Patient radiation dose drops 61% with imaging changes

Interventional cardiologists reduced the radiation dose in patients with congenital heart disease by 67 percent using a combination of practice and technical changes, according to a study published online June 20 in Catheterization and Cardiovascular Interventions. Most pediatric and adult patients benefited from the revised protocol.

Medical advancements now allow patients with congenital heart disease live longer. But as a consequence, they often undergo repeated catheterizations during their lifetimes, which expose them to repeated doses of ionizing radiation.

“Therefore, minimizing radiation dose while maintaining clinically useful image quality is an important patient safety initiative,” wrote lead author Daniel A. Maurillo, MD, of the Mayo Clinic in Rochester, Minn., and colleagues.   

The clinic initiated an imaging protocol between 2008 and 2010 that took a two-pronged approach to radiation reduction. On one front, they instituted five practice changes and on the other, five technical changes.

The practice changes included the formation of a cardiovascular interventional laboratory safety committee; internal reporting of case dose over 6,000 mGy; an intraprocedural announcement when 3,000 mGy was reached; air kerma listed in final reports; and compulsory fellow radiation training. On the technical side, they increased x-ray beam spectral filtration; changed the default fluoroscopy setting to low; decreased the fluoroscopy frame rate to 7.5 frames per second; reduced acquisition detector dose; and removed the antiscatter grid for patients weighing less than 20 kg.

To assess the effectiveness of the changes, they performed a retrospective study based on adult and pediatric patient records for 1,082 procedures done between 2008 and 2012. They categorized patients by age, weight and intervention type (nonintervention, simple and complex). The review period involved four staff cardiologists and 43 fellows using either Siemens Axiom Artis or Philips Integris systems.

The mean age of patient was 32 years. Comparing the first year to the last, they found that the median air kerma for all procedures fell from 424 mGy to 200 mGy, for a decrease of 61 percent. Mean fluoroscopy time did not change between periods.

They saw a 71 percent decrease in the nonintervention group over the study period; a 74 percent decrease in the simple intervention group; and no change in the complex intervention group. By age group, they reported a 74 percent drop in patients between 10 and 17 years old; a 67 percent decrease in adults; no change in infants; and a dip in children between 1 and 9 that was not statistically significant.

By weight, there was no statistically significant change between 0 and 20 kg; a 74 percent decrease in the 20 to 60 kg group; and a 64 percent drop in patients weighing 60 kg and more. The 0 to 20 kg group included one 4-year-old boy who underwent four complex, staged interventional procedures. Excluding that one patient resulted in an estimated air kerma reduction of 67 percent.

“Through a combination of technical changes made to x-ray fluoroscopy systems and implementation of provider awareness initiatives, our congenital heart practice was able to dramatically reduce patient radiation dose for most pediatric and adult CHD [congenital heart disease] patients undergoing cardiac catheterization,” they wrote.

The study was single center and retrospective. Consequently, Maurillo et al added, while they believed the initiative led to reduction in dose, the study could not prove any causal relationship.