  Purpose: Patient movement affects image quality in oral and maxillofacial
cone-beam CT imaging. While many efforts are made to minimize the possibility
of motion during a scan, relatively little attention has been given to motion
compensation after the acquisition. Methods: In a previous study, we proposed a
retrospective motion compensation approach for helical head CT imaging, which
iteratively estimates and compensates for rigid head motion. This study reports
on an extension of the previous method to cone-beam CT imaging. To address the
issue of the limited field-of-view, improvements were made to the original
method. The proposed motion estimation/ motion compensation (ME/MC) method was
evaluated with simulations, phantom and patient studies. Two experts in
dentomaxillofacial radiology assessed the diagnostic importance of the achieved
motion artifact suppression. Results: The quality of the reconstructed images
was improved after motion compensation, and most of the image artifacts were
eliminated. Quantitative analysis by comparison to a reference image
(simulation and phantom) and by calculation of a sharpness metric agreed with
the qualitative observation. Conclusions: The proposed method has the potential
to be clinically applied.
