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DMS expert leads the way in dosimetry

By Kristen Garner

In the event of a nuclear accident, terrorist attack, or nuclear war, thousands or even millions of people could potentially be exposed to dangerous levels of radiation. Measuring radiation exposure in an accurate and timely manner would be critical to managing such a crisis. But that's easier said than done.

It's possible to measure radiation exposure using electron paramagnetic resonance (EPR) in a process that's known as dosimetry. However, current EPR instruments are large and not very mobile. Yet without the ability to easily measure radiation, emergency personnel have no way to determine who's received

One system uses teeth to measure exposure, the other fingernails.

a low dose and doesn't need treatment and who's received a high dose and needs care—until symptoms show up, by which time it may be too late.

For some time, experts have dreamed of having an EPR instrument small enough to carry into the field to triage victims should a nuclear accident or attack take place. Dartmouth researcher Harold Swartz, M.D., Ph.D., an internationally known expert in EPR, is now well on the way to doing just that—developing a

Swartz has been called the "Father of Dosimetry."

portable bio-dosimeter.

Radiation: Swartz described EPR-based bio-dosimetry in a 2007 article for the journal Radiation Measurements. He explained that EPR detects the presence of unpaired electrons, and "ionizing radiation generates large numbers of unpaired electron species. While most of these react immediately and disappear, in some materials . . . the unpaired electrons can persist for long periods." The enamel of teeth is one suchmaterial. In 1968, Swartz published a paper

showing that EPR could determine radiation exposure by taking measurements of teeth. This was a discovery that, he admits with chagrin, has led some in the field to call him the "Father of Dosimetry." Recently, he has shown that fingernails and toenails also have the same property.

Exposure: The development of a portable dosimeter is understandably of great interest to the Department of Defense (DoD). The DoD's research arm—the Defense Advanced Research Projects Agency, or DARPA—supports research "where risk and payoff are both very high." DARPA has funded four contracts to develop dosimetry systems—two of them with Swartz. One is based on using teeth tomeasure exposure, the other on using fingernails and toenails. These contracts are very demanding, according to Swartz. Typical research projects are funded over several years, but the timeline for these is only eight months, plus a month for testing. "It's an impossibly short amount of time," says Swartz.

But with 40 years of experience in the field, he's as likely to succeed as anyone. With the pressure on, Swartz's group has been making great strides on the project. By October, when the contracts are up, portable bio-dosimeters may be not just a dream but a reality.

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