Evaluation of different counting methods for use in radiochemical purity testing procedures for 99mTc-labelled radiopharmaceuticals.

The efficiency and accuracy of different methods for quality control of radiopharmaceutical preparations for diagnostic purpose were studied. The radiochemical purity of (99m)Tc Tetrafosmin, (99m)Tc Exametazime, (99m)Tc Sestamibi and (99m)Tc Oxidronate was evaluated by different thin layer chromatography systems, followed by cutting of the strips into two or three sections and by the measurement of radioactivity distribution by dose calibrator or gamma counter. In addition, to confirm the accuracy of these routine procedures, the strips were cut into a number of micro-sections (14-25) and each of them evaluated by the gamma counter. The three tested procedures gave similar results and revealed a good and comparable accuracy. The radioactivity measurement with the dose calibrator remains the most practicable because of the rapidity of execution.