基于脚本的乳腺癌切线野机架角度设置

Script-based automated placement of gantry angles for tangential beams of breast cancer

目的 通过脚本寻找乳腺癌保乳术后正向调强放疗计划（fIMRT）中最优的切线野机架角度，以降低危及器官的受量。方法 采用脚本对手动布置切线野的46例（左、右两侧病例分别为26和20例）已治疗的保乳术后正向调强放疗计划进行重新设计，脚本程序由Pinnacle3计划系统内置的脚本功能配合Python语言编写。脚本程序统计保乳术后放疗患者在不同切线野角度下患侧肺V20、健侧乳腺D1和心脏V10等剂量学指数，采用罚分函数计算不同机架角度下各个危及器官的罚分值，以选取最优的切线野角度。结果 对于26例左侧乳腺癌计划，手动和脚本设置切线野患侧肺V20分别为（18.2±3.4）%和（18.1±3.4）%（P〉0.05），健侧乳腺D1分别为（249.2±88.4）和（230.4±80.2）cGy（t=2.27，P〈0.05），心脏V10分别为（13.7±5.7）%和（13.1±5.7）%（t=2.82，P〈0.05）。对于20例右侧乳腺癌计划，患侧肺的V20分别为（19.8±3.8）%和（19.8±3.9）%（P〉0.05），健侧乳腺D1分别为（340.0±286.2）和（298.0±239.7）cGy（t=2.53，P〈0.05）。结论 与手动相比，脚本能个性化、量化地评估切线野机架角度对乳腺癌危及器官受量的影响，更好地平衡各个危及器官间的受量，进一步提升计划质量。

Objective To reduce the dose to organ at risk （OAR） by script-based optimizing the gantry angles of tangential beams for forward-planned intensity-modulated breast radiotherapy （fIMRT） plans.Methods A total of 46 patients with breast cancer （26 in left and 20 in right） after conservative surgery who were treated with manually planned fIMRT were retrospectively re-planned using a script to place the tangential beams automatically. The script program was developed using Pinnacle3 scripting language as imbedded in the Pinnacle3 treatment planning system, and the Python scripting language. Dosimetric indices, including V20 of the ipsilateral lung, D1 of the contralateral breast and V10 of the heart were extracted by the script for plans of different gantry angles. Then the optimal tangential angles were selected by a penalty function.Results For the 26 left breast cancer cases, V20 of the ipsilateral lung for manual and script were （18.2±3.4）% and （18.1±3.4）%, respectively（P〉0.05）, while D1 of the contra-lateral breast（249.2±88.4） cGy and （230.4±80.2） cGy, respectively（ t=2.27, P〈0.05）, V10 of the heart （13.7±5.7）% and （13.1±5.7）%（t=2.82, P〈0.05）. The V20 of the ipsilateral lung of the 20 right breast cancer cases were （19.8±3.8）% and （19.8±3.9）%, respectively（P〉0.05）. The script plans achieved better V10 of the heart than the manual plans （t=2.53, P〈0.05）.Conclusions Compared with the manualmethod, the script can assess of the impact of tangential beam angles on the OAR dose, patient-specifically and quantitatively, hence make better trade-offs and improve the plan quality.