Oral cavity lesions rarely require imaging without clinical suspicion of deep infiltration. Patients with floor of mouth, retromolar gum and endophytic lesions of the tongue are imaged to rule out deeper involvement. Key landmarks are the midline lingual septum, mylohyoid sling, extrinsic muscles and cortical margin of mandible. Although axial images are most familiar, the coronal view is crucial for the above determination. The sagittal view is important to exclude extension of anterior tongue lesions into the root of the tongue base (Figure 3-15). As with surgical margins, the confidence in diagnosing involvement of the intrinsic tongue is limited by the heterogeneous signal of the interlacing muscle and fat. Pre-contrast and fat-suppressed post-contrast views must be carefully matched to improve confidence. Involvement of the extrinsic muscles must also be carefully excluded. Determining T stage by measuring size
Figure 3-7. A, Enhanced axial CT through lower neck. (1) Left common carotid artery (CCA). (2) Recurrent squamous cancer surrounding the CCA. (3) Normal right CCA. (4) Normal right internal jugular vein. B, Nonselective cervical catheter angiogram. (1) Proximal left CCA. (2) Extrinsic compromise of distal left CCA. (3) Normal caliber proximal left internal carotid artery.
may be difficult to determine by any means and any radiographic description must be considered an estimated margin.
Retromolar lesions sit within one of the most asymmetrically shaped structures, the trigone. Furthermore, imaging artifacts most often degrade this area, especially CT. Upward posterior extension along the lateral pterygoid fascia and neurotropic extension along the mandibular segment of the Vth nerve can be clinically silent but should be excluded in all cases.
Buccal mucosal lesions are not usually imaged until they become problematic due to multiple recurrences and limitations to clinical evaluation due to trismus. Submucosal, periosteal and perineural extension is difficult to evaluate and close correlation with the clinical findings is necessary to avoid over- or underestimating disease which becomes difficult to stage given the loss of tissue planes after multiple treatments.
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