Quantitative muscle ultrasound detects disease progression in Duchenne muscular dystrophy
In this 2‐year, nonblinded longitudinal study, we evaluated alterations in quantitative muscle ultrasound in boys with DMD and compared them to healthy controls, along with electrical impedance myography (EIM) measurements and functional assessments, as described in our companion article.11 Our goal was to determine whether quantitative muscle ultrasound, when performed by trained evaluators in a clinical trial setting, could provide effective biomarkers of disease progression in DMD. We measured muscle echo intensity in 2 ways. We utilized a direct analysis of the amplitudes of the reflected ultrasound echoes, measured in decibels, termed quantitative backscatter analysis (QBA), in addition to the more standard analysis of the gray scale pixel level (GSL) in a region of interest (ROI) within the fully processed image. The reason for evaluating QBA specifically is that the relatively large amounts of data contained in the raw backscattered energy may be lost or skewed when proprietary algorithms are used to compress the values into the 256 GSLs for image display. It is unknown whether QBA provides similar, better, or worse outcomes than using GSL for measuring disease progression in DMD.