| Summary: | Category: Basic Sciences/Biologics Introduction/Purpose: Although weight-bearing CT of the foot and ankle definitely reflect the morphology of joint and foot deformity, it is hard to obtain the standing CT due to difficulty of availability. The purpose of this study is to introduce a semi- automatic method based on a deformable surface fitting for achieving the weight-bearing 3D model reconstruction from standing radiographs for foot and ankle. Methods: Our method is based on a Laplacian surface deformation framework using a template model of foot bones. As pre- processing step, we obtained template surface meshes having the average shapes of foot bones from standing CT images (Planmed Verity® CT scanner) in 10 normal volunteers. First, 3D standing CT was obtained by Planmed Verity® CT scanner and used as gold standard of reconstruction for one patient with flatfoot. Second, in the reconstruction step, the surface meshes are deformed following guided user inputs (talus 6, calcaneus 8 in lateral, talus 6, calcaneus 6 in anteroposterior standing radiograph) with geometric constraints to recover the target shapes of patients while preserving average bone shape and smoothness as much as possible. Finally, we compared reconstructed 3D model to original standing CT images. Results: In this study, the comparison results indicate that the obtained reconstruction is close to the actual standing foot and ankle geometry. We present the accuracy and robustness of our method via comparison between the reconstructed 3D models and the original bone surfaces Conclusion: Weight-bearing 3D foot model reconstruction from standing radiographs is concise and the effective method for analysis of foot joint alignment and deformity.
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