Eclipse计划系统NTO优化对宫颈癌调强放疗计划的影响

Influence of NTO Optimization on Eclipse Treatment Planning System for Cervical Cancer Intense-Modulated Radiotherapy

目的探讨Eclipse上的优化工具正常组织目标(Normal Tissue Objective,NTO)对宫颈癌调强放疗(Intensity Modulated Radiotherapy,IMRT)的剂量学影响,为宫颈癌IMRT计划设计提供参考。方法对20例宫颈癌术后患者做回顾研究,为每个患者制订7组逆向IMRT计划。首先使用自动NTO作为对照组,其他6种计划在相同的优化条件下改为手动NTO,剂量跌落值K依次为0.01、0.1、0.3、0.5、1和5。靶区处方剂量均为4600 cGy/25 F,分析各计划靶区的D_(2)、D_(98)、D_(mean)和适形性指数(Conformity Index,CI)、均匀性指数(Homogeneity Index,HI),正常组织(Body-PTV)和危及器官(Organ at Risk,OAR)膀胱、直肠、股骨头、小肠和骨盆的剂量学。结果与对照组相比,K=0.3及以上时CI更好,K=0.5及以上时HI更差(P<0.05)。与对照组相比,膀胱D_(40)在K=1和5计划组更小(P<0.05);直肠D_(40)结果无统计学差异(P>0.05);左股骨头D_(25)在K=1、5计划组更大(P<0.05);右股骨头D_(25)在K=5计划组较大(P<0.05);小肠D_(max)在K=1、5计划组较大(P<0.05);骨盆在K=0.01计划组较小。正常组织K值较小时,低剂量体积较小,高剂量体积较大;K值较大时,低剂量体积较大,高剂量体积较小。对照组的机器跳数比其他6组都小(P<0.05)。结论在宫颈癌IMRT计划设计中,手动NTO与自动NTO相比,靶区和OAR及正常组织受量没有体现出绝对优势,但是自动NTO的机器跳数更小,能减轻机器负担,建议宫颈癌IMRT临床使用自动NTO。

Objective To explore the influence of the optimization tool normal tissue objective(NTO)on Eclipse on the dosimetry of intensity modulated radiotherapy(IMRT)for cervical cancer,and to provide a reference for the design of cervical cancer IMRT.Methods A retrospective study was conducted on 20 patients with cervical cancer after surgery,and 7 groups of reverse IMRT plans were developed for each patient.First,automatic NTO was used as the control group,and the other 6 plans were changed to manual NTO under the same optimized conditions,and the dose drop value K was 0.01,0.1,0.3,0.5,1,and 5 in order.The prescribed dose of the target area was 4600 cGy/25F.The D_(2),D_(98),D_(mean),conformity index(CI),homogeneity index(HI)and normal tissue(Body-PTV)of each planned target area,and organ at risk(OAR)dosimetry of bladder,rectum,femoral head,small intestine,and pelvis were analyzed.Results Compared with the control group,the CI was better when K=0.3 and above,and the HI was worse when K=0.5 and above(P<0.05).Compared with the control group,the bladder D_(40)was smaller in the K=1 and 5 plan groups(P<0.05);the rectum D_(40)results were not statistically different(P>0.05);the left femoral head D_(25)was higher in the K=1 and 5 plan groups(P<0.05);the right femoral head D_(25)was larger in the K=5 plan group(P<0.05);the small intestine D_(max)was larger in the K=1 and 5 plan groups(P<0.05);the pelvis was smaller in the K=0.01 plan group.When the K value of normal tissue was small,the volume of the low dose was smaller and the volume of the high dose was larger;when the value of K was larger,the volume of the low dose was larger,and the volume of the high dose was smaller.The number of monitor unit in the control group was smaller than that of the other 6 groups(P<0.05).Conclusion In the design of cervical cancer IMRT plan,manual NTO has no absolute advantage over automatic NTO in terms of target volume,OAR and normal tissues.However,automatic NTO has a smaller number of machine hops,which can reduce the burden on the machine.Automatic NTO is recommended for clinical use in cervical cancer IMRT.