1. A method for assisting in determination of the suitability of a patient for a scan of a heart of the patient in a resting phase of only one cardiac cycle of the patient's heart using an X-ray computer tomograph, the method comprising: recording an electrocardiogram of the patient; evaluating the electrocardiogram by predicting an occurrence time of at least an immediately following R wave based upon at least four immediately consecutive R waves of the electrocardiogram which were previously measured, and comparing the occurrence time with an actual measured occurrence time of the next R wave; and visualizing quality of the prediction qualitatively.