MR imaging of intramuscular hemorrhage.

This retrospective study was performed to (a) analyze the appearance of normal striated muscle using the spin echo (SE) technique and (b) evaluate the potential of magnetic resonance (MR) imaging for demonstrating intramuscular bleeding. Magnetic resonance examinations of 30 patients imaged for reasons other than muscular disorders were reviewed. Normal striated muscle was always imaged with a lower intensity than fat because muscle had a longer T1 and a shorter T2 than fat. Furthermore, the spin density of muscle was less than that of fat. The best contrast between the two tissues was obtained with a short repetition time (TR) of 0.5 s and a long echo time (TE) of 56 ms. In addition, five MR examinations from three patients with intramuscular bleeding were assessed. In one case the CT examination was also available for comparison. In every case MR permitted the diagnosis and demonstrated the precise extent of intramuscular bleeding and its regression after therapy. The MR diagnosis of intramuscular bleeding was readily performed because of the excellent contrast resolution of the technique. These lesions were always brighter than the surrounding normal muscle. The optimum SE technique, which enhanced contrast between the muscle and the site of bleeding, was a long TR of 2.0 s and a long TE of 56 ms. The T1 and T2 relaxation times of intramuscular bleeding were always longer than those of normal striated muscle. Preliminary results indicate that MR is very sensitive for the demonstration of intramuscular bleeding.