Effect of 99mTc-Sn-colloid incubation time on in vivo distribution

The in vitro particle size of sup(99m)Tc-Sn-colloid preparation increases with the length of incubation time after reconstitution. It was found that the percentage of particles trapped (T) by a 1-μm filter as a function of time (t) could be represented by the logarithmic equation T=5.3+15.7 lnt(r=0.96). This material was applied to a cross-mover study involving 25 patients each of whom received preparations of the same reconstituted sup(99m)Tc-Sn-colloid that had been incubated for 15 min or 5 h. It was found that there was a significant shift of radioactivity to the spleen and a significant decrease in background with the material that had been incubated longer. The sup(99m)Tc-Sn-colloid is adequate for the disclosure of space-occupying disease in the liver and spleen, but unreliable for drawing conclusions on the status of liver function based on the changes in splenic concentration. (orig.)