Finger Models: Example of Complex Geometry in Investigations on Microwave Skin Cancer Diagnosis

Micro/mm-wave technology is a promising tool for the early diagnosis of skin cancers. It is important that the models, whether for numerical or experimental phantom investigations, be a good anatomical representation of the tissue distribution. Most models for skin cancer diagnoses consider layered media (skin, fat) with tumor inclusions. However, the human body has a number of extremities of a more complex geometry. To begin addressing this challenge, we have selected the human finger as an excellent model of complex tissue distribution, possibly all within the sensing depth of the probe placed on the skin surface. Four finger models, with progressive complexity of tissue layers, are simulated by following the anatomical finger structure. The models include a slim probe, applied to the healthy structure and its version with basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) at 20 GHz - 50 GHz. We then observe the S-parameters, showing that, for meaningful results, finger model should consist of at least three layers: skin, fat, and ligament in microwave probe sensing for BCC/SCC detection. These results suggests that, for body portions with complex tissue distribution close to the skin surface, all tissues must be included in the model in order to properly assess the feasibility of the microwave-based diagnostic devices.