Magnetic resonance signal acquisition methods

Claim 1

A method of obtaining a nuclear magnetic resonance signal from a region of an object comprising subjecting the object to a static magnetic field and carrying out the following steps: 1) applying an rf selective 90° pulse in the presence of a first gradient magnetic field and applying at least one non-selective rf pulse in the absence of a gradient magnetic field so as to dephase incoherently all magnetisation in the object except in a slice orthogonal to the gradient direction of the said first gradient magnetic field; 2) in the presence of a second gradient magnetic field having a gradient extending in a direction generally orthogonal to said one direction and the said static magnetic field, applying an rf selective 90° pulse to tip into a plane perpendicular to the direction of the said static magnetic field a strip defined by the intersection of the aforesaid slice and slice orthogonal to the gradient direction of said second gradient magnetic field; and 3) in the presence of a third gradient magnetic field having a gradient direction extending generally orthogonally to the gradient directions of both the first and second gradient magnetic fields, applying an rf signal to refocus the spins of nuclei in a region defined by the intersection of said strip and a slice orthogonal to the gradient direction of said third gradient magnetic field so that the resulting free induction echo signal arises from the said region alone.

Claim 2

A method of obtaining a nuclear magnetic resonance signal from a region of an object comprising subjecting the object to a static magnetic field and carrying out the following steps: 1) applying an rf selective 90° pulse in the presence of a first gradient magnetic field and applying at least one non-selective rf pulse in the absence of a gradient magnetic field so as to dephase incoherently all magnetisation in the object except in a slice orthogonal to the gradient direction of the said first gradient magnetic field; 2) in the presence of a second gradient magnetic field having a gradient extending in a direction generally orthogonal to said one direction and the said static magnetic field, applying an rf selective 90° pulse to tip into a plane perpendicular to the direction of the said static magnetic field a strip defined by the intersection of the aforesaid slice and slice orthogonal to the gradient direction of said second gradient magnetic field; and 3) in the presence of a third gradient magnetic field having a gradient direction extending generally orthogonally to the gradient directions of both the first and second gradient magnetic fields, applying an rf signal to refocus the spins of nuclei in a region defined by the intersection of said strip and a slice orthogonal to the gradient direction of said third gradient magnetic field so that the resulting free induction echo signal arises from the said region alone.

Claim 7

The method as claimed in any one of the preceding claims in which a phase-encoding magnetic field gradient orthogonal to said one direction is interposed between steps 2) and step 3) and a free-induction signal is acquired in the presence of a magnetic field gradient in said one direction so that the signal contains image information of the said region.