Modeling Kinematics of Mobile C-Arm and Operating Table as an Integrated Six Degrees of Freedom Imaging System

Abstract

Maneuvering mobile C-arms to a desired position and orientation during surgery is not only a routine surgical task, e.g. for C-arm repositioning, but also an indispensable step for advanced X-ray imaging techniques, e.g. parallax-free X-ray image stitching. Standard mobile C-arms have only five degrees of freedom (DOF), which definitely restricts their motions that have six DOF in 3D Cartesian space. In this paper, we enable the mobile C-arm to have six DOF relative to the patient’s table by integrating a translational movement of the patient’s table into the mobile C-arm kinematics. We present a novel method to model the kinematics of the mobile C-arm and operating table as an integrated 6DOF C-arm X-ray imaging system. Kinematic singularities of the 6DOF C-arm model are determined by analyzing its manipulator Jacobian matrix. Inverse kinematic analysis is employed in order to find the required joint values to move the C-arm into the desired position and orientation. Our proposed 6DOF C-arm modeling paves the way for advanced applications in the fields of surgical navigation and advanced X-ray imaging that require C-arms to be precisely positioned or repositioned relative to the patient’s table with six DOF. In our implementation, we employ a visual planar marker pattern and a standard mobile C-arm augmented by a video camera in order to obtain a relationship between the C-arm system and the patient’s table. C-arm repositioning experiments on phantom study demonstrate the practicality and accuracy of our developed 6DOF C-arm system, and show the improved accuracy of C-arm repositioning by using the 6DOF C-arm model over the 5DOF C-arm model.