Image processing for enhanced observer agreement in the evaluation of periapical bone changes

AIM: The aim of the present study was to evaluate the effect of root canal treatment on periapical lesions by conventional and subtracted digital radiographic images of clinical cases. METHODOLOGY: Eleven patients who exhibited clinical or radiological signs of periapical pathology received root canal treatment. Periapical radiographs were obtained immediately postoperatively and recall radiographs at intervals of 3, 6, 9 and 12 months postoperatively were obtained. Identical exposure geometry was maintained. From the standardized radiographs digitized images were produced. Four experienced practitioners interpreted the radiographs and the digitized images. They assessed 59 pairs of images projected at random using a slide projector. On the left side, there was a reference image with no lesion, and on the right an image either with or without a lesion. Each reader was asked to rate each pair of images on a three-point scale: yes, absolutely sure that gain or loss was present; uncertain, if there was gain or loss; no, absolutely sure that no gain or loss was present. There was no time limit for each decision. Inter- and intra-examiner agreement was analyzed using the kappa-statistic for the diagnosis of periapical bone density changes in the periapical region at the different time points either in conventional pairs of radiographs or using digital subtraction images. RESULTS: The inter-examiner agreement (P < 0.001) and the intra-examiner agreement (P = 0.02) when digital pictures where evaluated were significantly higher than with conventional radiographs. CONCLUSIONS: A highly significantly better observer agreement was achieved by digital subtraction radiography during the evaluation of the outcome of root canal treatment on periapical lesions.