SIMULTANEOUS MEASUREMENT OF PERFUSION AND OXYGENATION CHANGES USING AMULTIPLE GRADIENT-ECHO SEQUENCE - APPLICATION TO HUMAN MUSCLE STUDY

We have developed a magnetic resonance imaging (MRI) technique based o n a multiple gradient-echo sequence designed to probe perfusion and ox ygenation simultaneously within skeletal muscle. Processing of the ima ges acquired at successive echo times (TEs) generates two functional m aps: one of the signal intensity (SI) extrapolated to zero echo time, which is sensitive to perfusion; and a second one of R2, which reflec ts oxygenation. An advantage of the processing procedure lies in the s election of tissue of interest through the profile of T-2 decay, lead ing to automatic rejection of pixels containing small vessels. This al lows a more specific assessment of tissue perfusion and oxygenation. T his technique was demonstrated successfully during post-ischemic react ive hyperemia in human calf, A perfusion peak of 123 mL x 100 g(-1) x min(-1) was measured immediately after ischemia, whereas R2 value sho wed an 11.5% decrease at the same time, essentially reflecting blood o xygenation changes. Differences in the time courses of reperfusion and re-oxygenation were observed, oxygenation presenting a slower recover y. The mechanisms responsible for such a differential dynamic response are discussed. (C) 1998 Elsevier Science Inc.