Clinical validation of a new substraction radiography technique for periodontal bone loss detection

Background: Diagnostic subtraction radiography (DSR) is a new digital radio graphic image subtraction method designed to enhance detection of crestal o r periapical bone density changes and to help evaluate caries progression i n teeth. In this clinical study, the performance of the DSR method was eval uated for its ability to detect periodontal bone loss and was compared with that of conventional evaluation of radiographs and the standardized cephal ostat-guided image acquisition and subtraction technique (LRA) which served as the "gold standard." Methods: In each of 25 subjects with alveolar crestal bone loss created by periodontal surgery, one set of DSR radiographs and one set of LRA radiogra phs were obtained before and after the surgery. Subtraction images were the n generated by both the proprietary DSR and the LRA techniques. Four viewer s evaluated the paired film sets and both subtraction image sets using a 5 point confidence scale to determine the presence or absence of crestal bone loss. Receiver operating characteristics (ROC) statistical procedures were applied to analyze the diagnostic accuracy and statistical differences bet ween the three imaging modalities. Results: The DSR subtraction viewing generated an ROC area of 0.882. For 2 of the viewers this represented a statistically significant gain (P <0.05) over the conventional viewing of the radiographs which had an average ROC a rea of 0.730. In comparison, the LRA method achieved an area of 0.954. The differences between the LRA and the DSR subtraction methods were not statis tically significant, but the statistical power for claiming equality was lo w ranging from 0.2 to 0.6. Conclusions: The use of the DSR technique in clinical radiographic image ac quisition and subsequent subtraction analysis clearly enhanced the accuracy of alveolar crestal bone loss detection when compared to conventional film viewing. Because this methodology is less resource demanding than LRA and the film exposure techniques and computer-based image analysis skills may b e acquired with only a few hours of training, the DSR has potential in clin ical practice.