Ultrasound in dermatology--basic principles and applications.

Ultrasound is widely used in general clinical medicine for non-invasive internal imaging. Over the last twenty years, technological advances have enabled the application of high-resolution ultrasonic imaging to the skin. Equipment and hardware is now available to produce cross-section images and three-dimensional reconstructions of selected skin segments. Resolution in vivo is not comparable to light microscopy but continues to improve with superior transducer designs. Skin ultrasonography has been reliably employed as an imaging modality in experimental designs, its quantifiable parameters being a distinct advantage. In particular, increased water content of the upper dermis, as occurs in inflammatory conditions or as a result of photodamage, can be demonstrated clearly as an echo-poor zone. Thus, the future of high-resolution ultrasound (HRU) may reside in its experimental role in monitoring inflammatory or photodamage processes in response to novel treatments. With regard to skin tumours, HRU reliably measures tumour thickness and also holds promise as a differentiator between seborrhoeic keratoses vs. melanoma and benign naevi vs. melanoma. While largely an experimental tool, the potential as an accurate, quantitative and reliable diagnostic and monitoring aid, merits further attention with an emphasis on clinical outcome measures.