Reducing radiation dose during ECG-triggered coronary CTA exams

Reduced or no "padding" during ECG-triggered coronary CT angiography (CTA) results in a substantial reduction in radiation dose without affecting image quality and interpretability, according to a study in the April issue of the American Journal of Roentgenology. ECG-triggered coronary CTA is a common, minimally invasive procedure that is used to evaluate blockages in the coronary arteries.

"During ECG-triggered coronary CTA, there is a mandatory minimum time that the scanner must be on during each heartbeat, and there is typically extra time added before and after this which is referred to as 'padding'," said Troy LaBounty, MD, lead author of the study. "By reducing or eliminating 'padding' we shorten the scanner 'on time' and lower the radiation dose," said LaBounty.

The study was performed at three different sites, including Weill Cornell Medical College in New York, NY; Fairfax Radiology Associates in Fairfax, VA; and the University of British Columbia in Vancouver, Canada. It included 886 patients who underwent ECG-triggered coronary CTA with a padding duration of either 0, 1–99, or 100–150 milliseconds.

"Results showed that increased padding was associated with a greater radiation dose (45 percent increase per 100-millisecond increase in padding)," said LaBounty. No difference in image interpretability was seen between the three groups.

"Our data show that use of minimal or no padding can result in reduced radiation dose with preserved image interpretability in examinations of patients with excellent heart rate control," he said.

"Concerns regarding the radiation exposure associated with coronary CTA have resulted in the development of new techniques to reduce radiation dose. Padding duration can be adjusted on a patient by patient basis, and decreased padding should be considered in dose reduction strategies for patients with excellent heart rate control," said LaBounty.

(Source: Roentgen Ray Society: American Journal of Roentgenology: March 2010)