Department of Radiation Oncology, Hiroshima University, Graduate School of Biomedical Sciences, Hiroshima City, Japan.
Int J Radiat Oncol Biol Phys. 2012 Mar 15;82(4):e663-70. doi: 10.1016/j.ijrobp.2011.08.016. Epub 2012 Jan 13.
To investigate the incorporation of functional lung image-derived low attenuation area (LAA) based on four-dimensional computed tomography (4D-CT) into respiratory-gated intensity-modulated radiotherapy (IMRT) or volumetric modulated arc therapy (VMAT) in treatment planning for lung cancer patients with chronic obstructive pulmonary disease (COPD).
Eight lung cancer patients with COPD were the subjects of this study. LAA was generated from 4D-CT data sets according to CT values of less than than -860 Hounsfield units (HU) as a threshold. The functional lung image was defined as the area where LAA was excluded from the image of the total lung. Two respiratory-gated radiotherapy plans (70 Gy/35 fractions) were designed and compared in each patient as follows: Plan A was an anatomical IMRT or VMAT plan based on the total lung; Plan F was a functional IMRT or VMAT plan based on the functional lung. Dosimetric parameters (percentage of total lung volume irradiated with ≥20 Gy [V20], and mean dose of total lung [MLD]) of the two plans were compared.
V20 was lower in Plan F than in Plan A (mean 1.5%, p = 0.025 in IMRT, mean 1.6%, p = 0.044 in VMAT) achieved by a reduction in MLD (mean 0.23 Gy, p = 0.083 in IMRT, mean 0.5 Gy, p = 0.042 in VMAT). No differences were noted in target volume coverage and organ-at-risk doses.
Functional IGRT planning based on LAA in respiratory-guided IMRT or VMAT appears to be effective in preserving a functional lung in lung cancer patients with COPD.
研究将基于四维 CT（4D-CT）的功能肺低衰减区（LAA）纳入慢性阻塞性肺疾病（COPD）肺癌患者呼吸门控调强放疗（IMRT）或容积旋转调强放疗（VMAT）计划中的情况。
本研究纳入了 8 例 COPD 肺癌患者。根据低于-860 亨氏单位（HU）的 CT 值将 LAA 从 4D-CT 数据集生成。功能肺图像定义为排除 LAA 的全肺图像区域。每位患者设计并比较了两种呼吸门控放疗计划（70 Gy/35 次）：计划 A 为基于全肺的解剖学 IMRT 或 VMAT 计划；计划 F 为基于功能肺的功能 IMRT 或 VMAT 计划。比较了两种计划的剂量学参数（20 Gy 以上总肺体积照射百分比[V20]和总肺平均剂量[MLD]）。
与计划 A 相比，计划 F 中的 V20 较低（IMRT 时的平均值为 1.5%，p = 0.025；VMAT 时的平均值为 1.6%，p = 0.044），这是通过降低 MLD 实现的（IMRT 时的平均值为 0.23 Gy，p = 0.083；VMAT 时的平均值为 0.5 Gy，p = 0.042）。在靶区覆盖和危及器官剂量方面无差异。
基于 LAA 的功能 IGRT 计划在 COPD 肺癌患者的呼吸门控 IMRT 或 VMAT 中似乎可有效地保留功能性肺。
