Subtraction radiography for the diagnosis of periapical bone lesions

Abstract Subtraction and conventional radiography were evaluated for the diagnostic potential to assess periapical bone lesions. The periapical region of dry human mandibles was radio-graphically examined, subjectively evaluated and measured by ¹²⁵I absorptiometry before and after the creation of bone defects. Both conventional radiographs and subtraction images made from the conventional radiographs after digitization were interpreted by 10 dentists. Receiver operating characteristic (ROC) analysis technique was used to compare the two techniques. There was a higher diagnostic accuracy using subtraction technique. For a lesion depth corresponding to < 2 mm of compact bone, there was a clear difference between the techniques, but for deeper lesions the conventional technique gained force. The subtraction technique was significantly superior for lesions confined to cancellous bone. The statistical difference in the diagnostic utility of subtraction compared with conventional technique was found to be less for lesions of the cortical bone. Therefore, the conclusion is that subtraction radiography improves the detection of small lesions in the periapical bone area.