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  

A comparison of the dosimetric effects of systematic MLC leaf position errors on flattening filter and flattening filter-free IMRT for nasopharyngeai carcinoma

作　　者：刘乐乐[1] 马阳光[1] 李国文[1] 郭跃信[1] 

机构地区：[1]郑州大学第一附属医院放射治疗部,450052

出　　处：《中华放射医学与防护杂志》2015年第11期835-838,共4页Chinese Journal of Radiological Medicine and Protection

摘　　要：目的研究多叶准直器（MLC）整体到位偏差对均整器（FF）和无均整器（FFF）模式的鼻咽癌固定野调强计划剂量学影响的比较。方法选取10例鼻咽癌患者，分别设计FF和FFF调强计划。修改两种计划的MLC文件，人为引入0．5和1mm两种偏移量的3种MLC整体到位偏差。重新计算修改MLC文件后的调强计划的剂量分布，比较两种射束模式调强计划的剂量学变化趋势。结果与FF计划比较，MLC整体闭合时，FFF计划的靶区D95%和两侧腮腺的Dmean对MLC到位偏差的敏感性稍高（t=3．298—4．793，P〈0．05）；MLC整体平移时，FFF计划靶区Dmean、D98%和左侧腮腺的Dmean对MLC到位偏差的敏感性稍高（t=2．372～6．844，P〈0．05），但是右侧腮腺的Dmean却表现出较低的敏感性（t=-4．049、-3．378，P〈0．05）。结论对于射野外的器官或体积较大器官，无均整器模式比均整器模式计划对MLC整体到位偏差表现出更高的敏感性。Objective To compare the dosimetric effects of systematic MLC leaf position errors on flattening filter （FF） and flattening filter-free [ FFF） JMRT 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 dose- volume 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.

关 键 词：非均整器模式 多叶准直器 到位偏差 调强放射治疗 剂量学 

分 类 号：R739.63[医药卫生—肿瘤]