In vivo normal human dermis characterization by 20-MHz ultrasound backscatter

Backscattered 20-MHz radio frequency (RF) signals were acquired from 10 sites of normal anterior mid-forearm of 29 subjects on three days and from one subject on 28 days. Using spectral analysis (12-25 MHz), apparent integrated backscatter (IBS) and frequency dependence of backscatter (n) were estimated at 5 successive dermal depths. Values of both parameters increased when greater pressure was placed on the skin during acquisition. IBS increased with depth while n decreased. In the most superficial depth studied, IBS was significantly correlated with age and was significantly higher in men. Parameter variations are discussed in terms of skin composition. Standardized coefficient of variation ranged from 7.7 to 10.3% for IBS and from 9 to 20% for n. Precise control of factors such as contact pressure and temperature could further improve reproducibility thus optimizing the technique for detection of pathologies or changes due to cosmetic or medical therapy.