A comparison of the dosimetric effects of systematic MLC leaf position errors on flattening filter and flattening filter-free IMRT for nasopharyngeal carcinoma
10.3760/cma.j.issn.0254-5098.2015.11.008
- VernacularTitle:多叶准直器整体到位偏差对有无均整器模式鼻咽癌调强放疗计划剂量学影响的比较
- Author:
Lele LIU
;
Yangguang MA
;
Guowen LI
;
Yuexin GUO
- Publication Type:Journal Article
- Keywords:
Flattening filter-free;
Multi leaf collimator;
Position error;
Intensity radiotherapy;
Dosimetry
- From:
Chinese Journal of Radiological Medicine and Protection
2015;35(11):835-838
- CountryChina
- Language:Chinese
-
Abstract:
Objective To compare the dosimetric effects of systematic MLC leaf position errors on flattening filter (FF) and flattening filter-free (FFF) IMRT for nasopharyngeal carcinoma (NPC).Methods In totaly of ten patients with NPC were enrolled in the current study.FF IMRT and FFF IMRT plans were designed for each patient, and in-house software was developed to modify the corresponding MLC files.Briefly, three kinds of systematic MLC error presented with 0.5 and 1 mm magnitudes error were simulated.The modified MLC files were re-imported into IMRT plans for dose recalculation, and differences in the dosimetry trends between FF-IMRT and FFF-IMRT plans were analyzed using a dosevolume histogram.Results Upon closed MLC, the average changes in D95％ of PTV and D of parotid glands in FFF-IMRT plans were more sensitive than in FF-IMRT plans (t =3.298-4.793, P ＜ 0.05).Otherwise, when MLC are shifted in the same direction, changes in D95％of PTV, D of PGTV, PTV as well as D of left parotid gland in FFF-IMRT plans were also more sensitive (t =2.372-6.844, P ＜ 0.05), whereas average changes in D of right parotid gland presented with less sensitivity (t =-4.049,-3.378, P ＜ 0.05).Conclusions For out-of-field or large organs, FFF-IMRT plans are more sensitive to leaf position error than FF-IMRT plans.
