Apparatus and method for registering 2D radiographic images with images reconstructed from 3D scan data

A system for registering at least one 2D radiographic image of a target with at least one image reconstructed from previously generated 3D scan data of said target, said radiographic image being characterized by an image plane defined by mutually orthogonal x- and y-axes, the system comprising:

• a. means for providing said 3D scan data of said target;
• b. a radiation source for generating at least one radiographic imaging beam having a known intensity, and having a known location and angle relative to said target;
• c. an imaging system for generating a 2D radiographic image of said target in near real time;
• and
• d. a controller, including:
• i) means for generating said at least one reconstructed 2D image of said target, using said 3D scan data, and using said known location, angle, and intensity of said imaging beam;
• and
• ii) software for determining a set of in-plane transformation parameters (x, y, θ) and out-of-plane rotational parameters (r, Φ), said in-plane and out-of-plane parameters representing a difference in the position of the target as shown in said radiographic image as compared to the position of the target as shown by said 2D reconstructed image;
• wherein said software comprises means fix performing a 3D multi-level matching to determine an initial estimate for said in-plane transformation parameters (x, y, θ);
• 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;
• and
• 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.

A method, comprising:

• acquiring x-ray images of a target volume in a first image plane and a second image plane, the x-ray images defining a present orientation of the target volume;
• generating synthetic x-ray reference images of the target volume from 3-dimensional scan data representing a previous orientation of the target volume, the synthetic x-ray reference images corresponding to in-plane transformations and out-of-plane rotations of the target volume projected onto the first image plane and the second image plane;
• determining a difference between the present orientation of the target volume and the previous orientation of the target volume in three translational coordinates and three rotational coordinates by comparing in-plane transformation parameters and out-of-plane rotation parameters of the x-ray images and the synthetic x-ray reference images in the first image plane and the second image plane, wherein determining said difference comprises searching the in-plane transformation parameters in the first image plane and the second image plane using a first similarity measure between the x-ray images and the synthetic x-ray reference images in a 3-dimensional multi-level search;
• and
• aligning a radiation source to the target volume using the difference between the present orientation of the target volume and the previous orientation of the target volume.

A system, comprising:

• a radiation source and an imaging system to generate 2D radiographic images of a target volume in a first image plane and a second image plane, the 2D radiographic images defining a present orientation of the target volume;
• a 3D scan data generator to generate reconstructed 2D reference images of the target volume from 3D scan data representing a previous orientation of the target volume, the reconstructed 2D reference images corresponding to in-plane transformations and out-of-plane rotations of the target volume projected onto the first image plane and the second image plane;
• and
• a controller coupled with the radiation source, the imaging system and the 3D scan data generator, the controller configured to:
• determine a difference between the present orientation of the target volume and the previous orientation of the target volume in three translational coordinates and three rotational coordinates by comparing in-plane transformation parameters and out-of-plane rotation parameters of the 2D radiographic images and the reconstructed 2D reference images in the first image plane and the second image plane, wherein to determine said difference the controller is configured to search the in-plane transformation parameters in the first image plane and the second image plane using a first similarity measure between the 2D radiographic images and the reconstructed 2D reference images in a 3-dimensional multi-level search.