# US 10,768,250 B2 · Techniques for operating magnetic resonance imagers to crush returns from unwanted coherence pathways

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- Number: US 10,768,250 B2
- Document ID: US10768250B2
- Status: Granted
- Kind: B2
- Application number: 16/223,626
- Filed: 2018-12-18
- Published: 2019-07-04
- Granted: 2020-09-08
- Earliest claimed: 2017-12-29
- Assignees: The Trustees of Columbia University in the City of New York
- Applicants: The Trustees of Columbia University in the City of New York
- Inventors: Karl Landheer; Christoph Juchem
- Web page: https://patentgrep.com/patent/US10768250B2

## CPC

- G01R 33/4616: {using specific RF pulses or specific modulation schemes, e.g. stochastic excitation, adiabatic RF pulses, composite pulses, binomial pulses, Shinnar-le-Roux pulses, spectrally selective pulses not being used for spatial selection}
- G01R 33/446: {Multifrequency selective RF pulses, e.g. multinuclear acquisition mode (spatially selective RF pulses G01R33/4833)}
- G01R 33/4608: {RF excitation sequences for enhanced detection, e.g. NOE, polarisation transfer, selection of a coherence transfer pathway}
- G01R 33/543: {Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription (G01R33/546 takes precedence)}
- G01R 33/4833: {using spatially selective excitation of the volume of interest, e.g. selecting non-orthogonal or inclined slices}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

Techniques for crushing unwanted coherence pathways during magnetic resonance spectral (MRS) measurements include receiving first data that indicates a sequence of RF pulses with one or more target coherence pathways of spin states for a subject that has at least N≥1 coupled spin states of interest. A negative, non-integer amplitude is determined for at least one intervening crusher pulse emitted from at least one spatial gradient magnetic coil. The at least one intervening crusher pulse has a duration less than a time between successive pulses of the sequence of RF pulses; and, the intervening crusher pulse de-phases unwanted coherence pathways. A MRS device is operated using the intervening crusher pulse and the sequence of RF pulses.

## Claims

### Claim 1

A method for operating a magnetic resonance device, the method comprising:
receiving first data that indicates a sequence of n radio frequency (RF) pulses with one or more target coherence pathways of spin states for making a magnetic resonance spectroscopy (MRS) measurement using a MRS device of a subject that has at least N≥1 coupled spin states of interest;
determining a negative non-integer amplitude for at least one intervening crusher pulse emitted from at least one spatial gradient magnetic coil, wherein
the at least one intervening crusher pulse has a duration less than a time between successive pulses of the sequence of n RF pulses, and
the intervening crusher pulse de-phases unwanted coherence pathways; and
operating the magnetic resonance device using the at least one intervening pulse and the sequence of n RF pulses.

### Claim 2 (depends on 1)

The method as recited in claim 1, wherein determining the negative non-integer amplitude further comprises determining amplitudes for all crusher pulses using an optimization algorithm.

### Claim 3 (depends on 2)

The method as recited in claim 2, wherein using the optimization algorithm further comprises:
determining a matrix A of coherence pathways for n RF pulses and coherence order N comprising matrix elements Aij, i∈(1, . . . , n) and j∈(1, . . . , (2N+1)n), each j representing a unique coherence pathway, j=K indicates the one or more target coherence pathways, and a value of Aij represents a coherence order of a jth pathway after i RF pulses;
determining values for elements Xmi of a matrix X, wherein each element Xmi describes a crusher area for each of 3 orthogonal axes, m∈(1,2,3), after each of n pulses, wherein the crusher area is a product of a spatial gradient Gmi along axis m of an ith crusher pulse and a duration time τmi of the ith crusher pulse, further comprising
determining for current values of elements of matrix X a vector D with elements Dj, having values that indicate a magnitude of a matrix product of XA for each coherence pathway j,
determining a vector {tilde over (D)} based on D with element DK constrained to zero, and
iterating on values of the elements of matrix X to find a solution matrix {tilde over (X)} that maximizes a measure of size of {tilde over (D)} and falls within values achievable by the MRS device and that minimizes an absolute value of DK; and
producing output data that indicates solution matrix {tilde over (X)}, wherein the negative non-integer amplitude is based on at least one element of solution matrix.

### Claim 4 (depends on 3)

The method as recited in claim 3, wherein operating the magnetic resonance device using the at least one intervening pulse further comprises sending signals that cause operation of the MRS device with crusher pulses having the areas of the elements of {tilde over (X)}.

### Claim 5 (depends on 1)

The method as recited in claim 1, wherein the negative non-integer amplitude is not a negative integer multiple of ½.

### Claim 6

A non-transitory computer-readable medium carrying one or more sequences of instructions, wherein execution of the one or more sequences of instructions by one or more processors causes the one or more processors to perform the steps of:
receive first data that indicates a sequence of n radio frequency (RF) pulses with one or more target coherence pathways of spin states for making a magnetic resonance spectroscopy (MRS) measurement using a MRS device of a subject that has at least N≥1 coupled spin states of interest;
determine a negative non-integer amplitude for at least one intervening crusher pulse emitted from at least one spatial gradient magnetic coil, wherein
the at least one intervening crusher pulse has a duration less than a time between successive pulses of the sequence of n RF pulses, and
the intervening crusher pulse de-phases unwanted coherence pathways; and
operate the magnetic resonance device using the at least one intervening crusher pulse and the sequence of n RF pulses.

### Claim 7 (depends on 6)

The non-transitory computer-readable medium as recited in claim 6, wherein to determine the negative non-integer amplitude further comprises to determine amplitudes for all crusher pulses using an optimization algorithm.

### Claim 8 (depends on 7)

The non-transitory computer-readable medium as recited in claim 7, wherein to determine amplitudes for all crusher pulses using the optimization algorithm further comprises:
determine a matrix A of coherence pathways for n RF pulses and coherence order N comprising matrix elements Aij, i∈(1, . . . , n) and j∈(1, . . . , (2N+1)n), each j representing a unique coherence pathway, j=K indicates the one or more target coherence pathways, and a value of Aij represents a coherence order of a jth pathway after i RF pulses;
determine values for elements Xmi of a matrix X, wherein each element Xmi describes a crusher area for each of 3 orthogonal axes, m∈(1,2,3), after each of n pulses, wherein the crusher area is a product of a spatial gradient Gmi along axis m of an ith crusher pulse and a duration time τmi of the ith crusher pulse, further comprising
determine for current values of elements of matrix X a vector D with elements Dj, having values that indicate a magnitude of a matrix product of XA for each coherence pathway j;
determine a vector {tilde over (D)} based on D with element DK constrained to zero, and
iterate on values of the elements of matrix X to find a solution matrix {tilde over (X)} that maximizes a measure of size of {tilde over (D)} and falls within values achievable by the MRS device and that minimizes an absolute value of DK; and
producing output data that indicates solution matrix {tilde over (X)} wherein the negative non-integer amplitude is based on at least one element of solution matrix.

### Claim 9 (depends on 8)

The non-transitory computer-readable medium as recited in claim 8, wherein to operate the magnetic resonance device using the at least one intervening pulse further comprises to send signals that cause operation of the MRS device with crusher pulses having the areas of the elements of {tilde over (X)}.

### Claim 10 (depends on 6)

The non-transitory computer-readable medium as recited in claim 6, wherein the negative non-integer amplitude is not a negative integer multiple of ½.

### Claim 11

A system comprising:
a magnetic resonance spectroscopy (MRS) device,
at least one processor; and
at least one memory including one or more sequences of instructions,
the at least one memory and the one or more sequences of instructions configured to, with the at least one processor, cause the system to perform at least the following,
receive first data that indicates a sequence of n radio frequency (RF) pulses with one or more target coherence pathways of spin states for making a magnetic resonance spectroscopy (MRS) measurement using a MRS device of a subject that has at least N≥1 coupled spin states of interest;
determine a negative non-integer amplitude for at least one intervening crusher pulse emitted from at least one spatial gradient magnetic coil, wherein
the at least one intervening crusher pulse has a duration less than a time between successive pulses of the sequence of n RF pulses, and
the intervening crusher pulse de-phases unwanted coherence pathways; and
operate the magnetic resonance device using the at least one intervening crusher pulse and the sequence of n RF pulses.

### Claim 12 (depends on 11)

The system as recited in claim 11, wherein to determine the negative non-integer amplitude further comprises to determine amplitudes for all crusher pulses using an optimization algorithm.

### Claim 13 (depends on 12)

The system as recited in claim 12, wherein to determine the negative non-integer amplitude further comprises:
determine a matrix A of coherence pathways for n RF pulses and coherence order N comprising matrix elements Au, i∈(1, . . . , n) and j∈(1, . . . , (2N+1)n), each j representing a unique coherence pathway, j=K indicates the one or more target coherence pathways, and a value of Aij represents a coherence order of a jth pathway after i RF pulses;
determine values for elements Xmi of a matrix X, wherein each element Xmi describes a crusher area for each of 3 orthogonal axes, m (1,2,3), after each of n pulses, wherein the crusher area is a product of a spatial gradient Gmi along axis m of an ith crusher pulse and a duration time τmi of the ith crusher pulse, further comprising;
determine for current values of elements of matrix X a vector D with elements Dj, having values that indicate a magnitude of a matrix product of XA for each coherence pathway j;
determine a vector {tilde over (D)} based on D with element DK constrained to zero, and
iterate on values of the elements of matrix X to find a solution matrix {tilde over (X)} that maximizes a measure of size of {tilde over (D)} and falls within values achievable by the MRS device and that minimizes an absolute value of DK; and
produce output data that indicates solution matrix {tilde over (X)}, wherein the negative non-integer amplitude is based on at least one element of solution matrix.

### Claim 14 (depends on 13)

The system as recited in claim 13, wherein to operate the magnetic resonance device using the at least one intervening pulse further comprises to send signals that cause operation of the MRS device with crusher pulses having the areas of the elements of {tilde over (X)}.

### Claim 15 (depends on 11)

The system as recited in claim 11, wherein the negative non-integer amplitude is not a negative integer multiple of ½.