Navigation of the drilling capsule

本课题主要研究仪器位置自动检测和轨迹控制。将多口骨手术的直通路规划扩展到非线性通路，需要对器械监测和轨迹控制进行调整。为了精确地跟随仪器预先计划的轨迹，必须确定钻井胶囊的六个自由度。在项目的初始阶段，我们开发了使用c臂锥束计算机断层扫描系统（CBCT）精确确定仪器位置的方法。然而，这些方法仅限于五个自由度的检测。此外，不能违反可接受的辐射水平，因此不可能获得连续的数据。为克服上述缺点，应考虑增设跟踪系统。电磁跟踪（EMT）是合适的，由于使用了小型传感器，即使它们被隐藏，也可以连续跟踪。由于EMT准确性有限，术中CBCT投影被用于确定确切的器械位置，并以此为基础调整EMT数据以适应接下来的时间段。在连续的CBCT扫描之间，使用EMT系统对仪器进行连续跟踪。必须研究扫描时间间隔，以便在不危及患者的情况下尽量减少辐射暴露。这些间隔主要取决于EMT系统的准确性、计划轨迹的形状以及到风险结构的距离。将设计一个合适的控制概念来同步和控制各个组件（规划系统、EMT、c臂和钻井胶囊）。通过有意义的两种跟踪系统（EMT和c臂）的集成，安全的连续监测和控制是可行的。此外，还必须提供一种视觉反馈，即仪器相对于患者解剖结构的位置。

Main topics in this subproject are the automatic detection of the instrument position and the trajectory control. The extension of the planning of straight access paths - for multi-port bone surgery - to nonlinear paths requires an adjustment of the instrument monitoring and the trajectory control. In order to follow a pre-planned trajectory with the instrument precisely, the six degrees of freedom of the drilling capsule must be determined. In the initial phase of the project, we developed methods, which allow an accurate determination of the instrument position using a C-arm cone beam computed tomography system (CBCT). However, these methods are limited to the detection of five degrees of freedom. Furthermore, acceptable levels of radiation must not be violated, thus, a continuous data acquisition is not possible. To overcome the aforementioned shortcomings, an additional tracking system should be considered. The electromagnetic tracking (EMT) is suitable, thanks to the used small sensors, which can be continuously tracked, even if they are hidden. Due to the limited EMT accuracy, intra-operative CBCT projections are acquired and used to determine the exact instrument location, and based on it, the EMT data is adjusted for the following time period. Between successive CBCT scans, the instrument is continuously tracked using the EMT system. The scan time intervals have to be investigated in order to minimize the radiation exposure without endangering the patient. These intervals depend principally on the accuracy of the EMT system, the shape of the planned trajectory, and the distances to the risk structures. A suitable control concept will be designed to synchronize and control the various components (planning system, EMT, C-arm, and drilling capsule). By a meaningful integration of the two tracking systems (EMT and C-arm), safe continuous monitoring and control are feasible. Furthermore, a visual feedback - on the instrument position relative to the patient anatomy- has to be offered.