以CT图像为基础的宫颈癌三维腔内放疗

目的 探讨CT模拟图像引导下宫颈癌三维腔内放疗实施的可行性及意义。方法 对12例根治性放疗宫颈癌患者的55次腔内施源器置入CT图像,分别设计二维、三维计划,并行配对t检验、Wilcoxon符号秩检验、Pearson相关分析、Spearman相关分析。结果 三维计划双侧A点剂量、D₉₀、V₁₀₀、CI、CI′均高于二维(P=0.015、0.016、0.000、0.000、0.000),三维计划的膀胱、直肠点剂量及直肠D_{2 cm³}略高于二维计划,但热点剂量明显减少。两组计划的膀胱、乙状结肠、小肠D_{2 cm³}相近(P=0.140、0.123、0.214)。膀胱D_{2 cm³}明显高于膀胱点剂量(P=0.000)。乙状结肠D_{2 cm³}较直肠D_{2 cm³}与直肠最高3点剂量平均值更相关(r=0.314、0.63,P=0.000、0.000)。V₁₀₀与高危CTV体积呈线性关系(r=0.981,P=0.000)。膀胱D_{2 cm³}在膀胱体积>80 cm³后达430 cGy以上,小肠D_{2 cm³}在膀胱体积<115 cm³内变化不明显,一旦超过明显下降。结论 CT引导下宫颈癌三维腔内放疗较传统二维腔内放疗显著增加了靶区覆盖率、提高了适形度,但未明显增加OAR剂量且能及时发现减少OAR热点剂量。点剂量评估并不准确。可以通过膀胱体积调控膀胱、直肠、小肠剂量。

A clinical study of CT image-based 3D brachytherapy for cervical cancer

Objective To evaluate the feasibility and significance of CT image-based three-dimensional (3D) brachytherapy for cervical cancer. Methods Three-dimensional (3D) plan and two-dimensional (2D) plan were designed for 55 CT images of brachytherapy from 12 cervical cancer patients who received radical radiotherapy in 2013. Dosimetric comparison was performed between the 3D plan and 2D plan, and paired t-test, Wilcoxon signed rank test, Pearson correlation analysis, and Spearman correlation analysis were performed. Results A point dose, D₉₀, V₁₀₀, CI, and CI′ in 3D plan were higher than those in 2D plan (P=0.015,0.016,0.000,0.000,0.000). Bladder point dose, rectal point dose, and rectal D_{2 cm³} in 3D plan were slightly higher than those in 2D plan, but hot spot dose was significantly reduced in 3D plan (P=0.140,0.123,0.214). Bladder D_{2 cm³} was significantly higher than bladder point dose (P=0.000). Sigmoid colon D_{2 cm³} was more correlated with the average doses of the three highest rectal points than rectal D_{2 cm³}(r=0.314,0.630, P=0.000,0.000). V₁₀₀ showed a linear relationship with high-risk CTV (r=0.981, P=0.000). Bladder D_{2 cm³} was higher than 430 cGy when the bladder volume was more than 80 cm³;small intestinal D_{2 cm³} did not change significantly when the bladder volume was less than 115 cm³, but decreased significantly once the volume exceeded the value. Conclusions Compared with the traditional 2D plan, the 3D plan for CT image-based cervical cancer brachytherapy significantly increases the target coverage and conformity index, but does not significantly increase the doses to organs at risk. Point dose evaluation is confirmed to be inaccurate. The doses to the bladder, rectum, and small intestine can be adjusted by controlling the bladder volume.