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


DIFFUSION (13:30-15:30)

4412-4435 Diffusion Biophysics & Microstructures
4436-4459 Diffusion: Acquisition Strategies
4460-4483 Diffusion Analysis
4484-4507 Diffusion Models
4508-4531 Tractography
4532-4555 Diffusion Applications

Diffusion Biophysics & Microstructures

Wednesday 14 May 2014
Exhibition Hall  13:30 - 14:30

  Computer #  
4412.   1 Probing the vitality of yeast suspensions by Double Diffusion Weighted MRI
Lars Mueller1, Andreas Wetscherek1, Jutta Janke1, Bram Stieltjes2, and Frederik Bernd Laun1
1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany, 2Quantitative Imaging-based Disease Characterization, German Cancer Research Center, Heidelberg, Germany

A double diffusion weighted sequence was implemented and tested on yeast suspension phantoms with different yeast concentrations. The sequence allowed us to determine the apparent exchange rate, which is a measure for water exchange rates across cell membranes, and the filter efficiency. Higher yeast concentrations result in lower exchange rates and higher filter efficiencies. Both parameters are dependent on the age of the yeast suspension and are shown to be good indicators of the vitality of the yeast suspension.

4413.   2 Double-PFG Filtered Diffusion Tensors
Ofer Pasternak1, Markus Nilsson2, Yoram Cohen3, Evren Ozarslan1, Hans Knutsson4, and Carl-Fredrik Westin1
1Harvard Medical School, Boston, MA, United States, 2Lund University, Lund, Sweden, 3Tel Aviv University, Tel Aviv, Israel, 4Linköping University, Linköping, Sweden

While most current double PFG methods concentrate on parameterization of new types of anisotropies in gray matter, we provide here a simple and intuitive filtered tensor based framework to explore the utility of double PFG for mapping white matter. The preliminary results shown here suggest that using filtered tensors has the potential to resolve complex fiber architecture in an intuitive, signal driven way, which is different than the typically complex model based HARDI methods.

4414.   3 Oscillating gradient diffusion MRI reveals frequency-dependent contrasts in cellular layers of the human cerebellum
Manisha Aggarwal1 and Susumu Mori1
1Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States

We investigate the effect of gradient frequency on diffusion MR contrasts derived using oscillating diffusion-sensitizing gradients in the fixed human cerebellum. Using diffusion MRI data acquired at 11.7 T with pulsed gradient and modified trapezoid-cosine oscillating gradient waveforms (at frequencies of 67, 100, 150, and 200 Hz), we report the generation of unique layer-specific contrasts in the human cerebellum. Quantitative maps derived from the rate of change in ADC measurements with gradient frequency revealed distinct anatomical contrasts highlighting specific cerebellar layers, which were compared with histologically-stained sections of the same tissue. The results demonstrate the potential of oscillating-gradient diffusion MRI acquisitions to generate anatomical contrasts that are sensitive to the microstructure of cellular layers in the human cerebellar gray matter.

4415.   4 Imaging microstructure: Application of oscillating gradient diffusion sequences on a 3T clinical MRI scanner
Lebina Shrestha Kakkar1, David Atkinson2, Rachel W Chan2, and Ivana Drobnjak1
1Center for Medical Image Computing, University College London, London, United Kingdom, 2Center for Medical Imaging, University College London, United Kingdom

Estimation of brain micro-structure parameters can be used to improve understanding of neuro-degeneration due to ageing or dementia. Recent studies show these estimations are possible using pulsed gradient spin echo sequences but are more accurately estimated using trapezoidal oscillating gradient spin echo (tOGSE) sequences. Here, we implement tOGSEs on a 3T MRI scanner and test its feasibility by imaging: (1)microcapillaries (2)an asparagus stem and (3)the corpus callosum of two healthy volunteers. Their fiber diameters were estimated using only 5 measurements with the three-stage fitting model procedure. Our results suggest good agreement with the ground truth and histology for our phantoms.

4416.   5 Mapping mean axon diameters using diffusion MRI with oscillating gradients
Junzhong Xu1, Hua Li1, Kevin D Harkins1, Jingping Xie1, Mark D Does1, and John C Gore1
1Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, United States

Due to relatively long diffusion times used, small axons are usually overestimated using PGSE-based models. In the current study, the OGSE method was implemented in fixed spinal cord measurements with much shorter effective diffusion times to enhance detection sensitivity to small axons. The results show that the fitted mean axon diameters are in very good agreement with histology.

4417.   6 Fast and robust measurement of microstructural dimensions using temporal diffusion spectroscopy
Hua Li1, John C. Gore1, and Junzhong Xu1
1Institute of Imaging Science, Vanderbilt University, Nashville, TN, United States

Current PGSE-based approaches usually require long scanning times and high q-values to detect small axons, which are limited by the long diffusion times and the significantly reduced sensitivity to small spatial scales. OGSE has been shown to achieve much shorter diffusion times and hence may be able to detect smaller axons with high sensitivity. We measure the inner diameters of hollow microcapillaries using OGSE methods. Two ADC values are sufficient to extract the cylinder diameters accurately. OGSE is insensitive to the intrinsic diffusion coefficient in the relatively low frequency range. We propose OGSE as a fast and robust method for mapping axon sizes non-invasively.

4418.   7 Axon diameter distribution (ADD) mapping of porcine spinal cord using d-PFG MRI
Dan Benjamini1,2, Michal E Komlosh1,3, Uri Nevo2, and Peter J Basser1
1NIH, Bethesda, MD, United States, 2Tel Aviv University, Tel Aviv, Israel, 3USUHS, Bethesda, MD, United States

Noninvasive estimation of a non-parametric axon diameter distribution (ADD) provides sub-voxel microstructural information of white matter tissue. ADD infers on the nerve conductivity, and is influenced by several diseases, such as amyotrophic lateral sclerosis and multiple sclerosis. A recently suggested 2D double pulsed-field gradient MRI experiment is used on a porcine spinal cord. A voxel-by-voxel non-parametric ADD estimation provides a sub-voxel resolution map. Distinct domains where the ADDs are similar are then found. ADD estimation might prove to have clinical MRI applications owing to its critical functional role in the central and peripheral nervous systems, in normal and abnormal tissue.

4419.   8 NMR characterization of cylinder radii distributions using a SHORE-based regularization method
Gonzalo Sanguinetti1, Matt G Hall2, Daniel C Alexander2, and Rachid Deriche1
1Athena Project-Team, INRIA, Sophia-Antipolis, France, 2Centre for Medical Image Computing, Department of Computer Science, University College London, London, United Kingdom

We are interested in retrieving information about the axon diameter distributions in white matter fiber bundles using NMR, which are commonly modelled as ensembles of parallel cylinders. We add regularization to the 1D-SHORE basis which results in more stable characterization of diameter distributions. To validate the method, we simulate NMR signals using the open source toolkit CAMINO. The results illustrate the enhanced estimation accuracy given by the regularization and provide an alternative validation of the SHORE based method.

4420.   9 Mathematical models of colorectal tumour microstructure informed by oscillating gradients diffusion MRI
Alessandro Proverbio1, Bernard M. Siow2,3, Eleftheria Panagiotaki3, Samuel Walker-Samuel2, Mark F. Lythgoe2, Adam P. Gibson1, and Daniel C. Alexander3
1Medical Physics and Bioengineering, University College London, London, United Kingdom, 2Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, United Kingdom, 3Centre for Medical Image Computing and Department of Computer Science, University College London, London, United Kingdom

Investigation of tissue microstructure with non-invasive histology is a developing research area. Diffusion MRI (dMRI) can estimate features of microstructural components such as cell cytoarchitecture. Here develop signal models for Square Wave Oscillating Gradient Spin Echo (SWOGSE) dMRI. This study is performed on fixed subcutaneous xenograft tumour samples grown in nude mice: 3 LS174T, and 3 SW1222 cell lines. Oscillating Gradient Spin Echo probes shorter length scales than standard PGSE. The more tissue-like compartment model appears to represent the signal better, suggesting the feasibility of a clinical measurement of cytological properties of the tissue.

4421.   10 The Importance of Angular Dispersion in Physiological Modeling of Transverse Diffusion Signal Decay
Novena A Rangwala1, David B Hackney1, and David C Alsop1
1Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, United States

In this theoretical study we have investigated the effect of axonal dispersion in white matter on the accuracy of physiological parameters estimated with a diffusion model incorporating axonal dispersion into AxCaliber. Diffusion signal decay was estimated with a characteristic dispersion angle of 6°, at diffusion times 20–1000 ms and two axonal diameter distributions, and fit to AxCaliber equations without angular dispersion. Results show that although AxCaliber can fit the signal decay curves effectively, the fitted parameters do not accurately match the assumed physiological parameters. These results strongly suggest that models of diffusion signal decay include axonal dispersion, even in white matter tracts with well-aligned fibers.

4422.   11 Changes in epithelium, stroma, and lumen space predict ADC changes with prostate cancer Gleason grade
Aritrick Chatterjee1, Geoff Watson2, Esther Myint3, and Roger Bourne1
1Faculty of Health Sciences, University of Sydney, Sydney, NSW, Australia, 2Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, Sydney, NSW, Australia, 3Laverty Pathology, Sydney, NSW, Australia

Reduced water ADC in cancer tissue is commonly attributed to “increased cellularity”, however, this explanation includes many assumptions about the diffusion properties of tissue. We hypothesise that the biophysical basis of reduced ADC in prostate cancer may instead lie in an increased partial volume of low diffusivity epithelial cells and loss of higher diffusivity stroma and lumen space. Partial volumes of epithelium, stroma, and lumen space were measured in histology images. There was a significant increase in epithelium volume and decrease in stroma and lumen space with Gleason grade. Predicted ADC changes explained about half the variation seen in vivo.

4423.   12 Quantifying in-vivo changes in myofiber diameter due to muscular atrophy with time-dependent diffusion MRI
Gregory Lemberskiy1,2, Els Fieremans1, Thorsten Feiweier3, Leon Axel1, and Dmitry S Novikov1
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, 3Siemens AG, Healthcare Sector, Erlangen, Germany

The random permeable barrier model (RPBM) utilizes time-dependent diffusion to quantify cell size and membrane permeability. Human in-vivo RPBM validation was performed on individuals that experienced calf muscle atrophy while immobilized in a non-weight bearing cast. The RPBM was used to quantify the difference of myofiber size in immobilized and control calf muscles. Muscle groups of immobilized calf muscles of all volunteers were significantly smaller than those of the control leg. Additionally, the RPBM revealed that certain muscle groups atrophied less due to degrees of freedom offered by the cast.

4424.   13 Diffusion modeling in brain cell geometries parameterized according to morphometric statistics - permission withheld
Julien Valette1
1Molecular Imaging Research Center (MIRCen), Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France

An original diffusion modeling approach is proposed to capture some features of brain cells complexity and heterogeneity, while parameterizing the model with only a small set of parameters based on cell morphometric statistics as derived from microscopy. We exemplify how this approach allows evaluating the effect of long-range cell morphology (i.e. cellular processes branching and length) on the apparent diffusion coefficient (ADC) of intracellular molecules, as might be measured by diffusion-weighted MRI/spectroscopy at long diffusion times Td.

4425.   14 Inverse Laplace transform analysis of the DWI MRI signal in prostate and bladder
Milica Medved1, Shiyang Wang1, Steffen Sammet1, Ambereen Yousuf1, Gregory S Karczmar1, and Aytekin Oto1
1Radiology, University of Chicago, Chicago, Illinois, United States

The non-mono-exponential nature of the DWI signal decay in the prostate is well established. Current advanced modeling methods use a two component model, and the data is fit for the fast (corresponding to the coherent motion in blood vessels) and slow (describing the inherent diffusion properties of the glandular tissue) components. Using a new implementation of the inverse Laplace transform, we present evidence that multiple slow components can be present in the decaying DWI signal. We demonstrate evidence for single-component diffusion in the bladder, and for presence of up to three components in the peripheral zone of the prostate.

4426.   15 3D structure tensor analysis of light microscopy data for validating diffusion MRI
Ahmad Raza Khan1,2, Lindsey A Leigland3, Steven G Kohama1, Anda Cornea1, Sune Nørhøj Jespersen4, and Christopher D Kroenke1,2
1Division of Neuroscience, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon, United States, 2Advanced Imaging Research Center, Oregon Health & Science University, Portland, Oregon, United States, 3Advanced Imaging Research Center, Oregon Health & Science University, Beaverton, Oregon, United States, 4Center of Functionally Integrative Neuroscience, Aarhus University Hospital, Aarhus, Denmark

Recently, two-dimensional structure tensor (ST) analysis has been applied to light microscopy images for the purpose of validating diffusion anisotropy measurements. The ST analysis strategy enables the microscopy data to be analyzed in a high-throughput manner, and hence is suitable for group-comparison studies. However, 2D analyses are restricted to directions parallel to the imaging plane. Here we show it is possible to extend ST analyses to 3D using serial image "stacks" acquired with confocal microscopy of nonhuman primate brain tissue. It is expected that this generalization of the ST analysis will extend its range of applications in future studies.

4427.   16 A novel method for realistic DWI data generation
Daniele Perrone1, Jan Aelterman1, Ben Jeurissen2, Aleksandra Pizurica1, Wilfried Philips1, and Jan Sijbers2
1IPI-TELIN-IMINDS, University of Gent, Gent, East Flanders, Belgium, 2Vision Lab, University of Antwerp, Antwerp, Antwerp, Belgium

Diffusion Weighted Imaging (DWI) was introduced to explore the human connectome in vivo; although many fiber tractography (FT) algorithms exist, proving the effectiveness of their estimates is challenging. We present a biologically and physically realistic software phantom, with brain-like fibres configuration and images, fully tunable in terms of ‘simulated acquisition’ parameters: a realistic bench test for quantitative analyses of every DWI-related algorithm.

4428.   17 Methods for comparing fiber orientation distribution (FOD) functions based on histology and diffusion MRI
Yurui Gao1, Ann Choe2, Iwona Stepniewskwa3, Xia Li2, and Adam W Anderson4
1VUIIS, Vanderbilt University, Nashville, Tennessee, United States, 2VUIIS, Vanderbilt University, TN, United States, 3Psychology, Vanderbilt University, TN, United States, 4BME, Vanderbilt University, TN, United States

In previous studies, we validated DTI-tractography-derived connectivity by comparing with the histological ground truth. Because DTI fiber orientation estimation is the basis of tractography, juxtaposing the DTI fiber orientation distribution (dFOD) and histological FOD (hFOD) is critical to validation studies. However, obtaining the 3D hFOD is challenging. This study introduces 1) two methods to extract the hFOD from z-stack micrographs and 2) the procedure to compare dFOD with hFOD functions.

4429.   18 NAA spectroscopy correlates with intra-axonal compartment parameters from diffusion MRI
Elan J. Grossman1,2, Ivan I. Kirov1, Oded Gonen1, Dmitry S. Novikov1, Robert I. Grossman1, Matilde Inglese3, and Els Fieremans1
1Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, New York, United States, 2Department of Physiology and Neuroscience, NYU School of Medicine, New York, New York, United States, 3Department of Neurology, Radiology, and Neuroscience, Mount Sinai School of Medicine, New York, New York, United States

The relationship between compartment-specific white matter tract integrity (WMTI) parameters from diffusion MRI and concentrations of neurochemicals was investigated in vivo using 1H-MRS on a cohort of patients with mild traumatic brain injury (MTBI). Results demonstrated significant correlations associating n-acetylaspartate (NAA) with those WMTI parameters that are affected by intra-axonal diffusion and axonal density, suggesting the validity of a two-compartment non-exchange model of intra- and extra-axonal diffusion in a single WM fiber bundle. Our results also indicate that NAA may influence downstream processes related to axonal shrinkage, degeneration, and/or loss, as well as plasma osmolarity and myelin synthesis in MTBI.

4430.   19 Quantifying non-invasive MRI parameters with angiogenesis and cellular infiltration to characterize collagen-sponge remodeling
Mohammed Salman Shazeeb1,2, Sivakumar Kandasamy2, Stuart Howes2, and George Pins2
1Radiology, University of Massachusetts Medical School, Worcester, MA, United States, 2Biomedical Engineering, Worcester Polytechnic Institute, Worcester, MA, United States

Invivo evaluation of biomaterial implant remodeling involves surgical removal of the implant for subsequent histological assessment. This approach is often destructive and imposes practical limitations on how effectively these materials can be evaluated. MRI has the potential to non-invasively monitor the remodeling of collagen scaffolds. This study investigated the development of a model system to quantify MRI parameters with angiogenesis and cellular infiltration of implanted collagen scaffolds using MRI and histological techniques. Correlations between MRI and histological parameters demonstrated that MRI is sensitive to specific remodeling parameters which can aid in the design of robust biomaterial scaffolds for tissue regeneration.

4431.   20 Integrated Phantom Analysis of Perfusion, Diffusion, and Fluctuation MRI - permission withheld
Naoki Ohno1, Tosiaki Miyati1, Tomohiro Chigusa1, Hikaru Usui1, Noam Alperin2, Shinnosuke Hiratsuka1, Akihiro Asano1, Hirohito Kan3, Satoshi Kobayashi1, Toshifumi Gabata1, and Osamu Matsui1
1Kanazawa University, Kanazawa, Japan, 2University of Miami, FL, United States, 3Nagoya City University Hospital, Nagoya, Japan

To clarify relations and mechanisms among blood-perfusion, water-diffusion, water-fluctuation, and biomechanics of the intracranial tissue, we developed an original cranial phantom for magnetic resonance imaging. The new cranial phantom consisted of a high-density polypropylene filter with intra- and extra-filter spaces, and a capacitor space, which were filled with water at 17 degrees centigrade. These correspond to a brain parenchyma, artery and vein, and cerebrospinal fluid space, respectively. Our original phantom makes it possible to clarify relations and mechanisms among blood-perfusion, water-diffusion, water-fluctuation, and biomechanics of intracranial tissue. Perfusion, diffusion, fluctuation, and biomechanics of the intracranial tissue interact in diverse ways.

4432.   21 Magnetic Resonance Microscopy of the Drosophila Brain at 10 Micron Isotropic Resolution - permission withheld
Choong Heon Lee1,2, Stephen J Blackband1,2, and Fernandez-Funez Pedro1,3
1Neuroscience, University of Florida, Gainesville, FL, United States, 2McKnight Brain Institute, Gainesville, FL, United States, 3Neurology, University of Florida, FL, United States

Understanding the complex brain architecture and functional connectivity using MRI has been a major interest in neuroscience. Based on the capability of MR microscopy to visualize the mammalian and human cells, the desire to map the entire human brain circuit at the resolution high enough to visualize cell-level structures is becoming a reality. Studies of a simpler brain, i.e. Drosophila, are significant due to its high genetic tractability together with high degree of conservation with humans at the genetic and cellular levels. To visualize the neuronal circuitry in the brain, we acquired MRM of it at 10 µm isotropic resolution.

4433.   22 In-Bore Oxygenator Designed for Physiological Maintenance of Slice and Cell Culture Preparations Employed in MR Microscopy Studies
Jeremy J Flint1,2, Kannan M Menon2,3, Brian Hansen4, and Stephen J Blackband1,5
1Neuroscience, University of Florida, Gainesville, Florida, United States, 2McKnight Brain Institute, University of Florida, Gainesville, Florida, United States,3Biomedical Engineering, University of Florida, Gainesville, Florida, United States, 4Center for Functionally Integrative Neuroscience, Aarhus University, Aarhus, Denmark, 5National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, United States

Recent developments allowing direct visualization of cellular structure in excised mammalian tissue using MRI techniques have created a need for micro-perfusion equipment capable of operating in conjunction with high-field spectrometer hardware. This study details the design and fabrication of an in-bore oxygenator capable of offering precise control of perfusate properties including pH and dissolved gas (O2 & CO2) content. In addition, a stability assessment is conducted which compares diffusion signal reproducibility over time under conditions of constant perfusion as compared to a static control group. Findings indicate statistical equivalence at 13 of 14 time-points sampled over a 21 hour period.

4434.   23 In Vivo Observation of Time-Dependent Diffusion in White Matter in Humans
Lauren Burcaw1, Jelle Veraart2, 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, 2Vision Lab, Department of Physics, University of Antwerp, Antwerp, Belgium

We report on time-dependent diffusion in white We report on time-dependent diffusion in white matter as measured on three normal human volunteers over diffusion times ranging from 26 to 400 ms. A decrease in axial diffusivity with time is found indicating the presence of restrictions to diffusion along the axonal direction. We also note a decrease in radial diffusion with respect to time, however this decrease is less pronounced. Our results imply that axial and possibly radial time-dependent diffusion may be observable using clinical systems.

4435.   24 Magnetic resonance microscopy of fixed breast tissue - permission withheld
Narina Norddin1,2, Ned Charles1, Nyoman Kurniawan3, Gary Cowin3, Laurence Gluch4, Carl Power5, Geoffrey Watson6, and Roger Bourne1
1Faculty of Health Sciences, University of Sydney, Camperdown, NSW, Australia, 2Kulliyyah of Allied Health Sciences, International Islamic University Malaysia, Kuantan, Pahang, Malaysia, 3University of Queensland, Brisbane, Queensland, Australia, 4The Strathfield Breast Centre, Strathfield, NSW, Australia, 5University of New South Wales, Sydney, NSW, Australia, 6Royal Prince Alfred Hospital, Sydney, NSW, Australia

Conventional MRI has high sensitivity for breast cancer detection but poor specificity.Addition of DWI to a breast exam may increase specificity to around 90%.However,the biophysical basis of changes in diffusion weighted contrast in the breast and other non-neural tissue remains poorly understood.The study described here investigates the microscopic diffusion properties of formalin fixed breast tissue.Breast tissue glandular epithelium is similar to prostate tissue epithelium in having a low ADC relative to adjacent tissue.Low ADC may be a distinctive and diagnostically useful feature of glandular epithelia,not only in prostate and breast,particularly considering that 80-90% of all cancers are of epithelial origin.


Diffusion: Acquisition Strategies

Wednesday 14 May 2014
Exhibition Hall  13:30 - 14:30

  Computer #  
4436.   25 Asymmetric Two-Dimensional Spatially Selective Excitation in Echo-Planar Imaging
Rainer Schneider1,2, Jens Haueisen2, and Josef Pfeuffer1
1MR Application Development, Siemens Healthcare, Erlangen, Bavaria, Germany, 2Institute of Biomedical Engineering and Informatics, TU Ilmenau, Ilmenau, Thuringia, Germany

An asymmetric design is introduced to 2-D spatially selective radiofrequency (2DRF) pulses based on an echo-planar trajectory. The proposed design allows a significant reduction of pulse durations maintaining the excitation quality. This can be done independent of potential pulse accelerations with parallel transmission. Excitation quality with different asymmetry factors was analyzed in a phantom study. Asymmetric 2DRF pulses were evaluated in human diffusion-weighted experiments. Linked to the resulting TE savings, asymmetric 2DRF pulses offered SNR gains of up to 25% compared to the conventional 2DRF designs.

4437.   26 Reduced field-of-view diffusion with 2D echo-planar RF excitation and Multiband refocusing for extended slice coverage and robust fat suppression
Suchandrima Banerjee1, Emine Ulku Saritas2,3, Rachel Connett1, and Ajit Shankaranarayanan1
1Global Applied Science Laboratory, GE Healthcare, Menlo Park, California, United States, 2Department of Electrical and Electronics Engineering, Bilkent University, Bilknet, Ankara, Turkey, 3National Magnetic Resonance Research Center, Bilknet University, Bilknet, Ankara, Turkey

Reduced field-of-view (rFOV) single-shot echo-planar imaging (ssEPI) with 2D Echo-planar (EP) RF excitation can improve diffusion image quality and enable high resolution, by reducing distortion. However slice coverage can be limited because of periodic repetitions of the excitation sidelobes appearing along the slice direction. We propose to address this constraint by using a multiband refocusing scheme that will simultaneously refocus multiple excitation lobes. Signal from the simultaneously refocused slice locations can be separated using parallel imaging method. We demonstrate that by using multiband refocusing with 2D EPRF in ssEPI, slice coverage can be increased while preserving rFOV and fat suppression.

4438.   27 Correcting for B1 inhomogeneities in post-mortem DWSSFP human brain data at 7T using multiple flip angles
Sean Foxley1, Saad Jbabdi1, Stuart Clare1, and Karla Miller1
1FMRIB Centre, University of Oxford, Oxford, OXON, United Kingdom

Due to the comparably sized RF wavelength at 7T, human brain imaging suffers from a central ‘bright spot’. Here, we investigated the implementation of a multiple flip angle approach to account for this B1 dependent artifact. Data were acquired at 7T of post-mortem human brain using a diffusion weighted steady-state free precession pulse sequence. Two flip angles were chosen using a described optimization method and DTI data were acquired using both. Results demonstrate that the primary diffusion direction was more accurately estimated in gray matter where signal loss due to B1 decreases have made this otherwise difficult to detect.

4439.   28 Three-Dimensional Diffusion-Prepared Balanced Steady-State Free Precession with Variable Flip Angle Scheme
Yuji Iwadate1, Mitsuharu Miyoshi1, and Hiroyuki Kabasawa1
1Global MR Applications and Workflow, GE Healthcare Japan, Hino, Tokyo, Japan

In diffusion preparation methods, the k-space signal modulation by T1 recovery results in image degradation if its effect is not negligible. We developed 3D diffusion-prepared balanced steady-state free precession pulse sequence with a variable flip angle technique to correct for the T1 recovery effects during data acquisition. In both simulation and phantom scan, variable flip angle reduced edge enhancement effect when we used centric view ordering. This technique can lead to homogeneous 3D diffusion weighted image acquisition of subjects with short T1 recovery times.

4440.   29 Acoustic noise optimized Diffusion-Weighted Imaging (DWI)
Martin Ott1, David Porter2, Felix Breuer1, David Grodzki2, Martin Blaimer1, Björn Heismann2, and Peter Jakob1,3
1MRB Forschungszentrum für Magnet-Resonanz-Bayern e.V., Würzburg, Bavaria, Germany, 2Siemens AG, Erlangen, Bavaria, Germany, 3Department of Experimental Physics 5, University of Wuerzburg, Würzburg, Germany

Diffusion-Weighted Imaging (DWI) is one of the loudest and most challenging sequence in terms of acoustic-noise due to the requirement of strong and fast switching gradients. In this work, among other gradient optimizations, a rs-EPI readout is modified to consequently minimize slew rates and hence acoustic-noise. Methodical modifications are presented as well as corresponding acoustic-noise measurements. A significant reduction in acoustic-noise of over 15dB(A) could be achieved. In-vivo imaging results are compared to standard methods like single-shot EPI.

4441.   30 Improve Image Homogeneity of High-Resolution DWI
Jiazheng Wang1 and Yongchuan Lai2
1STO-MR, GE Healthcare, Beijing, Beijing, China, 2GE Healthcare, Beijing, China

EPI based diffusion imaging is widely used yet suffers from geometric distortions, which become more pronounced in high resolution imaging. This work presents a method to implement 2D excitation for high-resolution EP-DWI with reduced phase encoding FOV, and thus to reduce the geometric distortion. Comparing to prior-art technique, the 2D excitation in this work is equipped with a pair of walking-saturations, which can improve the excitation profile in the phase encoding FOV direction and get more homogeneous imaging results. The proposed method is also shown to increase the max number of slices per TR comparing to traditional 2D excitation.

4442.   31 Updating Shim Dynamically During Diffusion Tensor Imaging Acquisition
A. Alhamud1, Aaron T. Hess2, Paul A. Taylor1,3, Ernesta M. Meintjes1, and André J.W. van der Kouwe4
1Human Biology,MRC/UCT Medical Imaging Research Unit, University of Cape Town, Cape Town, Western Cape, South Africa, 2University of Oxford, Oxford, United Kingdom, 3African Institute for Mathematical Sciences, Western Cape, South Africa, 4Massachusetts General Hospital, Charlestown, Massachusetts, United States

Diffusion tensor imaging (DTI) is characterized by a long acquisition time in which B0 homogeneity may change from one TR to another, or from one DTI scan to another due to many factors especially if head position changes (e.g. acquiring DTI in two different phase encoding directions ‘AP and PA’ ). Several studies have focused on evaluating the changes in B0 for fMRI, but this issue has been largely neglected for DTI. In this work, we present the first study to measure, report and correct the inhomogeneity in the static field with simultaneous real time shim correction,TR-by-TR, in real time.

4443.   32 Diffusion Weighted Imaging of In-vivo heart with 2nd moment nulling diffusion gradient
Tetsuo Ogino1,2, Toshiaki Miyati3, Marc Van Cauteren4, Tomoya Nakamura5, Taro Takahara6, and Yutaka Imai6
1Healthcare department, Philips Electronics Japan, LTD, Minato-ku, Tokyo, Japan, 2division of Health Sciences, Kanazawa University, Kanazawa, Ishikawa, Japan, 3Kanazawa University, Kanazawa, Ishikawa, Japan, 4Philips Healthcare LTD, Tokyo, Japan, 5Tokai University Hospital, Kanagawa, Japan, 6Tokai University, Kanagawa, Japan

A second moment nulling on diffusion gradients combined with ECG triggering for in-vivo myocardial diffusion weighted imaging was investigated its clinical feasibility. Uniform DWI signal was obtained with b-factor = 500 s/mm2 and clinically acceptable image quality with moderate signal non-uniformity was achieved up to b=800 s/mm2.

4444.   33 POCS-ICE: POCS based Inherent Correction of phase Errors for multi-shot spiral DWI
Xiaodong Ma1, Feng Huang2, Zhe Zhang1, Bida Zhang2, Sheng Fang3, 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, 3Institute of nuclear and new energy technology, Tsinghua University, Beijing, China

POCS based Inherent Correction of motion-induced phase Errors (POCS-ICE) is proposed for the reconstruction in multi-shot spiral DWI, which can automatically correct the phase variation among different excitations without calculating them directly. Invivo experiments show that DW images from POCS-ICE present higher SNR and less aliasing artifacts than SENSE+CG when a large shot number is used. Therefore, it can contribute to shortening the spiral readout duration such that high resolution diffusion weighted images can be achieved.

4445.   34 Self-feeding MUSE: A Method for High Resolution Diffusion Weighted Imaging with Robust Phase Variation Estimation
Zhe Zhang1, Feng Huang2, Bida Zhang3, Sheng Fang4, and Hua Guo1
1Center for Biomedical Imaging Research, Department of Biomedical Enginnering, School of Medicine, Tsinghua University, Beijing, China, 2Philips Healthcare, Gainesville, FL, United States, 3Philips Research China, Beijing, China, 4Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, China

Multi-shot strategies have been used for improving spatial resolution of DWI. MUSE is a multi-shot EPI based DWI method using SENSE for self-navigating of each shot. When many shots are used to decrease the EPI distortion and blurring, high SENSE reduction factor will cause inaccurate phase estimation and thus ghost artifacts. In this work, Self-feeding MUSE is proposed for robust phase estimation and improved MUSE reconstruction, even if the number of shots is high.

Merry Mani1, Mathews Jacob2, Vincent Magnotta2, and Jianhui Zhong1
1University of Rochester, Rochester, NY, United States, 2University of Iowa, Iowa, United States

Applications such as the study of human brain connectivity and pre-surgical planning can greatly benefit from high angular and spatial resolution diffusion data. Non-Cartesian multi-shot diffusion imaging schemes can offer high spatial resolution diffusion images. Coupled with high angular resolution schemes, it can enable the reconstruction of high fidelity fiber tracts. However, non-Cartesian multi-shot image reconstruction can be prohibitively time-consuming because of the need to account for motion-induced phase terms in the reconstruction to avoid motion artifacts. A fast reconstruction scheme is proposed using a PCA-based approximation, to accelerate the motion-compensated reconstruction of high angular and spatial resolution diffusion data.

4447.   36 High-quality and High-throughput Interleaved Diffusion Weighted EPI Enabled by Multi-band Multiplexed Sensitivity Encoding (MUSE) and Adaptive Partial Fourier Reconstruction
Hing-Chiu Chang1, Shayan Guhaniyogi1, and Nan-Kuei Chen1
1Brain Imaging and Analysis Center, Duke University Medical Center, Durham, North Carolina, United States

Multiplexed sensitivity encoding (MUSE) can effectively remove aliasing artifact due to shot-to-shot phase inconsistencies without relying on navigator echo. However, the conventional partial Fourier reconstruction procedure included in the original MUSE is highly susceptible to motion-induced k-space energy peak displacement, and the imaging throughput of multi-shot MUSE is significantly lower than single-shot DWI. We first develop a novel adaptive partial Fourier reconstruction procedure capable of producing high-quality multi-shot DWI, even in the presence of motion-induced k-data energy displacement. Next, we generalize the MUSE reconstruction to accommodate multi-band data, so that high-throughput, high-resolution and high-quality DWI can all be simultaneously achieved.

4448.   37 Clinically Feasible NODDI Characterization of Brain Tumor in 5.5 minutes Using Multiband EPI at 7T
Qiuting Wen1,2, Douglas A.C. Kelley3, Suchandrima Banerjee4, Janine M. Lupo2, Duan Xu2, Christopher P. Hess2, and Sarah J. Nelson1,2
1Graduate Program in Bioengineering, University of California, San Francisco & Berkeley, San Francisco, CA, United States, 2Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States, 3Global Applied Science Laboratory, GE healthcare, San Francisco, CA, United States, 4Global Applied Science Laboratory, GE healthcare, Menlo Park, CA, United States

The goal of this study was to demonstrate the feasibility of acquiring 7T data suitable for NODDI in under 6 minutes with a tailored multiband technique for routine clinical application. In a brain tumor patient NODDI provided unique contrast within the T2 lesion. Although NODDI does not directly model tumor characteristics, it demonstrates great potential in revealing underlying tissue components that are complimentary to FA and ADC. With the multiband EPI technique, we reduced the acquisition time of this two-shell diffusion sequence to 5.5 minutes, making it clinically feasible. In addition to NODDI, both diffusion tensor and tractography data can also be generated from this protocol.

4449.   38 Accelerated human cardiac diffusion tensor imaging using simultaneous multi-slice imaging
Angus Z. Lau1,2, Elizabeth M. Tunnicliffe1, Robert Frost3, Peter J. Koopmans3, Damian J. Tyler1,2, and Matthew D. Robson1
1Department of Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom, 2Department of Physiology, Anatomy, and Genetics, University of Oxford, Oxford, United Kingdom, 3FMRIB Centre, University of Oxford, Oxford, United Kingdom

Remodeling of cardiac fibre structure contributes to impaired cardiac function, and is implicated in the development of cardiac arrhythmias and sudden cardiac death. Diffusion tensor imaging (DTI) allows non-invasive detection of microstructure in vivo, but low SNR leads to long scan times, limiting the patient population which can benefit from such exams. In this abstract, we investigate the feasibility of using simultaneous multi-slice (SMS) excitation to accelerate human DTI of the heart. We demonstrate three-fold scan time reduction of cardiac diffusion measurements, and we anticipate this development will make it practical to incorporate DTI within a comprehensive clinical exam.

4450.   39 An Information Theoretic Approach to Optimal Q-space Sampling
Hans Knutsson1 and Carl-Fredrik Westin2,3
1Biomedical Engineering, CMIV, Linköping, Östergötland, Sweden, 2Harvard Medical School, MA, United States, 3Linköping University, Östergötland, Sweden

We present a novel approach to determine a local q-space metric that is optimal from an information theoretic perspective with respect to the expected signal statistics. The obtained metric will then serve as a guide for the generation of specific q-space sample distributions. It should be noted that the approach differs significantly from the classical estimation theory approach, e.g. one based on Cramer-Rao bounds. The basis for finding the q-space metric is to compute the information gain from measuring at a second q-space location given that we already have information from a first location.

4451.   40 Sparse isotropic q-space sampling distribution for Compressed Sensing in DSI
Alexandra Tobisch1,2, Gabriel Varela3, Rüdiger Stirnberg1, Hans Knutsson4, Thomas Schultz2,5, Pablo Irarrázaval3,6, and Tony Stöcker1
1German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany, 2University of Bonn, Bonn, Germany, 3Biomedical Imaging Center, Pontificia Universidad Católica de Chile, Santiago, Metropolitan District, Chile, 4Linköping University, Linköping, Sweden, 5MPI for Intelligent Systems, Tübingen, Germany, 6Department of Electrical Engineering, Pontificia Universidad Católica de Chile, Santiago, Metropolitan District, Chile

The Compressed Sensing (CS) technique accelerates Diffusion Spectrum Imaging (DSI) through sub-Nyquist sampling in q-space and subsequent nonlinear reconstruction of the diffusion propagator. State-of-the-art DSI approaches that exploit CS apply Cartesian undersampling patterns. Recently, a method was proposed to generate 3D non-Cartesian sample distributions that aim for isotropic sampling of q-space. This work compares the new scheme to standard Cartesian undersampling patterns in sparse reconstruction of simulated diffusion signals. The diffusion propagator and the corresponding orientation distribution function of the reconstruction are found to deviate less from the ground truth when using an isotropic q-space sample distribution.

4452.   41 Optimizing Q-Space Sampling Density for Diffusion Spectrum Imaging
Qiyuan Tian1, Ariel Rokem2, Brian L. Edlow3, Rebecca D. Folkerth4, and Jennifer A. McNab5
1Department of Electrical Engineering, Stanford University, Stanford, CA, United States, 2Department of Psychology, Stanford University, Stanford, CA, United States, 3Department of Neurology, Massachusetts General Hospital, Boston, MA, United States, 4Department of Pathology, Brigham and Women's Hospital, Boston, MA, United States, 5Department of Radiology, Stanford University, Stanford, CA, United States

Diffusion spectrum imaging is an approach to characterizing complex tissue microstructure. Stronger gradients enable expanded q-space coverage, which improves the spin-displacement resolution but also increases the q-space sampling density requirements. Here, we show three datasets acquired on a whole, fixed, human brain acquired with 300mT/m maximum gradients. These data are used to examine the effects of q-space sampling density on the fidelity of the voxel-wise orientation distribution functions (ODFs). Specifically, we show there is trade-off between ODF sharpness and aliasing artifacts when sampling density is insufficient to capture the spin-displacement pattern.

4453.   42 Rotating Field Gradient (RFG) Diffusion MRI for Mapping 3D Orientation Distribution Functions (ODFs) in the Human Brain
Alexandru V Avram1, Joelle E Sarlls2, Peter J Basser1, and Evren Ozarslan3
1Section on Tissue Biophysics and Biomimetics, NICHD, National Institutes of Health, Bethesda, MD, United States, 2NINDS, National Institutes of Health, Bethesda, MD, United States, 3Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States

Conventional methods for mapping 3D diffusion orientation distribution functions (dODFs) of neuronal microstructure require long acquisitions and are prone to quantitation errors due to subject motion. In this study we describe a method for directly measuring in vivo 3D dODFs with a novel technique called Rotating Field Gradient (RFG) diffusion MRI, which applies sinusoidal diffusion gradients in arbitrarily oriented planes to directly sample the dODFs along the axis of rotation. RFG dMRI represents a fast, direct and model-free method for mapping 3D ODFs that could represent a powerful alternative to conventional pulse-field gradient diffusion MRI techniques.

4454.   43 What do we gain from multiple q-shell acquistions in high angular resolution diffusion imaging? - permission withheld
Jonas Cordes1, Peter Neher1, Hans-Peter Meinzer1, Bram Stieltjes2, and Klaus Maier-Hein1,2
1Medical and Biological Informatics, German Cancer Research Center (DKFZ), Heidelberg, Baden-Württemberg, Germany, 2Quantitative Image-based Disease Characterization, German Cancer Research Center (DKFZ), Heidelberg, Baden-Württemberg, Germany

Here we present a set of metrics and experiments that evaluate the performance of several single- and multi-shell high angular resolution diffusion imaging (HARDI) acquisition schemes. In particular, we assess the angular resolution, the peak accuracy, the peak precision as well as the distribution function accuracy and distribution function precision at several different fiber configurations. We show that low b-value acquisitions in a multi-shell configuration can reach similar performances as high b-value acquisitions on a single shell.

4455.   44 Probing white matter microstructure at high spatial resolution combining CHARMED protocol optimization and a high performance gradient set
Matteo Bastiani1, Silvia De Santis2,3, Derek Jones2,3, Yaniv Assaf4, and Alard Roebroeck1
1Department of Cognitive Neuroscience, Maastricht University, Maastricht, Limburg, Netherlands, 2CUBRIC, School of Psychology, Cardiff University, Cardiff, United Kingdom, 3Neuroscience and Mental Health Research Institute, Cardiff University, Cardiff, United Kingdom, 4Department of Neurobiology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel

The composite hindered and restricted model of diffusion (CHARMED) typically requires multiple acquisitions with high b-values and high angular resolution, both of which are difficult to obtain with clinical MRI systems. The purpose of this study is to investigate the feasibility of probing white matter microstructure at high spatial resolution in vivo at 3T, combining protocol optimization and a high amplitude, high slew-rate gradient set. Different levels of trade-off between resolution, SNR and diffusion contrast are compared and the results are further compared to a benchmark dataset obtained from the Human Connectome Project (HCP).

4456.   45 Diffusion tensor imaging with 1mm isotropic resolution using a dual-echo steady-state method at 3T
Vincent Gras1, Ezequiel Farrher1, Farida Grinberg1, and N Jon Shah1,2
1INM-4, Research Centre Jülich GmbH, Jülich, Germany, 2Department of Neurology, RWTH Aachen University, Aachen, Germany

We investigate the applicability of the dual echo steady state pulse sequence with diffusion-weighting field gradients (DW-DESS) to characterize the anisotropic diffusion of water molecules in a dedicated anisotropic diffusion fibre phantom. The conventional diffusion tensor imaging (DTI) model is used for the data analysis and a comparison with the gold standard pulse sequence for DTI, namely the DW spin-echo EPI sequence, is carried out. A good agreement between both pulse sequences is demonstrated. Finally the feasibility of applying DW-DESS for high resolution DTI in vivo is discussed.

4457.   46 Effect of Diffusion Time on Intravoxel Incoherent Motion Parameters in Abdominal Organs
Yeeliang Thian1, Matthew R. Orton2,3, David J. Collins2,3, James A. d'Arcy2,3, Martin O. Leach2,3, Thorsten Feiweier4, and Dow-Mu Koh1
1Department of Radiology, Royal Marsden Hospital, Sutton, Surrey, United Kingdom, 2CR-UK and EPSRC Cancer Imaging Centre,Institute of Cancer Research UK, Surrey, United Kingdom, 3Royal Marsden Hospital, Surrey, United Kingdom, 4Siemens AG, Healthcare Sector, Erlangen, Germany

The intra-voxel incoherent motion (IVIM) model relates signal decay on diffusion-weighted MRI (DWI) to tissue characteristics of perfusion and diffusivity. We explored the effects of altering the diffusion time of DWI sequences on IVIM perfusion (f,D*) and diffusion (D) related parameters in abdominal organs of healthy volunteers. At longer diffusion times, the calculated perfusion fraction (f) was significantly increased while the effect on the D and D* parameters was more variable, depending on the organ under study. The diffusion time has a significant impact on measured IVIM parameters in abdominal organs and should be reported when employing the IVIM model.

4458.   47 Prostate MRI : comparison of generalized autocalibrating partial parallel acquisition (GRAPPA) -accelerated readout-segmented echo-planar imaging (EPI) and single-shot EPI in clinical application of diffusion-weighted imaging at 3 T
Liang Li1, Liang Wang1, Hui Liu2, Ming Deng1, Zhao-Yan Feng1, and Ji-Hong Liu3
1Department of Radiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, wuhan, hubei, China, 2Siemens Healthcare, Shanghai, China, 3Department of Urology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, wuhan, hubei, China

In this study, we investigate the use of readout-segmented echo planar imaging(rs-EPI) for diffusion imaging of the prostate. This result show the rs-EPI sequence will be less affected by both chemical shift and magnetic susceptibility resulting in higher quality images.

4459.   48 Effects of duration of the diffusion-encoding gradient (lower case Greek delta) and/or diffusion time interval (Capital Greek Delta) in diffusion weighted MRI: assessing ADC and Kurtosis in human brain
Shohei Miyazaki1, Masato Uchikoshi2, Thorsten Feiweier3, Andre de Oliveira3, Souichirou Tateishi1, Hitoshi Matsui1, Takashi Horinouchi1, and Katsuyuki Nakanishi1
1Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Osaka, Japan, 2SIEMENS JAPAN K.K., Tokyo, Japan, 3SIEMENS AG, Erlangen, Germany

We evaluated the effect of duration of the diffusion-encoding gradient (ƒÂ) and/or diffusion time interval (ƒ¢) in DW-MRI. DW-MRI were performed with various ƒÂ or ƒ¢ in healthy volunteers and patients with metastatic brain tumor, and the ADC and kurtosis were estimated. In our results, the kurtosis was affected by ƒ¢ more significant than ƒÂ, whereas there was no significant change in ADC against to both of ƒÂ and ƒ¢. Our results suggested that it might be important to optimize the ƒ¢, leading usefulness in clinical diagnosis and assessment of the treatment effect of brain disease using kurtosis.


Diffusion Analysis

Wednesday 14 May 2014
Exhibition Hall  13:30 - 14:30

  Computer #  
4460.   49 The importance of correcting for B0-drift-induced global signal decrease in diffusion MRI
Sjoerd B. Vos1, Chantal M.W. Tax1, Fredy Visser2, Peter R. Luijten2, Alexander Leemans1, and Martijn Froeling2
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, 2Department of Radiology, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands

B0-drift-induced global signal decrease in DWI data causes a significant influence on the estimation of diffusion parameters. Quantitative diffusion metrics (FA and mean kurtosis) as well as directional information (first eigenvectors in DTI) are affected by this artifactual signal decrease during the scan session. By interspersing the non-diffusion-weighted images throughout the session, the signal decrease can be estimated and compensated before processing, minimizing the detrimental effects on all further analyses.

50 Correction of Off-resonance Distortions in In-vivo Cardiac Diffusion Tensor Imaging
Jack Harmer1, Rachel W Chan2, Christian T Stoeck3, Constantin V Deuster3, David Atkinson2, and Sebastian Kozerke1,3
1Division of Imaging Sciences & Biomedical Engineering, King's College London, London, United Kingdom, 2Centre for Medical Imaging, University College London, London, Greater London, United Kingdom, 3Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

Advances in diffusion acquisition schemes employing stimulated echo modes now allow diffusion tensor imaging of the beating heart. However these pulse sequences almost invariably use single shot EPI readout modules that are extremely sensitive to magnetic field inhomogeneities. We demonstrate the feasibility of acquiring fully sampled single-shot in-vivo cardiac DTI data at 3T, in order to maximise SNR, by employing off-resonance correction as part of the reconstruction process. We demonstrate that such correction can be used to accurately reconstruct the correct geometry in areas of severe geometric distortion and signal pileup, whilst still allowing diffusion tensors to be reconstructed.

4462.   51 Comparison of extended Point Spread Function and Reverse Gradient Polarity distortion corrections in quantification of DW EPI at UHF
Oleg Posnansky1, Myung-Ho In1, and Oliver Speck1
1Department of Biomedical Magnetic Resonance, Institute of Experimental Physics, Otto-von-Guericke University, Magdeburg, Germany

In this study, we compare fractional anisotropy (FA) maps and DT (diffusion tensor) fiber tracks built after application of extended PSF, and Reverse Gradient Polarity distortion correction methods. The results demonstrate that the extended PSF method is very efficient for the correction of distortions in both DW-EPI data with opposite PE polarity, and thus it unveils properly positioned and fully recovered fine anatomical structures in the brain FA maps and fiber tracks. Due to its high accuracy extended PSF provides overwhelming correspondence between anatomy and connectivity of the tissue.

4463.   52 Higher order correction of eddy current distortion in diffusion weighted echo planar images.
Alan Seth Barnett1,2, Elizabeth Hutchinson1,2, M Okan Irfanoglu1,2, and Carlo Pierpaoli1,2
1NICHD, NIH, Bethesda, Maryland, United States, 2CNRM, USUHS, Bethesda, MD, United States

Higher order correction is sometimes required for adequate correction of eddy current induced distortion of diffusion weighted MR Images. The work consists of a description of the correction method and an example of a data set that requires cubic correction.

4464.   53 A method to combine multi NEX diffusion weighted images using Homomorphic filter
Sangwoo Lee1, Mitsuhiro Bekku2, Jeong Min Lee3, Jeong Hee Yoon3, Yuji Iwadate4, and Hiroyuki Kabasawa4
1Global MR Applications and Workflow, GE Healthcare, Seoul, Korea, 2MR Engineering, GE Healthcare, Hino-shi, Tokyo, Japan, 3Seoul National University Hospital, Seoul, Korea, 4Global MR Applications and Workflow, Hino-shi, Tokyo, Japan

Tissue movements from respiration, cardiac, and peristaltic motion during diffusion gradient can cause signal loss, which often leads to local overestimation of ADC map. To reduce motion induced signal loss, maximum intensity projection, weighted averaging or weighted multiplication methods have been proposed. These post processing methods are simple and efficient; however the final images cannot achieve pixel intensities higher than acquired raw images. To overcome such limitation, we propose a new image combining method with homomorphic filtering (H-MSW) and show the feasibility of the proposed via simulation and in vivo experiment.

4465.   54 Total Variation-Regularized Compressed Sensing Reconstruction for Multi-shell Diffusion Kurtosis Imaging
Jonathan I. Sperl1, Tim Sprenger1,2, Ek T. Tan3, Vladimir Golkov1,4, Marion I. Menzel1, Christopher J. Hardy3, and Luca Marinelli3
1GE Global Research, Munich, BY, Germany, 2IMETUM, Technical University Munich, Munich, BY, Germany, 3GE Global Research, Niskayuna, NY, United States, 4Computer Vision Group, Technical University Munich, Munich, BY, Germany

In Diffusion Kurtosis Imaging (DKI) the data is sampled in a series of concentric shells in the diffusion encoding space (q-space). This work proposes to randomly undersample this multi-shell data in q-space (i.e. to acquire fewer data points) and to exploit the 1D Fourier relation between single rays in q-space and in the reciprocal propagator space in order to reconstruct the missing points based on the principles of compressed sensing using a non-cartesian total variation regularization. The benefits of this approach in terms of stability and accuracy of the kurtosis tensor estimation are shown for a volunteer diffusion MR data set using undersampling factors up to R=2.

4466.   55 Model-based DTI reconstruction with sparsity constraints on the diffusion tensor
Florian Knoll1, Jos'e G Raya1, Rafael O Halloran2, Steven Beate1, Eric Sigmund1, Roland Bammer2, Tobias Block1, Ricardo Otazo1, and Daniel K Sodickson1
1Bernard & Irene Schwartz Center for Biomedical Imaging, Department of Radiology, NYU School of Medicine, New York, New York, United States,2Radiology, Stanford University, Stanford, California, United States

DTI allows to obtain quantitative measurements of tissue microstructure that no other technique can reveal. A simple and well defined signal model exists for DTI, which makes it an ideal candidate for model-based methods. The goal of this study is to introduce a new combination of compressed sensing and model based reconstruction where the sparsifying transform is evaluated directly in the domain of the diffusion tensor. Experimental results for truly accelerated in-vivo imaging are shown for both brain an MSK applications which demonstrate excellent performance of the model based approach.

4467.   56 Low Rank SENSE: A Robust Reconstruction Method for ms-EPI based high spatial resolution DWI
Feng Huang1, Zhe Zhang2, Randy Duensing1, Bida Zhang3, and Hua Guo2
1Philips Healthcare, Gainesville, FL, United States, 2Center for Biomedical Imaging Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China, 3Philips Research China, Beijing, China

Multi-shot EPI has been proposed for high spatial resolution DWI. Due to inter-shot motion, there are phase inconsistency among shots. Unlike the existing reconstruction methods for ms-EPI, we treat this ms-EPI as accelerated dyanmic imaging. Instead of correcting the phase difference, we use the low-rank property of the data set and parallel imaging to reconstruct the images of each shot. Experiments demonstrate that the proposed method can robustly reconstruct high quality DWI with up to 8-shot data set acquired by an 8-channel head coil.

4468.   57 CSF contamination contributes to apparent microstructural alterations in amnestic Mild Cognitive Impairment
Rok Berlot1,2, Claudia Metzler-Baddeley3, Derek K Jones3, and Michael J O'Sullivan1
1Department of Clinical Neuroscience, Institute of Psychiatry, King's College London, London, United Kingdom, 2Department of Neurology, University Medical Centre Ljubljana, Ljubljana, Slovenia, 3Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, and the Neuroscience and Mental Health Research Institute, Cardiff University, Cardiff, United Kingdom

Partial volume effects due to cerebrospinal-fluid contamination (CSFC) lead to artefacts in diffusion MRI studies in populations prone to atrophy. We explored the influence of CSFC on apparent microstructural differences in amnestic mild cognitive impairment (MCI). A post-acquisition method of Free Water Elimination was used to correct for CSFC. Comparisons between controls and MCI were performed at several spatial levels in uncorrected and corrected data. CSFC shifted the pattern of involvement of individual temporal association tracts. Tract-based spatial statistics were robust to CSFC with notable localised exceptions. A proportion of group difference in mean histogram metrics was driven by CSFC.

4469.   58 Parametric representation, variability analysis and atlas construction of the mouse myocardial fiber structure
Samer Sarfaraz Merchant1, Arnold David Gomez1, and Edward Hsu2
1BioEngineering, University of Utah, Salt Lake City, Utah, United States, 2University of Utah, BioEngineering, Salt Lake City, Utah, United States

Myofiber atlases have been constructed from cardiac DTI datasets using voxel-based statistics, which is prone to noise and omits obvious functional and structural interconnectivities of the organ. In the current work, parametric modeling and principal component analysis were performed to characterize and investigate the variability of myofiber structure in a group of 6 mouse hearts. Results show that the hearts can be well represented by a 16-term parametric function in prolate spheroidal space, and majority of the heart-to-heart variability exists concentrically in the transmural dimension. These findings are valuable for design and interpretation of DTI cardiac structural measurement and modeling.

4470.   59 Evaluation of Diffusion Spectrum Imaging Reconstruction with Trained Dictionaries use of 3T MR
Ping-Hong Yeh1, Namgyun Lee2, John Morissette3, Arman A. Taheri3, Li-Wei Kuo4, Fang-Cheng Yeh5, Erick Jorge Canales- Rodríguez6, Wei Lui3, John Ollinger3, Terrence Oakes3, Mark L. Ettenhofer7, and Gerard Riedy3
1Henry Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, United States, 2Korea Basic Science Institute, Korea, 3National Capital Neuroimaging Consortium, Bethesda, MD, United States, 4National Health Research Institutes, Taiwan, 5Carnegie Mellon University, PA, United States, 6FIDMAG Research Foundation, Germanes Hospitalaries and CIBERSAM, Barcelona, Spain, 77Uniformed Services University of the Health Sciences, MD, United States

Recent work using Compressed Sensing (CS) reconstruction shows promising in greatly reducing diffusion spectrum imaging (DSI) scan time without jeopardizing critical image information. We evaluate the performance of CS reconstruction using dictionary-based training coupled with the Focal Underdetermined System Solver (FOCUSS) algorithm and L2 regularization on undersampled human brain DSI data acquired by a clinical 3T MR scanner within an acceptable time frame (< 20 minutes).

4471.   60 Semi-Joint Reconstruction for Diffusion MRI Denoising Imposing Similarity of Edges in Similar Diffusion-Weighted Images
Vladimir Golkov1,2, Marion I. Menzel1, Tim Sprenger1,3, Axel Haase3, Daniel Cremers2, and Jonathan I. Sperl1
1Diagnostics & Biomedical Technologies - Europe, GE Global Research, Garching n. Munich, Germany, 2Department of Computer Science, Technische Universität München, Garching n. Munich, Germany, 3Institute of Medical Engineering, Technische Universität München, Garching n. Munich, Germany

Recently, Joint Reconstruction has been proposed by Haldar et al. for SNR enhancement of diffusion-weighted images (DWIs), performing edge-preserving denoising by imposing identical edge constraints to all DWIs. In this work, we propose Semi-Joint Reconstruction to allow individual edges for each DWI in order to account for the fact that distinct DWIs can look quite dissimilarly, whereas similar DWIs contain common edge structures. Individual edge maps necessitate edge map denoising, for which we use DWI similarity weightings, truncated singular value decomposition of DWIs, and shearlet-based edge detectors. Results are comparable to Joint Reconstruction, but more stable to regularization parameter choice.

4472.   61 Direct Reconstruction of the Average Diffusion Propagator with Simultaneous Compressed-Sensing-Accelerated Diffusion Spectrum Imaging and Image Denoising by Means of Total Generalized Variation Regularization
Vladimir Golkov1,2, Marion I. Menzel1, Tim Sprenger1,3, Mohamed Souiai2, Axel Haase3, Daniel Cremers2, and Jonathan I. Sperl1
1Diagnostics & Biomedical Technologies - Europe, GE Global Research, Garching n. Munich, Germany, 2Department of Computer Science, Technische Universität München, Garching n. Munich, Germany, 3Institute of Medical Engineering, Technische Universität München, Garching n. Munich, Germany

Reconstruction of diffusion-weighted images (DWIs) in diffusion MRI is usually done independently for each DWI, without exploiting structural correlations between the DWIs. In this work, we propose direct reconstruction of the average diffusion propagator (directly from k-space data), taking advantage of the DWIs being linked together via their Fourier relationship with the average propagator space, while regularization using five-dimensional total generalized variation (TGV) along both image space and diffusion space is applied. The results demonstrate the ability of the method to reconstruct q-space-undersampled data in a compressed sensing framework, simultaneously denoising the data.

4473.   62 A Novel Post-processing Procedure to Sharpen the ODFs of Different HARDI Datasets by Using Super-CSD
Shiou-Ping Lee1, Chung-Ming Chen2, Li-Chun Hsieh1, Wing-Keung Cheung1, Yu-Chiang Chen1, and Ming-Chung Chou3
1Department of Medical imaging, Far Eastern Memorial hospital, Banqiao, New Taipei city, Taiwan, 2Insitute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, 3Department of Medical Imaging and Radiological Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan

Recently, there were a variety of algorithms proposed to reconstruct orientation distribution function based on high angular resolution diffusion imaging data in order to resolve multiple fiber orientations. However, it was found that some fiber orientations were likely lost when fibers intersected at a small angle. A previous study performed the super resolved - constrained spherical deconvolution to resolve multiple fiber orientations crossing at a smaller angle, but the method was only suitable for diffusion-weighted datasets acquired in a spherical coordinate, such as q-ball imaging. Other HARDI datasets, such as diffusion spectrum imaging, acquired in a Cartestian coordinate whose fiber orientation distribution could not be obtained by using super-CSD. Hence, the purpose of this study is to propose a post-processing procedure which is suitable for sharpening ODFs of different HARDI datasets and resolving multiple fiber orientations by using super-CSD.

4474.   63 3D locally dependent regularization of the diffusion tensor using ICA and TGV
Gernot Reishofer1, Kristian Bredies2, Karl Koschutnig3, Margit Jehna4, Christian Langkammer5, David Porter6, and Hannes Deutschmann4
1Radiology, Medical University of Graz, Graz, Styria, Austria, 2Institute for Mathematics and Scientific Computing, Universtiy of Graz, Austria,3Psychology, Universtiy of Graz, Austria, 4Neuroradiology, Medical University of Graz, Austria, 5Neurology, Medical University of Graz, Austria, 6Siemens AG, Healthcare Sector, MR R&D, Germany

It has been shown recently, that spatially dependent regularization of the diffusion tensor applied on readout-segmented echo planar imaging (rs-EPI) with 2D navigator-based reacquisition significantly improves fractional anisotropy (FA) maps and tractography. In this work we propose a novel approach for automatic regularizing the entire diffusion tensor utilizing a three dimensional implementation of total generalized variation (TGV). The evaluation of the noise distribution of the diffusion tensor by means of ICA allows for an automatic update of the regularization parameter making the proposed algorithm user-independent. Furthermore the incorporation of the locally varying noise distribution allows for a spatially dependent regularization.

4475.   64 Human Brain Intravoxel Incoherent Motion (IVIM) : Optimized set-up for clinical investigation
Alberto Ciarmatori1,2, Elisa Cenacchi1, Tiziana Costi1, and Luca Nocetti1
1Medical Physics Department, University Hospital "Policlinico", Modena, Italy, 2Medical Physics School, University "Alma Mater Studiorum", Bologna, Italy

This study focused on separation of vascular and non-vascular component of DWI signal decay. Brain scans were performed using a 3T whole body MR on six healthy volunteers. DWIs with multiple b-values (0-5-10-20-30-40-50-75-100-150-200-300-500-1000 s/mm2) were obtained. Datas were fitted with a biexponential function with Diffusion Coefficient and Perfusion Fraction obtained from high-b (>250 s/mm2) monoexponential fit. A temporal optimized (6 min) sequence was found . Significative differences were observed D and standard ADC as well as between gray matter and white matter diffusion parameters. In particular D* of gray matter resulted significantly greater than in white matter.

4476.   65 Combining Multi-Centre Conventional and Diffusion MR Texture for the Characterisation of Childhood Brain Tumours
S. Tantisatirapong1, N. P. Davies1,2, D. Rodriguez3, L. Abernethy4, D. P. Auer3,5, C. A. Clark6,7, R. Grundy3,5, T. Jaspan5, D. Hargrave7, L. MacPherson2, M. O. Leach8, G. S. Payne8, B. L. Pizer4, S. Bailey9, A. C. Peet1,10, and T. N. Arvanitis10,11
1University of Birmingham, Edgbaston, Birmingham, United Kingdom, 2University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom, 3University of Nottingham, Nottingham, United Kingdom, 4Alder Hey Children’s NHS Foundation Trust, Liverpool, United Kingdom, 5University Hospital Nottingham, Nottingham, United Kingdom, 6University College London, London, United Kingdom, 7Great Ormond Street Hospital, London, United Kingdom, 8The Institute of Cancer Research and Royal Marsden Hospital, Sutton, United Kingdom, 9Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, United Kingdom, 10Birmingham Children’s Hospital NHS Foundation Trust, Birmingham, United Kingdom, 11Institute of Digital Healthcare, WMG, University of Warwick, Coventry, United Kingdom

This paper presents integration of multimodal MR image based texture analysis which take advantage of complementary information derived from structural and diffusion MR images. A supervised machine learning approach is used to achieve image analysis based on textural features from individual image types of T2, T1-post contrast and ADC, as well their combination, in order to characterize the multicenter dataset of the most common pediatric brain tumors; medulloblastomas (MB), pilocytic astrocytomas (PA), and ependymomas (EP).

4477.   66 Combined Segmentation and Sequential Registration Method for Artifact Removal in ADC maps in Liver
Harini Veeraraghavan1, Joseph O. Deasy1, and Richard K.G. Do1
1Memorial Sloan Kettering Cancer Center, New York, New York, United States

Bulk motion artifacts adversely impact the reproducible measurement of ADCs in the liver. We present a combined segmentation and sequential registration to align multi b-valued DWI images that removes artifacts and computes repeatable ADC mappings. Our approach uses the automatic volumetric segmentation of structures of interest (tumor) with a sequential registration such that the artifacts are most removed around those structures. Evaluation over multiple trials with introduced motion on 14 patients show that our approach results in least artifacts and lowest standard deviation of mean ADC in the tumors compared to either no registration or simultaneous affine registration.

4478.   67 Segmentation of renal structures in distortion corrected diffusion-weighted echo-planar images based on anatomical FSE and GRE images
Susanne Will1, Petros Martirosian1, Christina Schraml1,2, Bernd Kardatzki3, Michael Erb3, Günter Steidle1, and Fritz Schick1
1Department of Diagnostic and Interventional Radiology, University of Tuebingen, Tuebingen, Germany, 2Section on Experimental Radiology, University of Tuebingen, Germany, 3Department of Biomedical Magnetic Resonance, University of Tuebingen, Germany

Classification of anatomical renal structures in diffusion-weighted echo-planar images may be difficult to perform. For this reason a simple transfer of segmented areas from high-resolution FSE/GRE images with suitable visualization of the anatomy to DTI images would be helpful but is hampered by geometric distortions. The purpose of this study was to assess the feasibility of renal segmentation and their internal structures in distortion corrected DTI images. Six volunteers were examined at 3T. It was found that DTI values can be accurately determined in specific areas of distortion corrected images by manual renal segmentation in corresponding high-resolution anatomical images.

4479.   68 Comparison of the accuracy between manual and computerized anatomical delineation techniques in ex-vivo diffusion tensor imaging of the mouse brain.
Hedok Lee1,2, Joe Cavallo1, Vivek Goyal1, Sagar Dhandia1, Michael Cutrone1, Elyssa Chen1, Tian Fang1, Helene Benveniste1,2, and Thomas Floyd1,2
1Anesthesiology, State University of New York at Stony Brook, Stony Brook, New York, United States, 2Radiology, State University of New York at Stony Brook, Stony Brook, New York, United States

In this study we compared manual and semi-automated computerized anatomical delineation techniques in ex-vivo diffusion tensor imaging of the mouse brain. The accuracy of both FAs and anatomical volumes in the computerized technique was comparable or just below the discrepancies caused by subjective bias between the two raters. We conclude that the computerized method is effective and time efficient method in analyzing FA and anatomical volumes.

4480.   69 A GPU-based parallel computing framework for accelerating graph theoretical analyses
Tsang-Chu Yu1, Yi-Ping Chao1, Li-Wei Kuo2, Chung-Chih Lin1, Shih-Yen Lin2,3, Hengtai Jan2, Claudia Metzler-Baddeley4, and Derek Jones4
1Department of Computer Science and Information Engineering, Chang Gung University, Taoyuan, Taiwan, 2Institute of Biomedical Engineering and Nanomedicine, National Health Research Institutes, Miaoli, Taiwan, 3Department of Computer Science, National Chiao Tung University, Hsinchu, Taiwan,4School of Psychology, Cardiff University, Cardiff, United Kingdom

The main purpose of this study is to develop a graphics processing unit based framework for brain network analysis that permit networks comprising much larger numbers of nodes and provide the acceleration for processing. From the results, our implementation for the calculation of all pair shortest paths could reduce half of time with brain connectivity toolbox (BCT) and 638x speedup with Gretna in simulation random network with larger number of nodes (>8k). Moreover, our algorithm also shows better performance in human brain data with 1.37x and 21x speedup in comparison with BCT and Gretna respectively.

4481.   70 A New Algorithm to Estimate the Mean of A Group of Tract Bundles
Hsu Yung-Chin1 and Tseng Isaac Wen-Yih1,2
1Center for Optoelectronic Medicine, College of Medicine, National Taiwan University, Taipei, Taipei, Taiwan, 2Graduate Institute of Brain and Mind Sciences, College of Medicine, National Taiwan University, Taipei, Taiwan

In the study, we propose a new algorithm to iteratively estimate the mean shape of a group of tract bundles. The basic idea of our algorithm is: performing registration on tract bundles and taking the average on orientation maps. The conversion from orientation maps to tract bundles is achieved via fiber-tracking algorithms, and the reverse way is via modeling the tract bundles as currents. The algorithm is demonstrated on ten right cingulum bundles, and the results show that this method could properly estimate the mean cingulum bundle. This method has the potential to facilitate computational anatomy of the brain.

4482.   71 Moderate protein content does not influence on DWI-thermometry: Temperature-controlled Artificial CSF phantom study
Koji Sakai1, Ryusuke Nakai1, Kei Yamada2, Jun Tazoe2, Kentaro Aakazawa2, and Naozo Sugimoto1
1Kyoto University, Kyoto, Kyoto, Japan, 2Kyoto Prefectural University of Medicine, Kyoto, Japan

Among MR thermometry, the most clinically applicable may be the post processing of diffusion-weighted images (DWI). However, this DWI-based method might be influenced by the composition of CSF, which can strongly affect its viscosity and diffusivity. The purpose of this study was to investigate the influence of protein content on DWI thermometry by using temperature-controlled artificial CSF (ACSF). The results of DWI thermometry were not influenced by the protein content in the range of 0.0 to 8.01 mg/ml (approximately 40 times protein content of normal adult) at near body temperature.

4483.   72 Reliable Analysis of Tract-specific Multiparametric MR Data via Automated Isolation of Nigro-Striatal Tract
Ryan Hutten1, Nisa Desai1, Demetrius Maraganore2,3, Robert R. Edelman1,4, and Ying Wu1,5
1Radiology, Northshore University Health System, Evanston, IL, United States, 2Neurology, Northshore University Health System, IL, United States,3Neurology, University of Chicago, IL, United States, 4Radiology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States,5Radiology, University of Chicago, Chicago, IL, United States

Automated tract based diffusion tensor imaging (DTI) and magnetization transfer ratio (MTR) of the nigro-striatal tract (NST) represents a high innovative neuroimaging approach in Parkinson’s disease. The NST is a major dopamine pathway that is critically involved in Parkinson’s Disease (PD) diagnosis and treatment modulation. The development of the automated NST overcomes the challenges associated with segmenting SN, and the necessity of manual seed regions for tractography. We demonstrate considerably improved reliability that eliminates operator-induced error that will benefit future longitudinal studies of Parkinson's disease.


Diffusion Models

Wednesday 14 May 2014
Exhibition Hall  14:30 - 15:30

  Computer #  
4484.   1 New Insights into Rabbit Brain Development with Generalized Q-Sampling MRI
Fang-Yu Nien1, Seong Yong Lim1, Yu-Han Hong1, Ya-Han Chang1, and Jun-Cheng Weng1,2
1School of Medical Imaging and Radiological Sciences, Chung Shan Medical University, Taichung, Taiwan, 2Department of Medical Imaging, Chung Shan Medical University Hospital, Taichung, Taiwan

Characterizing complex anatomy at different stages of brain development not only aids in understanding this highly ordered process but also provides clues to detect abnormalities caused by genetic or environmental factors. Diffusion MRI allows for the in vivo delineation of white matter tracts in the brain in a manner that is individualized to the particular neuroanatomy of each subject. Diffusion anisotropy and diffusivity change in some brain regions with demyelinating disease and also with neural development. Previously we used diffusion tensor imaging (DTI) to detect the changes of white matter tracts of rabbit during brain development. However, DTI suffers from resolving the complicated neural structure, i.e. fiber crossing, which is observed frequently during mature period. Therefore the goal of this study was to characterize the changes of quantitative diffusion indices in the developing rabbit brains using generalized q-sampling imaging (GQI).

4485.   2 Transforming grids to shells and vice versa: an evaluation of interpolation methods in diffusion MRI q- and b-space
Chantal M.W. Tax1, Sjoerd B. Vos1, Max A. Viergever1, Martijn Froeling2, and Alexander Leemans1
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, 2Department of Radiology, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands

Interpolation in q- or b-space can be used to convert between different sampling patterns (e.g. from multi shell to grid as in hybrid diffusion imaging) to be able to compare between diffusion MRI reconstruction methods, or to detect and correct for artifacts, amongst others. In this work we perform a comparison between different interpolation methods (i.e. nearest neighbor, linear, cubic and model based) in q- and b-space, on simulated data.

4486.   3 Two-component Low Q-space Diffusion MRI in Evaluation of Spinal Cord in Patients with Cervical Spondylosis in Vivo: a Feasibility Study -permission withheld
Masaaki Hori1, Koji Kamagata1, Mariko Yoshida1, Nozomi Hamasaki2, Shuji Sato2, Kouhei Kamiya1,3, Yuriko Suzuki4, Michimasa Suzuki1, and Shigeki Aoki1
1Radiology, Juntendo University School of Medicine, Tokyo, Japan, 2Juntendo University Hospital, Tokyo, Japan, 3Radiology, The University of Tokyo, Tokyo, Japan, 4Philips Electronics Japan, Ltd, Tokyo, Japan

We investigate two-component low q-space diffusion MRI in evaluation of microstructural changes in the spinal cord in patients with cervical spondylosis in vivo, as a feasibility study. Five patients were enrolled in this study. There were significant differences in root mean square displacement of water molecules in extra- and intra- cellular spaces between compressed and uncompressed area in the spinal cords. More studies of the imaging pathological correlation and improvement of image quality are needed; this technique has the potential to provide new information in patients with spinal cord in vivo.

4487.   4 Rotation-invariant measures for population study in HARDI
Emmanuel Caruyer1 and Ragini Verma1
1Section of Biomedical Image Analysis, Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States

We present a novel family of rotational-invariant measures for High Angular Resolution Diffusion Imaging1 (HARDI) data. This research is motivated by need for the developing new biomarkers and thereby facilitating population-based studies in HARDI. From a spherical harmonics (SH) representation of the angular information in diffusion MRI, we derive 12 rotational-invariant measures computed as homogeneous polynomials of the SH coefficients. These measures are expected to be sensitive to subtle changes in white matter structure, not captured by FA or GFA. The large number of measures will be used to create population classifiers, paving the way for pathology-specific biomarkers.

4488.   5 Optimization of a Fast Diffusion Estimation Two-Compartment Model for Diffusion Tensor Imaging
Andrew R. Hoy1,2, Chen Guan Koay1, Steven R. Kecskemeti2,3, and Andrew L. Alexander1,2
1Medical Physics, University of Wisconsin, Madison, Wisconsin, United States, 2Waisman Laboratory for Brain Imaging and Behavior, Madison, Wisconsin, United States, 3Radiology, University of Wisconsin, Madison, Wisconsin, United States

Diffusion tensor imaging yields information about tissue microstructure. However, when a single voxel contains tissue and free water, DTI is not appropriate. A two-tensor fast diffusion estimation model has been proposed to correct this shortcoming. This model was implemented in a novel manner, and the acquisition parameters optimized through Monte Carlo simulations. The optimal acquisition with 68 diffusion-weighted encoded images had three diffusion-weighted shells (b-value in s/mm2 x number of directions) of 200x12, 650x40, 1500x12. This was confirmed in vivo. The model is useful for tissues adjacent to CSF and removing artifacts from CSF blurring and ghosting.

4489.   6 High Resolution Diffusion Imaging of the Brain Stem for Non-Gaussian Diffusion Analysis at High b-Values
Yi Sui1,2, Frederick C. Damen1,3, and Xiaohong Joe Zhou1,4
1Center for MR Research, University of Illinois at Chicago, Chicago, Illinois, United States, 2Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States, 3Department of Radiology, University of Illinois Hospital & Health Sciences System, Chicago, Illinois, United States,4Departments of Radiology, Neurosurgery and Bioengineering, University of Illinois Hospital & Health Sciences System, Chicago, Illinois, United States

An integrated high-resolution, multi-b-value diffusion acquisition approach has been developed with reduced FOV and phase-sensitive signal averaging. Using this approach, distortion-free brain stem diffusion images with an in-plane resolution of ~0.6×0.6 mm2 have been obtained at b-values up to 4000 s/mm2 and successfully fitted to a non-Gaussian diffusion model (Fractional Order Calculus model). This study demonstrates the potential for extending the applications of high b-value non-Gaussian diffusion models to fine brain structures.

4490.   7 Experimentally estimated non-Gaussian water diffusion at a large range of b-values
Louise Munk Rydtoft1, Brian Hansen1, Mikkel Bo Hansen1, and Sune Nørhøj Jespersen1,2
1CFIN / MindLab, Aarhus university, Aarhus, Denmark, 2Department of physics and astronomy, Aarhus University, Denmark

Conventionally DTI is deemed accurate for b-values below 1000 s/mm2 and DKI for b-values below 2000 s/mm2. By analysing DKI and DTI fits on data from a human volunteer and perfusion fixated rat, we show the DKI model is a better fit for a linearly increasing ratio of voxels, independent on tissue type. Up to one-third of voxels are better fitted by DKI when maximum b-value is 1000 s/mm2. DKI is a convincing alternative to DTI, even at smaller b-values that has generally been accepted. Also, we show that the fixation process indeed restricts diffusion; this is disputed in the literature.

4491.   8 Analysis of the cumulant expansion terms of the diffusion-weighted MRI signal in the human brain -permission withheld
Ezequiel Farrher1, Farida Grinberg1,2, Ivan I. Maximov1, and N. Jon Shah1,2
1INM - 4, Research Centre Jülich GmbH, Jülich, Germany, 2Department of Neurology, RWTH Aachen University, Aachen, Germany

Diffusion kurtosis imaging has become an important extension to diffusion tensor imaging in the quantification of non-Gaussian diffusion by means of magnetic resonance imaging. However, there is still no general consensus on the optimal range of b-values for data analysis. In this work we perform an investigation on the dependence of the cumulant expansion terms of the diffusion-weighted MRI signal on the fitting b-value range. The present analysis gives important insights into the validity of the fitting b-value range in DKI analysis.

4492.   9 Improving fiber orientation estimation in constrained spherical deconvolution under non-white matter partial volume effects
Timo Roine1, Ben Jeurissen1, Wilfried Philips2, Alexander Leemans3, and Jan Sijbers1
1iMinds-Vision Lab, University of Antwerp, Antwerp, Flanders, Belgium, 2Department of Telecommunications and Information Processing, University of Ghent, Ghent, Flanders, Belgium, 3Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands

Diffusion-weighted magnetic resonance imaging is prone to large partial volume effects (PVEs) due to its large voxel size. In this work, we studied the PVEs with non-white matter (WM) tissue on estimation of the fiber orientation distribution function (fODF) with constrained spherical deconvolution (CSD). We found a loss of precision in the detected fiber orientations and an emergence of a high number of false orientations in the fODF. The effects were most significant with gray matter (GM) partial volume. We propose a modification to CSD to further improve the estimation of the fODF especially near the WM-GM interface.

4493.   10 A Combined Analysis of the Non-Gaussian Diffusion Methods in Monte Carlo Simulations, Anisotropic Fibre Phantoms, and in in vivo Human Brain Tissues
Farida A Grinberg1, Ezequiel Farrher1, Ivan I Maximov1, and N. Jon Shah1,2
1INM-4, Forschungszentrum Juelich, Juelich, Germany, 2Department of Neurology, RWTH Aachen University, Aachen, Germany

This work provides a comparative analysis of the four non-monoexponential functions in fitting the diffusion response in a) the Monte Carlo diffusion simulations in a set of cylindrical objects, b) synthetic fibre phantoms with parallel and crossing fibres, and c) in vivo human brain tissue. All functions including the diffusion kurtosis, stretched-exponential, the lognormal- and gamma-distribution functions were shown to provide complimentary information and different contrasts in parameter maps.

4494.   11 Altered Global and Regional Brain Mean Kurtosis in Recently-Diagnosed Patients with Obstructive Sleep Apnea -permission withheld
Rajesh Kumar1, Santosh K Yadav1, Jennifer A Ogren2, Mary A Woo2, Daniel W Kang3, Paul M Macey2, Frisca L Yan-Go4, and Ronald M Harper5
1Anesthesiology, University of California at Los Angeles, Los Angeles, CA, United States, 2UCLA School of Nursing, University of California at Los Angeles, Los Angeles, CA, United States, 3Medicine, University of California at Los Angeles, Los Angeles, CA, United States, 4Neurology, University of California at Los Angeles, Los Angeles, CA, United States, 5Neurobiology, University of California at Los Angeles, Los Angeles, CA, United States

Obstructive sleep apnea (OSA) patients show structural injury and functional deficits in multiple brain areas, based on various MRI techniques, in sites that regulate autonomic, motor, cognitive, and mood functions, deficient in the condition. However, the nature of tissue injury remains unclear. We examined global and regional mean kurtosis values in newly-diagnosed, treatment-naive OSA patients, and found increased global values in critical autonomic, cognitive, motor, and respiratory control sites, including the insular cortices, cerebellum, and basal-ganglia. The pathological mechanisms contributing to tissue injury likely include hypoxemia-induced processes, leading to acute tissue changes in OSA.

4495.   12 Demonstration of fast diffusion kurtosis MRI for imaging acute ischemic stroke diffusion/kurtosis lesion mismatch -permission withheld
Phillip Zhe Sun1, Yu Wang1,2, Emiri Mandeville3, Eng H Lo3, and Xunming Ji2
1Radiology, Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 2Cerebrovascular Diseases Research Institute, Xuanwu Hospital of Capital Medical University, Beijing, China, 3Department of Radiology and Neurology, Neuroprotection Research Laboratory, MA, United States

Diffusion kurtosis MRI (DKI) is a complementary index to stratify heterogeneous DWI deficit. However, DKI acquisition time is relatively long. Here, we tested a fast DKI approach, recently proposed by Hansen et al., using a rodent model of acute stroke. We found significant correlation, per pixel, between the diffusion and kurtosis coefficients measured using the standard and fast DKI protocols. We further demonstrated that diffusion and kurtosis lesion sizes defined using the fast and conventional DKI methods were in good agreement. Moreover, we showed that kurtosis lesion size was significantly smaller than that of diffusion lesions (72±16%, P<0.01, Paired-t test).

4496.   13 Diffusional Kurtosis Imaging of White Matter and Gray Matter Lesions in Multiple Sclerosis: Combined Use with Double Inversion Recovery
Mariko Yoshida1, Masaaki Hori1, Kazumasa Yokoyama2, Nozomi Hamasaki1, Michimasa Suzuki1, Koji Kamagata1, Kohei Kamiya1, Shigeki Aoki1, Yoshitaka Masutani3, and Nobutaka Hattori2
1Department of Radiology, Juntendo University School of Medicine, Bunkyo, Tokyo, Japan, 2Department of Neurology, Juntendo University School of Medicine, Tokyo, Japan, 3Division of Radiology and Biomedical Engineering, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan

The purpose of this study is to evaluate diffusional changes of the WM and GM including plaques, periplaque WM (PWM), periplaque GM (PGM), NAWM, and NAGM in MS by using a new method\DKI with double inversion recovery (DIR) to segment GM. The participants were 7 MS patients with GM plaques. DKI with DIR detected abnormalities in WM and GM with high sensitivity and can provide additional information on changes of WM and GM in MS. In contrast to WM plaques, there may be little change in the GM substance around GM plaques. MK may be a more sensitive biomarker of tissue damage in MS patients.

4497.   14 Comparison of Fitting Methods and b value Sampling Strategies for Intravoxel Incoherent Motion (IVIM) in Breast Cancer
Gene Young Cho1, Jeff L Zhang2, Linda Moy1,3, Steven Baete1, Melanie Moccaldi3, Sungheon Kim1, Daniel K Sodickson1, and Eric E Sigmund1
1Radiology - Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, Select, United States,2Radiology, University of Utah, Salt Lake City, UT, United States, 3Radiology, New York University Cancer Institute, New York, NY, United States

The selection of diffusion gradients for diffusion weighted imaging (DWI) is important for protocol optimization. It has been shown that different ranges of gradients sensitize the signal to different components of diffusion. Additionally, quantification of DWI data with the biexponential IVIM fitting model can be numerically nontrivial. In this study, we employ an optimized b value selection for biexponential IVIM analysis of breast lesions to increase measurement precision. Eventually, optimization may lead to increasing diagnostic differentiation between cancerous subtypes and potentially allow more careful monitoring of response to treatment.

4498.   15 Effects of computation methods, median filtering and Rician noise removal on diffusional kurtosis and tensor imaging metrics in vivo
Masaaki Hori1,2, Yoshitaka Masutani3, Ryuji Nojiri2, Katsutoshi Murata4, Koji Kamagata1, Mariko Yoshida1, Michimasa Suzuki1, and Shigeki Aoki1
1Radiology, Juntendo University School of Medicine, Tokyo, Japan, 2Tokyo Medical Clinic, Tokyo, Japan, 3The University of Tokyo, Tokyo, Japan, 4Siemens Japan K.K., Tokyo, Japan

The purpose of this exhibit is to characterize, particularly for clinical use, the effects of computation methods, median filtering and Rician noise removal on diffusion tensor imaging (DTI) and diffusional kurtosis imaging (DKI) metrics in normal white matter and brain tumors. Median filtering is an important factor that affects quantitative diffusion metrics; for example, it changes fractional anisotropy (FA) values by 10%. Differences of computing methods and Rician noise removal appear to be less influential in changing diffusion metrics. Selection of post-processing methods should be clarified in research and clinical use.

4499.   16 Temporal change of bloody fluid with apparent diffusion coefficient and T1-/ T2-relaxation time in a phantom study. -permission withheld
Tomohiro Namimoto1, Kosuke Morita1, Yuuki Kizaki1, Toshinori Hirai1, Makoto Gotoh2, Yukimi Waki2, Ryo Itatani1, and Yasuyuki Yamashita1
1Diagnostic Radiology, Kumamoto University, Kumamoto, Kumamoto, Japan, 2Kumamoto University Hospital, Kumamoto, Japan

We compared apparent diffusion coefficients (ADCs) with T1-/T2-relaxation time in a phantom study. Blood phantoms were gradually diluted with saline. MR measurements were performed with T1-/T2-calculations and ADCs from 0.2 hour to 7 days. T1-relaxation time cumulatively increased and subsequently plateaued. T2-relaxation time increased, and then decreased. ADC slightly decreased during whole times. T1-relaxation time and ADC was almost proportional decreased as blood concentration decreased; T2-relaxation time was almost inversely proportional decreased. Temporary change of ADCin bloody fluid was poorly correlated with that of T1-/T2-relaxation time. ADC is almost linearly dependent on blood concentration and almost independent of T1-/T2-relaxation times.

4500.   17 Computing ADC for higher b-value using log-linear relationship between ADC and b-value
Prativa Sahoo1, Rakesh Kumar Gupta2, Indrajit Saha1, Bhaswati Roy2, Ram Krishna Singh Rathore3, and Divya Rathore4
1Philips Healthcare, Philips India Ltd, Gurgaon, Haryana, India, 2Radiology and Imaging, Fortis Memorial Research Institute, Gurgaon, Haryana, India,3Mathematics and Statistics, Indian Institute of Technology Kanpur, Kanpur, UP, India, 4ADISL India, Kanpur, UP, India

Diffusion weighted imaging (DWI) is a very sensitive imaging sequence for detecting various tissue abnormalities in brain. In clinical practice, b-values of 1000 sec/mm2 or less are commonly used; however it has been reported that use of higher b-values improves disease visualization and detection1. DWI imaging with higher b-values is challenging because it suffers with low signal to noise ratio (SNR), distortion along with longer scan time. To overcome these difficulties computed DWI technique has been proposed by many researchers 2. Computed DWI technique is a mathematical technique, which generates images of higher b-values by using at least two different lower b value (b ≤ 1000) images. Here we report that we have observed ADC depends on b-values, on contrary to the previous assumption where it was considered constant for all b-values and computation of ADC corresponding to higher b-values was not possible. The aim of this study was to find the relationship between ADC and b-values for quantification of ADC corresponding to higher b-values using lower b-values with computed DWI technique.

4501.   18 DTI fibre tracking: beyond the main eigenvector
Ivan I. Maximov1, Anton Minnekhanov1,2, Ezequiel Farrher1, Farida Grinberg1, and N. Jon Shah1,3
1INM-4, Forschungszentrum Juelich, Juelich, Germany, 2Department of Physics, Moscow State University, Moscow, Russian Federation, 3Department of Neurology, RWTH Aachen University, Aachen, Germany

Diffusion tensor imaging is a well-known and well-established imaging technique. It allows one to easily visualize the neuronal tissue architecture by using the eigenvector linked to the largest eigenvalue of the diffusion tensor. However, the diffusion tensor eigenvectors form a complete orthonormal basis in space and contain additional information. We hypothesize here that all three eigenvectors in the neuronal bundles can generate a structure similar to a crystal lattice and keep this configuration along the bundle with high anisotropy. Thus, vector fields based on secondary and/or tertiary eigenvectors could improve the segmentation/reconstruction of fibre tracts and provide additional information on white matter organisation.

4502.   19 Diffusion Tensor Imaging of Rat Brains Following Long-term Passive Acoustic Exposure at Moderate Sound Pressure Level
Condon Lau1, Sherwin Abdoli2, Leon C Ho3,4, Jevin W Zhang3,4, and Ed X Wu3,4
1Division of Biomedical Engineering, HKUST, Kowloon, Hong Kong, 2Keck School of Medicine, University of Southern California, CA, United States,3Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, Hong Kong, 4Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, Hong Kong

Diffusion tensor imaging was used to observe changes in the brain structure of rats (n=16) following two months of continuous and passive acoustic exposure at moderate sound pressure level. Voxel-based statistics (VBS) revealed greater fractional anisotropy of the pyramidal tract, tectospinal tract, intertwined trigeminothalamic tract and medial lemniscus of the exposed rats than of the control rats. ROIs were drawn for the structures indicated and applied to the fractional anisotropy and mean diffusivity maps. ROI analysis confirmed that in the structures indicated by VBS, fractional anisotropy was higher and mean diffusivity was lower in exposed rats than in normal rats.

4503.   20 Development of a hindered-diffusion-dominant DTI phantom made of polyethylene fibers: Comparison with a restricted-diffusion phantom.
Atsushi Tachibana1, Takayuki Obata1, Yasuhiko Tachibana1, Hiroshi Kawaguchi2, Jeff Kershaw2, Ichio Aoki2, Hiroshi Ito2, and Hiroshi Tsuji1
1Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba-shi, Chiba, Japan, 2Molecular Imaging Center, National Institute of Radiological Sciences, Chiba-shi, Chiba, Japan

This study investigates the diffusion characteristics of our newly developed DTI phantom made of bundled polyethylene fibers (Dyneema (Dy)), in comparison to a conventionally used glass made phantom with micro capillaries (capillary plates (CP)). Dy was less sensitive to diffusion time, implying that the water diffusion is hindered rather than restricted. Dy also had b-value dependent signal attenuation more similar to that in vivo tissue, and was much less expensive than CP. These suggest that Dy is a better phantom for DTI QC than CPs.

4504.   21 Examination of Tensor Estimation Methods for Cervical Spinal Cord DTI in Pediatric Subjects with Spinal Cord Injury and Typically Developing Subjects
Devon M. Middleton1,2, Nadia Barakat3, Sphoorti Shellikeri4, Scott H. Faro1,2, MJ Mulcahey3,5, and Feroze B. Mohamed1,2
1Department of Engineering, Temple University, Philadelphia, PA, United States, 2Department of Radiology, Temple University, Philadelphia, PA, United States, 3Shriners Hospital for Children, Philadelphia, PA, United States, 4Childrens Hospital of Philadelphia, Philadelphia, PA, United States, 5Thomas Jefferson University, Philadelphia, PA, United States

This study examines the effects of three different tensor estimation methods (linear least squares, robust outlier rejection, and linear least squares with non-positive tensor removal) on FA and MD in the cervical spinal cord for pediatric subjects. Both typically developing and injured subjects were examined.

4505.   22 Temperature-controlled Isotropic Diffusion Phantom with Wide Range of Apparent Diffusion Coefficients for Multicenter Assessment of Scanner Repeatability and Reproducibility
Michael A. Boss1, Thomas L. Chenevert2, John C. Waterton3,4, David M. Morris4, Hossein Ragheb4, Alan Jackson4, Nandita deSouza5, David J. Collins5, Bernard E. van Beers6, Philippe Garteiser6, Sabrina Doblas6, Stephen E. Russek1, Kathryn E. Keenan1, Edward F. Jackson7, and Gudrun Zahlmann8
1National Institute of Standards and Technology, Boulder, CO, United States, 2University of Michigan, Ann Arbor, MI, United States, 3AstraZeneca, Macclesfield, United Kingdom, 4University of Manchester, Manchester, United Kingdom, 5The Institute of Cancer Research, Sutton, Surrey, United Kingdom,6INSERM, France, 7University of Wisconsin, Madison, WI, United States, 8F. Hoffman-La Roche Ltd., Basel, Switzerland

We designed and built an ADC phantom to cover a wide range of physiologically relevant ADC values. The phantom used aqueous solutions of polyvinylpyrrolidone (PVP), and we maintained constant temperature by filling the phantom with ice water. The phantom was scanned at three sites (1.5 and 3.0 T) to assess variability of ADC measurement. We found excellent intrascanner repeatability and good reproducibility across systems and field strengths. There was non-negligible variability only for the highest concentrations of PVP, representing ADCs less than 0.3 x 10-3 mm2/s. The ADC of water at 0 °C was in excellent agreement with literature values of 1.1 x 10-3 mm2/s.

4506.   23 Quantitative Imaging Network Demonstration of ADC Nonlinearity Bias in Multi-center Trials
Dariya Malyarenko1, David Newitt2, Alina Tudorica3, Robert Mulkern4, Karl G. Helmer5, Michael A. Jacobs6, Lori Arlinghaus7, Thomas Yankeelov7, Fiona Fennessy4, Wei Huang3, Nola Hylton2, and Thomas L. Chenevert1
1Radiology, University of Michigan, Ann Arbor, MI, United States, 2Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States, 3Oregon Health and Science University, Portland, OR, United States, 4Dana Faber Harvard Cancer Center, Harvard Medical School, Boston, MA, United States, 5Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, MA, United States, 6John Hopkins University School of Medicine, Baltimore, MD, United States, 7Vanderbilt University Institute of Imaging Science, Vanderbilt Unversity, Nashville, TN, United States

Multi-center clinical trials seek to establish confidence levels for quantitative diffusion measurements. Scanner-specific gradient nonlinearity bias was observed for off-center measurements and implicated as a major source of potential reproducibility error in ADC mapping for some scanners. A practical procedure was developed to empirically characterize the systematic nonlinearity bias across diverse clinical MRI platforms. The results are demonstrated for representative MRI scanners utilized in clinical oncology trials supported by the NCI Quantitative Imaging Network (QIN).

4507.   24 Estimation of brain perfusion using flow-compensated intravoxel incoherence motion MRI: a simulation study
Yen-Peng Liao1, Shin-ichi Urayama1, and Hidenao Fukuyama1
1Human Brain Research Center, Kyoto University, Kyoto, Japan

Small blood volume of brain limits the application of IVIM-MRI. Hypoperfusion is an important index for diagnosis of some brain diseases. However, without sufficient signal-noise ratio, large estimation errors may be yielded in conditions of small cerebral blood volume (CBV) and cerebral blood flow (CBF). In this study, we proposed a method using conventional diffusion weighted imaging combined with flow-compensated pulses to estimate the CBF-related parameter. Computer simulation was performed to evaluate the accuracy and precision in heterogeneous brain tissues. The results showed that the proposed method can estimate extremely low CBF with better precision than the conventional fitting method.



Wednesday 14 May 2014
Exhibition Hall  14:30 - 15:30

  Computer #  
4508.   25 Probabilistic mapping of brain connectivity in the IIT Human Brain Atlas
Anna Varentsova1, Shengwei Zhang2, and Konstantinos Arfanakis2,3
1Department of Physics, Illinois Institute of Technology, Chicago, IL, United States, 2Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, IL, United States, 3Rush Alzheimer's Disease Center, Rush University, Chicago, IL, United States

The IIT Human Brain Atlas project is in the 4th year of development ( The latest version of the atlas contains high-quality artifact-free anatomical, DTI, HARDI templates, and probabilistic gray matter (GM) labels of the adult human brain in ICBM-152 space. The project is currently focusing on the development of a probabilistic white matter atlas that is complementary to the GM atlas, by performing tractography in the state-of-the-art HARDI template using the labels of the GM atlas as seeds. The present work aimed to: a) evaluate the tractography results, and b) generate probabilistic connectivity maps for pairs of GM labels.

4509.   26 Model-based neuroanatomy: Tractography validation, white-matter connections and geometrical organization
Franco Pestilli1, Justin Solomon2, Adrian Butscher3, and Brian Wandell1
1Psychology, Stanford University, Stanford, CA, United States, 2Computer Science, Stanford University, Stanford, CA, United States, 3Max Planck Institute for Informatics, Saarbruecken, Germany, Germany

We present a method for validating the organization of the white-matter tracts generated using diffusion weighted MRI and fiber tractography. Unlike previous techniques, our method locally determines the quality of each fascicle by associating nodes on each fascicle with nonnegative weights. These weights are optimized to predict the diffusion signal while also exhibiting smoothness along the fiber path. We find that different tractography algorithms generate different white-matter geometries. After cross-validation using our localized fascicle weights, however, we can describe the geometry of fascicles in white matter with confidence that our result is not a by-product of the choice of tractography techniques.

4510.   27 Visualizing complex white matter anatomy in the live monkey at 3T using super-resolution track density imaging
Louise Emsell1,2, Thijs Dhollander2, Koen Nelissen3, Ronald Peters1,2, Wim Vanduffel3, and Stefan Sunaert1,2
1Translational MRI, Imaging & Pathology, KU Leuven & Radiology, University Hospitas Leuvenl, Leuven, Belgium, 2Medical Imaging Research Center, Leuven, Belgium, 3Laboratorium voor Neuro-en Psychofysiologie, KU Leuven Medical School, Leuven, Belgium

Visualising white matter anatomy in vivo at submilimetre resolution using diffusion MRI is challenging without access to high-field and strong gradient systems. Short-tracks TDI (stTDI) is a post-processing technique that allows super-resolution visualization beyond the resolution of acquired data. In this pilot study we used stTDI to enhance anatomical contrast in 3T monkey data from 1.0mm3 to 0.25mm3 allowing the identification of structures not visible on the 1.0mm3 colour FA maps (e.g. stria medullaris, pre- and post-commissural fornix, decussation of the superior cerebellar peduncles). Reliability was assessed using bootstrapping to model the effect of noise in the stTDI maps

4511.   28 Tractography of Richardson-Lucy Spherical Deconvolution under Rician noise of Sparse Multiple q-shell Diffusion Imaging
Ping-Hong Yeh1, Erick Jorge Canales- Rodríguez2, John Morissette3, Arman A. Taheri3, Li-Wei Kuo4, Fang-Cheng Yeh5, Wei Lui3, John Ollinger3, Terrence Oakes3, Mark L. Ettenhofer6, and Gerard Riedy3
1Henry Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, United States, 2FIDMAG Research Foundation, Germanes Hospitalaries and CIBERSAM, Barcelona, Spain, 3National Intrepid Center of Excellence, Walter Reed National Military Medical Center, MD, United States, 4National Health Research Institutes, Taiwan, 5Carnegie Mellon University, PA, United States, 6Uniformed Services University of the Health Sciences, MD, United States

A variant of Richardson-Lucy (RL) spherical deconvolution (SD) algorithm modeling Rician noise from high angular resolution diffusion imaging (HARDI) data has been shown efficient in recovering the fiber orientation distribution in the low and medium SNR range. We evaluate the performance of RL_SD reconstruction on undersampled multiple q-shell HARDI data acquired by a clinical 3T MR scanner within an acceptable time frame (< 15 minutes).

4512.   29 Graph-based fibre tractography computing shortest paths between regions of interest
Niklas Kasenburg1,2, Matthew Liptrot1, Karsten M. Borgwardt2,3, Silas N. Ørting1, Mads Nielsen1, and Aasa Feragen1,2
1University of Copenhagen, Copenhagen, Zealand, Denmark, 2Max Planck Institutes Tübingen, Tübingen, Baden-Württemberg, Germany, 3Eberhard Karls Universität Tübingen, Baden-Württemberg, Germany

We present a novel, graph-based fibre tractography method, where the graph model can integrate any diffusion representation provided as an ODF. Tractography is performed by computing all possible shortest paths between regions of interest. For each path a confidence value is computed to assess its quality. Voxels are scored by the average value of paths they lie upon. Results for three different known tracts show the robustness of the method over five healthy subjects and a high overlap with tract atlases. The region based approach is especially useful for creating brain connectivity graphs while not suffering from path length dependencies.

4513.   30 Choosing Tractography Parameters to Improve Connectivity Mapping
Gabriel Girard1,2, Kevin Whittingstall3, Rachid Deriche2, and Maxime Descoteaux1
1Sherbrooke Connectivity Imaging Lab (SCIL), Computer Science Department, Université de Sherbrooke, Sherbrooke, Qc, Canada, 2ATHENA Project-Team, INRIA, Sophia-Antipolis, France, 3Department of Diagnostic Radiology, Faculty of Medicine and Health Science, Université de Sherbrooke, Sherbrooke, Qc, Canada

Diffusion-weighted imaging is often used as a starting point for in vivo white matter connectivity to reconstruct potential white matter pathways between brain areas. Tractography algorithms have many parameters which influence the reconstruction and connectivity analysis. But how does one choose the best set of parameters? In this study, we varied some of the tractography parameters and observed the connectivity score using the Tractometer evaluation system on the ISBI Challenge 2013 dataset. We think this provides useful information to choose tractography algorithms and its parameters for connectivity study.

4514.   31 Quantification of voxel-wise total tract density: addressing the problems associated with track-count mapping
Fernando Calamante1,2, Robert Elton Smith1, J-Donald Tournier1,3, David Raffelt1, and Alan Connelly1,2
1The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria, Australia, 2Department of Medicine, Austin Health and Northern Health, University of Melbourne, Melbourne, Victoria, Australia, 3Centre for the Developing Brain, King's College London, London, United Kingdom

A biological parameter that would be valuable to draw from a DWI experiment is the local white matter axonal density. It has been suggested that track-density imaging (TDI) could provide such a measure; however, this has been the subject of controversy. The post-processing method of SIFT was recently introduced to minimise tractography biases. Importantly, the TDI intensity following SIFT ideally corresponds to the DC term of the FOD spherical harmonic expansion. We characterise the TDI reproducibility with and without SIFT pre-processing, as well as the reproducibility of DC maps, to determine the most appropriate method for quantifying voxel-wise fibre densities.

4515.   32 Anatomical Priors to improve Global Tractography
Alia Lemkaddem1, Didrik Skiöldebrand1, Alessandro Dal Palú2, Jean-Philippe Thiran1,3, and Alessandro Daducci1
1Signal Processing Laboratory (LTS5), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland, 2Department of Mathematics and Computer Science, University of Parma, Italy, 3Department of Radiology, University Hospital Center (CHUV) and University of Lausanne (UNIL), Switzerland

Despite the improved robustness of current global tractography methods, the computation time makes them still not clinically feasible. Furthermore, the inclusion of anatomical priors are missing, i.e that the fiber starts and terminates in the gray matter. The latter constraint is thus crucial when performing connectivity studies, as it is mandatory to asses which pair of cortical regions a fiber is connecting. In this work, we have reformulated global tractography to reduce the computation time and furthermore embedded anatomical priors. We compare our results to state-of-the-art global tractography methods and therefore show how we improve.

4516.   33 Automated extraction of fiber bundles for population studies
Birkan Tunc1, William A. Parker1, and Ragini Verma1
1Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States

In this work, we design a framework for extraction of fiber bundles by introducing a group-wise consistent fiber clustering. This consists of defining a connectivity based fiber representation, using this representation to design a fiber atlas, and finally a subsequent adaptive clustering of a new subject based on this atlas. The connectivity based fiber representation encodes information related to the connectivity signatures of fibers. The fiber atlas is generated using several representative scans. The fibers of a new subject is clustered adaptively by incorporating this atlas as a prior. This whole framework results in a population consistent automated fiber clustering.

4517.   34 A method for evaluating the similarity of HARDI-based fiber tracking methods
Jian Lin1, Ken Sakaie1, Myron Zhang2, Katherine A Koenig1, Stephen E Jones1, and Mark J Lowe1
1Cleveland Clinic, Cleveland, OHIO, United States, 2The Ohio State College of Medicine, OSU, Columbus, OHIO, United States

Tractography can be sensitive to a number of parameters. However, there are few methods for quantifying such sensitivity. We demonstrate a means for quantitative comparison of pathways by comparison with an ensemble of tracks. We apply the method to compare the results of two probabilistic tractography methods: a computationally intensive Monte Carlo (MC) approach and fast partial differential equations (PDE) that is designed to rapidly replicate the results of the MC approach.

4518.   35 Alteration of White Matter Networks in Unilateral Mesial Temporal Sclerosis Identified by The Whole Brain Tract-Based Automatic Analysis
Yao-Chia Shih1,2, Yun-Chin Hsu2, Horng-Huei Liu3, and Wen-Yih Isaac Tseng2
1Institute of Biomedical Engineering, National Taiwan University, Taipei, Taipei, Taiwan, 2Center for Optoelectronic Medicine, National Taiwan University College of Medicine, Taipei, Taipei, Taiwan, 3Department of Neurology, National Taiwan University Hospital, Taipei, Taipei, Taiwan

Patients with unilateral mesial temporal sclerosis(MTS) were shown to have extensive gray matter (GM) and white matter (WM) abnormalities ipsilateral and contralateral to the seizure onset area. The changes of the whole brain WM tracts in MTS still remain unclear. In this study, we proposed a new method to perform tract-specific analysis over the whole brain, named tract-based automatic analysis (TBAA), using a diffusion spectrum imaging (DSI) template and a tract atlas. We hypothesized that left and right MTS would affect WM tract integrity over the whole brain and have different epileptic networks. In conclusion, we successfully identified different epileptic networks in left and right MTS, and found more extensive WM alterations in right MTS than in left MTS.

4519.   36 Impact of simulated lesions on communicability metrics of the brain structural network
Jennifer Andreotti1, Kay Jann1,2, Lester Melie-Garcia1,3, Stéphanie Giezendanner1, Thomas Dierks1, and Andrea Federspiel1
1Department of Psychiatric Neurophysiology, University Psychiatric Hospital, Bern, BE, Switzerland, 2Department of Neurology, University of California Los Angeles, Los angeles, California, United States, 3Department of Neuroinformatics, Cuban Neuroscience Center, Havana, Havana, Cuba

Communicability is a wider measure of network connectivity based on the idea that any path between two nodes will contribute to the total flow of information. Previous studies suggest that communicability may be sensitive to reorganizational changes of the brain network following a lesion. In our study the sensitivity of communicability related metrics was assessed using simulated lesions modelled as attacks to nodes and single edges. Our analysis confirmed that communicability metrics are an interesting tool to study the effects of lesions as they are sensitive to changes in the networks also in regions distant from the main lesion focus.

4520.   37 Evidence of brain damage in neuro asymptomatic HIV positive subjects kept on immune surveillance – A DTI study
Namita Singh Saini1, Giriraj Singh Gujral2, Richa Trivedi3, Archana Kumari3, Prabhjot Kaur3, Pawan Kumar3, Subhash Khushu3, and Rajender Prasad Tripathi3
1NMR, INMAS, Delhi, Delhi, India, 2Radiodiagnosis, Command Hospital Southern Command, Pune, Maharashtra, India, 3INMAS, Delhi, India

Neurological damage in HIV infection ranges from Minor Cognitive Motor Dysfunction in the neuroasymptomatic stage to frank HIV associated dementia later, necessitating placement under Highly Active Anti Retroviral Therapy (HAART). Conventional MRI is unable to detect abnormalities in the early stages while Diffusion Tensor Imaging shows reduced Fractional Anisotropy (FA) in Corpus Callosum in later stages. In a cohort of neuroasymptomatic HIV positive individuals we have found evidence of motor progression and reduced FA in Corticospinal Tract even in subjects with CD4 counts above 250, indicating disease progression. Thus DTI instead of CD4 could determine necessity for HAART cover.

4521.   38 Independent component analysis with ball-stick model tractography to solve an intra-voxel crossing fiber problem in clinical DTI data -permission withheld
Jeong-Won Jeong1,2
1Pediatrics and Neurology, Wayne State University, Detroit, Michigan, United States, 2PET center, Children's Hospital of Michigan, Detroit, Michigan, United States

The present study investigates whether independent component analysis with ball-stick model (ICA+BSM) analysis can estimate accurate orientation of multiple fiber bundles in clinical DTI. Simultaion studies assessing the absolute errors for two and three fibers per voxel demonsrated that ICA+BSM provides promising accuracy (median value of error angle = 4.1 ° and 10.4 ° for two and three fiber crossing, respectively) even at b-value =1000 s/mm2 and 12 encoding gradients. A preliminary human study suggests these errors may be marginal to isolate three crossing pathways, copus callosum, arcuate fasciculus, and cortico-spinal tracts in the lateral regions of central gyrus/sulcus.

4522.   39 Assessing Test-Retest Reliability of Quantitative Tractography Based on Diffusion Spectrum Imaging
Durai Arasan1, Wang Zhan1, and Luiz Pessoa1
1University of Maryland, College Park, MD, United States

Compared with diffusion tensor imaging (DTI) techniques, diffusion spectrum imaging (DSI) has demonstrated its superiority in characterizing complex diffusion patterns related to multiple fiber structures within a single imaging voxel. However, the test-retest reliability of DSI-based tractography remains unclear since assessments so far were generally based on DTI only. Here we present a study to investigate the test-retest reliability of a set of tracts in a group of healthy subjects, with 4 independent DSI scans for each. The outcome tractography measurements, such as fiber counts and tract length, show higher test-retest reliability than previously reported DTI results.

4523.   40 Analysis of the generalized fractional anisotropy in regions of fiber crossings: a simulation study -permission withheld
Jennifer Andreotti1, Alessandra Griffa2, Thomas Dierks1, Andrea Federspiel1, and Patric Hagmann2,3
1University Psychiatric Hospital, Bern, BE, Switzerland, 2Swiss Federal Institute of Technology, Lausanne, VD, Switzerland, 3CHUV, Lausanne, VD, Switzerland

Quantitative tractography methods require a detailed characterization of tissue properties specific to each white matter (WM) fiber tract. In our study Monte-Carlo simulations are used to understand how the generalized fractional anisotropy (GFA) is affected in the case of variable configurations of WM fiber tracts crossings. In particular, a linear sum of specific anisotropy measures for each of the tracts (linGFA) is compared to the usual GFA. The analysis shows that, compared to standard GFA, linGFA has a more linear relationship with the underlying characteristics of each of the fiber tracts and hence would be beneficial for quantitative tractography studies.

4524.   41 Robust Automated Tractography of the Brain using Diffusion Spectrum Imaging
Ek T Tan1, Xiaofeng Liu1, Aziz M Ulug2, Peter B Kingsley3, Anil K Malhotra2,3, Delbert G Robinson2,3, Philip R Szeszko2,3, and Luca Marinelli1
1GE Global Research, Niskayuna, NY, United States, 2Feinstein Institute for Medical Research, Manhasset, NY, United States, 3North Shore-LIJ Health System, Manhasset, NY, United States

Brain tractography is a manually-intensive and operator-dependent task, requires anatomical knowledge, and is inaccurate in regions containing crossing-fibers. We propose a robust, automated seeding method that performs image registration (1) to a predefined seeding template, and (2) multi-fiber tractography using compressed-sensing-accelerated diffusion spectrum imaging (CS-DSI). Because the method uses simple spherical ROIs, seeds can be easily adjusted on a manual basis to optimize tract identification. The automated algorithm was evaluated on CS-DSI data acquired in six healthy volunteers and seven patients with schizophrenia. The proposed method simplifies tractography workflow, and may provide improved reproducibility in studies utilizing diffusion tractography.

4525.   42 Diffusion Kurtosis Imaging based Tractography
Rafael Neto Henriques1,2, Luis Lacerda2,3, Rita Nunes2, Marta Morgado Correia1, and Hugo Alexandre Ferreira2
1Cognition and Brain Science Unit, Medical Research Council, Cambridge, United Kingdom, 2Institute of Biophysics and Biomedical Engineering, Faculty of Sciences of the University of Lisbon, Lisbon, Portugal, 3Centre for Neuroimaging Sciences, Institute of Psychiatry, King's College London, London, United Kingdom

Diffusion kurtosis Imaging (DKI) is an extension of diffusion tensor imaging. In addition to the diffusion tensor, DKI estimates a diffusion kurtosis tensor which provides an indirect measure of tissue heterogeneity. Moreover, previous studies show that the diffusion kurtosis tensor can help resolve crossing fibres. Thus, DKI-based tractography algorithms can be advantageous for visualization of crossing white matter pathways in clinical applications since they require less data and hence shorter scanning times relative to HARDI methods. Here, two tractography algorithms based on DKI are evaluated, one of which is shown to be able to resolve fibers crossing up to 45º.

4526.   43 Diffusion Tensor Imaging of the kidneys: functional assessment in the renal artery stenosis
Caterina Gaudiano1, Fiorenza Busato1, Beniamino Corcioni1, Valeria Clementi2, Emma Fabbri3, Paola Berardi3, and Rita Golfieri1
1Radiology Unit, Sant'Orsola-Malpighi Hospital, Bologna, Bologna, Italy, 2Clinical Science Development Group, GE Healthcare, Bologna, Italy, 3Medical Physics Department, Sant'Orsola-Malpighi Hospital, Bologna, Bologna, Italy

We studied 17 renal patients with RAS detected by using CE-MRA and 15 control subjects with 1.5 T MRI scanner adding DTI to the standard protocol. The comparison between the two groups showed that medullary ADC/FA in the study group were significantly lower than in the control group (P=0.034 and 0.022, respectively); there was no significant difference for the other parameters. This suggests that DTI could be a useful tool in evaluating renal alteration in hemodynamic RAS.

4527.   44 Evaluation of diffusion acquisition and tractography methods for neurosurgical planning systems
Jonathan Ashmore1, Flavio Dell'Acqua2, Ruth O'Gorman3, Gareth Barker2, and Jozef Jarosz1
1Neuroradiology, Kings College Hospital, London, United Kingdom, 2Department of Neuroimaging, Kings College London, London, United Kingdom, 3University Children's Hospital, Zurich, Switzerland

The purpose of this study was to investigate how diffusion acquisition parameters including the number of diffusion directions, the use of cardiac gating and the use of non-isotropic versus isotropic voxels impacts on tractography of the corticospinal tract for application to neurosurgical planning. We consider the tractography generated from a regulatory approved neurosurgical planning system to those produced from research software which incorporates constrained spherical deconvolution and probabilistic tractography. All tractography results are assessed against cyctoarchitectonic maps of the corticospinal tract which is used as a gold standard to asses the validity of the generated tracts.

4528.   45 Towards minimizing tractography errors and quantifying fiber crossing ratios
Stefan Sommer1,2, Sebastian Kozerke1, Erich Seifritz2, and Philipp Staempfli2
1Institute for Biomedical Engineering, ETH Zurich, Zurich, Zurich, Switzerland, 2Departement of Psychiatry, Psychotherapy and Psychosomatics, Zurich University Hospital of Psychiatry, Zurich, Zurich, Switzerland

A fundamental problem of tracking techniques based on high angular resolution diffusion data is that a quantitative evaluation of the resulting fiber tracts is still error prone and dependent on the algorithm and anatomy of interest. Furthermore, it remains challenging to derive e.g. crossing ratios of two or more intersecting fiber populations in a robust and reproducible manner. In this work, we present a method to minimize fiber tracking errors of any tracking algorithm in order to improve the quality of fiber tracts and fiber quantification of fiber crossing ratios. The method is validated using synthetic data and in-vivo data.

4529.   46 Orientation-dependent rendering of diffusion fiber tractography streamlines for improved visualization of complex tissue organization
Chantal M.W. Tax1, Marijn van Stralen1, Max A. Viergever1, Nick Ramsey2,3, and Alexander Leemans1
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, 2Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands, 3Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, Utrecht, Netherlands

The complex nature of diffusion MRI data has triggered the development of new approaches to visualize the architectural organization of diffusion MRI trajectories, which is becoming increasingly important with emerging human connectome studies and the growing interest of applying diffusion MRI tractography in clinical applications. We propose a visualization approach that interactively and selectively visualizes these tracts based on their local orientation, by applying an orientation-dependent transparency rendering to the fiber pathways. This greatly improves the visualization and exploration of the 3D architectural organization of pathways and the underlying tissue configurations that otherwise would be largely covered by other pathways.

4530.   47 A probabilistic method for unbiased longitudinal tractography with application to Huntington's disease
Anastasia Yendiki1, Martin Reuter1, Paul Wilkens1, Herminia Diana Rosas1, and Bruce Fischl1,2
1HMS/MGH/MIT Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 2MIT Computer Science and Artificial Intelligence Laboratory, Cambridge, MA, United States

We propose a probabilistic method for reconstructing white-matter pathways from longitudinal diffusion MRI data. We model the posterior probability of a pathway given a subject's full longitudinal data set, including diffusion and structural images from all time points. Our method is unbiased, making no assumptions on the direction of longitudinal change. By design, it allows longitudinal analysis of anisotropy and diffusivity measures to be performed as a function of position along the trajectory of a tract. We demonstrate that our longitudinal tractography improves both specificity and sensitivity compared to the conventional approach of performing tractography in each time point independently.

4531.   48 A High-Resolution Cardiomyofiber Atlas of the C57BL/6 Murine Heart
Stelios Angeli1, Nicolas Befera2, Jean-Marc Peyrat3, Evan Calabrese2, George Allan Johnson2, and Christakis Constantinides1,4
1University of Cyprus, Nicosia, Nicosia, Cyprus, 2Duke University Medical Center, Durham, NC, United States, 3Qatar Robotic Surgery Centre, Doha, Qatar,4Chi Biomedical Ltd, Nicosia, Cyprus



Diffusion Applications

Wednesday 14 May 2014
Exhibition Hall  14:30 - 15:30

  Computer #  
4532.   49 White matter tract atlas on NTU-DSI-122 template
Yu-Chun Lo1, Yung-Chin Hsu1, Yu-Jen Chen1, and Wen-Yih Isaac Tseng1,2
1Center for Optoelectronic Medicine, National Taiwan University College of Medicine, Taipei, Taiwan, 2Graduate Institute of Brain and Mind Sciences, National Taiwan University, Taipei, Taiwan

White matter tract atlas has gained interests in the neuroscience community because it provides 3D anatomy of white matter fiber pathways in the human brain. Recently, we constructed a diffusion spectrum imaging (DSI) template (NTU-DSI-122) from 122 healthy adults¡¦ DSI datasets. ¡§Difficult¡¨ fiber pathways which are of small sizes or have frequent crossings with other fiber tracts were reconstructed on the template. The tract atlas can be used to understand the geometric features of the white matter fiber pathways. Moreover, It allows us to implement a template-based approach that enables the microstructural integrity of the tracts in the human brain.

50 Aging in White Matter Revealed by Diffusional Kurtosis Imaging
Nan-Jie Gong1,2, Chun-Sing Wong1, Chun-Chung Chan3, Lam-Ming Leung4, Yiu-Ching Chu5, and Queenie Chan6
1Diagnostic Radiology, The University of Hong Kong, Hong Kong, China, 2Radiology, Stanford University, Stanford, CA, United States, 3Geriatrics & Medicine, United Christian Hospital, Hong Kong, China, 4Psychiatry, United Christian Hospital, Hong Kong, China, 5Radiology, Kwong Wah Hospital, Hong Kong, China, 6Philips Healthcare, Hong Kong, China

We utilized DKI, and for the first time a white-matter-model that provided metrics of explicit neurobiological interpretations in cognitive aging adults. Whole brain TBSS and regional results suggested that age-related white matter degenerations were broadly driven by axonal loss across nearly all tracts. In the anterior brain which is mostly composed of the late-myelinated fibre tracts, demyelination was also a major mechanism contributing to disintegration. Such probable coexistence of both mechanisms was in line with the Wallerian degeneration theory and is more supportive of the anterior-posterior gradient degeneration than the retrogenesis theory.

4534.   51 Correlation of DTI measures with neuropsychological scores in HIV-seropositive children
Bhaswati Roy1, Rakesh K Gupta1, Richa Trivedi2, Alok Kumar Singh3, Ravindra Kumar Garg3, Yogita Rai4, Vimla Venkatesh5, Mukesh Tripathi6, and Chandra M Pandey7
1Radiology & Imaging, Fortis Memorial Research Institute, Gurgaon, Haryana, India, 2NMR Reseach Centre, Institute of Nuclear Medicine and Allied Sciences, Delhi, Delhi, India, 3Neurology, King George's Medical University, Lucknow, Uttar Pradesh, India, 4Radiodiagnosis, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India, 5Microbiology, King George's Medical University, Lucknow, Uttar Pradesh, India,6Anaesthesiology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India, 7Biostatistics & Health Informatics, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, Uttar Pradesh, India

With an aim to assess the integrity of white matter in HIV positive pediatric patients, DTI and neuropsychological test battery was performed on 38 HIV-seropositive and 8 HIV-seronegative children born to HIV-seropositive mothers of same socioeconomic status. Voxel wise-based technique was implemented for the analysis of DTI data of participants. We observed significant changes in FA values in the corpus callosum, corona radiata, internal capsule. Significant direct correlation was also observed between FA and cognition scores relating to memory function. DT MRI could be used as an early objective marker of HIV related microstructural brain changes.

4535.   52 Differences in diffusional changes of the optic pathways between Multiple Sclerosis and Neuromyelitis Optica using Diffusional Kurtosis Imaging
Mariko Yoshida1, Masaaki Hori1, Kazumasa Yokoyama2, Nozomi Hamasaki1, Michimasa Suzuki1, Koji Kamagata1, Kohei Kamiya1, Shigeki Aoki1, Yoshitaka Masutani3, and Nobutaka Hattori2
1Department of Radiology, Juntendo University School of Medicine, Bunkyo, Tokyo, Japan, 2Department of Neurology, Juntendo University School of Medicine, Tokyo, Japan, 3Division of Radiology and Biomedical Engineering, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan

The purpose of this study is to evaluate differences in diffusional changes of the optic pathways between multiple sclerosis (MS) and neuromyelitis optica (NMO) using a new method, diffusional kurtosis imaging (DKI) Six NMO, eight MS, and seven healthy volunteers participated in this study. DKI sensitively detected abnormalities in optic tract in NMO patients. According to the past reports, NMO-immunoglobulin G targeting AQP4 is often observed in optic tact. DKI may be a more sensitive biomarker to differentiate between MS and NMO than conventional diffusional evaluations, such as diffusion tensor imaging.

4536.   53 Enhanced Contrast of Ischemic Stroke Lesions in Non-Gaussian Diffusion Imaging
Farida A. Grinberg1, Ezequiel Farrher1, Luisa Ciobanu2, Françoise Geffroy2, Denis Le Bihan2, and N. Jon Shah1,3
1Forschungszentrum Juelich, Juelich, Germany, 2Neurospin, CEA, France, 3RWTH Aachen University, Germany

We compare a sensitivity of two non-Gaussian diffusion models with the gold standard ADC approach in providing the contrast for ischemic lesions in animals: the stretched-exponential and gamma-distribution functions. Both functions provide good fits in the extended range of the diffusion weightings and allow for an enhanced contrast of the lesions. An interesting finding of this work is the appearance of laminar cortical structures in stroke lesions clearly visualised by the parameter maps of the investigated models but hardly observable in the ADC-maps.

4537.   54 Repeatability investigation and radiologic assessment of reduced field of view DWI on thyroid glands
Yonggang Lu1, Vaios Hatzoglou1, Hilda E. Stambuk1, Suchandrima Banerjee2, Ajit Shankaranarayanan2, Yousef Mazaheri1, Joseph O. Deasy1, and Amita Shukla-Dave1
1Memorial Sloan-Kettering Cancer Center, NEW YORK, New York, United States, 2Global Applied Sciences Laboratory, GE Healthcare, Menlo Park, California, United States

This study investigated the repeatability and assessed the radiologic quality of reduced field of view diffusion weighted imaging (rFOV DWI) in thyroid glands of healthy human volunteers. Repetitive DWI scans were performed on each subject within the same scan exam and across scan exams. Image qualities were scored and apparent diffusion coefficient (ADC) values were calculated on the lobes of thyroid glands and followed by reproducibility investigation. The study demonstrated that rFOV DWI had significantly improved image quality but lower ADC values and lesser repeatability value of ADC compared to the conventional DWI techniques in the region of thyroid glands.

4538.   55 Correlation of Diffusion Tensor Imaging (DTI) measures with memory dysfunction scores in hypothyroid patients
Subash Khushu1, Sadhana Singh1, Richa Trivedi1, Kavita Singh1, Pawan Kumar1, and L Ravi Shankar2
1NMR Research Centre, INMAS DRDO, Delhi, delhi, India, 2Thyroid Research Centre, INMAS DRDO, Delhi, delhi, India

The aim of our study was to correlate DTI measures (FA and MD) with memory dysfunction scores in hypothyroid population. Diffusion tensor tractography (DTT) and PGI-memory scale (PGIMS) were performed on eight healthy controls and eight hypothyroid patients. Our results showed the inverse correlation of memory dysfunction score with FA of WM tracts (RIFO and LIFO) and positive correlation of memory dysfunction scores with MD of RATR fibre tract. These findings suggest that the microstructural changes in these WM tracts may contribute to underlying dysfunction in memory in hypothyroidism.

4539.   56 IVIM-DTI of Healthy Human Liver
Oi Lei Wong1,2 and Michael D Noseworthy3,4
1Department of Medical Physics and Applied Radiation Science, McMaster University, Hamilton, Ontario, Canada, 2Medical Physics and Research Department, Hong Kong Sanatorium & Hospital, Hong Kong, Hong Kong, Hong Kong, 3Department of Electrical and Computer Engineering, McMaster University, Hamilton, Ontario, Canada, 4Imaging Research Center, St.Joseph's Healthcare, Hamilton, Ontario, Canada

Both IVIM and DTI are well recognized MRI methods for quantifying flow and diffusion, respectively. Simultaneously assessing both techniques (IVIM-DTI) has recently been shown feasible in the kidney. We proposed that the same technique is also feasible in the liver with multiple breath holds and subsequent retrospective motion compensation. Based on our result, IVIM-DTI analysis is able to differentiate between hepatic blood vessels and liver parenchyma, while minimizing the pseudo-hepatic artifact.

4540.   57 Assessment of aquaporins function in stages of liver fibrosis using multi-b diffusion weighted magnetic resonance imaging
LI Qiu-ju1, ZHANG Zi-heng2, LI Jia-hui1, YU Bing1, ZHANG Xin1, ZHAO Zhou-she2, SHI Yu1, XIN Jun1, and GUO Qi-yong1
1Radiology, Shengjing Hospital of China Medical University, Shenyang, Liaoning, China, 2General Electronic Company Healthcare (China), Beijing, China

A multi-b diffusion weighted MR imaging measurement was performed to examine the effects of AQP inhibition to normal and liver-fibrotic rats in vivo. At low-b values, the resulted ADCs reflected the hepatic blood perfusion information while the functional changes of the AQPs on cell membranes at high b values. The AQP1 expression in the liver endothelial cells increased with aggravation of liver fibrosis. An increase of perfusion was observes at S1, but a decrease occurred with the addition of inhibitor. At S2, perfusion decreased, and further decreased with inhibitor. The inhibition tests were all negative.

4541.   58 Sensitivity and specificity of prostate tumor discrimination by IVIM approximation
Gina Belmonte1, Vito Biondo2, Augusto La Penna3, Francesco Carbone4, Gianluca Vischi5, Leonardo Semeraro5, and Fabrizio Banci Buonamici1
1Medical Physics, University Hospital of Siena, Siena, Italy, Italy, 2University of Siena, Italy, Italy, 3Radiology, University of Siena, Italy, Italy,4Radiology, University Hospital of Siena, Italy, Italy, 5Radioterapy, University of Siena, Italy, Italy

We analyzed precision and accuracy in the discrimination of prostate tumor of IVIM parameters measured with a bi-exponential fit and a simplified approach, that allows to estimate the diffusion coefficient and the pseudo-diffusion fraction from a 2 b-values acquisition. ROC analysis were used to extract the optimum cut-off for each parameter that maximize the accuracy of test. The simplified IVIM parameters are not accurate estimates of the corresponding ones from the bi-exponential fit, but discriminate prostate tumor from healthy tissues in a accurate way. This simplified technique allows therefore to reduce the acquisition time and preserve a good diagnostic accuracy.

4542.   59 Age-related Changes of Prostate Peripheral Zone in Normal Adults£ºEvaluation by DTI
tao gong1,2, bin wang1, lili li2, and guangbin wang2
1binzhou medical university, shandong, yantai, China, 2Shandong Medical Imaging Research Institute, shandong, jinan, China

The DTI parameters of MD/FA values of normal prostate peripheral zone is different in different age groups, and MD values were increased with age , while FA values decreased.

4543.   60 Differential Diagnosis of Chest Lesions: Values of Diffusion-Weighted MR Imaging
Nan-Han Lu1,2, Tai-Been Chen2, Yung-Hui Huang2, Hueisch-Jy Ding2, Lee-Ren Yeh1, and Jeon-Hor Chen1,3
1Department of Radiology, E-DA Hospital, Kaohsiung, Kaohsiung, Taiwan, 2Department of Medical Imaging and Radiological Sciences, I-Shou University, Kaohsiung, Kaohsiung, Taiwan, 3Functional Onco-Imaging, Department of Radiological Sciences, University of California Irvine, Irvin, CA, United States

Lung cancer is the leading cause of cancer death among men and women worldwide. The precise pre-operation diagnosis of chest neoplasms and inflammatory nodules using CT, MRI and PET-CT is difficult. The most sensitive diagnostic method is the surgical biopsy. The differences in imaging findings may reflect differences in histopathologic features of chest lesions. On T2-weighted MR images could not be used to distinguish malignant from benign pulmonary nodules. On diffusion-weighted MR imaging (DWI), the apparent diffusion coefficient (ADC) value refers to the specific diffusion capacity of a biologic tissue. ADC value depends largely on the presence of barriers to diffusion within the water microenvironment.The goal of this study is to present a novel method for differential diagnosis among primary chest cancers, metastatic tumors and benign tumors using ADC standard deviation value (SD) of diffusion-weighted MR imaging.

Crombé Amandine1,2, Menegon Patrice1, Tourdias Thomas1, and Dousset Vincent1
1Department of neuroradiology, Pellegrin Hospital, Bordeaux Segalen University, Bordeaux, France, 2ENS Lyon, Lyon, France

From a commercially available axial SE-EPI DTI sequence, after empirical optimizations in order to limit distortion in an acceptable scan time, our aim was to determine the normal values of DTI parameters (mean diffusivity, axial diffusivity, radial diffusivity and fractional anisotropy) in key locations of cervical spine (cortico spinal tract, posterior column and anterior horn, full spine section) at each cervical level from C1 to C7.

62 Spatial and voxel-wise evaluation of eigenvector stability within the human calf at 3T
Conrad Rockel1,2 and Michael D Noseworthy1,2
1School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada, 2Imaging Research Centre, St Joseph's Healthcare, Hamilton, Ontario, Canada

Spatial distribution of eigenvector variability was investigated in the human calf at 3T using different amoungs of signal averages and encoding directions. The principal vector was found to vary much less than the two minor vectors. Furthermore, the spatial distribution appeared non-random and favourable to the peripheral musles, although noisier for the minor eigenvectors. The spatial distribution appeared dependent upon scan acquisition conditions.

4546.   63 Changes in the Medial and Lateral Gastrocnemius Fiber Architecture with Age.
Yanjie Xue1, Usha Sinha1, Vadim Malis1, Robert Csapo2, and Shantanu Sinha2
1Physics, SDSU, San Diego, CA, United States, 2Radiology, UCSD, San Diego, CA, United States

Age related changes in muscle alter fiber architecture (fiber lengths and pennation angles). Diffusion tensor imaging (DTI) allows the mapping of fiber architecture, this study investigates age related changes in fiber architecture of the medial and lateral gastrocnemius using DTI. Ten female subjects (5 young/ 5 old) were imaged using DTI and fiber length and pennation angles were determined. Decreases in fiber length and pennation angle were seen in the older cohort as well as regional differences between distal and middle origin fibers. The length/pennation angle changes in the LG were smaller than those seen in the MG.

4547.   64 MRI quantification of diffusion and perfusion in bone marrow by intravoxel incoherent motion (IVIM) and non-negative least square (NNLS) analysis.
Giulio Gambarota1, Antoine Marchand2, Eric Hitti1, Frederik Monge1, Regis Duvauferrier2, Raphael Guillin2, and Hervé Saint-Jalmes1
1Université de Rennes 1, LTSI, Rennes, F-35000, France, 2Department of Imaging, Rennes University Hospital, Rennes, F-35000, France

The aim of this study was to assess the feasibility of measuring diffusion and perfusion in vertebral bone marrow using the intravoxel incoherent motion (IVIM) approach and to investigate the benefits of the non-negative least square (NNLS) technique for analysis of IVIM data. Results indicated that, for a proper analysis of IVIM data, the use of NNLS is essential especially in cases where the signal-to-noise ratio is low or where motion artifacts and other factors might affect the data quality.

4548.   65 3 Tesla Diffusion Tensor Imaging (DTI) of Normal Uterus in Young and Middle-aged Women during the Menstrual Cycle: an Initial Study to Evaluate the Cyclic Changes of Fractional Anisotropy (FA) and Apparent Diffusion Coefficient (ADC) Values
Yonglan He1, Huadan Xue2, Ning Ding2, Yuan Li3, and Zhengyu Jin4
1Radiology, Peking Union Medical College Hospital, Beijing, Beijing, China, 2Radiology, Peking Union Medical College Hospital, Beijing, China, 3gynaecology and obstetrics, Peking Union Medical College Hospital, Beijing, China, 4Peking Union Medical College Hospital, Beijing, China

Prospectively investigate the cyclic changes of FA and ADC values of the normal uterus in a larger population divided into different age groups during 4 phases of the menstrual cycle, and the correlation with the basic serum hormone levels in menstrual phase.

4549.   66 Effects of gradient nonlinearity correction on DTI ADC and FA measurements for assessing breast cancer treatment response
David Newitt1, Ek Tsoon Tan2, Lisa Wilmes1, Hee Jung Shin3, Luca Marinelli2, and Nola Hylton1
1Radiology and Biomedical Imaging, UCSF, San Francisco, CA, United States, 2GE Global Research, Niskayuna, NY, United States, 3Radiology, Asan Medical Center, University of Ulsan, Korea

Gradient nonlinearity (GN) is a significant source of error for quantitative diffusion MRI and is of particular concern in breast imaging where anatomy requires large offsets from magnet isocenter. GN correction (GNC) to correct for spatially-varying diffusion encoding was evaluated in DTI acquired ADC and FA of tumor and normal tissue regions in breast cancer subjects undergoing neoadjuvant chemotherapy. GNC resulted in a mean change in tumor ADC of -11% (range -4% to -19%), and in FA of -6% (range -24% to 20%). Percent change in tumor ADC between visits had an RMS change of 3% with GNC.

4550.   67 Effect of scanner and head coil on diffusion MRI measures of the brain
Matthan W.A. Caan1, Michiel B. de Ruiter1, Liesbeth Reneman1, and Aart J. Nederveen1
1Radiology, Academic Medical Center, Amsterdam, Netherlands

The goal of this study was to compare diffusion parameters between three scanners of one vendor with the head-coils used in daily practice on the particular scanners. Of seven subjects, diffusion weighted MRI data were acquired on 3.0 Tesla Philips Intera, Achieva and Ingenia scanners. Signal to Noise Ratio (SNR), Mean Diffusivity (MD) and Fractional Anisotropy (FA) maps were compared. Inter-scanner differences were three times as large as intra-scanner differences. SNR varied up to 20% between scanners, was positively associated with MD and negatively with FA. Differences in MD and FA up to 7% are in agreement with literature.

4551.   68 Self correction of blood flow effect for brain-fluctuation MRI -permission withheld
Marina Takatsuji1, Toshiaki Miyati1, Naoki Ohno1, Saori Yoshizawa2, Tomohiro Noda1, Satoshi Kobayashi3, Toshifumi Gabata3, and Osamu Matsui3
1Division of Health Sciences, Institute of Sciences, Kanazawa University, Kanazawa, Ishikawa, Japan, 2School of Health Sciences, College of Medical, Pharmeceutical and Health Sciences, Kanazawa University, Kanazawa, Ishikawa, Japan, 3Department of Radiology, School of Medical Sciences, Kanazawa University, Kanazawa, Ishikawa, Japan

The change of the apparent diffusion coefficient ( ADC)during the cardiac cycle in the brain are affected by the regional cerebral blood flow (rCBF). To evaluate hemodynamic-independent water fluctuaion, we corrected the rCBF effect by using the ECG-triggered single shot diffusion echo planner data itself. We corrected the the changes of ADC (ĢADC) by the maximum ADC with b=0-200 having the highest correlation with the rCBF. There was no significant correlation between corrected-ĢADC and eCBF. Corrected-ĢADC makes it possible to obtain the degree of fluctuation of the water molecules hemodynamic-in the brain.

4552.   69 Reproducibility of Diffusion Weighted MRI under Active Breathing Coordinator control
Evangelia Kaza1, David Collins1, Richard Symonds-Tayler1, Rafal Panek1, and Martin Osmund Leach1
1CR-UK and EPSRC Cancer Imaging Centre, Institute of Cancer Research and Royal Marsden Hospital, Sutton, Surrey, United Kingdom

The feasibility of diffusion-weighted (DW) MRI automatically acquired during breath holding enforced by a modified, MR-compatible Active Breathing Coordinator (ABC) system was demonstrated on healthy volunteers. The position of abdominal organs, major vessels and the diaphragm was shown to be reproducible between different measurements under ABC control at the same inhaled air volume and unaffected by changes of non-spatial sequence parameters. The observed repeatability of organ position using the ABC device suggests that DW-MRI with controlled lung volume can be matched to CT images acquired with the same ABC settings and thus support radiotherapy treatment planning.

4553.   70 In vivo detection of sexual dimorphisms in the brain of a Passerine songbird, a proof-of-principle study
Julie Hamaide1, Geert De Groof2, Johan Van Audekerke1, Lisbeth Van Ruijssevelt1, Zhenhua Mai1, Firat Kara1, Marleen Verhoye1, and Annemie Van Der Linden1
1University of Antwerp, Wilrijk, Antwerp, Belgium, 2University of Antwerp, Antwerp, Belgium

The aim of the present study was to implement a non-invasive in vivo diffusion tensor imaging (DTI) protocol in the tiny zebra finch. To test for the sensitivity of the optimized sequence, we tried to visualize known (histology) sexual dimorphisms in adult zebra finches. We found the known dimorphisms and illustrate the benefit of using whole-brain in vivo MRI by revealing novel, unexplored sexual dimorphisms in the adult zebra finch brain.

4554.   71 Structure Specific Analysis of white and gray matter in the rat brain after exposure to chronic stress
Philip A Cook1, Paul A Yushkevich1, Sijie Tian2, Sandra Luz3, Seema Bhatnagar4, and James C Gee1
1Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States, 2School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA, United States, 3Children's Hospital of Philadelphia, PA, United States, 4Anesthesiology and Critical Care, Children's Hospital of Philadelphia and University of Pennsylvania, Philadelphia, PA, United States

TSA in rat brain

4555.   72 Neurotoxic aspects of tungusten Alloy Based Heavy Metals in Rat Brain: A DTI study
Ritu Tyagi1, Poonam Rana1, Richa Trivedi1, B.S. Hemanth Kumar1, Deepak Bhatnagar2, and Subash Khushu1
1NMR Research centre, Institute of Nuclear Medicine and Allied Sciences (INMAS), DELHI, DELHI, India, 2School of Biochemistry, Devi Ahilya Vishwavidayalaya, Indore, M.P., India

HMTAs are composed of a mixture of tungsten (91–93%), nickel (3–5%) and either cobalt (2–4%) or iron (2–4%) particles which are increasingly adopted as the raw material to make parts of military products. Diffusion tensor imaging (DTI) study was performed at day 1, day 3, and day 5 in controls and animals treated metals used in HMTAs and their mixture. An increase in MD values were observed in cerebral pedeuncle with cobalt and tungsten, whereas all the three metal salts and their mixture showed pronounced effect on the thalamic region of the brain compared to controls.