A method for distinguishing between gas and liquid phases in a multi-phase fluid flowing in a pipe without using time-of-flight measurements, comprising: a) providing a measurement and analysis magnetic resonance module through which the multi-phase fluid flows; b) providing a pre-polarization module through which the multi-phase fluid flows before entering the magnetic resonance module; c) flowing the multi-phase fluid through the pre-polarization module and the magnetic resonance module; d) as the multi-phase fluid flows through the magnetic resonance module; applying to the multi-phase fluid a radio-frequency pulse sequence at least once in the presence of a magnetic field gradient and at least once in the absence of a magnetic field gradient and measuring the intensity of a pre-determined number of spin echoes that are produced by the radio-frequency pulse sequence; e) using a first calibration between the ratio of slope and intercept of the measured spin echoes and flow velocity for at least one non-gas phase with the magnetic field gradient applied to determine the flow velocity of that non-gas phase; f) using a second calibration of the signal intensity of the non-gas phases as a function of flow velocity, with and without magnetic field gradients applied, to correct the gradient-induced attenuation of the non-gas signal and to calculate a gradient-corrected signal intensity of the non-gas phase; g) subtracting the gradient-corrected signal intensity of the non-gas phase from the magnetic resonance signal of the multi-phase fluid measured at step d) to determine a signal that corresponds to the gas phase; and h) determining the volumetric fraction and flow velocity of the gas phase from the gas signal determined in step g), wherein using a flow rate calibration for pure gas in conjunction with the slope and intercept of the gas signal from step g) to determine gas flow velocity. a) providing a measurement and analysis magnetic resonance module through which the multi-phase fluid flows; b) providing a pre-polarization module through which the multi-phase fluid flows before entering the magnetic resonance module; c) flowing the multi-phase fluid through the pre-polarization module and the magnetic resonance module; d) as the multi-phase fluid flows through the magnetic resonance module; applying to the multi-phase fluid a radio-frequency pulse sequence at least once in the presence of a magnetic field gradient and at least once in the absence of a magnetic field gradient and measuring the intensity of a pre-determined number of spin echoes that are produced by the radio-frequency pulse sequence; e) using a first calibration between the ratio of slope and intercept of the measured spin echoes and flow velocity for at least one non-gas phase with the magnetic field gradient applied to determine the flow velocity of that non-gas phase; f) using a second calibration of the signal intensity of the non-gas phases as a function of flow velocity, with and without magnetic field gradients applied, to correct the gradient-induced attenuation of the non-gas signal and to calculate a gradient-corrected signal intensity of the non-gas phase; g) subtracting the gradient-corrected signal intensity of the non-gas phase from the magnetic resonance signal of the multi-phase fluid measured at step d) to determine a signal that corresponds to the gas phase; and h) determining the volumetric fraction and flow velocity of the gas phase from the gas signal determined in step g), wherein using a flow rate calibration for pure gas in conjunction with the slope and intercept of the gas signal from step g) to determine gas flow velocity.