Medical physics is an academic field that applies knowledge of science and engineering to medicine. Researchers with a variety of backgrounds, including physics, optics, and health sciences, are active here. The Koganezawa Laboratory is engaged in research into medical physics related to cancer radiation therapy, particularly in the development of technology related to radiation measurement. Research themes are diverse, including dose distribution evaluation methods, in vivo respiratory monitoring systems, and the development of optical CT, but graduation research includes themes that allow students to experience both hardware and software. We are also actively engaged in joint research with other universities and companies.

Development of gamma pass rate prediction and prediction accuracy evaluation method
In high-precision radiation therapy, a verification measurement is required in advance to ensure that the dose distribution created in the treatment plan (dose distribution simulation) can be irradiated exactly as planned, and a gamma analysis is performed to evaluate the degree of agreement between the treatment plan and the actual measurement on a scale of 100. In recent years, research and development has been conducted to predict the results of the verification measurement (gamma pass rate) using technologies such as AI in order to omit the measurement.
We have developed a method to predict gamma pass rates using dose uncertainty and deep learning. We are also developing a method to fairly evaluate the prediction model itself by utilizing the concept of event mixing, which has been used in particle and nuclear experiments.

Development of a breathing monitoring system for living organisms using a near-infrared camera
In radiation therapy for lung cancer and hepatocellular carcinoma, radiation beams synchronized with respiration must be aimed at tumors. We have been working on developing a system that tracks three-dimensional movements of the body surface using a near-infrared camera. Because radiation therapy devices irradiate tumors with beams from various directions, the optimal installation position and angle of the respiratory monitoring camera differs for each case. Therefore, we developed a system that automatically calibrates the position and angle of the camera, making it possible to install and remove the camera instantly. In addition, by using the respiratory data obtained by this system, we discovered for the first time that the body surface position (baseline) during expiration (when exhaling) at rest can also occur in the craniocaudal direction.

Development of in-air readout optical CT
Gel dosimeters have been attracting attention as detectors capable of measuring highly accurate three-dimensional dose distributions in verification measurements performed prior to high-precision radiation therapy. We are working on the development of an optical CT system to be used to read out dye gel dosimeters. Optical CT generally uses a water tank filled with a liquid with the same refractive index as the gel dosimeter, but we are working on developing a technology that does not use liquid, but instead corrects for the refraction of light to take tomographic images of dose distribution. This development will enable high-speed acquisition of dose distribution data with a lightweight device, and is expected to enable prior verification using gel dosimeters at speeds that have not been possible until now.