ANTIMYOSIN SCINTIGRAPHY COMPARED WITH MAGNETIC-RESONANCE-IMAGING IN INFLAMMATORY MYOPATHIES

Objective To compare indium In 111 altumomab pentetate-labeled antimyo sin scintigraphy with magnetic resonance imaging (MRI) in the diagnosi s and follow-up of patients with myositis. Design and Methods: Sixteen patients with polymyositis and 1 patient with dermatomyositis, all ve rified with biopsy samples, were examined during diagnostic evaluation with antimyosin antibody scintigraphy and low-field MRI of the thighs and calves using T-1- and T-2-weighted sequences. Both examinations w ere repeated 6 to 22 months after therapeutic intervention with antiin flammatory 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 antibod y in the thighs and/or calves. In T-2-weighted MRI images, increased s ignal intensity changes reflecting intramuscular edema and inflammatio n were seen in all patients in at least 1 muscle group in the thighs o r calves. After anti-inflammatory drug therapy, the mean uptake of ant ibody and the mean signal intensity changes in T-2-weighted MRI had de creased. However, in T-1-weighted MRI the signal intensity changes ref lecting intramuscular fatty degeneration were more pronounced in the f ollow-up study. The level of serum creatine kinase had decreased marke dly by the second examination except in 1 patient who also had more ac cumulation 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-2-weighted MRI ar e feasible tools for the detection and follow-up of lesions in patient s with myositis. Scintigraphy findings correlate with serum creatine k inase activity and seem to reflect disease activity better than T-2-we ighted MRI changes, whereas secondary degenerative intramuscular lesio ns are only detectable using T-1-weighted MRI.