MAGNETIC-RESONANCE-IMAGING AND MAGNETIZATION-TRANSFER IN EXPERIMENTALMYONECROSIS IN THE RAT

Experimental myonecrosis-induced by injection of notexin into rat tibi alis anterior muscle-and subsequent regeneration were studied from 1 h to 20 days postinjury with magnetic resonance imaging using conventio nal and magnetization transfer sequences, and these findings were corr elated with histopathology. MR images revealed necrosis within 1 h pos tinjection. Histopathologically, necrotized fibers enlarged and interc ellular spaces widened, indicating intracellular and extracellular ede ma, which began to decrease after 48 h, whereafter the formation of ne w myofibers predominated. T-2 increased progressively until 7.5 h, whi le T-1 increased until 24 h. Magnetization transfer contrast (MTC) and magnetization transfer rate (R(wm)) decreased rapidly postinjection; the decrease in R(wm) lasted longer than in MTC (96 h versus 48 h, res pectively). Spin echo, inversion recovery and magnetization transfer s equences revealed the lesions equally effectively. MR images and relax ation parameters reflect well the extent of histopathological injury a nd edema in the acute phase, whereas specific tissue changes in the re generative phase were not detectable by MRI. MT imaging and especially magnetization transfer rate are as sensitive as conventional T-2 cont rast to alterations in water imbalance.