Thorotrast

Thorotrast is a radiopaque contrast agent that was historically used in medical imaging, particularly in the 1920s through the 1950s. It consists of colloidal thorium dioxide (ThO₂) suspended in water, which makes it visible under X-ray imaging due to its high atomic number. The substance was primarily employed for angiographic studies, including cerebral angiography, to visualize blood vessels.

The use of Thorotrast declined significantly after the 1950s due to growing concerns about its safety. Thorium, a radioactive element, decays into radioactive isotopes such as radium-228 and actinium-228, which emit harmful alpha and beta radiation. Prolonged exposure to Thorotrast has been linked to severe health risks, including an increased risk of cancer, particularly liver cancer, bone tumors, and leukemia. Additionally, it has been associated with other complications such as cirrhosis, kidney damage, and neurological disorders.

Thorotrast was banned in most countries by the 1960s, and its use is now considered obsolete in modern medicine. The long-term effects of exposure can persist for decades, as thorium has a half-life of approximately 14.1 billion years, meaning it remains radioactive for an extremely long period. Patients who were exposed to Thorotrast in the past may still face health issues due to its lingering radioactivity.

Today, safer alternatives such as iodinated contrast agents are used in medical imaging, eliminating the risks associated with radioactive materials. Thorotrast serves as a historical example of how medical practices evolve in response to emerging safety concerns.