Cross-sectional analysis of CBF values was carried out among 668 volunteers and patients. Subjects were subdivided according to age, gender, and degree of cerebrovascular disease, ranging from healthy volunteers with or without risk factors for stroke to patients with multi-infarct dementia. Four-year longitudinal analysis was also carried out on 230 individuals from the original sample. Decrements in CBF values were evidenced by both cross-sectional and longitudinal analysis in relation to advancing age, progressive cerebrovascular disease, and dementia. Regional, age-related CBF declines in healthy volunteers were heterogeneous, possibly related to changes in levels of functional activity within different brain regions.
SUMMARY Non-invasive methods are described for estimating local cerebral blood flows (LCBF) and partition coefficients (LX) during inhalation of 35% stable xenon gas (Xe*) in oxygen during CT scanning. After denitrogenatioD by 100% oxygen breathing, 35% Xe* is breathed for 7-8 minutes to minimize subanestbetic effects. Mean changes in brain Hounsfleld units extrapolated to 15 minutes were 7.7 units for white matter and S3 units for gray matter. They were measured from volumes 80 cubic mm (10 mm* area X 8 mm), or larger with an EMI 1010 scanner at 1 minute intervals. These data were used for computing LCBFs and LXs. Irradiation measured at the center of brain slices was 1 rad per minute. To calculate LXs about 6 exposures are necessary, thereafter, each 1 minute scan provides LCBF measurements for 2 adjacent 8 mm slices.
Neurotoxic effects of habitual alcohol consumption were investigated by correlating the subjects' estimates of abstinence or frequency and amount of alcohol consumed with measurements of gray matter blood flow utilizing the 133Xe inhalation method. Two hundred and twenty-two subjects were studied, including 136 healthy subjects, 82 subjects with well-established risk factors for stroke (hypertension, hyperlipidemia, heart disease, and diabetes mellitus), and four subjects with chronic alcoholic dementia of the Wernicke-Korsakoff type. Subjects were classified according to average quantitative amounts of alcohol consumed per day, week, or month for the past five years. Comparisons of mean values for hemispheric gray matter blood flow indicated significant inverse relationships with the average amounts of alcohol consumed. This linear relationship occurred regardless of whether or not other risk factors were present and indicated that alcohol itself was a risk factor reducing gray matter blood flow and had additive effects of reducing cerebral blood flow further when combined with other risk factors. Patients who had chronic Wernicke-Korsakoff syndrome had the most severely reduced blood flow levels, as might be predicted from extrapolation of the regression line comparing cerebral blood flow values with the degree of chronic alcohol consumption.
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