School of Physics, University of Sydney, NSW 2006, Australia. e.kyriakou@ physics.usyd.edu.au
Phys Med Biol. 2012 Feb 21;57(4):919-35. doi: 10.1088/0031-9155/57/4/919. Epub 2012 Jan 31.
Evidence that some lung tumors change shape during respiration is derived from respiratory gated CT data by statistical shape modeling and image manipulation. Some tumors behave as rigid objects while others show systematic shape changes. Two views of lung motion are presented to allow analysis of the results. In the first, lung motion is viewed as a wave motion in which inertial effects arising from mass are present and in the second it is a quasistatic motion in which the mass of the lung tissues is neglected. In the first scenario, the extremes of tumor compression and expansion are expected to correlate with maximum upward and downward velocity of the tumor, respectively. In the second, they should occur at end exhale and end inhale, respectively. An observed correlation between tumor strain and tumor velocity provides more support for the first view of lung motion and may explain why previous attempts at observing tumor shape changes during respiration have largely failed. The implications for the optimum gating of radiation therapy are discussed.
一些肿瘤在呼吸过程中改变形状的证据是通过统计形状建模和图像操作从呼吸门控 CT 数据中得出的。有些肿瘤表现为刚体，而有些则表现出系统的形状变化。本文呈现了两种肺运动视图，以允许对结果进行分析。在第一种情况下，肺运动被视为存在惯性效应的波动运动，而在第二种情况下，它是一种忽略肺组织质量的准静态运动。在前一种情况下，肿瘤的压缩和扩张极限预计分别与肿瘤的最大向上和向下速度相关。在后一种情况下，它们应该分别发生在呼气末和吸气末。观察到的肿瘤应变与肿瘤速度之间的相关性为第一种肺运动观点提供了更多支持，这可能解释了为什么以前观察呼吸过程中肿瘤形状变化的尝试大多失败的原因。还讨论了对放射治疗最佳门控的影响。
