| Two methods for measuring blood perfusion using magnetic resonance techniques are described in this dissertation. One method, a volume localized NMR measurement of regional cerebral blood flow (rCBF), was validated in rat experiments using radioactive microspheres. The second technique, only suitable for animal experiments, involved the use of paramagnetic particles as a magnetic analog of the "gold-standard" radioactive microspheres.; Detre et al (1992) have recently demonstrated a technique for the measurement of regional cerebral blood flow (rCBF) based on the continuous saturation (or inversion) of the arterial blood supply to the brain in rats at 4.7T. In the work reported here, we combined this technique with volume localized (PRESS) readouts to benefit from recording "perfusion" signals averaged over a larger volume, resulting in rapid acquisition of data with sufficient signal-to-noise ratio for application at 2.0T. The experiments described here were performed without the use of a decoupler for delivering saturation pulses. The technique was validated using radioactive microspheres in rats, under normal, hypercapnic, and occluded flow conditions. Hypercapnia experiments (5% CO{dollar}sb2){dollar} resulted in a mean measured increase of 143 {dollar}pm{dollar} 95% (10 measurements in 5 animals). Quantitative validation with radioactive microspheres indicated a mean error of {dollar}-1.5pm 15.2{dollar}% for baseline measurements, with significant underestimation noted during occlusion of the right hemisphere flow, and during hypercapnia. These results indicate that a reasonable accuracy could be obtained for measuring cerebral perfusion in rats without the use of exogenous tracers.; The magnetic microsphere experiment, using filtered {dollar}rm Fesb3Osb4{dollar} indicated the ability, when using electron spin resonance (ESR), to measure left/right and grey/white perfusion ratios with paramagnetic particles lodged in the vasculature. These particles also demonstrated an effect on conventional spin-echo images. Ideal particle properties for future work are discussed. |
