Thorotrast

Thorotrast and Umbrathor the trade name for a 1929 introduced into the market X-ray contrast agents, based on a stabilized colloidal suspension of 25% thoria. It was used until his ban mid-1950s, mainly as a contrast agent for angiography. The high atomic number, and the high atomic weight of thorium cause strong absorption of X-rays through this contrast agent. At first applications no immediate side effects in patients could be detected before the launch. Although you knew that thorium is radioactive, but the very long-lived isotope 232Th - natural thorium is 100 percent of this isotope with a half -life of 1.405 · 1010 years - was classified as harmless. This was a fatal mistake, as it turned out to be many years later.

Toxicology

The colloidal thorium dioxide accumulates in the reticuloendothelial system and can lead to cancer there due to locally increased radiation exposure. There are clear associations between Thorotrast and cholangiocarcinoma, as allowing an angiosarcoma or hemangioendothelioma of the liver, otherwise very rare malignant tumors that are induced by Thorotrast. Carcinomas of the paranasal sinuses after the administration of Thorotrast are also described. Typically, the disease occurred in 30 to 35 years after exposure. The biological half-life - the time are excreted to 50 percent of the administered thorium dioxide from the body - is about 400 years.

Application

Usually, the contrast agent was injected intravenously or intraarterially undiluted in amounts of about 25 ml. The case brought into the body amount of thorium was about 5 grams.

Thorotrast in the media

The Danish director Nils Malmros and surgeon has rotated under the German title " Facing the Truth " ( orig. At Kende sandheden, Eng. Facing the Truth ) a biographical film about his father Richard Malmros in 2002. The award-winning film, the dilemma of Malmros is ' father shows either the excellent suitable as contrast agents for diagnostic Thorotrast - to be used with the known him long term side effects - or the only time available alternative ( Per- Abrodil = diethanolamine -3, 5 - diiodpyridon - 4-acetic acid ), which showed significant immediate side effects, a significantly poorer image contrast delivered and was also difficult to obtain in World War II.

Alternatives

Instead of Thorotrast today barium in the stomach and intestinal diagnostics as well as significantly improved aromatic iodo derivatives are used as an intravenous or intra-arterial x-ray contrast agent.