Debating the Cumulative Radiation Dose Theory

Despite the attention being given to the cumulative CT scan radiation effect and the buzz surrounding risks of repeat CT scans, one leading expert is disputing the theory.

As reported in Diagnostic Imaging, Richard Morin, Ph.D, chair of the American College of Radiology’s safety committee says, “There is no radiation biology to demonstrate CTs are additive in any way.”

Morin uses a driving analogy that relates probability of an accident to the number of miles logged by a driver, but notes that there is not a certain mile threshold, like 200 miles, that would trigger an accident.

I like the driving analogy and used it in my recent post Measuring Risk: Driving vs. CT. Driving is something that most of us can relate to, and therefore the numbers are more meaningful, so I’ve tried to quantify it even further.

Here’s how I like to look at the risk: The risk of dying from a cancer induced from a CT of the abdomen and pelvis in a middle aged male is similar to the risk of dying in a car accident if you drive 36,000 miles – both are about one in 2000.

The debates over cumulative dose theory will continue, and so I feel it’s important to explain the risks in ways people can understand – so that they don’t turn down any life-saving exams out of fear or misunderstandings.

While Dr. Morin explains that there is no way to figure out whether a person developed cancer due to radiation, a carcinogen or chance, he does say “it’s important that the right test is ordered at the right time.”  I’ll add that it’s always a good idea to look at lowering the CT dose, too.

And while the effect of cumulative dose from multiple exams is unproven, we really must take the most conservative position when it comes to public health and assume the effect is cumulative.