Cone-beam CT for Assessing Mandibular Invasion by Gingival Carcinoma

Objectives: To evaluate the diagnostic accuracy of cone-beam CT in assessing mandibular invasion of lower gingival carcinoma and compare it with that of panoramic radiography

Methods: Fifty patients with squamous cell carcinoma of the lower gingiva who were examined by both of panoramic radiography and cone-beam CT before surgery were included in this study. As a cone-beam CT apparatus, 3D Accuitomo, image-intensifier type (Morita Corp., Kyoto, Japan) was used. Histopathological diagnosis was determined after marginal or segmental mandibulectomy in all patients. Five oral radiologists used a 6- point rating scale to evaluate independently cone-beam CT and panoramic images with the goal of identifying the presence or absence of alveolar bone and mandibular canal involvement by tumor. Using the histopathogical findings as the gold standard, we calculated and compared the area under the receiver operating characteristic curve (Az value) and the sensitivity and specificity of the two imaging modalities.

Results: In evaluations of both alveolar bone and mandibular canal involvement by tumor, the mean Az value for cone-beam CT (0.918 and 0.977, respectively) was significantly higher than that for panoramic radiography (0.793 and 0.872, respectively). The mean sensitivity for cone-beam CT (89% and 99%, respectively) was significantly higher than that for panoramic radiography (73% and 56%, respectively). There was no significant difference in the mean specificity. While cone-beam CT could provide high resolution three-dimensional images, the image quality around the alveolar crest was often hampered by severe dental artifacts and/or image noise, resulting in difficulties in detecting subtle alveolar invasion by tumor.

Conclusion: Cone-beam CT was significantly superior to panoramic radiography in the evaluation of mandibular invasion by lower gingival carcinoma. Its diagnostic value in detecting subtle alveolar invasion, however, may be limited by severe dental artifacts and image noise.