Validation study of photon beam absorbed dose and two-dimensional dose distribution in intensity modulated radiotherapy in Henan province / 中华放射医学与防护杂志

ABSTRACT

Objective To validate the absorbed dose and two-dimensional dose distribution from photon beam by using Thermoluminescent dosimeter (TLD) and film for intensity modulated radiation therapy (IMRT).Methods A total of 8 medical accelerators were selected among 5 third-grade first-class hospitals using non-probabilistic sampling method in Henan province.TLDs were put into polytetrafluoroethylene solid phantom with size of 5 cm × 15 cm × 15 cm provided by IAEA.After CT scanning,the radiotherapeutic plans were formulated through image transmission to the treatment planning system (TPS).The IMRT plan was implemented for measurement of TLD-absorbed doses under the conditions of 5 cm × 5 cm field,90 cm SSD,10 cm depth,6 MV photon beam and 6 Gy absorbed dose and corresponding measurement unit (MU).The 25 cm × 25 cm film-absorbed dose measurement was made in the same manner as TLD under the conditions of 30 cm × 30 cm size,20 cm thickness,95 cm SSD and 5 cm depth.Results Of eight accelerators,the requirements can be met for 7 accelerators with respect to the relative deviation of TLD absorbed dose except 1.For film,relative deviations were all consistent with the requirements.The passing rate of two-dimensional dose distribution was in line with the requirements for 7 accelerators except 1.Conclusions TLD and film can be used to check the MLC field absorbed dose and two-dimensional dose distribution.This methodis simple,easy to operate and suitable for the implementation of IMRT quality control in hospitals in Henan province.