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

Abstract

The in vitro particle size of ^99mTc-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 ln t (r=0.96). This material was applied to acrossmover study involving 25 patients each of whom received preparations of the same reconstituted ^99mTc-Sn-colloid that had been incubated for 15 min and (each patient received both) 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 ^99mTc-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.