Computed tomography to diagnose coronary artery disease: a reduction in radiation dose increases applicability

Abstract

Aim: To assess the effects of dose-saving algorithms on the radiation dose in an established computed tomography coronary angiography (CTCA) clinical service.

Materials and methods: A 3 year retrospective analysis of all patients attending for a clinically indicated CTCA was performed. The effective dose was calculated using a cardiac-specific conversion factor [0.028 mSv(mGy·cm)(-1)]. Patients were stratified by the advent of new scanning technology and dose-saving protocols.

Results: Between September 2007 and August 2010, 1736 examinations were performed. In the first 6 months, 150 examinations were performed with a mean effective dose of 29.6 mSv (99% CI 26.6-33 mSv). In March 2008 prospective electrocardiogram (ECG) gating was installed; reducing the effective dose to 13.6 mSv (99% CI 12.5-14.9 mSv). In March 2009, the scanner parameters were set to a minimal exposure time and 100 kV in patients with a body mass index (BMI) of <30. This reduced the mean dose to 7.4 mSv (99% CI 6.8-8 mSv). For the final six months the mean radiation dose for a cardiac scan was 5.9 mSv (99% CI 5.4-6.5 mSv) this figure incorporates all examinations performed irrespective of the protocol used.

Conclusion: With the implementation of evidence-based protocols, the effective dose from cardiac CT has significantly reduced. As CTCA services develop dose-saving algorithms should be adopted to keep the radiation dose as low as reasonably practical.