Assessment of tumour invasion into the mandible: the value of different imaging techniques

In oral carcinomas close to the mandible, tumour invasion of the mandible i s important in selecting segmental or marginal resection. Imaging may play a role in assessing tumour invasion. This study compares the accuracy of pa noramic X-ray, CT and MR imaging in assessing invasion of the mandible in 2 9 patients. At histopathology, 6 patients had mandible erosion, 12 had inva sion and 11 had an intact mandible. Magnetic resonance imaging had the high est sensitivity (94%), but a low specificity (73%), with 3 of 11 intact man dibles interpreted as positive. Furthermore, MR often overestimated the ext ent of tumour invasion. On the other hand, CT panoramic X-ray had a lower s ensitivity (64 and 63%, respectively) and a higher specificity (89 and 90%, respectively). Computed tomography (using 5-mm sections) and panoramic X-r ay had a similar accuracy, and negative findings do not exclude invasion. M agnetic resonance imaging was the most sensitive technique but had more fal se positives and frequently overestimated the extent of tumour invasion. Be cause none of the radiological techniques are accurate enough, clinical exa mination seems at present to remain the most important modality in deciding between segmental and marginal resection. Tumour invasion at CT or panoram ic X-ray is a strong argument for a segmental resection.