Image quality in reduced-dose coronary CT angiography

Area of Science:

• Cardiovascular Imaging
• Radiology
• Medical Physics

Background:

• Growing concerns over radiation-induced cancer risk necessitate reduced-dose protocols for coronary computed tomography angiography (CCTA).
• Previous comparisons of full-dose and reduced-dose CCTA were inconclusive due to differing patient cohorts.

Purpose of the Study:

• To compare the diagnostic performance and image quality of a new low-dose CCTA protocol against a standard full-dose protocol.
• To evaluate the impact of an 80% radiation dose reduction on CCTA image quality and diagnostic accuracy.

Main Methods:

• A prospective electrocardiogram-gated acquisition was performed on 70 patients with intermediate coronary artery disease (CAD) probability using both standard and low-dose CCTA protocols.
• The low-dose protocol utilized an increased phase window (75% of R-R interval) compared to the standard protocol (10% of R-R interval) on a 320-detector row CT scanner.
• Tube voltages of 120/100 kV were used for both protocols.

Main Results:

• Despite an 80% mean dose reduction (4.9 to 0.98 mSv), visual image quality was not significantly affected.
• Contrast level, image noise, and contrast-to-noise ratio (CNR) were similar between the standard and low-dose protocols.
• A strong correlation between image quality and heart rate variability was observed with the low-dose protocol (r = -0.58, P = .01), unlike the full-dose protocol (r = -0.07, P = .77).

Conclusions:

• An 80% dose reduction in CCTA using a prospective electrocardiogram-gated acquisition generally does not compromise image quality of the coronary vasculature.
• The enhanced performance of the low-dose protocol is attributed to an increased phase window, which improves image quality at the expense of increased sensitivity to heart rate variability.