Louis T. Kircos

Magnetic resonance imaging of the TMJ disc in asymptomatic volunteers

Forty-two temporomandibular joints (TMJs) in 21 asymptomatic volunteers were visualized by magnetic resonance imaging (MRI). The subjects, 12 males and nine females, were between 23 and 43 years of age and had no history of TMJ pain, joint noise, limited opening, or previous treatment for TMJ disorder. A cephalometric head-holder was designed to position the TMJ in an accurate and reproducible manner and multisection parasagittal images were obtained perpendicular to the longitudinal axis of the condyle. MR images depicted anterior disc position in 32% of the asymptomatic joints (8/24 males, 5/18 females). Anterior disc position in asymptomatic subjects may be a predisposing factor to TMJ dysfunction or simply an anatomic variant whose prevalence must be considered when evaluating TMJ dysfunction.

Emission imaging of patients with craniomandibular dysfunction.

Signs and symptoms of craniomandibular dysfunction in 37 patients were compared with the results of corrected cephalometric tomography and an emission imaging protocol consisting of both planar and single photon emission computed tomography (SPECT) (7500 ZLC Orbiter) images. The planar images and the single photon emission computed tomography projection views were processed with a bayesian deblurring algorithm to improve image quality. The correlation of emission imaging with craniomandibular dysfunction, as indicated by temporomandibular joint pain and joint noise, showed a high sensitivity (93%) and a high specificity (86%), whereas the correlation of corrected cephalometric tomography with temporomandibular joint pain and joint noise showed a relatively high sensitivity (89%) but a low specificity (27%). These results indicate that emission imaging is a sensitive and accurate indicator of craniomandibular dysfunction.

Bayesean-deblurred Planar and SPECT nuclear bone imaging for the demonstration of facial anatomy and craniomandibular disorders

Ambiguities in diagnoses can often be resolved when images from different imaging modalities are compared, and when images are processed with algorithms that improve resolution and contrast. Bayesean deblurring algorithms were developed and applied to Planar and SPECT images of the maxillofacial and temporomandibular joint regions. The combined use of Planar and SPECT imaging with Bayesean deblurring were complementary and provided more diagnostic information than either modality individually. A facial imaging protocol using Planar and SPECT imaging and Bayesean deblurring is described. SPECT maxillofacial anatomy is presented, as well as the application of the imaging protocol of craniomandibular dysfunction. Although not recommended for all patients with craniomandibular disorders, combined use of Planar and SPECT images and Bayesean deblurring techniques appears to be useful in diagnostically difficult or refractory cases.

A BAYESEAN PRE-PROCESSOR FOR SPECT: APPLICATION TO IMAGING THE FACIAL SKELETON

The standard algorithm used for SPECT reconstruction requires, as in x-ray CT, the selection of a one-dimensional window function. But one-dimensional filtering of the rotation views is inappropriate in SPECT where the “footprint” of the camera-collimator point spread function (PSF) is large compared to the desired SPECT section thickness. A Bayesean deblurring algorithm which has previously been shown to offer improved contrast and resolution in planar images is now being used to ameliorate the problems presented by this large PSF by pre-processing the rotation views two-dimensionally to remove some of the blurring caused by the collimator. After pre-processing, a ramp filter with the cut-off frequency at the Nyquist level may be used for the reconstruction giving improved resolution and contrast over SPECT images without Bayesean processing and using conventional window functions. This algorithm has been successfully applied to the problem of imaging the facial skeleton. A series of normal patients and those with craniomandibular disorders of unknown origin were imaged using 20 mCi Tc-99m MDP. TMJ arthropathy involving either the glenoid fossa or the mandibular condyle, orthopedic changes involving the mandible or maxilla, localized dental pathosis, as well as changes in structures peripheral to the facial skeleton were identified. Bayesean pre-processed SPECT depicted the facial skeleton more clearly as well as providing a more obvious demonstration of the bony changes associated with craniomandibular disorders than SPECT without pre-processing.