Cone-beam computed tomography to detect erosions of the temporomandibular joint: Effect of field of view and voxel size on diagnostic efficacy and effective dose

Introduction: In this study, we examined the influence of field of view (FOV) and voxel size on the diagnostic efficacy of cone-beam computed tomography (CBCT) scans to detect erosions in the temporomandibular joint (TMJ). Methods: The sample consisted of 16 TMJs containing natural or artificially created erosions and 16 normal TMJs. CBCT scans were obtained with 3 imaging protocols differing in the FOV and the size of the reconstructed voxels. Two oral and maxillofacial radiologists scored the scans for the presence or absence of erosions. Diagnostic efficacies of the 3 imaging protocols were compared by using receiver operating curve analysis. For each TMJ imaging protocol, we used thermoluminescent dosimetry chips to measure the absorbed dose at specific organ and tissue sites. Effective doses for each examination were calculated. Results: Areas under the receiver operating characteristic curves were 0.77 +/- 0.05 for the 6-in FOV, 0.70 +/- 0.08 for the 9-in FOV, and 0.66 +/- 0.05 for the 12-in FOV. The diagnostic efficacy of the 6-in FOV, determined by the area under the curve, was significantly higher than that of the 12-in FOV (P <= 0.05). Effective doses for bilateral TMJ evaluation were 558 mu Sv for the 6-in FOV, 548 mSv for the 9-in FOV, and 916 mSv for the 12-in FOV. Conclusions: The diagnostic efficacy of CBCT scans for the evaluation of erosive changes in the TMJ is highest for the 6-in FOV and lowest for the 12-in FOV. (Am J Orthod Dentofacial Orthop 2011; 140: e25-e30)