Patent ID: 8212557

Claim:
A method for determining, in real time and without using time-of-flight measurements, individual component flow-rates in a multi-phase fluid flowing in a pipe, comprising the steps of: a) flowing the fluid through a magnetic resonance based apparatus comprising: a magnetic resonance module; and at least one pre-polarization module through which the fluid phases flow before entering the magnetic resonance module, wherein said pre-polarization module comprises a plurality of cylindrical segments that can be selectively combined so as to modify the effective length of the pre-polarization module, and wherein said at least one pre-polarization module includes a plurality of magnetic disks each comprising a Halbach-type magnet array, wherein said discs can be reoriented relative to each other so a to modify the effective polarization length to adjust the pre-polarization length to the particular the spin-lattice relaxation time of a selected phase of the multi-phase fluid; b) selectively using the prepolarization module to polarize a component in a volume of the fluid; c) applying a selective excitation to said fluid volume; d) using a signal resulting from said excitation to obtain a velocity measurement for said component; and e) repeating steps b)-d) until velocity measurements for a desired number of components have been obtained.