蒙特卡罗算法的乳腺癌术中放疗剂量优化及临床应用

目的 运用蒙特卡罗算法指导乳腺癌IORT剂量优化并评价临床应用效果。方法 利用MCTP的MCBEAM程序建立加速器乳腺癌IORT的模型,采用自主开发的编辑器将乳腺癌患者术前CT图像编辑成术中状态影像,勾画靶区并分别在靶区前后设置不同厚度等效材料和铅板,通过MCSIM程序运算得到等效材料与铅板最佳优化组合。将优化组合应用于 23例IORT患者并观察伤口愈合、不良反应、美容效果和肿瘤复发情况。结果 靶区表面加 2~3 mm等效材料、靶区后缘加5 mm等效材料和2 mm铅板,优化的乳腺癌IORT靶区剂量90%等剂量线基本包绕整个靶区,靶区 V₉₀>90%、V₁₁₀<4%,肺 D_mean<1 Gy。23例患者伤口均愈合良好,未出现感染及不良反应,愈合后和术后半年乳房外观优良率达80%以上,未发现肿瘤复发。结论 蒙特卡罗算法指导下的乳腺癌IORT剂量优化方法可靠,靶区剂量分布均匀、理想,患者无不良反应,美容效果满意,值得临床推广应用。

Monte carlo simulation based dose optimization of intra-operative radiotherapy for breast cancer and its clinical application

Objective To study Monte Carlo simulation to guide the dose optimization of intra-operative radiotherapy (IORT) for breast cancer, and evaluating its effects of clinical application. Methods The MCBEAM program of MCTP is used to establish the model of the accelerator using for breast cancer patients′ IORP. The preoperative CT images are edited to intra-operative states using independent developed editor, then determing the target at the intra-operative states and setting equivalent material and lead of different thicknesses in front of and behind the target. Calculating with the MCSIM program to get the optimal combination of the equivalent material and lead. There are 23 patients who accepted IORT with the optical combination of themselves, and the situations of wounds healing, reactions of radiotherapy, cosmetic effects and the recurrence of cancer are observed. Results By adding 2-3 mm equivalent material in front of the target and 5 mm equivalent material and 2 mm lead behind the target, the 90% isodose curve almost wraps around the target volume;and the V₉₀>90% and the V₁₁₀<4%. The average dose of lung is less than 1 Gy. The 23 patients′ wounds healed well, and there are no wounds′ infection and radiotherapy reaction;after the healing of wounds and half a year after the operation, the excellent rate of breasts′ appearance is over 80%, and no tumor recurrence was found. Conclusions The method of MC guided dose optimization of IORT for breast cancer is reliable, the dose distribution of target volume is uniform. There were no adverse reactions to radiotherapy and the cosmetic effect is satisfying. This method is well worthy of clinical popularizing.