PISA, ITALY — In a new position paper, the European Society of Cardiology (ESC) calls for cardiologists to be more aware of radiation doses in cardiac imaging tests. The paper, from the Cardiovascular Imaging, Percutaneous Cardiovascular Interventions, and Electrophysiology associations of the ESC, summarizes current knowledge on effective radiation doses and risks related to cardiac imaging procedures and is published online January 9, 2014 in the European Heart Journal.
"X rays and gamma rays used in radiology and nuclear medicine are proven (class 1) carcinogens, and cardiologists should make every effort to give 'the right imaging exam, with the right dose, to the right patient,' " Dr Eugenio Picano (Institute of Clinical Physiology, CNR, Pisa, Italy) and colleagues advise.
"Cardiology accounts for 40% of patient radiology exposure and equals more than 50 chest X rays per person per year," Picano said in a statement. Cardiologists need to be aware of the magnitude of the risks and order these tests appropriately. "We need the entire cardiology community to be proactive in minimizing the radiological friendly fire in our imaging labs," he added.
"A smart cardiologist cannot be afraid of the essential and often lifesaving use of medical radiation but must be very afraid of radiation unawareness," the researchers conclude.
From a literature review, the authors determined that on average, PCI, cardiac radiofrequency ablation, multidetector coronary angiography, or myocardial perfusion imaging scintigraphy each deliver an effective radiation dose of about 15 msV, which is equivalent to 750 chest X rays per procedure. The average effective doses for these procedures varied widely—from 1 to 60 msV, equivalent to 100 to 2000 chest X rays.
Paper Aims to Summarize Current Knowledge
Recent estimates suggest that a third or more of cardiac examinations are partially or totally inappropriate, and most doctors grossly underestimate the radiation doses for most commonly requested tests, the researchers write.
Although radiation risks are probably not the most important risks associated with cardiac examinations, "they are probably the least well known and the least considered in . . . daily decision making," they add.
This position paper aimed to summarize the current knowledge on radiation effective doses and risks related to cardiac imaging procedures.
They found that based on an effective dose of 10 to 100 mSv, the additional lifetime risk of fatal and nonfatal cancer for one PCI ranges from one in 1000 to one in 100 for a healthy 50-year-old man and is 1.38 times higher in women and four times higher in children.
"Even in the best centers and even when the income of doctors is not related to number of examinations performed, 30% to 50% of examinations are totally or partially inappropriate according to specialty recommendations," Picano noted in a statement. "When examinations are appropriate, the dose is often not systematically audited and therefore not optimized, with values that are two to 10 times higher than the reference, expected dose," he said
Being aware of the magnitude of the radiation risks and ordering tests appropriately is key.
On the positive side, there has been progress in reducing the dose of radiation, the researchers note. During the past decade radiation dose has decreased dramatically in CT scanning through increasing dose-saving measures and improved scanner technology. If the heart rate is sufficiently slow and regular, gated cardiac CT can produce diagnostic-quality images with a mean effective radiation dose of <2 mSv or even <1 mSv.
In the US, nuclear cardiology imaging accounts for more than half of all nuclear medicine procedures, and radiation exposure can be decreased by 75% using a protocol where stress imaging is performed first.
Radiation Doses Are Dropping
Commenting to heartwire , Dr Matthew Budoff (Los Angeles Biomedical Research Institute, CA), agreed that medical imaging tests that expose patients to radiation need to be ordered appropriately and "doctors and patients in general need to be cognizant of all the risks in testing." However, "we have to balance both risks and benefits when we think about [any] diagnostic and therapeutic testing," he observed.
The position paper is similar to a scientific statement published by the American Heart Association about four years ago, by Thomas Gerber and colleagues to raise awareness of radiation exposure and common doses, but "unfortunately it does not reflect the most recent updates that have occurred over the past four years," he noted.
For example, the average dose of 15 mSv for PCI that Picano and colleagues refer to was based on a reference from 2008. "The average [radiation] doses with cardiac CT are now one-third of that, and nuclear imaging [radiation doses] have come down by 50%." Although the authors allude to changes that can be made to lower the dose, their references are old.
Radiation is just one of many risks, and is "probably one of the smallest risks for our patients. . . . Clearly, [in] PCI, the theoretical radiation exposure is the smallest possible consideration at the time of the test compared with the procedural complications that can occur," he said.
Picano received research funding through the CNR-Institute of Clinical Physiology from Sorin, Boehringer Ingelheim, Medtronic, and Malesci. He is the inventor of a pacemaker licensed to Medtronic. Disclosures for the coauthors are listed in the paper. Budoff has received research/grant support from HeartFlow, study funding from Wakunaga of America and GE Healthcare and has been a consultant and speaker for GE Healthcare.
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Cite this: ESC Urges Cardiologists to Be Aware of Radiation Doses - Medscape - Jan 09, 2014.