Improving CT-number Accuracy of Dental Cone-beam CT by Correcting Scattered X-rays

Abstract

A method for correcting X-ray scattering to improve the CT-number accuracy of dental cone-beam CT images is proposed. The proposed method is based on an approximate function; that is, X-ray scatter components are approximately calculated by using the mean pixel value of a measured transmittance image and a scatter parameter. The scatter parameter is defined as the ratio of scatter-generation and attenuation coefficients. When the correction method was applied to an inhomogeneous head phantom, the CT numbers were almost completely corrected and the artifacts in the corrected axial and sagittal reconstructed images were reduced. The absolute error from the true CT number for the mandible was reduced from 549 to 30 HU by the correction method. Volume-rendering images with few artifacts were also acquired using the corrected reconstructed images. These results demonstrate that the proposed method is effective for improving the accuracy of hardness and shape measurements of a mandible in cone-beam CT images. The method enables the use of a model based on such corrected cone-beam CT images for diagnostic support and surgical planning.