Factors affecting the labeling of human fibrinogen with 99mTc in vitro.

The preparation of [99mTc]fibrinogen is described. The following factors which could affect the quality of this preparation were studied: pH, SnCl2 and protein concentrations, pre- and post-labeling incubation times and labeling temperature. A 90% labeling yield was achieved by incubating fibrinogen with SnCl2 at pH 9.8 for 22 h before adding the TcO-4 solution. The product obtained was stable and was 85% clottable. The x-ray fluorescence technique was employed to measure the amount of bound tin at different times.