Purpose: To quantify the differences between normal and corticosteroid-treated Duchenne muscular dystrophy (DMD) lower limb muscle using signal intensity measurements on T(1)-weighted and gadolinium contrast-enhanced images and by measurement of muscle T(2) values, and to investigate the effect of exercise.
Materials and methods: Eleven ambulant boys with DMD were imaged at 3 Tesla (T(1)-weighted, gadolinium enhancement and T(2) measurement) before stepping exercise and again (gadolinium, T(2) measurement) 4 days later and were compared with five healthy controls imaged 4 days before and after stepping exercise. Muscle region-of-interest signal intensities were referenced to external oil and gadolinium phantoms.
Results: DMD thigh muscle T(2) values were significantly higher than normal values with the exception of the gracilis muscle. Eight of nine muscles studied showed a significant increase in T(1)-w signal intensity in DMD as compared to normal muscle, suggestive of increased fat infiltration in DMD muscle. In the DMD boys, an exercise effect (increased contrast enhancement) was only seen for the tibialis anterior muscle.
Conclusion: Referenced signal intensity measurements may be used to quantify differences between dystrophic and normal muscle without T(1) mapping. Stepping exercise does not have a large impact on subsequent MR imaging of dystrophic muscle.