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目的胸部肿瘤患者在放疗时,基于人性化治疗原则会给予覆盖物。本研究探讨覆盖物对胸部肿瘤放疗计量学的影响。方法选取上海交通大学胸科医院放疗科收治的10例胸部肿瘤患者,年龄57~68岁;包括局限期中上段食管癌7例(锁骨上淋巴结转移),胸腺瘤3例。比较测量和计算条件下不同大小射野模体不同深度处覆盖物对点剂量和面剂量影响,研究覆盖物对模体内剂量建成影响,评价覆盖物对10例胸部肿瘤治疗计划计算剂量影响。结果测量条件下,SAD=100cm,覆盖物使5cm×5cm、10cm×10cm和20cm×20cm射野固体水模体板表面下1cm处剂量分别增加2.5%、2.14%和1.61%;2、3、4、5和10cm深度处,覆盖物降低剂量约-0.18%~-0.47%。计算条件下,覆盖物对剂量影响与测量情况基本相当。覆盖物对模体表面到1.4cm深度TPS计算剂量有不同程度提升,1.5~1.6cm深度是覆盖物对组织剂量的平衡区,超过1.6cm深度剂量稍微降低。测量及计算条件下覆盖物降低模体2、3、4和5cm深度处平面各点剂量在-0.61%左右。覆盖物使PTV平均剂量和D95分别减小-0.77%(P<0.001)和-0.93%(P<0.001)。结论覆盖物对肿瘤患者体内剂量影响随深度而变化,特别对胸部肿瘤会造成靶区照射剂量偏差。
The purpose of chest cancer patients in radiotherapy, based on the principles of human treatment will be given coverage. This study explored the impact of cover on the radiotherapy-based metrology of thoracic tumors. Methods Ten cases of thoracic tumors admitted to Department of Radiotherapy, Shanghai Jiao Tong University Thoracic Hospital were enrolled, aged 57-68 years old. They included 7 cases of upper esophageal cancer (supraclavicular lymph node metastasis) and thymoma in 3 cases. The dose and surface dosage of coverings at different depths were compared under the conditions of measurement and calculation. The effect of cover on the dosage in the model body was evaluated. The effects of cover on the dose of the chest treatment plan were evaluated. Results Under the conditions of measurement, SAD = 100cm, the coverage increased 2.5%, 2.14% and 1.61% respectively at the surface of 5cm × 5cm, 10cm × 10cm and 20cm × 20cm radio field solid plate. At depths 4, 5 and 10 cm, the cover reduces the dose by about -0.18% -0.47%. Under the conditions of calculation, the influence of the covering on the dose is basically the same as the measurement. Cover the body surface to the depth of 1.4cm TPS calculated dose increase in varying degrees, 1.5 ~ 1.6cm depth is the coverage of tissue dose balance zone, more than 1.6cm depth dose slightly reduced. Under the conditions of measurement and calculation, the covering reduces the dose of the plane at the depths of 2, 3, 4 and 5 cm at the points of -0.61%. The overlay reduced the mean PTV dose and D95 by -0.77% (P <0.001) and -0.93% (P <0.001), respectively. Conclusion The influence of overlay on the dose of tumor patients varies with the depth, especially the target tumor dose will be deviated from the chest tumor.