Department of Surgical Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Robotics and Mechatronics, University of Twente, Enschede, The Netherlands.
Phys Med Biol. 2023 Sep 8;68(18). doi: 10.1088/1361-6560/acf08f.
. Oblique-viewing laparoscopes are popular in laparoscopic surgeries where the target anatomy is located in narrow areas. Their viewing direction can be shifted by telescope rotation without changing the laparoscope pose. This rotation also changes laparoscope camera parameters that are estimated by camera calibration to be able to reproject an anatomical model onto the laparoscopic view, creating augmented reality (AR). The aim of this study was to develop a camera model that accounts for these changes, achieving high reprojection accuracy for any telescope rotation.. Camera parameters were acquired by calibrations encompassing a wide telescope rotation range. For those parameters showing periodic changes upon rotation, interpolation models were created and used to establish an updatable camera model. With this model, corner points of a tracked checkerboard were reprojected onto the checkerboard laparoscopic images, at random rotation angles. Root-mean-square reprojection errors (RMSEs) were calculated between the reprojected and imaged corner points.. Reprojection RMSEs were low and approximately independent on telescope rotation angle, over a wide rotation range of 320°. The mean reprojection RMSE was 2.8±0.7 pixels for a conventional laparoscope and 3.6±0.7 pixels for a chip-on-the-tip (COTT) laparoscope, corresponding to 0.3±0.1 mm and 0.4±0.1 mm in world coordinates respectively. Worst-case reprojection errors were about 9 pixels (0.8 mm) for both laparoscopes.. The camera model developed in this study improves on existing models for oblique-viewing laparoscopes because it provides high reprojection accuracy independent of the telescope rotation angle and is applicable for conventional and chip-on-a-tip oblique-viewing laparoscopes. The work presented here is an important step towards creating accurate AR in image-guided interventions where oblique-viewing laparoscopes are used while simultaneously providing the surgeon the flexibility to rotate the telescope to any desired rotation angle.. CC: camera coordinates; CCToolbox: camera calibration toolbox; COTT: chip-on-the-tip; CS: camera sensor; DD: decentering distortion; FL: focal length; OTS: optical tracking system; PP: principal point; RD: radial distortion; SI: supplementary information;tHE:hand-eye translation component.
. 斜视角腹腔镜在目标解剖结构位于狭窄区域的腹腔镜手术中很受欢迎。它们的观察方向可以通过望远镜旋转而改变，而无需改变腹腔镜的位置。这种旋转还会改变腹腔镜摄像机参数，这些参数需要通过摄像机校准来估计，以便能够将解剖模型重新投影到腹腔镜视图上，从而创建增强现实（AR）。本研究的目的是开发一种能够考虑到这些变化的摄像机模型，实现任何望远镜旋转的高精度重投影。. 通过涵盖广泛望远镜旋转范围的校准来获取摄像机参数。对于那些在旋转时呈现周期性变化的参数，创建了插值模型并将其用于建立可更新的摄像机模型。使用该模型，可以将跟踪棋盘的角点重新投影到随机旋转角度的棋盘腹腔镜图像上。计算重新投影的和成像的角点之间的均方根重投影误差（RMSE）。. 在 320°的宽旋转范围内，重投影 RMSE 较低且大致独立于望远镜旋转角度。对于传统腹腔镜，平均重投影 RMSE 为 2.8±0.7 像素，对于芯片上的尖端（COTT）腹腔镜，为 3.6±0.7 像素，分别对应于世界坐标系中的 0.3±0.1 毫米和 0.4±0.1 毫米。对于两种腹腔镜，最坏情况的重投影误差约为 9 像素（0.8 毫米）。. 本研究中开发的摄像机模型改进了用于斜视角腹腔镜的现有模型，因为它提供了与望远镜旋转角度无关的高精度重投影，并且适用于传统和芯片上的斜视角腹腔镜。这里介绍的工作是朝着在使用斜视角腹腔镜的图像引导干预中创建准确的 AR 迈出的重要一步，同时为外科医生提供旋转望远镜到任何所需旋转角度的灵活性。. CC：相机坐标系；CCToolbox：相机校准工具箱；COTT：芯片上的尖端；CS：相机传感器；DD：偏心失真；FL：焦距；OTS：光学跟踪系统；PP：主点；RD：径向失真；SI：补充信息；tHE：手眼转换组件。
