IEEE Trans Biomed Eng. 2022 Apr;69(4):1424-1434. doi: 10.1109/TBME.2021.3118535. Epub 2022 Mar 18.
Determination of end-expiration (EE) and end-inspiration (EI) time points in the respiratory cycle in free-breathing slice image acquisitions of the thorax is one key step needed for 4D image construction via dynamic magnetic resonance imaging. The purpose of this paper is to realize the automation of the labeling process.
The diaphragm is used as a surrogate for tracking respiratory motion and determining the state of breathing. Regions of interest (ROIs) containing the hemi-diaphragms are set by human interaction to compute the optical flow matrix between two adjacent 2D time slices. Subsequently, our approach examines the diaphragm speed and direction and by considering the change in the optical flow matrix, the EE or EI points are detected.
The labeling accuracy for the lateral aspect of the left lung and the lateral aspect of the right lung (0.63±0.71) is significantly lower (P < 0.05) than the accuracy for other positions (0.42±0.44), but the error in almost all scenarios is less than 1 time point. By comparing between automatic and manual labeling in 12 scenarios, we found out that 9 scenarios showed no significant difference (P > 0.05) between two methods. Overall, our method is found to be highly agreeable with manual labeling and greatly shortens the labeling time, requiring less than 8 minutes/ study compared to 4 hours/ study for manual labeling.
Our method achieves automatic labeling of EE and EI points without the need for use of patientinternal or external markers.
在自由呼吸切片图像采集的胸部，确定呼吸周期的呼气末（EE）和吸气末（EI）时间点是通过动态磁共振成像构建 4D 图像的关键步骤之一。本文的目的是实现标签过程的自动化。
膈膜被用作跟踪呼吸运动和确定呼吸状态的替代物。通过人机交互设置包含半膈膜的感兴趣区域（ROI），以计算两个相邻 2D 时间片之间的光流矩阵。然后，我们的方法检查膈膜的速度和方向，并通过考虑光流矩阵的变化，检测 EE 或 EI 点。
左侧肺外侧和右侧肺外侧的标记准确性（0.63±0.71）明显低于其他位置（0.42±0.44）（P < 0.05），但几乎所有情况下的误差都小于 1 个时间点。通过在 12 个场景中比较自动和手动标记，我们发现 9 个场景两种方法之间没有显著差异（P > 0.05）。总体而言，我们的方法被发现与手动标记高度一致，并大大缩短了标记时间，与手动标记相比，每个研究需要不到 8 分钟，而手动标记则需要 4 小时。
我们的方法实现了无需使用患者内部或外部标记的 EE 和 EI 点的自动标记。
