Standardization of a cone beam computed tomography machine in evaluating bone density: a novel approach

Advent of cone beam computed tomography (CBCT) in dentistry has brought us to a new era of precise imaging. Radiographic evaluation of a CBCT image is more informational when compared to CT. The density measurements in CBCT images are based on greyscale values, which are more accurate in CT and these values are inconsistent across various CBCT machines. Hence, we aim at standardizing a single CBCT scanner to evaluate or determine tissue density from the greyscale values.

A total of 8 halves of undamaged, dry goat mandibles are included in the study. Scans of the bone are obtained using the KODAK CBCT unit and the PHILLIPS CT machine respectively. Densities are evaluated at 96 points on both the CT scans and the CBCT scans, respectively, using the Radiant Dicom viewer. The obtained data is entered into the excel spreadsheet and subjected to statistical analysis.

The greyscale values are obtained from each of the CBCT scans. Hounsfield units are calculated from CT images coinciding with the same points on CBCT scans. The collected data is subjected to linear regression analysis and an equation is derived to determine Hounsfield units (calculated HU units) from greyscale values of CBCT images. We found no significant difference between the mean original HU units and the mean calculated HU units, thus making the equation reliable for calculating HU units from CBCT greyscale values.

Our results conclude that the technique was effective in calculating the Original density of tissues using grey standards of CBCT scans.