  This paper presents a two-stage method for beam hardening artifact correction
of dental cone beam computerized tomography (CBCT). The proposed artifact
reduction method is designed to improve the quality of maxillofacial imaging,
where soft tissue details are not required. Compared to standard CT, the
additional difficulty of dental CBCT comes from the problems caused by offset
detector, FOV truncation, and low signal-to-noise ratio due to low X-ray
irradiation. To address these problems, the proposed method primarily performs
a sinogram adjustment in the direction of enhancing data consistency,
considering the situation according to the FOV truncation and offset detector.
This sinogram correction algorithm significantly reduces beam hardening
artifacts caused by high-density materials such as teeth, bones, and metal
implants, while tending to amplify special types of noise. To suppress such
noise, a deep convolutional neural network is complementarily used, where CT
images adjusted by the sinogram correction are used as the input of the neural
network. Numerous experiments validate that the proposed method successfully
reduces beam hardening artifacts and, in particular, has the advantage of
improving the image quality of teeth, associated with maxillofacial CBCT
imaging.
