Developing a measuring device which may become a gold standard for in vivo dosimetry
Evaluating the accuracy of radiotherapy
In recent years, radiotherapy has become utilizable as a therapy for cancerous tissues with a high accuracy on the order of 1mm. Implementing radiotherapy at this high level of accuracy requires quality assurance (QA) and quality control (QC) in order to maintain a high level of exposure precision. By applying proper QA/QC, we can accurately expose cancer tissues to a determined radiation dose while avoiding any unnecessary exposure of the surrounding healthy tissue.
At present, management of the radiation dose applied to a patient is primarily done through prediction based on QA/QC results, but with this method, the actual dose applied to a patient is not clear. Therefore, our research team is moving forward with the development of a method of in vivo dosimetry and a dedicated radiation dosimeter in order to directly confirm whether the applied radiation dose is correct during radiotherapy. This method directly measures the radiation dose during therapy through the use of a radiation meter inserted into the patient’s body, and is the only means of directly measuring the dose actually applied to the patient.
Compared to conventional X-ray therapy, heavy ion radiotherapy enables higher dose concentration on the cancerous tissue, and thus requires higher radiation accuracy, so we think it would work well with in vivo radiation measurement. Our research team succeeded in detecting the same value of radiation dose as the planned value by in vivo dose measurement in patients undergoing heavy ion radiation, thereby achieving the world’s first internal dose measurement during carbon ion radiotherapy.
Towards standardization of measuring devices
Radiotherapy techniques are becoming increasingly diverse. Even just classifying according to radiation type, there are X-rays, proton beams, heavy ion beams, and others. Additionally, irradiation technology has consistently improved, and technologies like irradiating from multiple angles and ultra high-dose irradiation can also be used when necessary.
There has not been an in vivo dosimeter capable of handling all of these diverse radiotherapies, so development has been an urgent need. Regarding this task, our research team has advanced research into using a radiation dosimeter we developed to realize in vivo measurement that is capable of handling this diversity of radiotherapies.
In order to deal with X-ray and proton beam therapy, we performed experiments specifically aimed at acquiring radiation dosimeter response characteristics for each radiation type, and have obtained good results.
As seen above, the radiation dosimeter we are developing is likely to create a gold standard for in vivo dosimetry, which currently does not have a standardized measurement method. We believe that continuous research and development of the meter will help promote more precise radiotherapy.
Department of Radiological Sciences