99MTc-HIDA, a gallbladder imaging agent: experimental aspects.

The molecule N-(2,6-dimethyl-phenyl-carbamoyl-methyl)-iminodiacetic acid (HIDA), capable of chelating reduced 99mTc, was synthesized, characterized, labeled with 99mTc, and studied in experimental animals. The results indicated that the new 99mTc-radiopharmaceutical is rapidly cleared from the blood to the liver, then rapidly removed to the gallbladder and excreted into the duodenum through the common bile duct. A comparative kinetic study of 99mTc-HIDA and 131I-Rose Bengal performed in rabbits demonstrated that both radiopharmaceuticals had a similar blood clearance rate, but cleared at a different rate from liver to gallbladder. 99mTc-HIDA showed a faster accumulation in the gallbladder than 131I-Rose Bengal. These findings, combined with the advantage of the low acute toxicity of HIDA, were promising enough to encourage a further evaluation and clinical investigation of this new Tc-99m hepatobiliary agent.