A comparison of cone-beam computed tomography image quality obtained in phantoms with different fields of view, voxel size, and angular rotation for iCAT NG

Abstract

Objectives: To characterize cone-beam computed tomography (CBCT) image quality (IQ) and dose for different fields of view (FOVs), voxel size, and angular rotation. Materials and Methods: IQ parameters, including image noise, homogeneity, geometric distortion, artifacts, contrast resolution and spatial resolution, and radiation dose, were measured for different FOV, voxel size, and angular rotation for an iCAT NG CBCT machine. Results: Noise increased with smaller voxel sizes as measured in the homogeneity layers. The 360° gantry rotation leads to improvements in contrast-to-noise ratio and spatial resolution and a decrease in artifacts compare to 180° gantry rotation with the same voxel size and FOV. Dose reduction was not always observed with smaller FOVs if smaller voxel sizes and longer scan times are used. Some of the test objects included in the phantom are not useful for dental CBCT machines, such as the range of resolutions tested by the bar pattern insert and the suitability of the materials used for the contrast assessment layer. Conclusions: A reduction in the patient dose can be achieved by reducing the angular rotation to 180°, increasing the acquired voxel size or decreasing the FOV height. However, using the reduced rotation angle also leads to increased artifacts around metallic objects. Changing the voxel size did not necessarily lead to improved spatial resolution or reduced dose, as some of the voxel sizes on this machine have identical imaging parameters.