QUANTITATIVE MEASUREMENTS OF CEREBRAL BLOOD-FLOW IN RATS USING THE FAIR TECHNIQUE - CORRELATION WITH PREVIOUS IODOANTIPYRINE AUTORADIOGRAPHIC STUDIES

Flow-sensitive alternating inversion recovery (FAIR) is a recently int roduced MRI technique for assessment of perfusion that uses blood wate r as an endogenous contrast agent. To characterize the FAIR signal dep endency on spin tagging time (inversion time (TI)) and to validate FAI R for cerebral blood flow (CBF) quantification, studies were conducted on the rat brain at 9.4 T using a conventional gradient-recalled echo sequence. The T-1 of cerebral cortex and blood was found to be 1.9 an d 2.2 s, respectively, and was used for CBF calculations. At short TIs (<0.8 s), the FAIR signal originates largely from vascular components with fast flows, resulting in an overestimation of CBF. For TI > 1.5 s, the CBF calculated from FAIR is independent of the spin tagging tim e, suggesting that the observed FAIR signal originates predominantly f rom tissue/capillary components. CBF values measured by FAIR with TI o f 2.0 s were found to be in good agreement with those measured by the iodoantipyrine technique with autoradiography in rats under the same c onditions of anesthesia and arterial pCO(2). The measured pCO(2) index on the parietal cortex using the FAIR technique was 6.07 ml/100 g/min per mmHg, which compares well with the pCO(2) index measured by other techniques. The FAIR technique was also able to detect the regional r eduction in CBF produced by middle cerebral artery occlusion in rats.