OPG (orthopantomogram) is a relatively simple and inexpensive plain radiograph that can provide useful preliminary information regarding mandible involvement and dental status.
CT is the primary modality of imaging in oral cancer and can provide detailed information about the extent of bone involvement (mandible and maxillary alveolus/hard palate), paramandibular disease, extension into infratemporal fossa/pterygoid muscle invasion—information that can impact on patient management.
MR is of great value in assessing deep invasion in case of deeply infiltrating tongue and floor of mouth cancer and thus determine approach (intraoral approach/mandibulotomy) as well as early invasion of mandibular marrow where CT findings may be equivocal.
Both CT and MR (as well as ultrasound in experienced hands) can give a high degree of accuracy in identifying subclinical lymph node involvement in N0 neck and assist the clinician in the decision whether to perform elective neck dissection or not (in early cancers).
PET-CT is the imaging of choice to assess postsurgical/post-CTRT relapse to differentiate recurrence from fibrosis and postsurgical changes.