Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, P. R. China; Key Laboratory of Health Informatics, Chinese Academy of Sciences, Shenzhen, P. R. China; University of Chinese Academy of Sciences, Beijing, P.R. China.
Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, P. R. China.
Ultrasound Med Biol. 2020 Aug;46(8):2079-2089. doi: 10.1016/j.ultrasmedbio.2020.03.018. Epub 2020 May 21.
Intra-operative ultrasound (US) is a popular imaging modality for its non-radiative and real-time advantages. However, it is still challenging to perform an interventional procedure under two-dimensional (2-D) US image guidance. Accordingly, the trend has been to perform three-dimensional (3-D) US image guidance by equipping the US probe with a spatial position tracking device, which requires accurate probe calibration for determining the spatial position between the B-scan image and the tracked probe. In this report, we propose a novel probe spatial calibration method by developing a calibration phantom combined with the tracking stylus. The calibration phantom is custom-designed to simplify the alignment between the stylus tip and the B-scan image plane. The spatial position of the stylus tip is tracked in real time, and its 2-D image pixel location is extracted and collected simultaneously. Gaussian distribution is used to model the spatial position of the stylus tip and the iterative closest point-based optimization algorithm is used to estimate the spatial transformation that matches these two point sets. Once the probe is calibrated, its trajectory and the B-scan image are collected and used for the volume reconstruction in our freehand 3-D US imaging system. Experimental results demonstrate that the probe calibration approach results in less than 1-mm mean point reconstruction accuracy. It requires less than 5 min for an inexperienced user to complete the probe calibration procedure with minimal training. The mockup test shows that the 3-D images are geometrically correct with 0.28°-angle accuracy and 0.40-mm distance accuracy.
术中超声（US）因其无辐射和实时的优势，成为一种流行的成像方式。然而，在二维（2-D）US 图像引导下进行介入性操作仍然具有挑战性。因此，目前的趋势是通过为 US 探头配备空间位置跟踪设备来实现三维（3-D）US 图像引导，这需要对探头进行精确校准，以确定 B 扫描图像和跟踪探头之间的空间位置。在本报告中，我们提出了一种新的探头空间校准方法，通过开发一个结合跟踪触笔的校准体模来实现。校准体模是专门设计的，以简化触笔尖端与 B 扫描图像平面之间的对准。触笔尖端的空间位置被实时跟踪，同时提取并收集其 2-D 图像像素位置。我们使用高斯分布来模拟触笔尖端的空间位置，并使用迭代最近点（ICP）优化算法来估计与这两个点集匹配的空间变换。一旦完成探头校准，就可以采集其轨迹和 B 扫描图像，并用于我们的自由手 3-D US 成像系统中的体积重建。实验结果表明，该探头校准方法的平均点重建精度小于 1mm。对于没有经验的用户，只需进行少量培训，不到 5 分钟即可完成探头校准过程。模拟测试表明，3-D 图像具有正确的几何形状，角度精度为 0.28°，距离精度为 0.40mm。
