Comparison of level-I, -II and -III dosimetry quality audits for MV-photon beams emitted from medicallinear accelerators

Background: dosimetry audits have an important role to safely deliver theprescribed radiation dose to the cancerous area. it not only maintains andimprove the treatment standards but also identify issues that are potentiallyharmful to the patients. this article presents the results of a comparativestudy of beam output measurements of a high-energy photon beam emittedfrom a medical linear accelerator. materials and methods: the measurementswere performed by an international atomic energy commission (iaea)quality assurance/quality control survey mission (level-i dosimetry), anational secondary standard dosimetry laboratory (ssdl) experts (level-iidosimetry) and hospital physicists (level-iii dosimetry). glass dosimeters andcylindrical ionization chambers for level i and cylindrical ionization chambersfor level-ii and -iii dosimetry were used in water by following iaea trs-398protocol. results: the level-i dosimetry results of glass dosimeters andionization chambers were compared and percent deviations of -0.4 % and 0.3% were found for 6 and 15 mv-photon beams, respectively. similarly, level-iiand -iii dosimetry results with respect to level-i are in good agreement andwithin the optimum uncertainty level of ±5%. the annual level-ii dosimetryquality audits (i.e., from 2010 to 2015) showed that only one dosimetry auditis out of the optimum level set for this study. however, it is within thetolerance level set for level-ii quality audit programs (i.e., < ±5%). conclusion:in conclusion, this article has demonstrated consistent radiotherapy radiationdosimetry results for mv-photons beams. it also showed quantitativeinformation in-line with the currently achieved accuracy and precision ofexternal megavoltage photon beam dosimetry. furthermore, this study alsoestablished a baseline for current routine audits of radiotherapy dosimetry.studies of this type are essential to appropriately follow therecommendations and procedures of the pertinent dosimetry protocols