High-resolution Diffusion-weighted Magnetic Resonance Imaging: Development and Application of Novel Radial Fast Spin-echo Acquisitions

by Sarlls, Joelle Elita.

Diffusion-weighted Magnetic Resonance Imaging (DWI) has become a useful tool in medicine for the purpose of diagnosis, tracking disease progression, and monitoring response to therapy. The current techniques used for DWI suffer from artifacts due to magnetic field inhomogeneities, image distortion, and low spatial resolution. The aim of the presented work is to advance DWI by improving upon and developing novel highresolution acquisition techniques. The approach taken for this purpose was to utilize radial fast spin-echo data acquisitions, which have been shown to produce high-resolution DWI without artifacts due to magnetic field inhomogeneities. In addition, there is little image distortion in radial fast spin-echo DWI, which allows for direct overlay onto anatomical MRI. However, a draw back is that radial methods require longer scan times. By increasing the imaging speed of existing radial fast spin-echo acquisitions, it may become a more practical clinical tool. In addition, novel acquisition techniques are developed that push high-resolution to all three dimensions. By employing a threedimensional radial fast spin-echo acquisition, voxels in an image have equal size in each dimension and can be on the order of 1mm 3. By decreasing the voxel size, the tissue contained within a voxel is more homogeneous. This is important for DWI applications that aim to measure the microscopic integrity of the tissue. The development and analysis of the novel radial fast spin-echo techniques are presented in this work along with several clinical applications. The remaining issues to be addressed for application to quantitative DWI measures are also presented, along with possible solutions. 12