Patent ID: 6794866
Filing Date: 2004-09-21
Classification: G01R

Abstract:
A method for pulsed field gradient NMR (=nuclear magnetic resonance) using stimulated echoes for determining a translational isotropic or anisotropic diffusion coefficient of a molecule or supra-molecular assembly and for determining a flow rate and flow direction of fluids containing such molecules, the method comprising the steps of:a) selecting a molecule or supra-molecular assembly containing protons (H) and at least one isotope (X) having non-zero nuclear spin, the isotope having a longitudinal relaxation time T1 (X) which is substantially longer than a longitudinal relaxation time T1 (H) of protons; and b) irradiating a sequence of radio-frequency pulses onto the selected assembly to transfer magnetization from the protons to the isotope and to transfer said magnetization from the isotope back to the protons, wherein information concerning a localization of the molecule or supra-molecular assembly during a diffusion or flow interval is temporarily stored in a form of longitudinal magnetization of the isotope, c) wherein said sequence of radio frequency pulses converts a transverse magnetization of the isotope perpendicular to an applied magnetic field into a longitudinal magnetization parallel to the applied magnetic field during an interval where translational diffusion or flow is monitored.