Artifacts in 3D rotational angiography. An experimental study

Purpose: To investigate artifacts in three-dimensional rotational angiography (3D-RA) in an experimental model and to evaluate which parameters influence their distribution. Material and Methods: 3D-RA was carried out in a circular vessel phantom filled with contrast medium. Two different rotational angulations were used: 160degrees causing 64 images and 180degrees causing 90 or 120 images. The images were transferred to one workstation for reconstruction of axial slices and then to another workstation for 3D reconstructions. The 3D reconstructions were compared with standardized threshold settings. Results: The artifacts occurred where the vessel had a longer path parallel to the rotation plane and became increasingly pronounced when the threshold level was raised. The artifacts decreased in size when rotation angle and number of projections were increased. Conclusion: The quality of the 3D reconstructions from RA was degraded by beam-hardening and sampling artifacts. The sampling artifacts were diminished by increasing both the rotation angle and the number of projections. The distortions in the 3D reconstructions caused by beam-hardening remain to be resolved. The threshold values also had a considerable influence on the 3D reconstructions.