MAGNETIC-RESONANCE MEASUREMENT OF BLOOD-FLOW IN PERIPHERAL VESSELS AFTER ACUTE EXERCISE

Velocity-encoded Cine magnetic resonance imaging (MRI) was used to mea sure blood flow in the anterior tibial artery (AT), posterior tibial a rtery (PT), and popliteal artery of adult human subjects (mean age 29 yr) before and after 90 s of ankle dorsiflexion exercise. Before exerc ise, mean flow, peak systolic velocity, and end-diastolic velocity in AT were 8.1 +/- 1.6 (SE, n = 6) ml/min, 26.9 +/- 2.6 cm/s, and -0.6 +/ - 0.4 cm/s, respectively. After exercise, mean flow and peak systolic velocity in AT increased by 19-fold and 3-fold, respectively, and end- diastolic velocity increased to 8.7 +/- 1.1 cm/s. Flow in popliteal ar tery above its bifurcation was similar to the sum of flows in AT and P T, both before and after exercise. Flow in AT declined exponentially a fter exercise with a mean half-time of 4 min. The results demonstrate the utility of MR phase-encoded flow-velocity measurements for physiol ogical studies of peripheral vascular dynamics after exercise.