Comparative evaluation of incorporated activity by four different whole body counters

The assessment of internal radiation exposure requires the determination of the activity of incorporated radioactive substances and the knowledge of their biokinetic behaviour. If possible, the total body activity should be determined by direct measurements applying whole body or partial body counting. Thereby, serious problems can arise from differences in body size and shape, as well as from variations in the distribution of radioactivity within the subject. To overcome these problems, careful calibration of whole body counters is necessary. Long term reproducibility of the calibration may be achieved by regular measurements of phantoms or activity sources in standard position. The accuracy of determinations of activity can only be realized by intercomparisons with the results obtained with other such devices. Several intercomparisons among whole body counters showed that improper calibration may result in errors of estimated body activities of up to a factor of two or even more. With respect to the variations in the fall out of fission products from the Chernobyl accident, consistency of total body measurements throughout Europe for the estimation of the consequences due to ingestion of radioisotopes is required. The present study was aimed to compare the results obtained by four different whole body counters in Budapest/Hungary, Seibersdorf/Austria, and Frankfurt/ Germany