How can perfusion fMRI improve studies of brain areas with high susceptibility from magnetic field inhomogeneities (e.g., orbital frontal cortex)?
Perfusion images with gradient echo acquisitions have reduced susceptibility effect compared to BOLD images because a minimum TE is used. Spin echo sequences can be used for image acquisition in ASL methods, such as spin echo EPI and SPIRAL. Parallel imaging with array coil will further shorten the TE and image acquisition time, and subsequently reduce susceptibility artifact. Echo train and steady state imaging sequences such as FSE and FISP can also be used but generally restricted to single slice. Some specific sequence with reduced susceptibility sensitivity, such as reversed SPIRAL, offers alternative approach for perfusion imaging in orbitofrontal and temporal regions.
