Fibro-osseous, osseous, and cartilaginous lesions of the orbit and paraorbital region. Correlative clinicopathologic and radiographic features, including the diagnostic role of CT and MR imaging.

Fibro-osseous and cartilaginous lesions of the orbit and facial region share overlapping clinical, radiologic, and pathologic features that may lead to diagnostic confusion and possible misdiagnosis. The value of imaging studies in the histopathologic diagnosis of these lesions cannot be overemphasized. The histopathologic diagnosis of such lesions should not be rendered in the absence of radiographic correlation.

Temporomandibular joint: role of direct sagittal CT air-contrast arthrogram and MRI.

Direct sagittal CT air-contrast arthrography can provide useful diagnostic information in the evaluation of disorders of the temporomandibular joint. The technique for the performance of this examination is practical and efficient, using a specifically designed head-holder, which is described. This technique effectively complements the clinical and imaging work-up of jaw dysfunction.

Effect of interference of metallic objects on interpretation of T1-weighted magnetic resonance images in the maxillofacial region.

PURPOSE: Metallic objects produce artifacts on magnetic resonance (MR) images. However, studies on typical dental materials in this area are scant. This study was conducted to describe and measure the magnitude of such artifacts. MATERIALS AND METHODS: Samples of various dental materials (dental gold, amalgam, stainless steel, titanium, silver-palladium, and vitallium) were embedded in bovine muscle and then subjected to T1-weighted MR imaging. The materials were of the typical morphology and composition encountered in routine maxillofacial practice. The MR artifacts were measured and compared with the original specimen measurements. RESULTS: All metallic objects were found to produce artifacts and to interfere with the interpretation of MR images. Artifacts were most pronounced in the central plane of the object. Gold produced the greatest artifact, and amalgam produced the least. CONCLUSION: Because metals commonly used in the maxillofacial region all produce artifacts on MR images, avoidance measures should be used to minimize the effect of these artifacts.

The role of magnetic resonance imaging in the diagnosis and management of ameloblastoma.

Magnetic resonance (MR) images of ameloblastoma are compared with computed tomographic (CT) images with the use of three parameters: artifact degradation, edge definition, and conspicuity. As a basis for comparison, MR imaging characterization of normal tissues is reviewed. The three cases studied demonstrate the importance of weighing heavily on MR for evaluation of tumor-normal tissue interface. MR generally proved to be superior to CT in the evaluation of recurrent disease because of its ability to differentiate tissues on the basis of their proton composition. CT images reflect the electron densities of tissues. Hence, interpreting inflammatory and postsurgical changes and differentiating them from neoplasm may be difficult. At the present time, familiarity with CT dictates that the MR evaluation complement and not substitute the CT evaluation.

CT evaluation of TMJ disc replacement with a Proplast-Teflon laminate.

A series of 12 temporomandibular joints treated by discectomy and replacement with Proplast nonporous Teflon laminates were examined retrospectively using direct sagittal and coronal computed tomography. Radiographic findings included severe condylar, glenoid fossa, and eminence remodeling changes; implant migration and fragmentation; and loss of implant adaptation to the temporal bone. The radiographic changes generally occurred in patients who were completely asymptomatic clinically.

Quantitative and qualitative fat analysis in human leg muscle of neuromuscular diseases by 1H MR spectroscopy in vivo.

1H MR spectra were recorded from human gastrocnemius muscle at 63.86 MHz using the body coil of the Signa scanner as transmitter and a 3-in. surface coil as receiver. The fat content of the muscle was quantified relative to that of water in a selected volume or slice. The fat/water ratio was 0.05-0.07 for normal muscle but increased to 0.5-6.0 in primary and secondary muscular disorders such as Duchenne and myotonic dystrophy, Charcot-Marie-Tooth and polio muscular atrophy, cerebral palsy, and spina bifida. In Werdnig-Hoffmann spinal atrophy the ratio was above 10. Water-suppressed and slice-selective 1H spectroscopy was used for qualitative analysis of fat. The 1H profile of gastrocnemius muscles between healthy individuals and patients with neuromuscular diseases showed two major differences. In the normal muscle spectra, the resonance from the -(CH2)n- protons at 1.6 ppm was the most pronounced, whereas in the diseased muscle spectra resonances also appeared between 1.1 and 1.4 ppm. Some diseased muscle spectra showed multiple resonances from -CH = CH- in polyunsaturated fatty acids between 5.5 and 7.0 ppm. The corresponding resonances from = CH-CH2-, 1.9-2.0 ppm, and = CH-CH2-CH =, 2.7-2.9 ppm, were also seen. These peaks are usually not detected in normal muscle.