Evaluation of PTW Seven29 combining Octavius phantom for tomotherapy patient-specific quality assurance

Abstract

Objective To investigate the feasibility of dose verification of helical tomotherapy (HT) using the PTW Seven29 2D-ARRAY with Octavius phantom.Methods The 12 patients HT plan were verified with the PTW Seven29 2D-ARRAY combining Octavius phantom.The detector array was guided and registered by MVCT imaging,and measured dose distributions on the corresponding planes were compared with those calculated by the treatment planning system (TPS).Based on several different Gamma criteria,the Gamma analysis method was utilized to evaluate the dose verification.Results According to the different acceptance criteria combination of dose difference/distance to agreement at different threshold level including 3％/2 mm,3％/3 mm,3％/4 mm,3％/5 mm at TH5,TH10,TH20,TH30,the mean passing rates with γparameter ≤ 1 were all above 91.7％ and 93.9％ when PTW Seven29 2D-ARRAY was horizontal and vertical.The dose distribution measured by the 2D-ARRAY combining Octavius phantom was well consistent with that calculated by the TPS.Conclusions 2D-ARRAY with Octavius phantom can get satisfying results when used in HT plan dose verification and is a viable tool to replace traditional film dosimetry system in clinical quality assurance work. Key words: Tomotherapy; PTW Seven29 detector array; Dose verification; Quality assurance