A high-frequency ultrasound method for testing skin cancer margins ex vivo

Mohs surgery is the standard surgical treatment for basal cell carcinoma and several melanomas. It involves resecting successive layers of the skin cancer and surrounding tissue (margins), analyzing the tissue in a pathology laboratory, and using the results to determine whether all of the cancer has been removed or whether another layer needs to be resected. Although resection of each layer only takes 5-10 minutes, procedure times for Mohs surgery are approximately 4 hours since the pathology analysis is very time consuming. A rapid specimen assessment technique for detecting skin cancer in surgical margins would therefore be of significant benefit to dermatology surgeons and their patients. A high-frequency ultrasound method has been developed to test Mohs surgical specimens without the need for direct immersion or transducer contact on the specimens. The ultrasound system uses a 50-MHz, narrow-beam (1.5 mm) pachymeter probe; a 50-MHz, broad-beam (6.25 mm) transducer; a high-frequency pulser-receiver; a 1-GHz digital oscilloscope; and an aluminum test stage to hold and scan the specimen. Pitch-catch and pulse-echo measurements are collected from each test position on the specimen to determine the position’s thickness and ultrasonic wave speed. Other parameters calculated from the data include attenuation and spectral peak density.