Radiation Dose to Humans from 99m Tc Labeled Dihydrothioctic Acid (DHTA).

摘要

Dihydrothioctic acid (DHTA) is a new 99mTc-labeled hepatobiliary imaging agent for liver/gall bladder visualization and for diagnosing acute cholecystitis. Nineteen patients with normal liver function were denied oral intake of food of drink after midnight and injected intravenously the following morning with 4mCi 99mTc-DHTA, prepared from a commercial kit. Each patient was scanned in a supine position from the mid-thoracic to mid-thigh regions. Scans were performed at various times from 0.25 to 12 hours after DHTA administration; 3 to 10 scans being recorded for each patient. The patients were allowed to eat fatty meals at the normal noon and evening meal times thereby inducing the gall bladder to empty. A dual five-inch rectilinear scanner interfaced to a PDP-8/I computer with 16K of core memory was used for data collection. The biological distribution of 99mTc-DHTA is similar to that of (131)I-sodium rose bengal since it is rapidly cleared from the blood by the polygonal cells of the liver and enters the intestines via the biliary tract with the kidneys excreting a small quantity. This biological distribution complicates determination of the quantitative data in humans necessary for absorbed radiation dose estimates, as evidenced by the lack of published quantitative data for rose bengal. Cumulated activity values for complete elimination of 99mTc-DHTA were determined utilizing a computer program which performs graphic integration of the experimentally determined activity distribution curves.