Effects of the Saline Flush on High-pitch CT Coronary Angiography on Third-generation Dual-source CT System

Objective To preliminarily investigate and optimize the saline flush effects to the image quality (IQ)and effective scan rate of high-pitch CT coronary angiography (CCTA)using ultra-low contrast media (CM)protocols on third-generation dual-source CT (DCST). Methods Sixty-eight consecutive patients with suspected or known coronary artery disease (CAD)were recruited and underwent prospective high-pitch CCTA on third-generation DSCT with automatic tube voltage selection (70-80 kV)based ultra-low CM protocols:18 ml(3.0 ml/s) for 70 kV and 21 ml (3.0 ml/s) for 80 kV. All the patients were randomly divided in to two groups:Group A(n=31)with the saline flush of 3.0 ml/s(40 ml) and Group B (n=37)with the saline flush of 4.0 ml/s(40 ml). The baseline data,risk factors,quantitative image quality (IQ),qualitative IQ results,and effective dose (ED)were evaluated and compared. Results There was no significant difference in ED between two groups [(0.36±0.12)mSv vs. (0.37±0.13)mSv;t=-0.40,P=0.70]. The average ED in all patients was (0.43±0.28)mSv. However,the contrast to noise ratio (CNR) of right coronary artery distal segment in Group A was significantly higher than that in Group B(76.04±62.46 vs. 43.96±26.94;t=2.67,P=0.01) and the CNR of left circumflex artery proximal segment in Group A was significantly higher than that in Group B(69.60±43.13 vs. 44.08±24.08;t=2.96,P=0.01). No other significant difference was found in terms of baseline characteristics,and objective image quality (all P>0.05). Subjective IQ showed no significant difference between these two groups (χ²=2.53,P=0.47). Conclusion Under high-pitch CCTA using ultra-low CM protocols [18-21 ml (3.0 ml/s)]on third-generation DCST,the saline flush at a flow rate of 3.0 ml/s can achieve satisfactory IQ and effective scan rate.