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Complexities of radiation in medical nuclear technology

How Nuclear Recoil Damages DNA  – Technology Review, 1 August 11, The recoil of a nucleus during radioactive decay can do more damage than the alpha particle it emits, according to a new study. Thorium-232 is a silvery, radioactive metal that is particularly good at absorbing X-rays. In the early days of X-ray imaging, doctors routinely injected patients with thorium dioxide because it produced high contrast images. Between the 1930s to the 1950s, some 10 million people received these doses…..

What doctors didn’t appreciate at the time were the long term effects on the body. Once injected, Thorotrast settles in various organs where it tends to stay. The biological half life of the stuff is 22 years.

When thorium eventually decays it sets in train a sequence of five further decays producing alpha particles. These all happen relatively quickly; four of them in a matter of hours or fractions of a second.

For that reason, Thorotrast turned out to be highly carcinogenic but often on a timescale measured in decades. It was eventually withdrawn as a contrast agent in the 1950s.

The problem for physicists is to calculate the effects of elements like thorium on the body. They’ve long known that the high energy particles released during a decay damage the body by smashing into and damaging molecules like DNA.

But today, Evandro Lodi Rizzini and pals at the University of Brescia in Italy say that physicists have missed another mechanism that may cause even more damage………the damage from a recoiling nucleus can be one hundred times greater than the damage from an alpha emission.

That could change the way people think about the damage that radioactive decays can do inside the body. Lodi Rizzini promise a more detailed evaluation in the near future…..

How Nuclear Recoil Damages DNA  – Technology Review

August 1, 2011 - Posted by Christina Macpherson | health, Uranium