Use of weekly 4DCT-based ventilation maps to quantify changes in lung function for patients undergoing radiation therapy
Use of weekly 4DCT-based ventilation maps to quantify changes in lung function for patients undergoing radiation therapy
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DOI：
10.1118/1.3668056
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发表时间：
2012-01-01
期刊：
影响因子：
3.8
通讯作者：
Guerrero, Thomas
中科院分区：
文献类型：
--
作者：
Vinogradskiy, Yevgeniy Y.;Castillo, Richard;Guerrero, Thomas
目的：提出一种从四维CT(4DCT)图像计算通气图的方法。在肺癌患者的放射治疗过程中，每周采集4DCT数据。我们的工作目的是利用每周4DCT数据计算的通气图来研究放射治疗期间通气量的变化。方法：为6名患者生成表示通气量的定量图。可变形配准用于连接4DCT数据集的吸气和呼气相之间的相应肺体积元素。在空间配准之后，相应的Hounsfield单元被输入到基于密度变化的模型中，用于量化局部通气量。将所有周的通气量数据记录到治疗前的通气量图像集中。我们根据剂量(V-20)和肺叶定义感兴趣区(ROI)，并跟踪每个ROI在整个治疗过程中的每周通气量，从而对数据进行了定量分析。使用与每周通气量数据线性拟合的斜率来评估整个治疗过程中通气量的变化。正斜率表示通风增加，负斜率表示通风减少，斜率为0表示没有变化。使用剂量ROI通气量和斜率数据来研究整个治疗过程中通气量随剂量变化的情况。利用肺叶ROI通气量数据研究肿瘤的存在对治疗前通气量的影响。结果：使用剂量ROI数据，我们发现3名患者每周的通气量随剂量的增加而增加(斜率分别为1.1、1.4和1.5)，3名患者的通气量无变化或略有下降(斜率为0.3、-0.6、-0.5)。从视觉上看，在含有肿瘤的肺叶中，治疗前的通气量似乎较低。治疗前含肿瘤肺叶通气率为39%，不含肿瘤肺叶通气率为54%。两组通气量差异有统计学意义(p=0.017)。当对每周肺叶通气量数据进行定性观察时，出现了两种截然不同的模式。当叶内肿瘤体积缩小时，叶内通气量增加。肿瘤体积不缩小时，通气量分布无明显变化。包含缩小的肿瘤的肝叶组的平均斜率为1.18，而不包含肿瘤(或包含不缩小的肿瘤)的组的平均斜率为-0.32。两组的斜率有显著差异(p=0.014)。结论：我们没有发现通气量随辐射剂量变化的一致模式。对于含有肿瘤的肺叶，由于中央气道闭塞，治疗前通气量显著降低。每周的肺叶通气量数据显示，当肿瘤体积缩小时，通气量增加，而当胸部解剖结构没有明显变化时，通气量可能保持不变。(C)2012年美国医学物理学家协会。[DOI：10.1118/1.3668056]
Purpose: A method has been proposed to calculate ventilation maps from four-dimensional computed tomography (4DCT) images. Weekly 4DCT data were acquired throughout the course of radiation therapy for patients with lung cancer. The purpose of our work was to use ventilation maps calculated from weekly 4DCT data to study how ventilation changed throughout radiation therapy.Methods: Quantitative maps representing ventilation were generated for six patients. Deformable registration was used to link corresponding lung volume elements between the inhale and exhale phases of the 4DCT dataset. Following spatial registration, corresponding Hounsfield units were input into a density-change-based model for quantifying the local ventilation. The ventilation data for all weeks were registered to the pretreatment ventilation image set. We quantitatively analyzed the data by defining regions of interest (ROIs) according to dose (V-20) and lung lobe and by tracking the weekly ventilation of each ROI throughout treatment. The slope of the linear fit to the weekly ventilation data was used to evaluate the change in ventilation throughout treatment. A positive slope indicated an increase in ventilation, a negative slope indicated a decrease in ventilation, and a slope of 0 indicated no change. The dose ROI ventilation and slope data were used to study how ventilation changed throughout treatment as a function of dose. The lung lobe ROI ventilation data were used to study the impact of the presence of tumor on pretreatment ventilation. In addition, the lobe ROI data were used to study the impact of tumor reduction on ventilation change throughout treatment.Results: Using the dose ROI data, we found that three patients had an increase in weekly ventilation as a function of dose (slopes of 1.1, 1.4, and 1.5) and three patients had no change or a slight decrease in ventilation as a function of dose (slopes of 0.3, -0.6, -0.5). Visually, pretreatment ventilation appeared to be lower in the lobes that contained tumor. Pretreatment ventilation was 39% for lobes that contained tumor and 54% for lobes that did not contain tumor. The difference in ventilation between the two groups was statistically significant (p = 0.017). When the weekly lobe ventilation data were qualitatively observed, two distinct patterns emerged. When the tumor volume in a lobe was reduced, ventilation increased in the lobe. When the tumor volume was not reduced, the ventilation distribution did not change. The average slope of the group of lobes that contained tumors that shrank was 1.18, while the average slope of the group that did not contain tumors (or contained tumors that did not shrink) was -0.32. The slopes for the two groups were significantly different (p = 0.014).Conclusions: We did not find a consistent pattern of ventilation change as a function of radiation dose. Pretreatment ventilation was significantly lower for lobes that contained tumor, due to occlusion of the central airway. The weekly lobe ventilation data indicated that when tumor volume shrinks, ventilation increases, and when the thoracic anatomy is not visibly changed, ventilation is likely to remain unchanged. (C) 2012 American Association of Physicists in Medicine. [DOI: 10.1118/1.3668056]