Spin echo MR imaging with spiral acquisition

Patent metadata

Field	Value
Publication number	US-12467996-B2
Application number	US-202118035301-A
Country	US
Kind code	B2
Filing date	Nov 4, 2021
Priority date	Nov 9, 2020
Publication date	Nov 11, 2025
Grant date	Nov 11, 2025

Abstract

The invention relates to a method of MR imaging of an object ( 10 ) positioned in an examination volume of an MR device ( 1 ). It is an object of the invention to enable spiral MR imaging with a reduced level of ringing artefacts close to strong local IC main magnetic field inhomogeneity. The method of the invention comprises the following steps:—generating a spin echo by subjecting the object ( 10 ) to an imaging sequence comprising an RF excitation pulse ( 31 ) followed by an RF refocusing pulse ( 32 ), wherein a modulated readout magnetic field gradient ( 34 ) is applied subsequent to the RF refocusing pulse ( 32 ),—acquiring MR signal data by recording the spin echo along a spiral trajectory in k-space, wherein the waveform of the readout magnetic field gradient ( 34 ) defining the spiral trajectory starts before the spin echo center ( 33 ), and—reconstructing an MR image from the acquired MR signal data. Moreover, the invention relates to an MR device ( 1 ) and to a computer program for an MR device ( 1 ).

First claim

The invention claimed is:

1 . A method of magnetic resonance (MR) imaging of an object positioned in an examination volume of an MR device, the method comprising:
generating a spin echo by subjecting the object to an imaging sequence comprising an RF excitation pulse followed by an RF refocusing pulse, wherein a modulated readout magnetic field gradient is applied subsequent to the RF refocusing pulse, acquiring MR signal data by recording the spin echo along a spiral trajectory in k-space, wherein a waveform of the modulated readout magnetic field gradient defining the spiral trajectory starts before a spin echo center, wherein a diffusion-sensitizing magnetic field gradient is applied before and after the RF refocusing pulse, so as to diffusion-weight the acquired MR signals and a duration of the diffusion-sensitizing magnetic field gradient applied before the RF refocusing pulse is longer than the duration of the diffusion-sensitizing magnetic field gradient applied after the RF refocusing pulse,
and
arranging to reconstruct a diffusion-weighted MR image from the acquired MR signal data.

2 . A magnetic resonance (MR) device comprising at least one main magnet coil for generating a uniform; static magnetic field within an examination volume; a number of gradient coils for generating switched magnetic field gradients in different spatial directions within the examination volume; at least one RF coil for generating RF pulses within the examination volume and/or for receiving MR signals from an object positioned in the examination volume; a control unit for controlling a temporal succession of RF pulses and switched magnetic field gradients; a reconstruction unit for reconstructing an MR image from the received MR signals; a processor; and a non-transitory computer readable medium that stored computer program, which when executed by the processor, causes the processor to:
generate a spin echo by subjecting the object to an imaging sequence comprising an RF excitation pulse followed by an RF refocusing pulse, wherein a modulated readout magnetic field gradient is applied subsequent to the RF refocusing pulse; acquire MR signal data by recording the spin echo along a spiral trajectory in k-space, wherein a waveform of the modulated readout magnetic field gradient defining the spiral trajectory starts before a spin echo center wherein a diffusion-sensitizing magnetic field gradient is applied before and after the RF refocusing pulse, so as to diffusion-weight the acquired MR signals and duration of the diffusion-sensitizing magnetic field gradient applied before the RF refocusing pulse is longer than the duration of the diffusion-sensitizing magnetic field gradient applied after the RF refocusing pulse; and arrange for reconstructing a diffusion-weighted MR image from the acquired MR signal data.

3 . A computer program including executable instructions stored on a non-transitory computer readable medium, which when executed by a processor of a magnetic resonance (MR) device, causes the processor to:
generate a spin echo by applying an imaging sequence comprising an RF excitation pulse followed by an RF refocusing pulse, wherein a modulated readout magnetic field gradient is applied subsequent to the RF refocusing pulse; acquire MR signal data by recording the spin echo along a spiral trajectory in k-space, wherein a waveform of the modulated readout magnetic field gradient defining the spiral trajectory starts before a spin echo center, wherein a diffusion-sensitizing magnetic field gradient is applied before and after the RF refocusing pulse, so as to diffusion-weight the acquired MR signals and a duration of the diffusion-sensitizing magnetic field gradient applied before the RF refocusing pulse is longer than the duration of the diffusion-sensitizing magnetic field gradient applied after the RF refocusing pulse; and arrange for reconstructing a diffusion-weighted MR image from the acquired MR signal data.

4 . The method of claim 1 , wherein the start of the waveform of the modulated readout magnetic field gradient is shifted by one quarter to one half of a total acquisition time of the spiral trajectory with respect to the spin echo center.

5 . The method of claim 1 , wherein the waveform of the modulated readout magnetic field gradient defining the spiral trajectory starts 2 ms to 5 ms before the spin echo center.

6 . The method of claim 1 , wherein the reconstruction of the MR image involves de-blurring based on a B 0 map.

7 . The method of claim 1 , wherein the start of the waveform of the modulated readout magnetic field gradient is shifted by approximately one third of a total acquisition time of the spiral trajectory with respect to the spin echo center.

8 . The MR device of claim 2 , wherein the start of the waveform of modulated the modulated readout magnetic field gradient is shifted by one quarter to one half of a total acquisition time of the spiral trajectory with respect to the spin echo center.

9 . The MR device of claim 2 , wherein the start of the waveform of the modulated readout magnetic field gradient is shifted by one third of a total acquisition time of the spiral trajectory with respect to the spin echo center.

10 . The MR device of claim 2 , wherein the waveform of the modulated readout magnetic field gradient defining the spiral trajectory starts 2 ms to 15 ms before the spin echo center.

11 . The MR device of claim 2 , wherein the reconstructing of the MR image involves de-blurring based on a B 0 map.

12 . The computer program of claim 3 , wherein the start of the waveform of the modulated readout magnetic field gradient is shifted by one quarter to one half of a total acquisition time of the spiral trajectory with respect to the spin echo center.

13 . The computer program of claim 3 , wherein the start of the waveform of the modulated readout magnetic field gradient is shifted by one third of a total acquisition time of the spiral trajectory with respect to the spin echo center.

14 . The computer program of claim 3 , wherein the waveform of the modulated readout magnetic field gradient defining the spiral trajectory starts 2 ms to 15 ms before the spin echo center.

15 . The computer program of claim 3 , wherein the reconstructing of the MR image involves de-blurring based on a B 0 map.

Assignees

• Koninklijke Philips Nv

Inventors

• Fuderer Miha

Classifications

• G01R33/5608

  Data processing and visualization specially adapted for MR, e.g. for feature analysis and pattern recognition on the basis of measured MR data, segmentation of measured MR data, edge contour detection on the basis of measured MR data, for enhancing measured MR data in terms of signal-to-noise ratio by means of noise filtering or apodization, for enhancing measured MR data in terms of resolution by means for deblurring, windowing, zero filling, or generation of gray-scaled images, colour-coded images or images displaying vectors instead of pixels (image data processing or generation, in general G06T) · CPC title

• G01R33/4824 Primary

  using a non-Cartesian trajectory · CPC title

• G01R33/243

  Spatial mapping of the polarizing magnetic field · CPC title

• G01R33/56341 Primary

  Diffusion imaging · CPC title

• G01R33/56563

  caused by a distortion of the main magnetic field B0, e.g. temporal variation of the magnitude or spatial inhomogeneity of B0 (G01R33/56509, G01R33/56518, G01R33/56536 take precedence) · CPC title