Confessions of a Quackbuster

This blog deals with healthcare consumer protection, and is therefore about quackery, healthfraud, chiropractic, and other forms of so-Called "Alternative" Medicine (sCAM).

Sunday, June 05, 2005

Ten Lies.....debunked - James R. Laidler, MD

These comments by Dr. Laidler - regarding point number six - are in reply to this nonsense - Ten Lies About Health Your Doctor Taught You

That nonsense is a hodge podge of deliberately misleading strawman arguments. It is simply poor spin doctoring from promoters of so-Called "Alternative" Medicine (sCAM), clearly designed to weaken people's confidence in modern medicine, and thus to get more customers for dubious methods, products and practitioners, such as chiropractors, naturopaths, homeopaths, chelationists, anti-vaccinationists, etc..


>> Lie #6: CT scans (CAT scans) are perfectly safe.
>>
>> Truth #6: CT scans expose patients to 1000 times the radiation
>> of chest X-rays. Repeated exposure to CT scans raises a
>> patient's cumulative radiation to levels experienced by many
>> hydrogen bomb victims in Hiroshima. In addition, rigorous
>> studies have concluded that CT scans offer no medical benefit
>> whatsoever.
>>

*** SNIP ***

You know, it's taken me about 10,000 times as much effort and research to debunk this nonsense as it took the writer to write it (10,000 times the effort, an undefined multiple of research, since the writer's research was apparently zero).

[1] "CT scans (CAT scans) are perfectly safe."

No doctor believes that a CT scan (or anything in this life) is perfectly safe. That is the "straw man" of the argument.

[2] "CT scans expose patients to 1000 times the radiation of chest X-rays."

Let's compare "real" X-ray exposure data:

X-ray exposure from a chest X-ray (PA) = 0.02 mSv
X-ray exposure from a chest CT = 8 mSv

Therefore the CT gives you 400 times (not 1000 times) the radiation of a simple PA chest X-ray. Add in the lateral chest X-ray (at 0.04 mSv) and the ratio drops to 133. Of course, the chest CT gives you a whole lot more information, but that's not what the "straw man" is all about, is it?

[3] "Repeated exposure to CT scans raises a patient's cumulative radiation to levels experienced by many hydrogen bomb victims in Hiroshima."

Hiroshima radiation exposure came from a fission ("atomic") bomb (uranium gun-type), not a fission-fusion ("hydrogen") bomb. The first fission-fusion bomb was detonated in 1951, six years after the war was over. This is just an indication of the depth of research that went into this list.

The problem with comparing any exposure to the "...hydrogen bomb [sic] victims in Hiroshima..." is that a person's exposure in Hiroshima depended on where they were - how far from the explosion and how much shielding they had. An unshielded person standing 1 kilometer from the blast received an exposure of 4 Gy, which is equivalent to an X-ray exposure of 4 Sv (or 4000 mSv). Using simple math, this is the equivalent of 500 chest CT scans.

Even someone who is being monitored for recurrent lung cancer only gets a chest CT scan every six months (or less frequently), so this would be at least 250 years worth of chest CT scans.

Now, using the inverse square rule of radiation, if a person were standing just over 22 kilometers from ground zero (technically, outside of Hiroshima) and immediately left the area, so as to avoid exposure to fallout, they would have received exactly the amount of radiation that you get from one chest CT.

[4] "In addition, rigorous studies have concluded that CT scans offer no medical benefit whatsoever."

What rigorous studies? I wasn't able to find any, except for those that say that "routine" use of CT scans (or MRI) for "screening" is useless. This is a far cry from "...no medical benefit whatsoever..."

'Tis true that CT scans do not treat any medical condition, but neither are they intended to - they are used for diagnosis, not treatment. As diagnostic aids, CT scans are marvelous (and probably overused, but so are most diagnostic aids in these litigious times). Although many of the indications for CT have been taken over by the MRI (which doesn't use X-rays), the CT scan is still much better at some things (and also a heck of a lot faster).

Jim Laidler
Portland, Oregon USA

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