用 5D 肺部运动模型描述自由呼吸模式。
Characterization of free breathing patterns with 5D lung motion model.
机构信息
Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
出版信息
Med Phys. 2009 Nov;36(11):5183-9. doi: 10.1118/1.3246348.
PURPOSE
To determine the quiet respiration breathing motion model parameters for lung cancer and nonlung cancer patients.
METHODS
49 free breathing patient 4DCT image datasets (25 scans, cine mode) were collected with simultaneous quantitative spirometry. A cross-correlation registration technique was employed to track the lung tissue motion between scans. The registration results were applied to a lung motion model: X(-->) = X(-->)0 + alpha(-->)v + beta(-->)f, where X(-->) is the position of a piece of tissue located at reference position X(-->)0 during a reference breathing phase (zero tidal volume v, zero airflow f). alpha(-->) is a parameter that characterizes the motion due to air filling (motion as a function of tidal volume v) and beta(-->) is the parameter that accounts for the motion due to the imbalance of dynamical stress distributions during inspiration and exhalation that causes lung motion hysteresis (motion as a function of airflow f). The parameters alpha(-->) and beta(-->) together provide a quantitative characterization of breathing motion that inherently includes the complex hysteresis interplay. The alpha(-->) and beta(-->) distributions were examined for each patient to determine overall general patterns and interpatient pattern variations.
RESULTS
For 44 patients, the greatest values of /alpha(-->)/ were observed in the inferior and posterior lungs. For the rest of the patients, /alpha(-->)/ reached its maximum in the anterior lung in three patients and the lateral lung in two patients. The hysteresis motion beta(-->) had greater variability, but for the majority of patients, /beta(-->)/ was largest in the lateral lungs.
CONCLUSIONS
This is the first report of the three-dimensional breathing motion model parameters for a large cohort of patients. The model has the potential for noninvasively predicting lung motion. The majority of patients exhibited similar /alpha(-->)/ maps and the /beta(-->)/ maps showed greater interpatient variability. The motion parameter interpatient variability will inform our need for custom radiation therapy motion models. The utility of this model depends on the parameter stability over time, which is still under investigation.
目的
确定肺癌和非肺癌患者的安静呼吸运动模型参数。
方法
采集了 49 例自由呼吸患者的 4DCT 图像数据集（25 次扫描，电影模式），并同时进行定量肺活量测定。采用互相关配准技术对扫描间的肺组织运动进行跟踪。将配准结果应用于肺运动模型：X（-->) = X（-->)0 + alpha（-->)v + beta（-->)f，其中 X（-->)是位于参考位置 X（-->)0的组织块在参考呼吸相（零潮气量 v，零气流 f）中的位置。alpha（-->)是一个描述充气运动（作为潮气量 v 的函数的运动）的参数，beta（-->)是描述吸气和呼气期间动力分布失衡引起的肺运动滞后（作为气流 f 的函数的运动）的参数。alpha（-->)和 beta（-->)两个参数共同提供了对呼吸运动的定量描述，其中包括复杂的滞后相互作用。对每个患者的 alpha（-->)和 beta（-->)分布进行了检查，以确定总体一般模式和患者间的模式变化。
结果
对于 44 名患者，最大的/alpha（-->）/值出现在下后肺。对于其余患者，在 3 名患者中，前肺的/alpha（-->）/达到最大值，在 2 名患者中，侧肺的/alpha（-->）/达到最大值。滞后运动 beta（-->)具有更大的可变性，但对于大多数患者，/beta（-->）/在侧肺中最大。
结论
这是首次对大量患者的三维呼吸运动模型参数进行报道。该模型具有无创预测肺运动的潜力。大多数患者表现出相似的/alpha（-->）/图谱，/beta（-->）/图谱显示出更大的患者间变异性。患者间运动参数变异性将为我们对定制放射治疗运动模型的需求提供信息。该模型的实用性取决于参数随时间的稳定性，这仍在研究中。
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