1. A method comprising: (a) placing an object to be imaged in a substantially uniform non-zero magnetic field B 0 ; (b) with the object positioned in the magnetic field B 0 , applying to the object a repeating sequence of (i) one or more RF pulses, (ii) one or more non-zero slice-selection field-gradient pulses, (iii) one or more phase-encoding field-gradient pulses, and (iv) one or more non-zero readout field-gradient pulses; (c) during at least a portion of each repetition cycle of the pulse sequence, applying to the object a non-zero modulating field gradient; (d) detecting and recording steady-state spin echo or gradient echo signals for multiple repetition cycles of the pulse sequence; and (e) extracting from the recorded steady-state echo signals a steady-state signal magnitude or a steady-state signal phase for each voxel of a complex-valued image of the object, wherein: (f) repetition time T R of the pulse sequence is less than the longitudinal relaxation time T 1 of the object; and (g) the modulating field gradient imparts spatial modulation of the steady-state signal phase and magnitude across the complex-valued image of the object along the direction of the modulating field gradient.