Evaluation of technetium-99m disofenin by column and instant thin-layer chromatography: demonstration of radiocolloid as a cause for splenic uptake.

We found persistent splenic uptake in 5% of patients undergoing hepatobiliary imaging with Tc-99m Disofenin when administered within a few minutes after labeling, suggesting the presence of radiocolloid. Hydrolyzed reduced Tc-99m colloid (HR-Tc) present in labeled Disofenin kits is controversial and may be dependent on method of assay and radiochemical kinetics. Kits were therefore evaluated by gel column (GCC) and instant thin-layer (ITLC) chromatographic methods. Tc-99m Disofenin was prepared according to the manufacturer's instructions and was maintained at room temperature (23 degrees C) or was incubated at 37 degrees C for 0.5 hr and then held at 23 degrees C. Aliquots were obtained at intervals over 5 hr and applied to Sephadex G-15 resin columns and ITLC-SG strips, with distilled water as mobile phase. GCC showed 14.9% +/- 3.4% and 11.0% +/- 2.9% initial values of HR-Tc at 23 degrees C and 37 degrees C treatments, respectively. HR-Tc decreased over time with each treatment. ITLC showed 1.2% +/- 0.4% and 1.3% +/- 0.2% HR-Tc, with no change over time. ITLC appears to be an insensitive method for the detection of HR-Tc. Incubation of Tc-99m with Disofenin kits for 30 min at 37 degrees C or for 1 hr at 23 degrees C offers an empiric method to ensure HR-Tc levels acceptable for nuclear imaging.