simulation and experimental results demonstrate the potential of highly accelerated parameter mapping by the proposed method.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

Reduced FOV Imaging Near Metal Using 2D Multispectral Imaging and Very Selective Outer Volume Suppression
Valentina Taviani1, Daniel Litwiller2, Kevin M. Koch3, and Brian A. Hargreaves1
1Radiology, Stanford University, Stanford, CA, United States, 2GE Healthcare, Rochester, MN, United States, 3Biophysics and Radiology, Medical College of Wisconsin, Milwaukee, WI, United States

Outer Volume Suppression (OVS) using high-bandwidth quadratic-phase RF pulses was used for reduced-FOV 2D Multispectral Imaging (MSI) near metal. OVS gradient reversal and a modified acquisition strategy were used to minimise unintentional saturation of off-resonance near metal. The technique was demonstrated in a phantom consisting of a metal implant embedded in agar. Clinical applications of the proposed method for spine imaging and MR-guided FUS (Focused Ultrasound Surgery) planning were presented. The ability to reduce the encoded FOV translated in shorter echo train lengths, i.e. reduced blurring, at the expense of slightly reduced SNR.

2506.   Compressed sensing accelerated broadband 3D phase encoded turbo spin-echo imaging for geometrically undistorted imaging in the presence of field inhomogeneities
Jetse van Gorp1, Chris Bakker1,2, Job Bouwman1, Jouke Smink3, Frank Zijlstra1, and Peter Seevinck1
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, 2Department of Radiology, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, 3Philips, Best, Noord-Brabant, Netherlands

In this work a compressed sensing (CS) accelerated 3D phase encoded turbo-spin echo (3D-PE-TSE) sequence was used to obtain geometrically undistorted images in the presence of titanium in a clinically acceptable time frame (<10min). By ordering the acquired echo’s in spherical layers with an equal number of sampling points it was possible to combine TSE and CS acceleration to achieve a factor 60 scan time acceleration compared to a 3D-PE-SE scan. Phantom and in vivo results confirm that the presented method can be used for investigations where spatial accuracy is required.

2507.   Imaging of the Spine with Metal Implants Using High-Bandwidth RF Pulses from a Local Tx/Rx Coil
Theresa Bachschmidt1,2, Johanna Schöpfer3, Stephan Biber2, Peter Jakob1, and Mathias Nittka2
1Department of Experimental Physics 5, University of Würzburg, Würzburg, Germany, 2Magnetic Resonance, Siemens AG, Erlangen, Germany, 3Corporate Technology, Siemens AG, Erlangen, Germany

Spinal fusion is a common surgery, which often requires follow-up treatments. However, the compensation of metal-induced through-plane distortion is time-consuming and its application in clinical routine is limited. Distortion through-plane is even enhanced at 3T compared to 1.5T and demands reduction before it is corrected; it scales inversely with the bandwidth of the RF pulse. Local transmit coils feature higher peak B1, hence enable higher RF bandwidths, than whole-body birdcage coils. This work presents the capability of a prototype Tx/Rx spine coil with respect to minimizing through-plane distortion. RF bandwidths of 3.3 kHz can decrease time-consuming artifact compensation significantly.

2508.   Automatic Detection of Metal Implant Location in Hexagonally Sampled MAVRIC-SL
Bragi Sveinsson1, Valentina Taviani1, Garry Gold1, and Brian Hargreaves1
1Radiology, Stanford University, Stanford, CA, United States

Multi-spectral Imaging (MSI) allows imaging close to metal implants at the cost of increased scan time. Previous work has demonstrated how MSI scan time can be shortened by hexagonally undersampling ky/kz-space and removing the resulting aliased replicas using a zeroing mask. This required the extra step of the operator providing the approximate location of the implant to the reconstruction software. In this work, we demonstrate how the detection of the implant location can be fully automated by hexagonally sampling adjacent slices in a complementary manner and combining the bins to get an estimate of the slice profile with minimal aliasing.

2509.   Initial experience with artefact reduction sequences and MR conditional cochlear implants
Jonathan Paul Ashmore1, Mathias Nittka2, Lyndall Blakeway3, Steve Connor1,3, and Geoff Charles-Edwards3
1Neuroradiology, King’s College Hospital NHS Foundation Trust, London, London, United Kingdom, 2Siemens Healthcare, Erlangen, Germany, 3Guy’s & St Thomas’ NHS Foundation Trust, London, United Kingdom

A growing number of MR conditional cochlear implants can now be scanned safely without requiring temporary surgical removal of the internal magnet. However, with the magnet in situ the resultant images have large areas of signal drop-out and distortion around the device which may obscure nearby structures of interest, even with spin echo sequences and large receiver bandwidths. The aim of this work was to evaluate two new options available on a clinical MRI scanner for reducing metal artefacts, View Angle Tilting (VAT) and Slice Encoding for Metal Artifact Correction (SEMAC)

2510.   Metal artifact correction using sensitivity information
Dongchan Kim1, JaeJin Cho1, Kinam Kwon1, and HyunWook Park1
1Electrical engineering, KAIST, Daejeon, Yuseong-Gu, Korea

MRI is one of the most powerful imaging modalities for clinical diagnosis. However, the use of MRI is limited for the patients who have metallic implants, because metallic implants causes severe field inhomogeneity, which causes the geometrical distortion in image and the slice profile. To resolve these problems, slice encoding for metal artifact correction (SEMAC) technique was proposed. But SEMAC is not practical technique due to the long imaging time. In this work, we propose a sensitivity information based metal artifact correction (MAC) technique to reduce the imaging time for multi-contrast and time-series imaging.

2511.   Metal Implant-Induced Spectral Range Optimization using Rapid 3D-MSI Calibration Scans
Kevin M Koch1
1Biophysics and Radiology, Medical College of Wisconsin, Milwaukee, WI, United States

3D Multi-Spectral Imaging (3D-MSI) techniques, such as MAVRIC, SEMAC, and MAVRIC SL collect multiple independently spatial-encoded images at discrete Larmor frequency offsets. Prospective knowledge of the range and location of off-resonant spins can aid in optimizing the efficiency of these sequences. Here we present a concept of 3D-MSI calibration scanning that can provide such information through an acquisition on the order of 1 minute. In addition, we demonstrate a practical method to automatically determine off-resonance frequency ranges determination using such calibration data. For many implant cases of lower magnetic susceptibility materials, such a calibration and off-resonance range computation can substantially improve the efficiency of 3D-MSI techniques.

2512.   Evaluation of T2-weighted WARP sequences in Patients with Spinal Prosthesis
shun qi1, Ying Liu1, Langlang Gao1, Panli Zuo2, Mathias Nittka3, and Hong Yin1
1Xijing Hospital, Fourth Military Medical University, xian, shaanxi, China, 2Siemens Healthcare, MR Collaborations NE Asia, shaanxi, China, 3Siemens Healthcare, Germany, Germany

MR images with WARP sequences significantly reduced metal-related artifacts and improved delineation of the prosthesis and periprosthetic region therefore increased the diagnostic sensitivity in patients with clinical abnormities.

2513.   An improved complex image combination algorithm for SEMAC
Daehyun Yoon1 and Brian A Hargreaves1
1Radiology, Stanford University, Palo Alto, CA, United States

A denoising algorithm to improve complex summation of spectral images for Slice Encoding for Metal Artifact Correction (SEMAC) sequence is presented. In SEMAC, multiple spectral images are collected, and combined together to image spins with a huge resonance frequency variation around metallic implants. The complex summation has not been often used for combining these spectral images because of a serious SNR degradation even though its image sharpness around the metal is better than other combination methods. Here we introduce a new image combination algorithm to improve the SNR for the complex summation to provide both sharpness and high SNR.

2514.   Phase unwrapping near metal implants with prior knowledge of the implant geometry
Laura J. King1, Philip J. Bones1, and Rick P. Millane1
1Department of Electrical and Computer Engineering, University of Canterbury, Christchurch, New Zealand

The three-point Dixon technique can be used to successfully suppress fat near metal implants if the phase shift due to the B0 field inhomogeneities can be estimated accurately. This research describes a new technique where the phase unwrapping is guided by prior knowledge of the implant. Using an approximate model of the implant location and orientation, the phase unwrapping is simplified to estimating the difference between the model and true phase shift. The model is rotated and translated to minimise the phase unwrapping required. Initial results obtained from simulation are shown.

2515.   Numerical RF Pulse Optimization to Reduce Peak B1 for Multi-spectral Imaging around Metal Implants
Andrew M. Huettner1, Andrew S. Nencka1, L.Tugan Muftuler2, and Kevin M. Koch3
1Biophysics, The Medical College of Wisconsin, Milwaukee, Wisconsin, United States, 2Neurosurgery, The Medical College of Wisconsin, Milwaukee, Wisconsin, United States,3Biophysics and Radiology, The Medical College of Wisconsin, Milwaukee, Wisconsin, United States

This work demonstrates nonlinear constrained numerical optimization for RF pulse design applied to a pulse sequence for multi-spectral imaging around metal implants. By reducing the peak B1 of the refocusing pulse though numerical optimization, the maximum tip angle permitted on the scanner, based on hardware and RF safety limits, was increased from 140 degrees to 180 degrees.

2516.   Fluid-Sensitive Metal Artifact Reduction using a 3D-Composite Fast Steady State Free Precession (COFIsp) sequence
Xeni Deligianni1,2, Thomas Egelhof2, Thorsten Wischer2, Reinhard Elke2, and Oliver Bieri1
1Radiology, Division of Radiological Physics, University of Basel Hospital, Basel, NA, Switzerland, 2Merian Iselin Klinik, Basel, NA, Switzerland

Magnetic resonance imaging (MRI) in the vicinity of metal hardware is stll characterized by long scan times for the acquisition of composite images and low fluid sensitivity. Here we propose an optimized composite fast steady state free precession sequence (COFIsp) as a fast, clinically feasible alternative for acquisition of fluid-sensitive and distortion-free images in the presence of metal. For distortion correction additional prephasing gradients and optimized phase encoding orientation were investigated. The sequence allows good artifact correction and high fluid contrast which is very important for the visualization of inflammation.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2517.   Estimation of Abdominal Aortic Aneurysm Stiffness using MR Elastography: Is Stiffness Superior to Diameter?
Shantanu Warhadpande1, William Kenyhercz2, Priyanka Illapani2, Brian Raterman3, Joshua Dowell3, Michael Go3, Patrick Vaccaro3, Jean Starr3, Richard White3, and Arunark Kolipaka3
1The Ohio State University College of Medicine, Columbus, OH, United States, 2The Ohio State University, Columbus, OH, United States, 3The Ohio State University Wexner Medical Center, OH, United States

It is known that changes in Abdominal Aortic Aneurysms (AAA) wall stiffness (WS) can reflect extra-cellular matrix integrity, a key factor in the pathophysiological development of AAA and the risk for rupture. Therefore, our study applied Magnetic Resonance Elastography (MRE) to determine aortic WS in 10 AAA patients. Our hypothesis was that there would be no relationship between aortic WS and AAA diameter and our results supported the hypothesis with a poor linear correlation of R2 =0.0051. In the future, a more personalized approach to AAA management using MRE-derived WS might be warranted to better assess the risk for rupture.

2518.    Theoretical Performance and Sampling Limits in Steady-State Magnetic Resonance Elastography
Joshua Trzasko1, Kevin Glaser1, Arvin Arani1, Armando Manduca1, David Lake1, Phillip Rossman1, Shivaram Poigai Arunachalam1, Kiaran McGee1, Richard Ehman1, and Philip Araoz1
1Mayo Clinic, Rochester, MN, United States

In magnetic resonance elastography (MRE), mechanically induced motion is estimated from a time-encoded series of phase-contrast images and used to generate quantitative spatial maps of tissue stiffness. Like most dynamic/parametric applications, MRE has flexibility regarding acquisition parameter assignment, particularly with respect to motion encoding gradients (MEG). In this work, we derive the Cramer-Rao Lower Bound (CRLB) for the complex harmonic signal — which completely describes mechanically induced motion in single-frequency, steady-state MRE — and use this to define performance limits of experimental MRE setups. This can serve as an objective tool for developing and comparing different protocols. Using this bound, we then identify minimum number of data samples needed for complex harmonic estimation to be well-posed.

2519.   Consistent SNR Measures for Magnetic Resonance Elastography
Armando Manduca1, David S Lake1, Khang T Huynh1, Rehman S Eon1, Elizabeth M Annoni1, and Richard L Ehman1
1Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States

In magnetic resonance elastography, the calculated stiffness values are affected by noise, which is amplified by the inversion process. It would be useful in practice to establish that, beyond some SNR threshold, stiffness calculations are accurate within some confidence limit. A variety of SNR measures have been proposed for MRE, including variations of displacement SNR and octahedral shear strain SNR. We demonstrate here that the proper SNR measure depends on the inversion algorithm used, and, more precisely, on the order of derivatives in the inversion process, and show that Laplacian-based SNR measures are required for commonly used Helmholtz inversions.

Mechanical properties and force output of quadriceps muscle following eccentric exercise
P Kennedy1, L MacGregor2, E Barnhill1, A Cooper1, L Hiscox1, C Brown3, J Braun4, I Sack4, E van Beek1, A Hunter2, CL Johnson5, and N Roberts1
1Clinical Research Imaging Centre (CRIC), University of Edinburgh, Edinburgh, United Kingdom, 2School of Sport, University of Stirling, Stirling, United Kingdom, 3The Mentholatum Company Ltd., Glasgow, United Kingdom, 4Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany, 5Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, United States

Exercise Induced Muscle Damage (EIMD) is associated with force reduction, inflammation and pain after exercise and is often accompanied by Delayed Onset Muscle Soreness (DOMS). In this study significant variation in muscle stiffness, measured using Magnetic Resonance Elastography (MRE), and force output are determined following an eccentric exercise protocol. Subjective pain assessment revealed significant pain increase following damage indicating the presence of DOMS. The rectus femoris muscle group is primarily affected with localised oedema present on T2 weighted imaging.

2521.   In Vivo Waveguide Elastography of White Matter Tracts in the Full Human Brain
Anthony Joseph Romano1, Jing Guo2, Michael Scheel2, Sebastian Hirsch2, Juergen Braun3, and Ingolf Sack2
1Physcial Acoustics, Naval Research Laboratory, Washington, DC, United States, 2Radiology, Charite-Universitatsmedizin, Berlin, Germany, 3Medical Informatics, Charite-Universitatsmedizin, Berlin, Germany

Waveguide Elastography combines Magnetic Resonance Elastography, Diffusion Tensor Imaging and Orthotropic inversions for the analysis of the anisotropic properties of white matter. Previously, this method was applied to the Cortico-spinal tracts of healthy human volunteers and to patients diagnosed with Amyotrophic Lateral Sclerosis. Here we apply this approach to the classification of the anisotropic properties of the 12 major white matter tracts in the human brain. This method is intended as a new modality to assess white matter structure and health by means of the evaluation of the anisotropic elasticity tensor of nerve fibers.

2522.   Fast 2D Hepatic MR Elastography for Free-Breathing and Short Breath Hold Applications
Kevin Glaser1, Jun Chen1, and Richard Ehman1
1Radiology, Mayo Clinic, Rochester, MN, United States

MR elastography (MRE) is a technique for noninvasively assessing hepatic fibrosis that has a high diagnostic accuracy and is safer and less expensive than biopsy. Typically, MRE requires multiple breath holds of 10-20 seconds, which may not be possible for some patients and can add several minutes to clinical liver MRI exams. In this work, we demonstrate an implementation of 2D hepatic MRE that can be performed in a single 3.2-second breath hold or while free breathing that can significantly reduce the number and duration of breath holds required for performing MRE and improve clinical patient throughput.

2523.   Combining Conjugate and Non-Conjugate Wave Data for Faster Elastography
Roger Grimm1, Eric Stinson1, and Richard Ehman1
1Mayo Clinic, Rochester, MN, United States

Elastography sampling with gradient echo sequences can lead to long scan times. Scan efficiency is limited by gradient heating concerns and the need to synchronize the TR to the period of motion excitation. These inefficiencies can be ameliorated by using a phase advancing TR. This work uses a phase advancing TR and acquires the minimum 7 samples to provide complex sampling of the wave field along all 3 axes. The proposed method uses a half-NEX like reconstruction to combine the conjugate and non-conjugate samples.

2524.   Three dimensional three parameter direct inversion MR elastography of incompressible transverse isotropic media: Application to in vivo soleus muscle
Jing Guo1, Sebastian Hirsch1, Jürgen Braun2, and Ingolf Sack3
1Radiology, Charité - Universitätsmedizin Berlin, Berlin, Berlin, Germany, 2Department of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany,3Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany

An anisotropic MR elastography method is introduced which relies on shear fields in incompressible transversely-isotropic media. The method provides three independent moduli, μ12, μ13 and E3, the shear moduli in the planes of isotropy and symmetry as well as the Young's modulus parallel to the fiber axis, respectively. The method is demonstrated on the soleus in ten healthy volunteers and reveals that 1) E3>μ13>μ12 and 2) elasticity parameters along the muscle fiber axis are higher in the right leg compared to the left leg which is most likely resulting from the right leg dominance of soleus function in our group.

2525.   The Accuracy of Multi-Slice Multi-Frequency MR Elastography in a Brain Stiffness Mimicking Phantom
Arvin Arani1, Ondrej Slezak1, Nikoo Fattahi1, Kevin J Glaser1, Joel Felmlee1, Armando Manduca2, Clifford R. Jack1, Richard L. Ehman1, and John Huston III1
1Radiology, Mayo Clinic, Rochester, Minnesota, United States, 2Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States

Several groups have investigated the use of MR elastography in neurological diseases, using a single vibration frequency or the use of multi-frequency data to acquire information about the viscoelastic properties of brain tissues. Although the precision, repeatability, and sensitivity to changes in these viscoelastic parameters has been reported in phantoms and in vivo, the accuracy of either the single-frequency or multi-frequency stiffness measurements has not been thoroughly evaluated experimentally. The objective of this work was to evaluate the accuracy of both single-frequency and multi-frequency brain MRE in a geometrically accurate brain stiffness mimicking phantom and compare it with mechanical testing.

2526.   Observation of Functional Magnetic Resonance Elastography (fMRE) in Mouse Brain
Samuel Patz1,2, Katharina Schregel3, Iga Muradyan1,2, Angelos Kyriazis1,2, Jens Wuerfel3,4, Srini Mukundan1,2, and Ralph Sinkus5
1Brigham & Women's Hospital, Boston, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Institute of Neuroradiology, University Medicine Goettingen, Goettingen, Germany, 4NeuroCure, Charité University Medicine, Berlin, Germany, 5Imaging Sciences & Biomedical Engineering, Kings College, London, United Kingdom

Using Magnetic Resonance Elastography (MRE), we observed changes in mouse brain cortical stiffness associated with changes in the amplitude of an externally applied acoustic stimulus.

2527.   A small animal MR Elastography setup to study skeletal muscle damage and the etiology of pressure ulcers and related deep tissue injury.
Jules Nelissen1,2, Larry de Graaf1, Tom Schreurs1,2, Willeke Traa3, Kevin Moerman4, Cees Oomens3, Aart Nederveen4, Klaas Nicolay1, and Gustav Strijkers1,2
1Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands, 2Biomedical Engineering and Physics, Academic Medical Center, Amsterdam, Netherlands, 3Soft Tissue Biomechanics and Engineering, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands, 4Department of Radiology, Academic Medical Center, Amsterdam, Netherlands

In order to study the role of tissue mechanical properties with MR Elastography (MRE) in the etiology of pressure ulcer related deep tissue injury a MRE actuator was added to a previously proposed MR compatible indentation setup for sustained tibialis anterior (TA) muscle loading in rats. We expect that the use of this novel device will provide new insights in the etiology of pressure ulcer related deep tissue injury.

2528.   A retrofit technology for MR Elastography
Tomokazu Numano1, Yoshihiko Kawabata2, Kazuyuki Mizuhara3, Toshikatsu Washio4, Junichi Hata5, and Kazuhiro Homma4
1Radiological Sciences, Tokyo Metropolitan University, Arakawa-ku, Tokyo, Japan, 2Takashima Seisakusho Co., Ltd., Tokyo, Japan, 3Tokyo Denki University, Tokyo, Japan,4National Institute of Advanced Industrial Science and Technology (AIST), Ibaraki, Japan, 5Graduate School of Medicine Keio University, Tokyo, Japan

In this work we developed a new retrofit MR Elastography (MRE) system consist of a gradient-echo type multiecho MR sequence and a wirelessly synchronized pneumatic vibration system. In the previous work (ISMRM2014, 1686), we introduced the wireless TR synchronization system with a dipole antenna tuned for the RF excitation frequency to make any electrical wiring from the MRI electronics unnecessary. However, the dipole antenna connected to the cable through a hole in the RF shield room, may introduce RF noise into the shield room and cause MR noises. In this study, we replaced the cable by an optical fiber, to prevent the external RF noise enter the magnet room.

2529.   Validation of Waveguide Magnetic Resonance Elastography Using Finite Element Model Simulation
Ria Mazumder1,2, Renee Miller3, Haodan Jiang4, Bradley D. Clymer1, Richard D. White2,5, Alistair Young3, Anthony Romano6, and Arunark Kolipaka2,5
1Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, United States, 2Department of Radiology, The Ohio State University College of Medicine, Columbus, OH, United States, 3Department of Anatomy with Radiology, The University of Auckland, New Zealand, 4Department of Research and Development, Ohio Supercomputer Center, OH, United States, 5Department of Internal Medicine-Division of Cardiology, The Ohio State University College of Medicine, OH, United States, 6Naval Research Laboratory, DC, United States

Anisotropic mechanical properties of tissues vary in response to different pathological conditions; hence, the development of a technique for non-invasive anisotropic stiffness quantification is expected to have diagnostic and prognostic significance. Recently, waveguide magnetic resonance elastography (MRE) has been used to non-invasively estimate anisotropic stiffness of biological tissues by measuring tissue deformation as a result of external perturbation in directions specified by fiber orientation. In this study, we simulate fibers using finite element modeling in a cylindrical rod to validate the stiffness measurements obtained using waveguide MRE. Our results show that the technique can successfully estimate anisotropic stiffness in an orthotropic material.

2530.   Finger tapping experiment observed by brain Magnetic Resonance Elastography
Ondrej Holub1, Simon Lambert1, Katharina Schregel2, Lynne Bilston3, Samuel Patz4,5, and Ralph Sinkus1
1Imaging Sciences and Biomedical Engineering, King's College London, London, London, United Kingdom, 2University Medicine Goettingen, Institute of Neuroradiology, Goettingen, Goettingen, Germany, 3University of New South Wales, Neuroscience Research Australia, Sydney, New South Wales, Australia, 4Brigham and Women's Hospital, Radiology, Boston, Massachusetts, United States, 5Harvard Medical School, Radiology, Boston, Massachusetts, United States

External finger tapping stimulus was successfully correlated to changes of the material properties in-situ. Work presents a novel imaging modality base on Magnetic Resonance Elastography (MRE) to provide additional information to fMRI assessment.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2531.   Mapping Magnetisation using a Magnetoencephalography System
Richard Bowtell1, Mobeen Ali1, Jason Medica1, Ingrid Vella1, and Mattthew Brookes1
1School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom


Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2532.   Introducing prior knowledge through the non-local means filter in model-based reconstructions improves ASL perfusion imaging
Samuel Fielden1, Li Zhao1, Max Wintermark2, and Craig Meyer1,3
1Biomedical Engineering, University of Virginia, Charlottesville, Virginia, United States, 2Radiology, Stanford University, Palo Alto, California, United States, 3Radiology, University of Virginia, Charlottesville, Virginia, United States

The major disadvantage for ASL is low SNR and low spatial resolution of the resulting images. The hypothesis of this work is that the SNR and spatial resolution of perfusion images acquired with ASL can be improved by incorporating side information from high-SNR anatomical images into iterative reconstructions of the data. Here, we use the non-local means filter, trained on high-SNR anatomical images, to denoise and sharpen the ASL reconstruction results. We have tested this method in a simulated numerical phantom and with in-vivo data and found that it improves SNR and reduces error.

2533.   Non-contrast Enhanced 4D Artery-selective MR Angiography using Spatially Selective Saturation
Thomas Lindner1, Ulf Jensen-Kondering1, Fritz Wodarg1, Olav Jansen1, and Michael Helle2
1Department of Radiology and Neuroradiology, UKSH, Kiel, Germany, 2Philips Research, Hamburg, Germany

In this study, we present a method for dynamic artery-selective non-contrast enhanced magnetic resonance angiography. This method is based on the inflow effect of arterial blood. Two individual cylinder pulses are placed over two major brain feeding arteries, resulting in the image acquisition of the third remaining vessel. Over a time-course of 1450ms, six individual temporal phases with a frame-rate of 200ms can be acquired, while the total acquisition time is kept to five minutes. This method was successfully applied in healthy volunteers, visualizing even the distal parts of the individual flow territories of the intracranial arteries.

2534.   Systematic evaluation of region-wise iVASO reproducibility at multiple blood water nulling times
Swati Rane1, Pratik Talati2, Manus Donahue3,4, and Stephan Heckers2
1Radiology and Radiological Sciences, Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, 2Psychiatry, Vanderbilt University, Nashville, TN, United States, 3Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, 4Neurology, Vanderbilt University, Nashville, TN, United States

In this work we assessed the intra- and inter-scan reproducibility of iVASO at multiple inversion times (TI) of blood in the cortex and the hippocampus. iVASO reproducibility was higher at shorter TIs for the hippocampus compared to the cortex. Reproducibility was assessed using intra-class correlation analysis and found to be similar to that of arterial spin labeling approaches.

2535.   Evaluation of GLACIER sampling for 3D DCE-MRI
Yinghua Zhu1, Yi Guo1, Sajan Goud Lingala1, R. Marc Lebel2, Meng Law1, and Krishna Nayak1
1University of Southern California, Los Angeles, CA, United States, 2GE Healthcare, Calgary, Canada

The proposed GoLden Angle CartesIan Encoded Randomization (GLACIER) sampling scheme combines two existing techniques, Poisson ellipsoid pseudorandom undersampling and golden angle (GA) Cartesian sampling. GLACIER randomizes ky-kz phase encode along golden angle radials with designed sampling probability. Constrained reconstruction results of GLACIER are compared with two conventional methods in retrospective studies. Normalized root-mean-square error is used as an objective image quality metric. GLACIER algorithm is fast and allows online sampling pattern generation. GLACIER shows comparable results with Poisson ellipsoid and improved quality over conventional GA method in retrospective studies.

2536.   A Novel Sequence to Improve Signal to Noise in DCE Measurements
Jason Kraig Mendes1, Scott McNally2, and Dennis L Parker1
1Radiology, University of Utah, Salt Lake City, Utah, United States, 2Clinical Radiology, University of Utah, Salt Lake City, Utah, United States

Dynamic contrast enhanced (DCE) imaging is useful in evaluating the functional status of a vascular system. Demands for high temporal and spatial resolution often lead to low signal to noise in the measurements. A novel sequence is presented that calculates concentration from bot T1 and T2 simultaneously to increase signal to noise.

2537.   In vivo rapid 3D Microscopic DTI combining Super Resolution Reconstruction and Reverse Gradient correction method
Ulysse Gimenez1, Antoine Triquet1, and Hana Lahrech1
1Clinatec, CEA, Grenoble, Rhones-Alpes, France

Super Resolution Reconstruction is performed on 2D EPI distorted diffusion images acquired in vivo on brain mouse at 9.4T. At this field, the feasibility to correct severe distortions with Reverse Gradient method is proved. Based on three orthogonal “low resolution” DTI acquisition (120*120*360 µm3), SRR is successfully performed allowing the calculation of 3D isotropic high spatial resolution DTI (120*120*120 µm3). Thus, high spatial resolution DTI parameter maps can be visualized. Fibertracking is also computed and fine white matter structures such as the fornix can be rebuilt.

2538.   Image Reconstruction for Accelerated Diffusion Tensor Imaging Using Joint Low-Rank and Sparsity Constraints
Sen Ma1, Xiaodong Ma2, and Hua Guo2
1Department of Electronic Engineering, Tsinghua University, Beijing, China, 2Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China

This paper proposes an effective joint reconstruction method to accelerate diffusion tensor imaging acquisition, combining the low-rank structure and sparsity constraints of the correlated diffusion-weighted images. We show that by jointly enforcing low-rank and sparsity constraints, we can achieve high reduction factor of diffusion tensor imaging acquisition while maintaining rather accurate reconstruction result.

2539.   Fast, whole brain Radial Diffusion Spectrum Imaging (RDSI) via Simultaneous Multi Slice Excitation
Steven Baete1,2, Tiejun Zhao3, and Fernando Emilio Boada1,2
1Center for Advanced Imaging Innovation and Research (CAI2R), NYU School of Medicine, New York, NY, United States, 2Center for Biomedical Imaging, Dept. of Radiology, NYU School of Medicine, New York, NY, United States, 3Siemens Healthcare, Siemens Medical Solutions USA, Inc., New York, NY, United States

Diffusion Spectrum Imaging (DSI) has become a powerful tool for non-invasive imaging of white matter brain architecture. Unfortunately, widespread clinical implementation has been hampered by long acquisition times. DSI approaches sampling q-space in a radial fashion have been shown to be more efficient and accurate. When combined with a multi-echo train, RDSI provides significant throughput improvements over conventional DSI. We demonstrate a further acceleration of multi-echo RDSI by extending this technique with Simultaneous Multi-Slice excitation. The combined acceleration allows for whole brain fully sampled RDSI in under 7 min.

2540.   Body DWI Using nCPMG FSE
Eric Kenneth Gibbons1, Shreyas Vasanawala2, John Mark Pauly3, and Adam Bruce Kerr3
1Department of Bioengineering, Stanford University, Stanford, California, United States, 2Department of Radiology, California, United States, 3Department of Electrical Engineering, Stanford University, California, United States

Here we present an modified non-CPMG FSE approach applied to abdominal DWI. We find that by modifying mixing crushers and use ESPIRiT/SENSE reconstruction we are able to achieve nearly artifact and distortion-free images that are often associated with body DWI images while also maintaining an appropriate echo train length.

2541.   TOF-MRA reconstruction from undersampled data: Comparison of three different regularization methods
Akira Yamamoto1, Koji Fujimoto1, Yasutaka Fushimi1, Tomohisa Okada1, Kei Sano2, Toshiyuki Tanaka2, and Kaori Togashi1
1Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, Japan, 2Department of Systems Science, Graduate School of Informatics, Kyoto University, Kyoto, Kyoto, Japan

Three different regularization methods, L1-norm, wavelet, and total variation in NESTA method for undersampled TOF-MRA image reconstruction were evaluated. In qualitative visual analysis, subtle but distinct difference was noted among them. In quantitative analysis, L1-norm showed the largest vessel-brain-ratio and more than 30 % undersampled data seemed sufficient for TOF-MRA reconstruction. Undersampled data less than 30 % showed visible image degradation. In conclusion, NESTA method can be used for TOF-MRA undersampled data reconstruction and L1-norm should be a choice for regularization method.

2542.   A simple and practical method to optimize regularization parameters in Compressed Sensing reconstruction of Time-of-flight (TOF) MR angiography
Koji Fujimoto1, Takayuki Yamamoto1, Thai Akasaka1, Tomohisa Okada1, Yasutaka Fushimi1, Akira Yamamoto1, Toshiyuki Tanaka2, Kei Sano2, Masayuki Ohzeki2, and Kaori Togashi1
1Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, Japan, 2Department of Systems Science, Graduate School of Informatics, Kyoto University, Kyoto, Kyoto, Japan

Reports on applying Compressed Sensing (CS) to TOF-MRA is still limited, probably because of difficulty due to a relatively lower SNR, and is hence challenging. In this work, we propose a simple and practical method to select a good regularization parameter applicable to TOF-MRA image reconstruction. We performed CS with 4x accelerated data at 3.0T by the FCSA algorithm with varying weights for Wavelet and Total Variation penalty. Among 6 different quantitative measures, the image selected by the highest SSIM value by using a masked MIP image was considered best by a clinical radiologist’s evaluation.

2543.   Comparison of 2D versus 3D sparse priors in Compressed Sensing reconstruction of Time-of-flight (TOF) MR angiography
Thai Akasaka1, Koji Fujimoto1, Takayuki Yamamoto1, Tomohisa Okada1, Yasutaka Fushimi1, Akira Yamamoto1, Toshiyuki Tanaka2, Kei Sano2, Masayuki Ohzeki2, and Kaori Togashi1
1Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan, 2Kyoto University Graduate School of Informatics, Kyoto, Japan

The application of compressed sensing (CS) to Time-of-Flight MRA is usually 2D-based, although exploitation of 3D sparsity should perform better in principle. We performed CS with 4x accelerated data at 3.0T by the FCSA algorithm in both a 2D and 3D Wavelet and Total Variation reconstruction scheme. Among different results with varying weights for each priors, the best 2D and 3D-based images were subjectively selected. Images were evaluated by two radiologists, and visualization of clinically relevant structures were slightly superior for the best 3D-based image compared with best 2D-based image. Similarity measures were also in agreement with these results.

2544.   Optimization of Flow-Compensation Gradients in SWI and TOF Scans for Acoustic Noise Reduction in MRI
David Manuel Grodzki1, Aurelien F Stalder1, Yutaka Natsuaki2, Julie Roesch3, and Bjoern Heismann1,4
1Magnetic Resonance, Siemens Healthcare, Erlangen, Bavaria, Germany, 2Siemens Healthcare USA, Los Angeles, California, United States, 3Neuroradiology, University of Erlangen, Erlangen, Bavaria, Germany, 4Friedrich-Alexander-University of Erlangen-Nuremberg, Pattern Recognition Lab, Germany

During an MRI scan, the patient is exposed to high acoustic-noise levels caused by fast-switching gradients. By minimizing gradient activity, acoustic-noise can be significantly decreased. For flow-compensation gradients however, optimization of gradients also needs to consider the M1 moments of the gradient events. In this work, we present an automated gradient conversion algorithm that does not only smooth gradient shapes but also saves the M1 moment during flow compensation. Increased noise reduction is demonstrated for TOF and SWI scans, without sacrificing diagnostic image quality.

2545.   Simultaneous assessment of respiration and heart beat on CSF and blood oscillations in near real-time imaging
Joel Daouk1, Roger Bouzerar1,2, and Olivier Baledent1,2
1BioFlow Image, University of Picardie Jules Verne, Amiens, Picardie, France, 2Medical Image Processing, CHU Amiens, Picardie, France

MR vascular images are obtained after the acquisition of several cardiac cycles followed by an average of these measures. In this case, we do not have the true cardiac information and respiratory influence is lost. The aim of the present study was to apply a near real time imaging to follow physiological changes in CSF, arterial and venous flows. Moreover, we expose the principle of an automatic Fourier-based method to extract respiratory and cardiac frequencies in fast MR images and to assess the contribution of the two physiological phenomena to the signal obtained during MR acquisitions in various fluids.

2546.   A Preliminary Study of Self-Gated Rat Cardiac Imaging by Using Wideband MRI Technique
Yi-Hang Tung1, Yun-An Huang2, Edzer L. Wu2, Wan-Ting Zhao2, Tzi-Dar Chiueh2, and Jyh-Horng Chen2
1National Taiwan University, Taipei, Taiwan, Taiwan, 2National Taiwan University, Taiwan, Taiwan

Non-invasive self-gated IntraGate FLASH sequence (IG-FALSH) was used to perform cardiac imaging by reducing motion artifacts. However, IG sequence requires large repetitions to reduce the motion artifact and hence was hard to examine high spatial or temporal resolution cardiac imaging. In this study, we demonstrate the capability of implementing W=2 acceleration Single Carrier Wideband MRI on IG-FLASH sequence. Moreover, by trading time reduction for higher spatial resolution, the fine structures such as valve, papillary muscles and chordae tendineae could be observed more clearly with this new technique.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2547.   First experiences with a Time of Flight (ToF) Camera for marker-less motion tracking within a 7 Tesla MR scanner
Thomas Siegert1, Enrico Reimer1, Roland Müller1, Robert Turner1, Harald Möller1, and Jessica Schulz1
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Sachsen, Germany

Time-of-flight (ToF) cameras have the potential to deliver real-time position information for prospective motion correction without special optical markers like retro-reflective spheres, checkerboard patterns or Moiré markers. In this abstract, we are reporting our initial experiments with a ToF camera within the bore of a 7T MR scanner. The modifications to make the camera MR-compatible as well as residual challenges are described and discussed.

2548.   In vivo 7T MR imaging triggered by phase information obtained from video signals of the human skin
Nicolai Spicher1, Markus Kukuk1, Mark E. Ladd2,3, and Stefan Maderwald2
1University of Applied Sciences and Arts Dortmund, Dortmund, Germany, 2Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany, 3Division of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany

A video of the forehead is used to offer an alternative to contact-based triggering hardware. The video is obtained from a camera installed above the subjects head in a 7T MR bore; triggers are computed in real-time by an algorithm based on phase information of mean pixel intensities. During nonenhanced MR angiography of the lower extremities of one volunteer, triggers from the vendor-provided pulse oximeter and from the algorithm were saved. Results suggest that the video-based approach is principally able to reproduce the triggers obtained by pulse oximetry but suffers in case of the head motion.

2549.   Assessment of marker fixation in prospective motion correction using a multiple marker approach.
Benjamin Knowles1, Thomas Lange1, Aditya Singh2, Michael Herbst2, and Maxim Zaitsev1
1Medical Physics, Univeristy Medical Centre Freiburg, Freiburg, Germany, 2John A Burns School of Medicine, University of Hawaii, Honolulu, Hawaii, United States

For accurate prospective motion correction using markers, the marker must be rigidly coupled to the motion of the imaged object. However, patient comfort and ease of adhesion are important factors, especially in a clinical setting. In this study, dual-marker tracking is used to assess drifts and non-coupled motion of markers adhered to the forehead or nose. This is achieved by tracking the relative pose of the marker compared to a reference marker fixated to a mouthpiece, assumed perfectly coupled to the skull. Drifts were measured to be small, but squinting causes large decoupling of marker motion with the skull.

2550.   The Necessity of Coil Sensitivity and Gradient Non-Linearity Distortion Corrections in Prospective Motion Correction
Uten Yarach1, Daniel Stucht1, Frank Godenschweger1, and Oliver Speck1
1Department of Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Sachsen-Anhalt, Germany

Patient motion during an MRI of the brain can result in non-diagnostic image quality. Even with perfect prospective motion tracking and correction, the varying coil sensitivity and gradient non-linearity can cause significant artifacts that cannot be corrected prospectively. Recently, a model-based MR image reconstruction via iterative solver was employed to minimize the sensitivity misalignment due to coil or physiological movement. In this study, we extended the mentioned model by gradient warp correction to reconstruct the prospective Mo-Co MR data. The result shows the improvement that is free from both artifacts after a few iterations of the proposed technique.

2551.   Contribution of FOV Updating and Reacquisition to Estimates of Cortical Surface Measures in PROMO MPRAGE
Joelle E Sarlls1, Francois Lalonde2, Dan Rettmann3, Ajit Shankaranarayanan4, Vinai Roopchansingh5, and S. Lalith Talagala1
1NMRF/NINDS, National Institues of Health, Bethesda, MD, United States, 2NIMH, National Institutes of Health, Bethesda, MD, United States, 3GE Healthcare, Rochester, NY, United States, 4GE Healthcare, Menlo Park, CA, United States, 5FMIRF/NIMH, National Institutes of Health, Bethesda, MD, United States

Prospective motion correction techniques, such as PROMO, are increasingly available to improve the quality of high resolution anatomical MRI. PROMO consists of two parts, FOV updating and reacquisition of k-space data when excessive motion is detected. Reacquisition of data adds extra scan time, which is undesirable for pediatric or patient studies where scan time is limited. The contribution of each part of PROMO in reducing errors of cortical surface reconstruction measures was investigated. This study shows that utilizing either part of PROMO improves accuracy of measures, but full PROMO provides the greatest accuracy.

2552.   Real-Time Dynamic Prediction of Motion during Prospective Motion Correction Helps Reduce Errors Caused by Fast Motions and Delayed Motion Measurements
Burak Erem1,2, Onur Afacan1,2, Ali Gholipour1,2, and Simon K Warfield1,2
1Department of Radiology, Boston Children's Hospital, Boston, MA, United States, 2Harvard Medical School, Boston, MA, United States

Prospective motion correction of MRI steers the imaging field of view (FOV) to image as if the subject was not moving. All existing prospective motion correction techniques to date will perform the action of steering the FOV using motion measurements made in the past, because all motion measurements are available after some delay. Moreover, all of these existing techniques assume that this delay is infinitesimal. However, recent work demonstrates that this assumption is wrong and leads to poor motion compensation, especially when motions are rapid. Prediction of motion parameters shortly into the future has been proposed to reduce errors due to measurement delays and improve motion compensation. Here we assess how dynamic prediction compares to PROMO and static motion estimation.

2553.   Comparing 1.5T vs. 7T phase contrast MRI for measuring brain tissue pulsation
Nils Noorman1, Fredy Visser1,2, Peter R. Luijten1, and Jaco J.M. Zwanenburg1
1Department of Radiology, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, 2Philips Healthcare, Best, Netherlands

Cardiac-driven volumetric strain pulsations in the brain are small, but relevant for normal physiology and disease. These strain rates can be obtained from phase contrast MRI with low encoding gradients, but the corresponding long TEs reduce the SNR. This work determines the optimal TE for phase contrast MRI with very low encoding velocities (< 1 cm/s) and the potential gain in SNR at 7T (with shorter T2*) compared to 1.5T, in 6 subjects. Despite signal attenuation due to shorter T2* at 7T, we obtained a 5-fold increase in SNR between 1.5T and 7T.

2554.   Inter-scan motion artefacts in quantitative R1 mapping require correction of coil sensitivity profiles
Daniel Papp1, Martina F. Callaghan1, Craig Buckley2, Heiko Meyer3, and Nikolaus Weiskopf1
1Wellcome Trust Centre For Neuroimaging, UCL Institute of Neurology, London, United Kingdom, 2SIEMENS PLC (Healthcare Division), United Kingdom, 3SIEMENS Healthcare AG, Germany

Quantitative imaging methods often rely on multiple scans and are therefore susceptible to inter-scan motion. In the presence of rapidly varying coil sensitivities, volunteer movement between scans will result in position-specific signal intensity modulation, which cannot be corrected for by rigid body motion correction and leads to error in the quantitative maps. Here we demonstrate the impact of this artefact on quantitative R1 maps and propose and validate a correction method based on dynamically updating coil-sensitivity maps. Our approach can be readily implemented and generalized to other multi-scan acquisitions.

2555.   Prospective Motion Correction (PROMO) enabled MP2RAGE for multi-contrast high-resolution brain imaging
Alexandru V. Avram1, Joelle E. Sarlls2, Cibu P. Thomas1,3, Vinai Roopchansingh4, Dan Rettmann5, Ajit Shankaranarayanan6, and Peter J. Basser1
1Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, MD, United States, 2NINDS, National Institutes of Health, Bethesda, MD, United States, 3The Henry Jackson Foundation, Bethes, MD, United States, 4NIMH/Functional MRI Facility, National Institutes of Health, Bethesda, MD, United States, 5ASL, GE Healthcare, Rochester, MN, United States, 6ASL, GE Healthcare, Menlo Park, CA, United States

Images with different tissue contrasts acquired with the MP2RAGE pulse sequence, although inherently co-registered, can suffer from imaging artifacts due to subject motion especially in studies involving non-compliant subjects such as pediatric or elderly patient populations. We implement a PROMO-enabled 3D MP2RAGE pulse sequence, evaluate its ability to correct for subject motion, and illustrate how it can be used for multi-contrast high-resolution tissue visualization and characterization in moving subject at 3T.

2556.   Retrospective rigid motion correction of undersampled MRI data
Alexander Loktyushin1, Maryna Babayeva2,3, Daniel Gallichan4, Gunnar Krueger2,3, Klaus Scheffler5,6, and Tobias Kober2,3
1Empirical Inference, Max Planck Institute for Intelligent Systems, Tübingen, Germany, 2Siemens ACIT - CHUV Radiology, Siemens Healthcare IM BM PI, & Department of Radiology, University Hospital (CHUV), Lausanne, Switzerland, 3LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 4CIBM, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 5High-Field Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 6Department for Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany

The present study combines retrospective motion correction and GRAPPA reconstruction. We propose a technique that performs several alternations of GRAPPA interpolation and motion correction steps, suppressing the artifacts caused by motion over the course of the optimization. Motion parameters are estimated directly from the data with the aid of free induction decay navigators. The proposed algorithm does not require a priori knowledge of coil sensitivity profiles and can be applied retrospectively to data acquired with generic sequences such as MP-RAGE. The algorithm was tested on motion corrupted brain images of healthy volunteers, performing controlled head movement during the scan. Results demonstrate a significant improvement in image quality.

2557.   Parallel imaging for motion correction in neonatal brain MR reconstruction
Lucilio Cordero-Grande1,2, Emer Hughes1,2, Rui Pedro A. G. Teixeira1,2, and Joseph V. Hajnal1,2
1Centre for the Developing Brain, King's College London, London, London, United Kingdom, 2Division of Imaging Sciences and Biomedical Engineering, King's College London, London, London, United Kingdom

A method is presented for retrospective rigid motion correction in multi-shot brain neonatal MR acquisitions. It is based on using parallel imaging so that the joint motion correction and image reconstruction problem becomes overconstrained. Additionally, no blurring is introduced in the presence of motion as no regridding is applied. The procedure has proven to significantly enhance the quality of neonatal brain images by decreasing the presence of confounding artifacts, improving the contrast, better resolving structures, and enabling the emergence of new anatomical details hindered by motion.

2558.   The Correction of Motion-Induced Coil Sensitivity Miscalibration in Parallel Imaging with Prospective Motion Correction
Uten Yarach1, Daniel Stucht1, Frank Godenschweger1, and Oliver Speck1
1Department of Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Sachsen-Anhalt, Germany

Unlike the retrospective technique, prospective motion correction (Mo-Co) can avoid spin history effects as well as k-space inconsistencies. However, in case of large motion during multi-coil acquisition, the coil sensitivities that change relative to the object are one of the most considerable residual artifact causes in prospective Mo-Co. In this study, we investigate the effect of coil sensitivity variations on parallel prospective Mo-Co data if only initial coil sensitivities are known. We also show that if a small number of central k-space can be acquired when motion occurred, they are sufficient for estimating coil sensitivities to correct abovementioned artifact.

Paul Wighton1,2, Matthew Dylan Tisdall1,2, Erez Nevo3, and André Dylan van der Kouwe1
1Martinos Center for Biomedical Imaging, MGH, Charlestown, MA, United States, 2Harvard Medical School, Boston, MA, United States, 3Robin Medical, Baltimore, MD, United States

Several external tracking prospective motion correction systems require a marker or sensor be affixed to the subject's head. These systems assume that the sensor moves rigidly with respect to the subject's head. When this assumption is violated, performance of the system degrades. This abstract investigates the incorporation of position estimates from imaging data to recover from non-rigid sensor affixation.

Prospective motion correction of DW 3D-MS EPI using collapsed FatNav (cFatNav)
Mathias Engström1,2, Enrico Avventi1,2, Magnus Mårtensson2,3, Ola Norbeck1, and Stefan Skare1,2
1Dept. of Neuroradiology, Karolinska University Hospital, Stockholm, Stockholm, Sweden, 2Dept. of Clinical Neuroscience, Karolinska Institutet, Stockholm, Stockholm, Sweden, 3EMEA Research and Collaboration, GE Applied Science Laboratory, GE Healthcare, Stockholm, Sweden

Here we suggest combining collapsed fat navigation (cFatNav) with diffusion-weighted 3D multi-slab echo-planar imaging (DW 3D-MS EPI) for prospective motion correction. 3D rigid body motion was registered via three orthogonal EPI readouts, which depicted projections of the subcutaneous fat. With a readout block duration of 6.4 ms (R = 8) motion updates were received at a ~5-10 Hz update rate, at a 5% scan time increase.

2561.   Effect of Hand Feedback Visualization on Head Motion During fMRI of Neuropsychological Testing
Mahta Karimpoor1,2, Zahra Faraji-Dana1,2, and Simon James Graham1,2
1Physical Scienses, Sunnybrook Research Institute, Toronto, Ontario, Canada, 2Medical Biophysics, University of Toronto, Toronto, Ontario, Canada

An fMRI-compatible computerized tablet system has been previously developed in house to be used for complex Neuropsychological testing such as writing. The tablet did not include visual feedback of hand position (VFHP), a human factors component that may be important for fMRI of certain patient populations. Because the user is lying in the magnet bore, they cannot view their hand during this process and must rely on their sense of proprioception. A real-time system was thus developed to provide VFHP and integrated with the tablet in an augmented reality display. Attempting to visualize the hand position during performing such complex motor movements may induce excess subject’s head motion. We assessed the influence of VFHP on head motion and the associated brain activity involving a set of handwriting tasks in young healthy adults. ​

2562.   An automatic EEG-assisted retrospective motion correction for fMRI (aE-REMCOR)
Chung-Ki Wong1, Vadim Zotev1, Han Yuan1, Masaya Misaki1, Raquel Phillips1, Qingfei Luo1, and Jerzy Bodurka1,2
1Laureate Institute for Brain Research, Tulsa, Oklahoma, United States, 2College of Engineering, University of Oklahoma, Norman, Oklahoma, United States

Head motion during fMRI impairs data quality. EEG-assisted retrospective motion correction (E-REMCOR), which utilizes EEG data to correct for head movements in fMRI on a slice-by-slice basis, was shown to be capable of substantially removing movement in fMRI datasets. To enhance E-REMCOR usability, especially for the rapidly growing interest in concurrent EEG and fMRI measurements, we developed automatic E-REMCOR (aE-REMCOR) for head motion correction. aE-REMCOR was applied to 305 fMRI scans at 3 Tesla. The average change of TSNR over the brain goes up to 24%. The largest 10 percent of TSNR improvement reaches over 43%.

2563.   Six-degree of Freedom Retrospective Motion Correction using Spherical Navigator Echoes (SNAV)
Patricia Johnson1,2, Junmin Liu1, Trevor Wade1, and Maria Drangova1,2
1Imaging Research Laboratories, Robarts Research Institute, London, Ontario, Canada, 2Dept. of Medical Biophysics, Schulich School of Medicine & Dentistry, Western University, London, Ontario, Canada

Spherical navigator echo (SNAV) techniques are promising for measuring rigid body motion in all 6 degrees of freedom. In this abstract we demonstrate – for the first time - the accuracy of retrospective preRot-SNAV-correction of motion by interleaving the SNAVs within a 3D imaging pulse sequence (efgre-SNAV). We have performed a preliminary evaluation of this sequence and determined that the interleaved SNAVs perform comparably to stand alone SNAVs in measurements of rotation and translations; they agree within 1.0° and 0.43mm. We have also demonstrated successful retrospective correction of a phantom image.

2564.   Motion Correction for Variable Density Spiral MRI Using Sampling Overlap as Inherent Navigators
Yilong Liu1,2, Xiaodong Ma2, Hua Guo2, and Ed X. Wu1,3
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, Hong Kong, China, 2Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, Beijing, China, 3Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, Hong Kong, China

Variable density spiral (VDS) sampling is advantageous for fast imaging, it also has potential in motion correction due to repeated sampling of each interleaf around the k-space center. However, for VDS, the full sampling area of each interleaf may be too small for accurate motion estimation. In this work, the navigation region is defined to cover more than the full sampling area, and we use SPIRiT to further improve navigation region. Results show that our proposed method can significantly remove the artifacts in both simulation and in vivo studies.

Wednesday 3 June 2015
Exhibition Hall 16:00 - 18:00

2565.   2D Diaphragm navigation with rapid gradient echo images: validation at 3T and application at 7T
Aaron T Hess1, Andre JW van der Kouwe2,3, Matthew Dylan Tisdall2, Stefan Neubauer1, and Matthew D Robson1
1Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Oxford, Ox, United Kingdom, 2Radiology, Harvard Medical School, Boston, MA, United States, 3Martinos Center, Massachusetts General Hospital, Boston, MA, United States

A novel 2D rapid gradient echo navigator is proposed for real time diaphragm navigation. At ultrahigh fields (>3T) traditional diaphragm navigators are challenging due to either large B0 gradients, limited B1+ or SAR demands. The proposed gradient echo navigator requires minimum B1+ and takes ~70 ms to acquire. The new 2D navigator is compared to a product 1D cross paired navigator at 3T, and is demonstrated to be robust and reliable at 7T. The contrast to noise is of the new 2D navigator is similar to that of the cross paired navigator, with an improved diaphragm edge sharpness.

2566.   Comparison of breath-holding and respiratory gating T2* mapping in the heart and liver for thalassemia major patients
Xiaodong Chen1,2, Zuoquan Zhang3, Qihua Yang1, Zebin Luo2, Ziliang Cheng1, Jiaji Mao1, Queenie Chan4, Hua Guo5, and Biling Liang1
1Sun Yat-Sen Memorial Hospital, Guangzhou, Guangdong, China, 2Affiliated hospital of Guangdong Medical College, Zhanjiang, Guangdong, China, 3The Fifth Affiliated Hospital of Sun Yat-Sen University, Guangdong, China, 4Philips Healthcare, Hong Kong, China, 5Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China

With the development of MRI techniques, T2* mapping is becoming the routine examination for evaluation of the iron level of the heart and liver in TM patients. Generally, the common T2* sequence is scanned with one breath hold and less attention is paid to motion artifact reduction because most adults can suspend respiration on command. However, as the recommended age to start the first cardiac MRI screening in TM patients has become younger, more and more children with TM will get T2* examination and most of them are generally less able to suspend respiration. In this study, We optimized a technique of T2* respiratory gating, developed and tested the use of respiratory gating to decrease motion artifacts in pediatric heart and liver T2* MRI examinations. From the preliminary study it suggests that, comparing to the results of breath-hold T2* scanning, the accuracy and reproducibility of respiratory gating method are good enough to be used in the clinical practice.

2567.   Continuous adaptive sampling of k-space from real-time physiologic feedback in MRI
Francisco Contijoch1, Yuchi Han1, Michael Hansen2, Peter Kellman2, Gene Gualtieri3, Mark A Elliott1, Sebastian Berisha1, James J Pilla1, Robert C Gorman1, and Walter RT Witschey1
1University of Pennsylvania, Philadelphia, PA, United States, 2National Institute of Health, Bethesda, Maryland, United States, 3Drexel University, Philadelphia, PA, United States

Inconsistent motion during a cine MRI can result in image artifacts, loss of signal-to-noise ratio, or poor representation of the underlying physiology because the scan does not always respond correctly or quickly, to changes in physiology. We proposed an adaptive real-time k-space sampling trajectory (ARKS) to respond to a physiologic feedback signal to reduce motion effects and ensure sampling uniformity. The most recent signals from an ECG waveform of normal subjects and patients were continuously matched to the previous signal history, new radial k-space locations were determined, and these MR signals were combined using multi-shot or single-shot radial acquisition schemes.

2568.   Using Optical Flow to Estimate Displacement Between 3D Navigators in Coronary Angiography
Nicholas Dwork1, Daniel O'Connor2, Nii Okai Addy1, Reeve Ingle1, John Pauly1, and Dwight Nishimura1
1Electrical Engineering, Stanford University, Stanford, CA, United States, 2Mathematics, University of California, Los Angeles, CA, United States

3D image based navigators (iNAVs) provide an opportunity to measure whole volume non-rigid beat-to-beat motion of the heart. In this work, we show that we can use optical flow to estimate motion from 3D iNAVs. The Alternating Direction Method of Multipliers is used to minimize the optical flow cost function, where total variation regularization has been imposed.

2569.   Estimating 3D deformable motion from a series of fast 2D MRI images with CLARET
Jason Brown1, Cihat Eldeniz1, Wolfgang Rehwald2, Brian Dale3, Hongyu An1, and David Lalush1
1Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill and North Carolina State University, Chapel Hill, NC, United States, 2Siemens Healthcare, Malvern, PA, United States, 3Siemens Healthcare, Cary, NC, United States

In this application, we effectively estimated patient-specific 3D deformable motion from fast 2D MRI images. CLARET is an image registration method that has been used to relate a set of 2D images to a corresponding set of 3D images. Using CLARET to predict the 3D motion of a subject from a set of 2D projection images has the potential to be used in MRI imaging of dynamic processes. The results of the registration give a motion estimate that reduced alignment error mean and variance in 2D frames. We concluded that CLARET can be used effectively in an MRI setting.

2570.   3D FFE PROPELLER Free-Breathing Abdominal Imaging
Yuchou Chang1, Dallas C Turley1, and James G Pipe1
1Imaging Research, Barrow Neurological Institute, Phoenix, Arizona, United States

A PROPELLER based 3D Fast Field Echo (FFE) sequence and reconstruction method for free-breathing data acquisition in dynamic abdominal imaging is studied. The proposed method acquires 3D blades dynamically depending on the physiology property. Two weighting functions are proposed to preferentially use the preferred data in the gridding process and reconstruction. Experimental results demonstrate that the proposed method is able to reduce respiration artifacts and sharpen images.

2571.   3D T2w-MRI using a Magnetization-Prepared Golden Angle Radial Sequence with Motion-Corrected ESPIRiT Reconstruction
Isabel Dregely1, Fei Han1, Ziwu Zhou1, Kyung Sung1, Peng Hu1, and Holden H Wu1
1Radiological Sciences, University of California Los Angeles, Los Angeles, CA, United States

T2-weighted MRI is the central component for body cancer MRI protocols. In clinical routine T2-w MRI is often restricted to 2D multi-slice acquisitions, because 3D acquisition times are relatively long and achieving robustly good image quality is often hindered by motion corruption. The purpose of our work was to develop a 3D T2-w motion robust imaging sequence using a magnetization-prepared radial imaging technique with self-navigating motion correction. We found that bulk and respiratory motion could be reliably detected using the self-navigating radial sequence. The golden angle view ordering allowed for flexible retrospective image reconstruction, allowing removing motion-corrupted views. ESPIRiT reconstruction yielded good image quality even in under-sampled data sets.

2572.   3D Free-breathing Abdominal MRI using Robust Navigator Processing with Coil Clustering
Tao Zhang1,2, Joseph Y Cheng1,2, Yuxin Chen2, John M Pauly2, and Shreyas S Vasanawala1
1Radiology, Stanford University, Stanford, CA, United States, 2Electrical Engineering, Stanford University, Stanford, CA, United States

Abdominal MRI is often limited by respiratory motion. Some acquisition trajectories, such as modified Cartesian and radial, can provide self-navigating signals during data acquisition. This enables retrospective motion compensation (MC). With phased array coils, navigators can be acquired for each coil element. Since navigators from different coil elements track motion in local regions that can vary significantly, averaging navigators from all coils sometimes yields inaccurate respiration estimation, and therefore ineffective MC. Here, a robust navigator processing method using coil clustering is described, implemented, and validated. The proposed method automatically selects the appropriate navigators for MC from coil arrays.

2573.   Interleaved versus grouped viewsharing in 3D DCE-DIXON of the abdomen: sensitivity to motion artifacts
Christine Nabuurs1, Gabriele Beck1, Silke Hey1, and Marko Ivancevic2
1Clinical Excellence, Philips Healthcare, Best, NB, Netherlands, 2Clinical Science, Philips Healthcare, Best, NB, Netherlands

Inconsistent breathholds during 3D dynamic DCE MR imaging of the abdomen are a major cause of motion artifacts. In this study we compared motion sensitivity of dynamic 3D-DIXON FFE to end-breath hold motion between interleaved1 and grouped2 peripheral ky-kz viewsharing. The acquisition of the complete peripheral kykz at the end of the breath hold makes gouped viewsharing less sensitive to breathing induced motion at the end of the acquisition. It also allows for a higher temporal resolution in the early dynamics, which is especially beneficial for capturing early arterial phases of abdominal MR imaging.

2574.   Dynamic Reacquisition for Respiratory Gated, Constant TR 2D multi-slice MRI
Paul Kinchesh1, Philip D Allen1, John S Beech1, Emmanouil Fokas1, Stuart Gilchrist1, Veerle Kersemans1, Ruth Muschel1, and Sean C Smart1
1Department of Oncology, University of Oxford, Oxford, United Kingdom

Constant T1 weighting is difficult to achieve in 2D multi-slice MRI when used with respiratory gating or triggering. Long term averaging and retrospective gating have been used to ameliorate this, but at the expense of significantly extended scan time. This report describes a new technique that enables respiratory-gated 2D multi-slice MRI to operate at a constant, short TR (TR<3T1). The method is maximally efficient as data are acquired throughout the entire respiratory interval, and are discarded only when motions are present. The method is compatible with the addition of cardiac triggering for TR>5T1 and is demonstrated in the mouse abdomen.

2575.   Flow Artifact Suppression in Subtractionless First-Pass Peripheral Angiography Based on Vessel Tree Segmentation
Holger Eggers1, Rafael Wiemker1, Peter Börnert1, and Tim Leiner2
1Philips Research, Hamburg, Germany, 2Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands

Flow compensation is usually not applied in first-pass peripheral angiography due to stringent scan time constraints. This entails the occurrence of flow artifacts, which are potentially aggravated by the recently proposed use of Dixon- instead of subtraction-based background suppression in this application. Therefore, the effect of flow artifacts inside the vessels on the water-fat separation is studied in the present work and illustrated by examples. Moreover, an approach is proposed that relies on a vessel tree segmentation to provide a comprehensive suppression of flow artifacts in subtractionless first-pass peripheral angiography.

2576.   Quantification of Fetal Motion Tracked with Volumetric Navigator MRI Acquisitions
Patrick McDaniel1, Borjan Gagoski2, M. Dylan Tisdall3,4, André J. W. van der Kouwe3,4, P. Ellen Grant2,4, Lawrence Wald3,4, and Elfar Adalsteinsson1,5
1Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, 2Fetal-Neonatal Neuroimaging and Developmental Science Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States, 3Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States,4Radiology, Massachusetts General Hopsital, Boston, MA, United States, 5Health Sciences and Technology, Harvard-MIT, Cambridge, MA, United States

The ability to perform higher quality fetal brain imaging would be facilitated by navigators that track fetal head motion. We demonstrate the feasibility of measuring this motion along six degrees of freedom using 3D volumetric navigator (vNav) acquisitions. A series of vNavs is acquired over time, and a fetal head ROI is identified within the first 3D volume to serve as a template for rigid-body registration of subsequent 3D images. Registrations are performed with FSL FLIRT, producing affine transformation matrices which provide quantitative measurements of fetal head displacement and rotation.

2577.   Motion Detection and Correction Using Non-marker-attached Optical System during MRI Scanning
Jin Liu1, Huijun Chen2, Zechen Zhou2, Jinnan Wang3, and Chun Yuan1
1University of Washington, Seattle, WA, United States, 2Tsinghua University, Beijing, China, 3Philips Research North America, NY, United States

Motion artifact is a major challenge affecting the image quality of MRI. Navigator based motion correction usually need extra scan time with sequence dependence, while existing optical motion tracking systems need markers for accurate motion measurements. Therefore, we proposed a non-marker-attached optical motion tracking system based on structured light to measure the absolute distance, which has the merits of high accuracy, sequence independence and no patient interaction. This study demonstrated that the motion can be accurately identified with the proposed method and then corrected retrospectively by deleting and resynthesizing the corresponding corrupted k-space lines.

2578.   In-vivo MR-derived non-rigid motion correction of simultaneously acquired PET
Thomas Küstner1,2, Christian Würslin1, Sergios Gatidis1, Petros Martirosian3, Nina Schwenzer1, Bin Yang2, and Holger Schmidt1
1Department of Radiology, University Hospital of Tübingen, Tübingen, Baden-Württemberg, Germany, 2Institute of Signal Processing and System Theory, University of Stuttgart, Stuttgart, Baden-Württemberg, Germany, 3Diagnostic and Interventional Radiology, University Hospital of Tübingen, Tübingen, Baden-Württemberg, Germany

In the field of oncology, simultaneous PET/MR scanners offer a great potential for improving diagnostic accuracy. However for accurate lesion detection and quantification, the induced motion artifacts in the PET image originating from a long free-breathing acquisition have to be compensated. The simultaneous acquisition allows performing a MR-based non-rigid motion correction of the PET data. Therefore it is essential to acquire a 4D MR image as accurate and fast as possible under free-breathing conditions. We propose a clinical feasible motion correction setup which uses a Compressed Sensing acquisition. In-vivo patient data substantiates the diagnostic improvement of the motion corrected PET.

2579.   Motion Compensation (MoCo) for Simultaneous PET/MR Based on Strongly Undersampled Radial MR Data - A Simulation Study
Christopher M Rank1, Thorsten Heußer1, Marcus Brehm1, and Marc Kachelrieß1
1Division of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany

We propose a new method for PET/MR respiratory Motion Compensation (MoCo), which is based on strongly undersampled MR data. In our simulation study, we used a 3D encoded radial stack-of-stars sampling scheme with 160 radial spokes per partition and an acquisition time of 38 s. Based on iteratively reconstructed 4D MR images, high-fidelity motion vector fields were estimated and MoCo 4D PET images of a simulated breathing thorax were reconstructed. Evaluation of 8 artificial hot lesions in the lungs and upper abdomen showed a significant visual as well as a quantitative improvement in terms of SUVmean values of MoCo 4D PET images compared to 3D and 4D gated reconstructions.