An imaging system for imaging a periodically moving object comprising a tissue wall, the imaging system comprising: - an ultrasound signals providing unit (13, 16) for providing ultrasound signals being A-lines of the tissue wall for different times, - a phase signal providing unit for providing a phase signal being indicative of motion phases of a periodic movement of the object at the different times, - an assigning unit for assigning the A-lines to the motion phases based on the provided phase signal, - an ultrasound images generation unit for generating several ultrasound images being M-mode images for the different motion phases, wherein an M-mode image for a motion phase is generated based on the A-lines assigned to the respective motion phase, - a selecting unit for selecting an ultrasound image from the generated ultrasound images, wherein the selecting unit is adapted to determine selection values for the generated ultrasound images, wherein a selection value is determined based on the image values of the respective ultrasound image, and to apply selection rules to the selection values for selecting the ultrasound image from the generated ultrasound images, said selection values being at least one of the following: - a first distance value being indicative of a distance between a sensing probe used for measuring the ultrasound signals and the tissue wall, - a wall thickness value being indicative of a thickness of the tissue wall, - a transmurality value being indicative of a part of the tissue wall having been influenced by the application of energy, - a second distance value being indicative of a distance between the tissue wall and an element behind the tissue wall, and - a gas formation value being indicative of an amount of gas formed in the tissue wall, and - a display unit for displaying the selected ultrasound image. - an ultrasound signals providing unit (13, 16) for providing ultrasound signals being A-lines of the tissue wall for different times, - a phase signal providing unit for providing a phase signal being indicative of motion phases of a periodic movement of the object at the different times, - an assigning unit for assigning the A-lines to the motion phases based on the provided phase signal, - an ultrasound images generation unit for generating several ultrasound images being M-mode images for the different motion phases, wherein an M-mode image for a motion phase is generated based on the A-lines assigned to the respective motion phase, - a selecting unit for selecting an ultrasound image from the generated ultrasound images, wherein the selecting unit is adapted to determine selection values for the generated ultrasound images, wherein a selection value is determined based on the image values of the respective ultrasound image, and to apply selection rules to the selection values for selecting the ultrasound image from the generated ultrasound images, said selection values being at least one of the following: - a first distance value being indicative of a distance between a sensing probe used for measuring the ultrasound signals and the tissue wall, - a wall thickness value being indicative of a thickness of the tissue wall, - a transmurality value being indicative of a part of the tissue wall having been influenced by the application of energy, - a second distance value being indicative of a distance between the tissue wall and an element behind the tissue wall, and - a gas formation value being indicative of an amount of gas formed in the tissue wall, and - a display unit for displaying the selected ultrasound image. - a first distance value being indicative of a distance between a sensing probe used for measuring the ultrasound signals and the tissue wall, - a wall thickness value being indicative of a thickness of the tissue wall, - a transmurality value being indicative of a part of the tissue wall having been influenced by the application of energy, - a second distance value being indicative of a distance between the tissue wall and an element behind the tissue wall, and - a gas formation value being indicative of an amount of gas formed in the tissue wall, and - a display unit for displaying the selected ultrasound image.