Physical factors influencing numerical echo-amplitude data extracted from B-scan ultrasound images

The replacement of analog-scan converters by digital-scan converters in commercially available B-scan ultrasound equipment provides easily available numerical echo-amplitude data from regions or organs of interest, once the image has been created. These values vary with, and are influenced by, a variety of physical variables, including transducer power output, time-gain compensation, signal threshold, preprocessing digital signal level assignment, frequency, and acoustic beam width. Unless vigorous efforts are made to standardize these variables, clinical reports using numerical analysis as disease descriptors should be viewed critically.