1. A method for operating a magnetic resonance tomography apparatus comprising: acquiring an overview slice image across an entirety of a subject to be examined in a selected slice; in said overview slice image, detecting a marking input of a first image region; in a control unit of a magnetic resonance tomography apparatus, electronically expanding said first image region in at least one phase coding direction, dependent on a geometry of said first image region, said overview slice image and respective positions of said overview slice image and said first image region relative to each other to designate a second image region that is expanded compared to said first image region; and with said control unit, acquiring oversampled magnetic resonance data from said second image region of said subject, that completely contains said first image region and that is free of foldovers in said first image region.