Study reveals low adoption of advice to reduce nuclear cardiology radiation exposure

Vienna, Austria – 9 May 2017: A study in 65 countries has revealed low adoption of
International Atomic Energy Agency recommendations to reduce nuclear cardiology
radiation exposure. The research is presented today at ICNC 2017 by Dr Edward
Hulten, a cardiologist at the Walter Reed National Military Medical Center,
Bethesda, USA.1

Nuclear cardiology uses small amounts of radioactive tracers which are injected into
the veins and taken up by the heart. A gamma camera images the radiation from the
tracer. The cardiac images are used to measure the heart size and function, identify
coronary heart disease, and predict the risk of a heart attack.

Dr Hulten said: “Nuclear cardiology is a key part of contemporary cardiology
management and around 15 to 20 million procedures are performed annually. It gives
information regarding diagnosis, prognosis, and the effects of therapeutic
interventions.”

“Concerns have been raised about tests, including nuclear cardiology, that expose
patients to ionising medical radiation,” he continued. “Medical radiation
potentially raises the lifetime risk of cancer which is important for all patients,
especially younger patients or when considering additional radiation over time from
further medical studies.”

A goal of 9 mSv or less radiation exposure per scan was recommended by the American
Society of Nuclear Cardiology (ASNC) in 2010. It was noted in a 2016 International
Atomic Energy Agency (IAEA) nuclear cardiology guideline but not formally endorsed
as a recommendation.2, 3

The IAEA developed eight quality metrics for responsible radiation use in nuclear
cardiology: avoiding thallium 201 stress testing, avoiding dual isotope testing,
avoiding too much technetium-99m and thallium 201, using stress only imaging, use of
camera technologies to reduce dose, use of weight based dosing strategies for
technetium-99m, and avoiding inappropriate dosing that can lead to “shine-through”
artefacts.

The IAEA Nuclear Cardiology Protocols Study (INCAPS) assessed adherence to the eight
quality metrics. The present analysis investigated which metrics were most helpful
in meeting the ASNC’s 9 mSv target. During one week in 2013, 308 nuclear cardiology
laboratories were studied in 65 countries in Africa, Asia, Europe, Latin America,
North America, and Oceania.

The survey included 7 911 nuclear cardiology scans. There was significant
variability in adherence to the quality metrics across laboratories and regions.
There was low adherence overall, with the majority of sites implementing less than
half of the quality metrics.

When the researchers performed multivariable logistic regression analysis, they
found that the practices most strongly associated with achieving a 9 mSv or less
scan were the use of stress or rest only imaging, avoiding thallium, and use of
camera technologies to reduce radiation dose.

Dr Hulten said: “When the 9 mSv recommendation was made in 2010 it was suggested
that it should be achieved in 50% of scans by 2014. The INCAPS survey shows that
there is still work to do. It is possible to reduce radiation exposure with existing
techniques. Cadmium zinc telluride (CZT) cameras are more sensitive and allow for
reduced dose scanning. With certain tracers you can achieve 1 mSv or less. But some
scans use more than 30 mSv, so there is huge variability.”

Not every site has all of the hardware and technology, said Dr Hulten, so the first
step is to look at what is possible within each lab. He said: “There are
improvements every lab can make regardless of money – for example multiple position
imaging, weight based dosing and stress only techniques. They do require adapting
existing workflows which takes leadership but they should be feasible in most labs.”

He added: “Eventually cameras wear out and perhaps the decision on a replacement
could factor in a reduced radiation dose which also lowers false positive tests and
has the potential to reduce lab costs.”

Dr Hulten concluded: “The INCAPS survey is a crucial step towards improving patient
care in the field of nuclear cardiology by quantifying worldwide adherence to best
practices. Any test involving ionising radiation will increase cancers within a
population but the risk must be weighed against the benefit of gaining information
about heart disease. The 9 mSv goal is achievable, and the lower the better.”