High Resolution Brain Imaging
Friday 7 May 2010
Room A1 10:30-12:30 Moderators: Joseph J.H. Ackerman and Essa Yacoub

10:30 684. 

T2-Weighted MRI Visualizes Cortical Layers in Living Mice
Susann Boretius1, Anastasia Stoykova2, Roland Tammer1, Thomas Michaelis1, Jens Frahm1

1Biomedizinische NMR Forschungs GmbH, Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany; 2Molekulare Zellbiologie, Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany

The delineation of cortical layers in living animals is of major interest for a variety of questions ranging from developmental biology to studies of genetic alterations. Here, high-resolution T2-weighted MRI at 9.4 T is demonstrated to detect layer-like structures in mouse brain in vivo, which at least in part correspond to the histologically defined 6-layer structure of mammalian cortex. For the first time age-related cortical differences in healthy mice and severe alterations in layer architecture in cortex-specific Pax6 conditional knockout mice are visualized by in vivo MRI.

10:42 685. 

Magnetic Susceptibility Anisotropy of Central Nervous System
Chunlei Liu1,2
Brain Imaging and Analysis Center, Duke University, Durham, NC, United States; 2Radiology, Duke University, Durham, NC, United States

Magnetic susceptibility difference between gray and white matter results in strong phase contrast at high magnetic field strength. We report, for the first time, a surprising observation of tissue-level magnetic susceptibility anisotropy in central nervous system (CNS). Specifically, we found that susceptibility of the white matter exhibits strong orientation dependence. Such orientation variation is extensive throughout the white matter area, but is relatively weak in the gray matter. We anticipate that imaging this anisotropy will provide a unique contrast that is unknown previously.  In addition, it will provide a novel tool to further quantify the substructures of the CNS.

10:54 686. 

Reliable Cortical Thickness Estimation with Reduction of Susceptibility-Induced Signal Loss Using Optimized T1-Weighted Single-Slab 3D Turbo Spin Echo Pulse Sequence
Hyunyeol Lee1, Eung Yeop Kim2, Jin-Suck Suh2, Jaeseok Park2
Medical Science, Yonsei University, Seoul, Seodaemun-gu, Korea, Republic of; 2Radiology, Yonsei University

MP-RAGE, currently has gained popularity in volumetric studies, is highly influenced by susceptibility-indeced magnetic field inhomogeneities, yielding signal losses or image distortions. In this work, we investigated the feasibility of the optimized sinlge-slab 3D fast/turbo spin echo imaging for the accurate measurement of cortical thickness. Our Results demonstrated that the proposed method alleviated susceptibility-induced problems, and thereby yielding more reliable volumetric values, as compared to those from conventional MP-RAGE. We concluded that the proposed sequence could be an alternative to conventional MP-RAGE for brain volumetry.

11:06 687.  

The First MRI Detection of Prion Protein Plaques in the Cerebral Cortex in Variant Creutzfeldt-Jakob Disease: Post Mortem MR Microscopy at 9.4 Tesla
Harpreet Hyare1, Po-Wah So2, Caroline Powell1, Thornton John3, Tarek Yousry3, Sebastian Brandner1, Harry Parkes4
MRC Prion Unit, UCL Institute of Neurology, London, United Kingdom; 2Institute of Psychiatry, London, United Kingdom; 3National Hospital for Neurology and Neurosurgery; 4Department of Brain Repair and Rehabilitation, UCL Institute of Neurology, London, United Kingdom

Magnetic resonance microscopy at 9.4T with in plane resolution of 58 microns can depict amyloid plaques composed of the abnormal prion protein in the cortex of patients with vCJD.  Formalin fixed cortical samples, passively stained with gadoteric acid and scanned with a high resolution 3D gradient echo sequence (TR 20, TE 5, 16 averages) demonstrate prion protein (PrP) plaques as hypointense foci in the cortex which correspond to PrP immunostaining.  As high field strength magnets enter clinical practice, in vivo MRI of the cortex may improve diagnosis and monitoring of vCJD.

11:18 688.

MRI Laminar Resolution of the Human Retina
Qi Peng1,2, Yi Zhang2, 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

MRI of the awake human retina is challenging because the thin retina is located in a region of high magnetic susceptibility, is susceptible to eye motion and high resolution is needed. This study successfully demonstrated for the first time MRI anatomical laminar resolution of the in vivo human retina at 3 T. Laminar thicknesses were quantified. Potential challenges, solutions and outlooks for future applications are discussed.

11:30 689

High Resolution 1H MRI of Postmortem Human Brain Sections Performed at 21.1 T
Parastou Foroutan1, Katherine J. Schweitzer2, Dennis W. Dickson3, Daniel F. Broderick4, Uwe Klose5, Daniela Berg6, Zbigniew K. Wszolek2, Samuel C. Grant1
1Chemical & Biomedical Engineering, The Florida State University, Tallahassee, FL, United States; 2Department of Neurology, Mayo Clinic Florida, Jacksonville, FL, United States; 3Department of Neuroscience, Mayo Clinic Florida, Jacksonville, FL, United States; 4Department of Radiology, Mayo Clinic Florida, Jacksonville, FL, United States; 5Department of Radiology, Section for Experimental ZNS Imaging, University hospital Tuebingen, Tuebingen, Germany; 6Hertie Institute for Clinical Brain Research, University of Tuebingen, Tuebingen, Germany

The first MRM evaluations of human tissue (Alzheimer/Parkinson related pathology) at 21.1 T, the highest magnetic field available for MRI, are presented. Quantitative analysis of relaxation proved very sensitive in identifying control versus pathological tissue, while parametric mapping demonstrated the potential for categorizing severity. Generally, neurodegeneration appeared more pervasive than expected, extending well beyond the regions normally considered to be affected by either Alzheimer’s or Parkinson’s disease alone. As a pathological tool, MRM has potential to elucidate the extent and severity of such neurodegeneration, and hopefully, may improve the diagnostic capabilities of MRI as higher magnetic fields become available.

11:42 690

Dependence of R2* Bias on Through-Voxel Frequency Dispersion and Gradient Echo Train in High-Resolution 3D R2* Mapping
Gunther Helms1, Peter Dechent1
1MR-Research in Neurology and Psychiatry, University Medical Center, Göttingen, Lower Saxony, Germany

An empirical model for the influence of through-voxel gradients on log regression of R2* was derived from simulations. This advocates trains of many gradient echoes that start early and are short compared to local frequency dispersion, that is, use of non-selective high-resolution 3D acquisitions. The general trade-off is between statistical error of R2* and sensitivity to bias. For 1mm resolution at 3T, excessive bias can be confined to small orbito-frontal and temporo-basal regions, whereas correction of bias is unreliable. High-resolution R2* mapping of (almost) the whole brain seems feasible.

11:54 691

Visualization of the Subthalamic Nuclei Using High-Resolution Susceptibility Mapping at 7T
Andreas Schäfer1, Birte U. Forstmann2, Jane Neumann1, Robert Turner1
1Max-Planck-Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; 2Department of Psychology, University of Amsterdam, Amsterdam, Netherlands

Deep brain stimulation targeting the subthalamic nucleus (STN) is an important treatment for Parkinson’s disease patients. The STN has been previously visualized at 3T and 7T using T2-weighted imaging, short inversion recovery sequences, phase imaging or susceptibility-weighted imaging, but contrast is inadequate or misleading, and the STN's borders are poorly defined. Here we used high-resolution phase imaging at 7T to calculate susceptibility maps of the STN and its surrounding areas. These show far clearer visualization of the STN, with excellent discrimination from the adjacent substantia nigra.

12:06 692.

Assessment of Motion and F0 Artifacts in 7T High Resolution T2*-Weighted Imaging in Alzheimer’s Disease Patients, and Application of a Navigator-Based Correction Scheme
Maarten J. Versluis1,2, Johannes M. Peeters3, Sanneke van Rooden1,2, Jeroen van der Grond1, Mark A. van Buchem1, Andrew G. Webb1,2, Matthias J. van Osch1,2
1Radiology, Leiden University Medical Center, Leiden, Netherlands; 2CJ Gorter Center for High Field MRI, Leiden University Medical Center, Leiden, Netherlands; 3Philips Healthcare, Best, Netherlands

Image quality is decreased substantially in 7T high resolution T2*-weighted images in Alzheimer’s disease (AD) patients compared to younger volunteers. The source of the image artifacts was investigated in phantom experiments using translational/rotational motion parameters and f0 fluctuations from AD patients. It was found that image degradation by f0 fluctuations was a factor-of-four times larger than artifacts caused by movement typical of AD patients. By implementing a navigator echo correction for f0 fluctuations, the image quality increased considerably. This technique was succesfully applied in four AD patients showing significant image quality improvements.

12:18 693

Phase-Based Regional Oxygen Metabolism (PROM) at 3T and Feasibility at 7T
Audrey Peiwen Fan1, Thomas Benner2, Divya S. Bolar3, Bruce R. Rosen2,3, Elfar Adalsteinsson, 1,3
1Electrical Engineering and Computer Science, MIT, Cambridge, MA, United States; 2Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States; 3Health Sciences and Technology, Harvard-MIT, Cambridge, MA, United States

The cerebral metabolic rate of oxygen (CMRO2) is an important indicator for brain function and disease, including stroke and tumor.  CMRO2 can be quantified from measurements of venous oxygen saturation (Yv) and cerebral blood flow (CBF) in cerebral veins.  Bulk susceptibility measurements based on gradient-echo phase maps has been used to estimate Yv in vivo at 3T. Challenges of this technique include partial volume effects, phase wrapping, and background susceptibility gradients.  Here we combine phase-based measurements of Yv with ASL measurements of CBF to quantify CMRO2 in cerebral vessels at 3T.  Further, we extended estimates of Yv to 7T, achieving a 1/5 reduction in voxel size.  The improved spatial resolution allows examination of smaller vessels more indicative of regional brain function.  Future work includes extending the method to estimate CMRO2 at 7T.



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