1. In a method for forming a projection image of the NMR activity of a selected region of a volume the steps of: exciting the selected region of the volume with a region-selecting excitation using a magnetic gradient having a component in the projection direction; exciting a sequence of planar sections which are parallel to the projection direction and perpendicular to the projection image; receiving signals from those regions which have experienced both excitations representing projections in solely one direction; and processing the received signals to form the projection image of the selected region of the volume.