Dextrose Solutions Yield Radiochemical Impurities: The "Sweet" Scans

If additional chemicals are inadvertently introduced in the preparation of radiopharmaceutical kits, radiochemical impurities may be formed. We report our experience with erroneously diluting (99m)Tc-pertechnetate eluate with 5% dextrose solution rather than normal saline during the preparation of (99m)Tc-tetrofosmin, (99m)Tc-methylene diphosphonate (MDP), (99m)Tc-stannous colloid, and (99m)Tc-mebrofenin. Scintigrams for 3 of the 4 radiochemicals unintentionally prepared with 5% dextrose were found to have an altered biodistribution. Therefore, radiopharmacy procedures for the day were reviewed, and instant thin-layer chromatography (ITLC) was performed. Scintigrams showed an altered biodistribution consistent with an impurity. Review of procedures that day uncovered the error of using 5% dextrose to dilute the (99m)Tc eluate. The altered biodistribution on (99m)Tc-stannous colloid, (99m)Tc-MDP, and (99m)Tc-mebrofenin scintigrams consisted of cardiac blood-pool activity (possibly as a result of slow clearance of (99m)Tc-dextrose), soft-tissue background activity (possibly as a result of interstitial distribution of (99m)Tc-dextrose), renal and bladder activity (possibly as a result of renal elimination of (99m)Tc-dextrose), and gallbladder activity (possibly as a result of hepatobiliary excretion of (99m)Tc-dextrose). Both scintigrams and ITLC showed no evidence of impurities for the (99m)Tc-tetrofosmin prepared using 5% dextrose. Unintended preparation of radiochemicals with 5% dextrose rather than normal saline often results in the production of impurities, possibly (99m)Tc-dextrose. Because some but not all commercial radiochemical kits prepared with 5% dextrose will suffer this fate, nuclear medicine physicians reviewing the day's images will be confronted with a confusing combination of expected and grossly abnormal findings.