The feasibility of reduced dose of contrast agent dependent on patients' heart rate in coronary CT angiography

Objective To evaluate the feasibility of low dose contrast material administration tailored by patients' heart rate (HR) in coronary computed tomography angiography (CCTA) using dual-source CT . Methods A total of seventy-seven patients were prospectively enrolled into this study. According to HR, all subjects were divided into low HR group (Group S, HR ≤ 75 bpm) and high HR group (Group H, HR> 75 bpm). There was no significant difference in the age and weight between two groups. The injection rate and volume of contrast were 3.8 ml/s and 0.7 ml/kg in Group S; 5.0 ml/s and 0.9 ml/kg in Group H, respectively. The CT values of ascending aorta, right coronary artery, left main coronary artery and the lower epicardial fat were measured and compared between two groups. The imaging noise were measured and signal noise ratio (SNR), contrast noise ratio (CNR) were also calculated. Furthermore, image quality (1 to 3, excellent to non-assessable) was compared between the two groups. The dose of contrast material and objective indexes were analyzed by t test, and the subjective indexes were analyzed using Mann-whitney U test. Results The dose of contrast material was (43±6) ml in Group S and (59±8) ml in Group H, and there was a significant difference between two groups (t= 9.647, P 0.05).The average subjective image quality score of two groups ranged from 1 to 2 and the distribution of different scores was score 1 (16 vs. 35) and score 2 (17 vs. 9). There was a significant difference between the two groups (U= -2.834, P= 0.005). Conclusion The injection protocol of contrast material tailored by patients' heart rate can significantly reduce contrast material dose without compromising the image quality. Key words: Contrast media; Coronary; Tomography, X-ray computed