# US 5,347,217 A · Magnetic resonance spectroscopy and imaging

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- Number: US 5,347,217 A
- Document ID: US5347217A
- Status: Granted
- Kind: A
- Application number: 07/966,158
- Filed: 1993-03-05
- Granted: 1994-09-13
- Earliest claimed: 1990-08-02
- Assignees: British Technology Group Limited
- Inventors: Martin O. Leach; Jonathan C. Sharp
- Web page: https://patentgrep.com/patent/US5347217A

## CPC

- G01R 33/54: Signal processing systems, e.g. using pulse sequences {; Generation or control of pulse sequences; Operator console}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

In magnetic resonance spectroscopy or imaging, e.g. n.m.r. or e.s.r., a method of localizing the region of a sample from which a resonance signal is obtained by modulating the component M.sub.z of magnetization in the B.sub.o direction according to position in the sample. This is achieved by flipping the spins away from the B.sub.o direction, applying a gradient magnetic field so that they lose or gain phase according to their position, refocussing the effects of any resonance offsets including chemical shifts and subsequently returning them to the B.sub.o direction whereupon M.sub.z depends on the phase lost or gained and thus the position. This may be repeated, possibly with different gradient fields or different phase pulses, to further localize the region before a resonance signal is finally detected. The contribution to the resonance signal varies with M.sub.z and so is localized to regions of greater M.sub.z.

## Claims

### Claim 1

A method of preparing the magnetization in a sample for magnetic resonance comprising:
applying to the sample a first e.m. preparation pulse to flip the spins in the sample away from the B.sub.o direction,
then applying a phase-encoding gradient magnetic field pulse of predetermined magnitude and duration to the sample to give a positional variation of phase in one direction in the sample,
and subsequently applying second e.m. preparation pulse to the sample to return the spins to the B.sub.o direction, the phase variation encoded during the application of the phase-encoding gradient magnetic field pulse resulting in a predetermined spatial variation in magnetization along the B.sub.o axis to enable a resonance signal to be then obtained from a predetermined localized region in a single acquistition.

### Claim 2 (depends on 1)

A method according to claim 1, wherein the e.m. preparation pulses are non-selective.

### Claim 3 (depends on 1)

A method according to claim 1, further comprising the steps of applying one or more further episodes of e.m. preparation pulses and phase-encoding magnetic field gradients without intermediate read-out of the resonance signal whereby the localized region is more closely defined, said episodes being followed by a single acquistion to obtain a resonance signal.

### Claim 4 (depends on 3)

A method according to claim 3, wherein at least one of the direction and magnitude of the phase-encoding gradient differs between repeat episodes to further localize the region of the sample from which a resonance signal will be obtained.

### Claim 5 (depends on 1)

A method according to claim 1, further comprising the step of applying a re-focussing e.m. pulse to the sample.

### Claim 6 (depends on 5)

A method according to claim 5, wherein the re-focussing pulse is spaced equally between the e.m. preparation pulses which respectively flip the spins away from and return the spins to the B.sub.o field direction.

### Claim 7 (depends on 1)

A method according to claim 1, wherein a gradient magnetic field is applied after return of the spins to the B.sub.o direction to dephase any remaining transverse components of spin.

### Claim 8 (depends on 1)

A method according to claim 1, wherein the phase of the e.m. preparation pulses is selected according to the localization required.

### Claim 9 (depends on 1)

A method according to claim 1, wherein the amplitude of the preparation pulses is selected so that the phase encoding gradient modulates the magnetization component M.sub.z in the range .vertline.M.sub.o .vertline. to zero.