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Biomedical subjects

A D Gean

Publications and source records attributed to A D Gean.

10 recordsLinked to original sources
PubMed1997

Neuroimaging of AIDS. I. Central nervous system toxoplasmosis.

Toxoplasmosis is the most common cerebral mass lesion encountered in HIV-positive patients. Previously uncommon, this disease has increased markedly since the AIDS epidemic. There are occasionally unusual appearances of central nervous system toxoplasmosis that make diagnosis by standard imaging techniques difficult or impossible. More recently, MR spectroscopy has increased the ability to differentiate between various central nervous system lesions.

AIDS-Related Opportunistic Infections↗
PubMed1996

Intraocular silicone oil for retinal detachment in AIDS: CT and MR appearances.

AIM: To describe the CT and MR features of intraocular silicone oil which is used to treat complex retinal detachments in patients with acquired immune deficiency syndrome (AIDS). PATIENTS AND METHODS: Seven male patients with AIDS were treated by pars plana vitrectomy and intraocular silicone oil injection for complex retinal detachments due to biopsy proven cytomegalovirus retinitis. Two patients had bilateral therapy. RESULTS: Silicone oil was hyperdense to muscle on CT with attenuation values of 106-139 HU (mean 115, SD 4.5). On MR, when compared with normal vitreous, intraocular silicone oil appeared hyperintense on T1-, proton density, and T2-weighted spin-echo sequences. A chemical shift artifact was seen on all MR images, being most marked on the T2-weighted images. CONCLUSION: The high attenuation value of silicone oil on CT and its hyperintensity on T1 weighted MR images my cause diagnostic confusion with haemorrhage. These entities can be distinguished at CT by directly measuring the attenuation number (silicone oil > 100 HU; blood < 90 HU), and at MR by the presence of a chemical shift artifact.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Imaging of acute head injury.

This article reviews the neuroradiological evaluation of acute head injury with an emphasis on CT and MR imaging. Subacute and chronic head injury are not discussed. CT remains the modality of choice in the emergency setting, permitting rapid, comprehensive assessment of the great majority of head injuries. MR is most useful in patients in whom there is a discrepancy between clinical symptoms and CT findings. In addition, MR is the imaging modality of choice in the subacute and chronic setting. The superior contrast resolution of MR permits optimal evaluation of nonhemorrhagic (and hemorrhagic) white matter shearing injuries, and the lack of beam-hardening artifact permits a more thorough evaluation of the brain stem, posterior fossa, and cortical surface.

Acute Disease↗
PubMed1995

Neuroimaging in head injury.

This article reviews the neuroradiologic manifestations of acute nonpenetrating head injury. The pathophysiology of the various types of neurotrauma is correlated with the imaging features. Computed tomography (CT) remains the initial imaging modality of choice, allowing rapid diagnosis of the majority of injuries. Magnetic resonance imaging is useful in the subacute and chronic stages (particularly in a patient whose initial CT scan is unremarkable) to assess brainstem and white matter shearing injuries.

Brain Injuries↗
PubMed1993

Clinical and radiographic findings in disseminated tuberculosis of the brain.

We report clinical and radiographic findings in a patient with disseminated tuberculosis (TB) of the brain. A Burmese man developed a left hemiparesis and mild cognitive difficulty 1 month into therapy for miliary TB. A head MRI showed numerous (> 100) contrast-enhancing supratentorial and infratentorial lesions. Following 9 months of treatment with isoniazid, ethambutol, rifampin, and pyrazinamide, most lesions resolved; however, one cortical tuberculoma enlarged significantly. The patient was continued on isoniazid and rifampin, with radiographic resolution of the tuberculoma 4 months later.

Adult↗
PubMed1989

A pneumatized anterior clinoid mimicking an aneurysm on MR imaging. Report of two cases.

The advent of magnetic resonance (MR) imaging has marked a new era in neuroimaging--particularly in terms of diminishing the need for more invasive diagnostic procedures. A cautionary note should be sounded, however, about an important limitation of standard spin-echo MR studies. Two patients were referred for angiography because MR imaging indicated the presence of a "paraclinoid aneurysm." In retrospect, these findings were due instead to a pneumatized anterior clinoid. Angiography could have been avoided had this pitfall been recognized, and had a gradient-echo flow-imaging protocol been utilized. This latter approach (which does not replace spin-echo imaging) is more sensitive to flowing blood and thus allows differentiation of an air space from a nonthrombosed aneurysm.

Adult↗
PubMed1986

The spinal tap: a new look at an old test.

The spinal tap, or lumbar puncture, has indisputable value; opinions differ, however, on the amount of that value. The procedure has variable utility depending on the clinical indications and the results of tests on the cerebrospinal fluid. Its greatest value is in the evaluation of infectious or malignant meningitis; for most other diseases, it provides additional, but not essential, information. Because of the potential risk of the spinal tap, decisions about when to do the procedure must be made carefully. A probability analysis is provided to elucidate the usefulness of data from cerebrospinal fluid tests.

Bacterial Infections↗