A joint project of the Graduate School, Peabody College, and the Jean & Alexander Heard Library

Title page for ETD etd-07222011-161620

Type of Document Dissertation
Author Wargo, Christopher Joseph
Author's Email Address chris.wargo@vanderbilt.edu
URN etd-07222011-161620
Title High Resolution MRI of the Human Brain Using Reduced-FOV Techniques at 7 Tesla
Degree PhD
Department Biomedical Engineering
Advisory Committee
Advisor Name Title
John Gore Committee Chair
Adam Anderson Committee Member
Brian Welch Committee Member
Seth Smith Committee Member
Victoria Morgan Committee Member
  • Reduced-FOV
  • High Resolution
  • Human Brain
  • MRI
  • 7 Tesla
  • Human DTI
  • Hippocampus MRI
  • Cervical Spinal Cord
Date of Defense 2011-07-12
Availability unrestricted
Achieving micron resolutions in magnetic resonance imaging is constrained first by limitations in available signal strength as voxel sizes decrease, and second, by acceptable acquisition times due to the large data sets required. The latter is problematic due to an increased sensitivity to patient bulk motion and physiological effects, and prevalence of distortion and blurring artifacts caused by susceptibility variation. Signal constraints can be mitigated using ultra-high field strengths, such as 7T, but face field dependent challenges such as increased B1 inhomogeneity and shorter T2* values. Scan times can be minimized using reduced field-of-view (FOV) imaging techniques that localize excitations to smaller regions of an object to achieve diminished imaging dimensions, but have largely been unexplored at 7T.

To address this deficiency with the goal of improving human imaging resolutions, this thesis first implements and compares multiple reduced-FOV methods at 7T, assessing relative ability to localize excitation, suppress unwanted signal, minimize artifacts, and constrain power deposition. Inner-Volume Imaging (IVI) and Outer-Volume Suppression (OVS) methods optimized from this comparison are then synergistically combined with rapid parallel and echo planar imaging (EPI) techniques to obtain 160 to 500 μm2 in vivo images throughout the human brain in 3 to 12 minutes, accelerated 160 to 1400 fold for multi-slice and 3D scans, respectively. Compared to full-FOV scans, this approach demonstrates reduced geometric distortion and motion artifacts, with improved visibility of features at the high resolution. The parallel reduced-FOV method is similarly applied for diffusion tensor and cervical spine imaging prone to motion and susceptibility artifacts to obtain 1mm2 DTI images and 300 μm2 in the spine, with localized measurement of diffusion properties. Overall, the reduced-FOV approach provides reduction in scan times, artifact minimization, and achieves resolutions that exceed prior studies.

  Filename       Size       Approximate Download Time (Hours:Minutes:Seconds) 
 28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access 
  PhD_Thesis_Wargo_2011.pdf 39.26 Mb 03:01:46 01:33:28 01:21:47 00:40:53 00:03:29

Browse All Available ETDs by ( Author | Department )

If you have more questions or technical problems, please Contact LITS.