April 2011

Radiation Dose: What Is Too Much?
By Jim Knaub
Radiology Today
Vol. 12 No. 4 P. 4

While sitting in an interview room in the HIMSS exhibit hall, an executive with a CT manufacturer was discussing his company’s dose-reduction software. He was pleased to share how it would warn the user when the patient may be exposed to too much radiation.

“How does it determine what is too much?” I asked.

“The user sets that,” he said, acknowledging that the industry wants nothing to do with making that decision.

The next day at the same show, I asked a radiologist, “Who determines how much is too much radiation?”

He quickly said he knew of no standard, either in a single CT scan or for the number of CT scans in a year. “We can all agree that 40 scans per year are too many,” he said. “But what about 20? Or 10?”

“What should that number be?” I asked.

He smiled and said, “That’s above my pay grade.”

I suppose that makes sense—in an Alice in Wonderland sort of way.

You certainly can’t make a blanket rule. There is good reason radiologists speak in terms of evaluating a CT exam’s risks and benefits before performing the imaging. The same goes for advocating dose that is “as low as reasonably achievable.” In diagnostic imaging, there are numerous potential variables on both the risk/benefit side and the patient side. Is the patient an adult or a child? Thin or obese? Have a history of previous CT scans? Are physicians evaluating head trauma from a violent collision or something more routine? Is there an alternative exam available that could do the job? And so on.

While those variables are defensible and supportable, they also contribute to growth in CT scan usage and the resulting radiation exposure—some of which is not needed. It also seems to me that these complex variables have the unintended consequence of suppressing the raising of red flags when it may not be appropriate to proceed with an exam. That has the net effect of greasing the skids to push ahead with more exams.

We’ve all read about the cases where we wished someone would have raised a red flag. Someone asking, “Are you really sure this radiation dose is what you need to obtain the information about this patient?

Decision-support and appropriateness criteria would help but to what extent is unknown. Sad to say, but I have to agree with the radiologist at HIMSS: The answer to this question is above my pay grade.

Enjoy the issue.