Comparison of the Stabilization of Tc - 99m HMPAO in Different Salicylate Preparations

Objective: Tc-99m HMPAO (technetium-99m hexamethylpropyleneamine oxime) is most commonly used radiopharmaceuti-cal for evaluation of cerebral cortex function. Because HMPAO is not chemically stable, the labeling process of Tc-99m HMPAO has some limitations. This study was designed to test whether salicyate derivatives can be used as a stabilizer and to determine which derivative is the most useful agent for stabilizing Tc-99m HMPAO used in the labeling process. Materials and Methods: The 3 salicyate derivatives such as sodium salicylate, salicylic acid, and gentisic acid were used as stabilizers in this study. We used the standardized 3-stripe method the perform both purity and stability tests. When the derivative from the experimental groups showing the best results in the in vitro study was determined, then it was used in an in vivo animal study for further imaging efficacy comparison with a control. Results: The group using gentisic acid as the stabilizer showed the most-effective results for preventing HMPAO chemical structure conversion from the lipophilic d,l type to the hydrophilic meso type. The radiochemical purity of labeled Tc-99m HMPAO remained great than 80% approximately 6 hours after labeling. In the in vivo animal study, the brain uptake ratio of the experimental group also increased with time. Conclusions: Gentisic acid as the stabilizer during the labeling of Tc-99m HMPAO has significant clinical benefits. These advantages were confirmed using both in vitro and in vivo studies.