Methods for measurement of longitudinal spin relaxation times in moving liquids

Claim 1

A method of measuring spin lattice relaxation time, T 1 , within a subject comprising the steps of: a) placing said subject in a magnetic field to generate longitudinal spin magnetization of nuclear spins within the subject; b) applying a spatially non-selective radio-frequency (RF) pulse to invert the longitudinal magnetization of the nuclear spins; c) applying a spatially selective RF pulse having a predetermined frequency range to convert longitudinal magnetization into transverse spin magnetization of a selected ensemble of nuclear spins of a spatial region defined by the frequency range; d) detecting at a time n, magnetic resonance signals generated by the transverse spin magnetization of the selected ensemble of nuclear spins; e) repeating steps `c` through `d` for a plurality of `N` repetitions to detect `N` MR response signals, each detected at a different time `n` after application of the spatially non-selective RF pulse to encode in a time dimension; f) selecting a subset of the ensemble of nuclear spins; and g) determining the spin lattice relaxation time, T 1 , for the selected subset of the ensemble of nuclear spins, the spin relaxation time being an exponential recovery rate of the MR response signal of the selected subset as a function of time.

Claim 2

A method of measuring spin lattice relaxation time, T 1 , within a subject comprising the steps of: a) placing said subject in a magnetic field to generate longitudinal spin magnetization of nuclear spins within the subject; b) applying a spatially non-selective radio-frequency (RF) pulse to invert the longitudinal magnetization of the nuclear spins; c) applying a spatially selective RF pulse having a predetermined frequency range to convert longitudinal magnetization into transverse spin magnetization of a selected ensemble of nuclear spins of a spatial region defined by the frequency range; d) detecting at a time n, magnetic resonance signals generated by the transverse spin magnetization of the selected ensemble of nuclear spins; e) repeating steps `c` through `d` for a plurality of `N` repetitions to detect `N` MR response signals, each detected at a different time `n` after application of the spatially non-selective RF pulse to encode in a time dimension; f) selecting a subset of the ensemble of nuclear spins; and g) determining the spin lattice relaxation time, T 1 , for the selected subset of the ensemble of nuclear spins, the spin relaxation time being an exponential recovery rate of the MR response signal of the selected subset as a function of time.

Claim 3

A method of measuring spin lattice relaxation time, T 1 , of nuclear spins within a subject comprising the steps of: a) placing said subject in a magnetic field to generate longitudinal spin magnetization of said nuclear spins; b) applying a spatially non-selective radio-frequency (RF) pulse to invert the longitudinal magnetization of the nuclear spins; c) applying a spatially selective RF pulse having a predetermined frequency range to convert longitudinal magnetization into transverse spin magnetization in a selected ensemble of nuclear spins of a spatial region defined by the frequency range; d) applying a phase-encoding magnetic field gradient pulse having an amplitude `a` to induce a phase evolution in the nuclear spins which is dependent upon the position of the nuclear spins in a phase-encoding direction; e) applying a readout dephasing magnetic field gradient pulse to induce a phase evolution in the nuclear spins which is dependent upon the position of the nuclear spins in a readout direction, substantially orthogonal to the phase-encoding direction; f) applying a readout magnetic field gradient pulse during detection of the magnetic resonance (MR) response signals to induce a phase evolution in the nuclear spins which is dependent upon the position of the nuclear spins in the readout direction; g) detecting at a time n and for a phase encoding amplitude `a`, a MR response signal having inherent phase shifts induced by the phase evolutions of the selected ensemble of nuclear spins; h) repeating steps `c` through `e` for a plurality of `N` repetitions to detect `N` MR response signals, each detected at a different time `n` after application of the spatially non-selective RF pulse for a phase encoding amplitude `a` to encode in a time dimension; i) repeating steps `b`-`h` for a plurality of `P` different phase encoding gradient amplitudes `a` to encode the detected MR response signal in a phase-encoding direction; j) selecting a subset of the ensemble of nuclear spins being a spatial subregion having dimensions in the phase encoding direction and the readout direction; and k) determining the spin lattice relaxation time, T 1 , for the selected subset of the ensemble of nuclear spins by calculating changes over time in portions of the MR response signal pertaining to the selected subset.

Claim 4

A method of measuring spin lattice relaxation time, T 1 , of nuclear spins within a subject comprising the steps of: a) placing said subject in a magnetic field to generate longitudinal spin magnetization of said nuclear spins; b) applying a spatially non-selective radio-frequency (RF) pulse to invert the longitudinal magnetization of the nuclear spins; c) applying a spatially selective RF pulse having a predetermined frequency range to convert longitudinal magnetization into transverse spin magnetization in a selected ensemble of nuclear spins of a spatial region defined by the frequency range; d) applying a phase-encoding magnetic field gradient pulse having an amplitude `a` to induce a phase evolution in the nuclear spins which is dependent upon the position of the nuclear spins in a phase-encoding direction; e) applying a readout dephasing magnetic field gradient pulse to induce a phase evolution in the nuclear spins which is dependent upon the position of the nuclear spins in a readout direction, substantially orthogonal to the phase-encoding direction; f) applying a readout magnetic field gradient pulse during detection of the magnetic resonance (MR) response signals to induce a phase evolution in the nuclear spins which is dependent upon the position of the nuclear spins in the readout direction; g) detecting at a time n and for a phase encoding amplitude `a`, a MR response signal having inherent phase shifts induced by the phase evolutions of the selected ensemble of nuclear spins; h) repeating steps `c` through `e` for a plurality of `N` repetitions to detect `N` MR response signals, each detected at a different time `n` after application of the spatially non-selective RF pulse for a phase encoding amplitude `a` to encode in a time dimension; i) repeating steps `b`-`h` for a plurality of `P` different phase encoding gradient amplitudes `a` to encode the detected MR response signal in a phase-encoding direction; j) selecting a subset of the ensemble of nuclear spins being a spatial subregion having dimensions in the phase encoding direction and the readout direction; and k) determining the spin lattice relaxation time, T 1 , for the selected subset of the ensemble of nuclear spins by calculating changes over time in portions of the MR response signal pertaining to the selected subset.