Comparison of sequential and high-pitch-spiral coronary CT-angiography: image quality and radiation exposure

New protocols for coronary computed tomography angiography (CCTA) could lower the radiation dose for patients but influence the image quality. To compare image quality and radiation exposure in step-and-shoot CCTA and high-pitch spiral CCTA. Fifty-nine pairs of patients matched for weight, height, sex and heart rate were included in this study (74 m, 44 f, average age 60 years, age range 29-94 years). Step-and-shoot CCTA and high-pitch spiral CCTA was performed on a third generation dual-source CT in equally sized patient groups. The signal-to-noise ratio (SNR) in the ascending aorta and the coronary arteries were determined for each dataset. Image quality was rated using a five-point scale. We used the t-test for paired samples to compare SNR and effective dose, and the Wilcoxon test to compare image quality scores. Mean effective dose for the step-and-shoot protocol (4.15 ± 3.07 mSv) was significantly higher in comparison to the high-pitch spiral protocol (1.2 ± 0.69 mSv; p < 0.0001). Mean SNR was higher with the step-and-shoot protocol compared to the high-pitch spiral protocol in the aorta, in the left main and peripheral coronary arteries (p < 0.01), in the proximal right coronary artery (p = 0.027). Image quality scores were significantly better for the step-and-shoot protocol (p = 0.0003). Step-and-shoot CCTA has significantly better SNR and overall image quality compared to high-pitch spiral CCTA, but with a mean effective dose more than thrice as high.