Feasibility study of multi-purpose quality assurance phantom for pretreatment verification of volumetric modulated arc therapy

Background: the purpose of this study was to evaluate the feasibility of a multipurposequality assurance (qa) phantom for pretreatment verification ofvolumetric modulated arc therapy (vmat). materials and methods: the qaphantom was constructed with polymethyl methacrylate (pmma) to performrelative dosimetry using ebt3 film and mapcheck, as well as absolute dosimetryusing an ionization chamber. the qa phantom was constructed to perform relativedosimetry using ebt3 film and mapcheck, as well as the absolute dosimetry usingionization chamber. in order to verify the pretreatment plans, 25 patients treatedwith vmat were selected. the pretreatment plans were calculated in the eclipsetreatment planning system using the acuros xb dose calculation algorithm and ctimages for the qa phantom, with the same beam setup and monitor units (mus) asthose for patient treatment. all plans were delivered to the varian truebeamaccelerator equipped with a high-definition multi-leaf collimator. results: themulti-purpose qa phantom is developed for convenient vmat doseverification. by using the qa phantom, all 25 cases passed ±3% acceptabilitycriteria in absolute dosimetry with an ionization chamber for pretreatmentverification. the relative dosimetry using ebt3 film and mapcheck systemalso showed high agreement of more than 90% for 2%/2-mm and 3%/3-mmcriteria. conclusion: the results of this study demonstrated the good multipurposecapabilities of the phantom for the absolute and relative dosimetry.therefore, the developed multi-purpose qa phantom was applied in our institutionfor routine vmrt dose verification.