Dose performance and image quality: dual source CT versus single source CT in cardiac CT angiography.

OBJECTIVE: To evaluate dose performance and image quality of 64-slice dual source CT (DSCT) in comparison to 64-slice single source CT (SSCT) in cardiac CT angiography (CTA).

METHODS: 100 patients examined by DSCT and 60 patients scanned by SSCT were included in this study. Objective indices such as image noise, contrast-to-noise ratio and signal-to-noise ratio were analyzed. Subjective image quality was assessed by two cardiovascular radiologists in consensus using a four-point scale (1=excellent to 4=not acceptable). Estimation of effective dose was performed on the basis of dose length product (DLP).

RESULTS: At low heart rates (<70 bpm), image quality of SSCT was equivalent to that of DSCT (P>0.05), but, at high heart rates (>70 bpm), DSCT provided robust image quality (P<0.05). The average effective dose of SSCT was 9.3+/-0.9 mSv at low heart rates (<70 bpm) while, the average estimated effective doses of DSCT were 9.1+/-1.3 mSv, 8.3+/-1.1 mSv, 7.9+/-1.1 mSv, 6.9+/-0.7 mSv, and 5.9+/-1.3 mSv, corresponding to heart rates of 50-59 bpm, 60-69 bpm, 70-79 bpm, 80-89 bpm, and 90-100 bpm.

CONCLUSION: For cardiac CTA, both DSCT and SSCT can get good image quality at low heart rates (<70 bpm) with a similar radiation dose, but, at high heart rates (>70 bpm), DSCT is able to provide robust diagnostic image quality at doses far below that of SSCT.