An Investigation into a Suitable Substitute for Amerscan Hepatate II in Solid Phase Gastric Emptying Studies
Objective
Since the withdrawal of Amerscan Hepatate II from the Australian market it became necessary to find a suitable technetium-based substitute for radiolabelling solid phase meals in Gastric Emptying studies.
Method
Six common, commercially available radiopharmaceuticals, 99mTc-antimony colloid, 99mTc-Hepatate, 99mTc-Sestamibi, 99mTc-pertechnetate, 99mTc-calcium phytate, 99mTc-MAA and in-house prepared 99mTc-rhenium sulphide colloid were investigated. Each radiopharmaceutical was tested by adding to scrambled whole egg and cooking prior to incubation in artificial gastric juice (pepsin, PBS, pH 1.5, 37C) for up to 120 minutes. Radiochemical purity and percentage radiolabel in the liquid phase was determined for each radiopharmaceutical at 5 time points.
Results
Radiochemical purity. The 99mTc-Sestamibi, 99mTc-antimony colloid and 99mTc-rhenium sulphide colloid were found to have < 11% free pertechnetate after 120 minutes incubation.
Artificial Gastric Juice. At 120 minutes, 99mTc-Rhenium sulphide colloid, 99mTc-antimony colloid and 99mTc-Hepatate were found to have < 40% of the label in the liquid phase. However, 99mTcSestamibi, 99mTc-pertechnetate, 99mTc-calcium phytate and 99mTc-MAA were found to have > 40% of the radioactivity present in the liquid phase at 120 minutes incubation.
Conclusion
Both 99mTc-antimony colloid and 99mTc-rhenium sulphide colloid gave similar results for radiochemical purity and distribution in the liquid phase. Either compound could be a suitable substitute for 99mTc-Hepatate as a solid phase marker in gastric emptying studies. 99mTc-calcium phytate, is not suitable due to unacceptably high free 99mTc-pertechnetate in the liquid phase of artificial gastric juice. Of note, 99mTc-rhenium sulphide colloid is recommended by The Society of Nuclear Medicine for solid phase gastric emptying studies.