Skeletal muscle perfusion during exercise using Gd-DTPA bolus detection

The study was performed to evaluate if skeletal muscle perfusion can be det ermined exercise using an IV bolus injection of Gd-DTPA. A fast spoiled gra dient echo sequence (T1 weighted) was used with intermittent imaging during one-legged plantar flexion at different workloads. Between repetitive flex ions, a 2-sec rest allowed magnetic resonance imaging (MRI) of the lower le gs and measurements of the blood flow in the popliteal artery by ultrasonog raphy for subsequent calculation of muscle perfusion. Maximal signal intens ity, upslope and downslope of the bolus, mean transit time, and integrated curve area were measured within regions of interest bilaterally. The skelet al muscle perfusion estimated by ultrasonography increased in the exercisin g leg from 4 ml (.) 100 g(-1) (.) min(-1) at rest to 38 ml at low, 86 ml at medium, and 110 ml (.) 100 g(-1) (.) min(-1) at high workload. The SImax i ncreased 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 obtaine d MRI parameters could visually separate the muscles into exercising, nonex ercising, and presumably low active muscles. It is concluded that the signa l intensity curve using a fast spoiled gradient echo sequence did not overa ll quantitatively mirror the perfusion, evaluated as the blood flow measure d by ultrasonography. However, the signal intensity seemed to follow the bl ood flow velocity with a limited range of 15-60 cm (.) sec(-1), correspondi ng to 35-90 ml (.) 100 g(-1) (.) min(-1). Nonetheless, it might be useful w hen studying ischemia or endothelial dysfunction in skeletal muscles during exercise.