Jun-Cheng Weng1, 2, Fatima Ali Nasrallah3, Kai-Hsiang Chuang3
1School of Medical Imaging and Radiological Sciences, Chung Shan Medical University, Taichung, Taiwan; 2Department of Medical Imaging, Chung Shan Medical University Hospital, Taichung, Taiwan; 3MRI Group, Singapore Bioimaging Consortium, A*STAR, Singapore, Singapore
Diffusion MRI is a technique for studying various aspects of microscopic tissue composition and organization in the central nervous system (CNS). The diffusion time is a key parameter to determine restricted diffusion in microstructures and hence the sensitivity of diffusion MRI to different spatial dimensions. However, it is not straightforward to implement pulsed gradient spin echo (PGSE) diffusion experiments with short diffusion times that are needed to highlight structures at microscopic scales. One alternative is to use oscillating gradient spin echo (OGSE) or the so-called temporal diffusion spectroscopy, which allows short diffusion time better than PGSE sequence, to provide a unique way to measure water diffusion. Diffusion spectrum imaging (DSI) is one of the diffusion MRI techniques that can map complex fiber architecture in the brain. We sought to apply OGSE DSI to identify minuscule neuroarchitecture in the brain. By applying oscillating diffusion-sensitive magnetic gradients to tag translational motion of water molecules, 3D probability density function (PDF) of molecular displacement can be reconstructed from the measured OGSE DSI data. For comparison, diffusion tensor images (DTI) of the rat brain were acquired using the OGSE and PGSE sequences. We demonstrate DSI maps with oscillating gradient revealed novel tissue contrast in the rat hippocampus.