Multicoil NMR data acquisition and processing methods
AssigneeVista Clara Inc.
InventorDavid O. Walsh
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Abstract
A multicoil NMR data acquisition apparatus and processing method for performing three-dimensional magnetic resonance imaging in a static magnetic field without the application of controlled static magnetic field gradients. A preferred application relates specifically to the detection and localization of groundwater using the Earth's magnetic field. Multicoil arrays are used in both transmit and receive modes. and coherent data processing algorithms applied to the data to generate three-dimensional NMR spin density estimates. Disclosed are methods for acquiring NMR data using an array of at least two transmit and receive coils, and for processing such multicoil data to estimate the three-dimensional NMR spin density distributions.
Claims35
A method of obtaining a localized nuclear magnetic resonance Nuclear Magnetic Resonance (NMR) signal from a sample a subsurface three dimensional (3D) volume in a static magnetic field using an array of two or more magnetic field transmitting coils, and an array of two or more magnetic field receiving coils, the method comprising:
- a) generating a single an alternating current excitation pulse on one or more transmitting coils, each of said transmitting coils of the array, providing a spatially distinct an inhomogeneous magnetic field in the three dimensional (3D) volume;
- b) acquiring NMR signals on two or more magnetic field receiving coils of the array of magnetic field coils;
- c) applying a plurality of excitation pulses to each transmitting coil or combination of transmitting coils, wherein each excitation pulse has a unique pulse moment defined as the product of the pulse amplitude and pulse length, and wherein the nth pulse moment PM(n) is not equal to (2n−1)*PM(1);
- and repeating steps a and b using a plurality of excitation pulses, wherein the plurality of excitation pulses produce magnetic fields in the 3D volume, wherein at least one excitation pulse is produced by a transmitting coil of the array that is spatially distinct from another transmitting coil geometry or location, and wherein at least one excitation pulse comprises a pulse moment that is unique from a pulse moment of another excitation pulse, and wherein an nth pulse moment PM(n) is not equal to (2n−1)*PM(1);
- and
- d) constructing a localized nuclear magnetic resonance NMR signal as a linear combination of NMR signals obtained using two or more transmitting coils or combinations of transmitting coils, two or more receiving coils, and two or more pulse moments for each transmitting coil excitation pulses corresponding to a plurality of different transmitting coil geometries or locations and a plurality of different pulse moments.
A multi-channel Nuclear Magnetic Resonance (NMR) data acquisition apparatus that uses an array of magnetic field coils to obtain a localized NMR signal from a three dimensional (3D) volume in a static magnetic field, comprising:
- a computer;
- one or more signal generators and power amplifiers configured to produce alternating current excitation pulses on one or more coils;
- an array of coils, wherein:
- one or more of the coils of the array are configured to produce magnetic fields in a three-dimensional (3D) volume in response to excitation pulses produced by the one or more signal generators and power amplifiers, wherein at least one excitation pulse is produced by a coil that is spatially distinct from another coil geometry or location, and wherein at least one excitation pulse comprises a pulse moment that is unique from a pulse moment of another excitation pulse, and wherein an nth pulse moment PM(n) is not equal to (2n−1)*PM(1);
- and
- two or more of the coils of the array of coils are configured to receive NMR signals produced in the 3D volume in response to the produced magnetic fields;
- a multi-channel Analog to Digital (AD) data acquisition device configured to receive NMR signals via the coils configured to receive NMR signals, convert received NMR signals to digital signals, and output the digital signals to the computer;
- wherein the computer is configured to record the digital signals produced by the AD data acquisition device;
- and
- wherein the computer is configured to construct a localized NMR signal as a linear combination of NMR signals obtained using excitation pulses corresponding to a plurality of different transmitting coil geometries or locations and a plurality of different pulse moments.
Dependencies are inferred from the claim text.