Safety initiative leads to 40% drop in radiation dose

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By implementing a combination of practice and x-ray system changes, cardiologists reduced the radiation dose administered to patients undergoing invasive cardiovascular procedures by 40 percent over a three-year period, according to a study published online Aug. 20 in the Journal of the American College of Cardiology: Cardiovascular Interventions.

In the paper, Kenneth A. Fetterly, PhD, a medical physicist in the division of cardiovascular diseases at the Mayo Clinic in Rochester, Minn., and colleagues described a radiation safety initiative rolled out at their cardiac cath lab between 2008 and 2011 that was designed to reduce patient radiation dose.  

The program combined changes in clinical practice with technical changes, using patient- and procedure-specific cumulative skin dose calculated from air-kerma values as a measure. The three-year comparison was based on the first and last quarters of the study.

The practice component included the establishment of a radiation safety committee for cardiovascular interventional labs; announcements of intraprocedure air-kerma values in increments of 3,000 mGy; reporting of procedures that exceeded 6,000 mGy; inclusion of procedure air-kerma in the clinical reports; and compulsory radiation safety training of all fellows. The x-ray system technical changes involved standardized protocols among similar systems; increased spectral filtration for acquisition imaging; a change in default fluoroscopy dose rate mode from normal to low; a reduced fluoroscopy frame rate from 15 frames to 7.5 frames; and a reduced acquisition detector target dose.

They used all invasive studies on adult patients who provided research consent over the study period. Procedures included PCI, coronary angiography, noncardiac vascular angiography and intervention as well as interventional treatment for structural heart disease. The majority of the 18,115 procedures were performed on men (63.9 percent). A total of 27 staff cardiologists and 65 fellows-in-training participated.

Fetterly and colleagues calculated that the mean cumulative skin dose for all procedures declined by 40 percent, ranging from 53 percent for noncardiac vascular angiography and intervention to 37 percent for coronary angiography. For all procedures, the mean acquisition skin dose decreased by 46 percent and the fluoroscopy skin dose was lowered by 33 percent in the three-year period.

The authors attributed the reduction to a culture and philosophy of radiation safety and emphasized probable benefits for physicians and staff, as well. “Because radiation scatter that results in occupational dose is directly proportional to patient dose, reductions in patient dose can be expected to have a complementary effect on radiation dose to staff,” they wrote.

Other observations that they noted:
  • Great variability in interpatient and interprocedure cumulative skin dose, with radiation dose reductions ranging from 22 percent to 69 percent among physicians who performed 10 or more procedures in the first and last quarters; and
  • Patient dose was reduced concurrently with increased use of radial access.

“Through our efforts, we were able to quickly cut the overall radiation exposure to patients by nearly half using simple but effective methods,” Charanjit Rihal, MD, senior author and chair of the clinic’s cardiovascular diseases division, said in a release. “We think this program could serve as a useful model for other cath labs in the U.S.”

The authors added that other factors come into play when initiating a radiation reduction program. “To reduce patient radiation dose requires that the physician’s expectations change from a desire for excellent image quality to a desire for low radiation dose and acceptance of clinically adequate image quality,” they wrote. “To implement change also requires a good understanding of the technical capabilities of modern digital x-ray imaging systems.”