ORIGINAL RESEARCH A Potential Pitfall of MR Imaging for Assessing Mandibular Invasion of Squamous Cell Carcinoma in the Oral Cavity

RESULTS: Twenty-five of 51 patients had histopathologic evidence of mandibular cortical invasion. The tumor involved both the cortex and the bone marrow in all 25 patients and involved the inferior alveolar canal in 5 patients. The sensitivity and specificity for mandibular cortical invasion were 96% and 54% for MR imaging and 100% and 88% for CT, respectively. Those for inferior alveolar canal involvement were 100% and 70% for MR imaging and 100% and 96% for CT, respectively. In both evaluations, the specificity of MR imaging was significantly lower than that of CT (McNemar test, P .004 in the former and P .002 in the latter). Chemical shift artifact by bone marrow fat was postulated to be the source of most false-positive cases on MR imaging findings for mandibular cortical invasion. Those for inferior alveolar canal involvement were due to MR imaging visualization of the tumor and surrounding inflammation with similar signal intensity. CONCLUSION: In assessing the presence and extent of mandibular invasion by squamous cell carcinoma, the specificity of MR imaging was significantly lower than that of CT.