A variety of lesions may occur in the jugular foramen, arising from the structures normally found within the jugular foramen or from contiguous structures. The most common jugular foramen lesions are nontumoral pseudolesions (eg, asymmetrically enlarged jugular foramen, high or protruding jugular bulb) and tumors (eg, paraganglioma, metastasis). In nontumoral pseudolesions, computed tomography (CT) demonstrates smooth, intact margins of the jugular foramen. Turbulent or slow flow in a high or protruding jugular bulb can result in loss of the flow void and contrast enhancement at magnetic resonance (MR) imaging, thereby mimicking real disease. Use of flow-sensitive techniques or MR angiography will help clarify confusing cases. In cerebral venous thrombosis, CT findings are often normal. At conventional MR imaging, flow-related enhancement and in-plane, turbulent, or slow flow can cause loss of the flow void and thus mimic thrombosis. Consequently, phase-contrast MR venography is the imaging modality of choice in the assessment of cerebral venous thrombosis. Most tumoral lesions of the jugular foramen manifest at CT as areas of infiltrative bone destruction, although schwannoma and meningioma cause smooth enlargement of the jugular foramen. In addition, most of these tumors have low to intermediate signal intensity on T1-weighted MR images and intermediate to high signal intensity on T2-weighted MR images and enhance strongly after the administration of contrast material. Careful analysis of these imaging features and correlation with clinical manifestations can allow a more specific diagnosis.
Temporal bone: comparison of isotropic helical CT and conventional direct axial and coronal CT.K S Caldemeyer, K Sandrasegaran, C N Shinaver, V P Mathews, R R Smith and K K KopeckyAudio Available | Share
During the 1980s the United States Federal Aviation Administration developed the thermal neutron analysis (TNA) automated explosive detection system for screening luggage taken aboard commercial air carriers. Six airport systems combining TNA and x-ray were built and deployed under a variety of conditions. This is an unclassified review of the deployment and the difficulties encountered when a system using a nuclear method to detect explosives is put into the field. The mechanical system, radiation safety, use of accelerators, system calibration, simulated explosives, types of luggage, and the test and evaluation procedures are reviewed.
PURPOSE: To evaluate for an association between familial hypophosphatemic rickets (FHR) and Chiari I malformation (CM1). MATERIALS AND METHODS: Sixteen patients with FHR underwent magnetic resonance (MR) imaging of the cervicomedullary junction. Images were analyzed by three radiologists for cerebellar tonsillar ectopia, syringohydromyelia, calvarial bone thickening, a flat posterior fossa, and cervical spinal stenosis. Final diagnoses were made by means of consensus. Tonsillar ectopia of 4 mm indicated CM1. Subjects underwent neurologic examination and completed a questionnaire. Medical records were retrospectively reviewed. A two-sided Fisher exact test was used to test for independence between CM1 and bone thickening or ventriculomegaly. RESULTS: Seven subjects (44%) had CM1. The more severe the bone thickening, the more likely that a CM1 was present. Four subjects (25%) had cervical spinal stenosis. CONCLUSION: Findings indicate that CM1 is associated with FHR and that the primary abnormality in patients with CM1 is a small posterior fossa caused by a bony malformation.
A prototype millimeter wave holographic surveillance system has been developed and demonstrated at the Pacific Northwest Laboratory (PNL). The prototype millimeter wave holographic surveillance system developed at PNL consists of a sequentially switched 2 X 64 element array coupled to a 35 GHz bi-static transceiver. The sequentially switched array of antennas can be used to obtain the holographic data at high speed by electronically sequencing the antennas along one dimension and performing a mechanical scan along the other dimension. A 1D mechanical scan can be performed in about one second. The prototype system scans an aperture of 0.75 by 2.05 m. This system has been demonstrated and images have been obtained on volunteers at Sea-Tac International airport in Seattle, Washington.
