利用ArcCHECK在实际机架角与零机架角的IMRT剂量验证结果比较

目的 研究鼻咽癌和宫颈癌在实际机架角和零机架角两种方式做IMRT剂量验证时γ通过率的差异。方法 从87例鼻咽癌计划和54例宫颈癌计划中采用单纯随机抽样方法选取鼻咽癌与宫颈癌各30例。以3 mm/3%标准,用ArcCHECK分别测量其在实际机架角和零机架角时的γ通过率,并对其结果进行配对t检验。结果 30例鼻咽癌实际机架角、零机架角的γ通过率分别为(93.8±3.6)%、(97.8±1.1)%(P=0.00);30例宫颈癌的分别为(96.3±2.1)%、(98.2±1.0)%(P=0.00)。两种癌症的实际机架角的通过率均低于零机架角,且通过率的波动范围也高于零机架角。鼻咽癌的实际机架角和零机架角剂量的通过率都比宫颈癌低。结论 实际机架角剂量验证的γ通过率更加接近真实情况,建议使用实际机架角做剂量验证;用零机架角做剂量验证,建议考虑对其通过率提出更高标准来达到临床治疗要求。

A comparative study of ArcCHECK measurements at actual and zero degree gantry angles for dose verification of intensity-modulated radiotherapy

Objective To compare the γ passing rate between measurements at actual degree gantry angle and zero degree gantry angle for dose verification of intensity-modulated radiotherapy (IMRT) in the treatment of nasopharyngeal carcinoma (NPC) and cervical carcinoma. Methods Thirty patients with NPC and thirty patients with cervical carcinoma were randomly chosen from 87 patients with NPC and 54 patients with cervical carcinoma, respectively. Using a gamma criterion of 3 mm/3%, the γ passing rates at actual gantry angle and zero degree gantry angle were measured using ArcCHECK and compared by paired t test. Results The γ passing rate was significantly lower at actual gantry angle than at zero degree gantry angle in patients with NPC or cervical carcinoma ((93.8±3.6)% vs. (97.8±1.1)%, P=0.00;(96.3±2.1)% vs. (98.2±1.0)%, P=0.00). Moreover, the variation range of the γ passing rate at actual gantry angle was larger than that at zero degree gantry angle. Both γ passing rates at actual gantryangle and zero degree gantryangle were lower in the patients with NPC than in the patients with cervical carcinoma. Conclusions
Compared with that at zero degree gantry angle, the γ passing rate at actual gantry angle is closer to reality. Therefore, the actual gantry angle is recommended for dose verification. In order to meet the clinical requirement, a higher standard of γ passing rate should be proposed when zero degree gantry angle is used for dose verification.