Perfusion‐based high‐resolution functional imaging in the human brain at 7 Tesla

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Abstract
Perfusion‐based MRI measures cerebral blood flow (CBF) at the capillary level and can be used for functional studies based on the tight spatial coupling between brain activity and blood flow. Obtaining functional CBF maps with high spatial resolution is a major challenge because the CBF signal is intrinsically low and the SNR is critical. In the present work, CBF‐based functional imaging was performed at a considerably smaller voxel size than previously reported in humans. High‐resolution CBF maps were obtained with voxel sizes as small as 0.9 × 0.9 × 1.5 mm3 in the human brain. High sensitivity was made possible by signal‐to‐noise gains at the high magnetic field of 7 T and by using a novel RF combination coil design. In addition, a reduction of the field‐of‐view was critical to achieve 0.9‐mm in‐plane resolution with gradient‐echo echo‐planar imaging in a single shot. Functional CBF data were compared with functional BOLD data to reveal that, for CBF, large contrast‐ to‐noise gains were obtained at high spatial resolution, indicating that the functional CBF response was more localized. High‐resolution functional CBF imaging is significant for neuroscience research because it provides better localization and more specific information than BOLD for monitoring brain function. Magn Reson Med 47:903–911, 2002.