通过剂量验证检测MLC运动的准确性

Accuracy detection of multileaf collimator movement by dose verification

目的:通过剂量学验证检测加速器多叶准直器(multi-leaf collimator,MLC)运动的准确性。方法:使用MatriXX测量Open野与MLC动态射野的剂量分布,验证5例鼻咽癌动态调强放疗患者在MLC校准前后的剂量分布。结果:(1)Open野的中心点剂量与TPS一致,3%/3 mmγ通过率为98.91%;(2)MLC动态射野的中心点剂量测量值和TPS的差异校准前和校准后分别为3.23%和-0.36%,校准前和校准后3%/3 mmγ通过率分别为95.89%和98.94%;(3)5例鼻咽癌患者计划校准前后3%/3 mmγ通过率分别为(90.234±5.485)%和(99.528±0.321)%。结论:动态调强放疗中MLC的运动精度直接影响靶区内的剂量准确性,通过剂量学验证可以检测MLC运动的准确性。

Objective To detect the accuracy of the muhileaf collimator （MLC） by dose verification. Methods MatriXX was used to measure the dose distribution of Open field and dynamic MLC field. The dose distribution of 5 patients with nasopharyngeal carcinoma （NPC） treated with dynamic IMRT was verified before and after MLC calibration. Results The absolute dose of centre points of Open field were consistent with TPS, and 3%/3 mm γ passing rate was 98.91%. The abso- lute dose of centre points of dynamic MLC field was different with TPS by 3.23% before calibration while -0.36% after calibration, and 3%/3 mm γ passing rate was 95.89% before calibration while 98.94% after calibration. The 3%/3mm γ passing rate of the five patients was （90.234±5.485）% and （99.528±0.321）% respectively before and after calibration. Conclusion The motion accuracy of the MLC directly influences the dose accuracy of the target volume, and the dose veri-fication can test the motion accuracy of MLC.