Skeletal muscle evaluation by MRI in a rabbit model of acute ischaemia.

OBJECTIVE: To assess rhabdomyolysis-associated skeletal muscle changes induced by complete ischaemia in rabbits using MRI.
METHODS: Acute ischaemia was induced in the right hind limb of 34 New Zealand white rabbits by arterial ligation. MRI of vastus lateralis was carried out pre-operatively and every hour post-operatively up to 7 h. T1 weighted images, T2 weighted images with fat suppression, T2 maps and diffusion tensor scans were obtained. The correlation of MRI findings with histopathological changes in biopsies of vastus lateralis was examined.
RESULTS: Histopathology demonstrated early cellular oedema 1 h post ischaemia and irreversible injuries by 7 h, including loss of striation and broken muscle fibres. T2 weighted images with fat suppression showed inhomogeneous high signal intensity of vastus lateralis, which progressively increased from 2 h following ischaemia. The T2 relaxation rate of ischaemic vastus lateralis was significantly greater than normal muscle (p<0.001) and demonstrated a linear increase with time following ischaemia. A similar linear increase was also found in the ischaemic vastus lateralis apparent diffusion coefficient (ADC) 1-5 h post ischaemia (p=0.006). Both the T2 ADC and fractional anisotropy (FA) were significantly higher on the ischaemic side 7 h post ischaemia (for T2, p=0.02; for ADC, p=0.004).
CONCLUSION: Muscle oedema is detectable on MR images and is reflected well by T2, ADC and FA values. MRI may have value in clinical evaluation of rhabdomyolysis. ADVANCES IN KNOWLEDGE: Ischaemic changes detected by MRI may have value in the diagnosis of rhabdomyolysis.