Download this article's Factoid in PDF (& PPT for Gold Subscribers)

Implementing systemic practice and technical changes in the cath lab as part of a radiation safety program can yield significant reductions in patient exposure, according to a study published in the August 2012 issue of JACC: Cardiovascular Interventions.

Kenneth A. Fetterly, PhD, of the Mayo Clinic (Rochester, MN), and colleagues evaluated radiation exposure from a total of 18,115 invasive procedures performed at their institution between June 2008 and May 2011 as a radiation safety program was being implemented. Practice changes included announcing high air kerma (a measure of patient radiation burden) values in the cath lab, creating a procedural summary report, and requiring radiation safety training for fellows, while technical adjustments included lowering fluoroscopy dose rates, standardizing imaging protocols, and reducing the fluoroscopy frame rate by half.

A Systematic Approach to Safety

Between the first and last quarters of the study period, the mean cumulative skin dose to patients decreased by 40% for all procedures. Reductions were also seen in procedural subsets: 41% for PCI, 37% for coronary angiography, 34% for structural heart procedures, and 53% for vascular procedures (table 1).

Table 1. Cumulative Skin Dose During First vs. Last Quarter of Study Period

 
The overall reduction in cumulative skin dose resulted from a 46% decrease in mean acquisition skin dose and a 33% decrease in fluoroscopy skin dose. In addition, between the first and last years of the study period, there was a decline in the proportion of procedures for which the cumulative skin dose exceeded the 6,000 mGy threshold that triggered reporting to the institutional radiation safety committee (0.33% to 0.13%; P = 0.04).

Among the 21 physicians who performed at least 10 cases in both the first and last quarters, 19 were associated with patient radiation dose reductions of 22% to 69%, while the remaining 2 operators were associated with increases of 6% and 33%.

“Building on a philosophy of radiation safety, substantial patient radiation-dose reduction can be achieved through organized and sustained practice and X-ray system technical changes,” the authors conclude.

Application of Mayo Program Feasible

The most important message of the paper is that an institutional radiation safety initiative is “doable,” Stephen Balter, PhD, of Columbia University Medical Center (New York, NY), told TCTMD in a telephone interview. “If physicians are willing to accept less than perfect image quality but image quality that is still good enough to do their procedures, then they can get meaningful dose reductions.”

According to Dr. Balter, the Mayo Clinic took a number of fairly common dose-reduction steps and implemented them in a systematic way. However, he noted, an unusual accomplishment was convincing cardiologists to use 7.5 frames per second as the standard fluoroscopy frame rate, down from 15 frames per second. While common in Europe, “this is something it will take US physicians a little time to recalibrate,” he said. “It’s just a matter of their expectation of what an image should look like.”

Hitinder S. Gurm, MD, of the University of Michigan Cardiovascular Center (Ann Arbor, MI), also singled out use of the lower frame rate. “I think a lot of what we do can be done with [the 7.5 rate],” he said. “One can always use it as the default and switch to a higher frame rate when necessary.”

Radiation Problem Not Visible

Part of the problem is that physicians become accustomed to doing procedures a certain way, Dr. Gurm noted, but another contributing factor is that they can at times ignore the downside of radiation. Unlike doctors who use GP IIb/IIIa inhibitors and become more selective if bleeding occurs, for example, “radiation is not something that we actually see,” he commented.

Dr. Gurm suggested that the reduction in radiation exposure in the study may represent a plateau in safety efforts, “or at least a point of diminishing returns.”

Dr. Balter agreed, noting that “we’re fighting a battle where the technical dose is being reduced, but to some extent the procedures are getting more complicated.”

One fault of the paper, Dr. Balter said, is its use of the term ‘cumulative skin dose.’ “The reader should not assume that that is the actual skin dose. That would be true only if the [radiation] beam doesn’t move during the procedure, and I know of virtually no cardiac procedures where they never change the angles,” he explained. The reference air kerma, however, is a perfectly good index for quality assurance, he added.

Drs. Gurm and Balter both noted that having a committee to specifically focus on radiation safety is key to success. “It brings people together and helps motivate the culture,” Dr. Balter said. Providing regular feedback is also important and a strong motivator to improve practice, Dr. Gurm added. “And the beauty of training fellows is that they get used to [the new, safer ways], so they will go out and influence other people to use [the same techniques],” he said.

Currently not many centers use this kind of program, “but perhaps this [paper] will encourage more people to [try] it,” Dr. Balter concluded. “The caveat is that individual physicians are going to have to ask themselves whether the image quality they’re used to is more than they really need and if they’re willing to back off.”

Study Details

Procedures were performed using 4 Philips Integris (Philips Medical Systems, Best, The Netherlands) and 4 Axiom Artis (Siemens Medical Systems, Erlangen, Germany) interventional X-ray systems. Two-thirds of patients were male, with a median age of 66 years.

Related Stories:

• Action Plan to Optimize Radiation Safety of Cardiovascular Imaging Developed
• Standard Protocol for Coronary CTA Cuts Radiation, Maintains Image Quality
• Cardiology Fellows Inadequately Trained in Radiation Protection Techniques