Purpose: To test the ability of different magnetic resonance imaging (MRI) modalities to discriminate the time course of damage and regeneration in a model of acute, toxin-induced muscle damage.
Materials and methods: We analyzed the time course of tissue and cellular changes in mouse lower limb musculature following localized injection of myotoxin by T2 , magnetization transfer (MT), and diffusion-weighted MRI. We also used T1 -weighted imaging to measure leg muscle volume. In addition, postmortem histological analysis of toxin-injected muscles was compared to uninjected controls.
Results: The damages detected by the MRI modalities are transient and recover within 3 weeks. Muscle water diffusivity and edema measured by leg volume increased within the first hours after injection of the toxin. The rate constant for volume increase was 0.65 ± 0.11 hr(-1) , larger than the increase in T2 (0.045 ± 0.013 hr(-1) ) and change in MT ratio (0.028 ± 0.021 hr(-1) ). During repair phase, the rate constants were much smaller: 0.022 ± 0.004 hr(-1) , 0.013 ± 0.0019 hr(-1) and 0.0042 ± 0.0016 hr(-1) for volume, T2 , and MT ratio, respectively. Histological analyses confirmed the underlying cellular changes that matched the progression of MR images.
Conclusion: The kinetics of change in the MRI measurements during the progression of damage and repair shows MRI modalities can be used to distinguish these processes.
Keywords: MRI; myotoxin; necrosis; regeneration; skeletal muscle.
© 2013 Wiley Periodicals, Inc.