Fully automatic reconstruction of personalized 3D volumes of the proximal femur from 2D X-ray images

Accurate preoperative planning is crucial for the outcome of total hip arthroplasty. Recently, 2D pelvic X-ray radiographs have been replaced by 3D CT. However, CT suffers from relatively high radiation dosage and cost. An alternative is to reconstruct a 3D patient-specific volume data from 2D X-ray images.

In this paper, based on a fully automatic image segmentation algorithm, we propose a new control point-based 2D–3D registration approach for a deformable registration of a 3D volumetric template to a limited number of 2D calibrated X-ray images and show its application to personalized reconstruction of 3D volumes of the proximal femur. The 2D–3D registration is done with a hierarchical two-stage strategy: the scaled-rigid 2D–3D registration stage followed by a regularized deformable B-spline 2D–3D registration stage. In both stages, a set of control points with uniform spacing are placed over the domain of the 3D volumetric template first. The registration is then driven by computing updated positions of these control points with intensity-based 2D–2D image registrations of the input X-ray images with the associated digitally reconstructed radiographs, which allows computing the associated registration transformation at each stage.

Evaluated on datasets of 44 patients, our method achieved an overall surface reconstruction accuracy of \(0.9 \pm 0.2\,\hbox {mm}\) and an average Dice coefficient of \(94.4 \pm 1.1\,\%\). We further investigated the cortical bone region reconstruction accuracy, which is important for planning cementless total hip arthroplasty. An average cortical bone region Dice coefficient of \(85.1 \pm 2.9\,\%\) and an inner cortical bone surface reconstruction accuracy of \(0.7 \pm 0.2\,\hbox {mm}\) were found.

In summary, we developed a new approach for reconstruction of 3D personalized volumes of the proximal femur from 2D X-ray images. Comprehensive experiments demonstrated the efficacy of the present approach.