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G A Mack

Publications and source records attributed to G A Mack.

3 recordsLinked to original sources

Trends of PCB, hexachlorobenzene, and beta-benzene hexachloride levels in the adipose tissue of the U.S. population.

Results are presented on the levels of selected toxic chemicals in the adipose tissue of the U.S. population. Estimates of baseline levels and time trends are presented for the chemicals beta-benzene hexachloride (beta-BHC), hexachlorobenzene, and polychlorinated biphenyls (PCBs). The statistical analyses are based on chemical data obtained from analysis of tissue specimens collected from a nationally representative sample of autopsied cadavers and surgical patients by EPA's National Human Adipose Tissue Survey during the period 1970 through 1983. The results show that while nearly the entire U.S. population has detectable levels of these chemicals, the actual concentration levels of beta-BHC and PCBs are steadily decreasing and the levels of HCB are remaining fairly constant. Comparisons of levels across demographic subpopulations show that there are some differences in concentration levels across geographic regions, age groups, and race groups.

Adipose Tissue↗

Computer-assisted liver-mass estimation from gamma-camera images.

We have devised a computer-assisted method for objective estimation of liver mass from the right lateral projection of radiocolloid images of the liver. Gamma-camera images were digitized, preprocessed, and stored in computer memory. The definition of liver for area measurement was adaptively determined by means of a Laplacian operator that measures change in radioactivity slope associated with the liver margin. Individual thresholds were calculated for each of 16 subregions. A liver-mass index was derived from a linear regression model correlating the area of the right lateral projection with liver weight at autopsy in 50 patients whose livers weighed between 0.8 to 3.0 Kg. The correlation coefficient found for this method was 0.83 using the equation: Liver Mass [kg] = Area [cm2]/275 [kg/cm2]--0.215 [kg]. Liver-mass estimates using an alternative computer-assisted method or representative manual methods adapted for gamma-camera images showed lower correlation with liver weight at autopsy.

Adult↗