Vial retention of technetium-99m sulfur colloid in commercial kits

Vial retention of technetium-99m sulfur colloid in five commercial kits used for the preparation of this radiopharmaceutical was studied. Radiochromatography and microscopic particle sizing were performed on all products; the biologic distribution in rats of two products was tested. Loss of activity attributable to vial retention was evident with only two products. The resulting loss of specific concentration did not affect biologic distribution. The cause of the "plating-out" of the radiopharmaceutical on the interior reaction vial surface was not determined, although the gelatin component of the product was suspected to be a factor.