Radiofrequency Skin Cancer Screening: Development of Tissue-Mimicking Phantoms for System Validation

In recent years, developments have shown that microwave imaging offers a cost-effective and promising alternative in cancer screening [1][2][3].Currently, skin cancer screening is carried out by visual assessment through a healthcare professional, with detection accuracy depending on the experience and expertise of individual care providers [4].The reported inherent dielectric contrast of healthy, benign and malignant tissues supports the exploration of microwave-based measurements for early-stage cancer detection [5,6].Microwave technologies rely on accurate measurement techniques for dielectric properties and development of preclinical lab models (phantoms) to validate novel skin cancer probes in a controlled environment.This research presents a novel phantom to validate a skin cancer probe in a controlled environment, based on melanoma dielectric measurements from 2 -18 GHz.The melanoma-mimicking phantom presented in this work is based on the recipe reported in [3] for basal cell and squamous cell carcinoma, with added natrium chloride (NaCl) and varying concentrations of TX-151.The main components of the phantom include Bloom 200 gelatin (14.8 g), deionized water (100 g) and safflower oil (15 g), while varying amounts of TX-151 (1 g and 2.5 g) were added to improve the stability of the dielectric properties over the lifespan of the phantom, and NaCl (1.6 g) to increase relative permittivity and conductivity to match melanoma dielectric properties.The phantoms were cured in silicone molds over 24 hours at 20 C.The complex dielectric properties were then measured using a Keysight slim form probe and Fieldfox vector network analyzer (VNA) [7,8].The dielectric properties of the phantoms were measured at four lateral locations across a flat surface, with five repeated measurements at each location.The average dielectric measurement of each phantom was compared to reported melanoma dielectric properties [5,6].While both TX-151 concentrations display good agreement with the reported melanoma dielectric properties, the 1g TX-151 phantom showed superior agreement across the entire frequency range and the results were fitted to a single-pole Cole-Cole model [9].In conclusion, a validation phantom has been developed for microwave skin cancer probe testing, based on simple ingredients and with representative dielectric properties to mimic melanoma over a wide frequency range from 2 -18 GHz.