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The B1 field and variability in left-right brain perfusion with 3-D IR-PULSAR and its implications in symmetry studies

Wednesday, October 26, 2011 — Poster Session III

10:00 a.m. – Noon

Natcher Conference Center




  • J Butman
  • N Gai


Brain perfusion asymmetry is thought to be associated with Alzheimer’s, schizophrenia and other cerebrovascular diseases. To a radiologist interpreting brain images, particularly those images that are either purely qualitative or only semi-quantitative (eg, cerebral blood flow (CBF) maps), left-right asymmetry serves a critically important function as a visual cue to the presence of pathology. The ability to assess inter-hemispheric symmetry in the human brain with precision is therefore of importance. Arterial spin labeling has now found routine clinical relevance. Earlier, we had described a non-segmented 3-D EPI acquisition method based on the PULSAR technique which provides whole brain CBF values in about five min. Here we study the effect of B1 field inhomogeneity on the spin labeling method and show that correcting for transmit and receive field B1 inhomogeneity is essential before any inferences can be made based on CBF values particularly related to perfusion asymmetry. The overall asymmetry in normal volunteers decreased with use of dual source transmission for RF excitation (to reduce transmit field inhomogeneity) and by applying the actual flip angle (AFI) method to reduce receive B1 inhomogeneity. Corrected values for asymmetry showed better agreement with values available from PET studies in normal volunteers.

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