Reduced iodine dose in coronary CT angiography by combining low tube voltage CT with iterative reconstruction

Purpose To evaluate image quality of a study protocol with reduced iodine dose and a combination of low tube voltage CT acquisition and iterative reconstruction (IR). Materials Two minipigs were scanned to compare a study protocol with low tube voltage - low iodine concentration (100kVp, 200mgI/ml) and iterative reconstruction (ASiR-60%) towards a standard of care protocol (120kVp, 320mgI/ml) with filtered back-projection. All scans were performed with constant injection protocol (speed 3ml/s, volume 1.5ml/kg, scan delay 30s) and equal radiation dose. CT-value and signal-to-noise-ratio (SNR) were measured in the right coronary artery (RCA), left anterior descending coronary (LAD) and left circumflex artery (LCx). Two expert readers scored overall image quality, vessel sharpness, image noise and artifacts on a five point scale. Statistics were performed by Mann-Whitney U test and Chi-square analysis. Results The study protocol did not result in inferior CT-signal and SNR. The standard RCA signal (307 ± 48 HU) was not significant different (p = 0.15) from the study protocol (258 ± 31 HU). Similar results were observed for SNR (p = 0.57), with comparable results between the standard (SNR 7.0 ± 2.5) and study protocol (SNR 8.7 ± 2.5). Expert reading confirmed these findings, showing no difference (all p-values > 0.12) between the standard (average score 4.2) and the study protocol (average score 3.9) for all evaluated parameters. All images were considered to be of at least acceptable diagnostic quality. Conclusion The combined use of reduced tube voltage with iterative reconstruction allows a marked reduction in total iodine dose without impairing image quality.