Ultrasonographic evaluation of skin lesions refers to the use of ultrasound to provide information about the margins and depth of surface tumors or inflammatory skin conditions. Several ultrasound systems using transducers of at least 20 MHz have been approved by the Food and Drug Administration (FDA) for visualizing skin; lower frequency ultrasound transducers (12-15 MHz) have also been used.
High-frequency ultrasound transducers (20–100 MHz), which have limited penetration but high resolution, have been extensively used in ophthalmology and as a component of endoscopic ultrasound. These same parameters make high-frequency ultrasound suitable for evaluating skin lesions, where ultrasound can distinguish between the epidermis, dermis, and underlying connective tissue. Lower frequency ultrasound transducers (12-15 MHz) have also been used to evaluate skin layers. Although used extensively in Europe, ultrasonographic evaluation of skin lesions has not been widely used in the United States.
The following applications of ultrasonic evaluation of skin lesions have been proposed:
- To assess the margins and depth of melanoma and non-melanoma skin cancers to aid in surgical planning
- To assess actinic keratoses to determine if cryosurgery is an appropriate therapeutic option
- To follow the course of connective diseases of the skin, i.e., scleroderma, by evaluating the amount and location of collagen in the dermis
- To assess inflammatory skin diseases, such as allergic reactions or psoriasis
The FDA has cleared numerous ultrasound systems that include skin ultrasound as one of many indications. In addition, several ultrasonic systems that specialize in imaging skin have been cleared for marketing by the FDA though the 510(k) process. The Episcan® I-200, Ultrasound System (Longport, Inc., Glen Mills, PA), which uses either a 20-MHz or 30-MHz transducer, was cleared for marketing in November 2006. Its intended use is medical/surgical dermatology assessment and diagnosis (aesthetic and therapeutic), plastic/reconstructive surgical planning, wound assessment and management, skin assessment for pressure ulcer detection and prevention, and superficial musculoskeletal diagnosis. Another specialized system, the DermaScan™ C Ultrasonic System (Cortex Technology, Denmark) was cleared in 1999. This 20-MHz transducer is intended to be used to visualize the layers of the skin to make approximate measurement of dimensions of skin layers and blood vessels.