Impact of iodine concentration and iodine delivery rate on contrast enhancement in coronary CT angiography: a randomized multicenter trial (CT-CON).

Abstract

To compare the effect of contrast medium iodine concentration on contrast enhancement, heart rate, and injection pressure when injected at a constant iodine delivery rate in coronary CT angiography (CTA). One thousand twenty-four patients scheduled for coronary CTA were prospectively randomized to receive one of four contrast media: iopromide 300mg I/ml, iohexol 350mg I/ml, iopromide 370mg I/ml, or iomeprol 400mg I/ml. Contrast media were delivered at an equivalent iodine delivery rate of 2.0g I/s. Intracoronary attenuation was measured and compared (per vessel and per segment). Heart rate before and after contrast media injection was documented. Injection pressure was recorded (n = 403) during contrast medium injection and compared between groups. Intracoronary attenuation values were similar for the different contrast groups. The mean attenuation over all segments ranged between 384HU for 350mg I/ml and 395HU for 400mg I/ml (p = 0.079). Dose-length product (p = 0.8424), signal-to-noise ratio (all p > 0.05), time to peak (p = 0.324), and changes in heart rate (p = 0.974) were comparable between groups. The peak pressures differed: 197.4psi for 300mg I/ml (viscosity 4.6mPas), 229.8psi for 350mg I/ml (10.4mPas), 216.1psi for 370mg I/ml (9.5mPas), and 243.7psi for 400mg I/ml (12.6mPas) (p < 0.0001). Intravascular attenuation and changes in heart rate are independent of iodine concentration when contrast media are injected at the same iodine delivery rate. Differences in injection pressures are associated with the viscosity of the contrast media. • The contrast enhancement in coronary CT angiography is independent of the iodine concentration when contrast media are injected at body temperature (37°C) with the same iodine delivery rate. • Iodine concentration does not influence the change in heart rate when contrast media are injected at identical iodine delivery rates. • For a fixed iodine delivery rate and contrast temperature, the viscosity of the contrast medium affects the injection pressure.