Department of Radiation Oncology, University of California Davis, Sacramento, California.
Department of Digital Imaging, Philips Research, Hamburg, Germany.
Int J Radiat Oncol Biol Phys. 2018 Nov 15;102(4):1366-1373. doi: 10.1016/j.ijrobp.2018.04.063. Epub 2018 May 4.
Lung functional image guided radiation therapy (RT) that avoids irradiating highly functional regions has potential to reduce pulmonary toxicity following RT. Tumor regression during RT is common, leading to recovery of lung function. We hypothesized that computed tomography (CT) ventilation image-guided treatment planning reduces the functional lung dose compared to standard anatomic image-guided planning in 2 different scenarios with or without plan adaptation.
CT scans were acquired before RT and during RT at 2 time points (16-20 Gy and 30-34 Gy) for 14 patients with locally advanced lung cancer. Ventilation images were calculated by deformable image registration of four-dimensional CT image data sets and image analysis. We created 4 treatment plans at each time point for each patient: functional adapted, anatomic adapted, functional unadapted, and anatomic unadapted plans. Adaptation was performed at 2 time points. Deformable image registration was used for accumulating dose and calculating a composite of dose-weighted ventilation used to quantify the lung accumulated dose-function metrics. The functional plans were compared with the anatomic plans for each scenario separately to investigate the hypothesis at a significance level of 0.05.
Tumor volume was significantly reduced by 20% after 16 to 20 Gy (P = .02) and by 32% after 30 to 34 Gy (P < .01) on average. In both scenarios, the lung accumulated dose-function metrics were significantly lower in the functional plans than in the anatomic plans without compromising target volume coverage and adherence to constraints to critical structures. For example, functional planning significantly reduced the functional mean lung dose by 5.0% (P < .01) compared to anatomic planning in the adapted scenario and by 3.6% (P = .03) in the unadapted scenario.
This study demonstrated significant reductions in the accumulated dose to the functional lung with CT ventilation image-guided planning compared to anatomic image-guided planning for patients showing tumor regression and changes in regional ventilation during RT.
肺功能图像引导的放射治疗（RT）避免照射高功能区域，有可能降低 RT 后肺毒性。RT 期间肿瘤消退是常见的，导致肺功能恢复。我们假设与标准解剖图像引导计划相比，在存在或不存在计划调整的 2 种情况下，使用 CT 通气图像引导治疗计划可降低功能肺剂量。
14 例局部晚期肺癌患者在 RT 前和 RT 期间进行了 2 次 CT 扫描（16-20Gy 和 30-34Gy）。通过对 4 个四维 CT 数据集的图像进行变形图像配准和图像分析来计算通气图像。我们为每个患者在每个时间点创建了 4 个治疗计划：功能适应、解剖适应、功能不适应和解剖不适应计划。在 2 个时间点进行了调整。使用变形图像配准来累积剂量，并计算用于量化肺累积剂量-功能指标的剂量加权通气的综合值。分别对 2 种情况下的功能计划与解剖计划进行比较，以在 0.05 的显著性水平上验证假设。
肿瘤体积在 16 至 20Gy 后平均减少了 20%（P=0.02），在 30 至 34Gy 后减少了 32%（P<0.01）。在这两种情况下，与解剖计划相比，功能计划的肺累积剂量-功能指标明显更低，同时不影响靶区覆盖率和对关键结构的限制的遵守。例如，在适应方案中，功能规划显著降低了功能平均肺剂量 5.0%（P<0.01），在非适应方案中降低了 3.6%（P=0.03）。
这项研究表明，与解剖图像引导计划相比，CT 通气图像引导计划在显示肿瘤消退和 RT 期间区域性通气变化的患者中，可显著降低功能肺的累积剂量。
