For trauma and orthopedic surgery, maneuvering a mobile C-arm X-ray device into a desired position in order
to acquire the right picture is a routine task. The precision and ease of use of the C-arm positioning becomes
even more important for more advanced imaging techniques as parallax-free X-ray image stitching, for example.
Standard mobile C-arms have only five degrees of freedom (DOF), which definitely restricts their motions that
have six DOF in 3D Cartesian space. We have proposed a method to model the kinematics of the mobile Carm
and operating table as an integrated 6DOF C-arm X-ray imaging system.1 This enables mobile C-arms
to be positioned relative to the patient's table with six DOF in 3D Cartesian space. Moving mobile C-arms
to a desired position and orientation requires finding the necessary joint values, which is an inverse kinematics
problem. In this paper, we present closed-form solutions, i.e. analytic expressions, obtained in an algebraic way
for the inverse kinematics problem of the 6DOF C-arm model. In addition, we implement a 6DOF C-arm system
for interactively radiation-free C-arm positioning based on a continuous guidance from C-arm pose estimation.
For this we employ a visual marker pattern attached under the operating table and a mobile C-arm system
augmented by a video camera and mirror construction. In our experiment, repositioning C-arm to a pre-defined
pose in a phantom study demonstrates the practicality and accuracy of our developed 6DOF C-arm system.