Dave Fornell, editor of DAIC Magazine
Defining the Cath Lab Workplace Radiation Safety Hazard
The biggest workplace concern for interventional cardiologists and cath lab staff is their daily exposure to ionizing radiation from the angiographic X-ray systems that are central to their procedures. In addition to increased cancer risks and developing cataracts, they are also worried about orthopedic issues caused by wearing heavy radiation protection aprons, which takes a toll on the spine and can lead to chronic back problems.
Interventional cardiology is a relatively new subspecialty, with the first interventional cath labs established in the late 1980s. But over the past decade, concern has risen sharply as older interventionists began showing high rates of cataracts, left-side brain cancers and chronic orthopedic back problems. For this reason, the younger generation of new interventional cardiologists are actively looking for ways to reduce their radiation exposure and eliminate the need to wear lead aprons, or at least reduce the weight.
Longer, More Complex Procedures Lead to More Radiation Exposure
While angiography imaging system vendors have all made great strides with new technologies that reduce the amount of X-rays needed while maintaining excellent image quality, the procedures have become more complex and are lasting longer. Transcatheter procedures now include treating chronic total occlusions (CTOs), which can take two or three hours, instead of the easier, straightforward percutaneous coronary interventions (PCIs) that had average procedure times of about 30 minutes. Peripheral artery disease (PAD) procedures in the legs also tend to be more involved and complex than coronaries. These lesions are often long and diffuse, requiring multiple stents and extra vessel preparation.
The number of transcatheter structural heart interventions also are rapidly increasing. These include transcatheter heart valve repair and replacement, septal defect closure, left atrial appendage (LAA) occlusion and sealing paravalvular leaks. These procedures can take longer and require more imaging that standard PCI stent placements.
What is the Average Radiation Exposure for Interventional Cardiologists?
There have been several studies attempting to establish a baseline for average staff radiation exposure.
A 1992 study, conducted prior to the introduction of today’s lower-dose imaging systems, estimated radiation exposure received by all in-room staff in three cardiac cath labs that performed more than 15,000 procedures over a five-year period. The study found head and neck areas generally receive about 20-30 millisieverts (mSv) per year. For comparison, the average background radiation exposure in most countries is about 2.4 mSv, and an average computed tomography (CT) scan is about 3-8 mSv.
The study showed all staff received a body dose equivalent well below regulatory limits set at the time of 150 mSv per year, which was the recommended limit for the lens of the eye to prevent cataracts.
The physicians in training and the staff physicians were found to be more likely to reach this limit. The data also showed only a small correlation between the annual number of procedures and the annual head dose equivalent of a physician. The researchers said this is likely due to variation in the doctors’ working attitudes and techniques. The mean dose equivalent at the collar level of the interventional cardiologists was estimated to be between 0.04-0.02 mSv per procedure.
A more recent study from 2013 found interventional cardiologists have an exposure per-person, per-year that is about 10 times higher than diagnostic radiologists. The data show cumulative doses after 30 years of working life are in the range of 50 to 200 mSv, with a projected professional lifetime attributable excess cancer risk in the order of magnitude of 1 in 100.
The study found the left side of the operator is exposed to between 30-100 percent more X-ray radiation than the right side because of where interventionists stand in relation to the C-arm of the angiography system. The left side of the head and less protected parts of the body like the hands can receive equivalent doses between 5-50 mSv per year.
Another study found lifetime cumulative whole-body exposure of less than 200 mSv. However, life-time head exposures were estimated to be much higher because of the lack of protection, in the 1-3 Sievert (Sv) range. Radiation therapy treatments start around 2 Sv. A 1-3 Sv range to the head is a brain equivalent dose around 500 mSv, according to the study.
Cath Lab Staff Radiation Exposure Levels
A lot of information on radiation exposure in the catheterization lab is related to the doctor, not the nurses and technologists working alongside them. This is partly because the doctor usually stands the closest to the X-ray source and the patient table, and so receives the highest dose of scatter radiation. However, a 2017 study in the Journal of the Americans College of Cardiology (JACC) shed some light on exposures and possible ways to offer increased radiation protection for cath lab staff.
The study established a baseline exposure using real-time radiation exposure data collected from nurses and technologists during 764 consecutive catheterizations. Of these, 401 procedures used standard radiation protection measures, and in another 363 cases, accessory lead shields were used to protect staff members. The shielding was associated with a nearly two-thirds reduction in radiation exposure.
The study reported radiation exposure as the effective dose normalized to dose-area product (EDAP — mSv/[mGy × cm2] × 10−5). Using this method, without shielding nurses were exposed to about 1.1 EDAP and techs about 2.4 EDAP. With shielding this was reduced to about 0.5 for nurses and 1 for techs.
For more on how to improve radiation safety in the cath lab read the article "5 Technologies to Reduce Cath Lab Radiation Exposure."
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2. UNSCEAR 2008 REPORT Vol. I, SOURCES AND EFFECTS OF IONIZING RADIATION. United Nations Scientific Committee on the Effects of Atomic Radiation. UNSCEAR 2008 Report to the General Assembly, with scientific annexes. Issued in May 2016. http://www.unscear.org/unscear/en/publications/2008_1.html
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