Skeletal muscle perfusion during exercise using Gd-DTPA bolus detection.

The study was performed to evaluate if skeletal muscle perfusion can be determined during exercise using an IV bolus injection of Gd-DTPA. A fast spoiled gradient echo sequence (T1 weighted) was used with intermittent imaging during one-legged plantar flexion at different workloads. Between repetitive flexions, a 2-sec rest allowed magnetic resonance imaging (MRI) of the lower legs and measurements of the blood flow in the popliteal artery by ultrasonography for subsequent calculation of muscle perfusion. Maximal signal intensity, upslope and downslope of the bolus, mean transit time, and integrated curve area were measured within regions of interest bilaterally. The skeletal muscle perfusion estimated by ultrasonography increased in the exercising leg from 4 ml x 100 g(-1) x min(-1) at rest to 38 ml at low, 86 ml at medium, and 110 ml x 100 g(-1) x min(-1) at high workload. The SImax increased from 1.38 +/- 0.12 to 1.58 +/- 0.15 and the negative slope of the peak nonsignificantly from - 2.38 +/- 1.75 to - 12.05 +/- 9. 71. All obtained MRI parameters could visually separate the muscles into exercising, nonexercising, and presumably low active muscles. It is concluded that the signal intensity curve using a fast spoiled gradient echo sequence did not overall quantitatively mirror the perfusion, evaluated as the blood flow measured by ultrasonography. However, the signal intensity seemed to follow the blood flow velocity within a limited range of 15-60 cm x sec(-1), corresponding to 35-90 ml x 100 g(-1) x min(-1). Nonetheless, it might be useful when studying ischemia or endothelial dysfunction in skeletal muscles during exercise.