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Sat Dec 1 00:56:39 GMT 2007

Is it just me...

I have not been fully convinced by the NEJM article about the 
"supposed" SIGNIFICANT increased risks of malignancy from CT's...

interesting to note that most of the evidence the article cites is 
based on Brenner's work...based an EXTRAPLOATED data from Enola Gay...

just to be provacative...the incidence of peanut allergy also has 
increased since the advent of CT scanning...must be a cause-effect

agree with K...way too many being done in all settings...however let's 
not throw the baby out with....

Joe Lex's puts things into context in his recent article in emedhome:

"Using standard models that assumed a linear extrapolation of risks 
from medium to low doses, they estimated the lifetime cancer mortality 
risks attributable to radiation exposure for an abdominal scan in a 
1-year-old to be 0.18%. In other words, of the approximately 600,000 
children under the age of 15 years who receive an abdominal CT 
annually, about 500 might eventually die from cancer attributable to 
the CT radiation. The authors also recognize that the risk-benefit 
balance is still strongly tilted toward benefit.

On the other hand, two large studies looked at cancer incidence and 
mortality many years after cardiac catheterization procedures in 
children; neither study reported an increase in cancer occurrence at 
remote follow-up years later (2,3). The estimated radiation dose from a 
cardiac catheterization is 200 to 500 mGray (mGy), whereas the 
estimated dose received from a single full-body CT examination in a 
child is 14 ? 21 mGy. The only adverse effects statistically proven at 
the dose levels associated with diagnostic radiation procedures is a 
very small increase in childhood malignancy, with an estimated increase 
of one additional cancer death per 1700 exposures of 10 mGy.

Applying these estimates to adults, Brenner and Elleson determined that 
a single full-body CT examination in a 45-year-old adult would result 
in an estimated lifetime cancer mortality risk of around 0.08% (4). 
They also note that a 45-year-old adult who plans to submit himself to 
annual full-body screening CT examinations up to age 75 (30 
examinations) would amass an overall estimated lifetime risk of cancer 
mortality of about 1.9%, or 1 in 50.

Parents of children receiving diagnostic radiographic studies need to 
know that the potential risk of a 1 year-old developing cancer sometime 
during life after a single CT is about 1 in 500. If this risk appears 
to outweigh the potential benefit, an alternative diagnostic study 
should be sought. In adult patients, the increased risk is minimal ? 
certainly less than one in 1000. The older the patient, the lower the 
lifetime risk, but effects are cumulative over time"

joe

Estimated Organ Doses and Lifetime Cancer Risks from Typical Single CT 
Scans of the Head and the Abdomen.

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NEJM article