A first performance evaluation of a dual-source CT (DSCT) system is presented. The system features two X-ray tubes and two corresponding detectors mounted on a rotating gantry with a 90-degree angular offset. The system concept is introduced, along with its implications for ECG-controlled cardiac CT and general radiology. Phantom scans are used to evaluate temporal and spatial resolution. First patient scans demonstrate the performance of DSCT for ECG-gated cardiac imaging, and initial results using a dual-energy acquisition mode are shown. With ECG-gated single-segment reconstruction, the DSCT system provides 83 ms temporal resolution independent of the patient's heart rate for coronary CT angiography (CTA) and evaluation of basic functional parameters. With dual-segment reconstruction, the mean temporal resolution is 60 ms (minimum 42 ms) for advanced functional evaluation. The z-flying focal spot technique allows 0.4 mm cylinders to be resolved at all heart rates. First clinical experience shows increased robustness for imaging patients with high heart rates. The dual-energy acquisition mode enables automatic separation of bones and iodine-filled vessels. Keywords: Computed tomography · Cardiac CT · CT technology · Dual-source CT · Multidetector-row CT The introduction discusses the current status of ECG-gated cardiac CT. Multidetector-row CT (MDCT) systems were introduced in 1999, enabling motion-free imaging of the heart in the mid- to end-diastolic phase at slow to moderate heart rates. Early studies showed the potential of MDCT to detect and characterize coronary plaques. However, challenges such as motion artifacts, limited spatial resolution, and long breath-hold times remained. Sixteen-slice CT systems improved spatial and temporal resolution, reducing examination times. Sixty-four-slice CT systems further improved resolution and are a significant step in integrating coronary CTA into routine clinical algorithms. Despite improvements, motion artifacts remain a major challenge. Some authors still recommend beta-blockers to reduce heart rate. However, even with 64-slice CT systems, some heart rates remain problematic. The authors observed good image quality in diastole for patients with heart rates <65 bpm and good image quality in end systole for patients with heart rates >75 bpm, yet image quality in the intermediate region was compromised. Further-improved temporal resolution of less than 100 ms at all heart rates is desirable to eliminate the need for heart-rate control.A first performance evaluation of a dual-source CT (DSCT) system is presented. The system features two X-ray tubes and two corresponding detectors mounted on a rotating gantry with a 90-degree angular offset. The system concept is introduced, along with its implications for ECG-controlled cardiac CT and general radiology. Phantom scans are used to evaluate temporal and spatial resolution. First patient scans demonstrate the performance of DSCT for ECG-gated cardiac imaging, and initial results using a dual-energy acquisition mode are shown. With ECG-gated single-segment reconstruction, the DSCT system provides 83 ms temporal resolution independent of the patient's heart rate for coronary CT angiography (CTA) and evaluation of basic functional parameters. With dual-segment reconstruction, the mean temporal resolution is 60 ms (minimum 42 ms) for advanced functional evaluation. The z-flying focal spot technique allows 0.4 mm cylinders to be resolved at all heart rates. First clinical experience shows increased robustness for imaging patients with high heart rates. The dual-energy acquisition mode enables automatic separation of bones and iodine-filled vessels. Keywords: Computed tomography · Cardiac CT · CT technology · Dual-source CT · Multidetector-row CT The introduction discusses the current status of ECG-gated cardiac CT. Multidetector-row CT (MDCT) systems were introduced in 1999, enabling motion-free imaging of the heart in the mid- to end-diastolic phase at slow to moderate heart rates. Early studies showed the potential of MDCT to detect and characterize coronary plaques. However, challenges such as motion artifacts, limited spatial resolution, and long breath-hold times remained. Sixteen-slice CT systems improved spatial and temporal resolution, reducing examination times. Sixty-four-slice CT systems further improved resolution and are a significant step in integrating coronary CTA into routine clinical algorithms. Despite improvements, motion artifacts remain a major challenge. Some authors still recommend beta-blockers to reduce heart rate. However, even with 64-slice CT systems, some heart rates remain problematic. The authors observed good image quality in diastole for patients with heart rates <65 bpm and good image quality in end systole for patients with heart rates >75 bpm, yet image quality in the intermediate region was compromised. Further-improved temporal resolution of less than 100 ms at all heart rates is desirable to eliminate the need for heart-rate control.