Mandible-Maxilla and TMJ Overview

Imaging Techniques and Indications

The study of choice for evaluating the mandible and maxilla is thin-section bone algorithm CT and CECT . A standard protocol consists of coverage from the orbits to the hyoid at ≤ 1-mm intervals following contrast administration and postprocessing with both bone and soft tissue algorithm. Axial images should be acquired parallel to the inferior border of the mandible. Acquiring the maxilla and mandible angled separately so as to avoid artifact from dental restorations assists in evaluation of the alveolar ridge and adjacent structures. Multiplanar reformats should be performed in the coronal and sagittal planes. In addition, it is frequently helpful to the referring clinician to reformat in a panoramic view.

MR of the maxillofacial complex is used to assess marrow changes, involvement of the inferior alveolar nerve, and soft tissue involvement of adjacent structures. T1-/T2-weighted and contrast-enhanced images should be acquired from the orbits to the hyoid at 3 mm and ideally should be acquired with high-resolution/small-FOV techniques. As with CT, axial images should be acquired parallel to the inferior border of the mandible. STIR or T2 fat-saturation sequences along with contrast enhancement are sensitive for marrow/nerve changes associated with inflammation or neoplastic involvement.

MR is the tool of choice for evaluating the TMJ. Small surface, circular (3-inch), or TMJ coils are ideally used, although multichannel coils (12 channels or greater) provide adequate signal. Sagittal images are acquired perpendicular to the long axis of the condyle ("corrected sagittal oblique") at 3-mm intervals. T1-weighted or proton density sagittal images are acquired in the closed- and open-mouth positions. Cine images provide the most accurate assessment of condylar rotation and translation and the associated disc function. Sagittal T2-weighted images are acquired to assess for joint effusion. Coronal T1-weighted images in the closed-mouth position are used to assess medial or lateral disc displacements as well as multiplanar views of the condyle. Contrast-enhanced images are generally reserved for the evaluation of synovitis or tumors.

CT imaging of the TMJ is generally reserved for the evaluation of trauma , assessment of bony abnormalities or calcified masses , or joint reconstruction with metallic prosthesis. Thin-section bone algorithm images are acquired at 1-mm intervals from the sella to the hyoid and reformatted in the coronal and sagittal planes.