title: [Quality assurance procedure for assessing mechanical accuracy of a radiation field center in stereotactic radiotherapy].
abstract: Stereotactic radiotherapy requires a quality assurance (QA) program that ensures the mechanical accuracy of a radiation field center. We have proposed a QA method for achieving the above requirement by conducting the Winston Lutz test using an electronic portal image device (EPID). An action limit was defined as three times the standard deviation. Then, the action limits for mean deviations of the radiation field center during collimator rotation, gantry rotation, and couch rotation in clockwise and counterclockwise resulted in 0.11 mm, 0.52 mm, 0.37 mm, and 0.41 mm respectively. Two years after the QA program was launched, the mean deviation of the radiation field center during gantry rotation exceeded the above action limit. Consequently, a mechanical adjustment for the gantry was performed, thereby restoring the accuracy of the radiation field center. A field center shift of 0.5 mm was also observed after a micro multi-leaf collimator was unmounted.
authors.affiliation: Department of Radiology, Osaka City University Hospital.
authors.forename: Daisaku
authors.initials: D
authors.lastname: Tatsumi
authors.forename: Akinori
authors.initials: A
authors.lastname: Ienaga
authors.forename: Ryosei
authors.initials: R
authors.lastname: Nakada
authors.forename: Akane
authors.initials: A
authors.lastname: Yomoda
authors.forename: Makoto
authors.initials: M
authors.lastname: Inoue
authors.forename: Takao
authors.initials: T
authors.lastname: Ichida
authors.forename: Masako
authors.initials: M
authors.lastname: Hosono
mesh_terms: D011785:Quality Assurance, Health Care / Q000379:methods*; D016634:Radiosurgery / Q000379:methods / Q000592:standards*