A model of respiratory airway motion for real-time tracking of an ultrathin bronchoscope
A model of respiratory airway motion for real-time tracking of an ultrathin bronchoscope
复制标题
用于实时跟踪超细支气管镜的呼吸气道运动模型
DOI：
10.1117/12.710150
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
E. Seibel
中科院分区：
文献类型：
--
作者：
Timothy D. Soper;D. Haynor;R. Glenny;E. Seibel
在呼吸的不同阶段对受试者进行的胸部CT扫描的可变形配准提供了由于呼吸而在肺中发生的空间变化的直接测量。这种呼吸运动的研究是开发一种新的电磁跟踪超薄支气管镜的基于CT的引导系统的一部分。在从完全呼气到完全吸气的五种不同肺压下，对一只麻醉的猪进行了15次扫描。在多分辨率框架下，采用非刚性配准和高斯正则化方法，利用对称的“恶魔”力来计算变形场。对各种配准方案进行了测试，包括：输入图像的初始直方图匹配，正则化过程中的场平滑程度，以及应用一种自适应平滑方法，该方法根据图像梯度的大小来加权平滑核的元素。使用反向一致性度量和传递一致性度量对注册质量进行量化和比较。在优化算法参数后，通过将集合中的每一幅图像配准到基线图像来计算变形场。将满激励下的基线图像与满到期时的图像配准会产生最大变形。提出了两个假设：第一，每个变形都可以被模拟为最大变形的数学分倍数，第二，变形与呼吸压力成线性关系。图像配准测得的变形量与线性模型预测值的平均偏差为1.25 mm。在最大变形时，这种运动补偿使呼吸引起的定位误差减少了87%。
Deformable registration of chest CT scans taken of a subject at various phases of respiration provide a direct measure of the spatially varying displacements that occur in the lung due to breathing. This respiratory motion was studied as part of the development of a CT-based guidance system for a new electromagnetically tracked ultrathin bronchoscope. Fifteen scans of an anesthesized pig were acquired at five distinct lung pressures between full expiration to full inspiration. Deformation fields were computed by non-rigid registration using symmetric "demons" forces followed by Gaussian regularization in a multi-resolution framework. Variants of the registration scheme were tested including: initial histogram matching of input images, degree of field smoothing during regularization, and applying an adaptive smoothing method that weights elements of the smoothing kernel by the magnitude of the image gradient. Registration quality was quantified and compared using inverse and transitive consistency metrics. After optimizing the algorithm parameters, deformation fields were computed by registering each image in the set to a baseline image. Registration of the baseline image at full inspiration to an image at full expiration produced the maximum deformation. Two hypotheses were made: first, that each deformation could be modeled as a mathematical sub-multiple of the maximum deformation, and second, that the deformation scales linearly with respiratory pressure. The discrepancy between the deformation measured by image registration and that predicted by the linear model was 1.25 mm on average. At maximum deformation, this motion compensation constitutes an 87% reduction in respiration-induced localization error.