Biomedical subjects

R McGeachie

Publications and source records attributed to R McGeachie.

5 recordsLinked to original sources

PubMed1994

Three-dimensional visualization of physiologically based kinetic model outputs.

Outputs from a physiologically based toxicokinetic (PB-TK) model for fish were visualized by mapping time-series data for specific tissues onto a three-dimensional representation of a rainbow trout. The trout representation was generated in stepwise fashion: 1) cross-section images were obtained from an anesthetized fish using a magnetic resonance imaging system, 2) images were processed to classify tissue types and eliminate unnecessary detail. 3) processed images were imported to a visualization software package (Application Visualization System) to create a three-dimensional representation of the fish, encapsulating five volumes corresponding to the liver, kidney, muscle, gastrointestinal tract, and fat, Kinetic data for the disposition of pentachloroethane in trout were generated using a PB-TK model. Model outputs were mapped onto corresponding tissues volumes, representing chemical concentration as color intensity. The workstation software was then used to animate the images, illustration the accumulation of pentachloroethane in each tissue during a continuous branchial (gill) exposure.

Animals↗

PubMed1990

Rapid dynamic CT scanning in primary degenerative dementia and age-matched controls.

Dynamic computed tomography (CT) scanning of the brain was performed in 26 patients with primary degenerative dementia (PDD) and in 15 age-matched controls without evidence of a dementing illness. Changes in CT density values over time were obtained for 16 regions of interest (ROIs) that were carefully chosen to avoid overlap with adjacent cerebrospinal fluid (CSF), sulsi, or bone. CT density washout curves were compared between patients and controls to detect regions where blood brain barrier (BBB) permeability might be increased. Although the patients' washout curves declined more gradually than control curves in 11 of the 14 ROIs with a functioning BBB, in no case did the difference reach statistical significance. Intrarater correlation coefficients indicated good overall reliability in the selection of ROIs.

Aged↗

PubMed1987

Magnetic resonance imaging in the assessment and surgical management of epilepsy and functional neurological disorders.

Magnetic resonance imaging (MRI) offers significant advantages over computerized tomography (CT) and teleradiographic techniques when used for the evaluation and management of epilepsy and functional neurological disorders. Depth recording and radiofrequency electrodes can be more accurately positioned within structures such as the amygdala and hippocampus. The extent of corpus callosum section, lobectomy, topectomy, and radiofrequency stereotactic lesions can now be readily confirmed and related with seizure, neurological, and behavioral outcome. Occult, usually low grade, intraparenchymal neoplasms not visualized on CT scans can be located by MRI and biopsied or excised by MRI stereotactic techniques.

Corpus Callosum↗

PubMed1984

Spontaneous periodic hypothermia.

We studied a patient with spontaneous periodic hypothermia, agenesis of corpus callosum (Shapiro's syndrome), polydipsia polyuria, and hyponatremia. Endocrine evaluation of hypothalamic-pituitary unit, thyroid, adrenals and gonads was normal. Results of a water deprivation test implied primary polydipsia. Four of 10 reported cases of Shapiro's syndrome had abnormalities in water metabolism. In view of the known effects of arginine vasopressin in thermoregulation, the recurrent hypothermia of this syndrome and the abnormalities of water metabolism may have a common pathogenetic mechanism.

Adult↗

PubMed1976

Aberrant left pulmonary artery presenting as a right paratracheal mass in an adult.

Aberrant left pulmonary artery, or pulmonary sling, is a rare variation of the pulmonary vasculature, with only one previous report of the condition being recognized in an adult. In this report a second case recognized de novo in an adult is presented. Both of these adults were evaluated because of right paratracheal masses which required differentiation from pulmonary malignancies. The barium swallow shows a characteristic indentation of the anterior esophageal wall and the lateral tomogram demonstrates absence of the left pulmonary artery from its normal position in the left hilum. The pulmonary arteriogram is diagnostic and allows avoidance of more invasive diagnostic measures.

Airway Obstruction↗