|From the WSJ article...|
As you can see from the graphic that appeared in the article (right) about 85.3 million CT scan were administered in 2011.
Let's compare that to the population of the US - 313 million (see this): 27% of all people in the US (provided each had one) get a CT scan each year.
As for children, there were about 75 million children in the US in 2011 (see this). If only children had CT scans this would mean 113% of all children had a CT scan each year.
CT scans are not cheep. The "street price" for a negotiated, "I don't have insurance" situation seems to be on the order of $750 USD (based on an anecdotal search of the internet) and on the order of $7,500 USD if insurance picks up the tab.
At the "street price" that's about $63 billion (with a "B") USD a year for CT scans (of course this does not count any cost to have the doctor read it, treat you, etc.).
And if insurance is picking up the tab, more like $630 billion USD.
The truth, I suspect, is somewhere in between - let's just call it $100 billion USD.
A CT scan is like an X-ray except it presents the doctor with a "cross section," i.e., as if you were sliced in half by a guillotine (outer images). A standard X-ray produces an image like you see in the center.
A CT scan works like this (from here): There is a giant "ring" which the CT operator places your body into - its like a doughnut. You are positioned in the doughnut where the "slice" is to occur (as in the image above the head would be in the center of the doughnut).
Inside this doughnut is an X-ray "head" and 180 degrees opposite is the X-ray "receiver."
The "head" starts at one spot, shoots an X-ray through you that is recorded by the "receiver" and moves about 0.3 degrees. So to go around the doughnut you are X-rayed about 1,000 times.
The receiver, instead of being film, is an electronic device that records the high-energy X-ray photons and sends them to a computer.
After the head has completed its full rotation the computer assembles the "cross section" image as you see above.
So while the CT scan may (and I stress may) provide valuable insight into a problem you have to ask yourself if its worth 1,000 X-ray exposures to get that insight.
With enough CT scans being prescribed per year such that everyone in the country could have one every four years you basically have a national exposure rate to X-rays of about 250 per year per person.
Unfortunately this is known to cause cancer. Hard X-ray's, unlike things known to cause cancer to the state of California, e.g., gasoline, are actually dangerous. The high-energy photo hits some molecule in the cell and damages, e.g., a piece of critical DNA.
Of course the distribution is not even - some people get a lot of CT scans per year, some never get any.
My guess is that a primary reason there are so many CT scans is one that doctors fear, for reasons of malpractice, making an incorrect diagnosis by not having a good "cross section" to use to diagnose the problem - so they order a CT. The second reason is that Medicare/Medicaid pays and once the machine is installed you have to use it - so no matter what the government pays you need to move bodies through it to make the payment.
I am quite certain that over all no one keeps track of how many you have. (My mother had one a while back and had one some years previously. Had she not mentioned this no one would have noticed or cared.)
The real question here is "is all this worth it?"
The cancer rates are low according to the WSJ article: one case of leukemia in 10,000 people ten years after a CT exposure, one case of brain cancer in 30,000 people ten years after.
But, there are 85,000,000 CT scans a year. So even if the additional rate is one in 10,000 that's potentially 8,500 additional cases of leukemia a year and 2,800 additional cases of brain cancer.
Why, this could even be masquerading as "cell phone" brain cancer everyone fears but cannot prove...
In any case CT scans are very dangerous in my book and have significant and demonstrable negative side effects.