Accurate and efficient image intensifier distortion correction algorithm for volume tomographic angiography

The recent advance in image intensifier based volume tomog- raphic angiography has stirred a significant interest in the development of accurate and efficient algorithms to correct image intensifier distor- tions. An algorithm and its calibration protocol are developed to correct the distortion caused by the image intensifier-CCD camera imaging chain in a single step regardless of distortion sources. This algorithm first partitions a distorted image into small quadrilateral regions, then maps each region individually to the corrected image using the corresponding bilinear functions. The general applicable parameters of these bilinear functions can be obtained using a specially designed grid phantom. The algorithm and the calibration protocol are tested using this grid phantom on a newly built image intensifier based volume tomographic angiogra- phy imaging system. The maximum distortion error is reduced from 5.96 mm before correction to 0.05 mm after correction. Further validation of the proposed algorithm is performed through three-dimensional tomog- raphic reconstructions of a vascular phantom and animal studies. The reconstruction results indicate that the accuracy of the algorithm and the calibration protocol is acceptable for volume tomographic angiography. This algorithm can also be applied to radiation therapy and stereosurgi- cal treatment planning where image intensifier distortions must be cor- rected.