Institute for Surgical Technology and Biomechanics, University of Bern, Bern, Switzerland.
Int J Comput Assist Radiol Surg. 2010 Sep;5(5):437-47. doi: 10.1007/s11548-010-0407-x. Epub 2010 Feb 24.
2D-3D image-based registration methods have been developed to measure acetabular cup orientation after total hip arthroplasty (THA). These methods require registration of both the prosthesis and the CT images to 2D radiographs and compute implant position with respect to a reference. The application of these methods is limited in clinical practice due to two limitations: (1) the requirement of a computer-aided design (CAD) model of the prosthesis, which may be unavailable due to the proprietary concerns of the manufacturer, and (2) the requirement of either multiple radiographs or radiograph-specific calibration, usually unavailable for retrospective studies. In this paper, we propose a new method to address these limitations.
A new formulation for determination of post-operative cup orientation, which couples a radiographic measurement with 2D-3D image matching, was developed. In our formulation, the radiographic measurement can be obtained with known methods so that the challenge lies in the 2D-3D image matching. To solve this problem, a hybrid 2D-3D registration scheme combining a landmark-to-ray 2D-3D alignment with a robust intensity-based 2D-3D registration was used. The hybrid 2D-3D registration scheme allows computing both the post-operative cup orientation with respect to an anatomical reference and the pelvic tilt and rotation with respect to the X-ray imaging table/plate. The method was validated using 2D adult cadaver hips.
Using the hybrid 2D-3D registration scheme, our method showed a mean accuracy of 1.0 +/- 0.7 degrees (range from 0.1 degrees to 2.0 degrees) for inclination and 1.7 +/- 1.2 degrees (range from 0.0 degrees to 3.9 degrees) for anteversion, taking the measurements from post-operative CT images as ground truths.
Our new solution formulation and the hybrid 2D-3D registration scheme facilitate estimation of post-operative cup orientation and measurement of pelvic tilt and rotation.
已经开发出基于 2D-3D 图像的配准方法来测量全髋关节置换术（THA）后的髋臼杯方向。这些方法需要将假体和 CT 图像配准到 2D 射线照片，并相对于参考计算植入物的位置。由于两个限制，这些方法在临床实践中的应用受到限制：（1）需要假体的计算机辅助设计（CAD）模型，由于制造商的专有问题，可能无法获得，（2）需要多张射线照片或射线照片特定的校准，通常无法用于回顾性研究。在本文中，我们提出了一种新的方法来解决这些限制。
提出了一种新的确定术后杯方向的公式，该公式将射线照相测量与 2D-3D 图像匹配相结合。在我们的公式中，可以使用已知方法获得射线照相测量值，因此挑战在于 2D-3D 图像匹配。为了解决这个问题，使用了一种混合 2D-3D 配准方案，该方案结合了基于地标到射线的 2D-3D 对准和稳健的基于强度的 2D-3D 配准。混合 2D-3D 配准方案允许计算术后髋臼杯相对于解剖参考的方向以及骨盆相对于 X 射线成像台/板的倾斜和旋转。该方法使用 2D 成人尸体髋关节进行了验证。
使用混合 2D-3D 配准方案，我们的方法显示出术后 CT 图像测量值的倾斜度平均准确度为 1.0 +/- 0.7 度（范围从 0.1 度到 2.0 度），前倾角的平均准确度为 1.7 +/- 1.2 度（范围从 0.0 度到 3.9 度）。
我们的新解决方案公式和混合 2D-3D 配准方案有助于估计术后杯方向和测量骨盆倾斜和旋转。
