Browsing by Author "Zhang, Shu"

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    2D-3D Registration for a High-speed Biplanar Videoradiography Imaging System
    (2022-04) Zhang, Shu; Lichti, Derek; Detchev, Ivan; Ronsky, Janet; Wang, Ruisheng; Armenakis, Costas; Lichti, Derek
    High-Speed Biplanar Videoradiography (HSBV) is an X-ray based imaging system that can derive dynamic bony translations and rotations. The 2D-3D registration process matches a 3D bone model acquired from magnetic resonance imaging (MRI) or computed tomography (CT) scans with the 2D X-ray image pairs. 2D-3D registration is usually conducted in two ways, marker-based and model-based registration. The marker-based method is known for its high registration accuracy thanks to corresponding marker pairs. On the other hand, the model-based method avoids the implantation of radiopaque beads but uses the radiograph’s features, intensities, or gradients to accomplish the data alignment. Two novel marker-based registration methods, the back-projection and the projection methods, were proposed and compared with the state-of-the-art RSA (Roentgen Stereophotogrammetric Analysis) method. A 3D printed bone model with beads was used to validate the proposed methods. The results showed that both methods acquired higher accuracy than the RSA method. In addition, the projection and back-projection techniques can be used for the model-based registration while the RSA method cannot. The projection method was applied to a model-based registration to achieve higher accuracy, providing a 3D reconstruction accuracy of 0.79 mm for both the tibia and femur. By using the non-rigid transformation with a scale factor, this accuracy was successfully increased to 0.56 mm for the tibia and 0.64 mm for the femur. The discrepancies in the 2D-3D registration that led to the non-rigid transformation were validated. It was caused by the offset between the detected edge points in the radiographs and their actual position. A Kalman filter was tested on the marker- and model-based registration results with different random processes and parameters. For marker-based registrations, the standard deviations of the kinematics parameters were improved by 25 – 62% for the translations and 35 – 43% for the rotations. For the model-based registration, these standard deviations were improved by 6 – 38% and 29 – 38%, respectively. While the projection method provided higher accuracy, the back-projection method had the larger capture range for the initialization. An automatic initialization method with 64 starting poses based on the back-projection method was proposed and validated. It successfully eliminated the user intervention in the registration initialization. The improved 2D-3D registration with non-rigid transformation and dynamic estimation allows the determination of accurate 3D kinematic parameters with high efficiency. These kinematic parameters can be used to calculate joint cartilage contact mechanics that provide insight into the mechanical processes and mechanisms of joint degeneration or pathology.