Johns Hopkins University, Baltimore, Maryland, USA.
Faculty of Medicine and Health, University of Sydney, Sydney, Australia.
Med Phys. 2024 May;51(5):3245-3264. doi: 10.1002/mp.17041. Epub 2024 Apr 4.
Cone-beam CT (CBCT) with non-circular scanning orbits can improve image quality for 3D intraoperative image guidance. However, geometric calibration of such scans can be challenging. Existing methods typically require a prior image, specialized phantoms, presumed repeatable orbits, or long computation time.
We propose a novel fully automatic online geometric calibration algorithm that does not require prior knowledge of fiducial configuration. The algorithm is fast, accurate, and can accommodate arbitrary scanning orbits and fiducial configurations.
The algorithm uses an automatic initialization process to eliminate human intervention in fiducial localization and an iterative refinement process to ensure robustness and accuracy. We provide a detailed explanation and implementation of the proposed algorithm. Physical experiments on a lab test bench and a clinical robotic C-arm scanner were conducted to evaluate spatial resolution performance and robustness under realistic constraints.
Qualitative and quantitative results from the physical experiments demonstrate high accuracy, efficiency, and robustness of the proposed method. The spatial resolution performance matched that of our existing benchmark method, which used a 3D-2D registration-based geometric calibration algorithm.
We have demonstrated an automatic online geometric calibration method that delivers high spatial resolution and robustness performance. This methodology enables arbitrary scan trajectories and should facilitate translation of such acquisition methods in a clinical setting.
具有非圆形扫描轨道的锥形束 CT（CBCT）可以提高 3D 术中图像引导的图像质量。然而，这种扫描的几何校准可能具有挑战性。现有的方法通常需要事先知道基准配置、专用的体模、假定可重复的轨道或长的计算时间。
我们提出了一种新颖的全自动在线几何校准算法，不需要事先了解基准配置。该算法速度快、精度高，可以适应任意扫描轨道和基准配置。
该算法使用自动初始化过程消除了在基准定位中的人为干预，以及迭代细化过程以确保鲁棒性和准确性。我们提供了所提出算法的详细解释和实现。在实验室测试台和临床机器人 C 臂扫描仪上进行了物理实验，以评估在实际约束下的空间分辨率性能和鲁棒性。
物理实验的定性和定量结果表明了该方法的高精度、高效率和鲁棒性。所提出方法的空间分辨率性能与我们现有的基准方法相匹配，该方法使用基于 3D-2D 配准的几何校准算法。
我们已经证明了一种能够提供高空间分辨率和鲁棒性性能的自动在线几何校准方法。这种方法可以适应任意的扫描轨迹，应该有助于在临床环境中推广这种采集方法。
