Megavoltage cone-heron CT in the use of head and neck dose calculation / 中华放射肿瘤学杂志

ABSTRACT

Objective To evaluate the feasibility and accuracy of performing dose calculation on megavoltage cone-beam CT(MVCBCT) in the head and neck. Methods MiniCTQC phantom was imaged using MVCBCT scanner, and the MVCBCT value density calibration curve was established. Conventional CT and MVCBCT image of phantom and nasopharyngeal carcinoma(NPC) patient were acquired respectively. Two kinds of single field plan were designed for conventional CT image of phantom,and IMRT plan was used for conventional CT image of a NPC patient. The conventional CT plans were copied to MVCBCT image. The dose distribution was calculated for targets and normal tissues using the MVCBCT value density calibration curve,and compared with that of conventional CT. Results For all the cases,the differences between the calculated dose distributions using MVCBCT and CT were less than 3% and 3 mm in single field plan. In IMRT plan, DVHs of conventional CT and MVCBCT were in excellent agreement. The biggest difference between conventional CT and MVCBCT was 95 cGy with the error of 1.4%. On the isocenter plane,the passing rate was 95.5% ,99.4% ,93.8% ,98.7%, 100% ,94.5% ,97.3% ,95.6% ,99.3% and 99.4% for the beam angle of 0°,45°,90°,120°,160°,200°,240°,280° and 320°. Conclusions Performing dose calculation using MVCBCT in head-and-neck region was feasible, and the dose distributions on the conventional CT and MVCBCT were in excellent agreement.