基于KV-CBCT影像引导下非小细胞肺癌自适应放疗可行性研究

Feasibility Study of Adaptive Radiotherapy for Non Small Cell Lung Cancer Guided by Kilo-Voltage Cone Beam CT Image

目的基于千伏级锥形束CT(Kilovolt Cone-Beam Computed Tomography,KV-CBCT)非小细胞肺癌(Non-Small Cell Lung Cancer,NSCLC)患者第1周放疗前扫描的锥形束CT(Cone-Beam Computed Tomography,CBCT)图像设计的自适应放疗计划,比较自适应放疗前后放疗计划的剂量学差异,以及探讨自适应放疗应用于NSCLC患者放疗的可行性。方法选取行调强放疗的NSCLC患者15例,将首周每天1次和后续每周1次获得的CBCT验证图像传入Eclipse计划系统与定位CT图像融合配准后,在CBCT图像上重新勾画大体肿瘤体积(Gross Tumor Volume,GTV)、临床靶区体积(Clinical Target Volume,CTV),将首周CBCT图像勾画的CTV拷贝到定位CT中合成并命名为临床靶区体积(Clinical Target Volume,CTVa),并依据首周测量的摆位误差外扩生成计划靶体积(Plan Target Volume,PTVa),同理获得后续几周的计划靶体积(Plan Target Volume,PTVb)。保持最初治疗计划的射束和优化条件等参数不变,针对PTVa重新设计出自适应放疗计划(Adaptive Radiation Therapy,ARTa),进一步比较自适应放疗前后放疗计划的剂量学差异,同时在ARTa中评估PTVb的剂量覆盖率。结果PTVa的体积小于初始靶区PTV,差异具有统计学意义(P<0.05);ARTa处方剂量的体积覆盖率为96.2%±1.7%,优于批准计划(Planapproved)的95.1%±2.3%,差异有统计学意义(P<0.05),且在ARTa中,PTVa的处方剂量线能使PTVb体积覆盖率达到96.8%±1.7%;ARTa中肺组织(V_(5)、V_(10)、V_(20)、V_(30)、D_(mean))、心脏(V_(30)、V_(40)、D_(mean))、脊髓(D_(max)、D_(mean))均较Planapproved有所降低,且两两比较差异有统计学意义(P<0.05)。结论使用患者首周CBCT提供的反馈进程(空间位移、解剖形变)重新设计的ARTa可以用于患者后续的放疗中,并能够减少重要器官的照射剂量和提高靶区剂量,进而有利于提高非小细胞肺癌肿瘤增益比。

Objective To compare the dosimetric differences of the plans before and after the adaptive radiotherapy,to investigate the feasibility of the application of adaptive radiotherapy in patients with non-small cell lung cancer(NSCLC)bases on an adaptive radiotherapy program that is designed with the cone-beam computed tomography(CBCT)images scanned before 1 week radiotherapy in NSCLC patients with kilovolt cone-beam computed tomography(KV-CBCT).Methods Fifteen NSCLC patients treated by intensity-modulated radiotherapy were selected.The CBCT verification images obtained once a day in the first week and once a week in the following weeks were imported into the Eclipse planning system and fused with the positioning CT images for registration.The gross tumor volume(GTV)and clinical target volume(CTV)were re-delineated on CBCT images.The CTV outlined in the CBCT images of the first week was copied into the positioning CT and synthesized,named clinical target volume(CTVa),and the plan target volume(PTVa)was generated based on the positioning error measured in the first week.Similarly,plan target volume(PTVb)in the following weeks were obtained.Keeping the beam and optimization parameters of the original treatment plan unchanged,adaptive radiation therapy(ARTa)was redesigned for PTVa to further compare the dosimetry differences of radiotherapy plans before and after adaptive radiotherapy,and the dose coverage of PTVb was evaluated in ARTa.Results The volume of PTVa was smaller than that of initial target PTV,and the difference was statistically significant(P<0.05).The volume coverage rate of prescription dose of ARTa was 96.2%±1.7%,and it was better than the Planapproved(95.1%±2.3%),the difference was statistically significant(P<0.05).In addition,in ARTa,PTVa prescription dose line could make PTVb prescription dose coverage rate reach 96.8%±1.7%.The lung tissue(V_(5),V_(10),V_(20),V_(30),D_(mean)),heart(V_(30),V_(40),D_(mean))and spinal cord(D_(max),D_(mean))in ARTa were lower than those in planapproved,and there were statistical significance between them(P<0.05).Conclusion Redesigned ARTa using the feedback process(spatial displacement and anatomical deformation)provided by patients first week of CBCT can be used in the later radiotherapy;ARTa can reduce the radiation dose of important organs as much as possible,which provides a possible space for the increase of target dose.This helps to improve the therapeutic ratio of NSCLC treatment.