Fast calibration of electromagnetically tracked oblique-viewing rigid endoscopes.
Fast calibration of electromagnetically tracked oblique-viewing rigid endoscopes.
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DOI：
10.1007/s11548-017-1623-4
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发表时间：
2017-10
影响因子：
3
通讯作者：
中科院分区：
文献类型：
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斜视（即角度）刚性内窥镜是常规内窥镜手术中常用的工具。它的两个可移动部件，望远镜和相机头之间的相对旋转，在相机图像中的物体的实际和投影之间产生旋转偏移。需要一种专门的校准方法来补偿这种偏移。我们开发了一种适合临床使用的斜视刚性内窥镜的快速校准方法。与先前基于光学跟踪的方法相比，我们使用电磁跟踪作为外部跟踪硬件，以提高紧凑性和实用性。在望远镜和摄像头上分别安装了两个电磁传感器，以减小电磁跟踪误差。该方法将单图像校准纳入其中，并开发了一种可灭菌的板，激光标记有校准图案。在此基础上，提出了一种估计相机图像旋转中心的通用算法。还开发了按顺时针和逆时针旋转更新相机矩阵的公式。采用传统的30°5 mm腹腔镜对所提出的校准方法进行了验证。采用该方法进行徒手标定，标定时间平均为2 min 8 s。校准精度在模拟的临床环境中进行评估，其中有几种手术工具存在于EM跟踪的磁场中。在旋转角度为- 40.3°至174.7°范围内，均方根重投影误差平均为4.9像素（范围为2.4 - 8.5像素，图像分辨率为1280 × 720）。该方法也被设计为在手术室中执行，因此将支持许多新兴的内窥镜计算机辅助手术系统的临床翻译。
The oblique-viewing (i.e.,angled) rigid endoscope is a commonly used tool in conventional endoscopic surgeries. The relative rotation between its two moveable parts, the telescope and the camera head, creates a rotation offset between the actual and the projection of an object in the camera image. A calibration method tailored to compensate such offset is needed. We developed a fast calibration method for oblique-viewing rigid endoscopes suitable for clinical use. In contrast to prior approaches based on optical tracking, we used electromagnetic (EM) tracking as the external tracking hardware to improve compactness and practicality. Two EM sensors were mounted on the telescope and the camera head, respectively, with considerations to minimize EM tracking errors. Single-image calibration was incorporated into the method, and a sterilizable plate, laser-marked with the calibration pattern, was also developed. Furthermore, we proposed a general algorithm to estimate the rotation center in the camera image. Formulas for updating the camera matrix in terms of clockwise and counterclockwise rotations were also developed. The proposed calibration method was validated using a conventional 30°, 5-mm laparoscope. Freehand calibrations were performed using the proposed method, and the calibration time averaged 2 min and 8 s. The calibration accuracy was evaluated in a simulated clinical setting with several surgical tools present in the magnetic field of EM tracking. The root-mean-square re-projection error averaged 4.9 pixel (range 2.4–8.5pixel, with image resolution of 1280 × 720) for rotation angles ranged from −40.3° to 174.7° We developed a method for fast and accurate calibration of oblique-viewing rigid endoscopes. The method was also designed to be performed in the operating room and will therefore support clinical translation of many emerging endoscopic computer-assisted surgical systems.
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DOI：
10.1007/s11548-016-1406-3
发表时间：
2016-06
影响因子：
3
作者：
Liu X;Plishker W;Zaki G;Kang S;Kane TD;Shekhar R
通讯作者：
Shekhar R
DOI：
10.1007/s00464-010-0890-8
发表时间：
2010-08-01
影响因子：
3.1
作者：
Shekhar, Raj;Dandekar, Omkar;Park, Adrian
通讯作者：
Park, Adrian
DOI：
10.1007/s11548-015-1348-1
发表时间：
2016-08-01
影响因子：
3
作者：
Nijkamp, Jasper;Schermers, Bram;Ruers, Theo
通讯作者：
Ruers, Theo
影响因子：
10.6
作者：
Franz, Alfred M.;Haidegger, Tamas;Maier-Hein, Lena
通讯作者：
Maier-Hein, Lena
影响因子：
--
作者：
Wu, C.;Jaramaz, B.;Narasimhan, S. G.
通讯作者：
Narasimhan, S. G.