Imaging Radiation Reduced with Contemporary Tools

Modified protocols, improved technology, and post processing software can slash nuclear cardiology radiation doses, according to a new study.

Researchers at Saint Luke's Mid America Heart Institute conducted a study involving 18,162 single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) studies performed at all four of the Saint Luke's Mid America Heart Institute nuclear cardiology laboratories from 1 January 2009 to 30 September 2016. The researchers examined the effect of modified protocols, which used radiotracers only in stress tests, and with Technetium tracers used instead of thallium, which reduces two-thirds of the radiation dose.

In addition, they also examined the effect of using a new generation of camera systems with a smaller field of view, which are more sensitive and need less radiotracer injected into the body. The camera systems are also equipped with advanced processing, which enhances the images and requires less radiation and shorter acquisition times. The results showed that average radiation dose fell from 17.9 mSv in 2009 to 7.2 mSv in 2016, and the median dose dropped from 10.2 mSv to 2.5 mSv. The study was published in the May 2017 issue of JACC: Cardiovascular Imaging.

“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,” said lead author Professor Randall Thompson, MD. “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.”

SPECT MPI is a non-invasive test performed to evaluate the presence and severity of coronary artery disease (CAD) by detecting flow-limiting disease, risk-stratifying patients, and assessing and quantifying patient risk. It is most frequently used for perioperative cardiovascular evaluation and following chest pain. Recent studies have shown that noninvasive SPECT scans of cardiac vessels are better at spotting CAD than commonly prescribed exercise stress tests, but are still inferior to coronary CT angiography (CTA).