Nuclear magnetic resonance (NMR) imaging with multiple surface coils

A method for simultaneously receiving a different NMR response signal from each of a plurality N of closely-spaced RF surface coils, comprising the steps of:

• (a) providing an at least one-dimensional array of the plurality N of surface coils, with the array defining an imaging volume, and with each surface coil having substantially no interaction with at least all adjacent surface coils;
• (b) receiving at each different one of the plurality N of surface coils a different one of a like plurality N of NMR response signals each evoked from an associated portion of a sample enclosed in the imaging volume;
• (c) constructing each different one of a like plurality N of NMR images of a sample portion from the NMR response signals received by an associated surface coils;
• and
• (d) the combining the plurality N of different images with weighting, on a point-by-point basis, each pixel of each image by a factor determined by at least by magnitude of correlated and uncorrelated noise between each adjacent pair of surface coils to produce a single final NMR image of all sample portions from which a NMR response signal was received by any one of the surface coils.

A method for simultaneously receiving a different NMR response signal from each of a plurality N of closely-spaced, substantially-circular-shaped RF surface coils, comprising the steps of:

• (a) providing an at least one-dimensional array of the plurality N of surface coils, with the array defining an imaging volume, and positioning the centers of any pair of adjacent surface coils at a separation distance substantially equal to one and one-half times the radius of one of the surface coils of the pair to cause each surface coil to have substantially no interaction with at least all adjacent surface coils;
• (b) receiving at each different one of the plurality N of surface coils a different one of a like plurality N of NMR response signals each evoked from an associated portion of a sample enclosed in the imaging volume;
• (c) constructing each different one of a like plurality N of NMR images of a sample portion from the NMR response signals received by an associated surface coils;
• and
• (d) then combining the plurality N of different images, on a point-by-point basis, to produce a single final NMR image of all sample portions from which a NMR response signal was received by any one of the surface coils.

A method for simultaneously receiving a different NMR response signal from each of a plurality N of closely-spaced, substantially-square-shaped RF surface coils, comprising the steps of:

• (a) providing an at least one-dimensional array of the plurality of surface coils, with the array defining an imaging volume, and positioning the centers of any pair of adjacent surface coils at a separation distance of about nine-tenths of the side length of one of the surface coils of the pair to cause each surface coil to have substantially no interaction with at least all adjacent surface coils;
• (b) receiving at each different one of the plurality N of surface coils a different one of a like plurality N of NMR response signals each evoked from an associated portion of a sample enclosed in the imaging volume;
• (c) constructing each different one of a like plurality N of NMR images of a sample portion from the NMR response signals received by an associated surface coils;
• and
• (d) the combining the plurality N of different images, on a point-by-point basis, to produce a single final NMR image of all sample portions from which a NMR response signal was received by any one of the surface coils.

A method for simultaneously receiving a different NMR response signal from each of a plurality N of closely-spaced RF surface coils, comprising the steps of:

• (a1) providing an at least one-dimensional array of the plurality N of surface coils with the array defining an imaging volume, and with each surface coil having substantially no interaction with at least all adjacent surface coils;
• (a2) and also providing in the array at least one pair of surface coils not adjacent to each other;
• and
• (a3) minimizing the interaction between each non-adjacent surface coil of that pair by:
• providing a preamplifier for each surface coil;
• connecting the output of each different one of the pair of non-adjacent surface coils to the input of a different preamplifier;
• and causing an effective input impedance of the preamplifier, at the associated surface coil, to resonate at the NMR response frequency with the output impedance of that surface coil and reduce the apparent surface coil Q towards a value of zero;
• (b) receiving at each different one of the plurality N of surface coils a different one of a like plurality N of NMR response signals each evoked from an associated portion of a sample enclosed in the imaging volume;
• (c) constructing each different one of a like plurality N of NMR images of a sample portion from the NMR response signals received by an associated surface coils;
• and
• (d) then combining the plurality N of different images, on a point-by-point bases, to produce a single final NMR image of all sample portions from whcih a NMR response signal was received by any one of the surface coils.

Apparatus for simultaneously receiving NMR response signals for nuclei within a predetermined portion of a sample, comprising:

• a plurality of surface coil antennae, positioned in an array extending in at least one dimension along a surface enclosing the sample, each surface coil positioned to have substantially no interaction with at least all adjacent surface coils, and with at least one pair of surface coils not adjacent to each other;
• and
• means for minimizing the interaction between each non-adjacent surface coil of each pair thereof, and including:
• a plurality of preamplifiers, each having an input impedance on the order of 5 ohms at the NMR response frequency, with a different preamplifier being connected to the output of each different one of the non-adjacent surface coils and providing a minimized-interaction signal, for that associated surface, from the preamplifier output;
• and means, operating with each different preamplifier, for providing an effective impedance connected in parallel with the associated surface coil to resonate at the NMR response frequency and reduce the apparatus surface coil Q towards the value of zero to reduce the current circulating in the associated surface coil during reception, without substantially changing the signal-to-noise ratio.