Differentiation of periapical granulomas and radicular cysts by digital radiometric analysis.

It is generally accepted that two of the most commonly seen radiolucencies, the periapical granuloma and the radicular cyst, cannot be differentiated radiographically. The purpose of this investigation was to determine the feasibility of identifying radiometric differences in these two pathologic conditions by analyzing the patterns of the gray-level distributions of digitized radiographic images. Radiographs used in the study had been sent by practitioners to the School of Dentistry with tissue specimens. Radiographs of lesions identified as periapical granulomas and radicular cysts in the mandibular posterior quadrant were included in the study. The radiographs were digitized and regions of interest were drawn to include the lesions. Frequency distributions (histogram) with 256 gray-scale intervals and a cumulative percent histogram were computed. The typical histograms of the dental granulomas had narrower ranges and lower gray-scale values than did cysts. The results of this study indicate that it is feasible to radiometrically differentiate between lesions that are visually indistinguishable on radiographs.