通量平滑度对直肠癌术后调强计划的剂量影响

目的 对比Monaco系统4种通量平滑度（Fluence-smoothing,FS）等级在直肠癌术后调强适形放射治疗技术（Intensity-Modulated Radiation Therapy,IMRT）中的剂量学差异,为临床选择FS参数提供参考。方法 选取2020年入院的15例直肠癌术后病例,在相同优化条件下,分别设置FS为Off、Low、Medium 和High进行计划设计,采用SPSS 20.0软件对数据进行统计分析;比较4种FS下靶区及危及器官（Organs at risk,OARs）的剂量参数、子野数（Segments）、机器跳数（Monitor units,MUs）、剂量计算时间（Estimated total delivery time,ETDT）及γ通过率。结果 4种FS下,靶区及OARs的剂量参数均满足临床需求,且不同FS等级下剂量分布差异无统计学意义;由FS-Off至FS-High,Segments、MUs及ETDT分别平均减少了15.2%、11.8%、6.7%,γ通过率提高了1.6%。结论 4种FS下IMRT计划均能满足临床要求,综合考虑计划质量和执行效率,建议采用FS-High用于直肠癌术后调强适形放射治疗。

Dose effect of fluence-smoothing on intensity modulated planning after rectal cancer surgery

Objective To compare the dosimetric differences of four fluence smoothing (FS) levels of the Monaco system in intensity-modulated radiation therapy (IMRT) after rectal cancer surgery, and to provide a reference for FS selection in clinical practice. Methods A total of 15 postoperative patients with rectal cancer admitted in 2020 were selected. Under the same optimal conditions, FS was set to Off, Low, Medium, and High for IMRT planning. The data were analyzed by SPSS 20.0 software. The dosimetric parameters of planning target volume and organs at risk (OARs), the number of Segments, the number of monitor units (MUs), the estimated total delivery time (ETDT), and the gamma pass rate were compared between the four FS levels. Results The four FS levels resulted in clinically acceptable dosimetric parameters of the planning target volume and OARs, and there was no significant difference in dose distribution between FS levels. From FS-Off to FS-High, number of Segments, number of Mus, and ETDT decreased by 15.2%, 11.8%, and 6.7%, respectively, whereas gamma pass rate increased by 1.6%. Conclusion The IMRT plans at four FS levels can meet the clinical requirements. Considering the planning quality and execution efficiency, FS-High is recommended for postoperative IMRT of patients with rectal cancer.