Department of Radiation Oncology, University of California Los Angeles, Westwood, California 90095, USA.
Med Phys. 2013 Jun;40(6):063502. doi: 10.1118/1.4805099.
The purpose of this study was to develop a methodology to quantitatively measure the thorax-to-abdomen breathing ratio from a 4DCT dataset for breathing motion modeling and breathing motion studies.
The thorax-to-abdomen breathing ratio was quantified by measuring the rate of cross-sectional volume increase throughout the thorax and abdomen as a function of tidal volume. Twenty-six 16-slice 4DCT patient datasets were acquired during quiet respiration using a protocol that acquired 25 ciné scans at each couch position. Fifteen datasets included data from the neck through the pelvis. Tidal volume, measured using a spirometer and abdominal pneumatic bellows, was used as breathing-cycle surrogates. The cross-sectional volume encompassed by the skin contour when compared for each CT slice against the tidal volume exhibited a nearly linear relationship. A robust iteratively reweighted least squares regression analysis was used to determine η(i), defined as the amount of cross-sectional volume expansion at each slice i per unit tidal volume. The sum Ση(i) throughout all slices was predicted to be the ratio of the geometric expansion of the lung and the tidal volume; 1.11. The Xiphoid process was selected as the boundary between the thorax and abdomen. The Xiphoid process slice was identified in a scan acquired at mid-inhalation. The imaging protocol had not originally been designed for purposes of measuring the thorax-to-abdomen breathing ratio so the scans did not extend to the anatomy with η(i) = 0. Extrapolation of η(i)-η(i) = 0 was used to include the entire breathing volume. The thorax and abdomen regions were individually analyzed to determine the thorax-to-abdomen breathing ratios. There were 11 image datasets that had been scanned only through the thorax. For these cases, the abdomen breathing component was equal to 1.11 - Ση(i) where the sum was taken throughout the thorax.
The average Ση(i) for thorax and abdomen image datasets was found to be 1.20 ± 0.17, close to the expected value of 1.11. The thorax-to-abdomen breathing ratio was 0.32 ± 0.24. The average Ση(i) was 0.26 ± 0.14 in the thorax and 0.93 ± 0.22 in the abdomen. In the scan datasets that encompassed only the thorax, the average Ση(i) was 0.21 ± 0.11.
A method to quantify the relationship between abdomen and thoracic breathing was developed and characterized.
本研究旨在开发一种从 4DCT 数据集定量测量胸廓-腹部呼吸比的方法，用于呼吸运动建模和呼吸运动研究。
通过测量胸廓和腹部的横截面积随潮气量的变化率来量化胸廓-腹部呼吸比。使用协议在安静呼吸期间采集了 26 个 16 层 4DCT 患者数据集，该协议在每个床单位位置采集 25 个电影扫描。15 个数据集包括从颈部到骨盆的数据。使用肺活量计和腹部气动波纹管测量潮气量，作为呼吸周期替代物。当将每个 CT 切片的皮肤轮廓与潮气量进行比较时，横截面体积表现出近乎线性的关系。使用稳健迭代重加权最小二乘回归分析来确定 η(i)，定义为每个切片 i 中单位潮气量的横截面积扩张量。所有切片的总和 Ση(i)预计为肺和潮气量的几何扩张比；1.11。剑突过程被选为胸廓和腹部之间的边界。在吸气中期采集的扫描中识别剑突过程切片。成像协议最初并非为测量胸廓-腹部呼吸比而设计，因此扫描并未扩展到 η(i) = 0 的解剖结构。使用 η(i) - η(i) = 0 的外推来包括整个呼吸体积。单独分析胸廓和腹部区域以确定胸廓-腹部呼吸比。有 11 个图像数据集仅扫描到胸廓。对于这些情况，腹部呼吸分量等于 1.11 - Ση(i)，其中和是在整个胸廓中取的。
发现胸廓和腹部图像数据集的平均 Ση(i)为 1.20 ± 0.17，接近预期值 1.11。胸廓-腹部呼吸比为 0.32 ± 0.24。胸廓的平均 Ση(i)为 0.26 ± 0.14，腹部为 0.93 ± 0.22。仅包含胸廓的扫描数据集的平均 Ση(i)为 0.21 ± 0.11。
开发并描述了一种量化腹部和胸部呼吸之间关系的方法。
