Imaging Studies For TMJ Evaluation
Lateral Cephalometric Radiograph
A radiograph of the head in profile taken with precise reproducible relationships between the radiograph machine, the patient, and the film. Typically the distance between the machine and the patient is 150cm and the distance between the patient and the film is 12cm. This precise and reproducible technique allows accurate measurements to be compared to accepted standards as well as to previous radiographs taken on the same machine.
A unique radiograph providing a complete uninterrupted view of the upper and lower jaws, teeth, facial bones, TMJ (jaw joints), and parts of the maxillary sinus and nasal complexes. Used for general evaluation of all of the visible structures.
Cone-Beam CT Scan
Essentially, this is a 3-D CT scan of the jaws, which allows the surgeon to view facial bones, soft tissues and teeth in three dimensions. It provides a more accurate view and detailed anatomy of the face not possible with a standard radiograph. The scan itself takes 12–18 seconds and is similar to other types of dental x-rays. You do not need to be lying flat and there is no discomfort from the scan. This is the gold standard of facial imaging to evaluate bones, teeth and other detailed anatomy. Because it is focused on a small area, the radiation exposure is much less than a standard CT scan.
Magnetic resonance imaging (MRI) is a noninvasive imaging study that produces detailed pictures of soft tissues, bones, and virtually all other internal body structures. An MRI uses a powerful magnetic field, radio frequency pulses, and a computer to produce the images, not radiation. Typically an MRI is used to provide information about the soft tissues of the TMJ (jaw joints) that cannot be obtained with other imaging methods such as an x-ray or cone-beam CT scan.
A bone scan is a nuclear scanning test that identifies active areas of bone growth and breakdown. It is typically used by jaw surgeons to determine if the jaws are still growing prior to performing surgery. A radioactive tracer is injected into a vein in the arm, the tracer then travels through the bloodstream and into the bones. This process may take several hours. A special gamma camera takes pictures of the tracer in the bones. This shows cell activity and function within the bones. Areas of bone growth absorb increased amounts of the tracer and show up as bright or “hot” spots in the images. Hot spots indicate bone activity related to active growth as well as arthritis, tumor, fracture, and infection.