Ischemia-Reperfusion Injury in Rat Skeletal Muscle Assessed with T2-Weighted and Dynamic Contrast-Enhanced MRI

Pressure ulcers are localized areas of soft tissue breakdown due to mechanical loading. Susceptible individuals are subjected to pressure relief strategies to prevent long loading periods. Therefore, ischemia-reperfusion injury may play an important role in the etiology of pressure ulcers. To investigate the inter-relation between postischemic perfusion and changes in skeletal muscle integrity, the hindlimbs of Brown Norway rats were subjected to 4-h ischemia followed by 2-h reperfusion. Dynamic contrast-enhanced MRI was used to examine perfusion, and changes in skeletal muscle integrity were monitored with T-2-weighted MRI. The dynamic contrast-enhanced MRI data showed a heterogeneous postischemic profile in the hindlimb, consisting of areas with increased contrast enhancement (14-76% of the hindlimb) and regions with no-reflow (5-77%). For T-2, a gradual increase in the complete leg was observed during the 4-h ischemic period (from 34 to 41 msec). During the reperfusion phase, a heterogeneous distribution of T-2 was observed. Areas with increased contrast enhancement were associated with a decrease in T-2 (to 38 msec) toward preischemic levels, whereas no-reflow areas exhibited a further increase in T-2 (to 42 msec). These results show that reperlusion after prolonged ischemia may not be complete, thereby continuing the ischemic condition and aggravating tissue damage. Magn Reson Med 66:528-537, 2011. (C) 2011 Wiley-Liss, Inc.