1. A magnetic resonance imaging method for monitoring motion of a part of an object to be imaged, which motion is repetitive in successive motion cycles, said method comprising: receiving a motion signal indicative of the motion cycle of the portion of the object to be imaged; applying pulse and gradient sequences to the object during successive motion cycles, triggered by said motion signal, for producing stimulated echo magnetic resonance signals in the part of the object during a plurality of different phases in the motion cycle; and using the stimulated echo magnetic resonance signals produced during at least one of said phases in successive motion cycles, forming at least one image of the object; wherein said pulse and gradient sequences comprise a tagging section for producing a tagging pattern and an imaging section comprising successive first, second, third and further radio frequency pulses which are arranged for generating said stimulated echo resonance signals after said third and further radio frequency pulses, said third and further pulses being combined with slice selective gradients, phase encoding gradients and readout gradients so as to form imaging subsequences, which are repeated in the successive motion cycles with different time integrals over the phase encoding gradients.