Joint Annual Meeting ISMRM-ESMRMB 2014 10-16 May 2014 Milan, Italy


DIFFUSION (16:00-18:00)

2553-2566 Diffusion: Acquisition Strategies
2567-2599 Diffusion Analysis
2600-2616 Non-Gaussian Diffusion
2617-2643 Diffusion Biophysics & Microstructure
2644-2661 Diffusion-Weighted Imaging Phantoms & Validation 
2662-2672 Tractography Connectivity
2673-2696 Diffusion: Applications

Diffusion: Acquisition Strategies

Wednesday 14 May 2014
Traditional Poster Hall  16:00 - 18:00

2553.   High-Resolution Diffusion Tensor Imaging (DTI) of the Human Kidneys using a Free-Breathing Multi-Slice Targeted-FOV Approach
Rachel W Chan1, Constantin von Deuster2,3, Christian T Stoeck2, Jack Harmer3, Sebastian Kozerke2,3, and David Atkinson1
1University College London, London, London, United Kingdom, 2University and ETH Zurich, Zurich, Zurich, Switzerland, 3King's College London, London, London, United Kingdom

Fractional anisotropy (FA) obtained by diffusion tensor imaging (DTI) can be used to non-invasively assess kidney function. A multi-slice targeted FOV technique that uses a non-coplanar application of excitation and refocusing pulse was extended to free-breathing kidney DTI with a navigator-triggered technique. The purpose of this study was to obtain high-resolution FA and diffusion-tensor maps in healthy subjects who were scanned with two (dual- and single-kidney) targeted FOV scans. The FA maps showed consistency between the two targeted FOVs and across subjects. The medulla and cortical FA values, quantified over multiple contiguous slices, were well-differentiated.

2554.   A Parallel Imaging and Compressed Sensing Combined Framework for Accelerating High-resolution Diffusion Tensor Imaging Utilizing Inter-image Correlation
Xinwei Shi1,2, Xiaodong Ma2, Wenchuan Wu2, Feng Huang3, Chun Yuan2,4, and Hua Guo2
1Department of Electrical Engineering, Stanford University, Stanford, CA, United States, 2Center for Biomedical Imaging Research, Tsinghua University, Beijing, Beijing, China,3Philips Healthcare, FL, United States, 4Department of Radiology, University of Washington, Seattle, WA, United States

Increasing acquisition efficiency is always a challenge in high-resolution diffusion tensor imaging (DTI), which has low SNR and is sensitive to image artifacts. In this work, a parallel imaging and compressed sensing combined reconstruction framework is proposed, which features multi-shot motion error correction, parallel imaging kernel calibration and anisotropic sparsity model utilizing inter-image correlation tailored for high-resolution DTI. The proposed method, titled as AS-SPIRiT, is implemented based on multi-shot variable density spiral, and evaluated in in-vivo brain DTI experiment. Compared with traditional parallel imaging methods and other sparsity models, AS-SPIRiT provides better preserved image quality and more accurate DTI parameters.

2555.   Single-shot and Readout Segmented EPI: Geometric Fidelity of 3T Prostate DWI
Andriy Fedorov1, Kemal Tuncali1, Lawrence P. Panych1, Janice Fairhurst1, Clare Tempany1, and Stephan E. Maier1
1Department of Radiology, Brigham and Women's Hospital, Boston, MA, United States

We compare image quality and distortion in the prostate diffusion-weighted MRI using single-shot EPI (SS-DWI) and multi-shot readout segmented EPI (MS-DWI) in clinical patients (N=12) undergoing in-bore MRI-guided prostate biopsy. The use of MS-DWI led to marked reduction of distortion under conditions that resulted in non-diagnostic SS-DWI images, with moderate increase in scan time (2 vs 3:30 min). Image quality and distortion severity were strongly correlated with the presence of air for SS-DWI, but not for MS-DWI. Distortion reduction agreed with the theoretically expected values. MS-DWI is thus preferable for improved accuracy of prostate target localization and interventional applications.

2556.   DWI Gradient Optimization for Large Spatial Coverage
Jiazheng Wang1 and Yongchuan Lai2
1STO-MR, GE Healthcare, Beijing, Beijing, China, 2STO-MR, GE Healthcare, Beijing, China

Gradient heating and TE are two limiting and mutually restrictive parameters in DWI scan. This work presents a gradient optimization method to reduce gradient heating without sacrificing TE, and quantitatively demonstrates that the method can significantly increase the spatial coverage in slice direction with diffusion imaging. In addition, since this method utilizes diffusion gradients with very short high-amplitude plateau, it theoretically has less sensitivity to motion effects. The proposed method also shows some benefits in eddy currents, leading to sharper subtle structures due to reduced distortion.

2557.   Feasibility of Diffusion Tensor Imaging with Magnetic Resonance Fingerprinting
Ken Sakaie1
1Imaging Institute, The Cleveland Clinic, Cleveland, OH, United States

The magnetic resonance fingerprinting (MRF) framework has a number of attractive features for quantitative imaging such as speed, precision and robustness against artifact. We examine, by simulation, the potential of MRF for diffusion MRI.

2558.   Single and Multiple Shell Sampling Design in dMRI Using Spherical code and Mixed Integer Linear Programming
Jian Cheng1, Pew-Thian Yap1, and Dinggang Shen1
1University of North Carolina at Chapel Hill, chapel Hill, NC, United States

We propose a integer linear programming framework to design single/multi-shell sampling schemes in diffusion MRI.

2559.   Single-shot isotropic diffusion weighting with eddy current compensation
Eric Gibbons1, John Pauly2, and Adam Kerr2
1Department of Bioengineering, Stanford University, Stanford, California, United States, 2Department of Electrical Engineering, Stanford University, Stanford, California, United States

We present a method to incorporate isotropic diffusion weighting into a twice-refocused spin-echo (TRSE) preparation with a single image acquisition. The gradient design is optimized to compensate for eddy current effects of a given time constant and to minimize the TE. By doing this, images with isotropic diffusion contrast are obtained in three times faster than the standard acquisition procedures while also preserving edge sharpness and geometric integrity.

2560.   Readout-Segmented Diffusion Tensor Imaging (RS-DTI) Acceleration Using Simultaneously Acquired Slices
Eric Peterson1, Samantha Holdsworth1, Rafael O'Halloran1, Eric Aboussouan1, and Roland Bammer1
1Radiology, Stanford University, Stanford, CA, United States

The advent of slice accelerated imaging has allowed the significant speedup of diffusion tensor imaging. Slice accelerated imaging excels at accelerating imaging which has a relatively long repetition time, such as readout segmented imaging, which is inherently a dual-echo imaging technique and typically has a repetition time of over 100ms. This work demonstrates that the image quality of diffusion tensor readout segmented imaging is comparable to non-slice accelerated imaging, despite the acquisition being at least 2 times faster.

2561.   Absolute Temperature Measurement of QC Diffusion Phantoms via Low Bandwidth EPI
Thomas L. Chenevert1, Dariya I. Malyarenko1, Michael A. Boss2, and Scott D. Swanson1
1Radiology, University of Michigan, Ann Arbor, Michigan, United States, 2Electromagnetics Division, National Institute of Standards and Technology (NIST), Boulder, Colorado, United States

Phantoms to assess diffusion measurement accuracy require knowledge of media temperature. Proton resonant frequency shift derived by phase difference, MRS, or echo interference pattern have been used to infer temperature. Thulium-based MR thermometry offers greater sensitivity, but requires wide frequency range. In this work, an EPI sequence is used to estimate the temperature-dependent spatial distance between two chemical shift targets. Sensitivity is improved by low bandwidth EPI and long-T2 chemical moieties. Spatial separation of two targets for temperature calibration is automatically determined using cross correlation. The proposed methodology is evaluated for absolute in-situ MR thermometry in a multi-component diffusion phantom.

2562.   Diffusion-Weighted 3D Multi-Slab EPI for Clinical Imaging
Mathias Engström1,2, Magnus Mårtensson1,3, Ola Norbeck2, Enrico Avventi1, and Stefan Skare1,2
1Clinical Neuroscience, Karolinska Institutet, Stockholm, Stockholm, Sweden, 2Neuroradiology, Karolinska University Hospital, Stockholm, Stockholm, Sweden, 3EMEA Research and Collaboration, GE Applied Science Laboratory, GE Healthcare, Stockholm, Sweden

A Diffusion-Weighted 3D Multi-Slab EPI protocol is presented as an alternative to 2D Diffusion-Weighted single-shot EPI for clinical imaging of the brain, when high-resolution and high-SNR is required.

2563.   Common-Information enhanced SPIRiT for high resolution VDS DWI reconstruction
Xiaodong Ma1, Feng Huang2, Xinwei Shi1, Wenchuan Wu1, Binbin Sui3, and Hua Guo1
1Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, Beijing, China, 2Philips Research China, Beijing, China, 3Department of Neuroradiology, Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China

Multi-shot DWI requires long scan time especially in diffusion tensor imaging (DTI). Parallel imaging reconstruction (CG-SENSE) suffers from low SNR when relatively large reduction factor is used. Existence of isotropic diffusion provides common information among different directions, which is utilized in this study through an interleaved acquisition scheme to enhance image reconstruction. Illustrated as an example, Common inhanced SPIRiT (CI-SPIRiT) reconstruction method in VDS DTI is proposed. Preliminary results show that it improves data sampling efficiency and obtains images of higher SNR.

2564.   3-T high b-value 1000 to 10000 s/mm² diffusion weighted MR imaging in healthy volunteers
Julia Reinhardt1, Tilman Schubert1, Michael Amann1,2, and Christoph Stippich1
1Division of Diagnostic and Interventional Neuroradiology, Department of Radiology, University Hospital Basel, Basel, Basel, Switzerland, 2Department of Neurology, University Hospital Basel, Basel, Switzerland

DWI is increasingly applied in the whole field of diagnostic imaging. Here we evaluated applicability of b-values from 1000-10000s/mm2 in a collective of healthy volunteers regarding SNR and overall image quality using a 3T-Scanner with a gradient strength of 80mT/m. The SNR values decrease exponentially. The b-values of grey matter structures drop more pronounced with increasing b-values as compared to white matter or mixed brain tissue, which may be exploited as additional diagnostic information. In this work we were able to demonstrate that DWI with b-values up to 10000s/mm2 with still reasonable SNR can be achieved with high gradient-strength MR-scanners.

2565.   Evaluation of Advanced Monopolar and Bipolar Whole Body Diffusion Weighted Imaging at 3T
Michael A. Jacobs1, Li Pan2, Doris G. Leung3, and John A. Carrino4
1Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States, 2Center for Applied Medical Imaging, Siemens Corporation Corporate Technology, Baltimore, MD, United States, 3Center for Genetic Muscle Disorders, Kennedy Krieger Institute, Baltimore, MD, United States,4Russell H. Morgan Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, MD, United States

The use of multiparametric whole body imaging is rapidly gaining favor in conducting non-ionizing interrogation of the whole body in a short period of time. The use of functional parameters are needed to better define tissue characteristics, in particular, with the use of DWI. We have tested and demonstrated improved DWI with ADC mapping using advanced pulse sequences incorporating mono- and bipolar gradients schemes during continuous table movement WB-MRI in a group of subjects.

2566.   Anisotropic and isotropic MPG comparison for better depiction of pyramidal tract in the patients
Yuichi Suzuki1, Yoshitaka Masutani1, Kuniaki Saito2, Akira Kunimatsu1, Akitake Mukasa2, Masaki Katsura1, Katsuya Maruyama3, Thorsten Feiweier4, Kenji Ino1, Yasushi Watanabe1, Takeo Sarashina1, Masami Goto1, Jiro Sato1, Keiichi Yano1, Nobuhito Saito2, and Kuni Ohtomo1
1Department of Radiology, The University of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan, 2Department of Neurosurgery, The University of Tokyo Hospital, Tokyo, Japan,3Siemens Japan, Tokyo, Japan, 4Health care Neurology Applications Development, Siemens AG, Bavaria, Germany

Our goal is to compare the depiction abilities among our anisotropic MPG set and Jones (isotropic) MPG sets for the brain disease patients.


Diffusion Analysis

Wednesday 14 May 2014
Traditional Poster Hall  16:00 - 18:00

2567.   A Gaussian Process based method for detecting and correcting dropout in diffusion imaging.
Jesper Andersson1 and Stamatios N Sotiropoulos1
1FMRIB-Centre, Oxford, Oxfordshire, United Kingdom

A very sensitive method for detecting and correcting signal dropout in diffusion images has been developed. It is incorporated into a framework for simultaneous correction of all off-resonance distortions and subject movement. When an outlier is detected it is replaced by its predicted value based on a Gaussian Process.

2568.   Strategies for improved correction of EPI distortions in diffusion MRI with blip-up blip-down acquisitions
Mustafa Okan Irfanoglu1,2, Amritha Nayak1,2, Andrew Knutsen3, Pooja Modi1, Joelle Sarlls3, and Carlo Pierpaoli1
1NICHD, NIH, Bethesda, MD, United States, 2CNRM, USUHS, Bethesda, MD, United States, 3NIH, Bethesda, MD, United States

In this work, we propose a novel EPI distortion correction scheme for diffusion weighted images with reversed phase encoding gradient schemes. In addition to describing the proposed method and comparing to existing methodologies, we highlight several important factors affecting these “blip-up blip-down” corrections and analyze the effects of these factors. Our analysis indicated that using additional anatomical image information helps the registration under imperfect data conditions and that using diffusion weighted image contrast along with b=0 s/mm2 image significantly improves anatomical accuracy, especially in tightly packed regions such as the brain stem.

2569.   Motion and eddy-current correction in high b-value diffusion MRI: Systematic registration errors and how to avoid them
Markus Nilsson1, Filip Szczepankiewicz2, Danielle van Westen3, and Oskar Hansson4
1Lund University Bioimaging Center, Lund University, Lund, Sweden, 2Dept. of Medical Radiation Physics, Lund University, Sweden, 3Dept. of Diagnostic Radiology, Lund University, Sweden, 4Clinical Memory Research Unit, Dept. of Clinical Sciences Malmö, Lund University, Sweden

Motion correction of high b-value diffusion MRI data can be performed using the non-diffusion weighted image as reference, but here we show that this conventional motion correction leads to substantial registration errors in terms of misalignment between low and high b-value volumes. We suggest a method that can eliminate this registration error by extrapolating reference volumes from low b-value data to high b-value data. The improved motion correction leads to a reduction in the standard deviation in the FA of up to 40%, which is associated to a large increase in the statistical power of group studies.

2570.   Construction of ground-truth data for head motion correction in diffusion MRI
Jan Hering1,2, Peter F. Neher1, Hans-Peter Meinzer1, and Klaus H. Maier-Hein1,3
1Div. Medical and Biological Informatics, German Cancer Research Center, Heidelberg, Germany, 2Mannheim University of Applied Sciences, Mannheim, Germany, 3Quantitative Image-based Disease Characterization, German Cancer Research Center, Heidelberg, Germany

Retrospective head motion correction counts to the most important post-processing steps in diffusion-weighted MR. However, due to the missing ground-truth, a quantitative evaluation of correction algorithms is possible only to a limited extent. Usage of reference transforms applied to an already aligned data is restricted to translation, as the diffusion signal is not invariant under rotation. We present a novel method for construction of ground-truth head motion data using the Fiberfox tool for realistic diffusion-weighted signal simulation. We further show that the rotation must not be neglected in motion correction and evaluation.

2571.   Improved motion correction using interleaved b=0 volumes and b-vector correction in DTI
Benjamin R Morgan1, Wayne Lee1, and Margot J Taylor1,2
1Hospital for Sick Children, Toronto, Ontario, Canada, 2University of Toronto, Toronto, Ontario, Canada

Diffusion imaging acquisitions are sensitive to head motion, making the collection of a large number of directions problematic, especially in motion-prone populations, such as children. In this study, we propose splitting long acquisitions into separate, shorter acquisitions and including interleaved b=0 reference volumes to facilitate improved motion and b-vector correction. A novel procedure for preprocessing motion-corrupted data collected in this manner is introduced and compared to the standard eddy correction algorithm. Preliminary evidence, using a series of motion-free and motion-corrupted datasets acquired on one healthy adult, shows an advantage to the proposed technique in fractional anisotropy and principle eigenvector estimation.

2572.   Super-resolution reconstruction of diffusion parameters from multi-oriented diffusion weighted images
Gwendolyn Van Steenkiste1, Ben Jeurissen1, Paul Parizel2, Dirk H.J. Poot3,4, and Jan Sijbers1
1iMinds Vision Lab, University of Antwerp, Wilrijk, Antwerp, Belgium, 2department of Radiology, University of Antwerp, Antwerp, Belgium, 3Imaging Science and Technology, Delft University of Technology, Delft, Netherlands, 4BIGR (dept. of Medical informatics and Radiology), Erasmus Medical Center Rotterdam, Rotterdam, Netherlands

Diffusion weighted (DW) images are acquired with a low spatial resolution to obtain a reasonable signal-to-noise ratio within a clinically feasible scan time. Recently, a method has been proposed that improves this trade-off by acquiring multiple anisotropic DW images with different slice orientations, and recovering the underlying high resolution (HR) DW images via super-resolution reconstruction (SRR). Here, we present an improved method (SRR-DTI) which includes the diffusion tensor model. We show using whole brain tractography that fiber tracking in a SRR-DTI data set is more accurate than in a HR DW data set acquired within the same scan time.

2573.   Post-processing of diffusion-weighted MR data lowers the accuracy of the weighted linear least squares estimator
Jelle Veraart1 and Jan Sijbers1
1Vision Lab, University of Antwerp, Antwerp, Belgium

For clinically relevant SNR values (SNR>2), the weighted linear least squares estimator is theoretically expected to be as accurate as advanced estimators that incorporate prior knowledge of the data distribution in the estimation of DTI/DKI model parameters. However, one must bear in mind that the high accuracy vanishes if magnitude operations are applied prior to model fitting. After magnitude operations, which are generally included in the diffusion MRI processing pipeline, the prior knowledge of the noise parameter becomes a must in order to define an unbiased estimator.

2574.   A Model-Free Unsupervised Method to Cluster Brain Tissue Directly From DWI Volumes
Matthew Liptrot1 and François Lauze1
1Department of Computer Science, University of Copenhagen, Copenhagen, Copenhagen, Denmark

We present a simple, novel approach to the voxelwise classification of brain tissue acquired with diffusion-weighted imaging (DWI). By working directly upon the individual DWI volume data, it makes no assumption of an underlying diffusion model. In addition, by summarising statistics across the diffusion gradient directions, we obtain features that are rotationally invariant. We show an example of how well a resulting cluster spatially matches a high FA region, thereby corresponding to probable single-tract voxels. The method could have application during tractography pre-processing, and has potential as a complementary approach for analysis of DWI datasets.

2575.   Influence of Post Diffusion Tensor Image Processing on FA Measure of Myocardial Infarction in Porcine Model
Feng Yang1, Yue-Min Zhu2, Maria A. Zuluaga3, and Pierre Croisille2
1School of Computer and Information Technology, Beijing JiaoTong University, Beijing, China, 2CREATIS, CNRS UMR 5220; Inserm U 1044; INSA of Lyon; University of Lyon, Lyon, France, 3Centre for Medical Image Computing, University College London, London, United Kingdom

We use diffusion tensor magnetic resonance imaging to investigate the effects on fractional anisotropy of diffusion tensor interpolation methods in the presence of myocardial infarction. Our results suggest that precaution should be taken with diffusion tensor interpolation when using absolute indexes (as the FA value) to distinguish infarction and remote regions, since interpolation methods may affect FA values in a non-negligible manner.

2576.   Precision and accuracy of intravoxel incoherent motion (IVIM) MRI: applicability in well-perfused tissues
Mie Kee Lam1, Clemens Bos1, Chrit T W Moonen1, Max A Viergever1, and Lambertus W Bartels1
1Image Sciences Institute, UMC Utrecht, Utrecht, Utrecht, Netherlands

IVIM MRI allows extraction of perfusion and diffusion information from diffusion weighted MR data and is receiving interest for use in well-perfused organs. Monte Carlo simulations were used to investigate the precision and accuracy of IVIM parameter estimation. To achieve acceptable precisions, unrealistically high SNRs are required for perfusion fractions typical of brain. At perfusion fractions typical of well-perfused organs, acceptable precisions and accuracies can be achieved with realistic SNRs. However, at high perfusion fractions systematic errors may become more prominent.

2577.   Investigation of artificial increase of fractional anisotropy (FA) due to truncation artifact in DTI data and compensation using total variation constrained data extrapolation
Daniel Güllmar1, Ferdinand Schweser1, and Jürgen R Reichenbach1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany

Artificial increase in fractional anisotropy occurs due to truncation artifacts in b0 (unweighted) images in DTI data. This artifact can be reduced using total variation constrained data extrapolation. Uncorrected and corrected data were used to obtain FA maps and the differences were investigated in a detailed ROI based analysis. This analysis showed a clear dependence of the artifact with respect to pial surface distance as expected from the theory.

Gabriel Varela1, Alexandra Tobisch2,3, Tony Stoecker2, and Pablo Irarrazaval1,4
1Biomedical Imaging Center - Pontificia Universidad Catolica de Chile, Santiago, Metropolitan District, Chile, 2German Center of Neurological Diseases, North Rhine-Westphalia, Germany, 3University of Bonn, North Rhine-Westphalia, Germany, 4Department of Electrical Engineering, Pontificia Universidad Catolica de Chile, Metropolitan District, Chile

Compressed Sensing allows accelerating Diffusion Spectrum Imaging (DSI) acquisitions by reconstructing the Ensemble Average Propagator from a significantly reduced number of q-space samples. Nevertheless, the reconstruction performance is highly dependent on the sparse domain, which has not been fully studied for the specific DSI application. In this work we propose a new sparse domain based on Curvelets, a multi-resolution geometric analysis that incorporates explicitly an angular decomposition with parabolic scaling and location to characterize bounded curve-singularities in a sparse matter. We show that this domain allows even higher accelerating factors for DSI and thus significantly shortening the scan time.

2579.   BRANDI: Bayesian Regularisation of Advanced Neurological Diffusion Imaging
Susan Doshi1, Derek Jones2, and Daniel Barazany2,3
1Computer Science and Informatics, Cardiff University, Cardiff, Glamorgan, United Kingdom, 2CUBRIC, Cardiff University, Cardiff, United Kingdom, 3Department of Neurobiology, Tel Aviv University, Tel Aviv, Israel

We use Bayesian statistical modelling to regularise parameter estimates in advanced diffusion imaging. By incorporating prior knowledge (such as spatial smoothness) during estimation, we exploit the information more fully than applying smoothing as post-processing. We use a Markov random field for the prior probability. This approach allows the possibility of non-isotropic smoothing, and for edges in one part of the data to guide the fitting of other parts. We demonstrate the approach with CHARMED data, using ex-vivo porcine spinal cord as a biological phantom. The parameter estimates in homogeneous areas are smooth (agreeing with our prior belief), with edges preserved.

2580.   Use of the Median Image Mitigates Effects of Respiratory Motion in Abdominal Diffusion Imaging
Neil P Jerome1, Matthew R Orton1, James d'Arcy1, Thorsten Feiweier2, Dow-Mu Koh3, David J Collins1, and Martin O Leach1
1CR-UK and EPSRC Cancer Imaging Centre, The Institute of Cancer Research, Sutton, Surrey, United Kingdom, 2Imaging & Therapy Division, Siemens AG, Erlangen, Germany,3Department of Radiology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom

Respiratory motion commonly confounds abdominal DWI, and motion minimisation strategies adversely affect scan efficiency and comfort. Blurring is due to post-acquisition combination of images from separate signal averages and diffusion-gradient directions, and is not inherent to the images. In a volunteer cohort where all images were stored separately, taking a (voxel-by-voxel) median image instead of a mean at each b-value yields parameter maps with much improved sharpness while still retaining tissue features. ADCs from ROIs in liver and kidneys were 108±18 vs 120±26 (p=0.007) and 182±17 vs 188±13 (p=0.04) x10-5 mm2s-1 for median and mean, respectively.

2581.   Robust estimation with suppressed image blurring for diffusion kurtosis imaging using selective spatial smoothing filter
Suguru Yokosawa1, Hisaaki Ochi1, Yoshitaka Bito2, Kenji Ito3, and Makoto Sasaki3
1Central Research Laboratory,Hitachi, Ltd., Kokubunji-shi, Tokyo, Japan, 2MRI System Division, Hitachi Medical Corporation, Chiba, Japan, 3Division of Ultrahigh Field MRI, Institute for Biomedical Science, Iwate Medical University, Iwate, Japan

In this work, we proposed a robust estimation method for DKI that reduces noise while suppressing image blurring. In our method, instead of being applied to all image data, a spatial smoothing filter is applied only to voxel dataset that contain outliers. These outliers are detected by deviation of calculated DKI coefficient from constrained condition. We demonstrated that the proposed method obtains a MK map with less blurring than constrained fitting with spatial smoothing and reduces pepper noises. The results confirm the effectiveness of our method applied in clinical DKI.

2582.   MASSIVE: Multiple Acquisitions for Standardization of Structural Imaging Validation and Evaluation
Martijn Froeling1, Chantal M.W. Tax2, Sjoerd B. Vos2, Peter R. Luijten1, and Alexander Leemans2
1Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands, 2Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands

For this studie we have acquired multiple anatomical scans and a diffusion data set containing 8000 diffusion weighted volumes, consisting of five shells and two Cartesian grids. Our dataset, coined Multiple Acquisitions for Standardization of Structural Imaging Validation and Evaluation (MASSIVE), allows for comparison of various techniques for e.g., registration, segmentation, tractography, clustering, denoising/ regularization and bootstrapping, eliminating the bias of variable data acquisition and sub-optimal sampling schemes.

2583.   INVERSION: A robust method for co-registration of MPRAGE and Diffusion MRI images
Chitresh Bhushan1, Justin P. Haldar1, Anand A. Joshi1, David W. Shattuck2, and Richard M. Leahy1
1Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California, United States, 2Department of Neurology, University of California, Los Angeles, California, United States

Accurate registration between MPRAGE and diffusion MRI images is essential for many multi-modal neuroimaging studies. We describe a new method, INVERSION (Inverse contrast Normalization for VERy Simple registratION), that robustly aligns MPRAGE and b=0 s/mm2 images by leveraging known "inverted" contrast relationships between these two modalities. We transform the contrast of the b=0s/mm2 image to match the contrast of the MPRAGE image, and achieve consistently accurate registration using the simple sum of squared differences cost function. Unlike most multi-modal registration approaches, INVERSION uses a locally smooth, and frequently convex, cost function that is relatively easy to numerically optimize.

2584.   Patient Centered Registration and Analysis of Diffusion MRI for Robust Detection of Spatially Varying Microstructural Changes
Asif K Suri1,2, Roman Fleysher1, and Michael L Lipton1,3
1Albert Einstein College of Medicine, Bronx, NY, United States, 2Bronx Psychiatric Center, Bronx, NY, United States, 3Montefiore Medical Center, Bronx, United States

Brain registration of a subject and set of controls to a template is an essential step in determining diffusion abnormalities obtained from MR diffusion imaging. Limitations in the registration process compounded with use of a canonical brain atlas, results in misregistrations that can result in erroneous identification of abnormal diffusion values within subjects. This study attempts to reduce misregistrations using subject based template, which increases the accuracy of registration. This strategy demonstrates a substantial decrease in volume of abnormally low FA attributed to the improved accuracy of registration and can have useful clinical applications.

2585.   Automated detection of brain regions associated with post-stroke depression: A hypothesis
Jhimli Mitra1, Jurgen Fripp1, Kaikai Shen1, Kerstin Pannek1, Pierrick Bourgeat1, Olivier Salvado1, Bruce Campbell2, Susan Palmer3, Leeanne Carey3, and Stephen Rose1
1The Australian e-Health Research Centre, CSIRO Computational Informatics, CSIRO Preventative-Health Flagship, Herston, QLD, Australia, 2Department of Medicine and Neurology, Melbourne Brain Centre at the Royal Melbourne Hospital, Parkville, VIC, Australia, 3The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia

Our hypothesis is that loss-in-connectivity in brain regions post-stroke is correlated with post-stroke depression (PSD). We propose an automated detection of cortical/sub-cortical regions that are associated with PSD. The method involves pairwise comparison of network connectivity matrices between normal and stroke patients using diffusion tractography and network based statistics to identify the networks affected by ischemic stroke. Then a groupwise linear regression analysis is performed between the loss-in-connectivity in each brain region and the respective patients' depression scores at 3 month post-stroke stage. The results revealed positive correlations between loss-in-connectivity and PSD in some brain regions including the thalamus.

2586.   Optimization of ROI transposition for atlas-based analysis of MRI quantitative metrics in neuroimaging studies
Mustafa Okan Irfanoglu1,2, Amritha Nayak1,2, Lindsay Walker3, Carlo Pierpaoli1, and The Brain Development Cooperative Group4
1NICHD, NIH, Bethesda, MD, United States, 2CNRM, USUHS, Bethesda, MD, United States, 3Brown University, RI, United States,, MD, United States

In analyzing quantitative MRI metrics in large population neuroimaging studies, it is convenient to define ROIs on a representative atlas and then transpose the ROIs onto individual subject space and extract values. Here we assess the contribution to overall variance that different ROI transformation methods introduce on the analysis of developmental trajectories of the diffusion MRI pediatric neuroimaging project, a large database of more than 400 subjects age 0-20. We find that the contribution to overall variance varies significantly with various methods and we propose a novel strategy that is more robust than previous approaches.

2587.   The Variation of MAP-MRI –derived Parameters along White Matter Fiber Pathways in the Human Brain
Alexandru V Avram1, Alan S Barnett1,2, and Peter J Basser1
1Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, MD, United States, 2The Henry Jackson Foundation, Bethesda, MD, United States

Scalar indices derived from diffusion weighted MR images (DWIs) provide invaluable clinical information for characterizing changes in brain microstructure and cytoarchitecture. In this study we apply the recently developed mean apparent propagator (MAP)-MRI framework to quantify the brain diffusion properties in healthy volunteers and describe and interpret the variation of scalar descriptors of the MAP (such as zero-displacement probability, non-gaussianity and propagator anisotropy) along the major white matter fiber pathways and discuss the clinical significance of our findings.

2588.   Il Gatto Sta Ingrassando: Novel Connectivity Tools and Additions in AFNI-FATCAT
Paul A Taylor1,2 and Ziad S Saad3
1Faculty of Health Sciences, University of Cape Town, Cape Town, Western Cape, South Africa, 2African Institute for Mathematical Sciences, South Africa, 3NIMH, National Institutes of Health, Bethesda, MD, United States

We present developments in the AFNI-FATCAT suit of tools for analyzing MRI functional and structural connectivity. Improvements include: enhanced deterministic tracking to utilize voxelwise uncertainty; increased options for combatting false positives and negatives with including multi-directional tracking and anti-masking ROIs; combined visualization with SUMA and AFNI, allowing interactive manipulation of tracking and regions. These additions to AFNI-FATCAT increase researchers' capabilities for integrating functional and diffusion-based tractographic connectivity.

2589.   Validation of a tract-based automatic analysis by comparison with manual tractography
Yu-Jen Chen1, Yun-Chin Hsu1, Yu-Chun Lo1, and Wen-Yih Isaac Tseng1
1Center for Optoelectronic Medicine, National Taiwan University College of Medicine, Taipei, Taipei, Taiwan

In this study, we proposed a whole brain tract-specific analysis using a high quality DSI template, predetermined tracts in the template, and LDDMM coregistration method. Compared to manual approach, TBAA showed higher overlap of tract positions and smaller variability of the sampled GFA. In conclusion, TBAA overcomes the problem of variability in manual tractography on individual DSI, and is potentially useful in high-throughput tract-specific analysis of the whole brain.

2590.   A new compression format for tractography datasets reconstructed from dMRI
Caroline Presseau1, Pierre-Marc Jodoin1, and Maxime Descoteaux1
1University of Sherbrooke, Sherbrooke, Quebec, Canada

Fiber tracking dataset are heavy to compute, but also difficult to visualize and hard to store on disk (especially when dealing with a collection of brains). These problems call for a fiber-specific compression. As of today, no fiber compression format has yet been adopted and the need for it is now becoming an issue for future connectomics research. In this work, we propose a new compression format for tractography datasets reconstructed from diffusion magnetic resonance imaging (dMRI)

2591.   Simulated DW-MRI Brain Data Sets for Quantitative Evaluation of Estimated Fiber Orientations
Bryce Wilkins1, Namgyun Lee1,2, Meng Law1,3, and Natasha Leporé1,4
1Biomedical Engineering, University of Southern California, Los Angeles, California, United States, 2Center of Magnetic Resonance Research, Korea Basic Science Institute, Ochang, Korea, 3Radiology, Keck School of Medicine of USC, Los Angeles, California, United States, 4Radiology, Children's Hospital of Los Angeles, California, United States

This abstract describes the development of simulated DW-MRI brain images and quantitative tools for evaluating the performance of diffusion analysis methods in terms of fiber orientation estimation and false-positive/-negative fiber rates, which are of fundamental importance to tractography based studies. Synthetic data is generated at SNRs of 9, 18 and 36, using sets of 20, 30, 40, 60, 90 and 120 gradient directions, at diffusion-weighting of b=1000 common to clinical acquisitions. We illustrate correspondence between in-vivo and synthetic data analysis, and provide an example of quantitative results obtained from six well-known DW-MRI analysis methods.

2592.   Evaluating the accuracy of diffusion models at multiple b-values with cross-validation
Ariel Rokem1, Kimberly L Chan1, Jason D Yeatman1, Franco Pestilli1, Aviv Mezer2, and Brian A Wandell2
1Stanford University, Stanford, CA, United States, 2Stanford University, Stanford, California, United States

Models of diffusion MRI (DWI) are used for inferences about the properties of the tissue and fiber orientations. Though stability of DWI model parameters is often evaluated, there are no extensive studies of model prediction accuracy. We evaluated different models using cross-validation in a test-retest data set and data from the Human Connectome Project. In most of the white matter and multiple b-values, we find that the classic diffusion tensor model predicts the data more accurately than test-retest reliability. However, modeling the signal as a combination of contributions from distinct white matter fascicles provides more accurate model predictions.

2593.   Using Spherical Harmonic Functions for Residual Bootstrap Analysis of HARDI
Bagrat Amirbekian1,2 and Roland G. Henry1,2
1Graduate Program in Bioengineering, UC San Francisco and UC Berkeley, San Francisco, CA, United States, 2Neurology, UC San Francisco, San Francisco, CA, United States

Spherical harmonic (SH) functions have been widely used to fit HARDI data, but residual bootstrap methods have mostly focused on other models for fitting this data. Here we use the example of estimating SNR to show that bootstrap estimates, using the SH functions, are accurate for many choices of maximum SH order. Additionally we show that for good precision of those estimates, the maximum SH order must be high enough to fit the data well and low enough to preserve sufficient degrees of freedom.

2594.   Investigation of Number of Direction Selection for Joint Reconstruction in Multiple-direction Diffusion Imaging
Xiaodong Ma1, Feng Huang2, and Hua Guo1
1Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, Beijing, China, 2Philips Research China, Beijing, China

In DWI, common information from other diffusion direction can be shared to increase the image quality of one diffusion direction. However, inappropriate selection of complementary information may provide suboptimal image results. In this study, we systematically compared the performance of common information enhanced reconstruction when different direction numbers are used for the image calculation. Results show that care should be taken when including other directions for one direction reconstruction in multiple direction DWI or high angular diffusion imaging.

2595.   Artifact correction based on diffusion coefficient
Gregory Lemberskiy1,2, Dmitry S Novikov1, and Els Fieremans1
1New York University School of Medicine, Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York, NY, United States, 2Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, United States

DWI images in the body are often afflicted with systematic vibration artifacts (SVA), characterized by localized regions of signal dropout. Generalized image processing techniques, such as outlier detection and histogram-based methods, require either large datasets or cannot account for nonlinear phenomena such as RF inhomogeneity. To overcome these limitations, we propose a rejection scheme based on unphysical diffusion coefficient values of the directional ADC, called Artifact Correction based on Diffusion Coefficient (ACDC). ACDC does not require many directions or averages to be efficient. Hence, its implementation in clinical systems would be straightforward.

2596.   The Performance of NODDI Estimation Using a Common 2-Shell Protocol
Zhen Wang1, Yuan Wang1, Jianye Zhang1, Xu Yan2, Hui Liu2, and Zeping Xiao1
1Shanghai Mental Health Center, Shanghai, China, 2MR Collaboration NE Asia, Siemens Healthcare, Shanghai, China

The study tested the estimation accuracy of Neurite orientation dispersion and density imaging (NODDI) using a common 2-shell protocol with the same gradient direction at each shell. The experiment used visual and quantitative comparisons to demonstrate that the common 2-shell protocol had very similar performance as the optimized NODDI protocol, but is easy to configure in a commercial scanner, thus can be widely adopted in clinical study.

2597.   DWI-Thermometry Study on Differences by Imaging Conditions of LV Temperature Measurements and Its Temperature Changes by Tympanic Temperature
Kentaro Akazawa1, Koji Sakai2, Rennie, Yung-Chieh Chen3, Jun Tazoe1, Kaori Nishida1, Akiko Takahata1, Mariko Goto1, Koshi Terayama1, and Kei Yamada1
1Department of Radiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Kyoto, Japan, 2Department of Human Health Science, Graduate School of Medicine, Kyoto, Kyoto, Japan, 3Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taipei, Taiwan

Diffusion-weighted image (DWI)-thermometry is one of the most clinically applicable approaches among some magnetic resonance methods. The DWI-based method calculates the temperature of cerebrospinal fluid based on diffusion coefficient of the lateral ventricles. However, the technique is relatively recent and insufficient yet in its analysis. We, therefore, need further evaluation. The results revealed that lateral ventricular (LV) temperature measurement was successfully performed using DWI-thermometry, slice thickness had significant effect on the calculation of LV temperature, and thinner slice thickness was considered to produce better results than the thick slices. Also we found that LV temperature would change with tympanic temperature.

2598.   The comparison of diffusion and perfusion characteristics among the different types of uterine fibroids based on T2WIs: an intravoxel incoherent motion MRI study
Rong Wang1, Hao Fu1, Hui Zhang1, Chenxia Li1, and Jian Yang1
1Department of Radiology, the First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi, China

The prognoses of non-invasive therapies such as magnetic resonance-guided focused ultrasound surgery (MRgFUS) and GnRH analogue of uterine leiomyomas were proved have a relationship with the signal intensity of tumor on T2WI. However the reason is not definite yet. We performed Intravoxel incoherent motion (IVIM) MR study on a cohort of patients to compare the diffusion and perfusion characteristics of uterine fibroid with different T2WI type. The results indicated that the cellularity is tighter in Type 1 and looser in Type 3 among 3 fibroid types, whereas perfusion parameters of Intravoxel incoherent motion (IVIM), seem no differences among them. Thus, the present results implied that IVIM technique facilitated the understanding of the tissue characteristics in uterine fibroid and proposed to guide patient selection for MRgFUS ablation.

2599.   Accelerating Diffusion Kurtosis Acquisition using SIR and Model-Based Reconstruction
Christopher Lee Welsh1, Edward W Hsu1, and Edward VR DiBella2
1Department of Bioengineering, University of Utah, Salt Lake City, UT, United States, 2Radiology, UCAIR, University of Utah, Salt Lake City, UT, United States

Diffusion kurtosis imaging (DKI) is a way to model tissue microstructure that is more realistic than DTI since it measures the degree of non-Gaussian diffusion. However, DKI requires a long scan time. A model-based strategy is presented to estimate diffusion and kurtosis tensors directly from accelerated k-space data. The accuracy of the model-based method with an acceleration factor of 3 was compared to using all acquired data. The findings suggest the proposed strategy can be used to reduce DKI scan time if used in conjunction with SIR, while still characterizing non-Gaussian diffusion and neural fiber crossings without loss of accuracy.


Non-Gaussian Diffusion

Wednesday 14 May 2014
Traditional Poster Hall  16:00 - 18:00

2600.   An accurate and precise new method for measuring kurtosis of intravoxel incoherent motion
Eizou UMEZAWA1, Daichi ISHIHARA1, and Shota SEKO1
1School of Health Sciences, Fujita Health University, Toyoake, Aichi, Japan

Recently, clinical usefulness of diffusional kurtosis has been reported, e.g., for distinguishing benign from malignant prostate tissues. Measured diffusional kurtosis must contain a systematic error owing to two factors: approximations in method for kurtosis measurement and perfusion. The error is unclear because the true value is still unknown. Clarifying the error is important to improve the kurtosis measurement method and explore its clinical significance. We first investigate the systematic error in measured kurtosis by numerical experiments. We then develop a new method for measuring kurtosis. Finally, we assess clinical significance of the kurtosis obtained by the new method with simulation.

2601.   Diffusional Kurtosis Imaging indicating various tissue of glioblastoma; voxel-by-voxel study
Fumitaka Kumagai1,2, Akira Nishikori1,2, Masaaki Hori2, Yoshitaka Masutani3, Masaki Katsura3, Koji Kamagata2, Kohei Kamiya2, Michimasa Suzuki2, Issei Fukunaga1,2, Nozomi Hamasaki2, Syuji Sato2, Yuriko Suzuki2, Mariko Yoshida2, Hajime Arai4, Hisato Ishii4, Shigeki Aoki2, Atsushi Senoo1, and Akihide Kondo4
1Department of Radiological Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Arakawa-ku, Tokyo, Japan, 2Department of Radiology, Juntendo University School of Medicine, Bunkyo-ku, Tokyo, Japan, 3Department of Radiological Medicine, Graduate School Medicine, University School of Medicine, Bunkyo-ku, Tokyo, Japan, 4Department of Neurosurgery, Juntendo University School of Medicine, Bunkyo-ku, Tokyo, Japan

Diffusional kurtosis imaging (DKI) has been highlighted as a new technique based on non-Gaussian water diffusion analysis. Although recent studies have reported values of diffusional MR imaging in glioma grading, underlining microstructural changes corresponding to changes of diffusion metrics are not fully elucidated. This study investigated differences in DKI metrics among different components within glioblastoma, by means of voxel-by-voxel analysis. This study give us insight and better understanding of changes in diffusion metrics of different tissue components of glioblastoma.

2602.   A fast and robust method for simultaneous estimation of mean diffusivity and mean tensor kurtosis
Brian Hansen1, Torben E. Lund1, Ryan Sangill1, and Sune N. Jespersen1,2
1CFIN/MindLab, Aarhus University, Aarhus, Denmark, 2Dept. of Physics and Astronomy, Aarhus University, Denmark

Diffusion kurtosis imaging (DKI) is a popular extension of diffusion tensor imaging accounting for non-gaussian aspects of diffusion in biological tissue. Several studies have indicated enhanced sensitivity of mean kurtosis (MK) to pathology, including stroke. Recently, we proposed a fast acquisition and postprocessing scheme based on a linear combination of only 13 diffusion weighted images for estimation of the mean tensor kurtosis. Here we extend this scheme by incorporating exact estimation of the mean diffusivity and show that this produces an improved estimate of mean tensor kurtosis across large brain regions. Our extension also permits acquisition b-values to be optimized numerically and the experimental uncertainty and precision to be mapped.

2603.   Observation of brain development in neonates/infants using Diffusional Kurtosis Imaging
Yuichi Suzuki1, Akira Kunimatsu1, Harushi Mori1, Junichi Hata1, Hiroki Sasaki1, Shiori Amemiya1, Yoshitaka Masutani1, Katsuya Maruyama2, Jian Xu3, Yasushi Watanabe1, Kenji Ino1, Masami Goto1, Jiro Sato1, Keiichi Yano1, and Kuni Ohtomo1
1Department of Radiology, The University of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan, 2Siemens Japan, Tokyo, Japan, 3Siemens Medical Solutions USA Inc, Pennsylvania, United States

to evaluate the neonatal/infants brain development with DKI, and to compare the quantitative values derived from DKI with the conventional diffusion value (apparent diffusion co-efficiency [ADC] and fractional anisotropy [FA]).

2604.   Characterization of diffusion complexity in prostate tissue with a stretched biexponential model
Roger M. Bourne1 and Matt G. Hall2
1University of Sydney, Sydney, NSW, Australia, 2University College London, London, United Kingdom

This study explores a development of the conventional biexponential model by adding a stretching factor to the lower diffusivity component. The superior Akaike information content and leave-one-out prediction performance of the stretched over the conventional model at short diffusion time is consistent with the presence of a diversity of diffusion environments experienced by the “slow” component of the models.

2605.   Characterizing Human Brain Microstructure with Mean Apparent Propagator (MAP) MRI
Alexandru V Avram1, Alan S Barnett1,2, Evren Ozarslan1,3, Joelle E Sarlls4, M. Okan Irfanoglu1,2, Elizabeth Hutchinson1,5, Carlo Pierpaoli1, and Peter J Basser1
1Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, MD, United States, 2The Henry Jackson Foundation, Bethesda, MD, United States, 3Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States, 4NINDS, National Institutes of Health, Bethesda, MD, United States, 5Center for Neuroscience and Regenerative Medicine, USUHS, Bethesda, MD, United States

Orientationally invariant measures such as Fractional Anisotropy or mean diffusivity are invaluable for characterizing changes in cytoarchitecture and microanatomical organization of brain tissue during stroke, cancer, neurodegenerative diseases and aging. In this study we apply the recently developed MAP-MRI framework to measure displacement profiles of water molecules in healthy human volunteers. Moreover, we characterize the mean apparent diffusion propagator with novel orientationally invariant scalar measures of zero-displacement probability, non-gaussianity, and propagator anisotropy and evaluate the feasibility of generating such images from clinical acquisitions.

2606.   Q-space signal reconstruction from sparse samples
Yogesh Rathi1, Oleg Michailovich2, Frederik Laun3, and Carl-Fredrik Westin4
1Psychiatry, Harvard Medical School, Boston, MA, United States, 2University of Waterloo, Ontario, Canada, 3German Cancer Research Center, Germany, Germany,4Harvard Medical School, MA, United States

We propose a novel method for reconstructing the diffusion signal in the q-space from very sparsely sampled data spread in over multiple b-values. Our preliminary results on a physical phantom shows that at-least 60 measurements are needed for good reconstruction quality of the data.

2607.   Measurement of axon diameter and axon density of the corticospinal tract in idiopathic normal pressure hydrocephalus by q-space imaging
Kouhei Kamiya1,2, Masaaki Hori1, Yuriko Suzuki3, Atsushi Nakanishi1, Issei Fukunaga1, Koji Kamagata1, Mariko Yoshida1, Masakazu Miyajima4, Hajime Arai4, and Shigeki Aoki1
1Department of Radiology, Juntendo University School of Medicine, Bunkyo, Tokyo, Japan, 2Deparment of Radiology, Graduate School of Medicine, the University of Tokyo, Bunkyo, Tokyo, Japan, 3Philips Electronics Japan, Ltd, Tokyo, Japan, 4Department of Neurosurgery, Juntendo University Graduate School of Medicine, Bunkyo, Tokyo, Japan

The gait disturbance is a characteristic treatable symptom of idiopathic normal pressure hydrocephalus (iNPH), though the etiology is not clear yet. This study evaluated axon diameter and axon density of the cortico-spinal tract (CST) in iNPH patients by using two-component low-q fit method of q-space imaging. Compared with controls, patients with iNPH had increased axon density of the CST running near the lateral ventricle, whereas the axon diameter was not altered. The present results suggest the idea that the gait disturbance in iNPH is not due to irreversible axonal damage, but results from compression and/or stretching of neural tracts.

2608.   Validation of mean apparent propagator MRI
Alan Seth Barnett1,2, Elizabeth Hutchinson1,2, Ferenc Horkay1, Michal Komlosh1,2, Evren Ozarslan3, Carlo Pierpaoli1, and Peter Basser1
1NICHD, NIH, Bethesda, MD, United States, 2CNRM, USUHS, Bethesda, MD, United States, 3Department of Radiology, Harvard Medical School, Boston, MA, United States

Mean apparent propagtor MRI (MAP-MRI) is a method of using diffusion MRI to map tissue microstructure. To evaluate the accuracy and precision of MAP-MRI we use a test system consisting of an array of microscopic cylinders. We use both simulated data, computed using the multiple correlation function (mcf) method, and real diffusion imaging data of a special phantom. We report the accuracy and precision of several MAP parameters as a function of the signal-to-noise ratio of the non-diffusion weighted images.

2609.   Developing new metrics for comparison of diffusion propagators
Luis Miguel Lacerda1, Jonathan I. Sperl2, Gareth Barker1, and Flavio Dell'Acqua1
1Centre for Neuroimaging Sciences, Institute of Psychiatry, King's College London, London, Denmark Hill, United Kingdom, 2GE Global Research, Munich, BY, Germany

Several techniques have been used to explore the information contained in the diffusion propagator. A standard methodology to evaluate such techniques (and the influence of factors such as acceleration methods) is to compare the reconstructed orientation distribution functions against a predefined "gold standard". Nonetheless additional measures may retrieve more information from the diffusion propagator. In this work we present preliminary results that may allow a more robust analysis and comparison of diffusion data and acceleration methods. Specific indices were extracted and appear to be helpful in the characterization of the diffusion propagator and in the comparison of different reconstruction methods

2610.   Greedy NNLS: Fiber Orientation Distribution From Non-Negatively Constrained Sparse Recovery
Aurobrata Ghosh1 and Rachid Deriche1
1Project Team Athena, Inria Sophia Antipolis Méditerranée, Sophia Antipolis, PACA, France

The Fiber Orientation Density (FOD) is a robust method for mapping crossing WM fibers. However, in clinical settings with minimalistic (~30) acquisitions, the FOD is restricted to 4th-6th order SHs, which limits its angular resolution. We proposed a non-negatively constrained sparse recovery of the FOD based on Non-Negative Least-Squares (NNLS) to overcome this limitation. We found NNLS solutions to be constrained and sparse. Here we experimentally compare the NNLS to l1-minimization and find NNLS superior in sparsity & robustness. We conclude by highlighting the greedy design of NNLS, which mirrors Orthogonal Matching Pursuit, and is the cause of its sparsity.

2611.   How to perform best ODF reconstruction from the Human Connectome Project sampling scheme?
Eleftherios Garyfallidis1, Mauro Zucchelli2, Jean-Christophe Houde3, and Maxime Descoteaux3
1University of Sherbrooke, Sherbrooke, Quebec, Canada, 2University of Verona, Italy, 3University of Sherbrooke, Quebec, Canada

The purpose of this work is to compare and extend recent state-of-the-art single-shell and multi-shell local reconstruction techniques for the HCP sampling scheme consisting of three-shells. We are interested in the best ODF reconstruction quantified locally with angular error (AE) and correct number of fibre compartments but most importantly, on the ODF reconstruction that leads to the best overall tractography output evaluated by the Tractometer.

2612.   Interpretation of diffusion MRI data using a gamma distribution model
Koichi Oshio1, Hiroshi Shinmoto2, and Robert Mulkern3
1Department of Diagnostic Radiology, Keio University, Shinjuku-ku, Tokyo, Japan, 2Department of Radiology, National Defence Medical College, Tokorozawa, Saitama, Japan, 3Department of Radiology, Children's Hospital, Boston, MA, United States

Although many models have been proposed to interpret non-Gaussian diffusion MRI data in biological tissues, it is often difficult to see the correlation between the MRI data and the histological changes in the tissue. In this work, a statistical model based on the gamma distribution is proposed. Using this model, the diffusion MR data is well fitted, and histological interpretation of the data is possible.

2613.   High resolution OGSE DTI of ex vivo mouse brain to investigate the frequency-dependence of the apparent diffusion tensor in cerebellar white matter
Jeff Kershaw1, Sayaka Shibata1, Ichio Aoki1, Takayuki Obata2, and Hiroshi Ito1
1Molecular Imaging Centre, National Institute of Radiological Sciences, Chiba, Japan, 2Research Centre for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba, Japan

An earlier study of ex vivo mouse brain was the first to demonstrate that increasing the MPG frequency strongly enhanced the mean diffusivity in the cerebellar granule cell layer of the cerebellum. There was also a much weaker increase for the cerebellar molecular layer. However, no data was presented for the cerebellar white matter (CBWM), which is odd because investigating the diffusion characteristics of white matter is one of the main targets of diffusion-weighted MRI. The present study was performed to address this omission and report the first quantitative OGSE DTI measurements for mouse CBWM.

2614.   Experimental considerations for OGSE of anisotropic tissue
Henrik Lundell1, Casper Kaae Sønderby1, and Tim B Dyrby1
1Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark

Oscillating gradient spin echo (OGSE) experiments offers new insight in tissue microstructure by probing diffusion processes on ultra-short time scales. In this study we examine different possibilities for sampling OGSE on anisotropic tissue. We find that the best results for very limited gradient strength is achieved with square/trapezoidal gradients in 6 gradients, whereas a circularly polarized OGSE (CP-OGSE) perform better at higher gradient strengths. Our results emphasize that the optimal solution is highly dependent on the given limitations and the parameters of interest.

2615.   Biexponential modeling of diffusion in stroma and epithelium of prostate tissue
Ned Charles1, Gary Cowin2, Nyoman Kurniawan2, and Roger Bourne3
1University of Sydney, Camperdown, NSW, Australia, 2University of Queensland, Brisbane, QLD, Australia, 3University of Sydney, Sydney, NSW, Australia

Multi b-value data from 80 micrometer voxels was acquired from fixed prostate tissue in a 16T microimaging system. Biexponential modeling demonstrated distinct regional variations in diffusion behavior that correlate with microscopic tissue structure features. Regions dense in glands have a higher proportion of the lower diffusivity component, and this component has lower diffusivity in the glandular regions than in regions of fibromuscular stroma. An increasing partial volume of low diffusivity epithelial cells, rather than “higher cellularity”, may explain the clinical observation of decreasing ADC as prostate cancer Gleason grade increases.

Characterization of the gray matter in spinal cords of Long Evans shaker rats by double-pulsed-field gradient MRI
Debbie Anaby1, Darya Morozov1, Ian D. Duncan2, and Yoram Cohen1,3
1School of Chemistry, Tel Aviv University, Tel Aviv, Israel, 2Department of Medical Sciences, University of Wisconsin-Madison, Wisconsin, United States, 3Sagol School of Neurosciences, Tel Aviv University, Tel Aviv, Israel

Conventional single-pulsed-field-gradient (s-PFG) methodologies are capable of faithfully depicting diffusion anisotropy in coherently ordered structures. However, microstructure is more difficult to characterize where macroscopic organization is absent. Double-PFG (d-PFG) MR methodologies were recently suggested as an alternative for studying microstructure in such cases. The spinal cords’ white matter (WM) of Long Evans shaker (les) rats, a dysmyelinated model, was recently studied by q-space MRI. Here, we characterize the spinal cords of les rats and their controls by d-PGSE, focusing on the gray matter (GM), in comparison with DTI. d-PFG clearly differentiates between three GM areas of the les spinal cord.


Diffusion Biophysics & Microstructure

Wednesday 14 May 2014
Traditional Poster Hall  16:00 - 18:00

2617.   High resolution diffusion MRI of the unfixed post mortem brain
Christian Langkammer1, Nikolaus Krebs2, Christoph Birkl1, Lukas Pirpamer1, Florian Borsodi1, Michaela Haindl1, Gernot Reishofer3, David Andrew Porter4, Eva Scheurer2, Franz Fazekas1, and Stefan Ropele1
1Department of Neurology, Medical University of Graz, Graz, Austria, 2Ludwig Boltzmann Institute for Clinical-Forensic Imaging, Graz, Austria, 3Department of Radiology, Medical University of Graz, Graz, Austria, 4Siemens Healthcare, Erlangen, Germany

The aim of this study was to investigate the feasibility of high-resolution diffusion MRI in the unfixed human brain as basis for validating diffusion-derived measures with histology.

2618.   An estimate of Gd-DOTA diffusivity in blood by direct NMR diffusion measurement of its hydrodynamic analogue Ga-DOTA
Christian Wieseotte1,2, Manfred Wagner2, and Laura Schreiber1
1Department of Radiology, Section of Medical Physics, Johannes Gutenberg University Medical Center, Mainz, Germany, 2Max Planck Institute for Polymer Research, Mainz, Germany

The diffusivity of contrast agents in the human body is a fundamental property which is still a factor of uncertainty in many applications. The main reason is that due to the highly paramagnetic Gd3+ ion, direct observations by means of nuclear magnetic resonance are not possible. This study pursues the approach of directly measuring the diffusion of the hydrodynamically analogue PET tracer Gd-DOTA in deuterated water. The diffusivity in blood plasma can be calculated by correcting for the higher solvent viscosity. We report a diffusivity of Ga-/Gd-DOTA in blood plasma at 310K of D = 2.92 (0.25)∙10-10 m2s-1.

2619.   Undulating and crossing axons in the corpus callosum may explain the overestimation of axon diameters with ActiveAx
Tim B Dyrby1, Mark Burke2, Daniel C Alexander3, and Maurice Ptito1,4
1Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark, 2Departments of Physiology and Biophysics, Howard University, Washington, United States, 3Centre for Medical Image Computing, University College London, London, United Kingdom, 4School of Optometry, University of Montreal, Montreal, Canada

Axon diameter (AD) estimates from diffusion-weighted imaging (DWI) is known being overestimated when compared with electron microscopy (EM). Mean AD in ten regions across the corpus callosum (CC) was obtained from painstaking EM. The AD’s from DWI using ActiveAx method were found overestimated but similar AD contrast as with EM was observed across CC. With classical histology, undulating axons was observed throughout CC, and crossing axons in genu also. Undulation leads to larger cross-sectional area than straight axons hence AD overestimation. This suggests that macroscopic features as undulating axons can explain the overestimation we observed from AD estimates using DWI.

2620.   A Framework for Joint Diffusion Modelling and Orientation Estimation
Marco Reisert1 and Valerij G. Kiselev1
1Medical Physics, University Medical Center Freiburg, Freiburg, Germany

Diffusion-Weighted MRI can reveal the microstructural organization of human brain white matter. In this work the diffusion model fitting is formulated as a global optimization problem assuming spatial coherence of the underlying diffusion parameters, which enables us to pool the variance from different voxels by their anatomical locations. The decision for single or multi-fiber voxels is directly integrated into the optimization process by using the Bayesian Information criterion. From a computational point of view the problem is quite hard, it is non-convex and combinatorial. At the heart of our approach lies a reversible jump Monte-Carlo Markov-Chain (RJMCMC) sampling strategy.

2621.   Bayesian Estimation of the Axonal Diffusion Coefficients in Brain White Matter
Enrico Kaden1, Frithjof Kruggel2, and Daniel C. Alexander1
1Centre for Medical Image Computing, University College London, London, United Kingdom, 2Department of Biomedical Engineering, University of California, Irvine, Irvine, CA, United States

Diffusion MR imaging has enabled us to study the geometry of white matter in the individual human brain noninvasively. The present work aims to quantify the voxel-averaged diffusion coefficients parallel to an axon and perpendicular to it without any prior knowledge about how the axons are oriented within a voxel because the fiber orientation distribution is typically not known in advance. The axonal water diffusivity reflects the fiber microanatomy such as the axon diameter, the myelination, and the interaxonal space.

2622.   What does non-exponential diffusion-weighted signal decay reveal about myocellular barriers?
John G Georgiadis1,2, Caroline G Tennyson1, Danchin D Chen1, Armen A Gharibans1, and Curtis L Johnson1,2
1Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, 2Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, United States

The successful employment of DTI to assess muscle quality in older adults in vivo hinges on connecting the signal to muscle cytoarchitecture. Seeking to explore the well-established anisotropy of the DTI metrics in muscle, the diffusion-weighted signal decay along the secondary and tertiary eigenvector tracts as a function of b-value was measured in the vastus medialis muscle of a single subject. We introduced a continuum myofiber model and attributed the non-exponential signal decay with b-value to the presence of myocellular diffusion barriers. This behavior cannot be accounted by lumped two-compartment models commonly considered in skeletal muscle DTI.

2623.   Non central chi estimation of multi-compartment models improves model selection by reducing overfitting
Aymeric Stamm1, Benoit Scherrer1, Stefano Baraldo2, Olivier Commowick3, and Simon Warfield1
1Computational Radiology Laboratory, Boston Children's Hospital, Boston, MA, United States, 2MOX, Politecnico di Milano, Milan, Italy, 3VISAGES, INRIA, Rennes, France, Metropolitan

Noise in diffusion MRI is known to be characterized by a non-central chi distribution. Many denoising methods have accounted for this but, for the estimation of diffusion models, the noise is most of the time still approximated by a Gaussian distribution. In this abstract, we examine the impact of this approximation to determine the optimal number of fascicles required for the estimation of multi-compartment models. We show that performing the models' estimation within a non-central chi framework significantly reduces over-fitting thus yielding a more reliable selection of the optimal number of fascicles.

2624.   Microstructural characterisation of normal and malignant human prostate tissue with VERDICT-MRI
Eleftheria Panagiotaki1, Rachel W Chan2, Nikolaos Dikaios2, Hashim U Ahmed3, David Atkinson2, Shonit Punwani2, David J Hawkes1, and Daniel C Alexander1
1Centre for Medical Image Computing, University College London, London, London, United Kingdom, 2Centre for Medical Imaging, University College London, London, United Kingdom, 3Research Department of Urology, Div of Surgery & Interventional Sci, University College London, London, United Kingdom

This study utilised diffusion-weighted MRI to probe in vivo the microstructure of benign and cancerous prostate tissue non-invasively. For this purpose, a mathematical model was employed to capture the Vascular, Extracellular and Restricted DIffusion for Cytometry in Tumours (VERDICT). We demonstrate the technique in patients with prostate cancer of Gleason score 7 (3+4) in the peripheral zone (all imaged before undergoing biopsy). Experiments using the VERDICT model identified a significant increase in vascular volume in the tumour regions. The standard apparent diffusion coefficient (ADC) and intravoxel incoherent motion (IVIM) models failed to detect any significant differences between benign and tumour areas.

2625.   In vivo characterisation of tumour microstructure with VERDICT MRI
Eleftheria Panagiotaki1, Simon Walker-Samuel2, Bernard Siow1,2, Peter S Johnson3, Vineeth Rajkumar3, R.Barbara Pedley3, Mark F Lythgoe2, and Daniel C Alexander1
1Centre for Medical Image Computing, University College London, London, London, United Kingdom, 2Centre for Advanced Biomedical Imaging, University College London, London, United Kingdom, 3UCL Cancer Institute, University College London, London, United Kingdom

This work presents a novel technique that quantifies and maps histological features of tumours, in vivo. The technique, named VERDICT (Vascular, Extracellular and Restricted DIffusion for Cytometry in Tumors), couples DW-MRI with a mathematical model of tumour tissue to access features such as cell size, vascular volume fraction, intra- and extracellular volume fractions, and pseudo-diffusivity associated with blood flow. We demonstrate the technique in two tumour xenograft models of colorectal cancer with contrasting cellular and vascular phenotypes. Experiments identified known differences in the microstructure of the tumours and a significant decrease in cell volume following administration of gemcitabine, possibly reflecting apoptotic volume decrease.

2626.   Learning microstructure parameters from diffusion-weighted MRI using random forests
Gemma Nedjati-Gilani1, Matt G Hall1, Claudia Angela M Wheeler-Kingshott2, and Daniel C Alexander1
1Computer Science & Centre for Medical Image Computing, University College London, London, London, United Kingdom, 2Department of Neuroinflammation, Institute of Neurology, UCL, London, United Kingdom

Deriving analytical models of the diffusion MR signal which account for permeability is inherently difficult and often requires strong assumptions to be made about the compartmentation of water within the tissue. Given these problems, in this study we construct a computational model using Monte Carlo simulations and machine learning. We use random forest regression to learn a mapping between simulations and microstructure parameters and obtain an efficient and accurate model for microstructure imaging that accounts for permeability. We show that unseen microstructure parameters are well-predicted by the random forest regressor for both noise-free and noisy data.

Hamed Y. Mesri1,2, Kelvin J. Layton1,3, Iven M. Y. Mareels1, and Leigh A. Johnston1,3
1Department of Electrical and Electronic Engineering, The University of Melbourne, Melbourne, Victoria, Australia, 2Victoria Research Laboratory, National ICT Australia, Melbourne, Victoria, Australia, 3Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria, Australia

Cramer Rao Lower Bound analysis is used to evaluate two compartment hindered/restricted diffusion models for estimation of mean axon diameter or axon diameter distributions from diffusion weighted MRI data. Our best-case model analysis demonstrates that the models are prone to high uncertainty levels. In practice, experimental data is acquired in regimes far from best-case model assumptions. Thus estimator performance is necessarily worse than the Cramer Rao error rates, which casts doubt on the ability of these models to robustly estimate microstructural features from diffusion MRI data. The Cramer Rao analysis technique is extensible to all parametric model-based inference methods.

2628.   Ranking Diffusion MRI Models for Fibre Dispersion using In Vivo Human Brain Data
Uran Ferizi1,2, Torben Schneider2, Eleftheria Panagiotaki1, Maira Tariq1, Hui Zhang1, Claudia A. M. Wheeler-Kingshott2, and Daniel C. Alexander1
1Department of Computer Science and Centre for Medical Image Computing, University College London, London, United Kingdom, 2NMR Research Unit, Department of Neuroinflammation, Queen Square MS Centre, UCL Institute of Neurology, London, United Kingdom

In this work we compare parametric diffusion MRI models which explicitly seek to explain fibre dispersion in nervous tissue. These models aim at providing more specific biomarkers of disease by disentangling these structural contributions to the signal. Some models are drawn from recent work in the field; others have been constructed from combinations of existing compartments that aim to capture both intracellular and extracellular diffusion. To test these models we use a rich dataset acquired in vivo on the corpus callosum of a human brain, and then compare the models via the Bayesian Information Criteria. We test this ranking via bootstrapping on the data sets, and cross-validate across unseen parts of the protocol. We find that models that capture fiber dispersion are preferred. The results show the importance of modelling dispersion, even in apparently coherent fibers.

2629.   Fast and robust detection of the optimal number of fascicles in diffusion images using model averaging theory
Aymeric Stamm1, Benoit Scherrer1, Olivier Commowick2, Christian Barillot3, and Simon Warfield1
1Computational Radiology Laboratory, Boston Children's Hospital, Boston, MA, United States, 2VISAGES, INRIA, Rennes, France, Metropolitan, 3VISAGES, CNRS, Rennes, France, Metropolitan

It is well known that the white matter has a complex architecture composed mainly of axon bundles or fascicles and glial cells. Fascicles cross in most parts of the white matter and multi-compartment models have been devised to study this complex microstructure. These models require that the number of compartments is known a priori, which is not the case in practice. In particular, determining the number of fascicles is difficult. It can however be reliably estimated from the generalization error at the cost of huge computational time. We propose a novel approach that relies on model averaging theory and generates the same results as the generalization error in a dramatically reduced computational time.

2630.   Comparing diffusion-weighted MRI signals from ordered and disordered microstructures
Damien J McHugh1,2, Penny L Hubbard1,2, Josephine H Naish1,2, and Geoffrey JM Parker1,2
1Centre for Imaging Sciences, University of Manchester, Manchester, United Kingdom, 2Biomedical Imaging Institute, University of Manchester, Manchester, United Kingdom

In this work we compare the diffusion-weighted MRI signals obtained from diffusion experiments in ordered and disordered microstructural environments. We used a simple tissue model of impermeable spherical cells and performed separate Monte Carlo diffusion simulations for ordered and disordered cell packing geometries. Synthetic signals were generated for pulse sequence parameters available on clinical scanners. Differences between the signals from ordered and disordered microstructures were small when extra-cellular diffusion alone was considered, and these differences were even smaller when considering combined intra- and extra-cellular diffusion. This suggests that the diffusion signal is insensitive to the packing geometry’s order/disorder for the sequence parameters and tissue properties covered here.

2631.   A novel biophysical model that characterizes the distribution of anisotropic micro-structural environments with DWI (DIAMOND)
Benoit Scherrer1, Maxime Taquet1, Mustafa Sahin2, Sanjay P. Prabhu1, and Simon K. Warfield1
1Radiology, Harvard Medical School, Boston Children's Hospital, Boston, MA, United States, 2Neurology, Harvard Medical School, Boston Children's Hospital, Boston, MA, United States

We propose a novel biophysical model of the diffusion that characterizes the distribution of three-dimensional (3D) microstructural environments in each voxel. This enables characterization of each fascicle in each voxel and of isotropic diffusion and may lead to novel biomarkers and novel investigations of the white-matter microstructure.

2632.   Inferring Axon Diameter Sizes using Monte Carlo Simulations and Oscillating Gradient Spin Echo Sequences
Sheryl L Herrera1, Trevor J Vincent2,3, Morgan E Mercredi1, Richard Buist4, Christopher P Bidinosti1,2, and Melanie Martin2,5
1Physics & Astronomy, University of Manitoba, Winnipeg, Manitoba, Canada, 2Physics, University of Winnipeg, Manitoba, Canada, 3Astronomy & Astrophysics, University of Toronto, Ontario, Canada, 4Radiology, University of Manitoba, Manitoba, Canada, 5Physics & Astronomy, Radiology, University of Manitoba, Manitoba, Canada

We simulate cylindrical geometries using OGSE and AxCaliber to determine diameter distributions. The fit results agree reasonably with the geometry. Numbers of small axons are underestimated and larger axons are overestimated. The calculated mean radius (1.57plus-or-minus sign0.01µm) is comparable with the actual mean radius (1.67µm). The CHARMED model simulates the extracellular space as hindered, whereas ours was restricted. Because the CHARMED model signal is proportional to r2, the larger axons are overestimated. With noise the smaller axons are harder to identify. These reasons could account for some discrepancy between the fitted and actual data. Modifications are necessary to the CHARMED model.

2633.   Oscillating Gradient Diffusion MRI in the ex-vivo prostate to assess ADC behavior at small diffusion times
Andre Bongers1, Aritrick Chatterjee2, Geoffrey Watson3, and Roger Bourne4
1Mark Wainwright Analytical Centre, University of New South Wales, Sydney, NSW, Australia, 2University of Sydney, Sydeny, NSW, Australia, 3Royal Prince Alfred Hospital, Sydney, NSW, Australia, 4University of Sydney, Sydney, NSW, Australia

As DWI is able to sensitively sample cellular changes in tissues the method is a promising biomarker for prostate cancer detection. Standard PGSE methods usually sample ADCs in the long diffusion time regime, meaning that ADC quantification is affected by cellular restrictions from multiple scales. This study explores the ability of oscillating gradient DWI (OGSE) methods to detect subcellular changes in fixed and unfixed ex-vivo prostate tissue at high magnetic field. Our findings show that -in the short diffusion time regime- ADC-diffusion-time behavior depends significantly on prostate tissue type and suggest that that prostate cancer induces intracellular structure changes.

2634.   In vivo oscillating gradient diffusion MRI provides unique microstructural information in normal and hypoxic-ischemic injured mouse brains
Dan Wu1, Frances J Northington2, and Jiangyang Zhang3
1Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States, 2Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States, 3Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States

In this study, we showed that in vivo oscillating gradient spin echo (OGSE) diffusion MRI provided unique tissue contrasts to delineate structures in the adult mouse cerebellum. Comparisons between in vivo and ex vivo OGSE data showed that death and fixation significantly reduced OGSE ADC measurements and altered their frequency dependency. In neonatal mouse brains with hypoxic-ischemic injury, in vivo OGSE showed larger increase in ADC with frequency in regions with cytotoxic edema than normal tissues, and thereby reduced edema contrast at high oscillating frequencies, which suggested that the microstructural changes under cytotoxic edema were within certain spatial scales.

2635.   Evidence for the Detection of Microscopic Diffusion Anisotropy in Human Brain Gray Matter in Vivo
Marco Lawrenz1,2 and Juergen Finsterbusch1,2
1Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Hamburg, Germany, 2University Medical Centers Hamburg-Kiel-Luebeck, Neuroimage Nord, Hamburg-Kiel-Luebeck, Hamburg-Kiel-Luebeck, Germany

Double-wave-vector diffusion-weighting (DWV) experiments involving two successively applied diffusion weightings are able to detect diffusion anisotropy on a microscopic scale, even if the diffusion macroscopically appears isotropic. This has been demonstrated recently in a human brain white matter region that yields a fractional anisotropy of 0. In this study, human gray matter is targeted in vivo using a DWV sequence with inversion recovery to suppress WM signals and avoid partial volumen effects. While no signal modulation is observed in a fluid phantom, the modulation curve characteristic for diffusion anisotropy is observed although the modulation amplitude is reduced compared to WM.

2636.   Exchange and T2-relaxation effects in double pulsed field gradient experiments
Casper Kaae Sønderby1, Henrik Lundell1, and Tim B. Dyrby1
1Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital, Hvidovre, Denmark

Double Pulsed Field Gradient sequences have recently been used to detect novel tissue contrasts such as the Apparent Exchange Rate and Compartment Eccentricity. We compare the effects of compartmental specific T2-relaxation in both single and double pulsed field gradient sequences. We measure a decrease in the Apparent Diffusion Coefficient as either the mixing time or the echo time is increased indicating filtering of compartment specific signal components with fast diffusivities. Our results indicate that both single and double pulsed field gradient sequences should adopt for the same TE in all experiments to maintain the relative T2-relaxation weighting of the individual compartments.

2637.   The effect of diffusion in the extracellular space on double-PFG measurements of axon size: Insights from Monte-Carlo simulations
Gregory T Baxter1, Vitaly Galinsky1, Evren Ozarslan2, Peter J Basser3, and Lawrence R Frank1,4
1Center for Scientific Computation in Imaging, Dept. of Radiology, University of California, San Diego, CA, United States, 2Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States, 3Section on Tissue Biophysics and Biomimetics, PPITS, NICHD, National Institutes of Health, Bethesda, MD, United States, 4Center for Functional MRI, Dept of Radiology, University of California, San Diego, CA, United States

We present Monte-Carlo simulations of diffusion within hexagonally packed arrays of cylinders mimicking the white-matter, and report the signal behavior for double-PFG experiments with zero mixing times. We investigate the accuracy of the axonal diameter estimates when a bi-compartmental model that assumes Gaussian diffusion outside the cells is employed. Despite the substantially underestimated bulk diffusivity values, cell diameter and volume fraction estimates are both adequately captured by such a bi-compartmental model. Some underestimation of cell diameters is expected only for tightly packed configurations.

2638.   Reproducibility and Normal Values of Microscopic Diffusion Anisotropy Measures and Their Variation in Healthy Volunteers
Marco Lawrenz1,2 and Juergen Finsterbusch1,2
1Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Hamburg, Germany, 2Neuroimage Nord, University Medical Centers Hamburg-Kiel-Luebeck, Hamburg-Kiel-Luebeck, Hamburg-Kiel-Luebeck, Germany

Double-wave-vector diffusion-weighting (DWV) experiments with two weighting periods applied successively offer access to microscopic tissue properties, e.g. the diffusion anisotropy present on a microscopic scale. This anisotropy is independent of the axon orientation distribution and, thus, may better reflect axon integrity than measures derived from DTI. To investigate whether measures of th microscopic diffusion anisotropy, e.g. the so-called MA index, are feasible for application in clinical or neuroscientific research, normal values in white matter and their variation within a group of healthy volunteers as well as their reproducability within and between sessions are determined.

2639.   Apparent exchange rate (AXR) mapping in diffusion MRI: An in vivo test-retest study and analysis of statistical power.
Björn Lampinen1, Filip Szczepankiewicz1, Danielle van Westen2, Pia Sundgren2, Freddy Ståhlberg1,2, Jimmy Lätt3, and Markus Nilsson4
1Dpt. of Medical Radiation Physics, Lund University, Lund, Sweden, 2Dpt. of Diagnostic Radiology, Lund University, Lund, Sweden, 3Center for Medical Imaging and Physiology, Lund University Hospital, Lund, Sweden, 4Lund University Bioimaging Center, Lund University, Lund, Sweden

Water exchange can be mapped noninvasively in diffusion MRI using filter-exchange imaging (FEXI) to obtain the apparent exchange rate (AXR). We here aim to prepare FEXI for future clinical research that investigates differences in mean AXR across populations. A test-retest study is conducted on 18 healthy volunteers to assess how inter-subject differences and measurement error contribute to variance in AXR in various brain regions. A power analysis is then performed to interpret AXR variance in terms of study group sizes required to detect a range of differences while ensuring a statistical power of 0.8. We show that with study groups under 10 subjects, mean differences between populations of 40-80% in AXR, depending on the region, can be detected.

2640.   Apparent Indices in the Rat Brain by Angular Double-Pulsed-Field-Gradient MRI at Finite Mixing Time Collected With Different Experimental Conditions
Debbie Anaby1, Darya Morozov1, and Yoram Cohen1,2
1School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Science, Tel-Aviv University, Tel-Aviv, Ramat-Aviv, Israel, 2Sagol School of Neurosciences, Tel-Aviv University, Ramat-Aviv, Israel

Angular double-pulsed-field gradient (d-PFG) MRI has been suggested as an alternative for studying microstructure in the brain. It has been shown that angular d-PFG MR experiments performed with long tms are able to distinguish between compartments with different eccentricities. Here, we study the effects of different experimental parameters on the obtained apparent eccentricity (aE) and residual phase maps of an ex-vivo rat brain obtained from angular d-PFG MRI collected with finite tms.

2641.   Recipes of Diffusion Measurements with Oscillating Gradients
Valerij G. Kiselev1 and Bibek Dhital1,2
1Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany, 2German Cancer Consortium (DKTK), Heidelberg, Germany

We discuss two major challenges of diffusion measurements with oscillating gradients: (i) achieving the highest frequency on preclinical scanners and (ii) performing measurements on human scanners. In order to respond to (i), we propose a ramp that does not compromise the maximal achievable frequency below the hardware limits and show explicitly the parameter range for which this extension is crucial. Other important ingredients of diffusion measurements with oscillating gradient are the relative phase of two gradient trains in the spin echo measurements, fast ramps for low-frequency measurements in human scanners and the optimal total gradient duration.

2642.   Preliminary Results on Measuring Intravoxel Incoherent Motion Using Oscillating Diffusion Gradients
Andreas Wetscherek1, Bram Stieltjes2, and Frederik Bernd Laun1,2
1Medical Physics in Radiology (E020), DKFZ, Heidelberg, Germany, 2Quantitative Imaging Based Disease Characterization (E011), DKFZ, Heidelberg, Germany

Diffusion experiments using oscillating gradients are performed. In the pancreas of healthy volunteers, sine gradients were found to cause larger signal attenuation than cosine gradients of the same b-value. In addition, the signal attenuation was found to decrease for the cosine profile when the number of oscillations was increased. The experimental findings can be understood in the picture of temporal diffusion spectroscopy and in the intravoxel incoherent motion model. The method might be of particular interest for probing the microvasculature in organs in which the characteristic timescale ô of the incoherent motion is shorter than the echo time.

2643.   Monte-Carlo simulation of diffusion MRI with realistic voxel sizes
Matt G Hall1, Gemma Nedjati-Gilani1, and Daniel C Alexander1
1Centre for Medical Image Computing, University College London, London, United Kingdom

We present a new method that enables Monte Carlo simulation of diffusing spins for diffusion MR data synthesis to be performed using tissue regions with sizes comparable to a typical scan voxel. We show how the technique may be optimised such that run time is minimised and also show that the new technique leads to improved reproducibility in synthetic diffusion-weighted measurements.


Diffusion-Weighted Imaging Phantoms & Validation

Wednesday 14 May 2014
Traditional Poster Hall  16:00 - 18:00

2644.   Reliability and sensitivity of intravoxel incoherent motion (IVIM) MRI in measuring cerebral perfusion
Wen-Chau Wu1,2, Kuan-Lin Chen3, and Shu-Hua Lien3
1Graduate Institute of Oncology, National Taiwan University, Taipei, Taiwan, 2Graduate Institute of Clinical Medicine, National Taiwan University, Taipei, Taiwan, 3Medcial Imaging, National Taiwan University Hospital, Taipei, Taiwan

Intravoxel incoherent motion (IVIM) MRI is a technique proposed for concurrent measurement of water diffusion coefficient D and perfusion-related pseudo-diffusion coefficient D*. In this study, we investigated the sensitivity of IVIM MRI in the brain by comparing with arterial spin-labeling (ASL) MRI. Monte Carlo simulation was performed to assess the reliability of the perfusion indexes derived from nonlinear fitting. Results show that IVIM perfusion indexes are less reliable when D*/D < 10 and vascular volume fraction f < 0.05. Overall, f is more robust an index than D*. ASL-derived blood flow values were found mildly correlated with fD* and f.

2645.   Regional change in DTI parameters due to scanner upgrade: effects on TBSS and ROI analysis
Petra Pouwels1, Frederik Barkhof2, Rudolf Verdaasdonk1, and Joost Kuijer1
1Physics & Medical Technology, VU University Medical Center, Amsterdam, Netherlands, 2Radiology and Nuclear Medicine, VU University Medical Center, Amsterdam, Netherlands

Regional changes in DTI parameters were observed in healthy volunteers at 3T after a hardware upgrade. Pairwise comparison (mimicking longitudinal studies) showed significant FA differences in 26.7% of the WM skeleton, and in all diffusivities, especially in the body of the corpus callosum. Unpaired comparison (mimicking cross-sectional studies) still showed FA differences in 5.5% of the skeleton. A change in gradient system and related eddy-current behaviour might be the cause of the observations. No pairwise differences were observed in repeated measurements on the same scanner. These results emphasize the need to take scanner upgrade into account in the study design.

2646.   Quality Assurance for Diffusion Tensor Imaging Using ACR Phantom: Comparative Analysis with 6, 15 and 32 Directions at 1.5T and 3.0T MRI Systems
Jung-Hoon Lee1,2, Sang-Young Kim1, Do-Wan Lee1, Jin-Young Jung1, Kyu-Ho Song1, and Bo-Young Choe1
1Department of Biomedical Engineering, Research Institute of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul, Seoul, Korea, 2Department of Radiology, Kyunghee Medical Center, Seoul, Seoul, Korea

We evaluated geometric accuracy, slice position accuracy, image intensity uniformity, percent-signal ghosting and, low-contrast object detectability provided by ACR Guidance as well as image distortion, ADC and FA values measured with 6, 15, and 32 directions at 1.5T and 3.0T MR systems.

2647.   Thalamic segmentation and validation with diffusion-weighted MRI
Francesca Pizzorni-Ferrarese1 and Franco Pestilli2
1Department of Psychology, The Royal Holloway, University of London, Egham, Surrey, United Kingdom, 2Psychology, Stanford University, Stanford, CA, United States

We propose a method to segments the human thalamus automatically using diffusion MR signal and to validate the accuracy of a alternative thalamic segmentations in individual brains. The method treats the clusters in the segmentation as models of the white matter tissue. Thalamic nuclei are assumed to have homogeneous tissue properties. Under this assumption the mean diffusion signal within each nucleus is used as prediction of the segmentation model. We use the model to validate a family of candidate thalamic segmentations by looking at how the reliability of the model prediction compares to the reliability of the measured diffusion data.

2648.   Quantitative evaluation of biophysical models of the diffusion with in vivo data by assessment of the generalization error
Benoit Scherrer1, Maxime Taquet1, Mustafa Sahin2, Sanjay P Prabhu1, and Simon K. Warfield1
1Radiology, Harvard Medical School, Boston Children's Hospital, Boston, MA, United States, 2Neurology, Harvard Medical School, Boston Children's Hospital, Boston, MA, United States

We propose a novel framework to achieve quantitative evaluation of biophysical models of the diffusion with in-vivo data. It enables identification of the model that best predicts the diffusion signal, and therefore identification of the model that best captures the underlying biophysical mechanisms. We investigate the performance of DTI, NODDI and DIAMOND.

2649.   Do DTI reproducibility studies agree? A meta-analysis.
Pim Pullens1, Wim van Hecke2, and Paul M Parizel1
1Radiology, Antwerp University Hospital, Edegem, Antwerp, Belgium, 2Icometrix, Leuven, Belgium

There is more and more interest in testing reproducibility of DTI measures, which could lead to use of DTI measures as clinical biomarkers. Coefficient of variation (std/mean) is often used to assess reproducibility. However, it is not trivial to compare CVs from different studies, each with a different number of subjects. In this meta-analysis across DTI reproducibility studies, we test if CVs are equal among published FA reproducibility studies with an appropriate statistical test. Results show that although confidence intervals of FA show deviations because of analysis or scanner type, CVs are comparable.

2650.   Predicting the Quantitative Accuracy of In-Vivo ADC using an Ice-Water Phantom
David M. Morris1, Hossein Ragheb1, Neil Thacker1, Naomi H.M. Douglas2, and Alan Jackson3
1Centre for Imaging Sciences, University of Manchester, Manchester, United Kingdom, 2Institute of Cancer Research, Sutton, United Kingdom, 3Wolfson Molecular Imaging Centre, University of Manchester, Manchester, United Kingdom

Apparent diffusion Coefficient (ADC) is a biomarker shown to have efficacy in monitoring the response of tumors to interventions. To be used successfully in multi-center trials a quality assurance protocol must be developed using an ice water phantom. The results of a multi-vendor, multi-site trial using standardized protocols are presented where different measurements of the accuracy of the systems using the phantom are compared. Then the relationship of these with the variability observed within the normal liver of volunteers at each site. While the protocols can differentiate between scanners there is no predictive power for performance in-vivo.

2651.   Repeatability of Diffusion-Weighted MRI Parameters in a Paediatric Oncology Population
Neil P Jerome1, Keiko Miyazaki1, David J Collins1, Matthew R Orton1, James d'Arcy1, Lucas Moreno2, Andrew D J Pearson2, Lynley V Marshall2, Fernando Carcellar2, Martin O Leach1, Stergios Zacharoulis2, and Dow-Mu Koh3
1CR-UK and EPSRC Cancer Imaging Centre, The Institute of Cancer Research, Sutton, Surrey, United Kingdom, 2Paediatric Drug Development Team, Cancer Therapeutics and Clinical Studies, The Institute of Cancer Research, Sutton, Surrey, United Kingdom, 3Department of Radiology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom

Diffusion-weighted imaging provides a sensitive way of detecting functional changes that may precede changes in tumour size and in response to cytostatic effects; though widely used for functional imaging in adult clinical trials, there is a need to establish the repeatability of DWI-derived parameters in children. For a paediatric cohort (median age 11, range 6 – 15 years) of seven extra- and eight intra-cranial solid tumours, DWI was performed on two successive days, showing lowest CV values for ADC with varying b-value inclusion (CV 2.4 – 4.1%), and for D derived from IVIM (CV 2.5%. IVIM perfusion-related parameters were less repeatable (CV>25%).

2652.   Initial Performance of the Diffusive Quantitative Imaging Phantom (DQIP): Thermal and SNR Characteristics Using a Clinical Protocol
Marc Buzzelli1, XiaoTian Li2, William Randazzo1, and Nathan Yanasak1
1Department of Radiology and Imaging, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States, 2Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States

Problem To characterize and apply thermal and signal-to-noise corrections to DTI images of a specialized quality assurance phantom via regression, to facilitate future investigation of systematic biases in clinical protocols. Methods A phantom was constructed for diffusion imaging. Scans were obtained utilizing a 3T magnet, monitoring the temperature of the phantom during the scans. FA and ADC maps were calculated. Dependencies in temperature and SNR were determined, to examine baseline systematic variability after regression. Results/Conclusion FA and ADC show linear dependence on temperature and an inverse dependence on SNR. Intrinsic dependences of FA on SNR are significant after regression.

2653.   A crossing fibre phantom for diffusion MRI composed of co-electrospun fibres
Penny L Hubbard1, Feng-lei Zhou2, Stephen Eichhorn3, and Geoff JM Parker2
1The University of Manchester, Manchester, Greater Manchester, United Kingdom, 2The University of Manchester, Manchester, United Kingdom, 3University of Exeter, Exeter, United Kingdom

We present a proof-of-principle study of comparing an aligned and simple crossing fibre phantoms composed on co-electrospun hollow fibres, with an inner diameter within the biological range.

2654.   Segmentation of anterior thalamic nucleus in DTI study: comparison of CSD-based method and conventional DT model
Yi-Hsiu Hsiao1, Cheng-Yu Chen1,2, Ping-Huei Tsai1, Hsiao-Wen Chung3, Ming-Chung Chou4, Shih-Wei Chiang3,5, Yung-Chieh Chen6, and Hung-Wen Kao5
1Department of Medical Imaging and Imaging Research Center, Taipei Medical University Hospital, Taipei Medical University, Taipei, Taiwan, 2Graduate Institue of Clinical Medicine, Taipei Medical University, Taipei, Taiwan, 3Graduate Institute of Biomedical Electrics and Bioinformatics, National Taiwan University, Taipei, Taiwan, 4Department of Medical Imaging and Radiological Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan, 5Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan,6Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan

The anterior thalamic nucleus (AN) plays an important role in communication and the actual mechanism has not been well-known. A reliable non-invasive imaging method which is capable of delineating the nucleus is desired. Several studies have demonstrated that MR diffusion tensor imaging (DTI) could help identify the individual regions of the thalamic nuclei by fiber tracking method, but the results may not actually reflect the true anatomic location. A reasonable solution has recently been proposed using constrained spherical deconvolution (CSD) tractography technique. In this study, we compared CSD-based method with conventional diffusion tensor (DT) model in localization of the AN and the fractional anisotropy.

2655.   Calibrated Diffusion Phantom for 7T MRI
Joelle E Sarlls1, Carlo Pierpaoli2, Qi Duan3, Wolfgang Devine4, and Hellmut Merkle3
1NINDS/NMRF, National Institutes of Health, Bethesda, MD, United States, 2NICHD/STBB, National Institutes of Health, MD, United States, 3NINDS/LFMI, National Institutes of Health, MD, United States, 4NINDS-NIMH/RSB, National Institutes of Health, Bethesda, MD, United States

Although 7T provides increased MR signal, attractive to signal-starved diffusion imaging, there are also technical challenges like increase B1 inhomogeneity and susceptibility effects. Accordingly, there is much activity in sequence and hardware development. We introduce a calibrated diffusion phantom that provides the means to accurately test developed sequences and hardware at 7T. We utilized a 35% PVP solution providing a known diffusion coefficient, close to in-vivo brain, and mitigating flow effects. We show that utilizing a 17cm cylindrical shaped container fitted with a grid of 1x1cm plastic columns dramatically improves B1 homogeneity, removing bias in the calculated diffusion coefficient.

2656.   Evaluation of the Effect of Intra-voxel Contrast Agent Diffusion on Quantitative DCE-MRI
Stephanie L. Barnes1,2, Natenael B. Semmineh1,3, C. Chad Quarles1,2, and Thomas E. Yankeelov1,2
1Vanderbilt University Institute of Imaging Sciences, Vanderbilt University, Nashville, TN, United States, 2Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, United States, 3Physics and Astronomy, Vanderbilt University, Nashville, TN, United States

Standard evaluation of dynamic contrast enhanced MRI (DCE-MRI) data assumes instantaneous mixing of the contrast agent (CA) within a given voxel. This work aims to evaluate the effect of non-instantaneous mixing due to passive diffusion of the CA on quantitative DCE-MRI. We utilized a finite element model of a (250 µm2) voxel that divides the voxel into vascular, extravascular extracellular, and extravascular intracellular spaces. The results show that diffusion, plasma fraction, and temporal resolution have a substantial effect on the distribution of CA concentration and this can significantly affect the estimation of pharmacokinetic parameters.

2657.   Quality Assurance for Multi-Center DTI Trial at 3T
Xiaopeng Zhou1, Ken Sakaie1, Erik Beall1, Mark Lowe1, and Robert Fox2
1Imaging Institute, Cleveland Clinic, Cleveland, OH, United States, 2Neurological Institute, Cleveland Clinic, Cleveland, OH, United States

We describe the development of a practical quality assurance (QA) protocol for a multi-center diffusion tensor imaging trial. fBIRN phantom was scanned on two 3T scanners to evaluate temporal stability of SNR and DTI parameters. Robustness of QA metrics against positioning provides confidence that the protocol will be effective across sites. Although variation of tensor parameters is small, it does correlate with SNR, suggesting that QA measurements may serve as a valuable covariate for statistical analysis. Tensor parameters appear consistent across platforms. This DTI QA procedure is effective to track scanner performance and can provide reference for multi-center trial.

2658.   Diffusion gradient calibration in DSI using a cyclooctane phantom
Irvin Teh1, Maelene Lohezic1, Dunja Aksentijevic1,2, and Jurgen E Schneider1
1Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom, 2Cardiovascular Division, The Rayne Institute, King's College London, London, United Kingdom

Gradient calibration is critical to accurate sampling of q-space in diffusion MRI, particularly for applications such as diffusion spectrum imaging (DSI) that rely on a precise relationship of q-space sampling. Cyclooctane possesses a number of properties that make it suitable for gradient calibration at high b-values, including isotropic diffusion, relatively low diffusivity and high viscosity, and a single proton resonance. We present the novel use of a phantom intended for gradient calibration in DSI and other high b-value q-space imaging applications.

2659.   Progression of Whole Mouse Brain Formaldehyde Fixation by T2 and ADC Maps
Tiziana M Florio1, Giuseppina Confalone1, Loredana Cristiano1, Alessia Fidoamore1, Angelo Galante1,2, Laura Brandolini3, Marcello Allegretti3, Annamaria Cimini1, and Marcello Alecci1,2
1Dipartimento Medicina Clinica, Sanita’ Pubblica, Scienze della Vita e dell'Ambiente, University of L'Aquila, L'Aquila, Italy, 2Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Gran Sasso, Italy, 3Research Centre, Dompé s.p.a., L'Aquila, Italy

We have investigated the time course from sacrifice of ADC and T2 maps of whole mouse brain during fixation with formaldehyde, comparing the immersion and perfusion methods. A non-fixed whole brain was studied for comparison.

2660.   Age Related Changes in Diffusion Tensor Indices in the Medial and Lateral Gastrocnemius.
Usha Sinha1, Robert Csapo2, Vadim Malis1, Yanjie Xue1, and Shantanu Sinha2
1Physics, SDSU, San Diego, CA, United States, 2Radiology, UCSD, San Diego, CA, United States

Age related changes in muscle alter both fiber architecture (flengths and pennation angles) as well the microstructure (fiber type, diameter, fibrosis). Diffusion tensor imaging allows the mapping of fiber architecture as well as the microstructure. We report age related changes in diffusion tensor indices (eigenvalues and FA) of the medial and lateral gastrocnemius in a cohort of 5 young and 5 old women. All three eigenvalues for both muscles increase with age, significant difference in young and old was seen for nearly all the indices. A decreased fiber diameter and muscle fiber fraction may qualitatively explain the current findings.

2661.   Anisotropy, Compartmentalization, and Anomalous Diffusion of Intracellular Metabolites in the Axons and Glia of the Human Brain at 7T
Carson Ingo1, Itamar Ronen1, and Andrew G. Webb1
1C. J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands

Recently, there was the first report of anomalous diffusion in DWS measurements of intracellular metabolites in the rat brain at 7T utilizing ultra-short diffusion times afforded by oscillating gradients. Here, we consider in vivo measurements of anomalous diffusion for tNAA, tCho, and tCr in the human brain at 7T with conventional diffusion times. Our study suggests for metabolites: 1) white matter anisotropy does not contribute to Gaussian or anomalous diffusion patterns, 2) compartmental distribution does not necessarily contribute to anomalous diffusion, and 3) the unique sub-diffusive behavior of tCr may be influenced by other factors like chemical exchange.


Tractography Connectivity

Wednesday 14 May 2014
Traditional Poster Hall  16:00 - 18:00

2662.   The reproducibility of diffusion tensor imaging on brain connectivity measures between cortical regions using probabilistic tractography
Chun-Hao Huang1, Woan-Chyi Wang2, Yi-Ru Lin1, and Shang-Yueh Tsai2
1Electronic and Computer Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, 2Graduate Institute of Applied Physics, National Chengchi University, Taipei, Taiwan

In this study we investigate the reproducibility of DTI and probabilistic tractography on the brain connectivity measures among 78 grey matter parcellations. Regular DTI protocols (30 directions, b=1000) were performed twice on each 14 healthy subject (7 male and 7 female in 20 to 25 years old). Results show that probabilistic tractography can be successfully applied to calculate the connectivity between GM regions. The inter-scan reproducibility is at level of 10% for GM regions with connectivity strength over 0.2. Therefore, structural connectivity assessed by diffusion tensor tractogrphy can be used to study the brain network.

2663.   Functionally constrained tractography: Improved diffusion MRI-based fiber tractography using functional information
Xi Wu1,2, Xu Ran2, Adam Anderson2, and Zhaohua Ding2
1Huaxi MRI Research center, Sichuan University, chengdu, sichuan, China, 2Vanderbilt University Institute of Imaging Science, Vanderbilt University, nashville, TENNESSEE, United States

We proposed an improved diffusion MRI-based fiber tractography using functional information. Bold signals are modeled as spatio-temporal correlation tensor and than used to constrain the tractography. This Constrained tracking method can ensure more accurate tracking direction estimation thus benefit more rigid tracking results.

2664.   A DTI tractography algorithm derived from the diffusion equation and quantum-mechanical correspondence: Method and Simulation
Hong-Hsi Lee1, Jeng-Wei Chen1, and Wen-Yih Isaac Tseng2
1Physics, National Taiwan University, Taipei, Taiwan, Taiwan, 2Center for Optoelectronic Medicine, National Taiwan University, Taipei, Taiwan, Taiwan

Utilizing the correspondence between diffusion equation and Schrodinger equation, we derived a Lagrangian and acquired an equation of motion. This equation is the core of our tractography algorithm which can be applied in the Diffusion Tensor Imaging (DTI) data. Since it contains gradient terms related to diffusion tensors, acute turnings of tracts are possible in several voxels. To demonstrate the feasibility, we simulated two-dimensional diffusion tensors from a picture of magnetic lines, and applied this algorithm to delineate tracts in the original picture. The simulation results show that this algorithm is viable.

2665.   Structural Brain Network Augmentation via Kirchhoff’s Laws
Iman Aganj1, Gautam Prasad2, Priti Srinivasan1, Anastasia Yendiki1, Paul M. Thompson2,3, and Bruce Fischl1,4
1Martinos Center for Biomedical Imaging, Radiology Department, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, 2Imaging Genetics Center, Institute for Neuroimaging and Informatics, University of Southern California, Los Angeles, CA, United States, 3Depts. of Neurology, Psychiatry, Engineering, Radiology and Ophthalmology, University of Southern California, Los Angeles, CA, United States, 4Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA, United States

-Structural brain connectivity – computed from diffusion-weighted MRI tractography – is useful in studying brain structure in health and disease. Current approaches for computing the structural brain network consider fiber bundles directly connecting brain regions, often disregarding indirect pathways relayed through other regions. Here we take multi-synaptic connections into account using mathematical tools developed for the analysis of resistive electrical circuits. Our results show that such an augmented network can improve the classification of Alzheimer’s disease patients from healthy controls.

2666.   Phantomas: a flexible software library to simulate diffusion MR phantoms
Emmanuel Caruyer1, Alessandro Daducci2, Maxime Descoteaux3, Jean-Christophe Houde3, Jean-Philippe Thiran2, and Ragini Verma1
1Section of Biomedical Image Analysis, Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States, 2Signal Processing Laboratory 5, École Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland, 3Sherbrooke Connectivity Imaging Lab, Université de Sherbrooke, Sherbrooke, Québec, Canada

We introduce Phantomas, an open-source software library to create realistic phantoms in structural and diffusion MRI. The software allows evaluation of each step of a tractography processing pipeline: acquisition design, preprocessing, local reconstruction and tractography algorithm. By starting from a ground truth configuration of fiber bundle geometries, Phantomas provides a basis to quantitatively evaluate connectivity analyses, using metrics based on successful reconstruction of the true connectivity profile. Complementarily, local metrics can be computed to measure the accuracy of local reconstruction methods. We demonstrate that user can easily create crossing, kissing and bending fiber configurations, leading to complex intravoxel diffusion profiles.

2667.   Lateralization of Temporal Lobe Epilepsy using Intrinsic Property of Water Diffusion in Fornix Crus
Mohammad-Reza Nazem-Zadeh1, Jason Schwalb2, Hassan Bagher-Ebadian3, Fariborz Mahmoudi1, Mohammad-Parsa Hosseini4, Hajar Hamidian1, Abdelrahman Hassane1, Oltion Meci1, Harrini Vijay1, Mohammad Emari1, and Hamid Soltanian-Zadeh1
1Radiology and Research Administration Departments, Henry Ford Hospital, Detroit, MI, United States, 2Neurosurgery Department, Henry Ford Hospital, Detroit, MI, United States, 3Neurology Department, Henry Ford Hospital, Detroit, MI, United States, 4Radiology and Research Administration Departments, Henry Ford Hospital, MI, United States

We hypothesizes that the hemispheric asymmetry of FA within the crura of fornix could be used to confirm the laterality of mesial temporal epileptogenicity. The TLE was associated with a reduced FA value in the fornix crus ipsilateral to the seizure onset. Outperforming anatomy-based lateralization methods, the proposed diffusion based method hold promise for improving decision-making for surgical resection and may reduce the need for implantation of intracranial monitoring electrodes.

2668.   A semi-local tractography approach using neighborhood information
Helen Schomburg1, Thorsten Hohage1, and Christoph Rügge1
1Institute for Numerical and Applied Mathematics, University of Göttingen, Göttingen, Germany

We present an approach for semi-local fiber tractography on HARDI data extending local tractography by including diffusion information of neighboring regions to reduce accumulation of noise. Considering the neighborhood located behind the current path position we obtain a guiding direction from the previously tracked path. Then, the region in front is explored by determining a set of candidate directions. In addition, we take into account right and left neighbors to observe the position on the fiber bundle perpendicular to the stepping direction and shift the fiber path point toward the center if necessary. Tests are performed on diffusion phantom data.

2669.   Lateralisation of the connections between Broca's area and the pre-SMA in relation to handedness
Henrietta Howells1, Flavio Dell'Acqua2,3, Anoushka Leslie2, Michel Thiebaut de Schotten1,4, Mitul Mehta2, Declan G. Murphy1, Andrew Simmons2, and Marco Catani1
1Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, London, United Kingdom, 2Department of Neuroimaging, Institute of Psychiatry, London, United Kingdom,3NIHR Biomedical Research Centre for Mental Health at SLAM NHS Foundation Trust, Institute of Psychiatry, London, United Kingdom, 4Université Pierre et Marie Curie-Paris 6, Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, Paris, France

The frontal aslant tract (FAT) is a newly described pathway connecting posterior Broca's territory with the pre-SMA and cingulate cortex. This tract is significantly left-lateralised in right-handed subjects and plays a role in speech initiation. It has not yet been studied in left-handers. We used spherical deconvolution diffusion tractography to compare this tract in right and left-handed subjects, finding left-lateralisation was not significant in the left-handed group. This may be reflective of more heterogeneous patterns of functional activation for language in left-handed individuals.

2670.   Mapping hippocampal connectivity of the live mouse brain with localized high resolution HARDI
Dan Wu1, Jiadi Xu2, Susumu Mori2,3, and Jiangyang Zhang3
1Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States, 2F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, United States, 3Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States

In order to resolve the complex microstructures and neural connectivity in the gray matter structures, high spatial and angular resolution is critical but remains challenging in vivo. We have achieved high-resolution HARDI (0.1 mm isotropic, 60 directions) of live the mouse brain using localized imaging technique and a 3D fast imaging sequence. Several potential tracts within the mouse hippocampus were reconstructed, and single subject and group average tractography data showed the tracts originated from the CA1 and dentate gyrus agreed with existing tracer-based studies. The technique could potentially be used to non-invasively examine the neuronal pathways in gray matter structures.

2671.   The role of fronto-parietal networks in mental imagery
Henrietta Howells1, Marco Catani1, Flavio Dell'Acqua2,3, Anoushka Leslie2, Andrew Simmons2, Declan G. Murphy1, and Michel Thiebaut de Schotten1
1Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, London, United Kingdom, 2Department of Neuroimaging, Institute of Psychiatry, London, United Kingdom,3NIHR Biomedical Research Centre for Mental Health at SLAM NHS Foundation Trust, Institute of Psychiatry, London, United Kingdom

When comparing two identical objects oriented differently, subjects perform a mental rotation of one object until it is congruent with the other. A recent diffusion tractography study revealed a correlation between right-lateralisation of a fronto-parietal pathway, the second branch of the superior longitudinal fasciculus (SLF II), and performance in certain visuo-spatial tasks. It is unknown whether this pathway is also involved in mental rotation. Using spherical deconvolution tractography, we assessed this correlation in a group of 25 healthy subjects. Our results confirmed lateralisation of this tract is associated with mental rotation performance.

2672.   Structural Graph Analysis of Left and Right Temporal Lobe Epilepsy using Diffusion Spectrum Imaging
Alia Lemkaddem1, Alessandro Daducci1, François Lazeyras2, Margitta Seeck3, Jean-Philippe Thiran1,4, and Serge Vulliemoz3
1Signal Processing Laboratory (LTS5), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, 2Dpt of Radiology, University Hospital of Geneva, Switzerland,3EEG and Epilepsy Unit, Neurology clinic, University Hospitals and Faculty of Medicine of Geneva, Switzerland, 4Dpt of Radiology, University Hospital Center (CHUV) and University of Lausanne (UNIL), Switzerland

In this study we investigated the effect of right-sided and left-sided temporal lobe epilepsy (TLE) on the global characteristics of brain connectivity estimated by topological measures. We used DSI to construct a connectivity matrix where the nodes represents the anatomical ROIs and the edges are the connections between any pair of ROIs. A significant difference was found between the patient group vs control group in characteristic path length( RTLE: p=0.007, LTLE: p=0.000493), clustering coefficient (p=0.0079, p=0.00025), strength (p=0.0088, p=0.00081) and efficiency (p=0.0099, p=0.00042). This suggests that the TLEs the network is less efficient compared to the network of the control group.


Diffusion: Applications

Wednesday 14 May 2014
Traditional Poster Hall  16:00 - 18:00

2673.   Neurite Orientation Dispersion and Density Imaging (NODDI) Adds Biophysical Insight of White Matter Microstructural Injury in Neonatal Encephalopathy
Peter J Lally1, Hui Zhang2, Shreela S Pauliah1, David L Price3, Alan Bainbridge3, Ernest B Cady3, Seetha Shankaran4, and Sudhin Thayyil1
1Perinatal Neurology and Neonatology, Imperial College London, London, United Kingdom, 2Centre for Medical Image Computing, University College London, London, United Kingdom, 3Medical Physics and Biongineering, University College London Hospitals NHS Trust, London, United Kingdom, 4School of Medicine, Wayne State University, Detroit, Michigan, United States

Descriptors of white matter (WM) diffusivity correlate with adverse neurological outcome in neonatal encephalopathy (NE). WM integrity measures derived from clinical diffusion tensor imaging are difficult to interpret in terms of microstructural morphology. We aimed to examine changes in WM microstructure associated with NE, and relate these to tangible biophysical models by fitting single-shell DTI data to the neurite orientation dispersion and density imaging (NODDI) model. Single subject maps of NODDI indices were noisy, but cohort-averaged maps (n=31) enabled characteristic changes in WM fractional anisotropy and radial diffusivity to be related to a possible reduction in neurite density.

2674.   Independent component analysis of DTI metrics in multiple sclerosis
K.A. Meijer1, M. Cercignani2, N. Muhlert1, V. Sethi1, D. Chard1, M. Ron1, A.J. Thompson1, D.H. Miller1, J.J.G. Geurts3, and O. Ciccarelli1
1NMR Unit, Queen Square MS Centre, UCL Institute of Neurology, London, United Kingdom, 2Clinical Imaging Sciences Centre, Brighton and Sussex Medical School, Brighton, United Kingdom, 3Department of Anatomy and Neuroscience, VU University Medical Centre, Amsterdam, Netherlands

We applied independent component analysis (ICA) to patients with multiple sclerosis (MS) in order to examine the specific patterns of correlation in fractional anisotropy (FA) across white matter (WM) tracts (obtained with tract-based spatial statistics). Fifteen out of eighteen components were associated with specific WM tracts and grouped in 5 classes, as previously demonstrated in healthy controls. A cluster of WM tracts, including the supratentorial commissural tracts, showed significant correlations with cognitive performance. These results suggest that microstructurally correlated WM regions are seen in MS patients and they may be important to understand the mechanisms of cognitive dysfunction.

2675.   Analysis of Normal Appearing White Matter of Multiple Sclerosis by Tensor-based Two-Compartment Model of Water Diffusion
Yasuhiko Tachibana1,2, Takayuki Obata2, Mariko Yoshida1, Masaaki Hori1, Michimasa Suzuki1, Koji Kamagata1, Issei Fukunaga1, Kouhei Kamiya1, Kazumasa Yokoyama3, Nobutaka Hattori3, Tomio Inoue4, and Shigeki Aoki1
1Department of Radiology, Juntendo University School of Medicine, Tokyo, Tokyo, Japan, 2National Institute of Radiological Science, Chiba, Chiba, Japan, 3Department of Neurology, Juntendo University School of Medicine, Tokyo, Japan, 4Yokohama City University Graduate School of Medicine, Kanagawa, Japan

Alterations in water diffusion are found in normal appearing white matter (NAWM) of multiple sclerosis (MS) patients. To detect more minor changes in this condition, a new simple method was designed to assess water diffusion using the two-compartment model combined with diffusion tensor imaging. The method allowed greater detectability of minimal changes in NAWM of MS (apparent diffusion coefficient of slow diffusion directed perpendicular to the fibers was higher with significance in MS) compared to conventional mono-exponential fit ADC.

2676.   Intravoxel incoherent motion diffusion-weighted MR imaging of benign meningiomas in brain: preliminary study
Yuchao Li1, Guangbin Wang2, and Qiang Liu2
1Shandong Medical Imaging Research Institute, Jinan, Shandong, China, 2Shandong Medical Imaging Research Institute, Jinan, China

the diagnostic performance of monoexponential model and the biexponential model using IVIM MR imaging for in brain.

2677.   The effect of b-value on ADC values in a rat U87 brain tumor model
Alexander D Cohen1, Kimberly R Pechman2, Mona Al-Gizawiy3, Christopher R Chitamber4, and Kathleen M Schmainda1,3
1Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States, 2Neurosurgery, Medical College of Wisconsin, Milwaukee, WI, United States, 3Radiology, Medical College of Wisconsin, Milwaukee, WI, United States, 4Medicine, Medical College of Wisconsin, Milwaukee, WI, United States

The apparent diffusion coefficient (ADC) depends on which b-values are used in its calculation. In this study, ADC is calculated using different combinations of b-values and compared between tumor and gray matter (GM) in a rat brain tumor model. Higher ADC was found in tumor vs. GM when lower b-values were used in its calculation, despite increased cellularity in the tumor seen on histology. Lower ADC was found in tumor vs. GM when higher b-values were used in its calculation. ADC calculated with high b-values may be more sensitive to cellularity as the faster diffusing extracellular components have been suppressed.

2678.   Assessing white matter microstructure in regions with different myelin architecture
Samuel Groeschel1,2, Thomas Schultz3,4, Gisela Hagberg2,5, Uwe Klose6, Till-Karsten Hauser6, Oliver Bieri7, Thomas Prasloski8, Alex MacKay8, Ingeborg Krägeloh-Mann1, and Klaus Scheffler2,5
1University Children's Hospital, Tuebingen, Germany, 2MPI for Biological Cybernetics, Tuebingen, Germany, 3Institute of Computer Science, University of Bonn, Germany,4MPI for Instelligent Systems, Tuebingen, Germany, 5Biomedical Magnetic Resonance, University Hospital, Tuebingen, Germany, 6Department of Diagnostic and Interventional Neuroradiology, University Hospital, Tuebingen, Germany, 7Radiological Physics, University of Basel, Switzerland, 8University of British Columbia, Vancouver, BC, Canada

In our study we assessed several white matter (WM) imaging protocols in their ability to detect the known differences in myelin architecture between the cortico-spinal tract and frontal WM regions in 18 healthy adolescents. We found that diffusion-weighted imaging parameters and myelin water fraction can give quantitative and most sensitive information about differences in myelin microstructure. From the diffusion parameters, neurite density (NODDI) was found to be more sensitive than fractional anisotropy (FA), underlining the limitation of FA in WM crossing fibre regions. Furthermore, these parameters successfully quantified loss of myelin in 5 patients with Metachromatic Leukodystrophy.

2679.   Double-Pulsed-Field-Gradient MRI at long mixing time of global hypoxia
Darya Morozov1, Debbie Anaby1, and Yoram Cohen1,2
1School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Science, Tel-Aviv University, Tel-Aviv, Ramat-Aviv, Israel, 2Sagol School of Neurosciences, Tel-Aviv University, Tel-Aviv, Ramat-Aviv, Israel

Diffusion weighted MRI and DTI, have been extensively used to study pathologies and to perform non-invasive in vivo tractography of the CNS. However, the ADC, FA and MD extracted from DWI and DTI experiments have limited sensitivity and specificity to structural changes. Therefore there is a constant need to develop new potential methods to provide more specific microstructural indices. In the present work we study the effect of global hypoxia on the indices extracted from angular d-PFG MRI at a long mixing time and compare them with the changes observed in the FA and MD obtained from DTI.

2680.   Assessing microstructural substrates of white matter abnormalities using NODDI - application to a metabolic disease
Inge Timmers1,2, Alard Roebroeck1, Matteo Bastiani1,3, Bernadette Jansma1, Estela Rubio-Gozalbo2, and Hui Zhang4
1Department of Cognitive Neuroscience, Maastricht University, Maastricht, Netherlands, 2Department of Pediatrics, Maastricht University Medical Center, Maastricht, Netherlands, 3Institute of Neuroscience and Medicine, Forschungszentrum Juelich GmbH, Juelich, Germany, 4Department of Computer Science & Centre for Medical Image Computing, University College London, London, United Kingdom

This work demonstrates neurite orientation dispersion and density imaging (NODDI) as a tool for investigating microstructural substrates of white matter abnormalities in a clinical population. NODDI estimates indices of neurite density (NDI) and orientation dispersion (ODI), two key contributors of fractional anisotropy (FA) from diffusion tensor imaging (DTI). We show that NODDI analysis of multi-shell diffusion-weighted data adds microstructural specificity to the findings from DTI. Findings from the NODDI indices overlap substantially with FA, revealing the specific microstructural changes corresponding to the latter. We additionally demonstrate that NODDI analysis of single-shell data can potentially be used for detecting ODI changes.

2681.   The Relation between Free-Water, Atrophy and Microstructural Pathologies in Retired NFL Players – A Combined Diffusion MRI and MRS study
Ofer Pasternak1, Robert A. Stern2, Michelle Y. Giwerc1, Charles Yergatian1, Sai Merugumala1, Huijun Liao1, Christine M. Baugh2, Carl-Fredrik Westin1, Martha E. Shenton1,3, and Alexander P. Lin1
1Harvard Medical School, Boston, Massachusetts, United States, 2Boston University, Boston, MA, United States, 3VA Boston Healthcare System, Brockton, MA, United States

Recent diffusion models include a free-water compartment accounting for extracellular water molecules not bounded by tissue membranes. In order to reveal the relation between free-water volume and underlying pathologies we correlate the measure with metabolite counts that were obtained in MR spectroscopy. We tested 49 retired National Football League (NFL) players at high risk for having chronic traumatic encephalopathy, and 14 controls. We find free-water differences between the groups, and that free-water mainly correlates with NAA, suggesting sensitivity to atrophy. By covarying for NAA we find that free-water correlates with other metabolites that suggest sensitivity to neuroinflammation and gliosis.

2682.   Correlations between different sources of contrast at 9.4T: diffusion vs. susceptibility
Yohan van de Looij1,2, Nicolas Kunz2, Rajika Maddage2, Rolf Gruetter2,3, Petra S Hüppi1, and Stéphane V Sizonenko1
1Division of Child Growth and Development, University of Geneva, Geneva, GE, Switzerland, 2Laboratory for Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, VD, Switzerland, 3Department of Radiology, University of Geneva and Lausanne, Geneva and Lausanne, GE and VD, Switzerland

Diffusion Tensor Imaging (DTI) and Quantitative Susceptibility Mapping (QSM) are two MR techniques given a superb contrast between white and grey matter in the brain. Diffusivity and anisotropy of water in the tissues are derived from DTI whereas QSM is based on the magnetic susceptibility distribution. The aim of this work was to investigate the potential cross correlations between DTI and QSM in the rat brain white matter at ultra-high magnetic field. In addition to the effect of magnetic field orientation and myelin, we suggest an effect of axonal diameter/compaction to the QSM contrast.

2683.   Leukoencephalopathy in acute CO intoxication: Diffusion kurtosis versus diffusivity
Ping-Huei Tsai1,2, Ming-Chung Chou3, Cheng-Yu Chen1,2, Shih-Wei Chiang4,5, Chao-Ying Wang5, Hsiao-Wen Chung4, Hung-Wen Kao5, and Yi-Hsiu Hsiao1
1Imaging Research Center, Taipei Medical University, Taipei, Taiwan, 2Department of Medical Imaging, Taipei Medical University Hospital, Taipei Medical University, Taipei, Taiwan, 3Department of Medical Imaging and Radiological Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan, 4Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, 5Department of Radiology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan

Acute CO intoxication is one of the most common lethal poisons worldwide, and could lead to brain injury resulting from leukoencephalopathy. Although diffusion tenor (DT) related parametric maps could help assess the brain structural changes resulting from demyelination, it may not be highly sensitive to observe the subtle alternations in patients with acute CO intoxication. The purpose of this study is to validate evaluate the ability of diffusion kurtosis imaging (DKI) for early detection of the brain WM microstructural changes. The present finding indicated that the use of DKI method may provide some valuable information in prediction of leukoencephalopathy in these patients.

Diffusion basis spectrum imaging (DBSI) and manganese-enhanced MRI (MEMRI) detect axonal pathologies with decreased axonal transport in optic nerves of DBA/2J mice
Chia-Wen Chiang1, Tsen-Hsuan Lin2, Joong Hee Kim1, and Sheng-Kwei Song1,3
1Radiology, Washington University School of Medicine, St. Louis, MO, United States, 2Physics, Washington University, St. Louis, MO, United States, 3The Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO, United States

In this study, in vivo diffusion basis spectrum imaging (DBSI) and manganese-enhanced MRI (MEMRI) were performed to assess axonal pathologies (inflammation, demyelination and axonal injury) and to determine the degree of axonal transport deficit in 12-month old DBA/2J mice, a rodent model of glaucoma which develops progressive degeneration of visual function mimicking human glaucoma. Our results suggest that DBA/2J mice developed inflammation, axonal injury, demyelination with significant axonal transport disruption in optic nerves compared with the age-matched controls.

Assessment of white matter tract integrity metrics in cuprizone-induced white matter degeneration with diffusion MRI
Magdalena Zurek1, Kerryanne Winters1, Jin Zhang1, Joe Rodriguez1, Dmitry S. Novikov1, Sungheon Kim1, and Els Fieremans1
1Department of Radiology, New York University School of Medicine, Bernard and Irene Schwartz Center for Biomedical Imaging, New York, New York, United States

We assessed diffusion white matter tract integrity (WMTI) metrics, in particular tortuosity and axonal water fraction (AWF), in an experimental model of cuprizone-induced WM degeneration, against conventional MRI myelin indicators and histopathology. DTI, WMTI metrics, and traditional MR myelin estimators such as T2 and MTR were sensitive to the effect of the cuprizone treatment, however the overall comparison between new and conventional parameters showed that tortuosity, and AWF were the most sensitive measures for cuprizone-induced changes. Our primarily results indicate that WMTI imaging markers can be valuable in assessing WM degeneration.

2686.   The anisotropic component of diffusion improves visualisation of fiber tracts in the presence of oedema
Lawrence Kenning1, Martin Lowry2, and Lindsay W Turnbull2,3
1Centre for Magnetic Resonance Investigations, University of Hull, Hull, East Riding of Yorkshire, United Kingdom, 2Centre for Magnetic Resonance Investigations, Hull York Medical School at the University of Hull, Hull, East Riding of Yorkshire, United Kingdom, 3Hull and East Yorkshire Hospitals NHS Trust, East Riding of Yorkshire, United Kingdom

DTI can visualise fiber tracts for surgery, however, oedema and tumour infiltration cause FA to decrease. We investigated the anisotropic component of diffusion to visualise fiber tracts in the presence of oedema. Glioma patients were scanned twice with DTI. ADC, FA and q maps were generated. Percentagewise changes of q following altered levels of oedema were reduced when compared to those of FA. Increased values of ADC are destructive to FA values given the normalisation process which q does not include. Anisotropic component of diffusion maps continue to show fiber tract directionality in the presence of large amounts of oedema.

2687.   A methodological study on DTI indices: from preprocessing to analysis with application to multiple sclerosis
Catarina Freitas1, Varun Sethi1, Nils Muhlert1, Olga Ciccarelli2, Mara Cercignani3, Declan Chard2, Hui Zhang4, and Claudia Wheeler-Kingshott1
1Department of Neuroinflammation, UCL Institute of Neurology, London, United Kingdom, 2Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, United Kingdom, 3Department of Neuroscience, University of Sussex, Brighton, United Kingdom, 4Department of Computer Science & Centre for Medical Image Computing, University College London, London, United Kingdom

Misinterpretation of differences in the diffusion tensor (DT) indices between patients and healthy controls (HC) may occur when the geometrical properties of each dataset are not taken into account. Here, we tested a new analysis method that has been suggested to solve this problem, in a group comparison of HCs and patients with multiple sclerosis (MS). In addition, we investigated the effect of registration by using DT-based and fractional anisotropy (FA)-based methods. The analysis showed the new approach may help to reveal WM subtle changes and the importance of determining which registration method is more appropriate to study WM pathology.

2688.   Investigating longitudinal changes in fractional anisotropy in Alzheimer’s disease using different registration methods
Sila Genc1, Christopher Steward1,2, Terence O'Brien3,4, and Patricia Desmond1,2
1Department of Radiology, University of Melbourne, Parkville, Victoria, Australia, 2Department of Radiology, Royal Melbourne Hospital, Parkville, Victoria, Australia,3Department of Medicine, University of Melbourne, Parkville, Victoria, Australia, 4Department of Neurology, Royal Melbourne Hospital, Parkville, Victoria, Australia

Longitudinal changes in fractional anisotropy in Alzheimer’s disease patients were investigated using three different registration methods. Recent studies have suggested alterations to the TBSS pipeline in order to improve the registration process for subsequent image analysis. Replacing the standard registrations in the TBSS pipeline in FSL, with ANTs registrations, revealed minimal differences between the spatial distributions of FA change in the core white matter tracts within six months. The consistencies between the standard TBSS, ANTS-modified TBSS, and study-specific template results suggests that running the simple TBSS pipeline may be sufficient for longitudinal analyses in complex pathologies such as Alzheimer’s disease.

2689.   A macaque brain white matter atlas based on averaged high resolution DTI
Qiaowen Yu1,2, Tina Jeon1, Austin Ouyang1, Virendra Mishra1, Steven Hsiao3, Shuwei Liu2, and Hao Huang1
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States, 2Research Center for Sectional and Imaging Anatomy, Shandong University School of Medicine, Jinan, Shandong, China, 3Mind and Brain Institute, Johns Hopkins University, Baltimore, Maryland, United States

A comprehensive characterization of white matter (WM) anatomy of macaque brain with DTI can not only provide neuroanatomical atlases for neuroscientific studies using macaque model, but also aid the study of the WM evolution. WM tracts underlie the connectivity of brain regions which play essential roles for understanding brain functions and evolution of brain functions. In this study, we aimed to generate a probabilistic and comprehensive digital macaque brain atlas including labeling of WM tracts with ultra-high resolution DTI data (0.35x0.4x0.45mm3) of a population of macaque brains.

2690.   In-vivo online monitoring of testosterone-induced neuroplasticity in a seasonal songbird
Geert De Groof1, Sofie Van Massenhoven1, Elisabeth Jonckers1, and Annemie Van der Linden1
1Bio-Imaging Lab, University of Antwerp, Antwerp, Antwerp, Belgium

Steroid hormones have a profound effect on brain plasticity and seasonal songbirds are on of the most extreme examples of this neuroplasticity (linked to song behaviour). The causality of the change in singing behaviour and neuroplasticity remains unknown. Using longitudinal DTI we measured the connectivity of the starling brain repeatedly after testosterone implantation. The connection between the main song control nuclei changed significantly after about 14 days of treatment, while plasma testosterone levels were already significantly higher at 2 days of treatment coinciding with an increase of song output. Our results thus indicate that this neuroplasticity is activity (singing) induced.

2691.   MRI of the Lung to monitoring cystic fibrosis (CF) patients with pulmonary exacerbation
Giovanni Morana1, Federica De Leo1, Valentina Tavano2, Andrea Mazzaro2, Mirco Ros3, Francesca Lucca3, Pierluigi Ciet4, and Silvia Bertolo1
1Radiology, Ca' Foncello Hospital, Treviso, Treviso, Italy, 2Padova's Hospital, Padova, Padova, Italy, 3Pediatrics, Ca' Foncello Hospital, Treviso, Treviso, Italy, 4Radiology and Pediatrics Pulmonology, Erasmus MC, Rotterdam, Rotterdam, Netherlands

Cystic Fibrosis is the most common lethal hereditary disease in the caucasian population. Currently, no sensitive, radiation-free methods are available to localize and quantify lung inflammation. Developments in MRI have made possible the clinical application of lung-MRI to obtain not only morphological but also functional information. Our propose is giving an overview of these new MR tecniques and their potential application in CF population. Lung-MRI has the potential to supply new relevant functional information in thoracic imaging. Its impact in CF follow-up has still to be defined, but it might open new therapeutic scenarios in CF and in other lung disease.

Automatic segmentation of tendons in human skeletal muscles using DTI tractography derived tract-density maps
Jos Oudeman1, Gustav J Strijkers2, Mario Maas1, Aart J Nederveen1, P Luijten3, and Martijn Froeling1,3
1Radiology, Academic Medical Center, Amsterdam, Noord Holland, Netherlands, 2Biomedical NMR, Department of biomedical engineering, Eindhoven University of Technology, Eindhoven, Brabant, Netherlands, 3Radiology, University Medical Center, Utrecht, Utrecht, Netherlands

In Diffusion Tensor Imaging (DTI) studies of skeletal muscles, segmentation is performed manually, which is tedious and difficult in complex structures. Furthermore, muscle fiber tractography often results in fibers that continue along tendon or aponeurosis due to partial volume effects. This effect leads to overestimation of muscle fiber lengths and making it difficult to identify tendon insertion points and calculate pennation angles.Due to the partial volume effects reconstructed fibers tend to curve along the tendons. Therefore we hypothesized tract density differences can be used for automatic muscle segmentation to distinguish muscle from tendon.

2693.   Assessment of inner volume imaging technique for renal tissue characterization by IVIM and DTI at 3 T
Christina Schraml1, Susanne Will2, Nina F Schwenzer1, Guenter Steidle2, Claus D Claussen1, Fritz Schick2, and Petros Martirosian2
1Department of Radiology, Diagnostic and Interventional Radiology, Tuebingen, BW, Germany, 2Department of Radiology, Section on Experimental Radiology, Tuebingen, BW, Germany

Aim of the study was to assess application of inner-volume-imaging (IVI) technique for diffusion-weighted imaging (DWI) with DTI and IVIM of the kidneys in healthy volunteers. Qualitative and quantitative comparison between IVI and full-field-of-view (FF) imaging was performed which revealed reduced distortion, less signal voids and better image quality of calculated parametric maps in IVI technique. FA values were comparable between IVI and FF technique while slight differences regarding IVIM parameters were observed. IVI technique is a promising approach for improving DWI of the kidneys. The application in patients with renal diseases is necessary to assess its clinical performance.

2694.   31P DWS of different muscles in the lower leg
Melissa Hooijmans1, Ece Ercan1, Robert Brandt1, Andrew Webb1, Hermien Kan1, and Itamar Ronen1
1Radiology, Leiden University Medical Center, Leiden, Zuid-holland, Netherlands

Conventional diffusion weighted imaging is limited by the lack of compartment specificity of water. In this work, we show the application of 31P diffusion weighted spectroscopy of individual muscles in the lower leg at 7T. SNR was sufficient to determine apparent diffusion coefficients of phosphocreatine (PCr) in two different muscles of the leg. In conclusion we are able to assess the diffusion of PCr in the individual lower leg muscles and these values seem to be affected more by cell size than fiber type distribution.

2695.   Diffusion MRI measurement of muscle fiber size and sarcolemma permeability in normal skeletal muscle growth
Kerryanne Winters1, Dmitry S. Novikov1, Els Fieremans1, and Sungheon Kim1
1Radiology, NYU School of Medicine, New York, NY, United States

We quantified the microstructural changes in normal skeletal muscle growth using time-dependent DTI combined with random permeable barrier model (RPBM). A DTI study with multiple diffusion times was conducted with 4-5 weeks and 10-12 weeks old mice, followed by immunohistochemistry staining of collagen-IV and aquaporin-4. Overall, young mice had lower unrestricted diffusivity, higher membrane surface-to-volume (S/V) ratio, and lower membrane permeability than the old mice. Our preliminary results demonstrate that the DTI-RPBM measures can be used to monitor muscle growth in wild type mice, and substantiates the potential of using the DTI-RPBM measures as quantitative biomarkers of myopathy.

Can intravoxel incoherent motion (IVIM) Replace the Conventional DWI Combined with DCE in Clinical Detection of Prostate Cancer?
Wenchao Cai1, Feiyu Li1, Jintang Ye1, Queenie Chan2, Xiaoying Wang1, and Xuexiang Jiang1
1Peking University First Hospital, Beijing, Beijing, China, 2Philips Healthcare, Hong Kong, China

Intravoxel incoherent motion (IVIM) MR imaging is a non-invasive method with the ability of separation of ¡°pure¡± molecular diffusion and perfusion effects. Radiologists perform diffusion-weighted and dynamic contrast-enhanced (DCE) MRI to provide additional diffusion and perfusion information in the routine clinical set, but it needs intravenous contrast agent administration and requires cumbersome procedures. Therefore, in this study we applied the IVIM technique to detect the prostate cancer and to compare the diagnostic performance between IVIM and conventional DWI combined with DCE. Our results demonstrated combination of D and f seemed to be more efficient than the clinical conventional DWI combined with DCE method in the diagnosis of prostate cancer