宫颈癌3DBT直肠实测剂量与参考剂量相关性研究

目的 探讨宫颈癌3DBT中直肠实测剂量与参考剂量的相关性, 评估直肠实测剂量的意义。方法 选取50例行宫颈癌根治性放疗患者, 在完成全盆腔外照射后行三维近距离治疗(3DBT)。依据ICRU38号报告推荐的直肠监测方法, 通过在体监测得到直肠实测剂量、参考点剂量(D_ICRU)及D_{2.0 cm³}, 在计划系统中得到计划剂量。应用配对t检验比较它们的差异, 采用Pearson法进行相关分析。结果 直肠实测剂量大于计划剂量(3.48∶3.25, P=0.000)、小于D_ICRU (3.48∶3.71, P=0.000)和D_{2.0 cm³}(3.48∶3.87, P=0.002)。直肠实测剂量与计划剂量存在线性关系, 二者偏差百分数为－20%~40%, 偏差平均数为8.16%, 其中63%宫颈癌患者偏差<±10%, 最大偏差达60%。实测剂量与D_ICRU相关性强(r=0.722)、与D_{2.0 cm³}相关性弱(r=0.284)。结论 宫颈癌3DBT中直肠实测剂量存在一定偏差, 但与计划剂量呈线性相关。实测剂量及计划剂量均会低估直肠剂量参考点剂量。直肠在体监测方法可作为有效的质量控制手段。

Correlation between the dose measured in the rectum and reference dose in three-dimensional brachytherapy for cervical cancer

Objective To explore the correlation between the dose measured in the rectum and reference dose in three-dimensional brachytherapy (3DBT) for cervical cancer, and to evaluate the significance of the dose measured in the rectum. Methods Fifty patients receiving radiotherapy for cervical cancer were selected, and 3DBT was performed after pelvic external beam radiotherapy. According to the rectal monitoring method recommended in the report ICRU38, in vivo monitoring was applied to obtain the dose measured in the rectum, reference point dose (D_ICRU), and D_{2 cm³}, and the planned dose was obtained from the planning system. The differences in these values were determined by the paired t-test and correlation analysis was performed with Pearson test. Results The dose measured in the rectum was higher than the planned dose (3.48 vs. 3.25, P=0.000), and lower than D_ICRU (3.48 vs. 3.71, P=0.000) and D_{2 cm³}(3.48 vs. 3.87, P=0.002). A linear relationship existed between the dose measured in the rectum and the planned dose, with a deviation percentage of －20% to 40% and an average deviation of 8.16%;63% of the patients with cervical cancer had a deviation of<±10%;the maximum deviation was 60%. The dose measured in the rectum had a strong correlation with D_ICRU (r=0.722), but a weak correlation with D_{2 cm³}(r=0.284). Conclusions During 3DBT for cervical cancer, the dose measured in the rectum has certain deviations, but has a linear correlation with the planned dose. Both the dose measured and the planned dose underestimate the dose at the reference point in the rectum, and in vivo rectal monitoring may be an effective method for quality control.