The Radiation Issue in Cardiology: the time for action is now
Cardiovascular Ultrasound
The Radiation Issue in Cardiology: the time for action is now
Eugenio Picano 0
Eliseo Vano 0 1
0 Institute of Clinical Physiology, CNR , Pisa , Italy
1 San Carlos University Hospital, Complutense University of Madrid , Madrid , Spain
The radiation issue is the need to consider possible deterministic effects (e.g., skin injuries) and long-term cancer risks due to ionizing radiation in the risk-benefit assessment of diagnostic or therapeutic testing. Although there are currently no data showing that high-dose medical studies have actually increased the incidence of cancer, the linear-no threshold model in radioprotection assumes that no safe dose exists; all doses add up in determining cancer risks; and the risk increases linearly with increasing radiation dose. The possibility of deterministic effects should also be considered when skin or lens doses may be over the threshold. Cardiologists have a special mission to avoid unjustified or non-optimized use of radiation, since they are responsible for 45% of the entire cumulative effective dose of 3.0 mSv (similar to the radiological risk of 150 chest x-rays) per head per year to the US population from all medical sources except radiotherapy. In addition, interventional cardiologists have an exposure per head per year two to three times higher than that of radiologists. The most active and experienced interventional cardiologists in high volume cath labs have an annual exposure equivalent to around 5 mSv per head and a professional lifetime attributable to excess cancer risk on the order of magnitude of 1 in 100. Cardiologists are the contemporary radiologists but sometimes imperfectly aware of the radiological dose of the examination they prescribe or practice, which can range from the equivalent of 1-60 mSv around a reference dose average of 10-15 mSv for a percutaneous coronary intervention, a cardiac radiofrequency ablation, a multi-detector coronary angiography, or a myocardial perfusion imaging scintigraphy. A good cardiologist cannot be afraid of lifesaving radiation, but must be afraid of radiation unawareness and negligence.
cancer; cardiology; imaging; risk
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of competitive non-ionizing techniques pose special
problems of avoidable long-term cancer risk [1,6]. However,
at that time this position was largely perceived by peers
as being motivated by an attempt of non-radiologist
imaging specialists to expand or defend their own
imaging market shares [7]. In the last 10 years, things have
changed. For a long time ignored by the mainstream
imaging and cardiology community, the linear-no
threshold model in radioprotection assumes that no
safe dose exists; the risk increases linearly with
increasing radiation dose; all doses add up in determining
cancer risk. This model was more generally accepted as
epidemiological evidence matured, and was re-endorsed
by concordant statements of the US National Academy
of Sciences Biological Effects of Ionizing Radiation
Committee (2006), International Commission on Radiological
Protection (2007), and United Nations Scientific
Committee on the Effects of Atomic Energy (2008) [8-10].
Conversely, the hormesis model assuming that low
doses of radiation were less harmful and possibly even
beneficial was abandoned [8-10] although there are
currently no data showing that high dose medical studies
have actually increased the incidence of cancer and the
full validation of the linear no-threshold model is still
lacking in the low dose range (below 100 mSv) [7]. In
particular, the evidence gaps are that radiation data
gathered from atomic bombings were whole body doses
that occurred in a brief period of time, not comparable
to small medical doses applied over days or years.
Radiation given in fractionated doses as happens with medical
testing is probably less harmful than a single dose
applied to the same organ. Many of the long-term
effects, including cancer, become manifest 20 or more
years after the exposure, but diagnostic medical studies
are more frequently performed in elderly patients with
co-morbidities, less likely to live long enough to develop
a radiation-induced illness [7].
In spite of these evidence gaps, in 2005 cardiology
imaging guidelines accepted in principle that the
riskbenefit assessment balance should include long-term
cancer risks on the risk side [11]. In 2005, the
interventional cardiology guidelines of the American College of
Cardiology Foundation emphasized that the
responsibility of all physicians is to minimize the radiation injury
hazard to their patients, to their professional staff and to
themselves [12]. In 2009, the AHA Science Advisory at
last delivered the reference doses of common cardiology
examinations [13], and in 2010 the ACC committee also
overtly expressed the need for appropriate and
optimized use of radiation techniques in cardiology [14]. It
is now generally recognized that all physicians make
every effort to see that each patient should get the
right i (...truncated)