ISMRM 21st Annual Meeting & Exhibition 20-26 April 2013 Salt Lake City, Utah, USA

2044 -2076 Diffusion Acquisition
2077 -2094 Diffusion: Noise, Artifacts & Phantoms
2095 -2116 Diffusion: Pre-Clinical & Clinical Applications
2117 -2143 Fibre PDF's & Tractography
2144 -2193 Arterial Spin Labeling
2194 -2226 Perfusion & Permeability

Monday, 22 April 2013 (16:30-18:30) Exhibition Hall
Diffusion Acquisition

2044.   Fat Suppressive and Susceptibility Tolerant PINS Pulses for Multi-Band Diffusion Weighted EPI
Eric Aboussouan1, Rafael O’Halloran1, Anh Tu Van1, Samantha J. Holdsworth1, William A. Grissom2, and Roland Bammer1
1Radiology, Stanford University, Stanford, California, United States, 2Biomedical Engineering, Vanderbilt University, Nashville, Tennesse, United States

Multi-band acquisitions make diffusion imaging with full brain coverage faster and more SNR-efficient by simultaneously acquiring multiple slices with limited g-factor penalty. To do so, special RF pulses must be employed. PINS pulses excite multiple slices simultaneously with limited power deposition and can additionally be designed to be inherently fat suppressive. In this work, we present and compare two multiband excitation and refocusing schemes for Diffusion Weighted EPI (DW-EPI). The first method performs lipid suppression by shifting the fat slice in opposite directions during the excitation and refocusing steps. The second method reduces susceptibility artifacts by matching the time-averages of the slice selection gradients of the excitation and refocusing pulses.

2045.   SAR Efficient Simultaneous Multislice Diffusion Weighted Imaging at 7T Using PINS RF Pulses
Markus Barth1,2, Peter J. Koopmans1,2, Rasim Boyacioglu1, Jennifer Bersch1, and David G. Norris1,2
1Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, Netherlands, 2Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany

Simultaneous multislice (SMS) imaging is an efficient way to speed up multislice 2D acquisitions by exciting several slices simultaneously and reconstructing them via parallel imaging algorithms. Specifically, diffusion weighted imaging (DWI) profits largely when this technique is used, however, at high field strengths conventional multiband pulses lead to high SAR. We show that by using RF pulses where the power is independent of the number of slices (PINS), SAR and amplitude constraints can be resolved even for double-refocused spin-echo DWI at 7 Tesla leading to short acquisition times (< 3 minutes for 60 diffusion directions).

2046.   Compressive Diffusion MRI – Part 2: Performance Evaluation Via Low-Rank Model
Hao Gao1,2, Longchuan Li3, and Xiaoping P. Hu3
1Department of Mathematics and Computer Science, Emory University, Atlanta, Georgia, United States, 2Department of Radiology and Imaging Sciences, Emory University, Atlanta, Georgia, United States,3Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, Georgia, United States

In another submitted abstract “Compressive Diffusion MRI – Part 1: Why Low-Rank?”, we compared several sparsity models and found that the low-rank (LR) model is the most suitable for diffusion MRI. In this abstract we retrospectively explore compressive MRI in the context of diffusion MRI via LR. The results suggest that LR is able to accurately reconstruct the diffusion MR images from highly undersampled k-space, in terms of both the image quality and the angular differences in the principal and secondary diffusion orientations.

How to Make Sure You Are Using the Correct Gradient Orientations in Your Diffusion MRI Study
Ben Jeurissen1, Alexander Leemans2, and Jan Sijbers1
1iMinds-Vision Lab, University of Antwerp, Antwerp, Belgium, 2Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands

Ensuring one is using the correct gradient table in a diffusion MRI study can be a challenging task. Different scanners, file formats and processing tools use different coordinate frame conventions. This can lead to gradient orientations containing an angulation error, which might go unnoticed when small. In this work, we propose a fast and reliable tool to automatically align the gradient table with the corresponding diffusion weighted images, using a metric based on whole brain tractography. Simulations show that sub-degree accuracy and precision is achieved. This tool will be made available during the meeting as a web application.

2048.   Diffusion Signal Decomposition Using Periodical Sampling in Gradient Direction Domain and Fourier Approximation
Farshid Sepehrband1, Jeiran Choupan1, Nyoman Dana Kurniawan1, David C. Reutens1, and Zhengyi Yang2
1Centre for Advanced Imaging, The University of Queensland, Brisbane, QLD, Australia, 2school of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD, Australia

In this work we proposed a novel data driven approach to decompose restricted diffusion from diffusion signal, and validated it using ex-vivo mouse brain tractography. To achieve this goal, first, we impose a periodic spiral sampling in gradient direction domain. Then, we applied low pass filter based on finding the optimal cut-off frequency to decompose the diffusion signal. We assume that restricted diffusion is sensitive to sampling orientation, while free diffusion and noise are orientationally independent. Therefore, restricted diffusion contributes in the low frequency parts of diffusion signal, while free diffusion and noise contribute in high frequencies.

Periodic Sampling in the Gradient Direction Domain Facilitates Noise Reduction in Diffusion Weighted Imaging
Farshid Sepehrband1, Jeiran Choupan1, Viktor Vegh1, Quang M. Tieng1, David C. Reutens1, and Zhengyi Yang2
1Centre for Advanced Imaging, The University of Queensland, Brisbane, Queensland, Australia, 2School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Queensland, Australia

We have proposed a new sampling scheme for Higher Angular Resolution Diffusion Imaging. The scheme is based on sampling the diffusion gradient directions periodically in a spiral over the unit sphere. Diffusion signal acquired with this scheme inherits the periodicity of the sampling, which brings post-processing opportunities for diffusion MRI data, such as denoising, compressed sensing and tractography. Here we have demonstrated its effect on signal-to-noise improvement.

2050.   Ordering of Multiple Diffusion Gradient Directions for High Resolution ADC Maps Using Golden Angle
Hyunseok Seo1, Yeji Han1, and HyunWook Park1
1Electrical Engineering, KAIST, Daejeon, Korea

This abstract proposes a diffusion weighted-imaging method containing various directional diffusion information in an imaging sequence using radial trajectories. The order of diffusion gradient directions is also proposed to reduce artifacts caused by the anisotropic diffusion properties in the ADC map. Computer simulations were performed to evaluate the proposed method. MR experiment results from phantom and in vivo brain studies show that the proposed method is more accurate and faster than conventional methods. Another merit of the proposed method was also verified through the high-resolution ADC map.

2051.   Optimized Twice-Refocused Adiabatic Spin Echo Sequence for Diffusion Weighted Imaging of Humans at 7T
Priti Balchandani1,2 and Deqiang Qiu2
1Radiology, Mount Sinai School of Medicine, New York, NY, United States, 2Radiology, Stanford University, Stanford, CA, United States

Diffusion weighted imaging (DWI) at higher field strengths, such as 7 Tesla, may benefit from increased signal-to-noise ratio but suffers from susceptibility to B1-inhomogeneity. This effect is particularly pronounced when using a twice-refocused spin echo DWI sequence to mitigate eddy current effects. We have employed the adiabatic SLR algorithm for RF pulse design to design optimized B1-insensitive 180° RF pulses and used them to replace the standard 180° pulses in a twice-refocused spin echo DWI sequence. We show improved diffusion weighted images of the human brain at 7T with more uniform SNR when using this method when compared to the standard non-adiabatic approach.

2052.   An in vivo Investigation Into the Potential Benefit of High-Field MR for Diffusion Imaging
Joelle E. Sarlls1 and S Lalith Talagala1
1NINDS/NMR Center, National Institutes of Health, Bethesda, MD, United States

It is still unclear if typical diffusion-weighted imaging (DW) will benefit from 7T. At higher field there is an increase in magnetization, yet T2-relaxation is shortened, limiting the utility of DWI due to the neccesarily long echo times. Previous studies comparing SNR for DWI at 7T and 3T used significantly different scan parameters and receiver coils. In this study, we compare the SNR of white matter regions, in vivo, for DWI relevent echo times at 7T and 3T using identical scan parameters and comparable receive coils. Our data shows that SNR is greater at 7T for all echo times investigated.

2053.   Noise Reduction in Accelerated Diffusion Spectrum Imaging Through Integration of SENSE Reconstruction Into Joint Reconstruction in Combination with Q-Space Compressed Sensing
Vladimir Golkov1,2, Tim Sprenger1,3, Marion I. Menzel1, Ek T. Tan4, Kevin F. King5, Christopher J. Hardy4, Luca Marinelli4, Daniel Cremers2, and Jonathan I. Sperl1
1GE Global Research, Garching n. Munich, Bavaria, Germany, 2Department of Computer Science, Technical University Munich, Garching n. Munich, Bavaria, Germany, 3IMETUM, Technical University Munich, Garching n. Munich, Bavaria, Germany, 4GE Global Research, Niskayuna, NY, United States, 5GE Healthcare, Waukesha, WI, United States

Sensitivity encoding (SENSE) reconstruction of diffusion weighted images (DWIs) in diffusion MRI is usually done independently for each DWI, without exploiting structural correlations between the DWIs. In this work, SENSE is incorporated into a joint reconstruction framework which models the prior knowledge of common smooth regions and edges in the DWIs. Image quality is improved in comparison to SENSE reconstruction, and even more so in combination with q-space compressed sensing.

2054.   Phase Sensitive Reconstruction in Diffusion Spectrum Imaging Enabling Velocity Encoding and Unbiased Noise Distribution
Jonathan I. Sperl1, Ek T. Tan2, Tim Sprenger1,3, Vladimir Golkov1,3, Kevin F. King4, Christopher J. Hardy2, Luca Marinelli2, and Marion I. Menzel1
1GE Global Research, Garching, Germany, 2GE Global Research, Niskayuna, NY, United States, 3Technical University Munich, Garching, Germany, 4GE Healthcare, Waukesha, WI, United States

Standard diffusion MRI data processing is based on the magnitude of the data, while the phase is neglected. However, valuable information about coherent motion like flow or pulsatility is encoded in the phase. Moreover, by separating the phase information from the data, subsequent processing like tensor fitting or fiber tracking can be done based on the real part of the data avoiding the bias introduced by the Rician noise distribution of the magnitude data. This work presents a robust workflow for a phase sensitive reconstruction of DSI data allowing for the extraction of velocity components and bias-free diffusion information.

2055.   Full Optimization of Multi-Shell Diffusion Acquisition Schemes for Advanced Microstructural Imaging
Silvia De Santis1, Yaniv Assaf2, and Derek K. Jones1
1CUBRIC Cardiff University, Cardiff, United Kingdom, 2Department of Neurobiology, Tel Aviv University, Tel Aviv, Israel

A comprehensive optimisation of the experimental acquisition scheme for advanced microstructural imaging is developed, optimising and comparing different approaches reported in the literature though both Monte-Carlo simulations and in vivo acquisitions. As a result, an optimised protocol for multi-shells acquisitions is proposed, that balances scan duration with accuracy/precision on the estimated parameters, needing only a 12 minutes acquisition for whole-brain maps of the axonal density and the fibre orientation.

2056.   Diffusion Spectrum Imaging with PROPELLER EPI Acquisition
Ming-Chung Chou1, Ya-Ling Lin1, Hsiao-Chien Miao1, Hing-Chiu Chang2, Tsyh-Jyi Hsieh3, and Gin-Chung Liu3
1Department of Medical Imaging and Radiological Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan, 2Graduate Institute of Biomedical Engineering and Bioinformatics, National Taiwan University, Taipei, Taiwan, 3Department of Medical Imaging, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan

Diffusion Spectrum Imaging (DSI) is an imaging technique capable of resolving intra-voxel fiber crossings and has been widely utilized to study neuronal fiber tracts in human brain. Since DSI technique requires hundreds of diffusion directions being sampled in Cartesian coordinate of q-space and takes very long acquisition time, echo-planar imaging (EPI) was usually employed to acquire the DSI data due to its high time-efficiency and high signal-to-noise ratio. However, the insufficient bandwidth in the phase-encoding direction caused strong susceptibility distortions in diffusion-weighted EPI. PROPELLER EPI was demonstrated to have capability of reducing susceptibility distortions and has been utilized to acquire DTI data [2]. Also, by using the keyhole reconstruction, the PROPELLER EPI can be further harnessed to reduce susceptibility distortions in QBI without lengthening acquisition time. Hence, this study employed PROPELLER acquisition to acquire DSI data and compare the fiber tracts with those of conventional DSI, and results showed that the tracts were in better agreement with anatomical locations in TSE T2WI.

2057.   Accurate Estimation of a Multiple Fascicle Model Is Enabled by Manipulation of Gradient Strength in a Two-Shell HARDI to Achieve Low TE.
Benoit Scherrer1 and Simon K. Warfield1
1Radiology, Harvard Medical School and Boston Children's Hospital, Boston, MA, United States

We propose a novel Cube and Sphere (CUSP) diffusion gradient encoding scheme that images multiple non-zero b-values with low TE and therefore high SNR to estimate a multi-tensor model. It is constructed from the projection of a two-shell HARDI on the enclosing cube of the inner shell, by reducing the gradient strength until the cube surface is reached. We shows that, despite the fact that CUSP doesn’t have full spherical coverage, it does not introduce any angular sensitivity to fascicle orientation and provides a lower estimation uncertainty than the corresponding two-shell HARDI. CUSP enables accurate white matter diffusion imaging.

2058.   Axon Diameter Distribution (ADD) MRI
Raisa Z. Freidlin1, Evren Ozarslan2, Sinisa Pajevic1, Michal E. Komlosh3, and Peter J. Basser3
1NIH/CIT/DCB, Bethesda, MD, United States, 2Radiology, BWH, Harvard Medical School, Boston, MA, United States, 3NIH/NICHD/PPITS, Bethesda, MD, United States

Obtained the axon diameter distribution (ADD) for fascicles in any orientation, anywhere within a brain volume, is based on estimate of an average propagator in each voxel using a 3-D generalization that determines the direction of maximum diffusivity and then estimates the DW signal attenuation profile. Two novel statistical model are used to fit ADD data. One is a parametric probability density function (pdf) developed by maximizing the information transmitted along fascicles subject to anatomical and energetic constraints. The second is a non-parametric modeling framework that empirically determines the form of the pdf by using non-uniform b-splines (NUBS).

2059.   Whole-Body STIR Diffusion-Weighted MRI in One Third of the Time
Alto Stemmer1, Wilhelm Horger1, and Berthold Kiefer1
1Healthcare Sector, Siemens AG, Erlangen, Germany

This work describes a recently developed DW-EPI sequence with STIR fat suppression. The sequence utilizes an efficient IR interleaving scheme and thereby allows reducing scan times of whole Body DWI up to one third.

2060.   Reduced FOV Diffusion-Weighted 3D-EPI
Mathias Engström1,2 and Stefan Skare1,2
1Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Stockholm, Sweden, 2Department of Neuroradiology, Karolinska University Hospital, Stockholm, Stockholm, Sweden

This work details a reduced FOV, parallel imaging accelerated, diffusion-weighted 3D-EPI sequence for head, neck, and spine imaging. The sequence combines inner volume imaging with GRAPPA parallel imaging reconstruction for increased distortion reduction.

2061.   Simultaneous Multislice Readout-Segmented Diffusion-Weighted EPI with Blipped-Controlled Aliasing
Samantha J. Holdsworth1, Rafael O'Halloran1, Anh Tu Van1, Eric Aboussouan1, William A. Grissom2, Anuj Sharma2, Murat Aksoy3, Julian R. Maclaren3, Stefan Skare4, and Roland Bammer3
1(Equal contribution): Center for Quantitative Neuroimaging, Department of Radiology, Stanford University, Palo Alto, CA, United States, 2(Equal contribution): Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, United States, 3Center for Quantitative Neuroimaging, Department of Radiology, Stanford University, Palo Alto, CA, United States, 4Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden

Readout-segmented EPI (RS-EPI) has been shown as a promising candidate for reducing distortion in diffusion-weighted (DW)-EPI while being robust to motion-induced phase errors. However, the requirement of several adjacent segments (or 'blinds') in RS-EPI can make the scan time can prohibitively long – particularly for thin slices which require a large number of slices to achieve full brain coverage. In this work, we reduce the minimum TR in RS-EPI with the use a simultaneous multislice acquisition using PINS multiband pulses coupled with blipped-controlled aliasing.

2062.   Diffusion MRI Based on SPatio-temporal ENcoding: Analytical Description and Validation
Eddy Solomon1, Noam Shemesh1, and Lucio Frydman1
1Chemical Physics, Weizmann Institute of Science, Rehovot, Israel

Single-scan SPatio-temporal ENcoding (SPEN) MRI is explored as an alternative for acquiring diffusion-weighted images. As these experiments involve the combined application of frequency-swept pulses and magnetic field gradients, the Stejskal-Tanner derivation of the b-values is no longer valid; in addition to diffusion-sensitizing gradients, SPEN’s gradients and swept RF fields impose additional spatially-dependent diffusion weightings over the sample. These effects, as well as potential cross-talk terms between the diffusion-sensitizing and SPEN gradients, are calculated in this study. Excellent agreement is then found between the analytical predictions and SPEN diffusion experiments in isotropic phantoms and anisotropic systems including spinal-cords.

2063.   Accelerated Multi-Shot Diffusion Imaging
Bruno Madore1, Jr-Yuan Chiou1, Renxin Chu1, Tzu-Cheng Chao2, and Stephan E. Maier1
1Department of Radiology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States, 2Department of Computer Science and Information Engineering, National Cheng-Kung University, Tainan, Taiwan

A method is proposed to reduce geometric distortions in diffusion-weighted imaging, at essentially no cost in scan time. The approach exploits the fact that diffusion-encoded data tend to be sparse when represented in the kb-kd space, where kb and kd are the Fourier transform duals of b and d, the b-factor and the diffusion direction, respectively. A main characteristic of the present work is how thoroughly navigator data get utilized in the reconstruction: The phase is used for motion correction, while the magnitude in kb-kd space is used for regularization purposes. Results were obtained showing marked reductions in image distortion as compared to single-shot EPI acquisitions.

2064.   Diffusion Weighted Imaging with Whole Brain Coverage and Sub-Microliter Voxels
Joseph L. Holtrop1,2 and Bradley P. Sutton1,2
1Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 2Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, United States

Diffusion weighted imaging provides a contrast mechanism that is sensitive to the microscopic restrictions of water. This contrast can be used to infer information about the general health of the tissue, integrity of white matter tracts, or to study microvascular blood flow. In this work, we demonstrate a 3D multislab technique that can be used to create images with comparable resolutions and coverage to high resolution structural MRI scans, but with diffusion weighting as contrast. Results from a 3 T system with 0.8 mm isotropic resolutions and whole brain coverage are presented.

2065.   Mapping Axon Radius in the Human Corpus Callosum Using Dual Spin-Echo Diffusion MRI
Jonathan D. Clayden1, Zoltan Nagy2, Nikolaus Weiskopf2, Daniel C. Alexander3, and Christopher A. Clark1
1Institute of Child Health, University College London, London, United Kingdom, 2Wellcome Trust Centre for Neuroimaging, University College London, London, United Kingdom, 3Centre for Medical Image Computing, University College London, London, United Kingdom

The use of diffusion MRI to estimate physical microstructure parameters such as axon radius and density has gained a lot of recent attention. Here we present the first in vivo axon radius maps derived from an optimised dual spin-echo pulse sequence.

2066.   Optimization of Scan Parameters for Diffusion Kurtosis Imaging at 1.5 T
Suguru Yokosawa1,2, Yoshitaka Bito1, Yoshihisa Soutome1, Kenji Ito2, Fumio Yamashita2, Kohsuke Kudo2, and Makoto Sasaki2
1Central Research Laboratory, Hitachi, Ltd., Kokubungi-shi, Tokyo, Japan, 2Division of Ultrahigh Field MRI, Institute for Biomedical Science, Iwate Medical University, Yahaba, Iwate, Japan

We investigated the effects of the b-values, number of diffusion directions, and number of signals averaged (NSA) on the accuracy of diffusion kurtosis imaging (DKI) and attempted to determine the ideal combinations of these parameters to achieve both accuracy and time efficiency at 1.5 T. We demonstrated that a b-value of 2500 s/mm2 and the NSA can improve the accuracies of DKI maps and that varying the numbers of b-values and diffusion directions was not effective for this purpose. Accurate DKI maps can be obtained with an acceptable acquisition time even at 1.5 T when the scan parameters are optimized.

2067.   Clinical Feasibility of High-Resolution Single-Shot Diffusion Tensor Trace -Weighted (SsTW) MRI
Alexandru V. Avram1, Joelle E. Sarlls2, Raisa Z. Freidlin3, and Peter J. Basser1
1Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, MD, United States, 2National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States, 3Division of Computational Bioscience, CIT, National Institutes of Health, Bethesda, Maryland, United States

Given the clinical importance of the mean apparent diffusion coefficient (ADC), we revisit strategies for measuring this important parameter in a single scan and propose an optimized solution for achieving high-resolution diffusion tensor trace -weighted imaging with whole brain coverage. Mean ADC maps measured using the proposed method are similar to those obtained using conventional diffusion tensor imaging (DTI), despite the significant scan time reduction. This technique could be uniquely suited to provide a quantitative microstructural assessment in whole-brain and whole-body diffusion MRI applications where motion is problematic.

2068.   Angular Double-PGSE Spectroscopy of the Long Evans Shaker Spinal Cord
Debbie Anaby1, Ian D. Duncan2, Chelsey M. Smith2, and Yoram Cohen1
1Tel Aviv University, Tel Aviv, Tel Aviv, Israel, 2Medical Sciences, University of Wisconsin-Madison, Madison, Wisconsin, United States

Conventional single-pulsed-field-gradient (s-PFG) methodologies are capable of faithfully depicting diffusion anisotropy in coherently ordered structures. However, randomly oriented compartments are more difficult to characterize. Double-PFG (d-PFG) MR methodologies were recently suggested as an alternative for studying microstructure in CNS. Specifically, the angular d-PFG experiment may offer novel microstructural information that is not available from s-PFG by yielding specific signatures in relatively low q values. The angular d-PFG was used to distinguish between control and Long Evans Shaker (les) spinal cords by providing information on macroscopic anisotropy and compartment shape anisotropy.

2069.   Mapping of Microscopic Diffusion Anisotropy Measures in the Living Human Brain
Marco Lawrenz1,2 and Jürgen Finsterbusch1,2
1Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Hamburg, Germany, 2NeuroimageNord, Hamburg-Kiel-Lübeck, Hamburg-Kiel-Lübeck, Germany

Double-wave-vector diffusion-weighting experiments with two weighting periods applied successively offer access to microscopic tissue. Thus, they may help to overcome confounds of DTI, e.g. in white matter fibre crossings. But so far, only the angular signal modulation that reflects the presence of microscopic diffusion anisotropy has been detected in vivo. This study extends present experiments to determine rotationally invariant measures of the microscopic diffusion anisotropy introduced recently. With the dedicated direction combination schema experimental signal variations could be reduced which improves the reliability of the measures. Additionally, the rotational invariance and the applicability in full brain white matter are demonstrated.

2070.   Localized Double-Pulsed-Field-Gradient MRS of CNS Metabolites
Noam Shemesh1, Jean-Nicolas Dumez1, and Lucio Frydman1
1Department of Chemical Physics, Faculty of Chemistry, Weizmann Institute of Science, Rehovot, Israel

Angular double-Pulsed-Field-Gradient (d-PFG) MR is gaining increasing attention due to its ability to depict microstructural parameters such as microscopic anisotropy (ìA) and compartment shape anisotropy (csA) in macroscopically disordered systems such as gray matter (GM). Here, we developed localized d-PFG MRS in the aim of extending the methodology towards CNS metabolites. Both ìA and csA were detected for the first time in GM of pig spinal cords for Lac, NAA, Cre and Cho. As some metabolites are considered compartment-specific, we expect this methodology to reveal insights into the interplay between microstructure, function and metabolism.

2071.   Rotationally Invariant Double Pulsed Field Gradient Diffusion Imaging
Sune Nørhøj Jespersen1,2, Henrik Lundell3, Casper Kaae Sønderby3, and Tim B. Dyrby3
1CFIN/MINDLab, Aarhus University, Aarhus, Denmark, 2Department of Physics, Aarhus University, Aarhus, Denmark, 3Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark

Multiple pulsed field gradient diffusion sequences (PFG) with 2 diffusion encoding blocks have been shown to be able to detect pore shape anisotropy in macroscopically isotropic samples. However, current approaches to quantifying pore shape anisotropy are not rotationally invariant and are affected by the distribution of pore orientations when applied to macroscopically anisotropic systems. Here we present a rotationally invariant sampling scheme for double PFG involving 60 pairs of diffusion wave vectors, and study its properties with numerical simulations. We demonstrate it experimentally on a fixated vervet monkey brain, and obtain maps of a rotationally invariant pore shape anisotropy index.

2072.   Whole-Brain Assessment of Microscopic Anisotropy Using Multiple Pulse-Field Gradient (MPFG) Diffusion MRI
Alexandru V. Avram1, Joelle E. Sarlls2, and Peter J. Basser1
1Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, MD, United States, 2National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States

Recent studies have shown that multiple pulsed-field gradient (mPFG) diffusion MRI has the potential to exclusively characterize water trapped in microscopic compartments with unique measures of average cell geometry. We applied quadruple PFG diffusion MRI on a clinical scanner to assess microstructural anisotropy parameters across the whole brain. Calculated maps of average axon diameter, axonal water diffusivity, intra-axonal signal fraction, and extracellular water diffusivity provide information that is complementary to that obtained with conventional diffusion tensor imaging (DTI). Upon further improvements in acquisition strategy and tissue modeling, mPFG diffusion MRI could provide a non-invasive whole brain histological assessment.

Increasing the Sensitivity of Temporal Diffusion Spectroscopy with Circularly Polarized Oscillating Gradient Spin Echo
Henrik Lundell1, Casper Kaae Sønderby1, and Tim B. Dyrby1
1DRCMR, Copenhagen University Hospital Hvidovre, Hvidovre, Hvidovre, Denmark

We introduce circularly polarized OGSE (CP-OGSE) as a way to increase diffusion weighting and thus the contrast in high frequency OGSE for the study of tissue microstructure. We show in simulations and experiments on perfusion fixed monkey brain tissue that multi-planar CP-OGSE improves data quality substantially and renders the same rotationally invariant diffusion tensor metrics as the conventional OGSE. CP-OGSE can be a significant contribution for making OGSE and temporal diffusion spectroscopy possible with higher frequencies and makes the technique realizable for studies of the human brain in vivo on clinical systems with moderate gradient strengths.

2074.   Modelling Extra-Axonal Diffusion Spectra for Oscillating Gradient Measurements
Wilfred W. Lam1, Saad Jbabdi1, and Karla L. Miller1
1FMRIB Centre, University of Oxford, Oxford, Oxon, United Kingdom

Diffusion imaging has enormous potential for quantitative measurements of properties like axon diameter that are directly relevant to brain function and pathology. Most work has focused on intra-axonal diffusion, despite the fact that significant signal is expected to arise from the extra-axonal space. Current diffusion models do not account for the frequency dependence of extra-axonal signal in oscillating gradient experiments. Two analytic models are proposed for the diffusion attenuation spectra of spins diffusing in the space between regularly packed cylinders. We compare our model predictions to Monte Carlo simulations. These models capture salient properties of extra-axonal diffusion spectra.

2075.   Bipolar Single Spin Echo: Diffusion Encoding with Concomitant Field and Eddy Current Correction
R. Marc Lebel1,2, Corey Allan Baron3, Christian Beaulieu3, Ek T. Tan4, and Ajit Shankaranarayanan5
1GE Healthcare, Calgary, Alberta, Canada, 2Radiology, University of Calgary, Calgary, Alberta, Canada, 3Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada, 4GE Global Research, Niskayuna, New York, United States, 5GE Healthcare, Menlo Park, California, United States

Diffusion imaging has become a crucial component of clinical and research protocols; robust and accurate diffusion encoding schemes are required to produce consistent and factual results. It was recently shown that the dual spin echo encoding scheme is prone to erroneous measurements due to concomitant fields, while the Stejskal-Tanner single spin echo encoding is susceptible to eddy currents. We present and validate an alternative encoding scheme, called bipolar single spin echo, which alleviates many of the problems encountered with current diffusion preparations.

2076.   Two-Scan Multiple Echo Diffusion Tensor Acquisition Technique on a 3T Clinical Scanner with Application to Skeletal Muscle
Steven Baete1, Gene Cho1,2, and Eric E. Sigmund1
1Center for Biomedical Imaging, Dept. of Radiology, NYU Langone Medical Center, New York, NY, United States, 2Sackler Institute of Graduate Biomedical Sciences, NYU School of Medicine, New York, NY, United States

This abstract describes a method with accelerated diffusion encoding, capable of acquiring a full diffusion tensor in just two encodings on a clinical scanner. The method, Multiple Echo Diffusion Tensor Acquisition Technique (MEDITATE), employs five rf-pulses, optimized for the tissue of interest, and a pattern of diffusion gradients to encode a train of echoes with different diffusion weightings and directions. The resulting signals can be used to estimate DTI parameters as demonstrated in in vivo skeletal muscle. This sequence may be useful in the future in clinical applications requiring time-sensitive acquisition of DTI parameters such as dynamical DTI in muscle.


Monday, 22 April 2013 (16:30-18:30) Exhibition Hall
Diffusion: Noise, Artifacts & Phantoms

2077.   Low-Rank Basis Smoothing for the Denoising of Diffusion Weighted Images
Stephen F. Cauley1, Obaidah A. Abuhashem2, Berkin Bilgic3, Itthi Chatnuntawech3, Julien Cohen-Adad4, Kawin Setsompop5, Elfar Adalsteinsson2,5, and Lawrence L. Wald5,6
1A.A. Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 2Department of Electrical Engineering and Computer Science, MIT, Cambridge, MA, United States, 3Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, 4Department of Electrical Engineering, Institute of Biomedical Engineering, Ecole Polytechnique de Montreal, Montreal, QC, Canada, 5A.A. Martinos Center for Biomedical Imaging, Dept. of Radiology, MGH, Charlestown, MA, United States, 6Harvard-MIT Division of Health Sciences and Technology, MIT, Cambridge, MA, United States

The substantial signal attenuation in DI images for large b-values can affect accurate calculation of orientation distribution functions (odf) and fiber tracks. In addition, the low signal-to-noise (SNR) observed at large b-values hinders the performance of popular denoising methods like the LMMSE estimator and the NLM filter. In this work we demonstrate the benefits of basis smoothing within a low-rank DWI estimation framework. Our method significantly reduces the dependencies on noisy basis vectors while preserving root-mean-square error (RMSE) relative to low-noise data (computed by averaging multiple acquisitions).

Higher Order Variational Denoising for Diffusion Tensor Imaging
Florian Knoll1, Tuomo Valkonen2, Kristian Bredies3, and Rudolf Stollberger1
1Institute of Medical Engineering, Graz University of Technology, Graz, Austria, 2Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom, 3Department of Mathematics and Scientific Computing, University of Graz, Graz, Austria

High resolution diffusion weighted imaging and diffusion tensor imaging with isotropic voxels are desirable for a large number of applications. Unfortunately, acquisitions of such data sets are challenging, due to the notoriously low SNR of DWI. In addition, even with fast sequences like single shot EPI, measurement times often become prohibitively long because of the large number of diffusion encoding directions that have to be acquired. In this work we introduce two higher-order variational denoising approaches to reconstruct DTI data with isotropic voxels from a single average which are based on Total Generalised Variation.

2079.   A Simple Retrospective Noise Correction for Diffusional Kurtosis Imaging
Russell Glenn1, Ali Tabesh1, and Jens H. Jensen1
1Radiology and Radiological Sciences, Medical University of South Carolina, Charleston, SC, United States

Diffusion MRI (dMRI) measurements are positively biased by noise from use of magnitude reconstructed images. The effects of the noise bias increase with decreasing signal-to-noise ratio (SNR), which can be problematic in high resolution dMRI acquisitions. A simple, retrospective noise correction technique is described and a weighted linear least squares fitting algorithm is presented for diffusional kurtosis imaging (DKI). Noisy phantom data is analyzed in DKI datasets with variable SNR, and the results of the noise correction are compared to uncorrected and reference data. Noise correction substantially reduces the bias in kurtosis estimates.

2080.   Noise Estimation for Averaged DW MR Images
Nikolaos Dikaios1, Valentin Hamy1, Shonit Punwani1, and David Atkinson1
1Centre for Medical Imaging, University College London, London, Greater London, United Kingdom

The scope of this project was to estimate the noise using an adaptation of the median-absolute-deviation (MAD) in the wavelet domain for the expected noise distribution, and calculate the diffusion coefficient (ADC) with a non linear regression (NR) algorithm that accounts for underlying noise.

2081.   Estimation of Spatially Variable Rician Noise Map in Diffusion MRI
Jelle Veraart1, Jeny Rajan1, Ronald R. Peeters2, Alexander Leemans3, Stefan Sunaert2, and Jan Sijbers1
1Vision Lab, University of Antwerp, Antwerp, Belgium, 2Dept. Radiology, University Hospitals of Leuven, Leuven, Belgium, 3Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands

Diffusion magnetic resonance imaging (dMRI) is widely used to quantify water diffusion in biological tissue. The accuracy of diffusion model-specific measures will be limited if not accounting for the statistical distribution of the magnitude dMRI data. The prior knowledge of the underlying noise is thus of importance when aiming for more accurate dMRI analyses. Many existing techniques to estimate the noise parameters rely, however, on assumptions that are generally not fulfilled in actual dMRI. Therefore, a new approach is presented.

2082.   Influence of Image Noise and Microcapillary Perfusion (IVIM) on Diffusional Kurtosis Measurements in the Body
Olaf Dietrich1, Anno Graser2, Martina Karpitschka2, Melvin D'Anastasi2, and Maximilian F. Reiser1,2
1Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Munich, Germany, 2Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, Munich, Germany

The purpose of this study was to analyze the influence of image noise and intravoxel-incoherent-motion (IVIM) effects on diffusional kurtosis imaging (DKI) outside the brain. DKI was performed in the prostate (bmax=2000s/mm²) and data was analyzed with and without fit of the noise level and with and without suppression of IVIM effects. Kurtosis values were substantially increased due to noise and also due to IVIM effects at low b-values. Including the image noise level into the kurtosis analysis and choosing a minimum b-value of 200s/mm² is recommend for DKI outside the brain.

2083.   On the Phase-Error Propagation in Diffusion-Weighted Steady State Free Precession (DW-SSFP) Imaging
Roland Bammer1 and Rafael O'Halloran1
1Center for Quantitative Neuroimaging, Department of Radiology, Stanford University, Stanford, CA, United States

Diffusion-weighted SSFP (dwSSFP) offers an efficient diffusion preparation and is a promising approach to high-resolution 3D DW MRI. As a multi-shot technique dwSSFP is affected by shot-to-shot phase inconsistencies as all multi-shot diffusion-weighted sequences are. However, because the steady state signal is composed of the constructive addition of many phase coherence pathways, motion-induced phase accrued during the application of a single diffusion-encoding gradient can propagate to subsequent phase pathways. This represents an additional mechanism of signal loss in dwSSFP. In this work, these errors are classified into two types and strategies for correcting each type are discussed.

2084.   Estimation and Compensation of Motion-Induced Phase Error in 3D for Multi-Shot Diffusion Acquisitions
Eric Aboussouan1, Anh Tu Van1, Rafael O’Halloran1, Samantha J. Holdsworth1, Marcus T. Alley1, Murat Aksoy1, and Roland Bammer1
1Radiology, Stanford University, Stanford, California, United States

Synopsis: High-resolution diffusion-weighted imaging is limited to multi-shot acquisitions, which are subject to signal decay due motion-induced phase variations. These variations are caused by rigid-body (non-repeatable) and pulsatile (repeatable over the cardiac cycle) motion during the diffusion-encoding period. It is possible to prospectively correct this phase before the creation of the spurious echo pathways in RF-refocused sequences (e.g. FSE, SSFP). While linear and constant phase errors can be corrected with gradient blips and the RF phase, the non-linear phase component should be compensated by the application of an RF pulse designed to remove that particular phase profile. In this work we will investigate methods to estimate the non-linear component of the 3D motion-induced phase and compensate it using a time-efficient 3D RF pulse design.

2085.   Effects of Corrupted Signals on Orientation Distribution Function in Q-Ball Imaging: A Simulation Study
Yen-Wei Cheng1, Ming-Chung Chou2, Wen-Yih Isaac Tseng3, and Hsiao-Wen Chung4
1Department of Electrical Engineering, National Ilan University, IIran, Taiwan, 2Department of Medical Imaging and Radiological Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan, 3Center for Optoelectronic Biomedicine, National Taiwan University, Taipei, Taiwan, 4Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan

The purpose of this study was to simulate the randomly corrupted signals and evaluate the resultant ODF errors as well as error reduction rates by using a neighboring interpolation correcting method. The simulation was performed by generating corrupted signals in the gold standard QBI with random loss of signal intensity as well as random occurrence of pixel location. We found that the reduction rates of ODF errors by neighboring interpolation method were 82.62%, 79.32%, 77.67% for b = 2000, 3000, 4000 s/mm2 QBI datasets, so it suggests the proposed NI method is helpful to correct signal loss artifacts in QBI.

2086.   Influences of B-Value on the Reproducibility and Accuracy of Diffusion Kurtosis Imaging
Ming-Chung Chou1, Wan-Hsin Wen1, Sheng-Fang Huang1, Cheng-Wen Ko2, and Ping-Hong Lai3
1Department of Medical Imaging and Radiological Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan, 2Department of Computer Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan,3Department of Radiology, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan

Diffusion kurtosis imaging (DKI) was demonstrated to successfully estimate the non-Gaussian distribution of water diffusion in vivo and has been applied in many clinical applications. Similar to diffusion tensor imaging, b-value is an important factor in the measurement of DKI indices and may have influential effects on them. Rapid DKI with three b-values was proposed to obtain DKI indices in clinically acceptable time, but the results may be affected by the choice of b-value. This study performed repeated measurement to investigate the effects of b-value on the reproducibility and accuracy of DKI indices and found that both reproducibility and accuracy were impacted by b-values.

2087.   Variability Analyses of Track Density Imaging
Javier Urriola Yaksic1, Nyoman Dana Kurniawan1, Zhengyi Yang2, and David C. Reutens1
1Centre for Advanced Imaging, The University of Queensland, Brisbane, Queensland, Australia, 2Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Queensland, Australia

Track density imaging (TDI) mapping method has been developed to dramatically increase the spatial resolution of diffusion-weighted imaging (DWI) data beyond the acquired resolution. However, it is not clear if TDI maps can be used to reliably to quantify differences in brain populations. This project aims to characterise short track TDI (stTDI) in terms of stability and reproducibility as a quantitative tool for group comparison of brain structures. Our results showed that stTDI produced more consistent profile in the white matter compared to the gray matter. Multiple stTDI reconstructions of a single dataset need to be generated then averaged to minimise the noise resulting from probabilistic fibertracking. Limited comparison between intra- and inter-subject variability suggests that stTDI could be developed as a method to measure differences in brain structures between two populations.

2088.   Evaluating Longitudinal Reliability and Cross-Subject Sensitivity of Structural Connectivity Networks Computed Using Probabilistic Fiber Tracking
Alex Smith1, Madhura Ingalhalikar1, and Ragini Verma1
1Section for Biomedical Image Analysis, University of Pennsylvania, Philadelphia, PA, United States

This study assesses the reliability of graph metrics extracted from structural networks constructed via probabilistic tractography, and the sensitivity of such networks to individual subjects. Both weighted and binarized networks were evaluated. It was found that subjects could be differentiated based on their weighted structural connectivity patterns, suggesting that such networks can be used in population studies. The intraclass correlation coefficients (ICCs) of the assessed metrics tended to be moderately high across network types, indicating longitudinal robustness across scan sessions. The ICCs tended to be lower in the weighted networks, possibly due to their decreased uniformity versus the binarized versions.

2089.   Reproducibility of Connectivity Based Parcellation - Primary Visual Cortex
Jérémy Lecoeur1, Madhura Ingalhalikar1, and Ragini Verma1
1Section of Biomedical Image Analysis, Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States

This study investigates the stability of cortical connectivity based parcellation over time. Such parcellations provide a unique characterization of the brain and it is believed that any change can be interpreted as being introduced by pathology or development. Hence a parcellation profile for a person could be defined using this paradigm and that constitutes a first step in quantifying differences between subjects, facilitating a meaningful clinical study. We demonstrate that such parcellation for the primary visual cortex is replicable over time with high similarity scores between the obtained clusters with an unsupervised algorithm.

2090.   Optimisation of ex Vivo Diffusion Imaging: The Effects of Tissue Preparation and Imaging Parameters on Data Quality
David Alexander Slater1, Po-Wah So2, Karthik Munikoti Prakash2, Istvan Bodi3, Michel Modo4,5, and Flavio Dell'Acqua1,6
1NATBRAINLAB, Department of Neuroimaging, King's College London, Institute of Psychiatry, London, United Kingdom, 2Department of Neuroimaging, King's College London, Institute of Psychiatry, London, United Kingdom, 3Department of Clinical Neuropathology, King's College Hospital, London, United Kingdom, 4McGowan Institute for Regenerative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States,5Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 6NIHR Biomedical Research Centre for Mental Health at South London and Maudsley NHS Foundation Trust, King's College London, Institute of Psychiatry, London, United Kingdom

Diffusion imaging of fixed human brain tissue has the potential to reveal neuroanatomical details at a scale that remains largely unexplored. Here we investigated how the optimisation of tissue sample preparation and imaging parameters can increase data quality. Our findings suggest that phosphate-buffered saline (PBS) and specific concentrations of the contrast agent GD-DTPA have the potential to dramatically increase SNR-efficiency at short TE and TR. However, longer diffusion times also provide improved diffusion contrast and thus a balance is required between potential increases in SNR-efficiency and diffusion contrast. These findings may provide improved SNR, enhanced resolution and/or faster acquisitions.

2091.   A High-Speed Diffusion-Weighted MRI Simulator with Bloch-Torrey Equation
Shogo Fujii1, Etsuji Yamamoto1, Yo Taniguchi2, and Yoshitaka Bito1,2
1Graduate School of Engineering, Chiba University, Chiba-shi, Japan, 2Central Research Laboratory, Hitachi, Ltd., Kokubunji-shi, Japan

The purpose of this study is to develop a DWI simulator, which can generate the images for the adult human brain size models in a reasonable time. In order to shorten the computation time, we proposed three approaches based on the principle of MRI to increase simulation efficiency and succeded in improving the efficiency approximately 140,000 times. As a result, simulation time for an adult human brain size model reduced to less than one hour.

2092.   SNR-Dependent Quality Assessment of Compressed-Sensing-Accelerated Diffusion Spectrum Imaging Using a Fiber Crossing Phantom
Tim Sprenger1,2, Brice Fernandez3, Jonathan I. Sperl1, Vladimir Golkov1,2, Michael Bach4, Ek T. Tan5, Kevin F. King6, Christopher J. Hardy5, Luca Marinelli5, Michael Czisch7, Philipp Sämann7, Axel Haase8, and Marion I. Menzel1
1GE Global Research, Garching, Germany, 2Technical University Munich, Garching, Germany, 3GE Healthcare, Munich, Germany, 4German Cancer Research Center, Heidelberg, Germany, 5GE Global Research, Niskayuna, NY, United States, 6GE Healthcare, Waukesha, WI, United States, 7Max Planck Institute for Psychiatry, Munich, Germany, 8Technische Universität München, Garching, Germany

Conventional diffusion spectrum imaging (DSI) requires Nyquist or full-sampling of q-space, and hence suffers from long acquisition times. To overcome this limitation, compressed-sensing-accelerated DSI has been proposed recently. For this technique q-space is randomly undersampled and subsequently reconstructed exploiting the signal sparsity in an appropriate transform domain. This work studies the SNR-dependent performance of compressed sensing-accelerated DSI using a fiber crossing phantom and by that validates the superior signal recovery and denoising properties.

2093.   Avian Egg Latebra as Tissue Water Diffusion Model
Stephan E. Maier1 and Robert V. Mulkern2
1Department of Radiology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States, 2Department of Radiology, Harvard Medical School, Children's Hospital, Boston, MA, United States

The egg presents a simple but relevant object for exploring biophysical aspects of common tissue contrast parameters like diffusion and transverse relaxation. The biexponential characterization of the white yolk containing latebra diffusion signal decay results in diffusion coefficients and signal fractions that are very similar to those found in brain. White yolk contains spheres with membranes. The size of the spheres observed in white yolk falls in the range of cell sizes typically encountered in tissues. The avian egg latebra, is thus an easily accessible model for tissue water diffusion

2094.   A Simple and Robust Test Object for Diffusion Kurtosis
Jonathan Phillips1,2 and Geoffrey David Charles-Edwards3
1Medical Engineering and Physics, King's College London, 124-126 Denmark Hill, London, United Kingdom, 2Institute of Life Science 2, Swansea University, Swansea, Wales, United Kingdom, 3Medical Physics, St. Thomas' Hospital, Westminster Bridge Road, London, United Kingdom

Diffusion kurtosis imaging (DKI) is an extension of conventional diffusion-weighted MRI which fits a model to diffusion b-value images from which a value of diffusion kurtosis K, the degree to which diffusion is non-Gaussian, is obtained. We present a simple and robust DKI test object based upon colloidal spheres dispersed in water. A linear relationship between concentration of spheres and kurtosis is found. DKI measurements over a period of time showed excellent reproducibility indicating the suitability of these colloidal spheres as a long term test object for DKI.


Monday, 22 April 2013 (16:30-18:30) Exhibition Hall
Diffusion: Pre-Clinical & Clinical Applications

2095.   Towards Spinal Cord Microstructure Mapping with the Neurite Orientation Dispersion and Density Imaging
Francesco Grussu1, Torben Schneider1, Hugh Kearney1, Hui Zhang2, David H. Miller1, Olga Ciccarelli3, Daniel C. Alexander2, and Claudia Angela M. Wheeler-Kingshott1
1NMR Research Unit, Queen Square MS Centre, Department of Neuroinflammation, UCL Institute of Neurology, London, England, United Kingdom, 2Department of Computer Science and Centre for Medical Image Computing, University College London, London, England, United Kingdom, 3NMR Research Unit, Queen Square MS Centre, Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, England, United Kingdom

We investigate the feasibility of Neurite Orientation Dispersion Imaging (NODDI) in the spinal cord. NODDI is a new technique that promises novel markers of neuronal density and dispersion, which may be informative in diseases like Multiple Sclerosis (MS) beyond routine Diffusion Tensor Imaging (DTI). Here we compare NODDI with standard DTI metrics in healthy volunteers and MS patients. NODDI disentangles the microscopic sources of DTI measures and provides better discrimination between very coherent and less coherent neural tissue structures. Further work will improve the acquisition protocol and study NODDI in a larger patient cohort.

2096.   Histological Correlation of DKI-White Matter Modeling Metrics in the Cuprizone-Induced Corpus Callosum Demyelination
Maria F. Falangola1,2, David Guilfoyle3, Edward S. Hui1, Xingju Nie1, Ali Tabesh1, Jens H. Jensen1, Scott Gerum3, Caixia Hu3, John LaFrancois3, Heather Collins1, and Joseph A. Helpern1,2
1Radiology and Radiological Science, Center for Biomedical Imaging, Medical University of South Carolina, Charleston, SC, United States, 2Neurosciences, Medical University of South Carolina, Charleston, SC, United States, 3Nathan Kline Institute, Orangeburg, NY, United States

The goal of this study was to utilize a recently developed white matter modeling method compatible with diffusional kurtosis imaging to characterize the demyelination process in the corpus callosum of the cuprizone mouse model. We studied 10 cuprizone and 10 control mice for a period of 10 weeks. All diffusion metrics were derived from DKI datasets. Quantitative analysis of myelin density was performed using Solochrome staining. The histological correspondence shown in our results demonstrate the correspondence between the WMM metrics and a well established histological marker of myelin.

2097.   The Water Apparent Diffusion Coefficient, But Not T2, in ex vivo Brain Tissue Is Affected by Previous Exposure to Alkaline pH
Lindsey A. Leigland1, Marcus Cappiello2, and Christopher D. Kroenke1,3
1Advanced Imaging Research Center and Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, United States, 2Department of Physics, Oregon State University, Corvallis, OR, United States, 3Division of Neuroscience, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, OR, United States

The goal of this research was to improve understanding of the determinants of physical properties (spin relaxation, diffusion, etc.) in postmortem tissue, as well as further characterize the dependence of these molecular properties on common laboratory tissue processing procedures. Here we show that exposure of tissue to alkaline conditions can induce dramatic (>2-fold) and irreversible changes in the water apparent diffusion coefficient (ADC) without affecting the water 1H transverse relaxation, an effect that is potentially realized through modifications to biological membranes. This research provides an avenue toward developing further insight into the determinants of physical parameters observable by MRI.

2098.   Potential of Diffusion Tensor Imaging as a Virtual Dissection Tool for Cardiac Muscle Bundles: A Pilot Study
Seongjin Choi1, Ria Mazumder2, Petra Schmalbrock1, Michael V. Knopp1, Richard D. White1,3, and Arunark Kolipaka1,3
1Radiology, The Ohio State University, Columbus, Ohio, United States, 2Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio, United States, 3Internal Medicine, The Ohio State University, Columbus, Ohio, United States

Diffusion-based tractography has the potential to delineate complex cardiac muscle fiber architecture. We explored fractional anisotropy distribution, angle and length threshold dependency of tractography in a fixed heart specimen. Tracking method used in the brain research was applied straightforwardly. Among three tracking constraints, seeding FA value and minimum fiber length threshold noticeably affected the tractography results. z-component of principal eigenvectors was useful index for subepi/subendocardium segmentation. Three long fiber bundles of interest and subepi/subendocardium were segmented as a demonstration of this approach.

2099.   Concurrent Dual-Slice Cardiac DTI of the in-vivo Human Heart
Constantin von Deuster1,2, Christian T. Stoeck2, Daniel Giese1, Jack Harmer1, Rachel W. Chan3, David Atkinson3, and Sebastian Kozerke1,2
1Division of Imaging Sciences, King's College London, London, United Kingdom, 2Institute for Biomedical Engineering, ETH Zurich, Zurich, Switzerland, 3Centre for Medical Imaging, University College London, London, United Kingdom

Diffusion tensor imaging (DTI) of the beating human heart became feasible in the last years, employing Stimulated Echo (STEAM) sequences for diffusion acquisition. Several signal averages and diffusion encoding directions make the image formation process however fundamentally slow. Hence acquisitions for 3D whole heart fibre configurations are not clinically applicable as several slices are necessary. We could show that concurrent dual-slice single-shot EPI cardiac diffusion weighted imaging using multi-band STEAM and controlled aliasing in parallel imaging can be used to speed up scan speed by a factor of two.

2100.   Diffusion Tensor Imaging of Fresh and Formalin Fixed Porcine Hearts: A Comparison Study of Fiber Tracts
Ria Mazumder1, Seongjin Choi2, Bradley Dean Clymer1, Richard White2,3, and Arunark Kolipaka2,3
1Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, United States, 2Deparment of Radiology, The Ohio State University, Columbus, OH, United States, 3Deptarment of Internal Medicine, Division of Cardiology, The Ohio State University, Columbus, OH, United States

Diffusion tensor imaging (DTI) is a technique used for fiber tracking. It has been rarely explored to track cardiac fibers .Previous studies have used formalin fixed heart for tracking fibers. However, formalin fixation tends to change the diffusion properties of tissues. This study explores the effects formalin fixation has on fiber tracking when compared to fresh hearts. DTI analysis parameter such as fractional anisotropy was further exploited to track the fibers in fresh and formalin fixed hearts. We have observed that formalin fixation makes diffusion pattern of the cardiac muscle fibers more isotropic and thereby lowers the FA value.

2101.   SPatio-Temporal ENcoded Diffusion-Weighted Breast MRI Studies
Eddy Solomon1, Noam Nissan1,2, Hadassa Degani3, and Lucio Frydman1
1Chemical Physics, Weizmann Institute of Science, Rehovot, Israel, 2Biological Regulation, Weizmann Institute of Science, Rehovot, Israel, 3Biological Regulation, Weizmann Institue of Science, Rehovot, Israel

Breast imaging is particularly challenging owing to a number of factors, including the relatively high fat/water heterogeneities that characterize breast, the off-center character of the targeted organs, and the unavoidability of breathing/cardiac motions. Here we exploit SPEN’s abilities to deliver quality single-scan images even from challenging regions subject to all these problems, to explore its use in DW MRI. Diffusion SPEN measurements were carried out at 3T in female breast analyses, showing significant advantages in anatomical and diffusional information vis-à-vis EPI.

2102.   Diffusion Tensor Imaging of the Normal Human Uterus in vivo
Koji Fujimoto1, Aki Kido2, Tomohisa Okada2, Masato Uchikoshi3, and Kaori Togashi2
1Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University, Kyoto, Japan, 2Department of Diagnostic Imaging and Nuclear Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan,3Siemens Japan K.K., Tokyo, Japan

Uterine DTI was performed for nine healthy young women on a 3T scanner. VOIs were drawn for the outer myometrium (OM), junctional zone (JZ) and endometrium (EM). ADC, FA and maximum fiber length were compared. Fibers were classified into 12 groups and visually evaluated. ADC was highest for OM (1.12), followed by EM (0.97) and JZ (0.83). FA was highest for JZ (0.297), followed by OM (0.257) and EM (0.186). Fibers were longest in OM (42.0mm), followed by JZ (34.2mm) and EM (20.0mm). Circular orientation was observed in 50% (36/72) of fibers in OM and in 44% (32/72) in JZ.

2103.   Measurement of Apparent Diffusion Coefficients of Hyperpolarized 13C-Metabolites In-Vivo
Franz Schilling1,2, Jan Henrik Ardenkjær-Larsen3, Martin A. Janich2, Marion I. Menzel2, and Lise Vejby Søgaard3
1Institute of Medical Engineering, Technische Universität München, Garching, Germany, 2GE Global Research, Garching, Germany, 3Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark

We suggest a new approach to characterize the metabolism by performing apparent diffusion coefficient (ADC) measurements of hyperpolarized metabolites in-vivo. A diffusion-weighted pulse sequence was developed based on the pulsed gradient spin echo with low flip angle (α = 20˚) slice selective excitation in combination with a band-selective universal-rotation refocusing pulse optimized by optimal control theory. In two rats, we acquired 13C-metabolite ADCs in 3 spatial directions from lactate, alanine and pyruvate in muscle tissue at 4 different positions. The analysis of diffusion properties of intracellularly produced hyperpolarized compounds might potentially be useful for characterizing pathological changes in tumor cells.

2104.   Diffusion-Weighted MRI for the Early Response Assessment of Neoadjuvant Chemotherapy in Breast Cancer: Does Perfusion Effect Influence ADC Map Accuracy?
David Garbera1, Jyoti Parikh2, and Geoffrey David Charles-Edwards3
1Imaging Sciences, King's College London, London, United Kingdom, 2Radiology, Guy's and St Thomas' NHS Foundation Trust, London, United Kingdom, 3Medical Physics, Guy's and St Thomas' NHS Foundation Trust, London, United Kingdom

We analyse use of diffusion-weighted MRI (DWI) scanning, and generation of apparent diffusion coefficient (ADC) maps, in predicting early response to neoadjuvant chemotherapy (NACT) in patients with breast cancer. It is thought that perfusion effects may confound accuracy of ADC values calculated from DWI. We gathered mean ADC values from pre and mid-treatment scans by generating a region of interest around a whole lesion. Early changes in mean ADC value were correlated with eventual radiological response to NACT. Early change in mean ADC value performed better than long-axis measurements in predicting response. Only ADC maps excluding perfusion were significantly better.

2105.   in vivo Characterisation of Colorectal Tumour Microstructure with DW-MRI
Eleftheria Panagiotaki1, Simon Walker-Samuel2, Bernard M. Siow1,2, Peter Johnson3, Rosamund Barbara Pedley3, Mark F. Lythgoe2, and Daniel C. Alexander4
1Centre for Medical Image Computing, University College London, London, United Kingdom, 2Centre for Advanced Biomedical Imaging, University College London, London, United Kingdom, 3Cancer Institute, University College London, London, United Kingdom, 4Centre for Medical Image Computing, Dept Computer Science, University College London, London, United Kingdom

This work explores the diffusion weighted (DW) MR signal of cancer cell lines with a selection of multi-compartment diffusion models, adapting a method for diffusion model identification in brain tissue . Characterisation of colorectal cancer cells (CRC) can improve the response of the cells to treatment. Most previous cancer cell classification studies involve invasive histological methods that alter the state of the sample. This study uses DW-MRI to quantitatively characterise CRC cell lines in vivo based on their microstructure.

2106.   The Clinical Use of Diffusion-Weighted Magnetic Resonance Imaging for Oncological Biomarkers
Karen Bae1, Daniel Ying1, David Yerushalmi1, Alice Kim1, and Jinha Park1
1Diagnostic Radiology, City of Hope, Duarte, CA, United States

Diffusion-weighted magnetic resonance imaging (DW-MRI) has been suggested as a promising, non-invasive, yet quantitative tool to detect lesions. However, global implementation of DW-MRI as a means of assessing cancer faces challenges due to lack of quality assessments and no accepted standards for measurements and analysis. The purpose of this study was to address this issue by assessing a recently implemented liver DWI protocol at our institution - City of Hope National Medical Center. In this retrospective study, we investigated the apparent diffusion coefficient values of liver lesions and found a statistical difference between benign and malignant lesions (p<0.0001). These results were consistent with previously published reports and demonstrate the clinical benefit of adopting DWI as a standard sequence in a liver MRI protocol.

2107.   DTI Is More Sensitive to Detect Effects of Hypercapnia on White Matter Development in ELBW Infants Than Conventional MRI
Xiawei Ou1, Charles M. Glasier1, Raghu H. Ramakrishnaiah1, Sarah B. Mulkey2, Vivien L. Yap2, and Jeffrey R. Kaiser2
1Radiology, Arkansas Children's Hospital; University of Arkansas for Medical Sciences, Little Rock, AR, United States, 2Pediatrics, Arkansas Children's Hospital; University of Arkansas for Medical Sciences, Little Rock, AR, United States

Cerebral white matter injury is very common in extremely low birth-weight (ELBW) infant survivors of intensive care and is associated with poor long-term neurological outcomes. In this study, we used DTI in addition to conventional MRI to evaluate two groups of ELBW infants: one was randomized to permissive hypercapnia ventilation during the first week of life, and the other was randomized to normocapnic ventilation. We found that while the average white matter score from conventional MRI for the hypercapnic group was not significantly different with that in the normocapnic group, DTI revealed lower FA values and higher MD values in the genu and splenium of hypercapnic subjects, suggesting that hypercapnia may have unfavorable effects on the white matter development of ELBW infants, and DTI may be more sensitive to detect these effects than conventional MRI.

2108.   A Pilot Study of Motion Corrected DTI in the Fetal Brain
Georgia Lockwood Estrin1,2, Zhiqing Wu2, Serena J. Counsell3, Mary A. Rutherford1, and Joseph V. Hajnal2
1Perinatal Imaging, Imperial College London, London, United Kingdom, 2Centre for the Developing Brain, Kings College London, London, United Kingdom, 3Centre for the Developing Brain, King's College London, London, United Kingdom

Fetal DTI offers the potential to provide detailed information on normal white matter development. A major limitation is movement, which is often not addressed in fetal MR studies. This study employs a fully motion corrected reconstruction method including distortion correction using a measured B0 field map to measure fractional anisotropy (FA) in 19 fetuses. Results were compared with ex utero preterm FA data of similar post-menstrual ages. The fetal FA values were consistent with the preterm neonates, including trends with age. This provides confidence that the method is reliable and offers the opportunity to study white matter development in utero.

2109.   Distinct Cerebral Tissue Alterations in Diabetic and Hereditary Neuropathic Pain as Revealed by Voxel-Based Morphometry and Tract-Based Spatial Statistics
Arzu Ceylan Has1, Aslihan Taskiran Sag2, Cagri Mesut Temucin3, Nese Oztekin2, Fikri Ak2, and Kader Karli Oguz4
1National Magnetic Resonance Research Centre (UMRAM), Bilkent University, ANKARA, Turkey, 2Department of neurology, Ankara Numune Education and Research Hospital, ANKARA, Turkey, 3Department of Neurology, Faculty of Medicine, and Institute of Neurological Sciences and Psychiatry, Hacettepe University, ANKARA, Turkey, 4Department of Radiology and National Magnetic Resonance Research Centre (UMRAM), Hacettepe University and Bilkent University, ANKARA, Turkey

Neuropathic pain is caused by a lesion or a disease of the somatosensory system itself. It’s usually more prominent in acquired pathologies of nerve fibers like diabetic neuropathy (DNP) despite less severe degeneration than hereditary neuropathies (HNP). On the basis of differences in etiopathogenetic mechanisms, we hypothesized that grey and white matter alterations would reveal distinct patterns in patients with DNP and HNP.

Short-Term Plasticity of the Motor System Induced by Piano Learning
Ido Tavor1, Rotem Botvinik1, and Yaniv Assaf1
1Department of Neurobiology, Tel Aviv University, Tel Aviv, Israel

Diffusion MRI was recently shown to be sensitive to short term neuroplasticity in spatial learning. While spatial learning is expected to cause structural changes in limbic structures, the neuroplasticity aspects in higher cognitive domains are not straightforward. Thus in the current study we used DTI in order to investigate the neuroplasticity that accompanies motor learning. Non-musician subjects were scanned before and after a motor sequence learning task based on an electric piano keyboard. We found learning related changes in diffusion properties in motor system regions, suggesting that DTI can follow on short-term learning-related brain plasticity of an entire cognitive domain.

2111.   Laterality of the Corticospinal Tract and Variation with Handedness: The Findings of a DTI Study
Khin Khin Tha1, Satoshi Terae2, Hiroyuki Hamaguchi2, Kinya Ishizaka2, Makoto Hirotani2, Kazuyuki Minowa3, Yuriko Suzuki4, and Hiroki Shirato1
1Department of Radiobiology and Medical Engineering, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, Japan, 2Hokkaido University Hospital, Sapporo, Hokkaido, Japan, 3Hokkaido University Graduate School of Dental Medicine, Sapporo, Hokkaido, Japan, 4Philips electronics Japan, Ltd., Tokyo, Japan

Laterality in the DTI indices of the corticospinal tract (CST) of the brain and the spinal cord and their variation with handedness were evaluated in 8 left handers and 8 age- and gender-matched right handers. The DTI indices were compared across the two sides and between the two handers, at various CST levels. The results revealed a similar pattern of asymmetry in the indices between the brain and the spinal cord for both handers. The values differed between the two handers. The knowledge of laterality of the DTI indices and variation with handedness is important in interpretation of the indices.

2112.   Comparison of Relationships Between Two Different White Matter Tracts and Memory Function with Healthy Individuals by Using Diffusion Tensor Tractography
Tetsuo Sato1, Nobuyuki Maruyama2, Toru Hoshida2, and Kotaro Minato1
1Nara Institute of Science and Technology, Ikoma, Nara, Japan, 2National Hospital Organization Nara Medical Center, Nara, Nara, Japan

In this research, we have calculated the correlation coefficient between the DTI parameter of uncinate fasciculus, fornix and WMS-R score. Correlations between DTI measures and memory performance suggest the relationships between the UF, fornix and function in memory tasks lateralization. Our finding matches previous reports on the correlation between FA in the left or L1 in the right UF and performance on visual memory.

2113.   Time Dependence of the Diffusional Kurtosis in the Human Calf Muscle
Anja Maria Marschar1, Tristan Anselm Kuder1, Bram Stieltjes2, and Frederik B. Laun1,2
1Department of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Quantitative Imaging Based Disease Characterization, German Cancer Research Center (DKFZ), Heidelberg, Germany

The diffusional kurtosis (Kapp) and the apparent diffusion coefficient (Dapp) were measured in the human calf muscle. Maps of Dapp and Kapp are shown and the time dependence of both values is reported. A dependence on the diffusion direction is visible for both values, but a higher anisotropy can be observed for Dapp than for Kapp. The kurtosis decreases at longer diffusion time. Absolute values of Kapp in the muscle tissue are much smaller than in white matter tissue in the brain.

2114.   Diffusion Tensor Imaging of the Pediatric Thoracic Spinal Cord Using a Short Echo Time Inner-Field-Of-View Sequence
Devon Middleton1, Feroze Mohamed1, Nadia Barakat2, Scott Faro1, Pallav Shah1, MJ Mulcahey2, Amer Samdani2, and Jürgen Finsterbusch3
1Radiology, Temple University, Philadelphia, PA, United States, 2Shriners Hospital for Children, Philadelphia, PA, United States, 3University Medical Center Hamburg-Eppendorf, Hamburg, Germany

DTI of the pediatric spinal cord (SC) has the potential to provide useful information on white matter integrity and to serve as an important biomarker for spinal cord injury (SCI). This study examines the evaluate the efficacy of an inner-field-of-view DTI sequence for imaging of the thoracic spinal cord in pediatric subjects, both normal and with SCI. Good quality DTI images were successfully collected for six healthy subjects and two subjects with SCI and DTI indices were examined for both groups.

2115.   Diffusion Tensor Measurements in Healthy Human Sciatic Nerve
Christopher D.J. Sinclair1,2, Laura Mancini2,3, and John S. Thornton1,2
1MRC Centre for Neuromuscular Diseases, UCL Institute of Neurology, London, London, United Kingdom, 2Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, London, United Kingdom,3Lysholm Department of Neuroradiology, National Hospital for Neurology and Neurosurgery, London, London, United Kingdom

The sciatic nerve is conveys motor and sensory signals in the lower limbs and abnormalities can include focal tumours or demyelination in peripheral neuropathies. We performed high-resolution anatomical imaging and diffusion tensor imaging (DTI) of the sciatic nerve in healthy subjects at 3T in order to visualize the course of the nerve and derive metrics such as the fractional anisotropy (FA). The mean FA of the nerve was 0.62±0.04, substantially higher than the surrounding muscle (0.22±0.02). FA maps provided good depiction of the course of the nerve and any observed variations may be valuable in monitoring conditions such as Charcot-Marie-Tooth disease.

2116.   MesoFT: Mesoscopic Structure and Orientation with Fiber Tracking
Marco Reisert1, Matthias Weigel1, Els Fieremans2, Valerij G. Kiselev1, and Dmitry S. Novikov3
1Dpt. of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, BW, Germany, 2Center for Biomedical Imaging, Dpt. of Radiology, New York University, New York, NY, United States, 3Center for Biomedical Imaging, Dpt. of Radiology, New York University School of Medicine, New York, NY, United States

As the inverse problem of quantifying tissue structure in every voxel is highly ill-posed, we regularize it by unifying sub-voxel modeling of dMRI signal at the mesoscopic scale with multi-voxel connectivity achieved with global fiber tracking. When MesoFT converges, we obtain the physically motivated fiber directions, connections, voxel-wise neurite densities, and, in principle, can incorporate other mesoscopic structural parameters. In particular, MesoFT yields strong anisotropy of extra-axonal diffusion and a notable tortuosity in corpus callosum.


Monday, 22 April 2013 (16:30-18:30) Exhibition Hall
Fibre PDF's & Tractography

2117.   Non-Negative Spherical Deconvolution for Fiber Orientation Distribution Estimation
Jian Cheng1, Dinggang Shen1, and Pew-Thian Yap1
1Department of Radiology and Biomedical Research Imaging Center (BRIC), The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States

In diffusion MRI, Spherical Deconvolution (SD) was proposed to estimate the fiber Orientation Distribution Function (fODF) based on spherical deconvolution using a single-fiber response function. The peaks or the shape of fODFs can be used to infer local fiber directions. Constrained Spherical Deconvolution (CSD), which takes into consideration the non-negative of the fODF, is the most widely used method among SD variants. Although CSD is capable of accurately determining fiber directions, it is susceptible to false positive peaks especially in the regions with low anisotropy. This is a common drawback of all existing SD-based methods. Moreover, in practice the fODF estimated using CSD still has significant negative values. We propose a method called Non-Negative Spherical Deconvolution (NNSD) to solve the above two problems. Based on a Riemannian framework of ODFs and Square Root Parameterized Estimation for non-negative definite Ensemble Average Propagator, NNSD is formulated such that the non-negativity of the fODF is guaranteed with largely reduced false positive peaks.The synthetic data and real data experiments demonstrated the improvement of NNSD over CSD.

2118.   Effect of Order and Sharpening on Orientation Distribution Function for Identifying Fiber Orientations in Higher Order Tensor Model
Getaneh Bayu Tefera1, Yuxiang Zhou1, and Ponnada A. Narayana1
1Diagnostic & Interventional Imaging, UT Houston, Houston, Texas, United States

High angular resolution diffusion imaging (HARDI) data was analyzed using 4th and 6th order tensors. The orientation diffusion function (ODF) was deconvolved using spherical basis set with order 4 and 6. The performance of this method was demonstrated by performing tractography around the centrum semiovale regions and corpus callosum. Our results indicate that sixth order tensor, convolved with six basis functions is superior to the fourth order tensor in resolving multiple crossing fibers

2119.   Test-Retest Reliability in Fibre Orientation Distribution (FOD) Measurements in HARDI Data
Kai-kai Shen1, Stephen Rose1, Jurgen Fripp1, Katie McMachon2, Greig de Zubicaray3, Nicholas Martin4, Paul Thompson5, Margret Wright4, and Olivier Salvado1
1Australian eHealth Research Centre, CSIRO, Herston, Queensland, Australia, 2Centre for Advanced Imaging, University of Queensland, Brisbane, Queensland, Australia, 3School of Psychology, University of Queensland, Brisbane, Queensland, Australia, 4Queensland Institute of Medical Research, Brisbane, Queensland, Australia, 5Imaging Genetics Center, Laboratory of Neuro Imaging, UCLA, Los Angeles, CA, United States

We evaluated the test-retest reliability for measures based on the fibre orientation distribution (FOD) using constrained spherical deconvolution (CSD). We derived measurements in the peak direction identified from the FOD, and evaluated the test-retest reliability for these FOD peak amplitudes using the intra-class correlation (ICC) coefficient. We visualized the ICC coefficients on the FOD orientation plot. We compared the reliability of measuring the FOD peak amplitudes and the fractional anisotropy (FA) derived from the diffusion tensor imaging (DTI) model.

2120.   Multiple Kernel Spherical Deconvolution and Intrinsic FA of Crossing Fiber Populations
Qiuyun Fan1,2, Erika Spangler3, Xin Hong4, Ha-Kyu Jeong5, Nicole Davis2,6, Laurie E. Cutting2,3, and Adam W. Anderson1,2
1Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, 2Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, 3Department of Special Education, Peabody College of Education and Human Development, Nashville, TN, United States, 4Singapore Bioimaging Consortium, Singapore, Singapore, 5Philips Healthcare, Korea Basic Science Institute, Cheongwon, Korea, 6Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States

Diffusion tensor imaging (DTI) provides valuable information about neuronal tissues, such as fractional anisotropy (FA), but is limited to single-fiber populations. High angular resolution diffusion imaging (HARDI) methods have been developed to reveal complex white matter structures. The conventional spherical deconvolution approaches do not allow for estimates of fiber-specific response kernels in the case of crossing fibers. The multiple kernel spherical deconvolution (MKSD) method can resolve the orientations of multiple fiber populations and provide estimates of the diffusion properties intrinsic to each fiber. In this work, we developed fiber tracking algorithms based on MKSD fiber orientation distribution functions and studied the stability of the fiber-specific FA estimates obtained.

2121.   A Separable Approximation to DSI Deconvolution
Michael Paquette1 and Maxime Descoteaux2
1SCIL, Universite de Sherbrooke, Sherbrooke, Quebec, Canada, 2SCIL, Université de Sherbrooke, Sherbrooke, Quebec, Canada

The q-space truncation induce in the classical acquisition scheme of Diffusion Spectrum Imaging leads to a modified version of the diffusion propagator. That modification can be inverted by deconvolution methods. This work present a separable deconvolution approximation to get better propagator. Those better propagators leads to more physically meaningful diffusion space metric and sharper orientation distribution functions.

2122.   RubiX: Combining Spatial Resolutions for Bayesian Inference of Crossing Fibres in Diffusion MRI
Stamatios N. Sotiropoulos1, Saad Jbabdi1, Jesper L. Andersson1, Mark W. Woolrich1,2, Kamil Ugurbil3, and Timothy E.J. Behrens1
1FMRIB Centre, University of Oxford, Oxford, United Kingdom, 2Oxford Centre for Human Brain Activity (OHBA), University of Oxford, Oxford, United Kingdom, 3Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

The trade-off between signal to noise ratio and spatial specificity governs the choice of spatial resolution in diffusion-weighted magnetic resonance imaging. We present an approach for tackling this trade-off by combining data acquired both at high and low spatial resolution. We combine all data into a single Bayesian model to estimate the underlying fibre patterns, therefore, combining the benefits of each acquisition. We show that fibre crossings at the highest spatial resolution can be inferred more robustly using this model compared to a simpler model that operates only on high-resolution data, when both approaches are matched for acquisition time.

2123.   Improved Angular Resolution with GQI2: A New Diffusion Imaging Q-Space Cartesian Lattice Reconstruction Method
Ian Nimmo-Smith1, Frank Fang-Cheng Yeh2, and Eleftherios Garyfallidis3
1MRC Cognition and Brain Sciences Unit, Cambridge, Cambridgeshire, United Kingdom, 2Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, United States, 3University of Cambridge, Cambridge, Cambridgeshire, United Kingdom

GQI2 is a new non-parametric method for reconstruction of diffusion imaging data acquired with Q-space cartesian lattice design. Using simulations and human data we show it has superior ability to resolve angular directions in voxels with two or three crossing fiber directions. GQI2 also has efficiency advantages over diffusion spectrum imaging (DSI) in terms of computer memory and computation time.

2124.   Cortical Fiber Insertions and Automated Layer Classification in Human Motor Cortex from 9.4T Diffusion MRI
Matteo Bastiani1,2, Ana-Maria Oros-Peusquens2, Daniel Brenner2, Klaus Moellenhoff2, Arne Seehaus1,3, Avdo Celik2, Jörg Felder2, Andreas Matusch2, Ralf Galuske3, Hansjürgen Bratzke4, Nadim Jon Shah2,5, Rainer Goebel1, and Alard Roebroeck1
1Department of Cognitive Neuroscience, Maastricht University, Maastricht, Limburg, Netherlands, 2Institute of Neuroscience and Medicine (INM-4), Research Centre Jülich, Jülich, Nordrhein-Westfalen, Germany,3Department of Biology, TU Darmstadt, Darmstadt, Hesse, Germany, 4Department of Forensic Medicine, Faculty of Medicine, JWG-University, Frankfurt/Main, Hesse, Germany, 5Faculty of Medicine, JARA, RWTH Aachen University, Aachen, Germany

Ultra-high resolution diffusion weighted imaging (DWI) on ex vivo tissue represents a unique tool to investigate human brain anatomy at a microscopic scale. This study focuses on two separate aspects which can be derived from high isotropic resolution HARDI data analysis on post mortem human tissue: i) we reconstruct and analyze the short association fibers connecting human motor and premotor area and fanning cortical insertions in the gyral crown and ii) we distinguish the majority of cortical layers by automatic clustering of their diffusion characteristics. Both aspects are validated using myelin stains of the sectioned tissue.

2125.   Imaging the Grid Structure of the Brain with DSI and QBI with the 3T Connectom Instrument: Conditional Validation of in vivo MRI Tractography in Humans
Van J. Wedeen1, Ruopeng Wang1, Timothy G. Reese1, Thomas Witzel1, Julian Cohen-Adad2, Bruce R. Rosen1, and Lawrence L. Wald1
1Martinos Center for Biomedical Imaging, Mass General Hospital, Harvard Medical School, Charlestown, MA, United States, 2Department of Electrical Engineering, Institute of Biomedical Engineering, Ecole Polytechnique de Montreal, Montreal, Quebec, Canada

It has been recently shown that the fiber pathways of the brain follow a natural curvilinear coordinate system, and being vanishingly improbable, this finding is conditionally self-validating. To test these results in human subjects, we obtained Q-ball and diffusion spectrum MRI and with a simple automated procedure mapped their grid structure. Grid structure was observed widely in the brain regions with all diffusion methods, though different methods emphasized different structures. This study indicates that grid structure is readily obtained in humans, and offers a promising strategy for tractography validation and the mapping of brain structure.

2126.   Which Blind Tract Clustering Method Is Most Robust to False Positives?
Mark Drakesmith1, John Evans1, Anthony David2, and Derek Jones1
1CUBRIC, Cardiff University, Cardiff, Wales, United Kingdom, 2Institute of Psychiatry, Kings College London, London, United Kingdom

The effect of false positives on the performance of blind tract clustering is unclear. From an idealised dataset of 6 pre-defined bundles, various distance metrics and clustering methods were tested across varying FP-rates by substituting a random proportion of ‘true’ tracts with FPs. Most methods deteriorate gradually with noise. Affinities computed from maximum (Hausdorff) and endpoint distances were most robust to noise. These methods showed FP misclassification were concentrated on the smallest fibre bundle while other methods showed more diffuse misclassification across adjacent bundles. These two distance metrics are therefore best for clustering noisy tractography datasets.

2127.   Quantitative Fiber Bundle-Driven Analysis of Diffusion MRI Data
Christian Ros1,2, Daniel Guellmar1, Martin Stenzel2, Hans-Joachim Mentzel2, and Jürgen R. Reichenbach1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, TH, Germany, 2Pediatric Radiology, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, TH, Germany

With this contribution, we presented a new method for the analysis of DTI data sets that uses fiber bundles to enhance the quantitative analysis. By utilizing fiber bundles the occurrence of adverse interpolation effects at the boundaries of white matter structures as a result of the non-linear spatial normalization is prevented. The method was used to assess hemispheric differences in selected fiber bundles using FA maps of 46 healthy volunteers. A statistical analysis was performed and correction methods were employed to deal with statistical errors. In various bundles, statistically significant differences were observed that are in line with the literature.

2128.   Probabilistic Atlas of the Adult Human Brain White Matter
Anna Varentsova1, Shengwei Zhang2, and Konstantinos Arfanakis2
1Physics, Illinois Institute of Technology, Chicago, IL, United States, 2Biomedical Engineering, Illinois Institute of Technology, Chicago, IL, United States

Digital human brain white matter (WM) atlases play an important role in brain imaging research. Existing WM atlases have been generated either based on anatomical landmarks, thus mixing tracts with substantially different roles, or using DTI tractography, which fails in regions with crossing fibers. The purpose of this study was to develop a probabilistic WM atlas of the adult human brain by performing probabilistic tractography on an artifact-free high angular resolution diffusion imaging (HARDI) brain template constructed in ICBM-152 space. Presented preliminary results show that the information contained in the new atlas is in agreement with known anatomy.

2129.   Development of a Comprehensive Digital Human Brain Atlas
Shengwei Zhang1 and Konstantinos Arfanakis1
1Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, IL, United States

A comprehensive digital human brain atlas was generated in this work. The atlas contains high quality, artifact-free anatomical and diffusion MRI data, and detailed WM and GM labels, in the same space (ICBM-152). The atlas also contains a number of supporting maps of quantities describing the quality of the information provided in different brain structures. The new resource provides a flexible reference frame for integration of macro-structural, micro-structural and functional information about the human brain.

2130.   A White Matter Tract Atlas Based on a Diffusion Spectrum Imaging (DSI) Template
Yu-Chun Lo1, Yu-Jen Chen1, Yung-Chin Hsu1, and Wen-Yih Isaac Tseng1,2
1Center for Optoelectronic Biomedicine, National Taiwan University College of Medicine, Taipei, Taipei, Taiwan, 2Department of Medical Imaging, National Taiwan University Hospital, Taipei, Taipei, Taiwan

In this study, a standard procedure of tractography was used to develop an atlas of fiber tracts of the whole brain. This procedure entailed a diffusion spectrum imaging (DSI) template on which interested fiber pathways and their ROIs were determined and validated by experts. A total of 107 major white matter tracts were reconstructed. Based on this atlas, a template-based approach was proposed to enable an automated analysis of the microstructural integrity of the tracts identified in the atlas. The atlas and the automated tract analysis method may facilitate the connectome study in a large cohort.

2131.   3D Visualisation of Connectomes Using Streamtubes
Kerstin Pannek1, Roslyn Boyd1, and Stephen Rose2
1The University of Queensland, Brisbane, Queensland, Australia, 2The Australian E-Health Research Centre, CSIRO, Brisbane, Australia

Connectomes are typically represented in matrix form. To improve visual assessment of the connectome, we suggest the use a streamtube representation of connections. Representation of connections contained in the connectome using streamtubes allows visualization of confidence in the existence of a connection (streamline number) and local attributes of the connections (e.g. FA). Tube thickness, colour and opacity can be fine-tuned for optimized visualization of cortical or deep structures. The opacity and colour of individual streamtubes can be adjusted to highlight subsets of connections, such as connections of altered connectivity.

2132.   Whole-Brain Neighbourhood Tractography
Kiran K. Seunarine1, Jonathan D. Clayden2, and Christopher A. Clark2
1Imaging and Biophysics Unit, UCL Institute of Child Health, London, United Kingdom, 2Imaging and Biophysics Unit, University College London, London, United Kingdom

Tractography allows the probing of brain connectivity. Limitations of the standard approaches are that they can be time consuming, require good anatomical knowledge and can be prone to false-positives. Neighbourhood tractography (NT) overcomes these limitations by using a priori information about the expected path of the tract through the brain. This work introduces a whole-brain extension to the NT algorithm to overcome some of the limitations of the method. We demonstrate the approach by segmenting four white-matter tracts. The segmentations show clear differences over single-seed NT, including fewer false-positives and a greater extent to the segmentation.

2133.   Functional Connectivity Suggests Mean Pathway Radial Diffusivity as a Robust Metric of Anatomic Connectivity
Mark J. Lowe1, Ken E. Sakaie1, Katherine Koenig1, Lael Stone2, Robert A. Bermel3, and Micheal D. Phillips1
1Imaging Institute, Cleveland Clinic, Cleveland, OH, United States, 2Neurologic Institute, Cleveland Clinic, Cleveland, OH, United States, 3Neurologic Institute, The Cleveland Clinic, Cleveland, OH, United States

There are several diffusion and fiber tracking-related measures that are used as metrics of functional connectivity. Many of these depend on the tracking algorithm. This makes it difficult to compare different studies. We propose a very simple tensor-based measure as a robust metric of anatomic connectivity that can easily be combined with different tracking algorithms and results in a metric that can be compared across studies.

2134.   Group-Representative Partitions of Human Brain Structural Networks
Alessandra Griffa1,2, Richard Betzel3, Kim Q. Do4, Philippe Conus5, Patric Hagmann1,6, and Jean-Philippe Thiran1,6
1Signal Processing Laboratory (LTS5), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Vaud, Switzerland, 2Department of Radiology, University Hospital Center (CHUV) and University of Lausanne (UNIL), Lausanne, Vaud, Switzerland, 3Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States, 4Center for Psychiatric Neurosciences, Lausanne University Hospital (CHUV) and University of Lausanne, Lausanne, Vaud, Switzerland, 5Department of Psychiatry, Lausanne University Hospital (CHUV), Lausanne, Vaud, Switzerland, 6Department of Radiology, Univerity Hospital Center (CHUV) and University of Lausanne (UNIL), Lausanne, Vaud, Switzerland

Diffusion MRI, tractography and graph analysis allowed to characterize the brain structural architecture as a small-world, hierarchically modular network. The study of the brain modular topology is raising new interest, and could be a key approach for the understanding of neurodevelopmental disorder. In this framework, it is important to individuate representative partitions for whole groups of subjects. In this work we use information theory-derived measures to quantify the inter-subjects variability of structural network modular decomposition, and we propose different approaches (and particularly the consensus clustering algorithm) to individuate a group-representative partition.

Evidence for the Improved Biological Interpretability of White Matter Connectivity Derived Following Tractogram Filtering Using SIFT
Robert E. Smith1, Jacques-Donald Tournier1, Fernando Calamante1, and Alan Connelly1
1Brain Research Institute, Florey Institute of Neuroscience and Mental Health, Heidelberg, Victoria, Australia

SIFT (Spherical-deconvolution Informed Filtering of Tractograms) has recently been proposed as a method for improving the correspondence between a whole-brain fibre-tracking reconstruction and the underlying diffusion data. Here we evaluate its utility for quantitative tractography analysis (such as connectomics) by comparing properties of tractography reconstructions before and after application of SIFT to those estimated from post-mortem brain dissection.

2136.   How Well Does the Residual Bootstrap Predict Scan-Rescan Repeatability of Spherical Deconvolution Diffusion MRI?
Jennifer S.W. Campbell1 and Bruce G. Pike2
1McConnell Brain Imaging Centre, McGill University, Montreal, Quebec, Canada, 2McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada

The purpose of this study was to evaluate how well the residual bootstrap statistical technique predicts the variability in scan-rescan estimates of fibre orientation, using spherical deconvolution diffusion MRI. Here, we evaluated how well the fibre orientations obtained from different, coregistered datasets in the same subject fit the fibre probability distribution function obtained from the residual bootstrap technique. For major fibre tracts (i.e., FA>0.3), the correspondence between the observed variability in the fibre orientations and the variability predicted by the bootstrap was very good. For low FA, the residual bootstrap underestimates the scan-rescan repeatability.

2137.   Explore the Brain White Matter Networks in Real-Time: Multi-Sticks Fiber Tracking
Maxime Chamberland1 and Maxime Descoteaux1
1Computer Science, Université de Sherbrooke, Sherbrooke, Québec, Canada

Real-time fiber tractography consists in achieving the computation and simultaneous display of fiber tracts. By doing so, this permits the user to interactively tweak any parameters involved in the tracking process and therefore see the effect of each adjustement made on the resulting fibers. For neurosurgical planning, this feature is crucial since giving a pre-computed set of tracts in the hands of neurosurgeon can hide important information, which could have been explored and tuned in real-time.

2138.   A Diffusion MRI Resource of 80 Age-Varied Subjects with Neuropsychological and Demographic Measures
Ryan P. Cabeen1, Ksenia Andreyeva2, Mark E. Bastin2, and David H. Laidlaw1
1Brown University, Providence, RI, United States, 2University of Edinburgh, Edinburgh, United Kingdom

The primary purpose of this work is to provide a resource of high angular resolution diffusion MRI datasets of 80 normal volunteers aged 25-64 together with neuropsychological testing data spanning general cognitive ability, memory, and information processing speed. To support the value of these data, we demonstrate statistical correlations between age and tract-based metrics calculated automatically from the data. The metrics are a function of fiber count, length, diffusion rate, and diffusion anisotropy; the statistical relationship to age was modeled with linear regression.

2139.   Tractography and Connectivity Analysis with the TractoR Software Package
Jonathan D. Clayden1, Susana Munoz Maniega2, Amos J. Storkey3, Martin D. King1, Mark E. Bastin4, and Christopher A. Clark1
1Institute of Child Health, University College London, London, United Kingdom, 2Division of Clinical Neurosciences, University of Edinburgh, Edinburgh, United Kingdom, 3School of Informatics, University of Edinburgh, Edinburgh, United Kingdom, 4Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom

This abstract introduces and describes TractoR, a freely available software package for MR image analysis implemented in R. The package has a particular emphasis on tractography and connectivity analysis.

2140.   A Comparison of Two Automated and Probabilistic Tract Segmentation Methods
Jonathan D. Clayden1, Susana Munoz Maniega2, Mark E. Bastin3, and Christopher A. Clark1
1Institute of Child Health, University College London, London, United Kingdom, 2Division of Clinical Neurosciences, University of Edinburgh, Edinburgh, United Kingdom, 3Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom

In this work, we compare two freely available, probabilistic and automated methods for segmenting white matter tracts from diffusion MRI data.

2141.   Connectivity-Based Segmentation of the Precuneus in Individual Adolescent Rhesus Macaque DTI Data.
Elizabeth Zakszewski1, Nagesh Adluru1, Ned Kalin1, and Andrew L. Alexander1
1University of Wisconsin-Madison, Madison, WI, United States

Connectivity-based segmentation of the precuneus, an important connectome hub, is performed on DTI data of young rhesus monkeys. We observe how the proportion of connections from the precuneus to functionally different brain regions (limbic, somatosensory, and visual) shifts with increasing age. This gives us valuable information for creating models of brain development.

2142.   Correlation of Imaging Connectivity with Electrophysiological Connectivity Using Intracranial Electrodes
Stephen Jones1, Erik B. Beall2, Jorge A. Gonzalez-Martinez1, Blessy Mathew1, Dileep Nair1, Imad Najm1, Michael Phillips1, Ken E. Sakaie1, and Myron Zhang1
1Cleveland Clinic Foundation, Cleveland, OH, United States, 2Cleveland Clinic, Cleveland, OH, United States

We study the correlation between diffusion weighted imaging (DWI) measures of structural brain connectivity and electrophysiological connectivity obtained from intracranial electrodes in epilepsy patients. We have collected data from four patients, each with around 150 electrode contacts implanted, and our analysis suggests that the correlation between DWI-based connectivity and electrophysiological connectivity is only modest and still uncertain, which may shape how we interpret DWI data and results.

2143.   Spatial Resolution Requirements for Diffusion Tensor Imaging of Fornix
Ken E. Sakaie1, Mark J. Lowe1, Katherine Koenig1, Robert A. Bermel2, Lael Stone2, and Michael Phillips1
1Imaging Institute, The Cleveland Clinic, Cleveland, OH, United States, 2Mellen Center for Multiple Sclerosis Treatment and Research, The Cleveland Clinic, Cleveland, OH, United States

As the primary efferent of hippocampus, diffusion tensor imaging (DTI) of fornix has potential as a biomarker for memory-related cognitive decline. As commonly-used spatial resolution for DTI risks partial volume averaging with surrounding CSF spaces, increases in diffusivity associated with disease that simply result from atrophy may be misinterpreted as change in tissue integrity. Here, we examine the use of high spatial resolution DTI of fornix to avoid partial volume averaging. The results suggest that 1mm isotropic voxels are sufficient for characterizing fornix in healthy controls but may be inadequate in multiple sclerosis patients experiencing atrophy.


Monday, 22 April 2013 (16:30-18:30) Exhibition Hall
Arterial Spin Labeling

2144.   Longitudinal Study of Cerebral Blood Flow Measurements in Normals Using Pseudocontinuous and Velocity-Selective Arterial Spin Labeling
Zungho Zun1, Deqiang Qiu1, Jarrett Rosenberg1, and Greg Zaharchuk1
1Radiology, Stanford University, Stanford, CA, United States

Arterial spin labeling (ASL) allows for quantitative measurements of cerebral blood flow (CBF), enabling longitudinal observation of CBF in the same subjects. In this work, monthly CBF measurements were performed in five normal volunteers for six months using pseudocontinuous ASL (PCASL) and velocity-selective arterial spin labeling (VSASL). Global CBF measurement of gray matter for six months was, on average, 61 ± 5 ml/100 g /min with PCASL and 44 ± 4 ml/100 g/min with VSASL. While CBF measurement with PCASL showed good agreement with literature values, both methods showed similar coefficient of variation.

2145.   Comparing 3D Velocity-Selective Arterial Spin Labeling to 3D Pseudocontinuous Arterial Spin Labeling
Zungho Zun1, Ajit Shankaranarayanan2, and Greg Zaharchuk1
1Radiology, Stanford University, Stanford, CA, United States, 2GE Healthcare, Menlo Park, CA, United States

Velocity-selective arterial spin labeling (VSASL) is a promising method for measuring cerebral blood flow (CBF) in patients with slow or delayed flow. Most previous works on VSASL were demonstrated using 2D imaging, and no previous work reported comparison of VSASL and PCASL, both with 3D imaging and with the same quantification method. In this study, VSASL was combined with 3D image acquisition and was performed in normal volunteers along with 3D PCASL. CBF maps acquired using two methods showed consistent results. Measured signal-to-noise ratio (SNR) from VSASL was about 30% lower than that of PCASL, but was adequate to provide good image quality.

Turbo-QUASAR: A Signal-To-Noise Optimal Arterial Spin Labeling and Sampling Strategy
Esben Thade Petersen1,2, Jill Britt De Vis1, Cornelis A.T. van den Berg2, and Jeroen Hendrikse1
1Department of Radiology, UMC Utrecht, Utrecht, Netherlands, 2Department of Radiotherapy, UMC Utrecht, Utrecht, Netherlands

In this work an optimal labeling and acquisition scheme for Arterial Spin Labeling is proposed. Repeated pulsed labeling during a multi time-point Look-Locker readout, allow full-brain acquisition while keeping optimum perfusion signal. The method gained 2-5 times the temporal SNR as compared to existing pCASL sequences while at the same time providing information about auxiliary parameters needed for quantification such as bolus arrival time, tissue T1, and arterial input function and blood volume. The method which is an extension of the model-free QUASAR ASL sequence was dubbed Turbo-QUASAR and it will boost any pulsed labeling approach (Pulsed, Velocity- or Acceleration-selective).

2147.   Thin Slab Pseudo-Continuous Arterial Spin Labeling
Weiying Dai1 and David C. Alsop1
1Radiology, Beth Israel Deaconess Medical Center & Harvard Medical School, Boston, MA, United States

Thin slab Flow-sensitive alternating inversion recovery (FAIR) arterial spin labeling (ASL) can be advantageous when the geometry or transit delay of the arterial supply is not known, but FAIR has reduced signal compared to continuous labeling methods. Here, a modification of pseudo-continuous labeling that achieves labeling very close to both sides of a slice is presented. Labeling RF is applied centered on the slab and labeling planes on both sides of the slice are created. The performance of this approach is evaluated in single slice perfusion imaging of the brain.

Suppression of Free Fluid Perfusion Artefacts in Velocity Selective ASL Using a BIR-4 T2-FLAIR Preparation
James A. Meakin1,2, Natalie L. Voets1, Thomas W. Okell1, and Peter Jezzard1
1FMRIB Centre, University of Oxford, Oxford, United Kingdom, 2Department of Oncology, University of Oxford, Oxford, United Kingdom

Velocity selective arterial spin labeling (VSASL) is not diffusion balanced between the tag and control condition, which causes artefacts from free fluids to appear as positive signal in the perfusion weighted subtractions. This affects both the healthy brain (CSF) and in tumors (inflammation response, edema). Here we present a T2-FLAIR method to null long T1/T2 spins at the time of the velocity selective tag using a segmented BIR-4 inversion. We find that this method increases the accuracy of perfusion measurements with VSASL in healthy grey matter by reducing CSF partial volume effects.

2149.   Pulmonary Blood Flow Measurement Using Velocity-Selective Arterial Spin Labeling at 3.0T
Jia Guo1 and Eric C. Wong1
1University of California San Diego, La Jolla, California, United States

In this study, we demonstrated that it is feasible to use Velocity-Selective ASL (VSASL) to measure pulmonary blood flow (PBF) at 3.0 T with bSSFP and cardiac gating. Comparing with FAIR, the intravascular signal of VSASL is minimized by choosing a proper cutoff velocity (2cm/s in this study) without affecting the quantification, therefore providing a less biased thus more accurate estimate of PBF. We expect VSASL to benefit from the longer T2/T2* at a lower field (1.5 T) on measurement of PBF.

2150.   ASL-Based Time-Resolved MRA Acquiring Labeled and Control Images in a Single Look-Locker-Like Acquisition
Yuriko Suzuki1, Noriyuki Fujima2, Hiroyuki Sugimori2, Tetsuo Ogino1, and Marc Van Cauteren3
1Philips Electronics Japan, Minato-ku, Tokyo, Japan, 2Hokkaido University Hospital, Sapporo, Hokkaido, Japan, 3Philips Healthcare Asia Pacific, Minato-ku, Tokyo, Japan

Hemodynamic information is useful for the accurate diagnosis, effective treatment and follow-up for numerous neurovascular diseases. Recently developed non-contrast-enhanced time-resolved 4D MRA using arterial spin labeling (ASL) methods achieve both high spatial and temporal resolution with 3D coverage. However, these methods require labeled and control images to make the subtracted image, doubling the scan time. We present a new non-contrast-enhanced time-resolved 4D MRA, in which contrast and labeled images are acquired in a single Look-Locker like acquisition, making scan time half compared to the conventional ASL method.

2151.   Theoretical and Practical Investigation of Acoustic Noise Level Reduction in Pseudo-Continuous Arterial Spin Labeling
Magdalena Sokolska1, Aaron Oliver-Taylor1, Xavier Golay2, and David Thomas1
1Department of Brain Repair & Rehabilitation, UCL Institute of Neurology, London, UK, United Kingdom, 2Department of Brain Repair & Rehabilitation, University College London, London, UK, United Kingdom

Arterial Spin Labeling (ASL) is a non-invasive imaging technique for quantifying blood perfusion in tissue. Pseudo-continuous ASL has recently emerged as the method of choice. However, concern has been raised about acoustic noise levels experienced by patients undergoing pCASL scans, leading to patient discomfort. This is especially a concern in imaging unsedated infants or elderly patients, where exposure to long lasting acoustic noise can increase patient unease in the scanner. This study investigates the Sound Pressure Level (SPL) produced by the pCASL sequence and how it can be reduced without significantly changing the inversion efficiency.

2152.   Silent Pseudo-Continuous Arterial Spin Labeling
Michael Helle1 and Tim Nielsen1
1Philips Research Laboratories, Hamburg, Germany

Conventional pseudo-continuous arterial spin labeling (pCASL) employs trapezoidal gradient waveforms and requires high gradient strengths in combination with high slew rates for sufficient labeling of flowing blood spins, which results in mechanical vibrations and a high acoustic noise level. In this study, possibilities are presented on how to reduce the acoustic noise level and the mechanical strain of a pCASL sequence, either by optimizing the labeling interval duration or by applying a sinusoidal gradient waveform for the labeling sequence or both.

2153.   Active Head Coil Detuning: A Method to Reduce SAR in CASL at 7T
Randall B. Stafford1,2, Se-Hong Oh1,2, Myung-Kyun Woo3, Tiejun Zhao4, Kyoung-Nam Kim3, Young-Bo Kim3, Zang-Hee Cho3, John A. Detre1,2, and Jongho Lee1,2
1Radiology, University of Pennsylvania, Philadelphia, PA, United States, 2Center for Functional Neuroimaging, University of Pennsylvania, Philadelphia, PA, United States, 3Neuroscience Research Institute, Gachon University, Incheon, Incheon, Korea, 4Siemens Healthcare USA, University of Pittsburgh, Pittsburgh, PA, United States

Arterial spin labeling has the dual benefit of increased spin polarity and elongation of the T1 relaxation time of arterial blood at 7T. In order to realize these benefits at 7T, specific absorption rate limits must be mitigated. One way to reduce the SAR deposition is to eliminate the need for RF power during ASL control acquisitions. Here, we use a novel ASL head/labeling coil system with active detuning to eliminate magnetization transfer effects during labeling, thereby allowing us to remove the control RF. This reduces the SAR deposition by almost 50%, and allows for shorter TRs. We demonstrate the utility of this system for CASL in healthy volunteers with a SAR-minimum TR under 7 seconds.

2154.   Vascular Territory Segmentation Using Mutual Clustering in Image and Label Space
Youngkyoo Jung1,2, Megan E. Johnston2, Christopher T. Whitlow1,3, and Joseph A. Maldjian1
1Radiology, Wake Forest School of Medicine, Winston-Salem, North Carolina, United States, 2Biomedical Engineering, Wake Forest School of Medicine, Winston-Salem, North Carolina, United States, 3Translational Science Institute, Wake Forest School of Medicine, Winston-Salem, North Carolina, United States

Pseudo-continuous ASL (PCASL) based vascular territory mapping enables the detection of source arteries. An automated vascular territory segmentation using connectivity information from both image space and label space is proposed. The algorithm was tested with data obtained at two locations with middle cerebral artery branching. The algorithm demonstrates the ability to resolve neighboring sources into separate territories with minimal computational burden.

2155.   Analysis of Localization Error of Decoded Vascular Sources in Random Vessel Encoded Arterial Spin Labeling
Yi Dang1, Jia Guo2, Jue Zhang1,3, and Eric C. Wong4
1Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, Beijing, China, 2Department of Bioengineering, University of California San Diego, San Diego, California, United States, 3College of Engineering, Peking University, Beijing, Beijing, China, 4Department of Radiology and Psychiatry, University of California San Diego, San Diego, California, United States

Random Vessel-encoded arterial spin labeling (R-VEASL) can be used to uniquely identify the locations of the source arteries in the tagging plane. However, localization of the decoded vascular sources is accurate in most but not all cases. In this work, the causes of this have been investigated. In our data, motion during the scan did not dominate the errors in the detecting process. The estimation of vessel locations was only slightly improved by selective filtering of data. In some cases, the detected vessel locations correlated closely with the vascular anatomy several millimeters inferior to the nominal tagging plane.

2156.   Investigation of the Theoretical Signal Model Used in Random Vessel Encoded Arterial Spin Labeling
Yi Dang1, Jia Guo2, Jue Zhang1,3, and Eric C. Wong4
1Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, Beijing, China, 2Department of Bioengineering, University of California San Diego, San Diego, California, United States, 3College of Engineering, Peking University, Beijing, Beijing, China, 4Department of Radiology and Psychiatry, University of California San Diego, San Diego, California, United States

In Random vessel encoded arterial spin labeling (R-VEASL), the correlation coefficient between acquired perfusion signal data and the theoretical signal model was used to detect the vessel locations. In this work, the accuracy of the theoretical signal model derived from Bloch simulation that is currently used to estimate vessel location in R-VEASL has been demonstrated. The theoretical model appears to generally fit the data well, and is insensitive to vessel velocity selection. This suggests that the method is robust to assumed velocity for the purpose of vessel detection, but that the data likely cannot be used to estimate flow velocities.

Accelerated 3DPCASL Using Compressed Sensing
Li Zhao1, Samuel W. Fielden1, Xiao Chen1, John P. Mugler, III2, Josef Pfeuffer3, Manal Nicolas-Jilwan2, Max Wintermark2, and Craig H. Meyer1
1Biomedical Engineering, University of Virginia, Charlottesville, Virginia, United States, 2Radiology, University of Virginia, Charlottesville, Virginia, United States, 3Siemens, Erlangen, Germany

Low SNR in ASL limits the achievable spatial resolution and the accuracy of perfusion maps. Dynamic ASL is time-consuming and also suffers from low SNR. Compressed sensing can improve image quality by enforcing spatial-domain sparsity. Compressed sensing can also enforce time-domain sparsity in dynamic ASL. Volunteer data are shown to demonstrate CS performance on single PLD PCASL images and multiple dynamic frames. The results show image SNR and image quality improvement. More importantly, the estimated CBF becomes more accurate and stable with compressed sensing image reconstruction.

2158.   Accelerating Arterial Spin Labeled Perfusion Imaging Using Compressed Sensing
Yihang Zhou1,2, Jie Zheng3, Dong Liang4, and Leslie Ying1,2
1Electrical Engineering, University at Buffalo, Buffalo, NY, United States, 2Department of Biomedical Engineering, University at Buffalo, Buffalo, NY, United States, 3Department of Radiology, Washington University, St. Louis, MO, United States, 4Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen, China

Arterial spin labeled (ASL) MRI method has been used as an alternative to first-pass perfusion imaging in assessing end organ perfusion. It has the advantage of avoiding administration of any contrast agent. However, this method is sensitive to motion artifacts due to prolonged data acquisition time for each T1 weighted image. The motion artifacts will greatly degrade the image quality and reduce the accuracy of perfusion measurements. In this study, the feasibility of accelerating ASL acquisition using compressed sensing is investigated. Results on calf muscle and cardiac experiments demonstrate compressed sensing is able to preserve the perfusion information with accelerated acquisition.

2159.   Pulsed Arterial Spin Labeling with Multi-Band Excitation
Tae Kim1, Wanyong Shin2, Erik B. Beall2, Mark J. Lowe2, Tiejun Zhao3, and Kyongtae Ty Bae1
1Radiology, University of Pittsburgh, Pittsburgh, PA, United States, 2Imaging Institute, Cleveland Clinic, Cleveland, OH, United States, 3Siemens Medical Solution USA, INC., Siemens MediCare Healthcare USA, Pittsburgh, PA, United States

Multi-band (MB) excitation for data acquisition was successfully implemented into pulsed arterial spin labeling and evaluated on healthy volunteers at 3T. Perfusion quantification for MB excitation was highly comparable with that of a conventional perfusion acquisition. Our study demonstrates that the MB technique facilitates an accelerated acquisition of high resolution, whole-brain perfusion maps.

2160.   Interleaved Multi-Slab 3D Gradient and Spin Echo for Arterial Spin Labeling
Hiroshi Toyoda1,2, Guoxiang Liu2, Yusuke Morito2, and Yasuyoshi Watanabe1
1RIKEN Center for Molecular Imaging Science, Kobe, Japan, 2National Institute of Information and Communications Technology, Kobe, Japan

A new 3D arterial spin labeling (ASL) acquisition using multi-slab 3D gradient and spin echo (GRASE) was proposed, which shortened scanning time without sacrificing measurement accuracy. We have shown that the ASL imaging based on a multi-slab 3D GRASE sequence provided equivalent results in the absolute quantification of the CBF to that of the single slab sequence. The feasibility of this new multi-slab 3D acquisition approach was demonstrated by its better time efficiency and equivalent quantification accuracy.

2161.   Dual Slice Perfusion Measured with PASL-SIR
Erin K. Englund1, Michael C. Langham1, Cheng Li1, and Felix W. Wehrli1
1Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States

In this work, a traditional pulsed arterial spin labeling (PASL) technique is combined with simultaneous image refocusing (SIR) EPI readout to measure dual-slice perfusion in the leg. PASL-SIR is evaluated by comparing results acquired in the two slices to an otherwise identical single-slice PASL sequence during a series of ischemia reperfusion paradigms in the leg. Time course parameters for the dual-slice PASL-SIR technique are in relative agreement with single-slice-measured perfusion and with literature reported values. Implementation of PASL-SIR in longitudinal studies may improve reproducibility by reducing errors due to subject repositioning.

2162.   Comparison of Water Excitation Versus Fat Saturation in Perfusion MRI - Effects on Lipid Signal, SNR and CBF
Karthik Prabhakaran1, Ryan D. Hopson1, Mark A. Elliott1, Kosha Ruparel1, Raquel E. Gur1, Ruben C. Gur1, and John A. Detre1
1University of Pennsylvania, Philadelphia, PA, United States

The use of frequency-selective fat saturation in EPI based perfusion imaging results in spurious measurements of cerebral blood flow (CBF) if the lipid suppression is poor and inconsistent. Frequency-selective water excitation provided superior lipid suppression and yielded higher CBF measurements when compared to frequency-selective fat-saturation in a spin-echo EPI pseudo-continuous arterial spin labeling (pCASL) application at 3T.

2163.   Comparison of Cerebral Blood Flow and Arterial Transit Time Estimation Methods Using Monte-Carlo Simulation
Megan E. Johnston1, Joseph A. Maldjian2, and Youngkyoo Jung1,2
1Biomedical Engineering, Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States, 2Radiology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States

The arterial transit time is a valuable metric for both optimizing arterial spin labeling parameters and as a complementary diagnostic tool in cerebrovascular disease. Simulations were performed for three arterial spin labeling based methods in order to compare their efficiencies in estimating the arterial transit time and cerebral blood flow. The three methods included a method with variable TR, Hadamard-encoded ASL, and a method using Look-Locker acquisition. The variable TR method produced the lowest error in arterial transit time estimation and the lowest percentage error in cerebral blood flow measurement over the range of arterial transit times simulated.

2164.   Optimal PLD Design and Maximum Likelihood CBF Estimation for Dynamic PCASL with Rician Noise
Li Zhao1 and Craig H. Meyer1,2
1Biomedical Engineering, University of Virginia, Charlottesville, Virginia, United States, 2Radiology, University of Virginia, Charlottesville, Virginia, United States

Noise in low SNR ASL images is more accurately modeled as Rician rather than Gaussian. Least squares estimation is typically used in ASL, but this results in a biased estimate with Rician noise. This work describes a new maximum likelihood (ML) estimator and an optimal post-label delay (PLD) design for dynamic ASL assuming Rician noise. To verify the performance of CBF estimation, a simulation is performed based on low SNR dynamic ASL signal. The results show that the new ML estimator provides unbiased estimation and that optimal PLD design can reduce the variance of CBF estimation significantly.

2165.   Alpha-Corrected Pseudo-Continuous Arterial Spin Labeling for Robust Quantification of Cerebral Blood Flow
David D. Shin1, Ho-Ling Liu2, and Thomas T. Liu1
1Center for Functional MRI, University of California, San Diego, La Jolla, CA, United States, 2Chang Gung University, Taoyuan, Taiwan

We present a novel PCASL technique for correcting compromised inversion efficiency resulting from off-resonance effects and gradient imperfections at the tagging plane. The implemented sequence acquires the ASL signal using 8 RF phase offsets during the first 32 reps then switches to the regular tag/control mode to acquire the conventional PCASL signal. The inversion response curves from the first mode is used to estimate the tagging efficiencies for the main feeding arteries, which are in turn used during the quantification step to correct for underestimated CBFs associated with regular PCASL. The gray matter CBFs calculated from alpha-corrected PCASL are compared to those from OptPCASL which restores inversion efficiency but requires additional calibration scans.

2166.   Robust T2 Measurements for Multi-TI Arterial Spin Labeling
Johanna Kramme1 and Matthias Günther1,2
1Fraunhofer MEVIS, Bremen, Germany, Germany, 2Faculty of Physics and Electronics, University of Bremen, Bremen, Germany, Germany

Precise arterial spin labeling T2 measurements are challenging because they are influenced by many factors like the choice of crusher gradients, the refocusing flip angle, and the number of fitted echoes. When extended to multi-TI T2 measurements, SNR at longer inflow times can be critical, especially if scan time limits the number of image averages. Here, a robust and reliable multi-TI T2 acquisition and fitting routine is presented that is fast enough to be implemented in clinical routine to determine T2 values for every individual patient. The T2 values could then be incorporate in two compartment models for permeability quantification.

2167.   Sensitivity to Bolus Dispersion in Continuous and Pulsed Multi-TI ASL Techniques
Roman Fleysher1, Mark E. Wagshul1, Michael L. Lipton1, and Craig A. Branch1
1Gruss Magnetic Resonance Research Center, Department of Radiology, Albert Einstein College of Medicine, Bronx, NY, United States

Both Gaussian dissipation and single compartment Kety models are found to be inadequate for description of ASL experiments for two major reasons: 1) bolus disperses continuously as it travels down the vascular tree and must be modeled as such all the way to the capillary level and 2) exchange through the capillary wall is not instantaneous. We use more realistic simulations with continuous bolus dispersion and restricted water permeability of capillary walls to ascertain sensitivity of CASL, ITS-FAIR and Quasar ASL techniques to bolus dispersion. Quasar is found to handle bolus dispersion most effectively at 20 degree flip angle.

2168.   Transient Effects in Arterial CBV Quantification
Kathrin Lorenz1, Toralf Mildner1, André Pampel1, and Harald E. Möller1
1Nuclear Magnetic Resonance Unit, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany

Inflow vascular-space-occupancy (iVASO) is a non-invasive method for the quantification of absolute arterial cerebral blood volume (aCBV). The present work is purposed to investigate determining factors of aCBV measurement like slow inflow of inverted blood from small vessels and inflow of fresh, i.e. non-inverted, blood in case of short arterial transit times. Transient effects related to the blood delivery by vessels of variable size were addressed by dedicated experiments. Such effects potentially lead to biased values in the aCBV measurement and were shown to vary between different regions in the human brain.

2169.   Delay and Dispersion in the Microvascular Network Due to Laminar Flow with Account for Vessel Bifurcations
Elias Kellner1, Roman Fleysher2, Matthias Günther3, Marco Reisert1, Peter Gall1, and Valerij G. Kiselev1
1Department of Radiology, University Hospital Freiburg, Freiburg, Germany, 2Gruss Magnetic Research Center, Department of Radiology, Albert Einstein College of Medicine, Bronx, NY, United States, 3Institute for Medical Image Computing, Fraunhofer MEVIS, 28359, Germany

Proper account for blood transport is imperative for quantitative analysis of pharmacokinetic and perfusion data in DSC, DCE, ASL MRI and CT/PET. The empirical nature of currently available models hinders prediction of delay and dispersion in higher generations of the vascular tree. We present an analytical framework for solving this problem based on the morphological parameters of vascular networks. Explicit expression with one fitting parameter is obtained for a simple scaling vascular tree. An ASL measurement in large cerebral arteries supports the model, but demonstrates weak disambiguation between several models using this vessel group.

2170.   A Two-Stage General Kinetic Model for Improved Estimation of Brain Tumour Perfusion Using Arterial Spin Labeling
Patrick W. Hales1, Kim P. Phipps2, Ramneek Kaur1, Tina Banks3, and Christopher A. Clark1
1Imaging and Biophysics, University College London, London, London, United Kingdom, 2Neuro-oncology Department, Great Ormond Street Hospital, London, London, United Kingdom, 3Radiology Department, Great Ormond Street Hospital, London, London, United Kingdom

A ‘two-stage’ model for quantification of CBF and arterial volume fraction in dynamic ASL data is presented. The two-stage model provides CBF values in healthy grey matter that are more in line with previously published data from PET studies (compared to standard ‘single stage’ ASL models), due to a reduction in ‘large vessel’ artefacts. Furthermore, the two-stage model is shown to provide a better fit to data collected in paediatric brain tumour patients, and provide novel contrast, in terms of arterial volume maps in and around the tumour region.

2171.   Correlation Between PCASL and DSC Perfusion MRI with and Without Contrast Agent Leakage Correction in Brain Tumors
Feng-Xian Yan1, Alex M. Wong2, and Ho-Ling Liu1,2
1Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taoyuan, Taiwan, 2Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Taoyuan, Taiwan

This study aimed to evaluate whether pseudo-continuous ASL (PCASL) perfusion method is sensitive to leaky vessels in brain tumors by comparing with DSC-MRI with and without leakage correction. Eight patients with contrast-enhancing tumors participated in this study. The results demonstrated that tumor/white matter (WM) CBF ratios obtained from PCASL had significant positive correlation with the leakage-corrected tumor/WM CBV ratios obtained from DSC-MRI(p=0.01), but not with the CBV ratios before correction(p=0.13). This study provides a direct evidence for supporting that using PCASL for evaluation of brain tumor perfusion is advantageous because it is insensitive to contract agent extravasation from tumor vessles.

2172.   Cerebral Blood Flow Quantification from QUASAR ASL by Stable Spline
Marco Castellaro1, Amit Mehndiratta2, Denis Peruzzo1, Gianluigi Pillonetto1, Esben Thade Petersen3, Xavier Golay4, Michael A. Chappell2, and Alessandra Bertoldo1
1Department of Information Engineering, University of Padova, Padova, PD, Italy, 2Institute of Biomedical Engineering, University of Oxford, Oxford, United Kingdom, 3Departments of Radiology and Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands, 4University College London, London, United Kingdom

QUASAR ASL allows the simultaneous estimation of Cerebral Blood Flow (CBF) and the residue function using deconvolution techniques. One vital aspect of quantification process is the estimation of delay between arterial input function and tissue. The error in delay might be propagated to CBF estimation. In this study the performance of a novel deconvolution method, Stable Spline (SS) was compared with the most commonly used method (oSVD) both on simulated and clinical data. SS showed a reliable estimation of delay, CBF along with physiologically realistic residue function compared to oSVD.

2173.   A Novel Efficient Denoising Method for ASL Data: Assessment Using Voxel-Wise Network Analysis
Xiaoyun Liang1, Alan Connelly1,2, and Fernando Calamante1,2
1Brain Research Institute, Florey Institute of Neuroscience and Mental Health, Heidelberg, VIC, Australia, 2Department of Medicine, Austin Health and Northern Health, University of Melbourne, Melbourne, VIC, Australia

The SNR of fMRI images is critical for functional connectivity studies. Although ASL has some advantages over BOLD fMRI, the reliability for detecting networks may be compromised due to its intrinsic low SNR. In this study, we proposed a denoising method combining block-wise non-local means and dual-tree complex wavelet transform to enhance the SNR of ASL images. Simulations show that the proposed method was superior to discrete wavelet transform. The validity of the proposed method has been further confirmed by the more robust detection of functional connectivity from in vivo data. Overall, the proposed method can enhance the SNR of ASL data significantly and thus enable more reliable network detection.

2174.   Arterial Spin Labeling (ASL) Denoising with Markov Random Field (MRF) Optimization
Yongsheng Zhang1 and Ze Wang1
1Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, United States

ASL MRI has an intrinsic low signal-to-noise-ratio, requiring an efficient denoising method. Spatial smoothing is efficient for suppressing random noise but at the expense of a resolution loss. We proposed a resolution preserving ASL denoising method based on the Markov random field theory. Our evaluation results showed that the proposed method can gain up to 4 fold SNR increase while still keep the structural details intact. By contrast, spatial smoothing induced severe blurring effects when a similar level of SNR increase was achieved.

2175.   Performance of Capnia-Derived Regressors and Physiological Noise Correction for ASL Measurement of Cerebral Vasoreactivity to Circulating Gases
Marjorie Villien1,2, Alexandre Krainik3, Julien Bouvier1, Matthias J.P. van Osch4, Laurent Lamalle5, Irène Troprès5, and Jan M. Warnking1
1Grenoble Institut of Neurosciences, INSERM, Grenoble, France, 2Athinoula A. Martinos center for biomedical imaging, Massachusetts General Hospital, Charlestown, Massachusetts, United States, 3Clinique universitaire de neuroradiologie et d'IRM, CHU Grenoble, Grenoble, France, 4Leiden University Medical Center, Leiden, Netherlands, 5SFR1, Université Joseph Fourier, Grenoble, France

Our aim is to compare the performance of a variety of data analysis methods in order to maximize the robustness of ASL CVR mapping in the context of clinical exams and basic and clinical research. Here, we analyzed 56 sessions of ASL vasoreactivity data obtained in patients and healthy subjects using the classical block regressor and regressors based on the physiological state of the individual subjects. We also analyzed the effect of excluding data obtained during the transition periods between capnia levels, and of regressors modeling physiological noise. Regressors based on individual capnia timecourses consistently outperformed standard block regressors.

2176.   ASL Inversion Efficiency for Three Methods and Two Magnetic Fields
Clément S. Debacker1,2, Jan M. Warnking1,3, Jérôme Voiron2, and Emmanuel Luc Barbier3,4
1Team 5: Functional NeuroImaging and Brain Perfusion, Grenoble-Institute of Neuroscience, La Tronche, France, 2MRI, Bruker BioSpin, Ettlingen, Germany, 3U836, INSERM, La Tronche, France, 4Team 5: Functional NeuroImaging and Brain Perfusion, Grenoble Institute of Neurosciences, La Tronche, France

Arterial Spin Labeling (ASL) methods can quantify cerebral blood flow (CBF), but this requires an estimate of the inversion efficiency (IE). The purpose of this study is to estimate IE for three ASL methods (pulsed ASL (PASL), continuous ASL (CASL), and pseudo-continuous ASL (pCASL)) and two magnetic fields in the context of pre-clinical imaging. We also show that shim correction seems to increase IE.

2177.   Perfusion Quantification Using Pseudo-Continuous Arterial Spin Labelling: The Impact of Labelling Efficiency Estimation
Magdalena Sokolska1, Xavier Golay2, and David Thomas1
1Department of Brain Repair & Rehabilitation, UCL Institute of Neurology, London, UK, United Kingdom, 2Department of Brain Repair & Rehabilitation, University College London, London, UK, United Kingdom

Arterial Spin Labelling (ASL) is a non-invasive method allowing quantitative measurement of CBF. Pseudo-continuous ASL (pCASL) is considered one of the best ASL techniques due to its high SNR. However, the accurate and reproducible CBF quantification using this technique can be challenging , because the labelling efficiency of the protons (α), which measures the effectiveness of the magnetic labelling of spins, depends on a number of subject-specific factors. The aim of this study was to compare different methods of labelling efficiency estimation of pCASL and evaluate error distribution on perfusion quantification resulting from α.

2178.   Quantitative Estimation of Cerebral Oxygenation in Micro-Vessels
Harshan Ravi1,2, Jinsoo Uh3, Peiying Liu1, Lisa C. Krishnamurthy1,2, and Hanzhang Lu1
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States, 2Department of Bioengineering, University of Texas at Arlington, Arlington, Texas, United States,3Department of Radiological Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States

Venous blood oxygenation is an important parameter for the quantification of cerebral metabolic rate of oxygen (CMRO2), a key biomarker for brain tissue viability and functionality. T2 based methods has been reported to measure Yv in macroscopic veins. However, the oxygenation of microvasculature (capillary/venule), which renders spatially more specific information, is not yet investigated. In this study we propose a novel technique to isolate microvascular venous blood signal and measure its oxygenation, named micro-vasculature T2-relaxation-Under-Spin-Tagging (mTRUST). This technique complements and extends the applicability of existing methods targeting macroscopic veins, and may lay foundation to region specific CMRO2 mapping in future.

2179.   Comparison of 3D Pseudo-CASL and H215O PET for Quantification of Cerebral Blood Flow
Joost P. A. Kuijer1, Larissa W. van Golen2, Marc C. Huisman3, Richard G. IJzerman2, Frederik Barkhof3, Michaela Diamant2, and Adriaan A. Lammertsma3
1Physics and Medical Technology, NCA, VU University Medical Center, Amsterdam, NL, Netherlands, 2Diabetes Center, Internal Medicine, VU University Medical Center, Amsterdam, NL, Netherlands, 3Radiology and Nuclear Medicine, NCA, VU University Medical Center, Amsterdam, NL, Netherlands

Arterial Spin Labeling (ASL) was compared with H215O Positron Emission Tomography (PET), the current gold standard for non-invasive quantification of CBF, in patients with type 1 diabetes and healthy subjects. The ASL variant used was pseudo-continuous, with background suppression, and a 3D FSE spiral readout. Both methods were compared in terms of absolute quantification and regional differences.

2180.   Automated Group Analysis Tools for CBF Measures Using CBFBIRN Database and Analysis Pipeline
David D. Shin1, Burak I. Ozyurt2, and Thomas T. Liu1
1Center for Functional MRI, University of California, San Diego, La Jolla, CA, United States, 2Dept. of Psychiatry, University of California, San Diego, La Jolla, CA, United States

Since its introduction in 2011 ISMRM, the CBFBIRN Database and Analysis Pipeline (CBFDAP) has processed/stored more than 1300 ASL datasets contributed by 24 research studies. The availability of CBF data from many diverse conditions (e.g. Alzheimer’s disease, schizophrenia, bipolar disorder, etc.) and associated subject demographics/assessments provides a unique opportunity to explore and mine clinically useful information. In order to facilitate this process, we developed a host of automated group analysis tools and integrated them to the CBFDAP. Three types of group analysis are supported, Path 1: mean gray matter analysis; Path 2: Regional analysis with user-provided ROIs; Path 3: voxel-level standard space analysis. Examples from all three paths are presented.

2181.   Quantitative Cerebral and Retinal Blood Flow Using Continuous Arterial Spin Labeling MRI and Fluorescent Microsphere
Yen-Yu Ian Shih1,2, Bryan H. De La Garza2, Shiliang Huang2, Guang Li2, Lin Wang3, and Timothy O. Duong4
1Experimental Neuroimaging Laboratory, Department of Neurology and Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, NC, United States, 2Research Imaging Center, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States, 3Devers Eye Institute, Legacy Research Institute, Portland, OR, United States, 4Research Imaging Center, UT Health Science Center at San Antonio, San Antonio, TX, United States

Continuous arterial spin labeling (CASL) MRI, widely used to non-invasively image blood flow (BF) of the brain, has been applied to image BF of the rat brain and retina but remains to be validated. The goal of this study was to use an established microsphere technique to cross-validate ASL MRI BF measurement in the rat brain and retina. By using a mixture of the two different sized fluorescent microspheres with two different colors, the cerebral, retinal and choroidal BF can be measured simultaneously in the same subject. Our data showed that BF values by MRI are in good accordance with the microsphere technique in the rat retina and cerebral cortex.

2182.   Measuring Tissue Perfusion in the Human Brainstem Using Multi-Inversion Time Pulsed Arterial Spin Labelling
Esther A H Warnert1, Ashley D. Harris1, Kevin Murphy1, Michael A. Chappell2, Judith E. Hall3, and Richard G. Wise1
1Cardiff University Brain Research Imaging Centre, Cardiff, South Glamorgan, United Kingdom, 2University of Oxford, Headington, Oxford, United Kingdom, 3Department of Anaesthetics, Intensive Care and Pain Medicine, School of Medicine, Cardiff, South Glamorgan, United Kingdom

We have performed a multi-inversion time pulsed ASL study with healthy subjects to obtain tissue perfusion kinetic curves of the brainstem. A two-compartment model was used that contains a tissue and intra-arterial component in order to model out macrovascular signal. Our study showed that the brainstem perfusion signal indeed has a relatively high macrovascular component, which can be model out to obtain tissue perfusion curves.

2183.   Effect of Deep Isoflurane Anesthesia on Cerebral Blood Flow Autoregulation in Non-Human Primates
Chun-Xia Li1, Sudeep Patel1, Danny J.J. Wang2, and Xiaodong Zhang1
1Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, United States, 2Ahmanson-Lovelace Brain Mapping Center, Department of Neurology, UCLA, Los Angeles, CA, United States

Non-human primates were widely used as various disease models in neuroscience studies and examined under isoflurane anesthesia. It is known that the cerebral blood flow (CBF) autoregulation can be disrupted under high isoflurane dosage and is more vulnerable in subcortical regions, but the regional specification of the effect remains poorly understood. In the present study, the pseudo continuous arterial-spin-labeling (pCASL) technique was used to evaluate the dose-dependent effect of deep isoflurane anesthesia on CBF of different brain structures. The result indicates that the CBF autoregulation in most cortical and subcortical regions of monkeys is impaired under 2% isoflurane.

2184.   Reinvestigation of Perfusion Measurement in Cerebral White Matter Using Pseudocontinuous Arterial Spin Labeling MRI
Wen-Chau Wu1,2, Shu-Chi Lin2, and Kuan-Lin Chen2
1Graduate Institute of Oncology, National Taiwan University, Taipei, Taiwan, 2Medical Imaging, National Taiwan University Hospital, Taipei, Taiwan

The feasibility of ASL MRI in cerebral perfusion measurement has been recognized in gray matter, but remains pending in white matter, mainly due to the tissue's low flow rate and long transit time. We tried to optimize the labeling duration (lower case Greek tau) and post-labeling delay (PLD) of pseudocontinuous ASL experimentally and numerically, based on a spatial resolution (1.56x1.56x5 mm3) finer than commonly used (3.4x3.4x5 mm3) to avoid partial volume effect. Results showed that cerebral perfusion can be measured in about 60% of white matter and that the optimal value is 2000 ms for lower case Greek tau and 1500-1800 ms for PLD.

2185.   Assessment of Microcirculation in Murine Myocardium: A Retrospective Method for Quantification of Perfusion and Regional Blood Volume
Fabian Tobias Gutjahr1, Thomas Kampf1, Xavier Helluy1, Christian Herbert Ziener2, Peter M. Jakob1,3, and Wolfgang Rudolf Bauer4
1Experimental Physics 5, University of Wuerzburg, Wuerzburg, Bavaria, Germany, 2German Cancer Research Center, Heidelberg, Baden Wuerttemberg, Germany, 3Magnetic Resonance Bavaria, Wuerzburg, Bavaria, Germany, 4Medizinische Klinik und Polyklinik I, Universitaetsklinikum Wuerzburg, Wuerzburg, Bavaria, Germany

In this work a retrospectively triggered method for the quantification of perfusion and regional blood volume (RBV) in murine myocardium is demonstrated. Perfusion and RBV maps can be reconstructed on any desired position in the heart cycle. Furthermore the calculation of RBV maps requires a voxel by voxel comparison of a pre and post contrast agent T1 map. A good match for both map can be guaranteed due to the ability to reconstruct T1 maps of any desired position in the heart cycle. The obtained RBV and perfusion values are shown to be in agreement with previous studies.

2186.   Simultaneous Quantification of Perfusion, Venous Oxygen Saturation, and Skeletal Muscle T2* in Response to Cuff-Induced Ischemia in the Leg
Erin K. Englund1, Michael C. Langham1, Cheng Li1, Emile R. Mohler2, Thomas F. Floyd3, and Felix W. Wehrli1
1Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States, 2Department of Cardiology, University of Pennsylvania, Philadelphia, PA, United States, 3Department of Anesthesiology, Stony Brook University, Stony Brook, NY, United States

A novel method to simultaneously measure perfusion, venous oxygen saturation, and skeletal muscle T2* using an interleaved pulsed arterial spin labeling and multi-echo GRE sequence, termed PASL/Ox-BOLD, is presented. The technique is assessed in healthy subjects during a series of ischemia reperfusion paradigms. Time course data is analyzed to investigate the kinetics of recovery following cuff-induced ischemia. Results indicate that PASL/Ox-BOLD is capable of faithfully measuring all three parameters at 2 second temporal resolution. The method is also used to investigate a small cohort of peripheral artery disease patients. In these patients, a blunted and delayed hyperemic response is detected.

2187.   ASL in Low-Intensity Exercise at 7T - Initial Experiences
Kiril Schewzow1,2, Georg Bernd Fiedler1,2, Martin Meyerspeer1,2, Ewald Moser1,2, and Albrecht Ingo Schmid1,2
1Medical Physics and Biomedical Engeneering, Medical University of Vienna, Vienna, Wien, Austria, 2MR Centre of Excellence, Medical University of Vienna, Vienna, Wien, Austria

Adequate perfusion is essential for muscle function and tissue health. Vascular complications are a common problem in several diseases like diabetes mellitus. Arterial spin labeling represents a non-invasive assessment of tissue perfusion using magnetically labeled blood water as an endogeneous tracer. ASL has been used to measure dynamic changes in skeletal muscle perfusion during and after exercise (plantar flexion). In this study we demonstrate the feasibility of measuring ASL in aerobic exercise at 7 Tesla with a high temporal resolution and good SNR and high intra-individual reproducibility.

2188.   Multi-Slice Look-Locker FAIR for Hepatic Arterial Spin Labelling
Rajiv Ramasawmy1,2, Adrienne E. Campbell-Washburn1, Sean Peter Johnson2, Jack Wells1, Rosamund Barbara Pedley2, Simon Walker-Samuel1, and Mark F. Lythgoe †1
1Centre for Advanced Biomedical Imaging, University College London, London, Greater London, United Kingdom, 2Cancer Institute, University College London, London, Greater London, United Kingdom

We present a novel use of a multi-slice respiratory-triggered flow-sensitive alternating inversion recovery (FAIR) Look-Locker arterial spin labelling (ASL) technique to measure perfusion within a mouse liver. Measurements from the multi-slice technique were in good agreement with those from single-slice triggered FAIR Look-Locker ASL. As the acquisition time is the same for the multi-slice and single-slice sequences, the multi-slice technique demonstrates a three-fold increase in efficiency of liver coverage. Pre-clinical liver perfusion measurements will find utility in a number of disease models such as liver metastases and liver cirrhosis. As ASL does not require injected contrast agents, this technique is suitable for follow-up and repeated measurements to track subject response to therapies.

2189.   Renal Perfusion Imaging with Two-Dimensional Navigator Gated Arterial Spin Labeling
Huan Tan1, Ioannis Koktzoglou1,2, and Pottumarthi Vara Prasad1,2
1NorthShore University HealthSystem, Evanston, IL, United States, 2The University of Chicago Pritzker School of Medicine, Chicago, IL, United States

A single breath-hold scan does not provide enough time for signal averaging needed by arterial spin labeling technique in renal perfusion measurement. In our study, we have implemented a novel two-dimensional (2D) navigator technique in concert with FAIR True-FISP to minimize respiratory motion via retrospective reconstruction and allow for multiple averages during free-breathing acquisition. The 2D navigator-gated approach achieved good image quality in patients while the breath-hold results were unusable. Given the limitation of using contrast agents in patients with compromised renal function, free breathing ASL offers a non-invasive method to evaluate renal perfusion.

2190.   Measurement of Bulk Liver Perfusion: Initial Assessment of Agreement Between ASL and Phase-Contrast MRI at 9.4T
Manil Chouhan1,2, Rajiv Ramasawmy2,3, Adrienne E. Campbell-Washburn2, Alan Bainbridge4, Jack Wells2, Nathan Davies5, Rosamund Barbara Pedley3, Raj Mookerjee5, Shonit Punwani1, Stuart Taylor1, Simon Walker-Samuel2, and Mark F. Lythgoe2
1Centre for Medical Imaging, University College London, London, Greater London, United Kingdom, 2Centre for Advanced Biomedical Imaging, University College London, London, Greater London, United Kingdom,3Cancer Institute, University College London, London, Greater London, United Kingdom, 4Department of Medical Physics and Bioengineering, University College London, London, Greater London, United Kingdom,5Institute for Liver and Digestive Health, University College London, London, United Kingdom

Non-invasive liver perfusion measurements could be used to monitor hepatic disease development and provide a functional biomarker for novel therapies. Arterial spin labelling (ASL) has not found extensive utility in the liver, mainly due to its dual vascular supply and susceptibility to respiratory motion. ASL can provide regional perfusion maps whereas with phase-contrast measurements taken in the portal vein can provide a bulk portal perfusion. Previous work has reported mouse liver regional perfusion maps but here we present rat liver ASL validated against phase-contrast measurements.

2191.   Cerebral Blood Flow of Mouse Increases Upon Insulin-Induced Hypoglycemia Using the Continuous Arterial Spin Labeling Technique
Hongxia Lei1,2 and Rolf Gruetter3,4
1University of Geneva, Geneva, Geneva, Switzerland, 2EPFL, Lausanne, Vaud, Switzerland, 3École Polytechnique Fédérale de Lausanne, Geneva, Geneva, Switzerland, 4University of Lausanne, Lausanne, Vaud, Switzerland

The aim of our study was to apply the continuous arterial spin labeling (CASL) technique on mouse before and during hypoglycemia at 9.4T. The elevated blood flow upon hypoglycemia was observed even when animals were under isoflurane anesthesia. This study opens possibility of investigating genetically modified models using multiple MR modalities at high magnetic fields.

2192.   Arterial Transit Delay Effects on Perfusion Measurement in an Elderly Cohort
Weiying Dai1, Ajit Shankaranarayanan2, and David C. Alsop1
1Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, United States, 2Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States

Arterial transit delay (ATD) measurement has been proposed to eliminate the ATD errors in perfusion measurements. In elderly cohorts, potentially longer and more variable ATD may introduce systematic errors in perfusion measurement if not taken into account. A quick ATD measurement was performed in 59 elderly patients over 70 years old scheduled for elective surgical procedures. ATD was heterogeneous across different brain regions and significantly longer than the young in all regions except posterior regions. ATD measurement can improve the reliability and accuracy of perfusion measurement in the elderly population and thus should improve the sensitivity of clinical research studies involving elderly subjects.

2193.   Resting State Functional Connectivity of the Subthalamic Nucleus in Parkinson’s Disease Assessed Using Arterial Spin Labeling
Maria A. Fernandez-Seara1, Elisa Mengual2, Marta Vidorreta1, Francis Loayza1, Jaione Irigoyen1, and Maria Pastor1
1Neuroscience, CIMA - University of Navarra, Pamplona, Navarra, Spain, 2Anatomy, Medical School - University of Navarra, Pamplona, Navarra, Spain

Arterial spin labeled (ASL) perfusion MRI offers the possibility of measuring cerebral blood flow (CBF) and assessing resting state functional connectivity (FC) by means of evaluating the spatial patterns of synchronous spontaneous fluctuations in the CBF time series. Recent work has shown that ASL FC has statistical power comparable to that of BOLD FC and could provide a better characterization of low frequency fluctuations than BOLD. In this work, ASL FC has been used to study FC connectivity of the STN in healthy controls and to evaluate STN FC alterations in Parkinson’s disease.


Monday, 22 April 2013 (16:30-18:30) Exhibition Hall
Perfusion & Permeability

2194.   3D Spoiled Gradient-Recalled Echo Sequence with Compressed Sensing for DCE-MRI: Improved Temporal Resolution and Image Contrast
Bin Chen1, Kai Zhao2, Bo Li3, Wenchao Cai2, Xiaoying Wang1,2, Jue Zhang1,3, and Jing Fang1,3
1Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China, 2Dept. of Radiology, Peking University First Hospital, Beijing, China, 3College of Engineering, Peking University, Beijing, China

Compressed sensing (CS) technique was introduced in this study in order to improve the temporal resolution in Dynamic Contrast-enhanced MR imaging. A real pulse sequence was modified with CS MRI scheme with undersampling in phase encoding, resulting in 2x, 3x, 4x, and 8x accelerations. Actual high temporal resolution was achieved, which could contribute more creditable quantitative renal perfusion measurements. In addition, the contrast-to-noise ratio of reconstructed images was effectively improved.

2195.   Analysis of the Spin and Gradient Echo (SAGE) Sequence for DSC-MRI in Rat Brain Tumors
Ashley M. Stokes1,2 and Christopher C. Quarles1,2
1Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, 2Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States

A combined spin- and gradient-echo (SAGE) EPI method was applied in a rat glioma model to obtain absolute ΔR2, ΔR2* and ΔR1 curves, thereby permitting derivation of dynamic susceptibility contrast (DSC) parameters. T1-insensitive estimates of R2 and R2* were acquired with SAGE and compared to conventional GE and SE DSC parameters, as well as independently measured R2 and R2*. The normal brain GE and SAGE ΔR2* curves produced similar relative cerebral blood volume (rCBV) values, while tumor leakage effects led to substantially underestimated rCBV values from the GE ΔR2* curve. Dynamic SAGE acquisition can provide improved perfusion and permeability information.

2196.   A Single-Shot Multiple Spin- And Gradient-Echo Acquisition for Perfusion Imaging Using SENSE Acceleration and Partial K-Space Sampling
Jack T. Skinner1,2, Ryan K. Robison2,3, and Christopher C. Quarles1,2
1Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, 2Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, 3Philips Healthcare, Highland Heights, OH, United States

Previous single-echo techniques for perfusion imaging have been extended to multiple-echo sequences to acquire more accurate estimates of R2* with contrast injection. Recently, a spin- and gradient-echo (SAGE) acquisition, for simultaneous R2 and R2* mapping, was introduced. This current study implements a single-shot SAGE sequence that utilizes SENSE parallel imaging and partial k-space sampling, allowing short echo times (< 10ms) suitable for AIF characterization. Validation of the current protocol with conventional multiple-echo acquisitions was carried out in phantoms and in the brain. The suggested single-shot SAGE acquisition may provide a robust method for quantitative perfusion imaging in brain tumors.

2197.   On the Importance of T1 Estimation for SAGE Perfusion MRI Data
Alexander Brost1, Heiko Schmiedeskamp1, Matus Straka1, Jalal Andre2, and Roland Bammer1
1Center for Quantitative Neuroimaging, Stanford University, Stanford, CA, United States, 2Department of Radiology, University of Washington, Seattle, WA, United States

The spin- and gradient-echo (SAGE) EPI sequence was developed to estimate cerebral blood flow (CBF) and cerebral blood volume (CBV). The main purpose of the sequence is to provide T1-independent perfusion-weighted imaging maps. Gadolinium-based contrast agents cause T1-shortening, in particular, when contrast agent leaks into the extravascular-extracellular space. Leakage correction using SAGE EPI requires a separately acquired pre-bolus T1 map. To estimate the effects of an incorrect T1 map, we simulated the effects using a pharmacokinetic model. Leakage correction could be applied to multi-echo data that lack a properly determined prebolus T1 map without significantly compromising CBV and MTT estimates.

2198.   Calibration of Dynamic Susceptibility Contrast MRI Using T1-Based Steady-State CBV (Bookend Technique) and Vascular Space Occupancy (VASO): Comparison with Pseudo-Continuous Arterial Spin Labeling
Emelie Lindgren1, Ronnie Wirestam1, Karin Markenroth Bloch1,2, André Ahlgren1, Matthias J.P. van Osch3, Danielle van Westen4, Yulia Surova5,6, Freddy Ståhlberg1,7, and Linda Knutsson1
1Department of Medical Radiation Physics, Lund University, Lund, Sweden, 2Clinical science, Philips, Lund, Sweden, 3C.J.Gorter Center for high field MRI, Department of Radiology, LUMC, Leiden, Netherlands, 4Center for Medical Imaging and Physiology, Skane University Hospital Lund, Lund, Sweden, 5Department of Clinical Sciences, Lund University, Lund, Sweden, 6Department of Neurology, Skåne University Hospital, Lund, Sweden,7Lund University Bioimaging Centrum, Lund University, Lund, Sweden

Quantification of CBF in absolute terms is relevant in some clinical applications. However, absolute CBF obtained by dynamic susceptibility contrast MRI (DSC-MRI) is usually overestimated. One solution is to calibrate DSC-MRI CBF using a complementary CBV method. In this study, T1-based CBV (Bookend) and VASO were used to calibrate CBF from DSC-MRI, and results from calibrations were compared with CBF from pseudo-continuous ASL (pCASL). Both calibration methods showed absolute grey matter CBF values which were comparable with corresponding CBF values from pCASL.

2199.   Improved T1 Mapping and DCE-MRI Quantification for Prostate at 3T by Incorporating B1 Inhomogeneity Correction
Ming-Ching Chang1, Sandeep Narendra Gupta1, Laura I. Sacolick2, Clare Tempany-Afdhal3, Fiona Fennessy3, and Ehud J. Schmidt3
1GE Global Research Center, Niskayuna, NY, United States, 2GE Global Research Center, Munich, Germany, 3Radiology, Brigham and Women's Hospital, Boston, MA, United States

Dynamic Contrast Enhanced MRI (DCE-MRI) is used for the assessment of tumor vascular properties with application to prostate cancer staging and treatment monitoring. Analysis of DCE-MRI requires knowledge of pre-contrast T1 maps. T1 mapping using Variable Flip Angle imaging is inaccurate due to B1 inhomogeneity. We present improved T1 mapping and PK quantification in prostate DCE-MRI at 3T by incorporating B1 inhomogeneity correction using the Bloch-Siegert B1 mapping method. We validated the method on 26 subjects and demonstrated good T1 quantification and better PK maps by incorporating B1 correction into DCE-MRI quantification.

2200.   Accuracy of Quantitative 3D DCE-MRI Using Variable Flip Angle T1 Mapping, B1 Correction, and the Bookend Method
Brandon Zanette1, Greg O. Cron2,3, Thanh B. Nguyen2,3, Mark E. Schweitzer2,3, and Ian G. Cameron2,3
1Carleton University, Ottawa, Ontario, Canada, 2Ottawa Hospital Research Institute, Ottawa, Ontario, Canada, 3Radiology, University of Ottawa, Ottawa, Ontario, Canada

For quantitative DCE-MRI, Gd concentration is conventionally estimated via a pre-DCE T1 map using variable flip angles (VFA), which allows conversion of DCE signal to concentration. This approach, however, is sensitive to B1 variations. Two techniques may potentially reduce errors: B1 mapping and the “Bookend Method” (involving a post-DCE T1 map). The results of this study show that, when estimating concentration in tissue for quantitative DCE-MRI, the best results will be achieved using the Bookend Method and accurate T1 maps. B1-corrected VFA does not consistently deliver enough T1 accuracy, indicating that further improvements in T1 mapping techniques are required.

2201.   Monitoring of T2 with Application of Diffusion Gradients to Remove Microcirculation Contributions to Signal for Optimisation of Diffusion Protocols and Generation of Flow-Free T2 Maps
Neil P. Jerome1, James A. d'Arcy1, Matthew R. Orton1, Thorsten Feiweier2, Dow-Mu Koh3, Martin O. Leach1, and David John Collins1
1Radiotherapy & Imaging, The Institute of Cancer Research, Sutton, Surrey, United Kingdom, 2Imaging & Therapy Division, Siemens AG, Healthcare Sector, Erlangen, Germany, 3Department of Radiology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom

Diffusion-weighted MRI in the body must account for a microcirculation fraction, separate to self-diffusion, within imaging voxels. Explicit control of diffusion pulse length and delay allows reproducible application of diffusion gradients with varying echo times; calculation of mono-exponential T2 estimates with applied gradients of b=0 and b=200 s/mm2 shows significant changes observed in liver, kidney and spleen. This suggests that the microcirculation component, with its own distinct T2, is being removed, allowing the generation of flow-free T2 maps more robustly estimating tissue T2s. This approach enables appropriate b-value choices when considering diffusion models that include or exclude microcirculation contribution.

2202.   The Influence of Vascular Morphology on DSC-MRI Derived Blood Volume Measurements in Brain Tumors
Natenael B. Semmineh1, Junzhong Xu1, and Christopher C. Quarles1
1Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States

The use of DSC-MRI in tumors can be confounded by the assumption that a linear relationship, with a spatially uniform rate constant termed the vascular susceptibility calibration factor, exists between the contrast agent concentration and the measured transverse relaxation rate change. Using simulations we demonstrate that varying vascular morphology parameters can increase or decrease the vascular susceptibility calibration factors found in tumor-like vessel trees, leading to the overestimation or underestimation of the tumor blood volume.

2203.   Optimizing Repeatability of Independent Component Analysis Applied to Dynamic Susceptibility Contrast MRI in 68 Brain Tumor Patients with Five Repeated Scans.
Peter S. LaViolette1, Mitchell Daun2, Alexander D. Cohen3, Jennifer Connelley2, and Kathleen M. Schmainda1
1Radiology, Medical College of Wisconsin, Milwaukee, WI, United States, 2Neurology, Medical College of Wisconsin, Milwaukee, WI, United States, 3Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States

Independent component analysis applied to DSC perfusion data allows the separation of arterial and venous perfusion. This study varies the number of ICA components modeled to determine which number generates the most repeatable arterial and venous maps. 68 patients with 5 repeated scans on the same scanner were compared. We conclude the modeling 3 components reliably generates arterial and venous maps.

2204.   Network Analysis Based on Analytic Solution to Permutation Tests on Support Vector Machines
Madhura Ingalhalikar1, Bilwaj Gaonkar1, Alex R. Smith1, Robert T. Schultz2, and Ragini Verma1
1Section of Biomedical Image Analysis, Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States, 2Center for Autism Research, Childrens Hospital of Philadelphia, Philadelphia, PA, United States

The study employs a novel method using an analytic approach to permutation tests on support vector machines for computing statistical significance maps on connectivity matrices. Permutation tests are critical for interpreting SVM output for high dimensional data. However performing these tests is time consuming and computationally expensive. However, the analytical approximation to these tests can yield the results quickly. We apply this method to investigate the differences between patients with autism and typically developing controls based on their structural connectivity networks. We find that patients with autism show lower connectivity mainly in the connections initiating from temporal regions like fusiform gyrus and insula as well between fronto-parietal tracts.

2205.   PCA of Combined DCE-MRI Data from a Large Cohort Can Be Used to Assess Treatment Effects with Similar Sensitivity to Pharmacokinetic Model Fitting
Matt Nathan Gwilliam1, David John Collins1, Martin O. Leach1, Helen Young2, and Matthew R. Orton1
1CRUK and EPSRC Imaging Centre, Institute of Cancer Research, Sutton, London, United Kingdom, 2Astrazeneca, Macclesfield, Cheshire, United Kingdom

DCE-MRI is widely used in clinical trials of antiangiogenic and vascular disrupting agents in the assessment of treatment response. Fitting pharmacokinetic models gives well defined measures of vascular function, but difficulties in obtaining a patient-specific AIF can cause additional errors on PK metrics. This abstract demonstrates that a model-free PCA approach is as sensitive to DCE-MRI treatment changes as model-based PK measures in a group of patients receiving a VEGF inhibitor.

2206.   Time-Consistent Non-Rigid Motion Compensation for 3D DCE-MRI of the Entire Liver
Marijn van Stralen1, Hanke J. Schalkx2, Harriët W. Mulder1, Kenneth Coenegrachts3, Maarten S. van Leeuwen2, Wouter B. Veldhuis2, and Josien P.W. Pluim1
1Image Sciences Institute, UMC Utrecht, Utrecht, Utrecht, Netherlands, 2Radiology, UMC Utrecht, Utrecht, Utrecht, Netherlands, 3Radiology, AZ St.‐Jan Brugge‐Oostende AV, Brugge, West-Vlaanderen, Belgium

Recent developments have enabled high-resolution dynamic contrast-enhanced MRI (DCE-MRI) of the entire liver. However, breathing and other organ motion hampers the current clinical use of DCE-MRI for perfusion analysis. Moreover, intensity change as a result of contrast perfusion challenges existing motion correction techniques. We propose a temporally consistent motion compensation method based on the integrated 3D + time alignment of the gradient magnitude of the image intensity. It is shown that time-consistent non-rigid registration outperforms temporal independent registration by measuring surface errors on manual liver segmentations. These results promise improved perfusion analysis (eg. pharmacokinetic modeling) of abdominal organs using DCE-MRI.

2207.   Segmentation of Normal Liver Volume Using Dynamic Contrast Enhanced Gd-EOB-DTPA Time Intensity Curves
Jonathan P. Dyke1, Pascal Spincemaille1, Martin R. Prince1, and Krishna Juluru1
1Radiology, Weill Cornell Medical College, NY, NY, United States

Monitoring total liver volume is of importance to assess regeneration post-resection. Normal liver volume is also of prognostic importance in subject with tumor burden and inflammatory disease. A technique is presented to segment normal liver by calculating a voxel wise Pearson’s R2 correlation coefficient with slice specific Gd-EOB-DTPA (Eovist) dynamic contrast enhanced DCE-MRI uptake curves. Significant correlation was found with DCE segmented liver volume and manual tracing methods. Future application of this technique may be found in other organ systems and patient specific monitoring of organ volume over time.

2208.   Signal Intensity and Texture Feature Analysis in Contrast-Enhanced Liver MRI for Chronic Liver Disease Diagnosis
Jihun Oh1, Diego Martin2, and Xiaoping P. Hu3
1School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 2Department of Medical Imaging, University of Arizona, Tucson, Arizona, United States, 3Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States

This paper describes our work of using features derived from contrast-enhanced liver MR images for providing a quantitative assessment of chronic liver disease severity. We first examined the mean slope of contrast uptake in hepatobiliary phase and demonstrated that it is significantly correlated with fibrosis score. We also examined several texture measures in equilibrium phase using Gabor filtering and grey level co-occurrence matrix and built a supervised maximum a posteriori classifier using these features to predict the disease severity. The classifier was evaluated by cross-validation and shown to be highly robust in predicting fibrosis score.

2209.   Logan Plot Estimates of Tracer Distribution Volume from Dynamic Contrast Enhanced MRI Data and Tumor Cellularity in a Rat Model of Cerebral Glioma at 7T
Madhava P. Aryal1,2, Tavarekere N. Nagaraja2, Kelly A. Keenan2, Hassan Bagher-Ebadian2, Swayamprava Panda2, Stephen Brown2, and James R. Ewing1,2
1Physics, Oakland University, Rochester, MI, United States, 2Henry Ford Hospital, Detroit, MI, United States

In this study, Logan plot graphical approach was applied to dynamic contrast enhanced MRI(DCE-MRI) data to estimate the distribution volume(VD) in a rat model of cerebral glioma. Test-retest VD values for 18 animal studies were quite stable. The test group mean of VD (7.94%) moved downward to (7.21%) in the retest group, but not significantly (p=0.21). The combined sample mean(±standard deviation) of VD was; (7.58±2.33)%. Also, the estimated VD showed a strong correlation to corresponding Patlak plot estimate (r=0.93, p<0.001). The mean tumor cellularity count was 2441 ± 850. Tumor cellularity and VD were highly correlated (r =0.76, p < 0.01). Thus, the Logan plot graphical approach can be a useful tool on DCE-MRI also for the diagnosis and evaluation of therapeutic response in tumors.

2210.   A Threshold Method to Exclude Unreliable Tracer Kinetic Model Parameters Measured from DCE MRI in Breast Cancer
Dennis Lai Hong Cheong1, Bo Zhang1, Soo Chin Lee2, and Thian C. Ng1,3
1Clinical Imaging Research Center, SBIC/A*STAR & National University of Singapore, Singapore, Singapore, 2Department of Haematology-Oncology, National University Health System, Singapore, Singapore, 3Department of Diagnostic Radiology, National University of Singapore, Singapore, Singapore

Model based tracer kinetic analysis of DCE MRI relies on some curve fitting process. The reliability of voxel level measured parameter depends on two main criteria: sufficient contrast to noise ratio (CNR) and successful curve fitting. We present a method to filter out unreliable voxels with low CNR and poor quality of fit based on fraction of modeling information (FMI). We found that CNR and FMI are useful measures for rejecting voxels with unreliable parameter values that were either due to a low CNR or a poor curve fitting. This is a part of our DCE-MRI project on breast tumors.

2211.   Dynamic Contrast Enhanced – Magnetic Resonance Imaging (DCE-MRI): Insights About Arterial Input Function Definition, Model Selection and the Quantitative Signal Difference Method
Georges Hankov1, Jill Fredrickson1, Gregory Ferl1, David Clayton1, Alexandre Coimbra2, and Alexandre de Crespigny2
1Genentech Inc., South San Francisco, California, United States, 2Genentech Inc, South San Francisco, California, United States

The use of DCE-MRI in multicenter therapeutic trials requires standardization, streamlined processing, and a focus on reproducibility. The purpose of this work was to assess the necessity of modeling the AIF and estimating the time lag between tissue and AIF uptake, and also evaluated the reproducibility of the Signal Difference [SD] method, using simulations and patient data. We found that modeling the AIF results in underestimation of the parameters, especially plasma volume, vp. Estimating the time lag increases vp estimates, without altering the other kinetic parameters. The simpler [SD] method was slightly more reproducible than the regular apparent concentration method.

2212.   Arterial Input Function Reconstruction for DCE-MRI of the Liver Using Pre-Bolus Acquisition with Low Dose Gadolinium Contrast
Guido H. Jajamovich1, Claudia Calcagno1, Hadrien A. Dyvorne1, Henry Rusinek2, Shimon Aronhime1, and Bachir Taouli1
1Mount Sinai School of Medicine, New York, NY, United States, 2NYU School of Medicine, New York, NY, United States

A reconstructed arterial input function (AIF) using prebolus injection of a low dose gadolinium contrast (1.3 mL) was quantified and compared with the measured AIF after the injection of the main bolus in DCE-MRI of the liver. The curve shape reconstructed using pre-bolus injection was observed to be of better quality than the measured main bolus AIF in the majority of cases. The quantified AIF using pre-bolus showed better parameter reproducibility and significantly higher AUC60 (area under the curve at 60 sec), peak and upslope and significantly lower FWHM (full width at half maximum) compared to main bolus AIF.

2213.   Bolus Tracking Perfusion Imaging in Humans Using Quantitative Arterial Input Function
Elias Kellner1, Irina Mader2, Marco Reisert1, and Valerij G. Kiselev1
1Department of Radiology, University Hospital Freiburg, Freiburg, Germany, 2Section of Neuroradiology, University Hospital Freiburg, Freiburg, Germany

We recently presented a method for a quantitative determination of the arterial input function for DSC MRI. The method was verified in the pig model. In this work, we present measurements in patients with carotid stenosis and discuss the quantitative perfusion parameters obtained with our extended technique. Obtained cerebral blood flow is compared with the whole-brain flow evaluated using phase contrast MRI measurements in large arteries. Discussion focuses on issues, which are crucial for correct perfusion evaluation, such as vascular transport effects and water relaxation properties in tissue.

2214.   AIF Induced Limits of Parameter Uncertainty in Pharmakokinetic Models of Pre-Clinical DCE-MRI
Tammo Rukat1,2, Simon Walker-Samuel3, and Stefan A. Reinsberg1
1Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada, 2Institut für Physik, Humboldt Universität zu Berlin, Berlin, Germany, 3Centre for Advanced Biomedical Imaging, University College London, London, United Kingdom

The reliability of small animal DCE-MRI data analysis with quantitative pharmakokinetic models depends strongly on the time course of contrast agent (CA) administration, known as arterial input function (AIF). In this study the dependence of the intrinsic limits of a parameter predictability on the width of the AIF-peak (i.e. the speed of CA administration) is quantified to provide investigators with a tool to determine reasonable limits for CA administration protocols.

2215.   Fast NSR: An Optimized Non-Linear Stochastic Deconvolution for Large Data Sets and Clinical Analyses
Denis Peruzzo1, Danilo Benozzo1, Gianluigi Pillonetto1, and Alessandra Bertoldo1
1Department of Information Engineering, University of Padova, Padova, PD, Italy

We present fast NSR, an optimization of the original Non-linear Stochastic Regularization algorithm to quantify the residue function and the CBF in DSC-MRI. Fast NSR introduces a preliminary step that allows to overcome the limits in the original NSR implementation, such as the sensitivity to the starting points and the required computational time. In the preliminary step the optimal starting points and the stochastic component of the residue function are computed for each voxel. Fast NSR elaborates a whole subject in a couple of hours and is now suitable for the analysis of large data sets and in clinical context.

2216.   DSC-MRI Derived T2* Leakage Effect Depends on Structural Features of Extravascular Space
Natenael B. Semmineh1, Junzhong Xu1, Jerry Boxerman2, Gary W. Delaney3, and Christopher C. Quarles1
1Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States, 2Alpert Medical School of Brown University, Providence, Rhode Island, United States, 3CSIRO Mathematical and Information Sciences, Clayton South, Vic, Australia

Brain tumor DSC-MRI studies can be confounded by extravascular T2* effects that occur when the contrast agent extravasates. The resulting signals are consequently influenced by the extravascular compartmentalization of the contrast agent and therefore may depend on the spatial distribution of tumor cells within tissue. Using simulations we demonstrate that the dependence of ∆R2* on tissue CA concentration is significantly influenced by to cell density. We also show that the spacing of cells and cellular cluster distribution within a voxel can alter ∆R2* values significantly for cell spacing variations on the order of the cell size.

2217.   Tumour Leakage Characterized Using a Novel Dynamic Susceptibility Contrast MRI Model Correlates with Tumour Interstitial Space
Keiko Miyazaki1, David John Collins1, James A. d'Arcy1, Dow-Mu Koh2, Anwar R. Padhani3, Martin O. Leach1, and Matthew R. Orton1
1CR-UK and EPSRC Cancer Imaging Centre, The Institute of Cancer Research, Sutton, Surrey, United Kingdom, 2Department of Diagnostic Radiology, The Royal Marsden NHS Foundation Trust, Sutton, Surrey, United Kingdom, 3Paul Strickland Scanner Centre, Mount Vernon Hospital, Northwood, Middlesex, United Kingdom

A recently published DSC-MRI model that includes first-pass, re-circulation and leakage components was evaluated on serially acquired brain tumour data after pre-loading with Gd-contrast. Relationships between DSC-MRI and DCE-MRI kinetic parameters were explored. The tertiary amplitude parameter a3 of the novel model, which characterizes the equilibrium phase (where BBB is intact) or leakage (where BBB is disrupted), was found to correlate strongly with the interstitial space. Results suggest it may be possible to obtain information on tumour interstitial space, in addition to blood volume, blood flow and mean transit time, from a single DSC-MRI measurement by employing this novel model.

2218.   Optimal Sampling Settings for Reliable Blood Brain Barrier Permeability Quantification Using DCE-MRI, a Monte Carlo Approach
Cecile RLPN Jeukens1, Harm J. van de Haar1, Jacobus F.A. Jansen1, Paul A.M. Hofman1, C. Eleana Zhang2, Julie Staals2, Saartje Burgmans3, Frans RJ Verhey3, Robert J. van Oostenbrugge2, and Walter H. Backes1
1Radiology, Maastricht University Medical Centre, Maastricht, Limburg, Netherlands, 2Neurology, Maastricht University Medical Centre, Maastricht, Limburg, Netherlands, 3Alzheimer Centre Maastricht, Maastricht University Medical Centre, Maastricht, Limburg, Netherlands

Using Monte Carlo simulations, we aim to determine the optimal sampling settings for reliable permeability (Ki) and plasma volume (vp) determination: 1) a single temporal resolution, i.e a single sample frequency (Capital Greek Deltat), versus dual temporal resolution, i.e., a high initial sample frequency (Capital Greek Deltat1=2.5s for 1:30min) followed by a lower sample frequency (Capital Greek Deltat2=10s—3min), and 2) the scan duration. We find that using a dual temporal resolution protocol and a scan duration of 15-20 minutes allows a reliable Ki and vp determination (5%/95% CI = -/+ 10%) for Ki and vp values down to Ki=0.002 min-1 and vp = 0.01.

Assessment of Vessel Permeability by Combining DCE and ASL MRI
Ting-Ting Chang1, Alex M. Wong2, Feng-Xian Yan1, Yu-Shi Lin1, and Ho-Ling Liu1,2
1Department of Medical Imaging and Radiological Sciences, Chang Gung University, Kwei-Shan, Tao-Yuan, Taiwan, 2Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Kwei-Shan, Tao-Yuan, Taiwan

This study proposed to combine dynamic contrast enhanced (DCE) and arterial spin labeling (ASL) MRI for assessing tumor vessel permeability in a group of 11 pediatric patients. After co-registration of measured parametric maps, permeability-surface-product (PS) was calculated by Ktrans from DCE-MRI and CBF from ASL on voxel-by-voxel basis. The results showed that for small Ktrans values they were approximately equal to the resulted PS values. When Ktrans values were greater, they became increasingly underestimated than the PS values. The largest discrepancy between Ktrans and PS in this study was 13% in a patient with mean tumor Ktrans of 0.10 min-1.

2220.   Dynamic Contrast-Enhanced MRI of Mouse Cirrhotic Liver: A Pilot Study
Septian Hartono1,2, Tong San Koh1, Lei Zhou3, Quan Sing Ng1, Puor Sherng Lee1, Kai-Hsiang Chuang4, Yock Young Dan3, Laurent Martarello5, and Choon Hua Thng1
1National Cancer Centre Singapore, Singapore, NA, Singapore, 2Nanyang Technological University, Singapore, NA, Singapore, 3National University Health System, Singapore, NA, Singapore, 4Singapore Bioimaging Consortium, Singapore, NA, Singapore, 5Roche Translational Medicine Hub, Singapore, NA, Singapore

We carried out a pilot study using DCE-MRI to assess liver cirrhosis in mice. Elevated values of extravasation parameters such as interstitial volume and vascular permeability were found in the cirrhotic mice, which was consistent to the capillarisation of liver sinusoidal endothelium found in liver cirrhosis.

2221.   Entropy Analysis of Peak Enhancement Ratio from DCE-MRI as a Potential Marker to Assess Brain Tumor Response to Radiotherapy
Chih-Feng Chen1, Ho-Ling Liu2,3, Yu-Jie Huang4, Yuan-Hsiung Tsai1, and Hsu-Huei Weng1
1Department of Radiology, Chang Gung Memorial Hospital, Chiayi branch, and Chang Gung University of Science and Technology, Chiayi, Taiwan, 2Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taoyuan, Taiwan, 3Healthy Aging Research Center, Chang Gung University, Taoyuan, Taiwan, 4Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan

This study assessed heterogeneity changes in peak enhancement ratio (PER) from DCE-MRI by calculating entropy in brain tumors before and after radiotherapy. There were 11 patients in the non-responder group and 12 patients in the responder group. The post- to pre-radiotherapy ratio of entropy was defined as therapeutic entropy ratio (TER). TER was significantly higher in the non-responder (1.14¡Ó0.14) than that in the responder (0.86¡Ó0.1). The corresponding area under the receiver operating characteristic curve was 0.98. In conclusion, calculating the heterogeneity changes in tumors via entropy could help diagnose response to therapy in clinical.

Imaging the Fragile Brain: Using BOLD Signal Fluctuations to Study Perfusion in Normal Subjects and Patients with Cerebrovascular Disease
Thomas Christen1, Deqiang Qiu1, Wendy W. Ni1, Michael E. Moseley1, and Greg Zaharchuk1
1Radiology, Stanford University, Stanford, California, United States

In this work, we acquired resting state BOLD image data in normal subjects and patients with cerebrovascular disease to study brain perfusion. The signal was analysed in two ways: (1) we looked at the amplitude of the fluctuations after high pass filtering of the signal, and (2) we looked at the correlation between the MR signal in major blood vessels (such as the sagittal sinus) and the rest of the brain. These maps demonstrated similar characteristics to CBF and CBV but did not require contrast.

2223.   Correlation Between Hemodynamic Variation and Resting-State fMRI in Patients with Carotid Artery Stenosis
Feng-Xian Yan1, Tsong-Hai Lee2, Pin-Hsun Huang1, Kuo-Lun Huang2, Ho-Fai Wong3, and Ho-Ling Liu1,3
1Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taoyuan, Taiwan, 2Department of Neurology and Stroke Center, Chang Gung Memorial Hospital, and Chang Gung University College of Medicine, Taoyuan, Taiwan, 3Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital, Taoyuan, Taiwan

This study aimed to investigate whether the functional connectivity (FC) derived from BOLD signal fluctuation is correlated with deficient blood supply in patients with unilateral internal carotid artery (ICA) stenosis. Thirty-eight patients underwent resting-state (RS) fMRI and DSC perfusion MRI scans. This study found that the prolonged perfusion delay time (Tmax) was significantly correlated (p < 0.05) with reduced default-mode network connectivity in the inferior parietal cortex ipsilateral to the ICA stenosis without apparent CBF impairments. Further studies are required to understand whether such correlation is originated from neuronal or purely hemodynamic variations.

2224.   The Comparison Study of ASL and DCE MRI for Renal Glomerular Filtration Rate (GFR) Mapping
Jing Wang1, Yudong Zhang2, Jue Zhang1, Xiaoying Wang3, and Jing Fang4
1Academy for Advanced Interdisciplinary Studies, Peking Unversity, Beijing, China, 2Department of Radiology, The First Affiliated Hospital With Nanjing Medical University, Nanjing, China, Beijing, China, 3Department of Radiology, Peking University First Hospital, Beijing, China, 4Peking University, Beijing, China

This study developed a new approach for noninvasive renal perfusion and glomerular filtration rate mapping based on PASL using variable TE acquisitions on clinical 3T MR. There were six rabbits included in the initial experiments and each of them accepted 6 different TEs ASL scans. Based on the proposed method, the rabbit RBF, blood R2* and GFR maps were obtained simultaneously by a two-compartment model fitting. Furthermore, the non-contrast GFR values were compared with DCE-MRI results to explore the feasibility of VTE-ASL as a noninvasive assessment of renal status in a single examination.

2225.   Direct CBF Comparison Between MRI ASL and DSC and Perfusion CT-Scan in Treated Tumor Patients
Marjorie Villien1,2, Do Kien N Guyen1, Julien Bouvier1, Cedric Mendoza3, Sylvie Grand3, Louise Fanchon1, Emmanuel Luc Barbier4, Irène Troprès5, Jean-François Le Bas3, Alexandre Krainik3, and Jan M. Warnking1
1Grenoble Institut of Neurosciences, INSERM, Grenoble, France, 2Massachusetts General Hospital, Harvard, Charlestown, Massachusetts, United States, 3Clinique universitaire de neuroradiologie et d'IRM, CHU Grenoble, Grenoble, France, 4Grenoble Institut of Neurosciences, INSERM U836, Grenoble, France, 5SFR1, Université Joseph Fourier, Grenoble, France

The goals of this study were to assess the reproducibility of Dynamic Susceptibility Contrast (DSC) MRI and Perfusion-CT (PCT) and to compare the CBF estimates obtained with DSC, PCT, and Arterial Spin Labeling (ASL). We included patients with cerebral tumor, routinely monitored with these imaging methods. We observed good agreement between DSC and PCT, and poor correlation between DSC and ASL. A more detailed analysis of the present data could yield insights into the respective strengths and weaknesses of each method depending on the vascular properties.

2226.   Comparison of Quantitative Cerebral Blood Flow Measured with Bolus Tracking Perfusion MRI and H215O PET in the Porcine Model
Elias Kellner1, Irina Mader2, Michal Mix3, Marco Reisert1, Katharina Förster4, Thao Nguyen-Thanh2, Daniel Nico Splitthoff1, Peter Gall1, and Valerij G. Kiselev1
1Department of Radiology, University Hospital Freiburg, Freiburg, Germany, 2Section of Neuroradiology, University Hospital Freiburg, Freiburg, Germany, 33Department of Nuclear Medicine, University Hospital Freiburg, Freiburg, Germany, 44Department of Cardiovascular Surgery, University Hospital Freiburg, Freiburg, Germany

We recently presented a method for the quantitative determination of the arterial input function for bolus tracking perfusion imaging. Here we present evaluation of cerebral blood flow obtained with the new method in comparison with 15H2O Positron-Emission-Tomography (PET) in the porcine model (N=13). In contrast to previous studies, we do not employ any adjustable parameters. The CBF values obtained with both methods correlate significantly, but MRI CBF is systematically lower. Present results create a quantitative basis for discussing the role of delay and dispersion in as well as the principal difference between PET and MRI perfusion measurements.