Doi Yoshiko, Kimura Tomoki, Nakashima Takeo, Takeuchi Yuki, Takahashi Ippei, Nishibuchi Ikuno, Murakami Yuji, Nagata Yasushi
Department of Radiation Oncology, Hiroshima University Hospital, Hiroshima City, Japan.
Division of Radiation Oncology, Hiroshima University Hospital, Hiroshima City, Japan.
Adv Radiat Oncol. 2017 Feb 2;2(2):183-191. doi: 10.1016/j.adro.2017.01.011. eCollection 2017 Apr-Jun.
To investigate the incorporation of functional lung image-derived low-attenuation area (LAA) based on 4-dimensional computed tomography (4D-CT) in volumetric modulated arc therapy (VMAT) planning for patients with malignant pleural mesothelioma (MPM) after extrapleural pneumonectomy.
Twelve patients with MPM after extrapleural pneumonectomy were included. The primarily affected side was the right in 6 patients and the left in 6 patients. LAA was generated from 4D-CT data according to CT values with a threshold of less than -860 Hounsfield units (HU). Functional lung image was defined as the area where LAA was excluded from contralateral lung image. Two radiation therapy plans were designed: (1) Plan C, conventional VMAT and (2) Plan F, functional VMAT plan based on the functional lung. Both plans were compared in each patient with respect to the following dosimetric parameters: fV20, V20, fV10, V10, fV5, and V5, the percentages of functional or contralateral lung volumes irradiated with >20 Gy, 10 Gy, or 5 Gy, respectively; functional mean lung dose (fMLD) and mean lung dose (MLD), the mean dose to the functional or contralateral lung, respectively; maximum dose to the cord; mean doses to the liver and heart; and planning target volume homogeneity index.
fV5 and MLD were significantly lower in Plan F (fV5, median 57.5% in Plan C vs 38.5% in Plan F, < .01; MLD, median 7.0 Gy in Plan C vs 6.4 Gy in Plan F, = .04). fV10, V5, and fMLD were also significantly lower in Plan F. Compared with Plan C, planning target volume homogeneity index and liver, heart, and cord doses were not significantly elevated in Plan F.
Significant reductions in fV5, fV10, fMLD, V5, and MLD were achieved with the functional image guided VMAT plan without negative effects on other factors. LAA-based functional image guided radiation therapy planning in VMAT is a feasible method to spare the functional lung in patients with MPM.
探讨基于四维计算机断层扫描（4D-CT）的功能性肺图像衍生的低衰减区（LAA）在胸膜外全肺切除术后恶性胸膜间皮瘤（MPM）患者容积调强弧形放疗（VMAT）计划中的应用。
纳入12例胸膜外全肺切除术后的MPM患者。主要患侧为右侧6例，左侧6例。根据CT值从4D-CT数据生成LAA，阈值设定为小于-860亨氏单位（HU）。功能性肺图像定义为从对侧肺图像中排除LAA的区域。设计了两个放射治疗计划：（1）计划C，传统VMAT；（2）计划F，基于功能性肺的功能性VMAT计划。比较每个患者两个计划的以下剂量学参数：fV20、V20、fV10、V10、fV5和V5，分别为接受大于20 Gy、10 Gy或5 Gy照射的功能性或对侧肺体积的百分比；功能性平均肺剂量（fMLD）和平均肺剂量（MLD），分别为功能性或对侧肺的平均剂量；脊髓的最大剂量；肝脏和心脏的平均剂量；以及计划靶体积均匀性指数。
计划F中的fV5和MLD显著更低（fV5，计划C中位数为57.5%，计划F为38.5%，P<0.01；MLD，计划C中位数为7.0 Gy，计划F为6.4 Gy，P = 0.04）。计划F中的fV10、V5和fMLD也显著更低。与计划C相比，计划F中的计划靶体积均匀性指数以及肝脏、心脏和脊髓剂量没有显著升高。
功能性图像引导的VMAT计划显著降低了fV5、fV10、fMLD、V5和MLD，且对其他因素没有负面影响。VMAT中基于LAA的功能性图像引导放射治疗计划是一种在MPM患者中保护功能性肺的可行方法。
