Ever worry about standing too close to the microwave as it works its magic for you in the kitchen? Or maybe think that you spend too much time on your cell phone? Sure, neither give off a ton of radiation in a single dose, but sometimes you might wonder what's safe?

That leads us to a big story that broke this week about computed tomography (CT) scans. According to a JAMA piece, published by researchers from Germany and the Mayo clinic, patients who receive a single heart CT scan are exposed to the same amount of radiation they'd receive from 600 chest X-rays. That 600 is a median figure; patient weight, heart rhythm, and length and type of scan affected the amount of radiation. Some patients received more, some less.

While a dosing algorithm called "electrocardiographically controlled tube current modulation" reduced radiation by about 25 percent in about three-quarters of patients, another technique called "sequential scanning" (according to Bloomberg, it's when the CT scan of the heart is done in pieces, with the X-ray on for a brief part of each scan) reduced the dose of radiation by 78 percent. But it was only used six percent of the time.

To be fair, sequential scanning cannot be used on every patient and the evidence base for it is not yet broad. However, the authors say their findings are in line with other recent studies.

Additionally, Bloomberg mentions a previous New England Journal of Medicine study that said CT scans weren't as reliable as cardiac catheterization for finding heart disease. While looking for that article, I came across this one that says one-third of CT scans are not justified by medical need. Reuters tells us:

While strategies are available that can substantially lower radiation doses from CT scans, such as reducing voltage, some of these techniques are not being widely used, the researchers found. That could be because many clinicians may still be unfamiliar with the magnitude of radiation exposure that is received from a cardiac CT scan, they said.

In fact, the NEJM article referenced above cites this survey of radiologists and emergency physicians— where three-quarters of respondents significantly underestimated the radiation dose from a CT scan. Bloomberg elaborates:

"If you have a patient with no chest pain and no shortness of breath, then a test that uses that level of radiation isn't right," said study author Gerber, a cardiologist at the Mayo Clinic branch in Jacksonville, Florida, in a telephone interview today. "If the patient feels great and hasn't got much in the way of risk factors, and the doctors insist they have the test, it might be reasonable to question it." 

According to the JAMA article, "A basic principle of radiation protection is to keep radiation exposure ‘as low as reasonably achievable' (ALARA principle)."

So are CT scans ever worth it? Absolutely. Former New America colleague and neurosurgeon Guy Clifton has a new book titled Flatlined: Resuscitating American Medicine that details how pre-1976 brain tumors were detected: it was messy. Now with CT and MRI scans, physicians can determine whether "a mass is a blood clot or a tumor, what kind of tumor it is, how close it is to speech and movement centers, and how it is affecting the surrounding brain." Dr. Clifton calls the difference "night-and-day." But Dr. Clifton, in a post on this blog a few months ago, also wondered about whether CT heart scans were being used wisely.

The key is to better understand when a CT scan is necessary. When it comes to your head, sometimes it is clearly necessary. When it comes to your heart, it is safe to say some overutilization is occuring. But apparently we're just getting started. An accompanying piece in JAMA by Dr. Andrew Einstein of Columbia University writes that the number of CT scanners installed in US cardiology practices has tripled in the past two years. Unfortunately, those machines don't pay for themselves by sitting idle.

A center for comparative effectiveness research would be a great start to disseminating how to reduce the risk of overradiating people, don't you think?