Pre-surgical assessment of mandibular bone invasion from oral cancer: comparison between different imaging techniques and relevance of radiologist expertise.

Purpose: To compare diagnostic performance between computed tomography (CT) and magnetic resonance imaging (MRI) for the detection of bone infiltration from oral cancer, and to test interobserver agreement between radiologists with different expertises.
Materials and Methods: Pre-surgical CT and MRI were reviewed independently by two radiologists with different expertises in head and neck oncology. A third radiologist reviewed CT and MRI simultaneously. Interobserver agreement was calculated by Cohen test. Association between radiological evidence of bone infiltration and histological reference was tested by Fisher's exact test or Chi-squared test, as appropriate. Receiving operator curve was calculated and area under the curve (AUC) was compared between CT, MRI, and both methods together.
Results: Interobserver agreement was moderate: the trainee under-reported periosteal reaction on CT and inferior alveolar canal involvement on MRI. Imaging findings associated with histologic evidence of bone infiltration were: periosteal reaction and cortical erosion on CT; bone marrow involvement, contrast enhancement within bone; and inferior alveolar canal involvement on MRI. Sensitivity of MRI alone (74 %) was higher than CT (52 %). Simultaneous review of CT and MRI showed the highest specificity (91 %), with the increase of diagnostic performance in the subgroup of subjects with positive MRI (AUC = 0.689; p = 0.044).
Conclusion: Higher expertise allows pre-surgical detection of clinically relevant signs of bone infiltration sensitivity of MRI alone is higher than CT for the detection of bone infiltration from oral cancer. In MRI positive cases, diagnostic integration with combined review of CT and MRI is suggested for optimal diagnostic performance.