Antimyosin Scintigraphy Compared With Magnetic Resonance Imaging in Inflammatory Myopathies.

Objective: To compare indium In 111 altumomab pentetate–labeled antimyosin scintigraphy with magnetic resonance imaging (MRI) in the diagnosis and follow-up of patients with myositis. Design and Methods: Sixteen patients with polymyositis and 1 patient with dermatomyositis, all verified with biopsy samples, were examined during diagnostic evaluation with antimyosin antibody scintigraphy and low-field MRI of the thighs and calves using T[sub 1]- and T[sub 2]-weighted sequences. Both examinations were repeated 6 to 22 months after therapeutic intervention with anti-inflammatory drugs. The performance of the 2 methods for the assessment of the severity of muscle inflammation was evaluated using comparison with clinical examination and the serum creatine kinase level. Results: At diagnosis all patients had increased uptake of antimyosin antibody in the thighs and/or calves. In T[sub 2]-weighted MRI images, increased signal intensity changes reflecting intramuscular edema and inflammation were seen in all patients in at least 1 muscle group in the thighs or calves. After anti-inflammatory drug therapy, the mean uptake of antibody and the mean signal intensity changes in T[sub 2]-weighted MRI had decreased. However, in T[sub 1]-weighted MRI the signal intensity changes reflecting intramuscular fatty degeneration were more pronounced in the follow-up study. The level of serum creatine kinase had decreased markedly by the second examination except in 1 patient who also had more accumulation of antibody in the calves after than before treatment. The clinical condition improved in 8 patients and remained unchanged in 9 patients. Conclusions: Antimyosin scintigraphy and T[sub 2]-weighted MRI are feasible tools for the detection and follow-up of lesions in patients with myositis. Scintigraphy findings correlate with serum creatine kinase activity and seem to reflect disease activity better than T[sub 2]-weighted MRI changes, whereas secondary degenerative intra... [ABSTRACT FROM AUTHOR]