MR imaging of synchronous spin motion and strain waves

Claim 1

A method for producing an image indicative of a mechanical characteristic of tissues, the steps comprising: a) applying a polarizing magnetic field to the tissues; b) irradiating the tissues with an RF excitation field that produces transverse magnetization in spins in said tissues; c) applying a magnetic field gradient to the spins which alternates in polarity; d) applying a stress to the tissues which varies in magnitude in synchronism with the alternation in the magnetic field gradient polarity; e) acquiring an NMR signal produced by the transversely magnetized spins; f) repeating steps a) through e) to acquire a set of said NMR signals from which a first image may be reconstructed; g) repeating steps a) through f) to acquire NMR signals from which a second image may be constructed; h) producing a third image indicative of the difference in phase between the NMR signals acquired for said first and second images; and i) producing from said third image a fourth image which indicates a mechanical property of the tissues.

Claim 2

A method for producing an image indicative of a mechanical characteristic of tissues, the steps comprising: a) applying a polarizing magnetic field to the tissues; b) irradiating the tissues with an RF excitation field that produces transverse magnetization in spins in said tissues; c) applying a magnetic field gradient to the spins which alternates in polarity; d) applying a stress to the tissues which varies in magnitude in synchronism with the alternation in the magnetic field gradient polarity; e) acquiring an NMR signal produced by the transversely magnetized spins; f) repeating steps a) through e) to acquire a set of said NMR signals from which a first image may be reconstructed; g) repeating steps a) through f) to acquire NMR signals from which a second image may be constructed; h) producing a third image indicative of the difference in phase between the NMR signals acquired for said first and second images; and i) producing from said third image a fourth image which indicates a mechanical property of the tissues.

Claim 19

A method for producing an image with an NMR imaging system which indicates a mechanical characteristic of a subject within the field of view of the NMR imaging system, the steps comprising: a) imparting mechanical wave motion to spins located in the subject; b) conducting a scan of the subject with the NMR imaging system using a pulse sequence in which an alternating magnetic field gradient is employed to impart a phase shift in acquired NMR data due to the wave motion of the spins; and c) reconstructing a phase image from the NMR data acquired during the scan and employing the phase information therein to indicate the mechanical characteristic of the subject at each pixel location in the image.

Claim 20

A method for producing an image with an NMR imaging system which indicates a mechanical characteristic of a subject within the field of view of the NMR imaging system, the steps comprising: a) imparting mechanical wave motion to spins located in the subject; b) conducting a scan of the subject with the NMR imaging system using a pulse sequence in which an alternating magnetic field gradient is employed to impart a phase shift in acquired NMR data due to the wave motion of the spins; and c) reconstructing a phase image from the NMR data acquired during the scan and employing the phase information therein to indicate the mechanical characteristic of the subject at each pixel location in the image.

Claim 39

A method for producing an image with an NMR imaging system which indicates a mechanical characteristic of a subject within the field of view of the NMR imaging system, the steps comprising: a) conducting a scan of the subject with the NMR imaging system to acquire a first and a second NMR data set, the first NMR data set being acquired by: i) imparting mechanical wave motion to spins located in the subject by energizing a transducer which applies an alternating stress to the subject; ii) performing an imaging pulse sequence with the NMR imaging system in which an alternating magnetic field gradient is employed to impart a phase shift in the acquired first NMR data set due to the wave motion of the spins; the second NMR data set being acquired by: iii) changing the energization of said transducer from that used during the acquisition of the first NMR data set; iv) performing substantially the same imaging pulse sequence used to acquire the first NMR data set; b) reconstructing a phase image by combining the first and second NMR data sets to indicate the difference in phase of the first and second NMR data sets at each pixel of the phase image; and c) displaying an image of a mechanical characteristic of the subject using the phase image.

Claim 40

A method for producing an image with an NMR imaging system which indicates a mechanical characteristic of a subject within the field of view of the NMR imaging system, the steps comprising: a) conducting a scan of the subject with the NMR imaging system to acquire a first and a second NMR data set, the first NMR data set being acquired by: i) imparting mechanical wave motion to spins located in the subject by energizing a transducer which applies an alternating stress to the subject; ii) performing an imaging pulse sequence with the NMR imaging system in which an alternating magnetic field gradient is employed to impart a phase shift in the acquired first NMR data set due to the wave motion of the spins; the second NMR data set being acquired by: iii) changing the energization of said transducer from that used during the acquisition of the first NMR data set; iv) performing substantially the same imaging pulse sequence used to acquire the first NMR data set; b) reconstructing a phase image by combining the first and second NMR data sets to indicate the difference in phase of the first and second NMR data sets at each pixel of the phase image; and c) displaying an image of a mechanical characteristic of the subject using the phase image.