| 王海洋,刘帅蓬,霍佳,韩滨,王芳娜,贾飞,刘乐乐,孔凡洋,裴运通,胡金炎,郭跃信.螺旋断层放疗在分段全身照射中上下靶区衔接处剂量分布的影响因素研究[J].中华放射医学与防护杂志,2018,38(12):923-927 |
| 螺旋断层放疗在分段全身照射中上下靶区衔接处剂量分布的影响因素研究 |
| Impact factors of dose distribution in the abutment area duing total body irradiation with helical tomotherapy |
| 投稿时间：2018-05-29 |
| DOI：10.3760/cma.j.issn.0254-5098.2018.12.008 |
| 中文关键词: 螺旋断层放疗 全身照射 射野宽度 螺距 靶区间隔距离 |
| 英文关键词:Helical tomotherapy Total body irradiation Field width Pitch Target gap distance |
| 基金项目:河南省科技计划项目（182102310578） |
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| 中文摘要: |
| 目的 选取10例身高在120.0 cm左右的急性白血病患者分上下两段行螺旋断层治疗（HT）实现全身照射（TBI），通过分析衔接处靶区剂量分布的变化情况，寻找最佳靶区间隔距离所对应的计划设计参数。方法 选取的研究对象使用德国Siemens公司定位CT获得层厚为5 mm的全身图像，同时在髌骨上方10 cm处放置铅丝，作为上下两段靶区的分割线。在美国瓦里安Eclipse 13.5医生工作站进行靶区和危及器官的勾画，其中上下靶区在铅丝分割处依次分别内收不同距离，然后传至HT计划工作站进行计划设计，其中射野宽度（FW）分别选择5.0、2.5、1.0 cm，螺距分别选择0.430与0.287，调制因子1.8，剂量计算网格（最精细：0.195 cm×0.195 cm），其余计划参数都保持一致。将其分两段照射的上下靶区依据不同参数进行计划设计，并将设计好的不同参数的计划分别对应叠加在一起进行分析衔接处靶区剂量分布的变化情况。结果 通过比较不同螺距和射野宽度所对应不同间隔距离的衔接处靶区的剂量分布，发现只有射野宽度才影响衔接处靶区的剂量分布：当射野宽度为5.0 cm时，靶区间隔距离为5.0 cm在衔接处的剂量分布最佳；同理当射野宽度为2.5和1.0 cm时，靶区间隔距离分别为2.0和1.0 cm时最佳，即衔接处靶区的最佳剂量分布所对应的间隔距离与射野宽度保持一致。而螺距对衔接处靶区剂量和总治疗时间比值没有影响，总治疗时间长度与射野宽度保持一致反比关系。结论 对于HT进行分段式TBI治疗时，采用如上的计划设计参数，同时靶区勾画时间隔距离与射野宽度保持一致，能保证在进行分段TBI治疗时衔接处靶区不会出现剂量冷热点，确保了治疗的精确与安全。在实际临床治疗过程中，为达到治疗效果与效率的平衡，需要选择合适的计划参数。 |
| 英文摘要: |
| Objective To investigate the optimal distance between upper and lower target volumes and their correlated planning parameters by analyzing the dose distribution in the abutment regions during total body irradiation (TBI) using helical tomotherapy.Methods A total of 10 patients with acute leukemia and with a height around 120 cm were enrolled. All patients were scanned by a Siemens simulation computerized tomography (CT) at a slice thickness of 5 mm. A lead wire was placed 10.0 cm above the patella as a marker of the separation boundary for the upper and lower target volumes. The delineations of target volumes and organs at risk (OARs) were performed in the Varian Eclipse 13.5 workstation with targets shrunk beyond the separation boundary at different distances. After contours and CT images were transferred to HT workstation, treatment plans were designed with different field width (FW, 5.0 cm/2.5 cm/1.0 cm) and pitch values (0.430/0.287) at a modulation factor of 1.8. All the plans were optimized with a dose calculation grid of 0.195 cm×0.195 cm and identical planning parameters. The correlation between treatment planning parameters and targets shrunk distances were investigated by analyzing the dose distributions in the abutment area.Results The study demonstrated that the dose distributions in the abutment area were influenced only by the field width parameters:when the gap distance between the upper and lower targets was 5.0 cm, the optimal FW is 5.0 cm; Similarly when the gap distances were 2.0 cm and 1.0 cm, and the optimal FW 2.5 cm and 1.0 cm, respectively. In another words, the dose distribution of the abutment region was optimal when the target gap distance was equal to FW. Pitch values did not affect the quality of dose distribution in the abutment region and the overall treatment time ratio. Overall treatment time was inversely related to the FW.Conclusions Consistent target distance and FW is helpful to improve the dose homogeneity in the abutment area during TBI with HT. Appropriate planning parameters is critical to balance the treatment efficacy and efficiency. |
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