IADR Abstract Archives
Effect of Scanning Condition on CBCT Gray Level Values
Objectives: There are many benefits of utilizing cone beam computed tomography (CBCT) images. However, a large concern continues to be the radiation dosage required to obtain a quality diagnostic image. Efforts to identify the minimum effective scanning parameters necessary to obtain a diagnostic image are of great importance. However, radiation doses and scanning conditions differ greatly among CBCT machines and their individual settings. The objective of this study is to use the Planmeca Promax 3D mid to examine the effect of scanning condition on gray level values.
Methods: Six full face CBCT scans were taken of the ATOMmax phantom using the Planmeca Promax 3D mid. Scans were obtained with 200, 400, and 600 micron voxel sizes with each voxel size setting taken at a normal dose and an “ultra-low dose.” All scans were taken at 90kV with altered voltage and time parameters. The second cervical vertebra (C2) and right and left mandibular condyles were isolated using ImageJ software and gray levels for the images were obtained. Gray value comparisons were made between regions of interest (ROIs) within the same scan as well as ROIs of separate scans of altered scanning condition. Means, ANOVA, and differences of least square means were calculated. Power to detect a difference in mean gray level of ±500 assuming a SD of 130 was 0.843.
Results: Gray levels means for the 200, 400 and 600 micron voxel sizes were 2591.84, 2533.05, and 2538.41 respectively (p-value=0.3087.) Gray level means for “ultra-low” and high dose settings were 2588.73 and 2520.13 (p-value=0.1117.)
Conclusions: Changes in voxel sizes and altered dosages had no significant effect on mean grey level values at C2, and right and left condyles. Thus, practitioners can reduce patient radiation exposure without significantly reducing gray level values.
Methods: Six full face CBCT scans were taken of the ATOMmax phantom using the Planmeca Promax 3D mid. Scans were obtained with 200, 400, and 600 micron voxel sizes with each voxel size setting taken at a normal dose and an “ultra-low dose.” All scans were taken at 90kV with altered voltage and time parameters. The second cervical vertebra (C2) and right and left mandibular condyles were isolated using ImageJ software and gray levels for the images were obtained. Gray value comparisons were made between regions of interest (ROIs) within the same scan as well as ROIs of separate scans of altered scanning condition. Means, ANOVA, and differences of least square means were calculated. Power to detect a difference in mean gray level of ±500 assuming a SD of 130 was 0.843.
Results: Gray levels means for the 200, 400 and 600 micron voxel sizes were 2591.84, 2533.05, and 2538.41 respectively (p-value=0.3087.) Gray level means for “ultra-low” and high dose settings were 2588.73 and 2520.13 (p-value=0.1117.)
Conclusions: Changes in voxel sizes and altered dosages had no significant effect on mean grey level values at C2, and right and left condyles. Thus, practitioners can reduce patient radiation exposure without significantly reducing gray level values.