Rapid preparation and quality control method for technetium-99m-2-methoxy isobutyl isonitrile (technetium-99m-sestamibi)

Technetium-99m-2-methoxy isobutyl isonitrile (^99mTc-sestamibi) is a radiopharmaceutical that can be useful in the evaluation of patients with acute myocardial infarction. The current method for preparation requires a lengthy boiling water bath procedure and the recommended quality control procedure is cumbersome and time-consuming. Using a microwave oven, the heating time necessary to provide a labeling efficiency (averaging 97% for sestamibi-labeled with maximum allowable ^99mTc activity and volume has been reduced to 10 sec. A new mini-paper chromatography (MPC) system has been developed to analyze the radiochemical purity of ^99mTc-sestamibi involving a 1:1 chloroform/tetrahydrofuran developing solvent. The recommended thin-layer chromatography (TLC) system involving the use of an Al₂O₃-coated plate requires an average time for drying and development of 34.8 ± 1.6 min (n = 58) to complete, whereas the new MPC system has an average developing time of 2.3 ± 0.1 min (n = 26). For radiochemical purity values ranging from 71-99% (n = 31), the MPC and TLC methods correlated closely (r = 0.99) with a regression line of MPC% = 1.05 TLC% - 5.75. The combined use of the microwave oven heating method and our quick quality control system will facilitate the rapid, emergency use of ^99mTc-sestamibi and eliminate the need for advance preparation of multiple kits each day.