From Mayo Clinic’s Discovery’s Edge magazine
Reducing radiation exposure from CT scans has become one of the primary goals of Mayo Clinic’s CT Clinical Innovation Center. Dr. Cynthia McCollough and her colleagues are doing the Radiation Limbo: How low can they go without sacrificing image quality.
At a time when CT scans are being used with greater frequency, the work of Mayo researchers has cut the risk of exposure without sacrificing image quality or diagnostic capability.
Dr. McCollough is continually looking for ways to lower radiation exposures while maintaining the needed quality. A critical step in that process includes better defining what level of image quality is needed.
“We don’t always need pretty pictures,” says Dr. McCollough. “We only need pictures that clearly show the disease or injury. For some conditions, a really low exposure of radiation can be used.”
To reduce the amount of radiation patients are exposed to, the CT Clinical Innovation Center takes several routes. “The most basic, low-tech thing we can do is to ‘right-size’ the dose,” says Dr. McCollough.
Mayo Clinic has developed a computerized set of electronic protocols that are centrally managed. If an adjustment is made to a protocol, the correct, new information is instantly available at all 25 CT scanners on the Mayo Clinic campus in Rochester, Minn., as well as at all Mayo Clinic Health System sites, and the Mayo practices in Florida and Arizona.
A CT scan of a patient with a small, non-obstructing kidney stone. In the left image, the stone is visible (arrow); in the right image from a follow-up exam, acquired using 60 percent less radiation, the stone is still easily detected (arrow).
Much like the automatic exposure feature on a camera, CT scanners can now automatically adjust the radiation exposure that the patient receives based on the type of exam and the size of the patient. “Everything we’re doing with dose reduction is to make sure patients get the exams they need at the lowest radiation doses,” says Dr. McCollough.
One area where use of medical radiation has increased dramatically in recent years is in cardiology. It is also one of the areas that has seen significant decreases in the levels of radiation exposure. Dr. Charanjit Rihal, a cardiologist at Mayo Clinic, says the results have been encouraging. “We reduced the amount of radiation by at least 40 percent, and in some cases, by as much as 70 percent.”
Charanjit S. Rihal, M.D., the William S. and Ann Atherton Professor of Cardiology Honoring Robert L. Frye, M.D., is chair of cardiovascular diseases at Mayo Clinic.
Another of Dr. McCollough’s colleagues, Dr. Joel Fletcher a radiologist and the medical director of the CT Clinical Innovation Center, worked with the pediatric oncology group to lower the radiation dose for follow-up CT scans for children diagnosed with cancer who had completed treatment.
“We just kept turning down the dose until finally it was down to the lowest setting the scanner would run at,” says Dr. McCollough. With each setting, a pediatric radiologist would look at the scan to ensure that the image was still clear. “We try to do the limbo: you know, ‘How low can you go?’”
With education, new technology, and collaboration between physicists, radiologists, and other physicians, Mayo Clinic is answering that question.