99mTc-labelled trimethylmonoiodo-IDA: a new radiopharmaceutical for hepatobiliary imaging.

A new radiopharmaceutical, 99mTc-3-iodo-2,4,6-trimethylphenylcarbamoylmethyl iminodiacetic acid (99mTc-trimethylmonoiodo-IDA) was prepared and evaluated for hepatobiliary scintigraphy. The new agent has less plasma protein binding capacity and greater lipophilicity as compared to that of di-isopropyl-IDA. Hepatobiliary specificity, a short transit time and a high gall bladder-to-liver ratio of the new agent were evident from tissue distribution data in mice. Blood tmax and clearance t1/2 of the radiopharmaceutical were observed at 2 and 3.5 min respectively. The hepatic peak-time tmax (5 min) and release time t1/2 (12.75 min) and release t1/2 (25.00 min) suggest the suitability of this agent for hepatobiliary imaging. Results of hepatobiliary scintigraphy in rabbits have further confirmed the above view.