The characteristics and clinical application of the ArcCHECK diode array for volumetric-modulated arc therapy verification / 中华放射肿瘤学杂志

ABSTRACT

Objective To evaluate the characteristics and clinical suitability of the ArcCHECK diode array for volumetric-modulated arc therapy (VMAT) verification.Methods The intrinsic sensitivity,short and long term reproducibility,dose and dose rate dependence,dose per pulsed dependence,field sizes dependence and directional response of the diodes were measured.The results of the diodes were compared with the measurement results of an ionization chamber and calculated results of treatment planning system.Gamma index was used to analyze the dose difference between the calculation and measurement for random selected 211 verified VMAT plans.Results The ArcCHECK performed well for all tests except directional dependence,which varies from a minimum of-3.9％ (seen only when the beam was incident on the diode at 180°) to a maximum of 7.7％ (approximately at 255°).Average gamma analysis passing rates with 3 mm/3％ for 113 nasopharyngeal cancer,48 cervical cancer and 50 rectal cancer patients VMAT plans were 93.5％,95.7％ and 97.5％,respectively,statistical significance has been found between either two of the groups (t=-12.69-4.88,all P＜ 0.01).Conclusions With proposed calibration method,the ArcCHECK diode array is very suitable for VMAT pretreatment verification,the complexity of VMAT plan is the main factor affecting the passing rate.