100 MHz sonography for visualisation of the palmar stratum corneum after application of different creams and ointments.

To visualise the effects of different topically applied substances on the s tratum corneum in vivo by means of sonography, it is necessary to have an u ltrasound unit with a much higher resolution than provided for by the 20 MH z scanners currently used in dermatology. We developed a workstation with a highly focussed transducer with a large bandwidth, providing a resolution of 9 mu m axially and 27 mu m laterally. Using this ultrasound unit, we inv estigated the effects of different creams and ointments in 10 persons on th e palmar side of the distal finger segments (vaseline, a water-in-oil-emuls ion, an oil-in-water-emulsion, 10% urea in an oil-in-water-emulsion and wat er). Sonograms were taken after an occlusion period of 0, 30, 60, 120, 180 and 240 min. In 100 MHz sonograms of palmar skin, the stratum corneum is re presented as an echo-poor band below the echo-rich entry echo - the correla te of the interface between the coupling water and the horny layer. The ech o-poor band is traversed by echo-rich coils, representing eccrine sweat gla nd ducts. It is separated by an echo-rich line from the viable epidermis, w hich is echo-poor as well. The topically applied substances differ in the t ime course of the swelling of the stratum corneum. After longer application all externals cause a significant thickening of the stratum corneum (p < 0 .005) and a reduction of the echogenicity of the skin entry echo due to alt ered impedance. 100 MHz sonography is well suited to visualise and quantify the effects of externals on the stratum corneum in vivo.