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• High-Resolution Diffusion-Weighted Imaging with Radial Fast Spin-Echo MRI
• Imaging of Neimann-Pick C Disease
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High-Resolution Diffusion-Weighted MRI with Radial Fast Spin Echo MRI

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Diffusion-weighted MRI (DWMRI) allows non-invasive determination of the motional properties of brain water in living tissue. Because the motion of tissue water is sensitive to the cellular architecture and integrity in the tissue, DWMRI can be used to investigate a number of neurological diseases including stroke, cancer and Alzheimer's disease. Conventional DWMRI uses single shot echo planar imaging (SSEPI), which is fast and insensitive to motion, but yields low resolution images and is sensitive to magnetic field inhomogeneities. We have developed a radial fast spin-echo (RAD-FSE) methods that allow DWMRI to be carried out at with high spatial resolution without sensitivty to motion and inhomogeneity. Below are diffusion-weighted images of a healthy volunteer using SSEPI (left) and diffusion-weighted RAD-FSE (right). Note the higher resolution of the RAD-FSE image and the absence of artifact in the temporal lobes.

The most frequent use of DWMRI is in the diagnosis and evaluation of acute stroke. Ischemic tissue affected by a stroke will exhibit a decrease in the apparent diffusion coefficient (ADC) of water and therefore show up as hyperintensity on a DWMRI image. Below are diffusion weighted SSEPI (left) and RAD-FSE (right) images obtained from a stroke patient. The higher resolutoin RAD-FSE image allows better visualization of the stroke in terms of extent and anatomic placement. There are small regions of ischemia that are visible using RAD-FSE that are not visible wtih SSEPI due to the low resolution. Artifacts seen in the temporal lobes in the SSEPI image are not present in the RAD-FSE image.

Diffusion Tensor Imaging (DTI) is an extension of DWMRI that investigates the directionality of water motion in living tissue. The white matter of the brain is a highly anisotropic environment where water motion is unrestricted along the axon but highly restricted perpendicular to it. Because of this, DTI is being applied to study a number of neurodegenerative diseases and myelin disorders. The higher resolution afforded by radial-FSE, compared to conventional SSEPI, allows smaller regions of anisotropy to be measured. Below are SSEPI and DIFRAD-FSE anisotropy maps in human brain. In these maps, the eigenvalues of the diffusion tensor in the right-left, anterior-posterior and superior inferior directions have been multiplied by red, green and blue, respectively. Isotropic diffusion will show up in grayscale(white to black).

This work has been funded by NIH grant R21 RR14274 and the FLINN Foundation.

Relevant Publications
Trouard et al. High-resolution diffusion imaging with DIFRAD-FSE (diffusion-weighted radial acquisition of data with fast spin-echo) MRI. Magn Reson Med. 1999
Theilmann et al. View-ordering in radial fast spin-echo imaging. Magn Reson Med. 2004
Sarlls et al. Isotropic diffusion weighting in radial fast spin-echo magnetic resonance imaging. Magn Reson Med. 2005
Gmitro et al. Radial GRASE: implementation and applications. Magn Reson Med. 2005