Handheld Microwave System for In Vivo Skin Cancer Detection: Development and Clinical Validation

A handheld microwave system for in vivo skin lesion detection and classification is presented. The system includes a microwave probe, which operates in contact with the skin, a compact inline one-port vector network analyzer, and a processing algorithm. To detect lesions originating at the dermal-epidermal junction, the system uses an open-ended coaxial probe with a sensing volume that ensures maximum response from the skin layer. The open-water-load calibration is used to convert the probe’s complex reflection coefficient to dielectric properties. The system operates within a safe specific absorption rate (SAR) (below 1.6 W/kg) across the band of interest with a total combined uncertainty of 1% and 1.9% for the dielectric constant and loss factor, respectively. To enable reliable measurements and eliminate data corruption that might be caused by the subject’s movement or air gaps at the probe-skin interface, the system includes a force sensor to ensure full probe-skin contact during in vivo measurements. The system was clinically tested on 19 suspected skin lesions in the arm region. The results indicate a clear separation in the dielectric properties between malignant and benign dermal lesions at frequencies between 1 and 14 GHz. Further analysis suggests that the contrast in the dielectric constant between malignant nonmelanoma lesions and their corresponding benign conditions is statistically significant at frequencies higher than 1 GHz. Additionally, the dielectric contrast between each tested lesion and its adjacent healthy skin results in a distinguishable grouping of nonmelanoma lesions, enabling their successful classification. Those results indicate the potential clinical use of the system.