Optimization of the Fair Technique for Specific Brain Region Perfusion Studies
Most of the technical development and applications of ASL (arterial spin labeling) imaging have mainly focused on the superior cortical regions of the brain. However, optimal ASL measurements to quantify cerebral blood flow (CBF) in specific brain regions may require optimized parameters, improved techniques, or new imaging schemes based upon physiological or anatomic characteristics of those brain regions. In this thesis, the advantages of this region-targeted approach are demonstrated by performing quantitative perfusion studies of two representative brain regions, the cerebellum in the inferior part of the brain and the hippocampus in the mid-brain. To minimize or eliminate the venous artifacts found in cerebellum perfusion studies using traditional FAIR (flow-sensitive alternating inversion recovery) technique, FAIR ASST (FAIR with active suppression of superior tagging technique), as well as MDS FAIR, (modulated dual saturation pulse trains for FAIR) was developed and compared to PICORE (proximal inversion with a control for off-resonance effects) for quantifying cerebellum perfusion. The data indicate that FAIR ASST yields more robust CBF (cerebral blood flow) measurements. OPTIMAL FAIR (orthogonally-positioned tagging imaging method for arterial labeling of FAIR) was developed and shown to reduce the heterogeneity of within-slice transit time and to minimize partial volume effects, improving quantitative CBF maps for cerebellum and hippocampus. These techniques were optimized and applied to the study of perfusion abnormalities in brain regions important to the study of Gulf War Syndrome. Together with regionally optimized parameters, these ASL methods provide more reliable, efficient, accurate, and artifact-free CBF measurements than methods previously available.