• Susanne Wegener, Wen-Chau Wu, Joanna E Perthen, and Eric C Wong.
• Department of Radiology, University of California San Diego, San Diego, California, USA.
• J Magn Reson Imaging. 2007 Oct 1; 26 (4): 855-62.

PurposeTo implement a pulsed arterial spin labeling (ASL) technique in rats that accounts for cerebral blood flow (CBF) quantification errors due to arterial transit times (dt)-the time that tagged blood takes to reach the imaging slice-and outflow of the tag.Materials And MethodsWistar rats were subjected to air or 5% CO(2), and flow-sensitive alternating inversion-recovery (FAIR) perfusion images were acquired. For CBF calculation, we applied the double-subtraction strategy (Buxton et al., Magn Reson Med 1998;40:383-396), in which data collected at two inversion times (TIs) are combined.ResultsThe ASL signal fell off more rapidly than expected from TI = one second onward, due to outflow effects. Inversion times for CBF calculation were therefore chosen to be larger than the longest transit times, but short enough to avoid systematic errors caused by outflow of tagged blood. Using our method, we observed a marked regional variability in CBF and dt, and a region dependent response to hypercapnia.ConclusionEven when flow is accelerated, CBF can be accurately determined using pulsed ASL, as long as dt and outflow of the tag are accounted for.(c) 2007 Wiley-Liss, Inc.

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