A projection matrix-based geometric calibration algorithm in CBCT system

Accurate geometric parameter information for cone-beam CT (CBCT) systems is crucial for high-quality image reconstruction. To validate the performance of the algorithms for geometric parameter extraction and projection matrix computation, this paper presents test calibration methods based on a computer simulation. We simulate the projection operation on a calibration phantom using Visual C++ and obtain the center of projection images through an approach based on least squares and genetic algorithm using Matlab programs. To verify the performance of the presented geometric calibration algorithm for projection matrix computation and geometric parameter extraction, CBCT consisting of a flat-panel detector is simulated and the un-calibration reconstructed image is compared with the reconstructed images of the calibration method in this paper. The extracted geometric parameters from the calculated projection matrix are very close to the input values. Compared with the uncorrected reconstructed image, the corrected reconstructed image significantly reduces many artifacts. Experimental results reveal that the presented method is robust and accurate, and can suppress undesirable artifacts of reconstructed images which caused by misaligned scanner geometry.