Re: Radiation levels - 64-slice CT vs. new 'dual-source' CT


Joe Doe wrote:
In article <1168132252.668109.211370@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
James216440@xxxxxxxxx wrote:


Your concern about the amount of radiation is a valid concern in the
absence of any understanding. Why expose yourself if it is not
important? On the other hand the risk is so tiny that there is so
close to zero chance of any health problem the reward far out weighs
the tiny risk. After all they will see things besides your heart and
you may even solve some health issue you did not know exists. The big
risk you are running is getting into a traffic accident and getting
killed on the way to the test or on your way home from the test. Of
course you can avoid this risk by never getting in a car again.


The risk was quantified as 7 excess cancer deaths per 10,000 people over
a lifetime from a multi slice CT procedure in one of the links I
provided. I agree this is a small risk. Exposing yourself to a spate
of such procedures however may not make sense. I.e if he has a CT then
has a cath he is doubling his exposure. So the question is he really a
candidate for the CT or a cath based on what his stress test revealed.

Roland

I will accept the 7 excess cancer deaths per 100.000 people over a
lifetime as the official published number. Yet this number is very
misleading. The OP is 48. Thus he has already used about 5/8 of his
lifetime. So the first correction that needs to be made is to correct
for remaining lifetime. This gets it down to about 3 per 100,000.

Next you must consider latency in cancer development. Latency is very,
very important as radiation induced cancers increase with time from
exposure in way more then a linear fashion. As the OP does not have
anyplace close to a full lifetime after exposure you need to adjust
that 3/100,00 down substantially to account for latency.

Then you need to consider how the 7/100,000 was derived to start with.
It was derived by dosing at a very high dose and assuming the dose
response curve is linear. Of course it is very well documented that
the dose reponse curve for radiation induced cancer is not linear.
Rather it has a substantial upwards concavity when you plot dose on the
vertical axis and life time response rate on the horizontal axis. This
dictates the rational person should make an added downward adjustment
to the actual risk estimate. By the way, a linear response is how
virtually all tox data is treated so there is nothing unusual about
this case. And a linear response is known to always be incorrect. But
it is simply too expensive to get the actual data on the shape of the
curve so this highly conservative data treatment is what is standard.

When you make reasonable corrections to the data for the known factors
that make the 7/100,000 incorrect you come up with a real estimated
risk for the OP of no more then 1/100,000 and likely quite a bit lower.

The big risk is not the radiation. The big risk is driving to the
medical center for the test.

.

Relevant Pages

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