Centre for Medical Radiation Physics, Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong, NSW, Australia; Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW, Australia; Ingham Institute for Applied Medical Research, Liverpool Hospital, Sydney, NSW, Australia.
Centre for Medical Radiation Physics, Faculty of Engineering and Information Sciences, University of Wollongong, Wollongong, NSW, Australia; Liverpool and Macarthur Cancer Therapy Centres, Liverpool, NSW, Australia; Ingham Institute for Applied Medical Research, Liverpool Hospital, Sydney, NSW, Australia; Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW, Australia.
Pract Radiat Oncol. 2018 May-Jun;8(3):e87-e97. doi: 10.1016/j.prro.2017.07.007. Epub 2017 Jul 14.
The purpose of this study was to evaluate the impact of magnetic resonance imaging (MRI) versus computed tomography (CT)-derived planning target volumes (PTVs), in both supine and prone positions, for whole breast (WB) radiation therapy.
Four WB radiation therapy plans were generated for 28 patients in which PTVs were generated based on CT or MRI data alone in both supine and prone positions. A 6-MV tangential intensity modulated radiation therapy technique was used, with plans designated as ideal, acceptable, or noncompliant. Dose metrics for PTVs and organs at risk were compared to analyze any differences based on imaging modality (CT vs MRI) or patient position (supine vs prone).
With respect to imaging modality 2/11 whole breast planning target volume (WB_PTV) dose metrics (percentage of PTV receiving 90% and 110% of prescribed dose) displayed statistically significant differences; however, these differences did not alter the average plan compliance rank. With respect to patient positioning, the odds of having an ideal plan versus a noncompliant plan were higher for the supine position compared with the prone position (P = .026). The minimum distance between the seroma cavity planning target volume (SC_PTV) and the chest wall was increased with prone positioning (P < .001, supine and prone values 1.1 mm and 8.7 mm, respectively). Heart volume was greater in the supine position (P = .005). Heart doses were lower in the supine position than prone (P < .01, mean doses 3.4 ± 1.55 Gy vs 4.4 ± 1.13 Gy for supine vs prone, respectively). Mean lung doses met ideal dose constraints in both positions, but were best spared in the prone position. The contralateral breast maximum dose to 1cc (D1cc) showed significantly lower doses in the supine position (P < .001, 4.64 Gy vs 9.51 Gy).
Planning with PTVs generated from MRI data showed no clinically significant differences from planning with PTVs generated from CT with respect to PTV and doses to organs at risk. Prone positioning within this study reduced mean lung dose and whole heart volumes but increased mean heart and contralateral breast doses compared with supine.
本研究旨在评估磁共振成像（MRI）与计算机断层扫描（CT）在仰卧位和俯卧位下分别为全乳放疗生成的计划靶区（PTV）的影响。
对 28 名患者的 4 个全乳放疗计划进行了生成，其中仰卧位和俯卧位下的 PTV 均基于 CT 或 MRI 数据生成。采用 6MV 切线强度调制放疗技术，将计划指定为理想、可接受或不符合要求。比较了 PTV 和危及器官的剂量学指标，以分析基于成像方式（CT 与 MRI）或患者体位（仰卧位与俯卧位）的任何差异。
就成像方式而言，2/11 个全乳计划靶区（WB_PTV）剂量学指标（PTV 接受 90%和 110%处方剂量的百分比）显示出统计学上的显著差异；然而，这些差异并没有改变平均计划符合度等级。就患者体位而言，与俯卧位相比，仰卧位有更高的理想计划与非符合计划的几率（P=0.026）。与俯卧位相比，俯卧位时胸壁规划靶区（SC_PTV）与胸壁之间的最小距离增加（P＜0.001，仰卧位和俯卧位值分别为 1.1mm 和 8.7mm）。心脏体积在仰卧位时更大（P=0.005）。与俯卧位相比，心脏剂量在仰卧位时更低（P＜0.01，仰卧位和俯卧位的平均剂量分别为 3.4±1.55Gy 和 4.4±1.13Gy）。在两个体位下，平均肺剂量均符合理想剂量限制，但在俯卧位下得到了最好的保护。对侧乳房 1cc（D1cc）的最大剂量在仰卧位时显著降低（P＜0.001，4.64Gy 与 9.51Gy）。
与基于 CT 生成的 PTV 相比，基于 MRI 数据生成的 PTV 在 PTV 和危及器官剂量方面没有明显的临床差异。与仰卧位相比，本研究中的俯卧位降低了平均肺剂量和全心脏体积，但增加了平均心脏和对侧乳房剂量。
