Muscle uptake of 99mtechnetium pyrophosphate in patients with neuromuscular disorder. A quantitative study

99mTechnetium pyrophosphate (99mTc PYP) muscular scanning was carried out in 28 patients affected by neuromuscular diseases. To express the muscle tracer retention quantitatively, the soft tissue to bone uptake ratio was calculated in the thigh and in the lower leg. Significantly increased ratio values were found in all the patients with polymyositis and in most patients with different types of muscular dystrophy, while high values were seen in a few subjects with myasthenia gravis and with neurogenic disorders. These findings are compared with those of previous studies, and the factors playing a role in determining some discrepant observations are discussed. The use of 99mTc muscular scanning in the investigation of patients with suspected inflammatory myopathy is suggested.