Gastric Emptying Scintigraphy Egg Radiolabeling Efficiency Pre- and Post-Microwave Cooking

The accuracy and reproducibility of nuclear medicine gastric emptying scintigraphy (GES) require strict adherence to the Society of Nuclear Medicine and Molecular Imaging (SNMMI) standardized protocol. The SNMMI standardized GES protocol contains precise instructions for meal ingredients and preparation. Previous research demonstrated many laboratories were using whole eggs in the test meal as opposed to the guideline-recommended liquid egg white and some laboratories attempted to radiolabel the egg by adding the radiotracer after cooking. This study aimed to document the labeling efficiency of Tc-sulfur colloid (SC) added to whole eggs before and after microwave cooking. Whole eggs were mixed with Tc-SC before and after microwave cooking. The radiolabeling stability of the eggs was tested after 2 and 4 hours of incubation in hydrochloric acid (HCl) and simulated gastric fluid with HCl and pepsin. The experiment showed that no matter what the testing condition, radiolabeling by adding Tc-SC to whole eggs before microwave cooking resulted in a significantly higher labeling efficiency than radiolabeling when the Tc-SC was squirted on eggs after microwave cooking. This finding persisted over time with the pre-cooking radiolabeling method still significantly higher at 2 and 4 hours after the egg was placed for both gastric fluid mediums. Simulated gastric fluid with pepsin at 2 hours, the labeling was significantly higher at 73.3% when the radiotracer was added before microwaving and 43.3% when added after cooking (p