Comparison of CT, low-field-strength MR imaging, and high-field-strength MR imaging. Work in progress.

To assess objectively the sensitivity and specificity of low-field-strength (0.064 T) magnetic resonance (MR) imaging, a prospective blind study of 280 examinations was performed to compare low-field-strength MR imaging with computed tomography (CT) and with high-field-strength (1.5-T) MR imaging of the cranium. The sensitivity (defined as the true-positive rate) with high-field MR imaging was superior to that with low-field MR imaging and CT in helping detect overall abnormalities. Sensitivities were generally similar over a broad range of specific cranial central nervous system diseases. Low-field and high-field MR imaging were equivalent in the blind diagnoses of neoplasms and white matter disease, whereas low-field MR and CT were equivalent in the blind diagnoses of contusion, subdural and epidural hematoma, sinus disease, normality, and abnormality. The specificities with low-field MR imaging and CT were substantially better than those with high-field MR imaging.

High-resolution, cross-sectional computed tomography of the normal spine.

CT has proved to be an excellent method of studying the spine in cross section. The osseous axial skeleton may be imaged without the need for contrast media. Analysis of the contents of the spinal canal requires administration of intrathecal contrast material, except in the lumbar region, where epidural fat serves as a natural contrast agent. This article illustrates and discusses normal axial CT anatomy of the spine.

Applications of computed tomographic scanning of the cervical spine.

Computed tomography is an extremely valuable adjunct to the evaluation of the cervical spine and spinal cord. When combined with intrathecal metrizamide enhancement and with computer reformatted images in sagittal and coronal planes, CT is a thorough diagnostic modality that can be applied to congenital/developmental, degenerative, and trauma-induced abnormalities. Its major deficiency is the potential to miss defects that are oriented in the transverse plane because of partial volume averaging of adjacent surrounding bone. CT scanning of the cervical spine has been used sparingly to date, probably because available scanners are used for higher-priority demands. However, anecdotal information in the literature document the value of CT in evaluations of the cervical spine, intervertebral disks, neural foramina, and spinal cord. In the future, magnetic resonance scanners may shift some of the imaging burden away from x-ray CT. More widespread use of CT for evaluation of cervical radiculopathies and myelopathy may then occur.

Paragangliomas of the temporal bone: high-resolution CT studies.

Seventeen patients with 15 surgically proved paragangliomas involving the temporal bone and parapharyngeal spaces were examined with high-resolution computed tomography (CT). Scans were obtained in multiple axial (0 degree, 30 degrees) and coronal (70 degrees, 105 degrees) section planes using 1.5-mm collimation and table incrementation. The purpose of this study was to demonstrate the utility of HRCT in assessing tumor extent and size, with particular emphasis on intrinsic temporal bone invasion. The most characteristic HRCT signs of paraganglioma include: jugular fossa expansion, soft-tissue mass in the hypotympanum and sinus tympani, permeation of the infracochlear surface, dural ballooning adjacent to the jugular fossa (indicative of epidural tumor), anterior displacement of parapharyngeal fat planes, and extension into the proximal aspect of the eustachian canal. It is concluded that HRCT is the single most efficacious examination to determine tumor extent, especially when intratemporal invasion has occurred, and to define other additional clinically unsuspected lesions.

Computerized tomography of a sellar spine. Case report.

A presumed developmental variant of the dorsum sellae was found in a patient undergoing evaluation for a suspected pituitary adenoma. An initial computerized tomography (CT) scan suggested a suprasellar mass; however, high-resolution CT with reformations clearly revealed the mass to be the pituitary gland, which was deformed and displaced upward by an osseous spine projecting from the dorsum sellae. The radiographic appearance and etiology of this anomaly are discussed. Neurosurgeons and neuroradiologists should be aware of this anomaly when evaluating a patient for pituitary adenoma.

Multiplanar metrizamide-enhanced CT imaging of the foramen magnum.

Definition of masses and malformations at the foramen magnum has been less than optimal with traditional radiographic techniques. The use of intrathecal metrizamide with computed tomographic (CT) scanning improves contrast resolution and facilitates detection of abnormalities that may not be apparent on Pantopaque cisternography, plain films, or conventional axial CT alone. Fifty patients with clinically suspected foramen-magnum lesions were evaluated with this technique. Forty were abnormal with the following findings: 14 cases of the Chiari malformation (five cases had associated syringomyelia), five meningiomas, three neuromas, a chondrosarcoma, a chordoma, and five cervical and three brainstem gliomas. Six cases of syringomyelia, a large posterior-fossa subarachnoid cyst, and an anomaly of the cisterna magna were also diagnosed. Sagittal and coronal images were beneficial in defining tonsillar position, configuration of the fourth ventricle, and the relations of mass lesions to the spinal canal and subarachnoid space. Metrizamide CT cisternography provides superior spatial and contrast resolution of lesions at the foramen magnum not obtainable with other radiographic techniques. Morbidity is minimal because of the low dose of metrizamide used. Multiplanar reformations are particularly helpful in assessing anatomic detail not readily recognized on axial scans alone.