99mTc-Sulfur Colloid Egg Preparation

3056 Background: A common practice in Nuclear Medicine is to cook 99m Tc-Sulfur Colloid into eggs in order to bind the colloid to the protein for gastric emptying studies. The package insert does not currently address this practice. This study was performed to show the colloid does bind to the egg protein and remains bound for at least one hour to establish a beyond use date (BUD). Sodium Pertechnetate (99mTc04-) was used as a control to compare the binding efficacy to sulfur colloid. Mayo Clinic’s egg preparation method is prepared by mixing two eggs with 1 mCi of sulfur colloid and scrambled at 160oF with cooking spray. Materials and Methods:99m Tc-Sulfur colloid and free 99mTcO4- were both cooked into eggs for comparison. One mCi ±10% of either 99mTcO4- or sulfur colloid was added to one cracked egg, the solution was mixed and added to the frying pan with cooking spray to cook at 160oF. Each egg was cooked for one minute on each side and then transferred to a plate to cool. Three eggs were prepared using 99mTcO4- and three with sulfur colloid. All six egg preparations sat for one hour at room temperature and were then minced into rice-sized pieces. Each minced egg was put into separate conical vials with 30mL of saline. These vials were inverted for 5 minutes simultaneously to mix and wash the egg pieces with the saline. The saline solution was then removed with a syringe from the remaining solid. A standard coffee filter was used to filter the saline and then the saline was assayed in a dose calibrator to measure free 99mTcO4- or unbound colloid particles from the egg. This step was repeated for each egg preparation. The egg pieces for each preparation were also assayed in a dose calibrator to measure the amount of radioactivity still bound to the egg. The percent of radioactivity bound to the egg, one hour after prep time, was then determined for the 99m Tc-Sulfur Colloid and 99mTcO4- preparations. Results: 99mTc-Sulfur Colloid has higher binding activity after one hour compared to free TcO4-. The results shown below indicate 99mTc-Sulfur Colloid averaged 95% of activity still bound after one hour, whereas TcO4- averaged in the mid 50% range. Table 1: Preparation Parameters Table 2: Percent of Radioactivity Bound to Egg After One Hour Conclusions: From these results, it is concluded that 99mTc-Sulfur Colloid does bind to eggs effectively, and remains bound one hour after preparation time. Pertechnetate (TcO4-) does not bind to the egg as effectively, therefore it was used as a control expecting it to be detected as unbound radioactivity in the saline. For establishing a BUD, this study demonstrates a one hour BUD is acceptable in regards to how well the 99mTc-Sulfur Colloid remains bound to the egg. Food temperature and safety should also be considered when determining a BUD for clinical practice.