Magnetic resonance of diseased skeletal muscle: combined T1 measurement and chemical shift imaging.

Magnetic resonance examinations of skeletal muscle with differential T1 relaxation time measurements were performed in 19 patients with muscular dystrophies and congenital myopathies, and in eight control subjects. A field echo chemical shift imaging technique was used. T1 values of muscular tissue were measured from the primary composite images, and differential T1 values were calculated separately from water and fat images. Longitudinal relaxation times of skeletal muscle were significantly increased in both dystrophies and myopathies. The results of differential relaxation time measurements suggest that intramuscular fat reduces the abnormal increase in T1 of diseased muscle tissue. When characterizing diseases of skeletal muscle by T1 relaxation time measurements, the contribution of secondary fatty infiltration must be considered.