Patent attributes
The present invention is directed to an alternative geometric calibration method based on a calibration phantom with multiple line-shaped markers. The markers can in some embodiments take the form of radio-opaque wires. Line fiducials overcome the occlusion hazards of spherical fiducials, because their projections overlap very mildly as long as the wires are mutually non-coplanar in 3D. This makes the phantom amenable to a wider range of orbits and less sensitive to phantom positioning. Equations relating the pose of 3D line-shaped objects to their 2D radiographic projections are then used as the basis for view-by-view geometry estimation. The technique can flexibly accommodate a wide range of different CT scan trajectories, including strongly noncircular trajectories known to provide better image quality than standard circular scans.
