The invention relates to an imaging system for imaging a periodically moving object. An assigning unit (18) assigns ultrasound signals like A-lines to motion phases based on a provided phase signal, wherein an ultrasound images generation unit (19) generates several ultrasound images like gated M-mode images for the different motion phases based on the ultrasound signals assigned to the respective motion phase. A selecting unit (20) is used to select an ultrasound image from the generated ultrasound images, wherein a display unit (21) displays the selected ultrasound image. The selected ultrasound image corresponds therefore to a single motion phase only such that motion artifacts in the displayed ultrasound image are reduced. The imaging system is particularly useful for, for instance, monitoring cardiac ablation procedures.
