Absolute quantification of pharmacokinetic distribution of RES colloids in individuals with normal liver function

Estimates of the radiation dose resulting from liver-spleen scintigraphy 99Tcm-labelled colloids are based on pharmacokinetic data mainly determined in animals. The aim of this study was to check the pharmacokinetic data by direct, absolute in vivo quantification in man. For this purpose appropriate methods of measurement were developed, or procedures taken over from literature were modified. Liver and spleen activities were directly measured using a double-energy window technique. Activities in other organs were quantified by conjugate whole-body scans. All measurement procedures were checked using the whole-body Alderson phantom. Pharmacokinetic data for sulphur colloid, tin colloid, human serum albumin (HSA) millimicrospheres, and phytate were obtained in 13 to 20 normal subjects for each type of colloid. Depending on the colloid type liver uptake was between 54 and 75% of the total administered dose (TAD) and spleen uptake was 3.5 to 21% TAD. Activity measured in blood, urine, lung and thyroid proved to be far from negligible. The results of this work suggest a correction of the animal-based data of colloid distribution and radiation dose on the basis of the direct measurement of absolute uptake in man.