Patent ID: 7204640

Claim:
A method of registering a 2D (two-dimensional) x-ray image of a target with previously generated 3D (three-dimensional) scan data of said target, said x-ray image being characterized by an image plane defined by mutually orthogonal x- and y-coordinates, the method comprising: A. generating at least one reconstructed image from said 3D scan data, said reconstructed image also characterized by the same image plane; B. determining the value of in-plane transformation parameters (x, y, θ) and out-of-plane rotational parameters (r, Φ) for registering said reconstructed image onto said x-ray image, said in-plane and out-of-plane parameters representing a difference in the position of the target as shown in said x-ray image as compared to the position of the target as shown by said image reconstructed from said 3D scan data; wherein r and Φ represent rotations of said target about first and second mutually orthogonal axes, said rotations being out-of-plane with respect to said image plane, said out-of-plane rotations representing a projection of said target onto said image plane; wherein x and y represent an amount of translation of said target within said image plane in the directions of said x- and y-axes, respectively, and θ represents an amount of rotation of said target within said image plane about an axis perpendicular to both said x- and said y-axes; and wherein step B comprises: a. obtaining an initial estimate for said in-plane transformation parameters (x, y, θ) by multi-level matching in 3D (three dimensions), between said x-ray image and said reconstructed image; b. based on said in-plane transformation parameters (x, y, θ) estimated in step a, performing an initial search in one dimension (1D) for each pair of out-of-plane rotation parameters (r, Φ); and c. iteratively refining said in-plane transformation parameters (x, y, θ) and said out-of-plane rotational parameters (r, Φ), until said in-plane and out-of-plane parameters converge to a desired accuracy; and C. aligning a radiation source to the target using the values of the in-plane transformation parameters and the out-of-plane rotational parameters.