High-frequency ultrasound in the evaluation of pharmacological effects on the skin.

In 1987, the introduction of two 20-MHz B- (brightness-) scan ultrasound systems with axial and lateral resolution of 200 microm and 75-80 microm, respectively, rendered two-dimensional sonographic imaging in dermatology possible. Since then cutaneous sonography has increasingly been used to investigate drug effects on human skin. Both unwanted and wanted effects have been studied, including skin thinning due to repeated glucocorticoid application and reduction of skin thickening in hyperplastic disorders such as psoriasis vulgaris due to various treatment approaches. The resolution of 20-MHz ultrasound is sufficient for studying pathological changes and pharmacological effects in the dermis and the subcutaneous fat; for assessing the epidermis, frequencies between 50 and 100 MHz may prove to be more effective.