A motion correction approach for oral and maxillofacial cone-beam CT imaging.

Patient movement affects image quality in oral and maxillofacial cone-beam computed tomography imaging. While many efforts are made to minimize the possibility of motion during a scan, relatively little attention has been given to motion correction after acquisition. We propose a novel method which can improve the image quality after an oral and maxillofacial scan. The proposed method is based on our previous work and is a retrospective motion estimation and motion compensation (ME/MC) approach that iteratively estimates and compensates for rigid pose change over time. During motion estimation, image update and motion update are performed alternately in a multi-resolution scheme to obtain the motion. We propose use of a feature-based motion update and patch-based image update in the iterative estimation process, to alleviate the effect of limited scan field of view on estimation. During motion compensation, a fine-resolution image reconstruction was performed with compensation for the estimated motion. The proposed ME/MC method was evaluated with simulations, phantom and patient studies. Two experts in dentomaxillofacial radiology assessed the diagnostic importance of the resulting motion artifact suppression. 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 and by calculation of a sharpness metric agreed with the qualitative observation. The results are promising, and further evaluation is required to assess the clinical value of the proposed method.

Publisher Correction: Halve the dose while maintaining image quality in paediatric Cone Beam CT.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Halve the dose while maintaining image quality in paediatric Cone Beam CT.

Cone beam CT (CBCT) for dentomaxillofacial paediatric assessment has been widely used despite the uncertainties of the risks of the low-dose radiation exposures. The aim of this work was to investigate the clinical performance of different CBCT acquisition protocols towards the optimization of paediatric exposures. Custom-made anthropomorphic phantoms were scanned using a CBCT unit in six protocols. CT slices were blinded, randomized and presented to three observers, who scored the image quality using a 4-point scale along with their level of confidence. Sharpness level was also measured using a test object containing an air/PMMA e,dge. The effective dose was calculated by means of a customized Monte Carlo (MC) framework using previously validated paediatric voxels models. The results have shown that the protocols set with smaller voxel size (180 µm), even when decreasing exposure parameters (kVp and mAs), showed high image quality scores and increased sharpness. The MC analysis showed a gradual decrease in effective dose when exposures parameters were reduced, with an emphasis on an average reduction of 45% for the protocol that combined 70 kVp, 16 mAs and 180 µm voxel size. In contrast, both "ultra-low dose" protocols that combined a larger voxel size (400 µm) with lower mAs (7.4 mAs) demonstrated the lowest scores with high levels of confidence unsuitable for an anatomical approach. In conclusion, a significant decrease in the effective dose can be achieved while maintaining the image quality required for paediatric CBCT.