Propagation of ultrasound in skin

The scanning laser acoustic microscope (SLAM) at 100 MHz and backscattering acoustic technique (BAT) at 10–40 MHz were used to examine canine skin. Specimens from four animals and from four locations on the animal were analyzed biochemically and morphologically as well as acoustically. The mean collagen and water concentrations were 20% ± 2% and 60% ± 3%, respectively. An analysis of variance of the SLAM data and the biochemical data showed significant animal to animal differences and some differences due to location on the animal. At 100 MHz the mean ultrasonic speed obtained with the SLAM was 1632 ± 34 m/s and the mean attenuation coefficient was 57 ± 10 dB/mm. Using BAT the mean integrated attenuation coefficient was 11 ± 3 dB/mm at 25 MHz (midfrequency range). While the speed values fall within the range of values previously reported for skin, the values for the attenuation coefficient using either SLAM or BAT are considerably higher than would be predicted from literature values at 1–10 MHz. Thus the attenuation coefficient is a stronger function of frequency that the data at lower frequencies would suggest. [Work supported by NIH and RR&D of the Veterans Administration.]