Motion compensation in short-scan CBCT reconstructions for dental applications

Cone-beam computed tomography (CBCT) is a widely established technique for dental imaging that provides detailed three-dimensional representations of the maxillofacial region. However, its application in clinical practice is often impaired by patient movement during image acquisition, leading to severe image artifacts and compromised diagnostic accuracy. Cone beam CT system manufacturers have incorporated mechanical fixations to prevent patient movement, however, these fixtures lack complete rigidity and still permit some degree of movement. In clinical situations, short scan acquisitions are a common scenario where only a limited portion of the full 360° rotation is covered during the scan. A shorter scan has the advantage of a shorter exposure time and requires a device of smaller size which is very convenient due to space constraints in many dentist's clinics. This paper proposes a multi-stage approach to compensate for patient motion in short-scan CBCT reconstructions. In contrast to conventional iterative techniques that require multiple reconstructions during compensation, this approach requires only a few reconstructions computed with the Feldkamp-Davis-Kress (FDK) algorithm as the reference for compensation. Before the motion compensation stage, the reference volume undergoes regularization. The motion compensation is then accomplished by optimizing motion parameters through a regularized 3D-2D image registration process. The results show that the proposed motion compensation approach effectively reduces motion-induced artifacts in the final reconstruction.