Reduced Patient Exposure to Radiation With Protocol and X-Ray System Changes

August 20, 2012

August 20, 2012 (Rochester, Minnesota) — A change in workplace culture regarding the dangers of radiation exposure in the cath lab and the subsequent implementation of clinical-practice and X-ray system changes can significantly reduce the radiation dose patients are exposed to during invasive cardiovascular procedures, research shows [1]. Over a three-year period, researchers at the Mayo Clinic reduced the mean cumulative skin dose of radiation by 40%.

"There are really two fundamental ways to affect radiation dose in the cath lab," Dr Kenneth Fetterly (Mayo Clinic, Rochester, MN), a medical physicist, told heartwire . "The first is radiation-dose rate, that being how much radiation is given as a unit of time. Also, there is the amount of time that physicians use the X-ray, or how much time their foot is on the pedal. This reduction initiative was an attempt to affect both sides: how much radiation was coming out of the machines as well as elevated physician awareness so there was a desire to do their procedures efficiently from a time perspective."

The new report, which includes data from more than 18 000 cardiovascular procedures, is published online August 20, 2012 in the Journal of the American College of Cardiology: Cardiovascular Interventions.

Following the Advice of the Radiation Safety Committee

In 2008, the Mayo Clinic established a committee to oversee all aspects of patient and staff radiation safety. The Cardiovascular Interventional Labs Radiation Safety Committee included a medical physicist, invasive cardiovascular specialists, anesthesiologists, and other physicians and nurses, and together they developed strategies to increase awareness about radiation management.

The Mayo Clinic labs began announcing intraprocedure air-kerma values, a patient radiation burden metric, in increments of 3000 mGy to encourage staff to take further steps to reduce radiation exposure as the procedure continued. Radiation exposures were routinely included in the patient reports in 2009, with exposures exceeding 6000 mGy reported to the clinic's radiation safety committee. In addition, mandatory fellows training about radiation safety was started in 2010.

In terms of some of the technical changes, X-ray protocols were standardized, including activating the X-ray imaging only when clinically needed, ensuring a maximum distance between the X-ray source and patient, minimizing the air gap between the patient and X-ray detector, and the use of a clinically appropriate X-ray field of view. In addition, the X-ray system underwent some technical changes, including lowering the vendor-provided default radiation-dose rates for fluoroscopy and image acquisition.

The new report includes 18 115 patient studies performed by 27 staff cardiologists and 65 fellows in training. Of the procedures, the clinic performed 4062 PCIs, 9877 coronary angiographies, 459 vascular procedures, and 1070 structural heart procedures.

Compared with the first quarter of the three-year study, the mean cumulative skin dose decreased from 969 mGy to 586 mGy in the last quarter. The mean cumulative skin dose decreased across all procedures, down from 1900 mGy in the first quarter for PCI procedures to 1123 mGy for PCIs done in the last quarter of the three-year study. For coronary angiography procedures, the cumulative skin dose decreased from 712 mGy to 461 mGy. Similar reductions were observed in patients treated for structural heart abnormalities and those undergoing vascular procedures.

"We've always had various radiation-dose awareness initiatives," said Fetterly. "We've always worked to keep the doses reasonable, and that goes back many years. In this most recently published paper, we actually show that our radiation doses are almost 70% lower than they were in 1997. So this is an ongoing effort."

Impressive Institutionwide Effort

To heartwire , Fetterly said the radiation doses in the cath lab, especially for complex procedures or for larger patients, can be high enough to potentially cause skin damage. The routine procedures typically do not cause any complications, but in terms of radiation exposure from medical procedures, the radiation exposure for diagnostic and X-ray guided interventional procedures is on the "high end," he added. There is certainly the potential for injury, said Fetterly, and that was the reason for the Mayo Clinic's dose-reduction program.

"I was really impressed with the physicians' acceptance of the initiative," said Fetterly. "We have a lot of physicians in the lab, a lot of different clinical specialties, a lot of different personalities. One of the things I was impressed by was everybody's willingness to be engaged and participate in the overall practicewide reduction, instead of just a reduction by a small number of individuals. Was I surprised by the reduction? Not surprised, but the 40% reduction was certainly welcomed."