SU‐E‐T‐170: A Survey of Quality Assurance in Intensity‐Modulated Radiation Therapy in Japan

Abstract

Purpose: To investigate the status of the implementation of quality assurance (QA) for intensity‐modulated radiation therapy (IMRT) in Japan using a questionnaire survey. Methods: The questionnaire consisted of six sections: (1) clinical uses of IMRT; (2) IMRT‐related equipment; verification of the (3) absorbed dose; (4) dose distribution; and (5) fluence map; and (6) acceptance criteria for each verification. There were 55 questions in total. Results: The questionnaire was completed for 124 institutions. IMRT was performed for prostate cancer in 120 institutions (96.8%), followed by head and neck cancer in 81 (65.3%), and brain tumors in 67 (54.0%). Although at least four individuals were engaged in IMRT QA in 54.0% of the institutions, the number of full‐time persons involved in IMRT QA was two or less in 110 institutions (88.7%). This indicated that most institutions in Japan have a staff shortage. Dynamic IMRT was the most common beam delivery technique (52.5%) for prostate cancer, followed by segmental IMRT (25.0%) and volumetric modulated arc radiotherapy (15.0%). Similar tendencies were seen for head and neck cancer and brain tumors. More than 90% of the institutions verified both the absorbed dose and dose distribution. In more than 50% of the institutions, these were verified in each and every beam. The acceptance criterion for the absorbed dose verification was set to +/−3% in at least 80% of the institutions. Gafchromic film was used for the majority of dose distribution verification. The acceptance criteria for dose distribution verification mainly involved gamma analysis and a comparison of dose profiles; however, the judgment of acceptance did not depend on the results of the gamma analysis. Conclusion: This survey increases our understanding of how institutions currently perform IMRT QA analysis. This understanding will help to move institutions toward more standardization of IMRT QA in Japan. This research was funded by the Japan Society of Medical Physics.