Computed tomographic angiography (CTA) is an important prognostic tool with regard to the detection of coronary artery stenoses. Both iodine delivery rate (IDR; the amount of iodine delivered to the patient per second) and iodine concentration are decisive factors in the opacification of arterial vessels.

There remains to be some debate in the literature about whether the use of high iodine concentration contrast media is beneficial compared to lower iodine concentrations.

To date, there have not been any studies comparing intracoronary attenuation using concentrated contrast media lower than 300 mg I/ml at coronary CTA. For a reliable comparison of CM with different iodine concentrations, adapted injection protocols insuring an identical IDR (in g iodine per second) are mandatory. The investigators hypothesize that usage of lower iodine concentrations, while maintaining identical IDR and total iodine load, will result in comparable diagnostical intra-vascular attenuation in CTA.

To evaluate intravascular contrast enhancement and image quality in coronary CTA using different iodine concentrations ranging from 240 to 370 mg iodine per ml, administered with an identical IDR and total iodine load.

To describe the effect of iodine concentration and flow rates on contrast bolus characteristics, eg time to peak, bolus homogeneity, injection pressure and patient comfort.

Inclusion Criteria:

• Atypical or typical chest pain

Exclusion Criteria:

• Unstable angina
• Hemodynamic instability
• History of CAD
• Pregnancy
• Renal insufficiency (defined as glomerular filtration rate (GFR) <45ml/min or <60ml +diabetes
• HR > 90 bpm and the inability to receive beta-blockers and iodine allergy