Bertelsen A, Garin-Muga A, Echeverría M, Gómez E, Borro D
CEIT and Tecnun (University of Navarra), San Sebastián, Spain.
Comput Med Imaging Graph. 2014 Oct;38(7):558-68. doi: 10.1016/j.compmedimag.2014.06.004. Epub 2014 Jun 19.
This work presents an automatic method for distortion correction and calibration of intra-operative spine X-ray images, a fundamental step for the use of this modality in computer and robotic assisted surgeries. Our method is based on a prototype calibration drum, attached to the c-arm intensifier during the intervention. The projections of its embedded fiducial beads onto the X-ray images are segmented by the proposed method, which uses its calculated centroids to undo the distortion and, afterwards, calibrate the c-arm. For the latter purpose, we propose the use of a constrained version of the well known Direct Linear Transform (DLT) algorithm, reducing its degrees of freedom from 11 to 3. Experimental evaluation of our method is included in this work, showing that it is fast and more accurate than other existing methods. The low segmentation error level also ensures accurate calibration of the c-arm, with an expected error of 4% in the computation of its focal distance.
这项工作提出了一种用于术中脊柱X射线图像畸变校正和校准的自动方法，这是在计算机和机器人辅助手术中使用这种模态的基本步骤。我们的方法基于一个原型校准鼓，在干预过程中连接到C形臂增强器上。通过所提出的方法对其嵌入的基准珠在X射线图像上的投影进行分割，该方法利用计算出的质心来消除畸变，然后校准C形臂。为了实现后一个目的，我们建议使用著名的直接线性变换（DLT）算法的约束版本，将其自由度从11减少到3。这项工作包括了对我们方法的实验评估，结果表明它比其他现有方法更快且更准确。低分割误差水平也确保了C形臂的精确校准，其焦距计算中的预期误差为4%。
