Quantification of rodent cerebral blood flow (CBF) in normal and high flow states using pulsed arterial spin labeling magnetic resonance imaging.
OBJECTIVE
To 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.


METHODS
Wistar 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.


RESULTS
The 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.


CONCLUSIONS
Even when flow is accelerated, CBF can be accurately determined using pulsed ASL, as long as dt and outflow of the tag are accounted for.
Wegener
Susanne
S
Department of Radiology, University of California San Diego, San Diego, California, USA.
Wu
Wen-Chau
WC
Perthen
Joanna E
JE
Wong
Eric C
EC
D000818:Animals; D001158:Arteries / Q000473:pathology*; D001776:Blood Circulation Time; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000737:chemistry; D002560:Cerebrovascular Circulation; D006863:Hydrogen-Ion Concentration; D006935:Hypercapnia / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008956:Models, Chemical; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D002245:Carbon Dioxide