Radiation Medicine Program, Princess Margaret Hospital, and Department of Radiation Oncology, University of Toronto, Toronto, Ontario, Canada.
Int J Radiat Oncol Biol Phys. 2012 Nov 15;84(4):e557-63. doi: 10.1016/j.ijrobp.2012.06.026. Epub 2012 Aug 25.
Understanding the relationship between normal tissue dose and delayed radiation toxicity is an important component of developing more effective radiation therapy. Late outcome data are generally available only for patients who have undergone 2-dimensional (2D) treatment plans. The purpose of this study was to evaluate the accuracy of 3D normal tissue dosimetry derived from reconstructed 2D treatment plans in Hodgkin's lymphoma (HL) patients.
Three-dimensional lung, heart, and breast volumes were reconstructed from 2D planning radiographs for HL patients who received mediastinal radiation therapy. For each organ, a reference 3D organ was modified with patient-specific structural information, using deformable image processing software. Radiation therapy plans were reconstructed by applying treatment parameters obtained from patient records to the reconstructed 3D volumes. For each reconstructed organ mean dose (Dmean) and volumes covered by at least 5 Gy (V5) and 20 Gy (V20) were calculated. This process was performed for 15 patients who had both 2D and 3D planning data available to compare the reconstructed normal tissue doses with those derived from the primary CT planning data and also for 10 historically treated patients with only 2D imaging available.
For patients with 3D planning data, the normal tissue doses could be reconstructed accurately using 2D planning data. Median differences in Dmean between reconstructed and actual plans were 0.18 Gy (lungs), -0.15 Gy (heart), and 0.30 Gy (breasts). Median difference in V5 and V20 were less than 2% for each organ. Reconstructed 3D dosimetry was substantially higher in historical mantle-field treatments than contemporary involved-field mediastinal treatments: average Dmean values were 15.2 Gy vs 10.6 Gy (lungs), 27.0 Gy vs 14.3 Gy (heart), and 8.0 Gy vs 3.2 Gy (breasts).
Three-dimensional reconstruction of absorbed dose to organs at risk can be estimated accurately many years after exposure by using limited 2D data. Compared to contemporary involved-field treatments, normal tissue doses were significantly higher in historical mantle-field treatments. These methods build capacity to quantify the relationship between 3D normal tissue dose and observed late effects.
了解正常组织剂量与迟发性放射毒性之间的关系是开发更有效的放射治疗方法的重要组成部分。只有接受二维（2D）治疗计划的患者才能获得晚期结果数据。本研究的目的是评估从 Hodgkin 淋巴瘤（HL）患者的二维治疗计划重建中得出的三维正常组织剂量的准确性。
对接受纵隔放射治疗的 HL 患者的二维计划射线照片进行三维肺、心脏和乳房体积重建。对于每个器官，使用变形图像处理软件，使用患者特定的结构信息修改参考三维器官。通过将从患者记录中获得的治疗参数应用于重建的 3D 体积，重建放射治疗计划。对于每个重建的器官，计算平均剂量（Dmean）和至少覆盖 5 Gy（V5）和 20 Gy（V20）的体积。对于有 2D 和 3D 计划数据的 15 名患者进行了此过程，以比较重建的正常组织剂量与从原始 CT 计划数据得出的剂量，并对仅有 2D 成像的 10 名历史上接受治疗的患者进行了比较。
对于有 3D 计划数据的患者，使用二维计划数据可以准确地重建正常组织剂量。重建计划与实际计划之间 Dmean 的中位数差异为 0.18 Gy（肺），-0.15 Gy（心脏）和 0.30 Gy（乳房）。每个器官的 V5 和 V20 的中位数差异小于 2％。历史上的斗篷野治疗与当代的受累野纵隔治疗相比，重建的 3D 剂量明显更高：平均 Dmean 值分别为 15.2 Gy 与 10.6 Gy（肺），27.0 Gy 与 14.3 Gy（心脏）和 8.0 Gy 与 3.2 Gy（乳房）。
通过使用有限的 2D 数据，可以在暴露多年后准确估计危及器官的吸收剂量的三维重建。与当代受累野治疗相比，历史上的斗篷野治疗的正常组织剂量明显更高。这些方法为量化 3D 正常组织剂量与观察到的迟发性效应之间的关系提供了能力。
