Schumann Steffen, Thelen Benedikt, Ballestra Steven, Nolte Lutz-P, Büchler Philippe, Zheng Guoyan
Institute for Surgical Technology and Biomechanics (ISTB), University of Bern, Switzerland.
Institute for Surgical Technology and Biomechanics (ISTB), University of Bern, Switzerland.
Med Eng Phys. 2014 Jul;36(7):968-74. doi: 10.1016/j.medengphy.2014.04.001. Epub 2014 May 14.
X-ray imaging is one of the most commonly used medical imaging modality. Albeit X-ray radiographs provide important clinical information for diagnosis, planning and post-operative follow-up, the challenging interpretation due to its 2D projection characteristics and the unknown magnification factor constrain the full benefit of X-ray imaging. In order to overcome these drawbacks, we proposed here an easy-to-use X-ray calibration object and developed an optimization method to robustly find correspondences between the 3D fiducials of the calibration object and their 2D projections. In this work we present all the details of this outlined concept. Moreover, we demonstrate the potential of using such a method to precisely extract information from calibrated X-ray radiographs for two different orthopedic applications: post-operative acetabular cup implant orientation measurement and 3D vertebral body displacement measurement during preoperative traction tests. In the first application, we have achieved a clinically acceptable accuracy of below 1° for both anteversion and inclination angles, where in the second application an average displacement of 8.06±3.71 mm was measured. The results of both applications indicate the importance of using X-ray calibration in the clinical routine.
X射线成像是最常用的医学成像方式之一。尽管X射线平片为诊断、治疗计划制定和术后随访提供了重要的临床信息，但其二维投影特性导致的解读困难以及未知的放大倍数限制了X射线成像的全面优势。为了克服这些缺点，我们在此提出了一种易于使用的X射线校准物体，并开发了一种优化方法，以稳健地找到校准物体的三维基准点与其二维投影之间的对应关系。在这项工作中，我们展示了这一概述概念的所有细节。此外，我们展示了使用这种方法从校准后的X射线平片中精确提取信息在两种不同骨科应用中的潜力：术后髋臼杯植入物方向测量和术前牵引测试期间的三维椎体位移测量。在第一个应用中，我们在髋臼前倾角和倾斜角方面都达到了临床可接受的低于1°的精度，在第二个应用中，测量的平均位移为8.06±3.71毫米。这两个应用的结果表明了在临床常规中使用X射线校准的重要性。
