Subtraction radiography for the diagnosis of periodontal bone lesions

Subtraction radiography permits reduction of structured noise from sequentially obtained images containing changes of diagnostic interest. It is particularly well suited for the detection of small periodontal changes, because the teeth provide stable bases for standardization of projection geometry from one exposure to the next and because structured noise is prevalent in unprocessed images of the periodontium. Multiple lesions were selectively induced in the tooth-supporting bone of dry mandibles. A significant improvement was unequivocally demonstrated in the visual detectability of the resulting changes after digital subtraction of pre- and postinduction standardized radiographs. The data indicate a significant increase in diagnostic accuracy as a result of the digital subtraction process used in this study. Hence, further application of this technique is warranted in controlled clinical trials.