Robust band artifact suppression for cardiac CT

Cardiac cone beam CT images are reconstructed today using phase selective multi-cycle algorithms. According to the acquisition geometry of a helical CT scan, voxels having different z-coordinates are illuminated during non-overlapping time intervals and are reconstructed, therefore, using phase points of different heart cycles. This behavior can lead to inconsistency expressed by step-like and slab-like band artifacts. These bands often seen in coronal and saggital images can hinder the segmentation of the coronary arteries and the diagnosis. Our present work is based on the understanding that by forcing a smooth change of the back-projection weights with respect to the voxel z-coordinate band artifacts will be suppressed. Using this approach, we have developed a new back-projection weighting scheme that replaces the original weighting scheme of the so-called extended cardiac reconstruction method for helical cone beam CT (Grass et al, Phys. Med. Biol. 2003). We evaluated this scheme on patients having different heart rates. The strong suppression of band artifacts and the visualization of the coronary arteries obtained using this scheme will be presented.