Abstract: A method of determining a multi-dimensional distribution function of fluid types in a sample comprising: (i) applying a sequence of radio frequency pulses to the sample, each pulse having a predetermined phase, the sequence including: a diffusion encoding portion followed by a series of 180-degree refocusing pulses, wherein the diffusion encoding portion comprises repeating blocks of pulses, where the pulses in each block are separated by an interval time of 6, and the blocks themselves by a time delay; (ii) measuring a stimulated echo signal from the sample; (iii) repeating steps (i) to (ii) one or more times with constant 6 to obtain a phase-cycled data set of stimulated echo signal measurements, wherein for each repetition the phase of at least one of the RF pulses is shifted by a predetermined offset; (iv) repeating steps (i) to (iii) one of more times with different 6 values to obtain a series of phase-cycled data sets; and (v) analysing the series of phase-cycled data sets to provide a multi-dimensional