The New York Times featured an article on June 29th that discussed rapidly expanding use of CT scans for the heart. The article discusses the potential for overuse of this and other diagnostic testing when the physician actually owns the device and profits from the volume generated. It also highlights the very substantial radiation exposure of angiograms performed on CT devices.
However, the article goes on to say that “they expose patients to large doses of radiation, equivalent to at least several hundred X-rays, creating a small but real cancer risk.”
Is this true?
Sadly, though the reporters discuss both CT heart scans and CT coronary angiograms, they confuse the two and use the terms interchangeably. Yet they are as different as a Smart Car vs. a Hummer─yes, both are cars, but they represent two different ends of a wide spectrum.
Likewise with CT scans of the heart.
A heart scan is a simple screening test for coronary atherosclerotic plaque. It detects the presence of calcium in the heart’s arteries, provided as a “score.” (Because calcium occupies 20% of total plaque volume, knowing the amount of calcium tells you how much total coronary plaque is present.) If you have a high score, it should trigger an effective prevention program, since atherosclerosis is present. (In fact, that is what my book, Track Your Plaque, is all about: how heart scans can serve as the start of a prevention─even reversal─program to manage coronary plaque.) Just having a high score should not prompt heart procedures, since people undergoing simple screening heart scans are without symptoms. However, a stress test may yield some useful information. On the other hand, if you have a score of zero, great! A less intensive prevention program may suffice.
What about radiation risks?
On present-day CT devices (64-slice or greater multi-detector scanners, or electron-beam scanners), heart scans are performed with about the same quantity of radiation as a mammogram done to screen women for breast cancer, or about the equivalent of four chest x-rays.
CT coronary angiograms, while performed on the same devices as heart scans, require x-ray dye to fill the contours of the coronary arteries. It also requires more radiation, up to several hundred times more radiation. While new engineering innovations are being introduced that promise to reduce this exposure, the current devices being used today do indeed require a radiation dose equivalent to 100 to 400 chest x-rays, a value that approximates that obtained during a conventional heart catheterization.
While heart scans are most useful to detect and quantify plaque that can help determine the intensity of your prevention program, CT coronary angiograms are generally used as prelude to hospital procedures like catheterizations, stents and bypass surgery. That’s because they are performed to look for (or rule out) “severe” blockages.
Two different tests, two different kinds of information provided, two very different levels of radiation exposure.
The New York Times article otherwise does a credible job of exposing an unhealthy trend in medicine: the leap to new technology just because of “newness,” even before clinical experience develops that proves genuine superiority. This eagerness to embrace new for its own sake is a substantial part of the reason why healthcare costs continue to escalate.
But, despite their otherwise well-written description, the article failed in one critical aspect: They failed to distinguish two very different tests, criticizing one test with the shortcomings of another. Don’t you fail to make the distinction.
In my view, if you desire an easy means of screening for the hidden coronary plaque that leads to heart attack, that’s what simple CT heart scans provide─with low-radiation exposure. But if your doctor requires greater information, such as that which can lead to stents and bypass surgery, then a CT coronary angiogram is just one emerging choice, though one that comes with significant radiation exposure in 2008.
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Published On: June 30, 2008