Ultrasonic and viscoelastic properties of skin under transverse mechanical stress in vitro.

Ultrasound properties of rabbit and human skin tissues under transverse stress have been studied in vitro over the frequency range from 15 MHz to 40 MHz. B-scan images show significant increases in average dermal grey-scale levels for increasing strain. Quantitative measurements show that ultrasound attenuation coefficients decrease significantly with increasing strain. A linear decrease of 0.109 dB/mm/strain% in rabbit skin and 0.069 dB/mm/strain% in human breast reduction skin was observed at 30 MHz. Experimental results show that backscattering coefficients only exhibit minor variation with strain. The speed of sound in human skin appears to be age-dependent. The viscoelastic and mechanical properties of skin, including stress relaxation, creep and Young's modulus as a function of strain were also studied.