Differential diagnosis between a granuloma and radicular cyst: effectiveness of magnetic resonance imaging.

AIM: To investigate the diagnostic reliability and accuracy of magnetic resonance imaging (MRI) to differentiate periapical lesions of endodontic origin and to compare the results with histopathological information. METHODOLOGY: The radiolucent periapical jaw lesions of 34 patients, which were surgically enucleated, were investigated by two radiologists using MRI, based on the same six criteria, to categorize the lesions as granulomas, radicular cysts or others. After apicoectomies, two oral pathologists (blinded to the radiologist's diagnoses) analysed all specimens by referring to seven specific parameters and diagnosed the specimens as granulomas, radicular cysts or other conditions. The inter-rater agreements between the radiologists and pathologists in terms of MRI and histological diagnoses, respectively, along with the discriminant power of the adopted criteria and the accuracy of the MRI assessments compared with the histopathological results, were calculated. Cohen's kappa test was adopted to examine inter-rater agreement between the two radiologists and two pathologists. Guttman's lambda coefficient (λ6 ) was used to evaluate the internal consistency of the items used for the differential diagnosis by radiologists. The accuracy resulted from a receiver operator characteristic (ROC) analysis. RESULTS: A strong inter-rater reliability was observed between the two radiologists (k-statistic = 0.86, P = 0.0001) and the two pathologists (k-statistic = 0.88, P = 0.0001). The internal consistency of the diagnostic items was 0.605 for cysts and 0.771 for granulomas. The accuracy (true positives plus true negatives) of the radiologists was greater than that of the pathologists based on analysis (area under the curve = 0.87 and 0.91, respectively). CONCLUSIONS: The reliability and accuracy of MRI were high and comparable to histopathological reliability, highlighting the usefulness of this noninvasive technique as a pre-treatment diagnostic method for periapical endodontic lesions.