Re: What radiologists don't tell you (CT scans)

From: David Rind (drind_at_caregroup.harvard.edu)
Date: 11/28/04 

Date: Sun, 28 Nov 2004 12:20:28 -0500

john wrote:
> This is probably just as well because new data reveals that the patient who
> undergoes a full-body CT (computed tomography) scan is being exposed to a
> radiation level equivalent to that from the atomic bombs dropped on
> Hiroshima and Nagasaki.

I don't usually bother replying to John's posts, but this one is sort of
  funny. There was no new research that radiation from a full-body CT is
equivalent to that from an atomic bomb. (Could anyone really believe
that such a statement was true??).

Someone published a study that attempted to predict the long-term
radiation effects of full-body CT by comparing the radiation levels to
the lowest levels seen in atomic bomb survivors and for whom the authors
had long-term cancer risk data. Note that this is rather different from
suggesting that getting a full-body CT gets you exposed to similar
levels of radiation to what you could expect if you had an atom bomb
dropped on you.

What they calculated was that if you started getting yearly full body
CTs at age 45 and continued for 30 years you would have about a 2%
increased risk of cancer. It's not an enormous risk, and it's not clear
how accurate their estimates were, but since using full-body CT scans
for screening has never been shown to be of benefit it's worth keeping
in mind that additionally they may cause cancer. This has almost no
relevance to the more common situation of someone getting a diagnostic CT. 

-- 
David Rind
drind@caregroup.harvard.edu