Electronic Posters : Diffusion & Perfusion - Neuro
Click on to view the abstract pdf and click on to view the video presentation.

Monday May 9th
Exhibition Hall  14:00 - 16:00 Computer 79

14:00 3959.   A new comprehensive framework for probabilistic tractography of fanning fibres 
Jennifer Campbell1, Parya MamayyezSiahkal2, Peter Savadjiev3, Ilana R. Leppert1, Kaleem Siddiqi2, and G. B. Pike1
1McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada, 2Centre for Intelligent Machines, McGill University,3Brigham and Women's Hospital, Harvard University

The objective of the current work was to develop an improved probabilistic tractography framework that could handle, in addition to crossing fibres, information on more complex subvoxel geometries, such as fanning fibres. The technique incorporates a residual bootstrap probabilistic processing step, followed by a tractography process that results in the assignment of an index of connectivity, at each voxel in the volume, to the region of interest of the user's choice. This connectivity index is derived using a weakest link approach, and solves many of the problems inherent in popular connectivity indices that are based on frequency of connection.

14:30 3960.   A Full Bi-tensor Neural Tractography Algorithm Using the Unscented Kalman Filter 
Stefan Lienhard1, James Malcolm2, Carl-Frederik Westin3, and Yogesh Rathi2
1Information Technology and Electrical Engineering, ETH Zürich, Zürich, Switzerland, 2Harvard Medical School, Psychiatry Neuroimaging Laboratory, Boston, MA, United States, 3Harvard Medical School, Laboratory of Mathematics in Imaging, Boston, MA, United States

We introduce a tractography method by extending an existing framework which models the signal with Gaussian tensors. At each fiber point an unscented Kalman filter finds the most consistent direction as a mixture of previous estimates and of the local model. In the existing framework the diffusion tensor’s second and third eigenvalues are identical. We extend the tensor representation so that the diffusion tensor can be an arbitrary ellipsoid. Synthetic experiments show better angular resolution at fiber crossings. Tests on in vivo data show that our new model finds fibers in areas where the simpler model stops.

15:00 3961.   Advanced Fiber Tracking Using ODF Based Force Fields 
Robert Stefan Vorburger1, Carolin Reischauer1, and Peter Boesiger1
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

High angular resolution diffusion-weighted imaging techniques have been developed to resolve complex intravoxel fiber structure. Until now, just a few dedicated algorithms have been introduced. The current work presents a novel tracking approach that simulates particle motion in a force field which is derived directly from the so-called orientation distribution function using principles of classical mechanics. On the basis of the derived particle tracts, connectivity maps and virtual fibers are subsequently generated. The benefit of the algorithm is demonstrated by presenting tracking results in a healthy volunteer.

15:30 3962.   Clinically feasible crossing fiber tractography based on additional local HARDI 
Kenji Ito1, Yoshitaka Masutani1,2, Yuichi Suzuki2, Shigeki Aoki3, Osamu Abe4, Akira Kunimatsu1,2, and Kuni Ohtomo1,2
1Graduate School of Medicine Univ. of Tokyo, Bunkyo-ku, Tokyo, Japan, 2Univ. of Tokyo Hospital, Bunkyo-ku, Tokyo, Japan, 3Radiology, Juntendo Hospital, Bunkyo-ku, Tokyo, Japan, 4Radiology, Nihon University Itabashi Hospital, Itabashi-ku, Tokyo, Japan

Although HARDI (High Angular Resolution Diffusion Imaging) acquisition techinique is essential for crossing fibers analysis, its limitation for clinical situation is the long scan time. We propose a clinically feasible scheme; local-HYDI (Hybrid Diffusion Imaing), which combines whole brain imaging using LARDI (Low Angular Resolution Diffusion Imaging) and local brain imaging with HARDI for crossing fibers volume. Using the local-HYDI data, we also present a Hybrid Tractography (HT) technique based on local switching of deterministic and probabilistic techniques according to data type (LARDI or HARDI) of the location. In this abstract, we evaluated the feasibility of our local-HYDI and HT.

Tuesday May 10th
  13:30 - 15:30 Computer 79

13:30 3963.   Voxel-based Morphometric Analysis of Fiber Tract Volume of Corpus Callosum Using Large Deformation Diffeomorphic Metric Mapping and Diffusion Spectrum Tractography 
Hsiao-Chin Cheng1, Yung-Chin Hsu2, and Wen-Yih Isaac Tseng1,3
1Center for Optoelectronic Biomedicine, National Taiwan University College of Medicine, Taipei, Taiwan, 2Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan, 3Department of Medical Imaging, National Taiwan University Hospital, Taipei, Taiwan

We normalized diffusion spectrum imaging data sets, acquired from 7 males and 7 females, to a template using 6D Large Deformation Diffeomorphic Metric Mapping (LDDMM) algorithm. Voxel-based analysis was performed to compute the gender difference in tract volume of the corpus callosum. The males¡¦ tract volume was generally larger than the females¡¦, but there was a spatial variation in the difference. The most prominent difference was found in frontal and temporal lobes, whereas little difference was found in parietal and occipital lobes. Our study demonstrates the feasibility of 6D LDDMM in the analysis of tract volume using voxel-based morphometric approach.

14:00 3964.   Fiber Bundle Segmentation Using Major Diffusion Orientations in Reduced Position Orientation Space 
Esmail Davoodi-Bojd1, Mohammadreza Nazem-Zadeh2, Hamid Soltanian-Zadeh1, and Quan Jiang2
1Control and Intelligent Processing Center of Excellence, School of Electrical and Computer Engineering, University of Tehran, Tehran, Iran, 2Neurology, Henry Ford Hospital, Detroit, MI, United States

Position Orientation Space (POS) is composed of three dimensions for position and two dimensions for orientation information in each voxel. The POS can be very helpful in low resolution datasets. If two fiber tracts are irresolvable sharing crossing area in three dimensional space, they may be resolvable in five dimensional POS. Since four distinct peaks of the Orientation Distribution Function (ODF) are adequate for extracting the fibers, we propose a novel strategy to the compute major directions from the ODF, then they are employed for segmenting fiber bundles by an algorithm similar to that of Hagmann et al.

14:30 3965.   COMET – A framework for the large scale Cluster analysis Of Major Equivalent Tracts 
Christia Ros1, Daniel Güllmar1, and Jürgen R Reichenbach1
1Medical Physics Group, Department of Diagnostic and Interventional Radiology I, Jena University Hospital, Jena, Thuringia, Germany

To cope with large tractography data sets, we propose COMET – a new framework that is capable to perform autonomous, high quality Cluster analysis Of Major Equivalent Tracts (COMET). The framework facilitates exploratory data analysis of fiber tracts and enables the exploration of axonal pathways and connections, as well as quantitative analysis in large groups of subjects. By exploiting the capabilities of modern multiprocessor system and using new clustering techniques as well as a variety of similarity measures, our toolkit is able to cluster large data sets on the order of minutes.

15:00 3966.   Clustering Method for Estimating Principal Diffusion Directions 
Mohammadreza Nazem-Zadeh1, Kourosh Jafari-Khouzani2, Abbas Babajani-Fermi2, Siamak Pourabdollah Nejad-Davarani1, Hamid Soltanian-Zadeh2,3, and Quan Jiang1
1Neurology, Henry Ford Hospital, Detroit, MI, United States, 2Diagnostic Radiology, Henry Ford Hospital, Detroit, MI, United States, 3Control and Intelligent Processing Center of Excellence, School of Electrical and Computer Engineering, University of Tehran, Tehran, Iran

Using High angular resolution diffusion imaging (HARDI), the fiber orientation distribution function (ODF) on the unit sphere is calculated and used to extract the principal diffusion directions (PDDs). Fast and accurate estimation of PDDs is a prerequisite for tracking algorithms that deal with fiber crossings. In this paper, a clustering approach to estimate PDDs is proposed which is an extension of fuzzy c-means clustering developed for orientation coordinates of points on a sphere. Experimental results illustrate that the proposed clustering algorithm is more accurate, more resistant to noise, and faster than the techniques currently being utilized.

Wednesday May 11th
  13:30 - 15:30 Computer 79

13:30 3967.   Accurate Estimation of Local Fiber Orientations for Groupwise Tractography 
Pew-Thian Yap1, John H. Gilmore2, Weili Lin1, and Dinggang Shen1
1Radiology and BRIC, University of North Carolina, Chapel Hill, NC, United States, 2Psychiatry, University of North Carolina, Chapel Hill, NC, United States

Tractography in an atlas space allow the reconstructed trajectories to form a common geometry onto which diffusion properties from the individual images can be projected for tract-based comparison. We show, however, that conventional average-atlas-based approach, when applied to HARDI data, causes significant deviation of the estimated local orientations from the 'true' orientations, inevitably jeopardizing subsequent trajectory reconstruction. In our approach, local fiber orientation information is estimated by harnessing orientation information simultaneously from all images in a population. We model the orientation statistics at each voxel location by employing the bipolar Watson distribution, which will capture the mean orientations of the fiber bundles and also the related degrees of orientation dispersion. This distribution information, when fed into a stochastic tractography algorithm allows reconstruction of fiber trajectories which are consistent across images in the population.

14:00 3968.   Auditory tracts identified with the combined use of fMRI and DTI 
Laura Mancini1,2, Faiza Javad2, Jason D Warren3, John S Thornton1,2, Xavier Golay1,2, Tarek Yousry1,2, and Caroline Micallef1,2
1Lysholm Dept of Neuroradiology, National Hospital for Neurology and Neurosurgery, UCLH NHS Foundation Trust, London, WC1N 3BG, United Kingdom, 2Academic Neuroradiological Unit, Dept Brain Repair and Rehabilitation, UCL Institute of Neurology, London, WC1N 3BG, United Kingdom, 3Dementia Research Centre, UCL Institute of Neurology, London, WC1N 3BG, United Kingdom

This is the first combined DTI/fMRI study to investigate pathways connecting cortical and sub-cortical structures in the auditory system. Auditory pathways connect the inferior collicular nucleus (ICN) and medial geniculate body (MGB) to the auditory cortex. These tracts are particularly difficult to identify because they intersect the optic radiation and numerous other fascicles. 2.3mm isotropic DTI (64 gradient directions, b-value=1400s/mm 2) were analyzed with probabilistic, 2-tensor model tractography. ICN and MGB were identified anatomically, while auditory cortices were identified by fMRI using sparse acquisition and amplitude-modulated iterated-ripple-noise pitch as stimuli. Our results successfully identified sub-cortical auditory projections in 14 healthy subjects.

14:30 3969.   Are larger pathways faster ? a spherical deconvolution tractography study on the visuo-spatial pathways 
Michel Thiebaut de Schotten1,2, Flavio Dell'Acqua1,3, Stephanie Forkel1,4, and Marco Catani1,3
1Natbrainlab, Institute of Psychiatry, London, United Kingdom, 2Hopital de la Salpêtrière, CRICM-INSERM UMRS 975, Paris, France, 3Department of Neuroimaging Sciences, Institute of Psychiatry, London, United Kingdom, 4Department of Forensic and Neurodevelopmental Sciences, Institute of Psychiatry, London, United Kingdom

Little is known about how the size of tract can modify the speed of conduction. Larger tract volumes could depend on a number of factors, including greater fibre myelination, higher number of axons and larger axonal diameter. Experimental physiology has shown that the conduction speed of larger diameter, or more myelinated axons is faster. A higher number of axons would also boost the speed of conduction by assuring a parallel processing. So, are larger pathways faster ? In this study we found a direct correlation between tract volume and the speed of detection visual events.

15:00 3970.   Voxel-wise histogram analysis of tractography streamline length for assessing brain injury 
Kerstin Pannek1, Thomas Kampf2, Jane Mathias3, Greg Brown4, Jamie Taylor5, Olivier Salvado6, and Stephen Rose7
1Centre for Advanced Imaging, The University of Queensland, Brisbane, Queensland, Australia, 2Department of Experimental Physics 5, University of Wuerzburg, Wuerzburg, Germany, 3School of Psychology, University of Adelaide, Adelaide, South Australia, Australia, 4MRI Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia, 5Radiology, Royal Adelaide Hospital, Adelaide, South Australia, Australia, 6Biomedical Imaging, Australian eHealth Research Centre, Brisbane, Queensland, Australia, 7Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia

Streamline number and streamline length are quantitative tractography metrics that are influenced by white matter pathology. We propose to assess streamline length in a fully automated voxel-wise manner. The length distribution within an individual voxel can be described by a mixture of Gaussian distributions, and compared across subjects. Voxel-wise length distributions appear to be highly reproducible over time. We demonstrate how this new method can be used to identify fibre populations affected by white matter pathology.

Electronic Posters : Diffusion & Perfusion - Neuro
Click on to view the abstract pdf and click on to view the video presentation.
Brain Across Species

Monday May 9th
Exhibition Hall  14:00 - 16:00 Computer 80

14:00 3971.   In vivo measurement of T2 relaxation times in mouse brain at 17.6 Tesla 
Firat Kara1, Fu Chen1, Jörg Matysik1, and Alia Alia1
1Leiden Institute of Chemistry, Leiden University, Leiden, South holland, Netherlands

Knowledge of T2 relaxation times for mouse brain at ultra high field (17.6 T) can be important to optimize imaging parameters for optimum contrast to noise and higher sensitivity and to observe changes induced by various pathological conditions. In this work in vivo T2 relaxation parameters for mouse brain have been measured at 17.6 T and compared with those measurements at 9.4 T. Phantom solutions were used to quantify and validate changes in T2 relaxation time at different field strengths. A decrease in T2 relaxation time was found in several regions of mouse brain at 17.6 T as compared with 9.4 T. Phantom results validated a decrease in T2 relaxation time at higher field strengths.

14:30 3972.   High-resolution zebrafish white matter fibertracks 
Nyoman Dana Kurniawan1, Gary Cowin1, Shaun P. Collin2,3, and Jeremy F.P. Ullmann3
1Centre for Advanced Imaging, The University of Queensland, Brisbane, Queensland, Australia, 2School of Animal Biology, The University of Western Australia, Crawley, Western Australia, Australia, 3School of Biomedical Sciences, The University of Queensland, Brisbane, Queensland, Australia

Zebrafish is an important model in development and neuroscience research. However due to its extremely small size (4x2x1mm), ultra-high resolution MR diffusion images are required to obtain meaningful information. Here we present the white matter tracks of the zebrafish brain reconstructed using Track Density Imaging at 5-micron resolution and comparison with conventional high-resolution anatomical MRI.

15:00 3973.   Characterizing Brain Development in the Ferret in vivo Using Diffusion Tensor Imaging 
Yulin V Chang1, and Philip V Bayly1
1Mechanical Engineering, Washington University, St. Louis, MO, United States

We investigated the relationships between cortical folding, T2, average ADC, and diffusion anisotropy in a developing ferret brain using diffusion tensor imaging. Our results show that brain folding is accompanied by the vanishing of the diffusion anisotropy in the gray matter. We observed that the white matter has not been fully myelinated by the last time point (P30) of measurement, which suggests that cortical folding and white matter myelination are independent processes during brain development.

15:30 3974.   MRI Assessment of the Effect of Different Resuscitation Fluids on Cerebral Blood Flow and Edema Following Experimental Traumatic Brain Injury and Hemorrhagic Shock in Mice 
Lesley M Foley1, T Kevin Hitchens1,2, John A Melick3, Nancy T Ho2, Tusey C Tam2, Chien Ho1,2, and Patrick M Kochanek3,4
1Pittsburgh NMR Center for Biomedical Research, Carnegie Mellon University, Pittsburgh, PA, United States, 2Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, United States, 3Safar Center for Resuscitation Research, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States, 4Departments of Critical Care Medicine, Pediatrics and Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States

Using MRI we assessed brain and pulmonary edema and cerebral blood flow (CBF) after resuscitation, from TBI+HS using two conventional solutions, namely the crystalloid Lactated Ringers (LR), the colloid hextend (Hex), and an octomeric recombinant hemoglobin (rHb). MRI assessment of edema using 1/T1 seemed to provide a more sensitive measurement than wet weight/dry weight values. Recombinant hemoglobin whilst increasing CBF initially also produces slightly more edema than either LR or Hex. One possibility is that rapid restoration of CBF in the damaged brain with rHb results in perfusion of severely damage tissue and edema.

Electronic Posters : Diffusion & Perfusion - Neuro
Click on to view the abstract pdf and click on to view the video presentation.
Diffusion Phantoms

Tuesday May 10th
Exhibition Hall  13:30 - 15:30 Computer 81

13:30 3975.   A Diffusion Tensor Resolution Phantom 
Michael Bach1, Bram Stieltjes2, Klaus Fritzsche3, Wolfhard Semmler1, 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, 3Medical Imaging and Biological Informatics, German Cancer Research Center, Heidelberg, Germany

Recently, several different diffusion phantoms have been proposed but a dedicated resolution phantom is lacking. Here we present a circular phantom consisting of four 2mm wide tracts separated by a 2 mm space. The phantom was measured at isotropic resolutions of 2x2x2 mm3 and 3x3x3 mm3. A high FA of 0.7 was obtained. Fiber tracking clearly shows a resolution effect; at 2x2x2 mm3, the individual bundles can be separated whereas at 3x3x3 mm3, no separation can be obtained. The presented resolution phantom may be used to investigate various parameters influencing the obtainable effective resolution of the used DTI-sequence and post-processing.

14:00 3976.   A Selectable Diffusion Coefficient Phantom Based on Restricted Diffusion 
Joseph P. Hornak1, Hongmei Yuan2, Scott Kennedy3, and Edmund Kwok3
1Imaging Science, RIT, Rochester, NY, United States, 2Chemistry, RIT, Rochester, NY, United States, 3University of Rochester, Rochester, NY, United States

Quantitative MRI studies of diffusion require a phantom to calibrate an imaging system. One convenient diffusion phantom consists of a set of hydrocarbon liquids with diffusion coefficients (D) between that of water and approximately 0.5x10-9 m2/s. Regional, national, and international shipping constraints make commercializing phantoms containing flammable hydrocarbons more costly. We propose a diffusion phantom based on the restricted diffusion of water within tightly packed glass fibers. This phantom gives a range of diffusion coefficients between Dwater and 0.5x10-9 m2/s using only water as the NMR signal baring liquid.

14:30 3977.   Characterization of the TE Dependence of IVIM Biomarkers in a Flow Phantom and In Vivo 
Gene Young Cho1, Daniel K Sodickson1, and Eric E Sigmund1
1Center for Biomedical Imaging - Radiology, NYU School of Medicine, New York, New York, United States

Recent applications of IVIM diffusion-weighted imaging produce biomarkers of tissue structure and vascularity. However, these biomarkers may show dependence on echo time (TE). Recent observations have shown TE dependence of perfusion fraction, attributable to differential relaxation weighting. There may be dependence of the pseudo-diffusion rate on TE when such times are similar to transit times for a vessel branch. With proper modeling, this dependence could be exploited for quantification of vessel parameters useful for characterization of tumors or highly perfused organs. We explore the dependence of IVIM parameters upon TE in a phantom and human kidney in a clinical scanner.

15:00 3978.   Regional Biomechanical Property of Intracranial Tissue using Dynamic Diffusion MRI: A Phantom Study 
Hirohito Kan1, Tosiaki Miyati1, Mitsuhito Mase2, Masaki Hara3, Makoto Kawano3, Yuta Shibamoto3, Harumasa Kasai3, Nobuyuki Arai3, Akihiro Kitanaka1, and Risa Yorimitsu1
1Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, Kanazawa, Ishikawa, Japan, 2Department of Neurosurgery and Restorative Neuroscience, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Aichi, Japan, 3Department of Radiology, Nagoya City University Hospital, Nagoya, Aichi, Japan

To clarify the mechanism, i.e., the fluctuation of the water molecules in the intracranial tissue, we determined the temporal ADC waves obtained with diffusion magnetic resonance imaging (MRI) using a hemodialyzer phantom. Our original phantom makes it possible to analyze the change in ADC due to the volume loading, assess the biomechanical property, and verify the mechanism of the fluctuation of water molecules in the intracranial tissue.

Electronic Posters : Diffusion & Perfusion - Neuro
Click on to view the abstract pdf and click on to view the video presentation.
Arterial Spin Labeling - Methods

Monday May 9th
Exhibition Hall  14:00 - 16:00 Computer 82

14:00 3979.   Velocity Selective Arterial Spin Labeling Using an Inversion Pulse Train 
Ruitian Song1, Ralf B. Loeffler1, Adam M. Winchell1, and Claudia M. Hillenbrand1
1Radiological Sciences, St Jude Children's Research Hospital, Memphis, TN, United States

A new velocity selective ASL using an inversion pulse train was developed. Because inversion labeling was achieved with our new VSASL method, the labeling efficiency can be improved by approximately a factor of 2, compared to saturation labeling. The diffusion b value was the same in both label and control scans, therefore diffusion contamination was eliminated in the perfusion images.

14:30 3980.   Optimization of Tagging Efficiency Using ECG-gated Velocity-matched B1-increased Pseudo-continuous Arterial Spin Labeling 
Wen-Ming Luh1, Eric C. Wong2, S Lalith Talagala3, and Peter A. Bandettini1
1Functional MRI Facility, NIMH, National Institutes of Health, Bethesda, MD, United States, 2Departments of Radiology and Psychiatry, University of California, San Diego, La Jolla, CA, United States, 3NMRF, NINDS, National Institutes of Health, Bethesda, MD, United States

In conventional pseudo-continuous arterial spin labeling (PCASL) techniques, a train of short RF pulses with constant amplitude are played out over entire labeling period. However, changes in velocity throughout the cardiac cycle can compromise tagging efficiency especially during systolic phases with high velocity and volume throughput. To minimize mismatch between RF amplitude increase and systolic phase, here we employed ECG triggering and short labeling period to be within a typical cardiac cycle. Moreover, RF B1 modulation was implemented in a pair-wise interleaved fashion to minimize run-to-run differences.

15:00 3981.   Territorial Arterial Spin Labelling at 7T using PICORE 
Rebecca Susan Dewey1,2, Dorothee P Auer1, and Susan T Francis3
1Division of Academic Radiology, The Univeristy of Nottingham, Nottingham, United Kingdom, 2Sir Peter Mansfield Magnetic Resonance Centre, The University of Nottingham, Nottingham, United Kingdom, 3Sir Peter Mansfield Magnetic Resonance Centre, The Univeristy of Nottingham, Nottingham, United Kingdom

Perfusion territory maps provide unique information for the characterisation of cerebral haemodynamics. Ultra-high field (7T) provides increased image SNR and perfusion sensitivity. Territorial Arterial Spin Labelling (TASL) performance relies on good coil coverage and B1 homogeneity, both issues at 7T. PICORE (Proximal Inversion with a Control for Off-Resonance Effects) based TASL with a FOCI pulse is implemented to address these limitations. We assess sharpness and efficiency of the inversion profile of the FOCI pulse. Selective inversion slabs are positioned to perform Territorial Arterial Spin Labelling of the LICA, RICA and BA at 7T, providing maps of the three vascular territories.

15:30 3982.   Inversion-Prepared Pulsed ASL with Single-Shot FSE Readout for the In Vivo Measurement of the T1 of Arterial Blood 
David Thomas Pilkinton1,2, John A Detre2,3, and Ravinder Reddy1,2
1Biochemistry & Molecular Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 3Center for Functional Neuroimaging, Unversity of Pennsylvania, Philadelphia, Pennsylvania, United States

To accurately quantify CBF with ASL, it is necessary to have an estimate of the T1 of arterial blood (T1a). However, it is very challenging to measure T1a in vivo because of the high flow velocity in arteries and the relatively small artery diameters, particularly in small animals. A PASL approach for measuring T1a has been suggested in the literature to avoid these problems. We implemented an similar PASL approach to measure T1a in vivo which increases the dynamic range, avoids possible venous signal contamination, and maximizes the SNR in the presence of static field inhomogeneities.

Tuesday May 10th
  13:30 - 15:30 Computer 82

13:30 3983.   Acquisition Strategy for 3D GRASE with a Sharp Point Spread Function Towards Whole Brain ASL Perfusion Mapping at 3T 
Qin Qin1,2, Alan J Huang2,3, Jun Hua1,2, Matthias J.P. van Osch4, and Peter CM van Zijl1,2
1Radiology, Johns Hopkins University, Baltimore, Maryland, United States, 2F.M. Kirby Center, Kennedy Krieger Institute, Baltimore, Maryland, United States, 3Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 4Radiology, Leiden University Medical Center, Leiden, Netherlands

3D GRASE acquisition is a natural choice for whole brain ASL perfusion mapping. In GRASE, however, a long echo train is often used that not only causes blurring but also leads to signal loss due to T2 decay during acquisition. An acquisition strategy that can achieve a sharper point spread function would require an echo train of length comparable to tissue T2. In this work, this is theoretically derived and subsequently demonstrated experimentally for whole brain perfusion mapping with both high resolution and high SNR efficiency.

14:00 3984.   Look-Locker 3D-EPI ASL at 7T 
Emma Louise Hall1, Penny A Gowland1, and Susan T Francis1
1Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom

Look-Locker ASL provides a technique for the simultaneous assessment of transit time for accurate assessment of perfusion. However, due to the limited time between readout pulses volume coverage of this method is generally limited to a few slices. Here we implement LL-FAIR combined with a 3D-EPI readout at 7T. We show that 3D-EPI provides a significant increase in the number of slices that can be acquired due to parallel imaging along two directions, improved SNR and identical perfusion weighting across all slices. This allows a larger volume coverage without compromising on the temporal or spatial resolution.

14:30 3985.   Turbo-flash based Arterial Spin Labeling at 7T 
Zhentao Zuo1,2, Rui Wang1,2, Dapeng Liu1,2, Rong Xue1, Yan Zhuo1, and Danny JJ Wang3
1State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China, People's Republic of, 2Graduate University, Chinese Academy of Sciences, Beijing, China, People's Republic of, 3Neurology, UCLA, Los Angeles, CA, United States

Arterial spin labeling (ASL) at 7T is attractive due to prolonged blood T1 as well as increased SNR at ultrahigh field. In the present study, turbo-flash based pulsed and pseudo-continuous ASL sequences were performed at both 7 and 3T, with different spatial resolutions and post-labeling delays. High quality perfusion images were obtained at 7T even with the spatial resolution of 0.85 X 1.7mm2 and with post-labeling delays up to 3s. Motor cortex activation was further demonstrated which precisely located the primary motor cortex to the precentral gyrus, with the spatial resolution of 0.85 X 1.7mm2.

15:00 3986.   Dual-Density and Parallel Spiral ASL for Motion Artifact Reduction 
Craig H. Meyer1,2, Li Zhao1, Michael Lustig3, Manal Jilwan-Nicolas2, Max Wintermark2, John P Mugler III2, and Frederick H Epstein2
1Department of Biomedical Engineering, University of Virginia, Charlottesville, VA, United States, 2Department of Radiology, University of Virginia, Charlottesville, VA, United States, 3Department of Electrical and Computer Engineering, UC Berkeley, Berkeley, CA, United States

This study compares single-shot and interleaved constant-density spiral arterial spin labeling (ASL) sequences to their dual-density analogs. Single-shot dual-density parallel spiral ASL reconstructed using the SPIRiT parallel image reconstruction algorithm had the best combination of motion robustness, spatial resolution, and resistance to suceptibility artifacts.

Wednesday May 11th
  13:30 - 15:30 Computer 82

13:30 3987.   Full Model-Based Analysis of QUASAR Arterial Spin Labelling 
Michael A Chappell1,2, Esben T Petersen3, Mark W Woolrich2, Xavier Golay4, and Stephen J Payne1
1Institute of Biomedical Engineering, University of Oxford, Oxford, United Kingdom, 2FMRIB Centre, University of Oxford, Oxford, United Kingdom, 3Clinical Imaging Research Center, NUS-A*STAR, Singapore, 4Institute of Neurology, University College, London, United Kingdom

The QUASAR Arterial Spin Labelling (ASL) approach is unique in making use of a variety of flow suppressed and non-suppressed data. This makes ‘model-free’ analysis feasible, it also is advantageous for ‘model-based’ strategies, since the different regimes can be used to model more accurately the arterial and tissue signals. Here a novel model-based strategy is proposed that models the contribution of label in the arteries as magnitude and dominant direction of arterial blood flow. This provides a more appropriate comparison to model-free approaches and also permits different models of label dispersion to be more rigorously tested.

14:00 3988.   Absolute Regional Gray Matter Perfusion Measured with Arterial Spin Labeling Calibrated using Phase Contrast MRI 
Ahmet Murat Bagci1, Sang Lee1, David Adams1, Clinton Wright1, Birgit Ertl-Wagner2, and Noam Alperin1
1University of Miami, Miami, FL, United States, 2University of Munich, Munich, Germany

Absolute values of cerebral blood flow (CBF) measurements obtained using arterial spin labeling (ASL) methods depends on the implementation of the technique, the imaging parameters, and also influenced by subject’s hemodynamics. This report presents early results from the incorporation of phase contrast measurements of total cerebral blood flow to obtain calibrated regional CBF in deep gray matter and cerebral cortex obtained with 2D- whole brain PASL. The calibrated regional CBF values are more consistent with previously reported values. The CBF measurements using ASL in combination with PCMRI may help overcome the limitations of ASL in providing reliable absolute CBF values.

14:30 3989.   Detection of MR perfusion transit time effects in pulsed arterial spin labeling using a ‘model validity metric’ 
Yang Wang1, Josef Pfeuffer2, Gary D Hutchins1, and Andrew J Saykin1
1Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, Indiana, United States, 2MR Applications Development, Siemens Healthcare, Erlangen, Germany

Standard acquisition and processing of MR perfusion using Q2TIPS PASL images is extended by an additional acquisition and a metric analysis. A transit time compensation between slices and perfusion model validity measures are introduced to reduce artifacts by prolonged bolus transit time effects.

15:00 3990.   Regional Coherence-based Denoising (RECODE) for Arterial Spin Labeled Perfusion MRI 
Ze Wang1, and John A Detre2
1Dept of Psychiatry, U of Penn, Philadelphia, PA, United States, 2Dept of Neurology, Univ of Penn, Philadelphia, PA, United States

This work presents a novel denoising method for ASL perfusion MRI. Regional data coherence as well as the systematic tag-control spin labeling paradigm are explicitly utilized to reduce noise in ASL data in order to improve the SNR of ASL MRI. As compared to standard denoising routine based on spatial smoothing, the proposed method remarkably improved the CBF quantification results.

Thursday May 12th
  13:30 - 15:30 Computer 82

13:30 3991.   WITHDRAWN
14:00 3992.   A Total Variation spatial prior for the estimation of perfusion and transit time maps in PASL-MRI 
Nuno Santos1,2, João M. Sanches1, Inês Sousa1,2, and Patricia Figueiredo1
1Institute for Systems and Robotics, Instituto Superior Técnico, Lisbon, Portugal, 2Healthcare Sector, Siemens S.A., Portugal

Maps of perfusion and transit time can be measured using PASL, by fitting a kinetic model to magnetization difference images acquired at multiple inversion times. Here, a total variation (TV) spatial prior is incorporated into a Bayesian estimation method, based on the maximum a posteriori criterion, which also incorporates knowledge regarding the model physiological parameters. Monte Carlo simulations using different test objects showed reduced estimation errors when including the TV prior relative to commonly used Euclidean distance spatial priors and physiological priors only. Application to data collected from healthy subjects at 3T also showed improved performance for the TV prior.

14:30 3993.   Absolute CBF Quantification with PASL During Hyperoxia Corrected with the Simultaneous Measurement of the T1 of Arterial Blood 
David Thomas Pilkinton1,2, John A Detre2,3, and Ravinder Reddy1,2
1Biochemistry & Molecular Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 2Center for Magnetic Resonance and Optical Imaging, Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 3Center for Functional Neuroimaging, Unversity of Pennsylvania, Philadelphia, Pennsylvania, United States

A number of studies have used ASL approaches to investigate the regional CBF changes with hyperoxia. Although it is well-known that inhaled oxygen creates a significant reduction in the T1 of arterial blood (T1a), only a minority of these studies have incorporated T1a changes in their ASL calculations. In this study, we simultaneously measured CBF and T1a in vivo during hyperoxia using a PASL approach in the rat brain at 3T. These data allow for correction per subject basis to quantify the degree to which the reduction in CBF measured with ASL is due to the reduction in T1a.

15:00 3994.   Comparison of Arterial Transit Times Estimated Using Arterial Spin Labeling 
Yufen Chen1, Danny J.J. Wang2, and John A. Detre1
1Center for Functional Neuroimaging, University of Pennsylvania, Philadelphia, PA, United States, 2Department of Neurology, University of California Los Angeles, Los Angeles, CA, United States

Transit time refers to the time needed for labeled spins to travel from the label region to the imaging region in ASL. Here, we investigate the effects of labeling position on the arterial and microvascular transit times of two efficient transit time mapping techniques: LL-ASL and FEAST. Our results demonstrate a linear relationship between label position and arterial transit time, with the slope related to the average blood velocity from label to image region. A 650ms discrepancy was observed between arterial and microvascular transit times, likely the result of controlled oxygen transport to facilitate exchange at the capillary bed.

Electronic Posters : Diffusion & Perfusion - Neuro
Click on to view the abstract pdf and click on to view the video presentation.
Arterial Spin Labeling - Applications

Monday May 9th
Exhibition Hall  14:00 - 16:00 Computer 83

14:00 3995.   Magnetic Resonance Imaging of Blood Flow of the Human Retina 
Qi Peng1,2, Yi Zhang1,2, Oscar San Emeterio Nateras1,2, and Timothy Q Duong1,2
1Radiology, UT Health Science Center at San Antonio, San Antonio, TX, United States, 2Research Imaging Institute, UT Health Science Center at San Antonio, San Antonio, TX, United States

Blood flow (BF) measurement of the human retina is challenging because the thin retina is located in a region of high magnetic susceptibility, is susceptible to eye motion and requires high spatial resolution. This study successfully demonstrated the feasibility of high spatial-resolution (500x800¦Ìm) retinal BF measurement under baseline and hypercapnia. Pseudo-continuous arterial spin-labeling technique with background suppression and single-shot turbo spin-echo acquisition were employed to improve BF sensitivity, suppress vitreous signal, and achieve high spatial resolution free of image distortion and signal dropout. This approach could open up new avenues for retinal research and may have important clinical applications.

14:30 3996.   Blood Flow MRI of the Human Retina during Isometric Exercise-Induced Increase in Blood Pressure 
Yi Zhang1, Oscar San Emeterio Nateras2, Qi Peng1,2, Carlos A. Rosende3, John M. Johnson4, and Timothy Q. Duong1,2
1Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States, 2Radiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States, 3Ophthalmology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States,4Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States

This study investigated the relation between perfusion pressure and blood flow (BF) in the human retina using MRI during rest and isometric exercise (squeezing a tennis ball inside the MRI scanner). Basal BF in the posterior retina was 137±47mL/100mL/min (±SD, N=4). Isometric exercise increased mean BF, heart rate, mean arterial pressure, and ocular perfusion pressure (P<0.05), but not intraocular pressure, arterial oxygen saturation, end-tidal carbon dioxide, or respiratory rate (P>0.1). A MRI approach provides objective quantitative BF with a large field of view without depth limitation. BF MRI during isometric exercise provides a unique means to study retinal physiology and autoregulation free of adverse pharmacological effects.

15:00 3997.   Layer-Specific Blood-Flow MRI of Retina Degeneration at 11.7T 
Guang Li1, Bryan De La Garza2, Yen-Yu I Shih2, Eric R Muir2,3, and Timothy Q Duong2
1Radiology, UT Health Science Center at San Antonio, San Antonio, Texas, United States, 2UT Health Science Center at San Antonio, United States, 3Georgia Institute of Technology, Atlanta, Georgia, United States

Vision loss due to retinal degeneration is a major problem in ophthalmology. We developed blood flow (BF) MRI (44x44x600 μm3) using continuous arterial spin labeling at 11.7T to image layer-specific, quantitative retinal BF (RBF) and choroidal BF (ChBF) in the rat eye. This method was used to investigate BF changes in an animal model of progressive retinal degeneration, the Royal-College-of-Surgeons (RCS) rat. In this model, RBF and ChBF were affected differently by retinal degeneration. RBF was attenuated in RCS rats as the retina degenerated, while ChBF likely was not. BF MRI provides layer-specific quantitative BF data of the retina without depth limitation and with a large field-of-view, potentially opening up new avenues for retinal disease research in animal models.

15:30 3998.   Layer-Specific Retinal and Choroidal Blood-Flow MRI in a Mouse Model of Glaucoma 
Eric R Muir1, William Lavery2, Jeffrey W Kiel2, René C Rentería3,4, and Timothy Q Duong1
1Research Imaging Institute, University of Texas Health Science Center, San Antonio, TX, United States, 2Department of Ophthalmology, University of Texas Health Science Center, San Antonio, TX, United States, 3Department of Physiology, University of Texas Health Science Center, San Antonio, TX, United States, 4Center for Biomedical Neuroscience, University of Texas Health Science Center, San Antonio, TX, United States

Glaucoma, a leading cause of blindness worldwide, is characterized by progressive degeneration of retinal ganglion cells and the optic nerve. Elevated intraocular pressure, which is associated with glaucoma, may reduce blood flow (BF) in the eye. The retina is nourished by two separate vasculatures, the retinal and choroidal vessels. Arterial spin labeling MRI was used to image layer-specific retinal and choroidal BF in the DBA/2J mouse model of glaucoma at different stages of disease. Retinal and choroidal BF were distinctively reduced at different ages in DBA/2J mice. MRI provided a non-invasive method to monitor vascular changes in rodents in vivo.

Tuesday May 10th
  13:30 - 15:30 Computer 83

13:30 3999.   Calibrated fMRI using simultaneous EEG and fMRI and the effect of hypercapnia on CMRO2 
Andrea Federspiel1, Ariane Orosz1, Martinus Hauf2, Roland Wiest2, Danny JJ Wang3, Thomas Dierks1, and Kay Jann1
1Department of Psychiatric Neurophysiology, University Hospital of Psychiatry, Bern, Switzerland, 2Institute of Diagnostic and Interventional Neuroradiology, University of Bern, Switzerland, 3Department of Neurology, UCLA, Ahmanson-Lovelace Brain Mapping Center, Los Angeles, CA, United States

Calibrated fMRI is performed with simultaneous EEG and fMRI recording. In the fMRI setting a set of ASL and BOLD images are acquired with hypercapnia condition and a set of ASL and BOLD images during visual stimulation (checkerboard 2Hz). Calculation of CMRO2 during hypercapnia was performed and revealed values in line with previous findings. Visual evoked potentials showed latency of P100 peak at 116 ms. During hypercapnia a reduced power in frequency bands theta and alpha 2 are observed. These findings suggest that during hypercania CMRO2 may not be constant. These findings may have implication in future calibrated fMRI setting.

14:00 4000.   Coupling between resting cerebral perfusion and EEG power 
Lars Michels1, Ernst Martin1, Daniel Brandeis2, Rafael Lüchinger2, Peter Klaver3, Ajit Shankaranarayanan4, David C Alsop5,6, and Ruth L O'Gorman1
1University Children's Hospital, Zürich, Switzerland, 2Department of Child and Adolescent Psychiatry, University of Zürich, Zürich, Switzerland, 3Department of Psychology, University of Zürich, Zürich, Switzerland, 4Global Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States, 5Beth Israel Deaconess Medical Center, Boston, MA, United States, 6Harvard Medical School, Boston, MA, United States

This study examines the relationship between resting EEG power fluctuations in low, medium, and high frequency bands and resting cerebral perfusion. EEG and ASL data were acquired in separate measurement sessions in a group of 12 healthy adults. Peak EEG power correlated positively with perfusion in a widespread network including both cortical and sub-cortical regions. After controlling for whole-brain ASL perfusion, significant correlations were restricted to a smaller network of regions, and predominantly negative correlations were found for alpha frequencies, whereas higher frequencies (gamma) exhibited predominantly positive correlations.

14:30 4001.   Dynamics of CBF and BOLD responses to a Cued Deep Breathing paradigm 
Inês Sousa1,2, Pedro Vilela3, and Patricia Figueiredo1
1Institute for Systems and Robotics, Instituto Superior Técnico, Lisbon, Portugal, 2Healthcare Sector, Siemens, S.A., Lisbon, Portugal, 3Imaging Department, Hospital da Luz, Lisbon, Portugal

An approach for the optimization of a Gamma impulse response function to be used in a GLM analysis ASL perfusion and BOLD data, collected during a Cued Deep Breathing paradigm, is proposed. The optimal parameter values of the Gamma function were determined, for the whole-brain in terms of maximum number of active voxels, and on a voxel-by-voxel basis in terms of the maximum Z score. The results obtained indicate that a voxe-by-voxel optimization may be preferable due to the spatial heterogeneity of the parameters, yielding optimal lag and width maps and contributing to more sensitive and accurate cerebrovascular reactivity measurements.

15:00 4002.   Dosage-dependent effects of isoflurane on cerebral blood flow in rhesus monkeys 
Chun-Xia Li1, Sudeep Patel1, Eddie Auerbach2, and Xiaodong Zhang1
1Yerkes Imaging Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA, United States, 2Center for MR Research, School of Medicine, University of Minnesota, Minneapolis, United States

Non-human primates were widely used as various disease models and examined under isoflurane anesthesia.Isoflurane is believed to increase the cerebral blood flow in general but the detailed effects in the monkey brain still remain unknown. In this study, the dosage effects of isoflurane (0.6 to 1.2 MAC) on CBF in the different brain regions of monkey brain were investigated with the continuous arterial-spin-labeling (CASL) technique.

Wednesday May 11th
  13:30 - 15:30 Computer 83

13:30 4003.   Memory performance is negatively correlated with resting CBF level in hippocampus in healthy elderly 
Siyuan Hu1, Hengyi Rao1, Lauren Mancuso1, John A. Detre1, and David Wolk1
1Department of Neurology, University of Pennsylvania, Philadelphia, PA, United States

The medial temporal lobe (MTL) plays a critical role in episodic memory function, and is activated by episodic memory tasks. Deficits in episodic memory performance are also seen in aging and in Alzheimer's disease. Here we correlated resting MTL function as measured by arterial spin labeled (ASL) perfusion MRI with episodic memory performance in 31 cognitively normal elderly participants. After controlling for age, years of education, gender, and global CBF values, we found a negative correlation between episodic memory performances and resting CBF in left hippocampus. These findings suggest that resting MTL perfusion provides a biomarker of memory performance phenotype, and that increased CBF may represent a compensatory response to memory decline.

14:00 4004.   Temporal and extra-temporal perfusion abnormality in mesial temporal lobe epilepsy revealed by arterial spin labeling(ASL)-based MRI 
Guangming Lu1, Zhiqiang Zhang1, Cuiping Yuan1, and Lianfang Shen1
1Department of Radiology, Jinling hospital, Nanjing University School of Medicine, Nanjing, Jiangsu, China, People's Republic of

Interictal single-photon emission computed tomography (SPECT) studies have demonstrated that there is hypoperfusion within the extra-temporal structures besides to the temporal lobe in mesial temporal lobe epilepsy (mTLE), which contributes to the proposal of concept of the mesial temporal lobe epilepsy network [1]. The purpose of this study was to determine the feasibility of detecting perfusion abnormalities in mTLE using arterial spin labeling (ASL)-based MRI, which is a noninvasive method for calculating regional cerebral blood flow (rCBF).

14:30 4005.   Quantification of Cerebral Blood Flow (CBF) in Acute-on Chronic Liver Failure (ACLF) patients with 3D Pseudo continuous Arterial Spin Labeling 
Abhishek Yadav1, Rakesh Kumar Gupta1, Santosh Kumar Yadav1, M Rangan2, V A Saraswat3, M A Thomas4, and R KS Rathore5
1Radiodiagnosis, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India, Lucknow, Uttar Pradesh, India, 2Pediatric Gastroenterology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India, Lucknow, UP, India, 3Pediatric Gastroenterology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India, lucknow, UP, India, 4Department of Radiological Sciences, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India, California, Los Angels, United States, 5Department of Mathematics & Statistics, Indian Institute of Technology, Kanpur, UP, India

Acute-on-chronic liver (ACLF) failure develops in patients with previously well-compensated chronic liver disease following an acute precipitating event. It is known that the cerebral autoregulation may be defective in patients of liver failure, and raised ICP is often seen in ALF patients. Ammonia and cytokines are known to increase in ACLF, and have synergistic role in pathogenesis of HE. The current data suggest that ASL demonstrates the increase in CBF various grey matter regions in ACLF and may be used in the in initial and follow up study of these ACLF patients.

15:00 4006.   Combined Dynamic Susceptibilty Contrast (DSC) Imaging and Arterial Spin Labeling (ASL) for Quantitative Perfusion Measurements in Children with Diffuse Pontine Glioma 
Brian A Taylor1, Adam Winchell1,2, Jan Sedlacik1, Alberto Broniscer3, Ruitian Song1, Ralf B Loeffler1, and Claudia M Hillenbrand1
1Radiological Sciences, St. Jude Children's Research Hospital, Memphis, TN, United States, 2Biomedical Engineering, University of Memphis, Memphis, TN, United States,3Oncology, St. Jude Children's Research Hospital, Memphis, TN, United States

An algorithm that combines dynamic susceptibility contrast (DSC) and arterial spin labeling (ASL) imaging for quantitative perfusion measurements was evaluated in a large clinical study in children with diffuse pontine glioma. DSC measurements were calibrated to ASL measurement in voxels with low transit times. An alternative method was evaluated which calibrated DSC to ASL in the gray matter.

Thursday May 12th
  13:30 - 15:30 Computer 83

13:30 4007.   Test-Retest Reproducibility Assessment of CBF Measurements with 3D GRASE ASL at 1.5 T in Aged Population with Alzheimer’s Disease 
Alexandre Coimbra1, Dai Feng2, Sonia Apreleva2, Peter Hu3, S Ramana4, A Bernstein5, Matthias Guenther6, William Cho7, Mark Forman8, Ajay Verma9, Gary Herman10, Richard Baumgartner2, and David Feinberg4
1Imaging, Merck & Co, Inc, West Point, PA, United States, 2Biometrics, Merck & Co, Inc, Rahway, NJ, United States, 3BARDS, Merck & Co, Inc, Upper Gwynedd, PA, United States, 4Advanced MRI Technologies, Sebastopol, CA, United States, 5Redwood Regional Medical Group, Santa Rosa, CA, United States, 6Fraunhofer MEVIS-Institute for Medical Image Computing, Bremen, Germany, 7Experimental Medicine, Merck & Co, Inc, Upper Gwynedd, PA, United States, 8Clinical Pharmacology, Merck & Co, Inc, Upper Gwynedd, PA, United States, 9Translational Neurology, Biogen Idec, Cambridge, MA, United States, 10Clinical Research, Merck & Co, Inc, Rahway, NJ, United States

In this contribution we assessed the test-retest reproducibility of 3D GRASE ASL technique at 1.5 T and in populations of AD patients and age matched control. Assessment of measurement reproducibility was done using graphical methods as well as quantitative metrics such as Intraclass Correlation Coefficient and within subject coefficient of variability. Our findings suggest that the test-retest reproducibility varies between ROIs, and overall moderate to very good reproducibility can be achieved. Assessment of reproducibility is an important first step to inform design (e.g. parallel versus cross-over) of future studies of disease progression and treatment effect.

14:00 4008.   A Comparison Study of Imaging Absolute CBF Change in Rat Brain with SR-T1app method and CASL technique 
Xiao Wang1, Xiao-hong Zhu1, Yi Zhang1, and Wei Chen1
1Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, MN, United States

In the present study, the absolute CBF increase induced by transient mild hypercapnia in the rat brain was directly compared using the SR-T1app method and the CASL technique. The results revealed good agreement in both magnitude and spatial patterns of CBF change measured by these two techniques. In addition, both techniques showed great sensitivity to the variation of hypercapnia level and the associated CBF change. Our results also show that the SR-T1app method could also provide absolute CBF value once the intrinsic R1 (R1int) was determined. Therefore, the SR-T1app method should provide a noninvasive, simple and efficient way to determine both absolute CBF and CBF change induced by physiological and pathological perturbations in the rat brain.

14:30 4009.   Intersubject variability in cerebral blood flow is great than structural variability 
Yufen Chen1, Hengyi Rao1, and John A. Detre1
1Center for Functional Neuroimaging, University of Pennsylvania, Philadelphia, PA, United States

Cerebral blood flow (CBF) is tightly coupled to brain metabolism and is known to be modulated by age and gender. But little is known about intersubject variability in CBF, which may be reflective of individual phenotypic differences. Here, we retrospectively analyzed arterial spin labeling (ASL) data from 136 subjects to test the hypothesis that metabolic variance exceeds structural variance. F-tests showed gray matter (GM) CBF had higher variance than GM volume. Linear model of age and gender showed reduced R2 fit to GM CBF compared to GM volume, suggesting the presence of additional sources of variability.

15:00 4010.   An Online Shared Database of ASL-based CBF Measures with Integrated Processing Pipeline 
David Dongsuk Shin1, Burak Ibrahim Ozyurt2, and Thomas T Liu1
1Center for Functional MRI, University of California, San Diego, La Jolla, CA, United States, 2Department of Psychiatry, University of California, San Diego, La Jolla, CA, United States

A rapidly growing number of CBF measures are being collected both in clinical and research settings around the world. Here we present an online CBF database with an integrated analysis pipeline for CBF quantification (CBFDAP). To date, we have successfully processed and accumulated several hundred CBF datasets acquired with FAIR and OptPCASL protocols for a range of subject populations. The number of datasets is expected to grow rapidly as we begin to make the CBFDAP available to the general public. The CBFDAP provides an infrastructure for the easy upload, processing, storage, retrieval, and exploration of ASL-based CBF data.