Biomedical subjects

W T Oravez

Publications and source records attributed to W T Oravez.

5 recordsLinked to original sources

PubMed1989

Hyperperfusion of cerebral cortex, thalamus and basal ganglia during spontaneously occurring migraine headaches.

Color-coded, cross-sectional imaging of local cerebral blood flow (LCBF) was made in a prospective manner among 22 patients with well-established common or classic migraine utilizing the stable xenon-enhanced computed tomographic (Xe CT-CBF) method. LCBF in patients during spontaneously occurring headaches (N = 12) were significantly higher compared to patients without headache (N = 10) by 25-35%. The hyperperfusion involved not only cerebral cortex but also subcortical structures including thalamus, basal ganglia, and subcortical white matter. LCBF increases were not bilateral and sometimes asymmetrical, but LCBF increases were not consistently related to the preponderant side of headache. No significant differences were observed in the degree or pattern of cerebral hyperperfusion during headaches compared among common (N = 6) and classic (N = 6) migraineurs. Results suggest a common etiology for both common and classic migraine. Results are not consistent with spreading oligemia or spreading cortical depression as a cause of migraine. The cerebral hyperperfusion appears to be mediated by various neurogenic and chemical changes accompanying migraine. The unilateral nature of migraine head pain is more likely due to dilation of extracranial vessels.

Adult↗

PubMed1988

Imaging local cerebral blood flow by Xenon-enhanced computed tomography--technical optimization procedures.

Methods are described for non-invasive, computer-assisted serial scanning throughout the human brain during eight minutes of inhalation of 27%-30% Xenon gas in order to measure local cerebral blood flow (LCBF). Optimized Xenon-enhanced computed tomography (XeCT) was achieved by 5-second scanning at one-minute intervals utilizing a state-of-the-art CT scanner and rapid delivery of Xenon gas via a face mask. Values for local brain-blood partition coefficients (L lambda) measured in vivo were utilized to calculate LCBF values. Previous methods assumed L lambda values to be normal, introducing the risk of systematic errors, because L lambda values differ throughout normal brain and may be altered by disease. Color-coded maps of L lambda and LCBF values were formatted directly onto CT images for exact correlation of function with anatomic and pathologic observations (spatial resolution: 26.5 cubic mm). Results were compared among eight normal volunteers, aged between 50 and 88 years. Mean cortical gray matter blood flow was 46.3 +/- 7.7, for subcortical gray matter was 50.3 +/- 13.2 and for white matter was 18.8 +/- 3.2. Modern CT scanners provide stability, improved signal to noise ratio and minimal radiation scatter. Combining these advantages with rapid Xenon saturation of the blood provides correlations of L lambda and LCBF with images of normal and abnormal brain in a safe, useful and non-invasive manner.

Aged↗

PubMed1988

LCBF values decline while L lambda values increase during normal human aging measured by stable xenon-enhanced computed tomography.

Results of measurements of LCBF and L lambda values utilizing optimal CT-CBF methods under resting conditions are reported among thirty-two neurologically normal volunteers aged between 20 and 88 years. Measurements were made during inhalation of 26-30% stable xenon gas for 8 min and serial scanning utilizing a state-of the-art CT scanner with both eyes closed and ears unplugged. LCBF values for cortical gray matter were lowest in occipital cortex and highest in frontal cortex. Gray matter flow values were also high in subcortical structures with highest values measured in the thalamus. For white matter, highest flow values were measured in the internal capsule. Changes in LCBF and L lambda values were analyzed with respect to advancing age. Significant age-related declines in LCBF values were observed in occipital cortex and frontal white matter. Significant age-related increases in L lambda values were measured in frontal and temporal cortex, caudate nucleus and thalamus. Possible explanations are offered for these age-related increases in L lambda values for gray matter, such as accumulation of lipofuscin in neurons and relative compacting of gray matter with advancing age. The latter increases the numbers of nerve cells sampled per volume of gray matter measured.

Administration, Inhalation↗

PubMedDate not supplied

Quantitative evaluation of a dual energy CT system.

We have evaluated the accuracy of CT numbers produced by a prototype dual energy system. Solutions of known composition were scanned in simple cylindrical phantoms and the observed CT values in synthetic monochromatic images were compared with the expected values computed from published cross-section data. Although accuracy varied with both the composition of the solution and the energy selected for the synthetic monoenergetic image, for the solutions used the inaccuracy was less than the uncertainty of the photon cross-section data at 80 and 100 keV. Virtually no cupping artifact was present in the monoenergetic images.

Evaluation Studies as Topic↗

PubMedDate not supplied

Leukoaraiosis: correlation of MR and CT findings with blood flow, atrophy, and cognition.

Hypodense periventricular white-matter lesions detected by CT (leukoaraiosis) and high-intensity T2 signals detected by MR imaging were correlated with measurements of local cerebral blood flow (LCBF), cerebral atrophy, and cognitive performance. Subjects studied included elderly volunteers who were neurologically normal (n = 6), patients with chronic cerebral infarctions and intact cognition (n = 2), patients with multiinfarct dementia (n = 14), and patients with Alzheimer dementia (n = 9). Leukoaraiosis correlated with periventricular high-intensity lesions detected by MR, LCBF reductions, cognitive impairments, and cerebral atrophy. Moderate to severe leukoaraiosis was associated with LCBF reductions in the cortex, basal ganglia, and frontal white matter. Periventricular MR lesions correlated with cerebral atrophy but not with cognitive impairments or reductions in LCBF. The exquisite sensitivity of MR revealed small lesions that did not correlate with LCBF reductions and cognitive impairments. Remote subcortical white-matter lesions detected by MR did not correlate with periventricular MR lesions, leukoaraiosis, LCBF, cerebral atrophy, or cognitive performance, indicating little clinical relevance. We concluded that diffuse cerebral hypoperfusion, particularly in combination with the poor collateral circulation of white matter surrounding the lateral ventricles, is responsible for leukoaraiosis.

Aged↗