Liverpool and Macarthur Cancer Therapy Centres, New South Wales, Australia; Ingham Institute of Applied Medical Research, New South Wales, Australia; South Western Clinical School, University of New South Wales, New South Wales, Australia.
Liverpool and Macarthur Cancer Therapy Centres, New South Wales, Australia; Ingham Institute of Applied Medical Research, New South Wales, Australia; South Western Clinical School, University of New South Wales, New South Wales, Australia; Centre for Medical Radiation Physics, University of Wollongong, New South Wales, Australia; Institute of Medical Physics, School of Physics, University of Sydney, New South Wales, Australia.
Pract Radiat Oncol. 2017 Jan-Feb;7(1):e9-e17. doi: 10.1016/j.prro.2016.06.009. Epub 2016 Jun 23.
The aim of this study was to estimate the delivered dose to the target and organs at risk (OAR) for external beam accelerated partial-breast irradiation (APBI) accounting for day-to-day setup uncertainties, using rigid and deformable image registration.
One planning computed tomography (CT) scan and 5 cone beam CT scans for each of 25 patients previously treated with tangential breast radiation therapy were used. All cone beam CT scans were registered to the planning CT scan using 3 techniques: (1) rigid registration based on bony anatomy only, (2) rigid registration based on soft-tissue only, and (3) deformable image registration. For each patient, 4 dose distributions were calculated for APBI. The first dose distribution was the original plan. The other 3 were "dose-of-the-day" for each of the registration approaches. The effects of image registrations on estimating delivered dose to targets and OAR were determined.
The average reductions in V (percentage of the PTV that received 95% of the prescribed dose) were 6%, 7%, and 5% for bone, soft-tissue, and deformable registrations, respectively. The average increase in mean dose to the heart were 9%, 9%, and 18% for bone, soft-tissue, and deformable registrations, respectively, whereas the average increase in maximum dose to the contralateral breast were 19%, 20%, and 28%, respectively.
The results of this study have shown that there are differences between the planned and estimated delivered dose for APBI because of day-to-day setup uncertainties that may need to be accounted for. Estimated dosimetric impact of setup variation and breast deformation assessed using deformable registration was greater for OARs and smaller for target volumes compared to rigid registration.
本研究旨在通过刚性和弹性图像配准，估算考虑日常摆位不确定性的外照射加速部分乳房照射（APBI）的靶区和危及器官（OAR）的剂量。
对 25 例接受过切线乳房放射治疗的患者，分别使用 1 次计划 CT 扫描和 5 次锥形束 CT 扫描。所有锥形束 CT 扫描均使用 3 种技术与计划 CT 扫描配准：（1）仅基于骨性解剖的刚性配准，（2）仅基于软组织的刚性配准，（3）弹性图像配准。对于每位患者，计算了 4 种 APBI 的剂量分布。第一种剂量分布是原始计划，另外 3 种是针对每种配准方法的“当日剂量”。确定图像配准对估计靶区和 OAR 接受剂量的影响。
骨性、软组织和弹性配准的平均靶区体积 V（接受处方剂量 95%的靶区百分比）降低率分别为 6%、7%和 5%。心脏的平均剂量增加率分别为 9%、9%和 18%，对侧乳房的最大剂量增加率分别为 19%、20%和 28%。
本研究结果表明，由于日常摆位不确定性，APBI 的计划和估计剂量之间存在差异，这可能需要考虑。与刚性配准相比，使用弹性配准评估的摆位变化和乳房变形对 OAR 的剂量学影响估计更大，对靶区体积的影响更小。
