Vol.7 No.4 2015
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Research paper : International standardization of four dimensional radiotherapy system (Y. HIRATA et al.)−231−Synthesiology - English edition Vol.7 No.4 (2015) Although the 4DRT enables more effective therapy than the conventional radiotherapy, to perform the 4DRT safely, it is necessary to individually manage the parameters corresponding to tumor motions for each patient, since there is an increase in the number of parameters, including the timings of irradiation, the patterns of change in tumor position, the prediction model for predicting the change in tumor position, and others that are necessary to handle the degrees of freedom of tumor movement. In addition, the appropriate coordination of the X-IGRT equipment and external beam equipment that irradiates the tumor with x-rays, protons, or others is necessary to safely perform the radiation therapy.As explained above, new safety requirements that were not considered before are necessary to realize the 4DRT. In the R&D for 4DRT, the most important aspect is safety assurance, and the safety requirements for 4DRT must be internationally standardized as soon as possible, to enable safe performance of 4DRT widely around the world. In addition, it can be expected that trial-and-error to ensure safety during the R&D of 4DRT can be reduced through the international standardization of the safety requirements for 4DRT.Particularly, the arbitrary requirements that are internationally standardized by the International Electrotechnical Commission (IEC) are mandated and enforced, once they are quoted by the regulatory authority of a country. Therefore, the international standardization of the safety requirements of 4DRT system by the IEC is extremely effective to ensure solid safety assurance.1.3 Organizations involved in the international standardizationThere are three kinds of international standards: de jure standards that are developed by formal organizations; forum standards developed by private companies; and de facto standards that are developed through market competition (Intellectual Property Strategic Program 2011 of the Japanese government).Representative organizations that develop the de jure standards are International Organization for Standardization (ISO), International Electrotechnical Commission (IEC), and International Telecommunication Union (ITU). The radiotherapy equipment are handled in the electrotechnical field by the IEC, and the standardization of the X-IGRT equipment, an important component for realizing 4DRT, has recently progressed in the IEC.In the IEC, the Technical Committees (TC) are organized by categories, and the international standards pertaining to radiotherapy equipment are discussed in TC62 that handles the electrical equipment for medical practice. The TC62 has four Subcommittees (SC) as subsidiary organizations, including the following: SC62A (Common aspects of electrical equipment used in medical practice), SC62B (Diagnostic imaging equipment), SC62C (Equipment for radiotherapy, nuclear medicine, and radiation dosimetry), and SC62D (Electromedical equipment). The international standardization of 4DRT will be discussed in SC62C that handles the radiotherapy equipment.As shown in Fig. 4, the Japan Electronics and Information Technology Industries Association (JEITA) discusses the items related to TC62, SC62A, and SC62D of the IEC, as the Japanese national commission consigned by the IEC. Also, the Japan Medical Imaging and Radiological Systems Industries Association (JIRA)[10] discusses the items related to SC62B and SC62C of the IEC, as the Japanese national commission consigned by the IEC.2 Objective of this paperThe objective of this paper is to analyze our case of the international standardization of 4DRT in the IEC, and to present a direction of how to promote its international standardization for expanding the international use of 4DRT Fig. 3 Conceptual diagram of the tracking radiotherapy (left), and photograph of the tracking radiotherapy system using Vero4DRT of Mitsubishi Heavy Industries, Ltd. (right)Left photograph is cited from the website of Mitsubishi Heavy Industries. Movement due to respiration etc.Irradiation of therapeutic rayTumorTumor

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