On-site audits to investigate the quality of radiation physics of radiation therapy institutions in the Republic of Korea.

PURPOSE: To investigate and improve the domestic standard of radiation therapy in the Republic of Korea.

METHODS: On-site audits were performed for 13 institutions in the Republic of Korea. Six items were investigated by on-site visits of each radiation therapy institution, including collimator, gantry, and couch rotation isocenter check; coincidence between light and radiation fields; photon beam flatness and symmetry; electron beam flatness and symmetry; physical wedge transmission factors; and photon beam and electron beam outputs.

RESULTS: The average deviations of mechanical collimator, gantry, and couch rotation isocenter were less than 1mm. Those of radiation isocenter were also less than 1mm. The average difference between light and radiation fields was 0.9±0.6mm for the field size of 20cm×20cm. The average values of flatness and symmetry of the photon beams were 2.9%±0.6% and 1.1%±0.7%, respectively. Those of electron beams were 2.5%±0.7% and 0.6%±1.0%, respectively. Every institutions showed wedge transmission factor deviations less than 2% except one institution. The output deviations of both photon and electron beams were less than ±3% for every institution.

CONCLUSIONS: Through the on-site audit program, we could effectively detect an inappropriately operating linacs and provide some recommendations. The standard of radiation therapy in Korea is expected to improve through such on-site audits.