Elfring Robert, de la Fuente Matías, Radermacher Klaus
Chair of Medical Engineering, Helmholtz-Institute for Biomedical Engineering, RWTH Aachen University, Aachen, Germany.
Comput Aided Surg. 2010;15(1-3):1-12. doi: 10.3109/10929081003647239.
The technology for localization of surgical tools with respect to the patient's reference coordinate system in three to six degrees of freedom is one of the key components in computer aided surgery. Several tracking methods are available, of which optical tracking is the most widespread in clinical use. Optical tracking technology has proven to be a reliable method for intra-operative position and orientation acquisition in many clinical applications; however, the accuracy of such localizers is still a topic of discussion. In this paper, the accuracy of three optical localizer systems, the NDI Polaris P4, the NDI Polaris Spectra (in active and passive mode) and the Stryker Navigation System II camera, is assessed and compared critically. Static tests revealed that only the Polaris P4 shows significant warm-up behavior, with a significant shift of accuracy being observed within 42 minutes of being switched on. Furthermore, the intrinsic localizer accuracy was determined for single markers as well as for tools using a volumetric measurement protocol on a coordinate measurement machine. To determine the relative distance error within the measurement volume, the Length Measurement Error (LME) was determined at 35 test lengths. As accuracy depends strongly on the marker configuration employed, the error to be expected in typical clinical setups was estimated in a simulation for different tool configurations. The two active localizer systems, the Stryker Navigation System II camera and the Polaris Spectra (active mode), showed the best results, with trueness values (mean +/- standard deviation) of 0.058 +/- 0.033 mm and 0.089 +/- 0.061 mm, respectively. The Polaris Spectra (passive mode) showed a trueness of 0.170 +/- 0.090 mm, and the Polaris P4 showed the lowest trueness at 0.272 +/- 0.394 mm with a higher number of outliers than for the other cameras. The simulation of the different tool configurations in a typical clinical setup revealed that the tracking error can be estimated to be 1.02 mm for the Polaris P4, 0.64 mm for the Polaris Spectra in passive mode, 0.33 mm for the Polaris Spectra in active mode, and 0.22 mm for the Stryker Navigation System II camera.
在三到六个自由度上，将手术工具相对于患者参考坐标系进行定位的技术是计算机辅助手术的关键组成部分之一。有几种跟踪方法可供选择，其中光学跟踪在临床应用中最为广泛。光学跟踪技术已被证明在许多临床应用中是一种可靠的术中位置和方向获取方法；然而，此类定位器的准确性仍是一个讨论的话题。在本文中，对三种光学定位系统——NDI Polaris P4、NDI Polaris Spectra（主动和被动模式）以及史赛克导航系统II摄像头——的准确性进行了评估和严格比较。静态测试表明，只有Polaris P4表现出明显的预热行为，在开机42分钟内观察到准确性有显著变化。此外，使用坐标测量机上的体积测量协议，确定了单个标记以及工具的固有定位器准确性。为了确定测量体积内的相对距离误差，在35个测试长度下确定了长度测量误差（LME）。由于准确性在很大程度上取决于所采用的标记配置，因此在针对不同工具配置的模拟中估计了典型临床设置中预期的误差。两种主动定位系统，史赛克导航系统II摄像头和Polaris Spectra（主动模式），表现出最佳结果，其真实性值（平均值±标准差）分别为0.058±0.033毫米和0.089±0.061毫米。Polaris Spectra（被动模式）的真实性为0.170±0.090毫米，Polaris P4的真实性最低，为0.272±0.394毫米，异常值数量比其他摄像头更多。在典型临床设置中对不同工具配置的模拟表明，Polaris P4的跟踪误差估计为1.02毫米，Polaris Spectra被动模式为0.64毫米，Polaris Spectra主动模式为0.33毫米，史赛克导航系统II摄像头为0.22毫米。
