Production of lyophilized albumin macroaggregates and labelling with 99mTc

Optimal conditions of HSA aggregation in acetate buffer (pH = 4.6) were investigated. With the aim of obtaining a higher percentage of fixation in the lungs, the aggregates were rinsed three times with acetate buffer. A MAA suspension was lyophilized with SnCl22H2O (10 microgram/ml) solution. The lyophilized MAA was then labelled by adding pertechnetate of the desired activity in a volume of up to 5 ml. The radiochemical purity of 99mTc-MAA, greater than 95%, was determined by the methods of thin layer chromatography and low-voltage electrophoresis. All MAAs were uniform in shape whereas the size varied between 20 and 100 micrometer. Biodistribution studies have shown the maximum radioactivity to be deposited in the animals' lungs immediately after application of 99mTc-MAA.