A recent study published in the Journal of the American Medical Association suggests that implementing techniques to reduce dose of radiation associated with cardiac computed tomography angiography (CCTA) exposes patients to less radiation and does not change the quality of the images. While CCTA has emerged as a potential noninvasive and cost-effective test used to rule out coronary ischemia in patients with chest pain, radiation dosage remains a concern.
The Michigan-based research team analyzed whether implementation of “best practice” interventions would reduce the amounts of radiation produced by the scans and whether there would be a reduction in image quality. The interventions chosen are basic to both older and newer CCTA machines. They enrolled 4995 patients at 15 imaging centers throughout Michigan that volunteered to take part in this nonrandomized controlled retrospective study for 1 year; 4862 patients had complete data available at the end of the year. Mean age of the patients was 57 and 53% of the patients were male. Most were overweight, with a mean body mass index (BMI) of 29.4. Interventions to reduce the dose of radiation included minimizing the longitudinal scan range; reducing the heart rate with beta-blockers; maximizing the use of electrocardiographic-gated tube current modulation; and decreasing the scan voltage in normal-weight patients. The first 2 months of the study were designated as the control group; months 3 to 10 were considered the intervention period, and months 11 and 12 were the follow-up period. The study provided education at each step in the imaging process, along with monitoring of patient preparation, imaging protocols, and image quality.
Compared with the control period, the median estimated radiation dose was reduced by 53.3% (P<0.001) by the follow-up period. There was also a significant increase in the number of patients who received the target dose, which was less than 15 millisieverts (mSv) (P<0.001).
During the course of the study, the most frequently effective radiation dose range decreased from a range of 25 to 29 mSv to a range of 5 to 10 mSv. The two most powerful predictors of achieving the target dose were the use of lower tube voltage and a site volume exceeding 30 scans per month (P<0.001 for both). Despite reduction in the radiation doses, there was no significant reduction in the proportion of diagnostic-quality scans, from 89% in the control period to 92% after the intervention (P=0.07).
The limitations to the study include its nonrandomized design, which does not allow for drawing conclusions regarding causality. In addition, since sites volunteered to take part in the study, the results might not be generalizable to sites less committed to the interventions. The authors call for additional multicenter studies to evaluate other technical advances and interventions that might reduce patient exposure to radiation, and emphasize that facilities should prepare in-depth training programs and utilize guidelines issued by specialty societies before implementing large-scale practice improvements.