Spatial variation of acoustic parameters in human skin: an in vitro study between 22 and 45 MHz

Abstract

This study of spatial variance of acoustic parameters was performed on eight nonfrozen samples of female abdominal skin (women 46.5 ± 12.2 years old), obtained during plastic surgery. Intra- and interindividual variations are discussed on the basis of estimations of three acoustic parameters (slope of attenuation- β; integrated attenuation coefficient- IAC; integrated backscattering coefficient- IBC) and one texture parameter (based on two estimators of effective density of scatterers: α2 and α1/2) as a function of surface area and depth of acquisition in the frequency range 22 to 45 MHz. Values of intraindividual variations varied from 7.1% for IAC to 23.2% for IBC, and significantly decreased at a ratio between 1.2 to 2.3 when the acquisition surface area was increased from 4 mm2 to 1 cm2. Interindividual variations were higher than intraindividual variations, and varied from 14.2% for α1/2 to 51% for IBC. The mean values (± SD) for all specimens combined, estimated with a large number of independent radiofrequency (RF) lines (400) and for a surface area of exploration of 4 cm2, were 1.06 ± 0.17 dB cm−1 MHz−1 for β, 135 ± 37 dB cm−1 for IAC, (3.7 ± 1.9) × 10−2 cm−1 sr−1 for IBC, 1.40 ± 0.17 scatterers/resolution cell for α2 and 1.32 ± 0.27 scatterers/resolution cell for α1/2. Finally, attenuation μ(f) and backscattering coefficient σb(f) were compared to published results for the same parameters measured in human skin. (E-mail: lebert_m@med.univ-tours.fr)