Nielsen Anders W Mølby, Spejlborg Harald, Lutz Christina Maria, Rugaard Poulsen Per, Offersen Birgitte Vrou
Department of Experimental Clinical Oncology, Aarhus University Hospital, Aarhus, Denmark.
Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark.
Phys Imaging Radiat Oncol. 2023 Jul 12;27:100470. doi: 10.1016/j.phro.2023.100470. eCollection 2023 Jul.
Chest wall movement during radiotherapy can impact the delivered dose to the internal mammary nodes (IMN) in high-risk breast cancer patients. Using portal imaging and dose reconstruction we aimed to examine the delivered IMN dose coverage.
Cine MV images were recorded for 39 breast cancer patients treated with daily image-guided radiotherapy (IGRT) in deep-inspiration breath-hold (DIBH). On the final frame of each cine MV recording the chest wall was matched with the Digitally Reconstructed Radiograph (DRR) from the treatment plan. The geometrical chest wall error was determined in the imager-plane perpendicular to the cranio-caudal direction, rounded to integer millimeters, and binned. For each 1 mm bin, an isocenter-shifted treatment plan was recalculated assuming that the projected error observed in the cine MV image was caused by anterior-posterior chest wall movement in the IMN region. A weighted plan sum yielded the IMN clinical target volume receiving at least 90% dose (V90_CTVn_IMN).
The mean number of cine MV observations per patient was 36 (range 26-55). Most patients (67%) had on average a posterior chest wall position at treatment compared to planned. This translated into a change in the delivered median V90_CTVn_IMN of -0.7% (range, -11.9-2.9%; p < 0.001). The V90_CTVn_IMN reduction was greater than 9% in three patients. No clinically relevant differences were found for the mean lung dose or mean heart dose.
Using cine MV images, we found that the delivered V90_CTVn_IMN was significantly lower than planned. In 8% of the patients, the V90_CTVn_IMN reduction exceeded 9%.
放疗期间胸壁运动可能会影响高危乳腺癌患者内乳淋巴结（IMN）的受照剂量。我们旨在通过门静脉成像和剂量重建来检查IMN的实际受照剂量覆盖情况。
对39例接受每日图像引导放疗（IGRT）的乳腺癌患者在深吸气屏气（DIBH）状态下记录电影MV图像。在每个电影MV记录的最后一帧，将胸壁与治疗计划中的数字重建射线照片（DRR）进行匹配。在垂直于头脚方向的成像平面中确定几何胸壁误差，四舍五入到整数毫米并进行分组。对于每个1毫米的分组，假设电影MV图像中观察到的投影误差是由IMN区域的前后胸壁运动引起的，重新计算等中心移位的治疗计划。加权计划总和得出接受至少90%剂量的IMN临床靶体积（V90_CTVn_IMN）。
每位患者电影MV观察的平均次数为36次（范围为26 - 55次）。与计划相比，大多数患者（67%）在治疗时平均胸壁处于后位。这导致实际V90_CTVn_IMN的中位数变化为 -0.7%（范围为 -11.9% - 2.9%；p < 0.001）。三名患者的V90_CTVn_IMN降低超过9%。在平均肺剂量或平均心脏剂量方面未发现临床相关差异。
通过电影MV图像，我们发现实际的V90_CTVn_IMN显著低于计划值。在8%的患者中，V90_CTVn_IMN降低超过9%。
