Hybrid electromagnetic and image-based tracking of endoscopes with guaranteed smooth output
Hybrid electromagnetic and image-based tracking of endoscopes with guaranteed smooth output
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DOI：
10.1007/s11548-013-0835-5
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发表时间：
2013-11-01
影响因子：
3
通讯作者：
Navab, Nassir
中科院分区：
文献类型：
--
作者：
Reichl, Tobias;Luo, Xiongbiao;Navab, Nassir
柔性纤维支气管镜检查是一种广泛用于诊断和治疗肺部疾病的医疗程序。需要导航系统来跟踪支气管树内的柔性内窥镜。电磁（EM）跟踪是目前临床上用于此目的的唯一技术。由于呼吸运动，EM 跟踪和患者解剖结构之间的配准可能会变得不准确，因此提出了添加基于图像的跟踪作为基于 EM-图像的混合系统。当使用 EM 跟踪作为图像配准的初始化时，初始化中的微小变化可能会导致不同的局部最小值，并且混合跟踪会放大噪声。跟踪输出被建模为连续的，并使用样条曲线进行插值，从而大大提高了平滑度。使用用于位置的 Catmull-Rom 样条和用于定向的球面线性插值 (SLERP) 来插值相对于计算机断层扫描数据的支气管镜姿态。使用专家手动选择的地面真实姿态来评估混合方法，其中平均专家间一致性确定为 1.26 mm。使用四个动态体模数据集，精度为4.91毫米，与之前的方法相当。与最先进的方法相比，帧间平滑度从 2.77-3.72 毫米提高到 1.24 毫米。混合图像和电磁内窥镜引导提供了更真实、物理上合理的解决方案，并且抖动显着减少。这一定量结果通过真实视频和虚拟视频的视觉比较得到了证实，其中虚拟视频输出更加一致和鲁棒，与以前的方法相比，跟踪丢失或意外移动的情况更少。
Flexible fiber-optic bronchoscopy is a widespread medical procedure for the diagnosis and treatment of lung diseases. Navigation systems are needed to track the flexible endoscope within the bronchial tree. Electromagnetic (EM) tracking is currently the only technology used clinically for this purpose. The registration between EM tracking and patient anatomy may become inaccurate due to breathing motion, so the addition of image-based tracking has been proposed as a hybrid EM-image-based system.When EM tracking is used as an initialization for image registration, small changes in the initialization may lead to different local minima and noise is amplified by hybrid tracking. The tracking output is modeled as continuous and uses splines for interpolation, thus smoothness is greatly improved. The bronchoscope pose relative to computed tomography data is interpolated using Catmull-Rom splines for position and spherical linear interpolation (SLERP) for orientation.The hybrid method was evaluated using ground truth poses manually selected by experts, where mean inter-expert agreement was determined as 1.26 mm. Using four dynamic phantom data sets, the accuracy was 4.91 mm, which is equivalent to previous methods. Compared to state-of-art methods, inter-frame smoothness was improved from 2.77-3.72 to 1.24 mm.Hybrid image and electromagnetic endoscope guidance provides a more realistic and physically plausible solution with significantly less jitter. This quantitative result is confirmed by visual comparison of real and virtual video, where the virtual video output is much more consistent and robust, with fewer occasions of tracking loss or unexpected movement compared with previous methods.