Dental cone beam computed tomography (CBCT) offers a variety of fields of view (FOV), ranging from the entire craniofacial complex down to an individual tooth. To manage the radiation dose to the patient, partial rotation scanning is often used. However, the images suffer from non-uniformities related to attenuation of the beam as it crosses the patient anatomy and the uneven radiation field due in part to scattered radiation. We have modelled the cupping artifact in the maxillofacial field of view and applied a correction to improve uniformity in the image. We applied this correction to smaller fields of view. Images were obtained using a Carestream 9300 CBCT system of the SEDENTEX image quality phantom and 2 anthropomorphic skull phantoms. The maxillofacial FOV (17x11 cm2 ) was used with clinical settings for an average adult (90 kVp, 4 mA, 6.4 s) and reconstructed with 0.25 mm voxel spacing. In MATLAB, we modeled the 2D surface across a uniform section of the SEDENTEX phantom with a polynomial fit to find an offset that could be added to reduce the cupping artefact. This offset was then applied to the images of the anthropomorphic and SEDENTEX phantoms for 17x11 cm2 , 10x10 cm2 , 10x5 cm2 and 8x8 cm2 FOVs. The offset was cropped for the 10x10 cm2 , 10x5 cm2 and 8x8 cm2 FOVs. For all images, the uniformity was improved. From this study, we conclude that a single correction matrix can be used for all 4 FOVs on this machine to improve image quality.
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