系统摆位误差对保护海马脑预防照射的剂量学影响-《中国医学物理学杂志》

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Title:: Dosimetric effects of systematic setup errors on hippocampus sparing prophylactic cranial irradiation

文章编号:: 1005-202X（2021）08-0930-05

作者:: 王攀; 陈俊杰; 赵婷; 杨万福; 孔伟; 叶红强; 尚钧; 宁夏医科大学总医院肿瘤医院放疗科，宁夏银川 750004

Author(s):: WANG Pan; CHEN Junjie; ZHAO Ting; YANG Wanfu; KONG Wei; YE Hongqiang; SHANG Jun; Department of Radiotherapy, Cancer Hospital, General Hospital of Ningxia Medical University, Yinchuan 750004, China

关键词:: 海马; 脑预防照射; 系统摆位误差; 剂量分布

Keywords:: Keywords: hippocampus prophylactic cranial irradiation systematic setup error dose distribution

分类号:: R815.6

DOI:: DOI:10.3969/j.issn.1005-202X.2021.08.002

文献标志码:: A

摘要:: 目的：研究不同系统摆位误差对肺癌的保护海马脑预防照射剂量分布的影响。方法：随机选取20例肺癌脑预防照射患者，均采取保护海马的脑预防照射。通过在计划系统中移动治疗计划的等中心，分别模拟患者在三维6个方向上1、3和5 mm系统摆位误差。移动等中心后的计划，在不做通量计算的情况下，重新计算剂量分布。分析在不同系统摆位误差下，靶区和危及器官剂量分布的变化情况以及系统摆位误差对靶区和危及器官剂量影响的灵敏度。结果：系统摆位误差为1、3和5 mm时，CTV D90在三维6个方向的剂量变化均值均未超过2%。误差为1 mm时，CTV D90的剂量变化仅脚方向有统计学意义（P<0.05）；误差为3 mm时，CTV D90的剂量变化仅头脚方向有统计学意义（P<0.05）；误差为5 mm时，CTV D90的剂量变化仅头脚方向和背部方向有统计学意义（P<0.05）。系统摆位误差为1 mm时，海马体剂量变化均值在左右方向和头脚方向均大于3%；系统摆位误差为3、5 mm时，海马在三维6个方向的剂量变化均值均超过10%；对于海马剂量变化，仅1 mm误差下背部方向无统计学意义（P>0.05），其余误差下所有方向的剂量变化，有统计学意义（P<0.05）。系统摆位误差为1 mm时，海马、左右眼球和左右晶体剂量变化大于5%的占比分别是26.19%、26.20%、26.19%、10.71%、17.86%；系统摆位误差为3 mm时，海马、左右眼球、左右晶体和左右视神经剂量变化大于10%的占比分别是97.62%、69.05%、66.67%、30.95%、25.00%、1.19%、3.57%。靶区和海马均在头脚方向误差敏感度最大。结论：系统摆位误差对CTV剂量影响较小，CTV外扩3 mm形成的PTV足以保证靶区接受足够的处方剂量的照射。危及器官尤其是海马、眼球和眼晶体对系统摆位误差尤为敏感，且误差越大对剂量分布的影响越大。因此在实际治疗的过程中要严格控制摆位误差尤其是头脚方向的摆位误差。

Abstract:: Abstract: Objective To investigate the effects of different systematic setup errors on the dose distribution in hippocampus sparing prophylactic cranial irradiation for lung cancer. Methods A total of 20 lung cancer patients were randomly selected, and all of them received hippocampus sparing prophylactic cranial irradiation. The systematic setup errors of 1, 3 and 5 mm in three-dimensional 6 directions were simulated by moving the isocenter of the treatment plan in treatment planning system, respectively and then the dose distributions of the generated plans with different systematic setup errors were recalculated without flux calculation. Under different systematic setup errors, the changes of dose distribution in target area and organs-at-risk to systematic setup errors were analyzed, and the sensitivity of dosimetric parameters of target areas and organs-at-risk were discussed. Results The mean dose deviation of CTV D90 did not exceed 2% in the 6 directions with the systematic setup errors of 1, 3 and 5 mm. The significant dose variation of CTV D90 was only found in inferior direction (systematic setup error of 1 mm), in superior and inferior directions (systematic setup error of 3 mm), and in superior, inferior and posterior directions (systematic setup error of 5 mm) (all P<0.05). When the systematic setup error was 1 mm, the mean dose deviation of the hippocampus was greater than 3% in left-right and superior-inferior directions. With the systematic setup error of 3 mm and 5 mm, the mean dose deviation of the hippocampus was more than 10% in the 6 direction. Except for the hippocampus dose deviation in posterior direction under the systematic setup error of 1 mm (P>0.05), the hippocampus dose deviations were statistically significant (P<0.05). When the systematic setup error was 1 mm, the proportions of the dose deviations greater than 5% for hippocampus, left and right eyeballs and left and right lens were 26.19%, 26.20%, 26.19%, 10.71% and 17.86%, respectively. When the systematic setup error was 3 mm, the proportions of the dose deviation greater than 10% for hippocampus, left and right eyeballs, left and right lens and left and right optic nerve was 97.62%, 69.05%, 66.67%, 30.95%, 25.00%, 1.19% and 3.57%, respectively. Both target area and the hippocampus had the highest error sensitivity in superior-inferior direction. Conclusion Systematic setup error has little effect on CTV dose distribution, and the PTV formed by CTV with an expansion of 3 mm is adequate to ensure that the target area receives sufficient prescription dose. Organs-at-risk, especially the hippocampus, eyeball and lens, are particularly sensitive to systematic setup error. The larger the error is, the greater the effect on the dose distribution is. Therefore, in treatment practice, it is necessary to strictly control the setup error, especially the setup error in superior-inferior direction.

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《中国医学物理学杂志》[ISSN:1005-202X/CN:44-1351/R]

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