EFFECT OF VARIABILITY OF CURRENT INTENSITY (MILLIAMPERAGE) ON THE GRAY SCALE VALUES DRIVEN FROM CONE BEAM COMPUTED TOMOGRAPHIC IMAGES: AN IN-VITRO STUDY

Document Type : Original Article

Authors

1 Lecturer of Oral and Maxillofacial Radiology, Faculty of Dentistry, Cairo University.

2 Assistant Professor of Oral and Maxillofacial Radiology, Faculty of Dentistry, Cairo University.

Abstract

Introduction: Cone beam computed tomography (CBCT) is an imaging modality of great value in dental field thanks to its lower radiation and high spatial resolution compared to Computed Tomography (CT). However there is still some controversy of using CBCT in bone density assessment. That is why this study was conducted to assess the ability of the gray scale values driven from CBCT by different milliamperage (mA) settings to assess bone density.
Methodology: Seventeen mandibles were included in this study. On each mandible, a gutta percha marker was glued on the buccal surface of bone and another one on the same site on the lingual surface then covered by a layer of pink wax of thickness 13–17mm to simulate soft tissue in patients imaging. The mandibles were fixed to their skulls and imaged by a CBCT machine Planmeca ProMax 3D Mid® with three different mA settings (8, 10 and 12 mA). For the resultant images, both corrected coronal images marked with gutta percha marker and others away from gutta percha marker were assessed and the measured gray scale values were tested for agreement between 3 scans.
Results: Changing of current intensity from 8 mA to 10 mA leads to a change of measured bone density by 24% in cuts away from radiopaque markers and 26% in cuts marked with radiopaque markers. Changing of current intensity from 8 mA to 12 mA leads to a change of measured bone density by at least 18 % in cuts away from radiopaque markers and at least 21% in cuts marked with radiopaque markers. Bland-Altman limits of agreement show clinically poor agreements between the measured densities.
Conclusion: Changing of milliamprage (mA) setting from 8 mA to 10 or 12 mA will change the gray scale values denoting bone density in a statistically significant manner making bone density assessment from CBCT inaccurate.

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