When a doctor prescribes a medication, we weigh the risks versus the benefits. "Now we need to start having that same kind of question about medical imaging," says Dr. Rebecca Smith-Bindham, radiology professor at the University of California at San Francisco (Time, November 22, 2014). Radiologists are raising red flag warnings about the soaring use of CT scans which typically emit much higher doses of ionizing radiation than traditional x-rays. A regular-dose CT scan of the chest, for example, exposes the patient to 70 times more radiation than a single chest x-ray. The concern is that such high doses of ionizing radiation may eventually lead to cancer. Making matters worse, the more CT scans one undergoes over time, the greater the risk.
"The goal isn't to eliminate CTs but to use them more prudently," says Dr. Smith-Bindman. When appropriately ordered, the benefits of a CT scan far outweigh the radiation risk. In fact, they can be life-saving. But, in many cases, there are other options. "About a third of CT scans are clinically unnecessary or could be avoided by using conventional x-rays or an imaging test that doesn't use radiation, like ultrasound or MRI," according to Columbia University's Dr. David Brenner. In fact, a thorough, risk-free history and physical exam may provide all the information needed.
When is a CT scan NOT beneficial?
Concussion: This is a symptom-based diagnosis. A scan may be appropriate if a skull fracture or brain bleed is suspected.
Headache: MRI, not CT, is the test of choice for most headaches that pose a diagnostic problem, according to the American Headache Society.
Back pain: The majority of cases resolve with conservative treatment. If it persists, an MRI is usually more appropriate than a CT scan.
Sinus infection: A good history and physical is generally all that's needed.
Appendicitis in children: Use ultrasound first, then follow-up with a CT scan only if the ultrasound is inconclusive, according to the American College of Radiology.
The bottom line: Will the outcome of the CT scan change the treatment plan? If not, the CT scan is probably not necessary.