Abstrakt: |
Objectives: The aim of this study was to reveal the three-dimensional fluctuation of voxel values in a uniform material placed inside a phantom simulating a human head when it was scanned with cone-beam computed tomography (CBCT) for dental use. Methods: We employed a cylindrical acrylic phantom to simulate a human head. Iodine solution, water, or air was placed inside the phantom, which was then scanned using CBCT. Regions of interest (ROIs) were set on the obtained CBCT images, and the mean voxel value in each ROI was measured. Finally, the profiles of the voxel values in the bottom-to-top (BT) and anterior-to-posterior (AP) directions in the field of view (FOV) were investigated. Results: For the BT direction, the voxel values were almost constant regardless of the slice position (standard deviation: <10.0 for each material). However, in the AP direction, the profiles showed different tendencies depending on the contents of the acrylic phantom. When iodine solution or air was scanned, the profiles showed a cupping shape, as the voxel values in the epicenter were lower than those in the periphery of the FOV. In contrast, when water was placed in the phantom, the profiles showed a capping shape, as the voxel values in the epicenter were higher. Conclusions: Three-dimensional fluctuation of voxel values was evaluated for uniform scan targets on CBCT scanning. In the longitudinal direction, the voxel values were almost constant. However, in the axial plane, the fluctuation was so large that estimation from voxel values might not be reliable. [ABSTRACT FROM AUTHOR] |