Radioisotopes in medicine : Preparing a technetium-99m generator and determining its efficiency

Medical professionals increasingly rely on the use of radiopharmaceuticals as tools for medical diagnostics and therapy. Technetium-99m is the most widely used radioisotope in nuclear diagnostic imaging. Its short half-life, ease of incorporation into a variety of carrier molecules, low energy gamma emission, and rapid excretion make it ideal for obtaining images of the major internal organs and skeleton of the human body. It is produced in hospitals by using technetium-99m generators, where the parent 99Mo is stored on a chromatographic column, and the daughter 99mTc is eluted as needed. In this laboratory experiment, students prepare a 99mTc generator by placing a solution of 99Mo in transient equilibrium with 99mTc at the head of a small chromatographic column filled with alumina (Al2O3). The daughter is eluted with 0.9% NaCl solution, and the concentrations of parent and daughter in the eluate are measured using gamma spectrometry. These measurements allow the determination of generator efficiency and the generator's compliance with federal limits for 99Mo breakthrough. We recommend that the instructor contact one of the many university research reactors located throughout the United States so that the experiment may be safely carried out at one of these facilities near their home institution.