Calibrated Quantitative Ultrasound Imaging of Skeletal Muscle Using Backscatter Analysis

We evaluated the ability of an ultrasound method, which can characterize cardiac muscle pathology and has reliability across different imaging systems, to obtain calibrated quantitative estimates of backscatter of skeletal muscle. Our procedure utilized a tissue-mimicking phantom to establish a linear relationship between ultrasound grayscale and backscatter levels. We studied skeletal muscles of 82 adults: 45 controls and 37 patients with hereditary myopathies. We found that skeletal muscle ultrasound backscatter levels varied with probe orientation, age, and muscle contraction and pathology. Reliability was greater with the probe in longitudinal compared with transverse planes. Backscatter levels were higher in those >40 years of age, in muscle extension than flexion, and in myopathic patients than controls. Calibrated measurements of muscle backscatter have sensitivity and specificity in identifying and reliably measuring levels of skeletal muscle pathology.