Quantitative muscle ultrasound in Duchenne muscular dystrophy: A comparison of techniques

Introduction: Muscle pathology in Duchenne muscular dystrophy (DMD) can be quantified using ultrasound by measuring either the amplitudes of sound-waves scattered back from the tissue [quantitative backscatter analysis (QBA)] or by measuring these backscattered amplitudes after compression into grayscale levels (GSL) obtained from the images. Methods: We measured and compared QBA and GSL from 6 muscles of 25 boys with DMD and 25 healthy subjects, aged 2-14 years, with age and, in DMD, with function (North Star Ambulatory Assessment). Results: Both QBA and GSL were measured reliably (intraclass correlation≥0.87) and were higher in DMD than controls (P<0.0001). In DMD, average QBA and GSL measured from superficial regions of muscle increased (rho≥0.47, P<0.05) with both higher age and worse function; in contrast, GSL measured from whole regions of muscle did not. Conclusions: QBA and GSL measured from superficial regions of muscle can similarly quantify muscle pathology in DMD.