The objective of this study is to compare radiation dose of a 100kV scan protocol to the standard 120kV scan protocol. We hypothesize that the 100kV scan protocol is associated with a reduction in dose estimates of at least 20%, while the diagnostic image quality is not inferior.

Secondary endpoints of the study include quantitative image quality parameters, diagnostic accuracy for 120 vs.100kV studies compared to invasive angiography in patients who underwent subsequent invasive coronary angiography

All patients scheduled for a coronary CT scan are screened for inclusion and exclusion criteria. Patients are included if they have stable sinus rhythm (heart rate <100 bpm) and a body weight < 90 kg or a body mass index (BMI) < 30. Informed signed consent is obtained from these patients and the CT scan is prepared. After topogram scan and the native scan for Ca-Scoring, patients are randomized in two groups with the use of sealed envelopes. After that contrast-enhanced coronary CT angiography is performed with the 120kV- or 100kV-protocol.

The CT examination is evaluated by two experienced investigators on a per-vessel basis and all results and study-related data are collected in a dedicated database. For assessment of image quality, a previously established 4-point score system is used and quantitative image quality parameters are measured.

A 30 day follow-up after the CT examination aims to evaluate if patients underwent invasive coronary angiography or were scheduled for a myocardial stress / perfusion test (such as stress-echocardiography, myocardial scintigraphy or stress perfusion imaging by MRI).

Inclusion Criteria:

• patients with an indication for a coronary CT angiography (planned evaluation of the coronary arteries)
• stable sinus rhythm
• patient weight < 90kg or body mass index < 30 kg/m2
• signed informed consent

Exclusion Criteria:

• non-ECG triggered studies
• non-coronary CTA studies, e.g. bypass graft CTAs, pre- or post EP studies, CABG planning studies