Whole-Body Counting in Metabolic Studies of ¹³¹I- Labelled Albumin

Abstract

A ring scan whole-body counter with three scintillation detectors in an unshielded room was used in metabolic studies of ¹³¹I-labelled albumin. Due to redistribution of the tracer, the selfabsorption will change during the study. This will compromise the results. It is possible to calculate the change in selfabsorption by comparison of the whole body measurements with the retained activity calculated from the urinary excretion of activity. The selfabsorption was constant after three days. The initial change was assumed to be caused by transfer of the tracer from the intravascular to the extravascular compartment. Initially the selfabsorption was on an average 7.3 per cent higher than subsequently. If the height and weight of the subjects were taken into account it was possible to correct for change in selfabsorption with an accuracy of 1.8 per cent. When corrected wholebody countings are used it is possible to omit urine collections.

Key Words:

• Albumins
• iodine isotopes
• radiometry