1. A magnetic resonance scanner, comprising: main magnet coils, which generate a B 0 field; gradient windings and a gradient coil controller, which generates gradients across the B 0 field; one or more RF coils, or one of more local RF coils, which transmit B 1 pulses and receive magnetic resonance signals; an RF transmitter, which transmits B 1 pulses to the RF coils to excite and manipulate resonance; an RF receiver, which demodulates received resonance signals into imaging data lines; a sequence controller connected to the gradient controller, and the RF transmitter, the sequence controller being configured to: control the RF transmitter and the gradient coil controller to implement an interleaved multi-slice 2D imaging sequence, which in each of a plurality of repetitions (TRs) generates a first and second navigation data lines and at least one image data line for each of a plurality of slices; and one or more processors configured to: reconstruct the first navigation data lines from the plurality of slices into a first navigation projection image; reconstruct the second navigation data lines from the plurality of slices into a second navigation projection image; and compare successive navigation projection images to detect and adjust for 3D motion; and a display device, which displays reconstructed 2D slices.