MUNICH – The median radiation dosage received by patients worldwide undergoing coronary CT angiography fell by 78% from 2007 to 2017, according to a prospective study with more than 4,500 patients.
This substantial drop in radiation occurred with a steady rate of nondiagnostic CT scans, less than 2% in both 2007 and 2017.
“Given the high diagnostic accuracy and the low radiation dose, coronary CT angiography should be considered as a first-line diagnostic test,” Jörg Hausleiter, MD, said at the annual congress of the European Society of Cardiology.
The results also showed a huge disparity in the range of radiation doses used worldwide, with a 37-fold intersite variability in the median dose. This finding “underlines the need for further site-specific training and adaptation of contemporary cardiac scan protocols,” said Dr. Hausleiter, professor of medicine at the University of Munich Clinic. He suggested updated imaging guidelines on radiation levels, more educational sessions on how to perform coronary CT angiography, and actions by vendors to adjust their standard imaging protocols.
The Prospective Multicenter Registry on Radiation Dose Estimates of Cardiac CT Angiography in Daily Practice in 2017 (PROTECTION-VI) study included 4,502 patients from a total of 61 sites in 32 countries. At each participating site, investigators enrolled consecutive adults during a randomly selected month in 2017, with a median of 51 patients enrolled at each site undergoing diagnostic coronary CT angiography. Comparison data for 2007 came from a similar study run by Dr. Hausleiter and his associates at that time, with 1,965 patients undergoing coronary CT angiography (JAMA. 2009 Feb 4;301:500-7). In 2007, the median dose-length product of radiation for each scan was 885 mGy x cm, which corresponds to a radiation dose of about 12.4 mSv. In 2017, the median dose-length product was 195 mGy x cm, corresponding to a dose of about 2.7 mSv. By both measures the median dose dropped by roughly 78%.
A multivariate analysis identified three changes in the way clinicians obtained most of the CT scans during the two studied time periods that seemed to explain the drop in radiation dose. First, more scan protocols in 2017 used low tube potential; second, more protocols in 2017 used prospectively ECG-triggered axial high-pitch scans; and third, 2017 had increased use of iterative image reconstruction, Dr. Hausleiter said. Patient variables that had modest but significant links with increased radiation doses were higher body weight, higher heart rate, and no sinus rhythm.
Concurrently with Dr. Hausleiter’s talk at the congress, the results appeared in an article online (Euro Heart J. 2018 Aug 25. doi: 10.1093/eurheartj/ehy546).