J. Anim Sci.
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J. Anim Sci. 1979. 49:1458-1463.
© 1979 American Society of Animal Science
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Utilization of Animal Phantoms to Increase the Accuracy of 40K Whole-body Counting1

D. D. Johnson2, L. E. Walters, R. D. Morrison, R. R. Frahm and B. W. Lambert

Oklahoma Agricultural Experiment Station, Stillwater 74074

Abstract

Five phantoms weighing 92.2, 117.5, 145.2, 172.0 and 199.6 kg were developed to determine the influence of weight (mass) and potassium concentration on the detection of potassium by the use of the 40K whole-body counting technique. Two potassium concentrations were studied: a high concentration which approximated the amount of potassium in the body of a very lean heavily muscled pig and a low concentration which approximated the amount of potassium in the body of a fatter, lighter-muscled pig. Phantoms were 40K counted in two replications of four individual counts at each of three instrument counting efficiencies.

Net 40K count increased as phantom weight increased from 92.2 to 199.6 kg, but at a somewhat variable rate. Phantom counting efficiency, which was determined from the known amount of potassium in the phantoms, decreased as mass increased. Reductions in counting efficiency ranged from 3.5 to 9.14% for each increase in phantom weight for the low potassium concentration. Reductions in counting efficiency for the high potassium concentration ranged from 3.2 to 9.38 % for each increase in phantom weight. The response surface constructed from the mean net 40K phantom counts at both potassium concentrations had significant (P<.01) linear and quadratic effects for phantom weight, and significant (P<.01)interaction between concentration linear and phantom weight linear effects. Standard error of estimates from the regression equations at the three instrument counting efficiencies ranged from 1.5 to 2.0% of their respective means. Regression analysis was utilized in order to produce prediction equations to allow for the estimations of potassium in phantoms or animals of different weights.

Footnotes

1 Journal Article No. 3583 of the Oklahoma Agr. Exp. Sta., Oklahoma State Univ., Stillwater 74074.

2 Present address: Dept. of Animal Science, California State Univ., Chico 95926.






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