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



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 300 mg I/ml, iohexol 350 mg I/ml, iopromide 370 mg I/ml, or iomeprol 400 mg I/ml. Contrast media were delivered at an equivalent iodine delivery rate of 2.0 g 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 384 HU for 350 mg I/ml and 395 HU for 400 mg 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: 197.4 psi for 300 mg I/ml (viscosity 4.6 mPa s), 229.8 psi for 350 mg I/ml (10.4 mPa s), 216.1 psi for 370 mg I/ml (9.5 mPa s), and 243.7 psi for 400 mg I/ml (12.6 mPa s) (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.

Key Points

• 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.

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Adverse events


American Heart Association


Analysis of variance


Beats per minute


Computed tomography angiography


Circumflex artery


Dose-length product




Hounsfield units


Iodine delivery rate


Interquartile range


Left anterior descending artery


Left main coronary artery


Modification of Diet in Renal Disease


Right coronary artery


Region of interest


Standard deviation


Signal-to-noise ratio


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Dr. Alexander Boreham (co.medical, Berlin, Germany) is acknowledged for medical writing.


This study has received unrestricted funding from Bayer (Germany).

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Corresponding author

Correspondence to Koen Nieman.

Ethics declarations


The scientific guarantor of this publication is Koen Nieman.

Conflict of interest

Koen Nieman declared institutional research support from Siemens Healthineers, GE Healthcare, Bayer Healthcare, and Heartflow Inc.

Joachim E. Wildberger declared institutional research grants from AGFA Healthcare, Bayer Healthcare, GE Healthcare, Philips Healthcare, Siemens Healthcare, and Optimed as well as personal disclosures (Speaker’s bureau) from Bayer and Siemens.

Marco Das declared institutional research grants at the time of the study from Bayer Healthcare, Philips Healthcare, and Siemens Healthcare as well as personal disclosures (Speaker’s bureau) from Bayer and Siemens and Cook Medical.

Andrea Laghi declared personal disclosure (Speaker’s bureau) from Bayer, Bracco, GE Healthcare, Merck, and Bristol-Myers Squibb.

The other authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.

Statistics and biometry

One of the authors has significant statistical expertise.

Informed consent

Written informed consent was obtained from all subjects (patients) in this study.

Ethical approval

Institutional Review Board approval was obtained.


• prospective.

• randomized controlled trial.

• multicenter study.

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Rengo, M., Dharampal, A., Lubbers, M. et al. Impact of iodine concentration and iodine delivery rate on contrast enhancement in coronary CT angiography: a randomized multicenter trial (CT-CON). Eur Radiol 29, 6109–6118 (2019).

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  • Contrast media
  • Computed tomography angiography
  • Coronary disease
  • Randomized controlled trial