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07 January 2009

Answer to Question #2965 Submitted to "Ask the Experts"

Category: Radiation Effects — Effects on Tissues and Organs

The following question was answered by an expert in the appropriate field:

I am a radiographer and am exposed to scatter radiation during some procedures. In school I was taught that brain cells are pretty much radioresistant. But doses at therapy levels can cause brain cell damage. To research this more, I looked through a book called Radiation Injury to the Nervous System, which was published in 1991. From what I could gather, the damage that happened to the neurons was secondary to vascular or supporting (glial) cell damage. Does this theory still hold true in light of new research? Have there been studies that isolate neurons to see the direct effect of radiation on them? Finally, is there any new evidence that the scatter radiation I am exposed to could result in any neurons being killed directly or indirectly?

A

You are correct in that neurons are very resistant to lethal radiation damage. The theory that injury to the CNS (central nervous system) is secondary to vascular and connective tissue damage remains widely accepted. We are not certain of the precise mechanism of lethal CNS injury. In any event, very large doses are required in this type of injury—such as those administered in radiotherapy. As you know, millions (perhaps billions) of diagnostic procedures have been done with direct exposure of the brain. There are no reports of lethal injury. There are also no reports of any brain injury from occupational exposure, even from years ago when doses were much greater than they are now.

Conclusion: There is negligible (probably no) risk of brain injury from occupational exposures that do not exceed the current limit. The National Council on Radiation Protection and Measurements has established a cumulative occupational dose limit of 10 mSv (1 rem) per year, with a maximum of 50 mSv in any one year.

S. Julian Gibbs, PhD, DDS

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