| Perfusion & Diffusion: Animal Models |
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Thursday 23 April 2009 |
| Room 312 |
16:00-18:00 |
Moderators: |
Josette Chen and Afonso C. Silva |
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16:00 |
739. |
Hybrid Diffusion Imaging (HYDI)
in a Brain Model of Dysmyelination |
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Yu-Chien Wu1,2,
Andrew L. Alexander2, Ian D. Duncan3,4,
Aaron S. Field4,5
1Radiology , University of Wisconsin-Madison,
Madison, WI, USA; 2Waisman Laboratory for
Brain Imaging & Behavior, University of
Wisconsin-Madison, Madison, WI, USA; 3Medical
Science, University of Wisconsin-Madison, Madison,
WI, USA; 4Radiology, University of
Wisconsin-Madison, Madison, WI, USA; 5Biomedical
Engineering, University of Wisconsin-Madison,
Madison, WI, USA |
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Fractional anisotropy
(FA) in the diffusion tensor imaging (DTI) is
commonly used as a measure of white matter (WM)
integrity. However, FA is also highly sensitive to
such factors as non-Gaussian diffusion, crossing
fibers and imaging noise, which may degrade its
specificity. It has recently been proposed that the
radial diffusivity is highly related to WM
myelination. Alternatively, PDF measures in the
diffusion spectrum imaging (DSI), e.g. Po and MSD,
may provide additional information about WM
microstructure. In this longitudinal study, the
dysmyelinating shaking pup model was studied using
both the DTI and DSI acquired from a hybrid
diffusion imaging. |
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16:12 |
740. |
Untangling a Fiber Bundle Knot
- Preliminary Results on STN Connectivity Using DTI
and HARDI on Rat Brains |
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Ellen Brunenberg1,
Vesna Prckovska1, Bram Platel2,
Gustav Strijkers1, Bart ter Haar Romeny1
1Biomedical Engineering, Eindhoven University
of Technology, Eindhoven, Netherlands; 2Biomedical
Engineering, University Hospital Maastricht,
Maastricht, Netherlands |
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Deep Brain Stimulation
of the subthalamic nucleus (STN) for Parkinson’s
Disease improves the motor function, but cognitive
and emotional side effects occur. These can be
minimized by an accurate location of the STN motor
part, analyzing the connections with other brain
areas. In this study, we compare DTI and HARDI
glyphs around the rat STN. The HARDI glyphs are more
heterogeneous than the mostly oblate DTI glyphs. We
observe crossings in the lateral STN, while a linear
configuration can be seen medially. We may thus
distinguish the lateral motor part and the medial
cognitive/emotional part of the rat STN. |
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16:24 |
741. |
Diffusion Tensor Imaging and
Micro-Computed Tomography Based Three Dimensional
Stereotaxic Atlas of the Adult C57BL/6J Mouse Brain
Corrected for Postmortem Tissue Deformation |
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Manisha Aggarwal1,
Jiangyang Zhang2, Michael I. Miller1,3,
Susumu Mori2,4
1Department of Biomedical Engineering, Johns
Hopkins University School of Medicine, Baltimore,
MD, USA; 2Department of Radiology, Johns
Hopkins University School of Medicine, Baltimore,
MD, USA; 3Center of Imaging Science,
Johns Hopkins University, Baltimore, MD, USA; 4F.
M. Kirby Research Center for Functional Brain
Imaging, Kennedy Krieger Institute, Baltimore, MD,
USA |
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A microCT and DTI based
three dimensional stereotaxic atlas of the adult
C57BL/6J mouse brain was developed, with correction
of postmortem tissue distortion due to specimen
fixation. A population-averaged in vivo MRI
brain template was developed with estimates of
anatomical variability, and was used as the
reference for nonlinear deformation of the ex vivo
data, to generate a distortion-corrected DTI atlas
with high anatomical fidelity. The
distortion-corrected DTI atlas was incorporated into
the stereotaxic coordinate frame. Compared to
existing histology based atlases, the distortion
corrected microCT-DTI atlas provides a more accurate
representation of the adult C57BL/6J brain anatomy. |
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16:36 |
742. |
Mild Hypoxic-Ischemic Injury
in the Neonatal Rat Brain: Longitudinal Evaluation
of the White Matter Using Diffusion Tensor MR
Imaging |
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Silun Wang1,
Ed. X. Wu2,3, Kexia Cai2,3,
Ho-Fai Lau2,3, Pek-Lan Khong1
1Department of Diagnostic Radiology, The
University of Hong Kong, Hong Kong, Hong Kong;
2Laboratory of Biomedical Imaging and Signal
Processing, The University of Hong Kong, Hong Kong;
3Department of Electrical and Electronic
Engineering, The University of Hong Kong |
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We evaluated
longitudinally mild hypoxic-ischemic (HI) induced
white matter (WM) damage in a neonatal rat model
using DTI and correlated the DTI indices with
histological evaluations. Results showed
significantly decreased FA and increased ¦Ë¡Í in the
injured WM reflected dysmyelination. The
longitudinal changes of increasing FA, decreasing ¦Ë¡Í,
and no change in ¦Ë// in both injured and control WM
suggests continued myelination. Furthermore,
differences in FA and ¦Ë¡Í between injured and
control WM decreased longitudinally. Our results
demonstrated that mild HI induced WM damage
continues to mature with partial recovery post-HI,
and this could be reflected by DTI in vivo. |
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16:48 |
743. |
Diffusion Weighted Magnetic
Resonance Imaging of Neuronal Activity in the
Hippocampal Slice Model |
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Brian Hansen1,
Jeremy Flint2,3, Peter
Vestergaard-Poulsen1, Stephen J.
Blackband2,3
1Center of Functionally Integrative
Neuroscience, University of Aarhus, Aarhus, Denmark;
2Department of Neuroscience, University
of Florida, Gainesville, FL, USA; 3The
McKnight Brain Institute, University of Florida,
Gainesville, FL, USA |
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Functional magnetic
resonance imaging (fMRI) has become the leading
modality for studying the working brain but the
spatiotemporal resolution of the method is somewhat
limited. Therefore, alternative MR-based methods for
detection of brain activity have been proposed and
investigated. Studies have reported functional
imaging based on diffusion weighted (DW) MRI. The
basis for such DW fMRI is believed to be the
sensitivity of DW MRI to changes in tissue
micro-structure. However, it remains unclear whether
the observed signal changes reflect cell swelling
related to neural activation, residual vascular
effects, or a combination of both. Here we present
evidence of a detectable activity related change in
the diffusion weighted MR-signal from the cellular
level in live hippocampal slices in the absence of
vasculature. Slices are exposed to several
substances and the effects evaluated and compared. |
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17:00 |
744. |
DKI Visualizes Hippocampal
Alterations in the Chronic Mild Stress Ratmodel |
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Rafael Delgado y
Palacios1, Marleen Verhoye1,2,
Johan Van Audekerke1, Dirk Poot2,
Jan Sijbers2, Ove Wiborg3,
Annemie Van der Linden1
1Bio-Imaging Lab, University of Antwerp,
Antwerp, Belgium; 2Vision Lab, University
of Antwerp, Antwerp, Belgium; 3Centre for
Basic Psychiatric Research, Aarhus Psychiatric
University Hospital, Aarhus, Denmark |
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Depression is a serious
and disabling disorder. However, the exact
pathophysiology of depression is not clearly
understood. The chronic mild stress ratmodel is a
well established animal model. In the hippocampus
and the corpus callosum and capsula externa of this
model, we used diffusion kurtosis imaging (DKI) as a
measure of tissue’s microstructure. We found changes
in the hippocampus of mean and radial kurtosis in
the CMS rats in comparison with control rats,
suggesting possible stress-induced CA3 apical
dendrite atrophy, dendritic regression in granule
and CA1 pyramidal cells and reduction of mossy fiber
terminals volume and surface area. |
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17:12 |
745. |
Myocardial Remodeling in
Chronic Porcine Model: A DT-MRI Study Using the
Toroid-Based Representation |
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Choukri Mekkaoui1,
Marcel P. Jackowski2, Donald P. Dione1,
Francis G. Spinale3, Albert J. Sinusas1
1Yale University, New haven, CT, USA; 2University
of Sao Paulo, Brazil; 3Medical University
of South Carolina, USA |
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The toroid-based
representation of MR diffusion tensor fields was
used to investigate structural and fiber angle
remodeling at 2- and 8-weeks post-MI compared to
normal hearts. Toroidal DT-MRI indices provide a
means for a non-destructive, regional quantification
of hearts post-MI. Results suggest that structural
changes attributed to left ventricular (LV)
remodeling involve both the infarcted and non-infarcted
LV myocardium. The ongoing tissue reorganization
process is underscored by a concomitant alteration
in diffusivity, anisotropy and myocardial fiber
inclination in the remote territory between 2- and
8-weeks post-MI. The toroid-based parameters
revealed a structural dynamic modification as a
function of time post-MI. |
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17:24 |
746. |
In-Vivo Hadamard
Encoded Continuous Arterial Spin Labelling (H-CASL)
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Jack A. Wells1,2,
Mark F. Lythgoe2,3, David Gadian2,
Roger Ordidge1, David L. Thomas1
1Advanced MRI Group, University College
London, London, UK; 2RCS Unit of
Biophysics, UCL Institute of Child Health, London,
UK; 3Centre for Advanced Biomedical
Imaging, University College London, London, UK |
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Recently, Hadamard
encoding techniques have been applied to the CASL
labelling pulse to efficiently image small boli of
tagged arterial blood water at a range of post-labelling
delay times. In this study we demonstrate that this
method can be successfully applied in-vivo to
accurately measure cerebral blood flow and arterial
transit time (äa) in the rat brain. We have modified
the ASL quantification model to take account of the
new encoding approach that can measure the first
inflow of labeled blood into the tissue. We
demonstrate an improvement in the precision of the
äa estimates compared to the standard method. |
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17:36 |
747. |
Vessel Size Imaging with Iron
Oxide and with Gadolinium: A Comparative Study in
Rodent |
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Nicolas Pannetier1,2,
Benjamin Lemasson3,4, Thomas Christen1,2,
Régine Farion1,2, Christoph Segebarth1,2,
Chantal Remy1,2, Emmanuel Luc Barbier1,2
1Inserm, U836, Grenoble, F-38043, France;
2 Université Joseph Fourier, Grenoble Institut
des Neurosciences, UMR-S836, Grenoble, F-38043,
France; 3Oncodesign Biotechnology, Dijon,
France; 4 Inserm, U836, Grenoble,
F-38043, France |
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Vessel Size Index (VSI)
is a powerful tool for characterizing tumor vessel
diameters and their evolution under therapy. VSI has
been obtained either using a Gd-bolus or at
steady-state using iron oxide particles. In this
study we compared the VSI obtained with Gd and with
iron using either a dynamic approach (first passage)
or a steady state approach. Data were acquired in
rats bearing a glioma model. The case of Gd-loaded
tumor was also considered. This study suggests that
monitoring the first passage of a Gd-bolus with a
double-echo EPI sequence is well suited to assess
VSI in humans. |
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17:48 |
748. |
Gd-DTPA-Enhanced MRI Revealed
Leakage at Aqueous-Vitreous Interface Upon Ocular
Hypertension |
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Kevin C. Chan1,2,
Qing-ling Fu3, Kwok-fai So3,
Ed X. Wu1,2
1Laboratory of Biomedical Imaging and Signal
Processing, The University of Hong Kong, Hong Kong
SAR, China; 2Department of Electrical and
Electronic Engineering, The University of Hong Kong,
Hong Kong SAR, China; 3Department of
Anatomy, The University of Hong Kong, Hong Kong SAR,
China |
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This study aims to
employ in vivo contrast-enhanced MRI to
evaluate the ocular transport upon an induction of
ocular hypertension in the right eye in a rat model
of chronic glaucoma. Following systemic
administration of Gd-DTPA solution, our results
showed a progressive T1-weighted signal increase in
the anterior vitreous body of the glaucomatous eye
but not the control eye, suggestive of the leakage
of Gd-DTPA at the aqueous-vitreous interface. These
findings may explain the sources of changing
biochemical compositions in the glaucomatous chamber
components, which may implicate the cascades of
neurodegenerative processes in the retina and the
optic nerve. Our findings of the early Gd-DTPA
signal enhancements in the anterior vitreous body
than the preretinal vitreous provided a noninvasive
marker for the disease. More importantly, this
approach could have direct clinical applications and
can be readily translated to humans. |
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