Department of Radiation Oncology, University Hospital, Geneva, Switzerland.
Radiat Oncol. 2011 Jun 24;6:78. doi: 10.1186/1748-717X-6-78.
Physiological respiratory motion of tumors growing in the lung can be corrected with respiratory gating when treated with radiotherapy (RT). The optimal respiratory phase for beam-on may be assessed with a respiratory phase optimizer (RPO), a 4D image processing software developed with this purpose.
Fourteen patients with lung cancer were included in the study. Every patient underwent a 4D-CT providing ten datasets of ten phases of the respiratory cycle (0-100% of the cycle). We defined two morphological parameters for comparison of 4D-CT images in different respiratory phases: tumor-volume to lung-volume ratio and tumor-to-spinal cord distance. The RPO automatized the calculations (200 per patient) of these parameters for each phase of the respiratory cycle allowing to determine the optimal interval for RT.
Lower lobe lung tumors not attached to the diaphragm presented with the largest motion with breathing. Maximum inspiration was considered the optimal phase for treatment in 4 patients (28.6%). In 7 patients (50%), however, the RPO showed a most favorable volumetric and spatial configuration in phases other than maximum inspiration. In 2 cases (14.4%) the RPO showed no benefit from gating. This tool was not conclusive in only one case.
The RPO software presented in this study can help to determine the optimal respiratory phase for gated RT based on a few simple morphological parameters. Easy to apply in daily routine, it may be a useful tool for selecting patients who might benefit from breathing adapted RT.
在接受放射治疗（RT）时，通过呼吸门控可以纠正肺部生长的肿瘤的生理呼吸运动。可以使用呼吸相位优化器（RPO）来评估最佳的射束开启相位，RPO 是为实现这一目的而开发的 4D 图像处理软件。
本研究纳入了 14 例肺癌患者。每位患者均接受了 4D-CT 检查，共提供了 10 个呼吸周期十个时相（0-100%）的数据集。我们定义了两个形态学参数来比较不同呼吸时相的 4D-CT 图像：肿瘤体积与肺体积比和肿瘤与脊髓距离。RPO 自动计算（每位患者 200 次）这些参数在呼吸周期的每个时相的计算值，从而确定 RT 的最佳间隔。
不附着于膈肌的下叶肺部肿瘤在呼吸时运动幅度最大。4 名患者（28.6%）认为最大吸气时相是治疗的最佳阶段。然而，在 7 名患者（50%）中，RPO 显示在最大吸气以外的时相具有更好的体积和空间配置。在 2 例患者（14.4%）中，门控没有带来益处。在仅 1 例患者中，该工具的结论不明确。
本研究中介绍的 RPO 软件可以帮助基于几个简单的形态学参数确定 gated RT 的最佳呼吸相位。该软件易于在日常工作中应用，可能是选择可能受益于呼吸适应 RT 的患者的有用工具。
