Diffusion Tensor MR Spectroscopic Imaging

Diffusion tensor imaging (DTI) characterization of white matter microstructure abnormalities in autism spectrum disorder (ASD) generally demonstrate decreased water diffusion anisotropy in frontal cortex and corpus callosum, consistent with frontal disconnectivity theories of autism. However, DTI findings in ASD show considerable heterogeneity and little is known about differential involvement of the intracellular and extracellular compartments or mechanisms underlying changes in water diffusion that limit the extent to which DTI can be used to characterize developmental processes in ASD. Diffusion tensor 1H MRSI (DTSI) can provide unique information on intracellular properties, such as viscosity, cell swelling, restriction in subcellular structures and cytoplasmic streaming, that may help to characterize possible inflammatory processes in autism. All human studies so far have used single voxel localization method (e.g. Posse et al 1993a, Ellegood et al 2005 and 2006, Upadhyay et al 2007) due to overwhelming motion sensitivity of conventional MRSI techniques (Posse et al. 1993b), which do not allow mapping of metabolite diffusion across extended brain areas hypothesized to be involved in autism.

The objective of this project is to develop single-shot diffusion sensitive MRSI to dramatically reduce motion sensitivity, and to show feasibility of volumetric mapping of metabolite diffusion in healthy adults and children with ASD using a clinical 3 Tesla whole body scanner.