The effect of region of interest variations on morphologic operations dataand gray-level values extracted from digitized dental radiographs

Objective. To determine the correlations among morphologic operations (MO) values and the correlations among gray-level values for regions of interest (ROIs) placed at various locations on digital images of alveolar bone for 45 patients. Study design. As part of a larger study, up to 7 vertical bite-wing radiogr aphs were taken and digitized for Each of 45 patients. Sets of 2 rectangula r ROIs were placed on the digitized images of interdental alveolar bone at 4 locations for each patient. The ROIs (1 crestal and 1 apical) were placed between second premolars and first molars in all 4 dental quadrants. Gray- level values were measured, and MO analysis was performed on each ROI. Desc riptive statistics were calculated and correlations determined. Results. Paired correlations (such as apical vs crestal, left vs right, max illary apical vs mandibular apical) of MO values were weak (r = 0.01-0.21), but corresponding correlations for gray-level values were relatively stron g (r = 0.60-0.92). Conclusion. MO values varied with ROI location considerably more than did g ray-level values. Additionally, ROI size and shape apparently affected MO d ata. Accurate placement and documentation of ROIs appear to be critical con siderations in analyses that use MOs.