Miniature Antennas for Medical Microwave Radiometers

Mathematical simulation of three miniature antennas for medical microwave radiometry was held. The diameters of antennas were 8 mm, 15 mm, and 22 mm. Mathematical simulations were based on the numerical solution of 3D bioheat equation and Maxwell's equations for multilayer structure with a malignant tumor. The purpose of mathematical simulation was to assess the impact of the antennas size on the measured temperature. The bioheat equation was solved for the breast tissue with a malignant tumor. The model of the breast was consisted of several layers, glandular tissue, fat tissue, skin and malignant tumor. Each component of the model was characterized by its metabolic heat production, blood perfusion rate and thermal conductivity. The calculations were performed using COMSOL Multiphysics software.

Simple approximation function for temperature distribution in breast tissue with malignant tumor was derived. The resulting analytical temperature distribution was used for the calculation of self-radiation of human tissue. CST Microwave Studio was used to calculate the electromagnetic field in tumor and surrounding tissues of the breast. Calculations showed that the miniature antenna with 8 mm diameter had a significant advantage for identifying small malignant tumors located at a depth of less than 15 mm.

For the greater depth all the antennas showed approximately the same result for identifying tumor 10 mm. For 20 mm tumors standard antenna had a slight advantage for a depth of more than 15 mm compared to a miniature antenna. New miniature antennas presented in the article can be used for measuring the internal temperature of the various bodies where the use of larger antennas is unacceptable, for example, in dentistry, for measuring the temperature of the thyroid, joints, spine, etc.