A computationally efficient approach for 2D-3D image registration.

2D-3D image registration has become an important tool in many clinical applications such as image-guided surgery and the kinematic analysis of bones in knee and ankle joints. A limitation of this approach is the need to recalculate the voxel values in the 3D volume for every iteration of the registration procedure. In this paper we propose a new 2D-3D image registration algorithm which uses the projected 2D data from the original 3D CT volume. For the majority of the iterations of the algorithm, only this 2D data is updated rather than the 3D volume. Experimental results show that similar registration accuracy to the approach which employs 3-D updates at every iteration can be achieved with our method if we employ 3-D updates only in the last few iterations. As a result of reducing the number of 3-D updates, the proposed approach reduces the time required to perform the registration by approximately a factor of five.