Research of a microwave radiometer for monitoring of internal temperature of biological tissues

Currently, there is growing interest among specialists in the use of non-invasive dose-free technologies for diagnosis and monitoring treatment of various diseases. Microwave radiometry enables non-invasive detection of thermal abnormalities in internal tissues of the human body. The current level of development of the method of microwave radiometry makes it possible to non-invasively detect malignant neoplasms at early stages according to characteristics of the person's own radiothermal fields. For a wider implementation of the method, it is necessary to overcome a series of scientific and technical barriers that impede its development. First of all, it is necessary to ensure miniaturization of the equipment used.An analytical review of the current state of development in the field of medical radiometers has been performed. Miniaturization of equipment is an important area for studies. It was shown that application of the proposed scheme for designing a null balance radiometer with a sliding scheme of reflection compensation with two matched RF loads will enable creation of a miniature highly stable radiometer. The measurement error of this device does not depend on the ambient temperature, intrinsic temperature of the device and impedance of the studied area of the body. The device calibration procedure was considered and noise signal calculations were performed. Results of experimental verification of correctness of choice of the way of designing the miniature radiometer circuit were presented. Introduction of thermal compensation has made it possible to reduce measurement error associated with the device heating to 0.2 °C when intrinsic temperature of the radiometer changed by 20 °C. It was shown that a radiometer operating in the frequency band 3.4–4.2 GHz can be used to detect various diseases and monitor internal temperature of tissues during treatment. With introduction of autonomous power supply and wireless communication with a smartphone, the miniature radiometer can be used as a wearable device to monitor temperature of internal tissues in everyday human life.