To image flowing materials, magnetic resonance preconditioning pulses are applied in an upstream region (28). For scanning a subject, an RF pulse calibration sequence is performed by generating a corresponding magnetic resonance data line (361, . . . , 36n) in each of a plurality of slices (401, . ....http://www.google.de/patents/US6618609?utm_source=gb-gplus-sharePatent US6618609 - Flow adaptive guided determination of imaging parameters for 3D magnetic resonance angiography