MRI for mandibular involvement in squamous cell carcinoma

Buccal carcinoma in our country is ubiquitous due to the widespread habit of tobacco chewing. One determinant of the surgical method is the presence of underlying bone involvment. If the bone is not involved, it may be left alone or a rim resection may be done to achieve the necessary tumor-free margins. If the cortex is involved, a segmental or marginal mandibulectomy is required.

We have been using CT for this purpose for a long time. Adding dental CT with thinner sections and paraxial and panoramic reconstructions helps.

However MRI, especially in the Western countries is now routinely used for all head and neck tumors including buccal carcinomas. The ability of MRI to depict bone involvement has been a bit of a question mark however. There is a new study from Italy published in this month's issue of the Archives of Otolaryngology Head Neck Surgery by Bolzoni A et al that shows that MRI in fact does very well in picking up bone involvement. In the forty-three patients who underwent surgery, MRI missed one patient with bone involvement and overdiagnosed two patients in the retromolar trigone region.

The advantage of MRI is in its ability to pick up marrow involvement, though CT is probably superior in picking up subtle buccal involvement. With the advent of isotropic imaging, CT may still be good enough, though the comforting thought is even we do perform MRI in these patients, it is unlikely that we will be missing bone involvement.

Unfortunately, a contrast enhanced MRI costs at least twice as much as a contrast-enhanced CT, so its routine use is unlikely.