Dose reductions achieved despite a large number of obese patients
Vienna, Austria – 7 May 2017: A large nuclear cardiology laboratory has slashed its average radiation dose by 60% in eight years, according to new research presented today at ICNC 2017 and published in JACC: Cardiovascular Imaging.1,2 The study in over 18 000 patients shows dose reductions were achieved despite a large number of obese patients.
“There has been concern amongst the medical community and the public that the radiation from medical diagnostic tests could increase the risk of cancer,” said Professor Randall Thompson, a cardiologist at the Mid America Heart Institute, Kansas City, Missouri, US.
He continued: “Although the risk of harm from an individual nuclear cardiology test is very low – even very conservative estimates suggest only one in 1 000 extra patients would develop cancer 20 years later – the cumulative dose from multiple medical diagnostic tests may be a concern.”
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The average radiation dose fell from 17.9 mSv in 2009 to 7.2 mSv in 2016 and the median dose (the 50th percentile) dropped from 10.2 mSv to 2.5 mSv. Professor Thompson said: “There was a dramatic lowering of the radiation dose with all of these concerted efforts. The average dose fell by 60% and the median dropped by 75%.”
“The average dose had fallen to 5.4 mSv in 2012 but crept up as we’ve had more obese patients referred in whom we have to use the higher dose protocols,” he added. “But more than half of patients now are tested with a low-dose, stress-only test using the new technology, which is why the median dose of radiation has fallen so dramatically.”
The average background dose for people living in Europe and North America from radon underground and cosmic background sources is about 3 mSv a year. Medical societies consider higher and lower dose tests to be above 10 mSv and below 3 mSv, respectively. In 2010 the American Society of Nuclear Cardiology set a target of 9 mSv or less for the majority of tests.3
Professor Thompson said: “The majority of studies were in the high dose range back in 2009 and now most tests have a radiation dose that is about a third of the target. This is despite being referred a larger number of obese patients. In the last 2.5 years, 17% of patients have needed the large field of view camera as their average body mass index was 46 kg/m2 and they were simply too big for the small cameras.”
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