A method of exciting nuclear spins in a body, the method comprising the steps of: (a) immerging said body in a static magnetic field (B 0) for aligning nuclear spins along a magnetization axis (z), said static magnetic field being substantially uniform over at least a volume of interest of said body; (b) exposing said body, or at least said volume of interest, to a time-varying magnetic field gradient having components (G x, G y, G z) directed along at least three non-coplanar directions (x, y, z) and to a radio-frequency non-selective pulse having a transverse polarization (B 1), whereby: said time-varying magnetic field gradient consists of a sequence of magnetic field gradient pulses and defines a three-dimensional trajectory in k-space constituted by straight segments linking discrete points (k T 1, k T 2,...), and said radio-frequency non-selective pulse having a transverse polarization comprises transverse radio-frequency subpulses (P 1, P 2,...) interleaved with said magnetic field gradient pulses, said radio-frequency subpulses deposit radio-frequency energy only in said discrete points of k-space, no radio-frequency non-selective pulse having a transverse polarization is applied simultaneously to said magnetic field gradient pulses the positions of said discrete points in k-space being determined, and the radio-frequency non-selective pulse having a transverse polarization being designed, for flipping said nuclear spins by a same predetermined flip angle, independently from their position within said volume of interest. (a) immerging said body in a static magnetic field (B 0) for aligning nuclear spins along a magnetization axis (z), said static magnetic field being substantially uniform over at least a volume of interest of said body; (b) exposing said body, or at least said volume of interest, to a time-varying magnetic field gradient having components (G x, G y, G z) directed along at least three non-coplanar directions (x, y, z) and to a radio-frequency non-selective pulse having a transverse polarization (B 1), whereby: said time-varying magnetic field gradient consists of a sequence of magnetic field gradient pulses and defines a three-dimensional trajectory in k-space constituted by straight segments linking discrete points (k T 1, k T 2,...), and said radio-frequency non-selective pulse having a transverse polarization comprises transverse radio-frequency subpulses (P 1, P 2,...) interleaved with said magnetic field gradient pulses, said radio-frequency subpulses deposit radio-frequency energy only in said discrete points of k-space, no radio-frequency non-selective pulse having a transverse polarization is applied simultaneously to said magnetic field gradient pulses the positions of said discrete points in k-space being determined, and the radio-frequency non-selective pulse having a transverse polarization being designed, for flipping said nuclear spins by a same predetermined flip angle, independently from their position within said volume of interest. said time-varying magnetic field gradient consists of a sequence of magnetic field gradient pulses and defines a three-dimensional trajectory in k-space constituted by straight segments linking discrete points (k T 1, k T 2,...), and said radio-frequency non-selective pulse having a transverse polarization comprises transverse radio-frequency subpulses (P 1, P 2,...) interleaved with said magnetic field gradient pulses, said radio-frequency subpulses deposit radio-frequency energy only in said discrete points of k-space, no radio-frequency non-selective pulse having a transverse polarization is applied simultaneously to said magnetic field gradient pulses the positions of said discrete points in k-space being determined, and the radio-frequency non-selective pulse having a transverse polarization being designed, for flipping said nuclear spins by a same predetermined flip angle, independently from their position within said volume of interest.