Patent ID: 8107592

Claim:
A method for computed tomography (CT) for calculating mathematical corrections for geometric distortion of a non-rigid CT system, the method comprising: A. during a calibrating phase, executing the steps of (i) calculating a central axis of rotation for a non-circular orbit of a CT scanner using projection positions at which a detector of the CT scanner acquires images of a volume to be reconstructed, where the central axis of rotation is the central axis of a resample circle, the resample circle being the best-fit circle representing the non-circular orbit of the CT scanner based on the projection positions; (ii) defining a coordinate system of a reconstruction volume of an object based on the resampled circle comprising an x-axis and a y-axis; (iii) calculating a resampled detector plane of the detector of the CT scanner for each projection position, where the resampled detector plane is in a plane tangential to the resampled circle; (iv) defining a source-normal ray for each projection position, the source-normal ray being a ray in the same plane as the resampled circle and passing through the center point of the resample circle and intersecting a center point of the resampled detector plane; and (v) calculating and storing a projection offset for each projection position based on a comparison of the x-axis and a further axis found at each projection position, the further axis being in the plane of the resampled circle and intersecting the midpoint of the resampled detector plane at each projection position; and B. in a runtime phase, i) applying the projection offset calculated in the calibration phase to correct for geometric distortion of projections of an object to be reconstructed acquired with the non-rigid CT system to obtain corrected projections; and ii) performing volume reconstruction with the corrected projections, where the reconstruction utilizes a determined order in which to process two or more bricks of the volume to be reconstructed based at least in part on the proximity of said bricks to one another when images of the bricks are projected onto the plane of the detector.