呼吸门控技术在肝癌大分割放射治疗方面的剂量学优势

Dosimetry advantage of respiratory gating in the treatment of hepatocellular carcinoma with large segmentation

目的探讨呼吸门控(Gating)技术在原发性肝癌大分割放射治疗方面的剂量学优势。方法回顾性分析2017年8月—2018年11月10例原发性肝癌患者介入治疗后应用呼气末3个连续时相实现门控式大分割放疗的患者资料。10例患者行4DCT定位扫描,通过呼吸波形重建10组呼吸时相序列,将图像传输至MIM6.7.6工作站。在MIM工作站中分别生成全时相最大密度投影(MIP-10)、全时相平均密度投影(Mean-10)、呼气末3时相最大密度投影(MIP-3)、呼气末3时相平均密度投影(Mean-3),其中MIP用于靶区勾画,Mean用于剂量计算。放疗医师在MIM工作站上勾画IGTV-10、IGTV-3,并外放生成CTV-10、CTV-3、PTV-10、PTV-3,比较靶区体积差异。靶区勾画完毕后将图像从MIM工作站传输至Eclipse治疗计划系统,分别制定条件相同的全时相计划(Plan-10)和呼气末3个连续时相门控计划(Plan-3),处方剂量给予50 Gy/10 f/2 weeks。比较靶区的HI和CI,危及器官的比较包括肝脏平均照射剂量Dmean、肝脏受到小于15 Gy的照射体积、小肠Dmax、结肠Dmax、胃Dmax、肾脏平均照射剂量Dmean、心脏Dmax、脊髓Dmax。结果呼气末3时相勾画的靶区体积在IGTV、CTV、PTV方面均小于全时相勾画的靶区体积,差异有统计学意义(P<0.05)。在制定的两组7野共面大分割放疗计划方面,3时相门控计划明显降低了各危及器官的照射剂量,差异有统计学意义(P<0.05)。同时两组计划的均匀性指数(HI)和适型性指数(CI)差异无统计学意义(P>0.05)。结论呼吸末3个连续时相的门控式靶区勾画和计划设计方式较全时相的选择相比缩小了IGTV、CTV、PTV靶区的体积,并在计划剂量学方面有明显优势,降低了危及器官的照射剂量,在肝癌大分割放疗方面值得被推广运用。

Objective The aim of this study was to investigate the dosimetric advantages of Gating in the treatment of primary hepatic cancer with large segmentation.Methods A retrospective analysis of 10 patients with primary liver cancer from August 2017 to November 2018 after interventional therapy was performed using three consecutive phases of end-tidal phase to achieve patient-controlled large-segment radiotherapy.Ten patients underwent 4DCT localization scan,and 10 respiratory phase sequences were reconstructed by respiratory wave-form,and the images were transmitted to the MIM6.7.6 workstation.In the MIM workstation,full-time phase maximum density projection(MIP-10),full-time phase average density projection(Mean-10),end-expiration 3 phase maximum density projection(MIP-3)and end-expiration 3 phase average density projection(Mean-3)were generated respectively,where MIP was used for target delineation and Mean for dose calculation.The radiotherapy doctor delineated IGTV-10 and IGTV-3 on the MIM workstation,and released CTV-10,CTV-3,PTV-10 and PTV-3 to compare the volume differences of the target area.After the target area was drawn,the image was transmitted from the MIM workstation to the Eclipse treatment planning system,and the full-time phase plan(Plan-10)with the same conditions and three consecutive phase-phase gating plans(Plan-3)were prepared.The prescriptive dosage was given at 50 Gy/10 f/2weeks.Comparing the HI and CI of the target area,the comparison of organs at risk included the average dose of liver Dmean,the irradiation volume of liver less than 15Gy,the Dmax of small intestine,the Dmax of colon,the Dmax of stomach,the average dose of the kidney Dmean,the heart Dmax,and the spinal cord Dmax.Results The volume of the target area delineated at the end of expiratory phase was less than that of the target area outlined by the full-time phase in IGTV,CTV and PTV,and the difference was statistically significant(P<0.05).In the two groups of seven field coplanar lage-segment radiotherapy plans,the 3-phase respiratory gating plan significantly reduced the dose of the organs at risk,and the difference was statistically significant(P<0.05).At the same time,there was no statistically difference in the HI and CI between of the two groups(P>0.05).Conclusion The gated target area delineation and planning design of the three consecutive phases of end-tidal phase reduce the volume of IGTV,CTV and PTV target regions compared with the selection of full-time phase,and have obvious advantages in the planned dosimetry.The irradiation dose that threatens the organs is worthy of being promoted and applied in the large-scale radiotherapy of liver cancer.