Reproducibility of skin characterization with backscattered spectra (12--25 MHz) in healthy subjects

Ultrasonic techniques were developed for quantitative in vivo analysis of skin composition based on measurements of apparent integrated backscatter (IBS) and its frequency dependence (n) between 12.5 and 25 MHz. Parameters were measured at five depths in healthy dermis of the midforearm of 29 volunteers (13 women, 16 men, 20 to 76 years old) on three different days. Reproducibility of measurements was evaluated (standardized coefficients of variation: 7% to 11% for IBS and 9% to 20% for n). Parameter values were significantly influenced by pressure of the ultrasonic probe on the skin, and both room and skin-surface temperatures were correlated to IBS measured in a single subject on 28 days. More precise control of these factors could further improve measurement reproducibility and sensitivity to skin composition. Significant (p < 0.05) differences of parameter values with respect to region of interest depth, age and gender of subjects were discussed in comparison with dermal composition and offer promise that these parameters could be used to characterize skin modifications.