Motion-sensitized driven equilibrium blood-suppression sequence for vessel wall imaging

Patent metadata

Field	Value
Publication number	US-9448296-B2
Application number	US-92225709-A
Country	US
Kind code	B2
Filing date	Feb 20, 2009
Priority date	Mar 18, 2008
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

An improved motion-sensitization driven equilibrium (iMSDE) sequence based upon an MLEV-4 sequence is used for black-blood vessel wall imaging. The MSDE pulse pattern that is used us a preparation sequence for other procedures employed to acquire images has been modified to produce the iMSDE sequence by the addition of a second 180 degree refocusing pulse and two motion sensitization gradients. The iMSDE sequence thus includes a group of four radio frequency (RF) pulses, as well as additional magnetic gradient pulses that are not included in the conventional MSDE sequence. Computer simulations indicate that this new pulse sequence is substantially more immune to local B1 inhomogeneity than conventional sequences. In vivo experiments have demonstrated significant signal improvement at high first-order moments (m 1 ) conditions compared to the traditional MSDE sequence.

First claim

The invention in which an exclusive right is claimed is defined by the following:

1. A method, comprising:
(a) using a magnetic resonance imaging (MRI) device, administering a preparation sequence configured to suppress a contribution due to flowing blood in an MRI signal of a site in a subject, the administering of the preparation sequence including:
(i) applying four radio frequency (RF) pulses to the site at predefined time intervals;
(ii) applying a plurality of motion sensitizing magnetic field gradients to the site, for each of a plurality of orthogonal axes, wherein the motion sensitizing magnetic field gradients are applied between the RF pulses; and
(iii) applying a spoiler magnetic field gradient to the site after a last of the four RF pulses; and

(b) after the administering of the preparation sequence and using the MRI device, performing an image acquisition sequence to acquire a magnetic resonance image signal that is usable to image the site, the preparation sequence reducing contributions to the magnetic resonance image signal from flowing blood at the site;
wherein applying the plurality of motion sensitizing magnetic field gradients further comprises constructing the plurality of motion sensitizing magnetic field gradients so that a phase coherence among stationary spins at the site is retained.

2. The method of claim 1 , wherein the step of applying the four RF pulses includes the step of applying, in order:
(a) a first 90 degree RF pulse;
(b) a first 180 degree RF pulse;
(c) a second 180 degree RF pulse; and
(d) a second 90 degree pulse.

3. The method of claim 2 , wherein the step of applying the four RF pulses comprises the step of applying the four RF pulses to the site over a predefined preparation period, TE prep , using predefined time intervals between the first 90 degree RF pulse and the first 180 degree RF pulse, and between the second 180 degree RF pulse and the second 90 degree pulse that are equal to TE prep /4, and using a predefined time interval between the first 180 degree RF pulse and the second 180 degree RF pulse that is equal to TE prep /2.

4. The method of claim 3 , wherein for the plurality of motion sensitizing magnetic field gradients are configured to increase a first order gradient moment.

5. The method of claim 1 , wherein the step of applying the four RF pulses comprises the steps, in order, of:
(a) rotating a magnetization at the site from a selected one of the orthogonal axes, into a plane defined by two others of the orthogonal axes;
(b) providing a first refocus of the signal at the site;
(c) providing a second refocus of the signal at the site; and
(d) rotating the magnetization from the plane back into alignment with the selected one of the orthogonal axes.

6. The method of claim 1 , wherein for each of the plurality of orthogonal axes, the step of applying the plurality of motion sensitizing magnetic field gradients includes the steps of:
(a) applying a first motion sensitizing magnetic field gradient during a first predefined time interval between a first and a second of the RF pulses;
(b) applying at least one motion sensitizing magnetic field gradient during a second predefined time interval between the second and a third of the RF pulses; and
(c) applying a final motion sensitizing magnetic field gradient during a third predefined time interval between the third and a fourth of the RF pulses.

7. The method of claim 1 , wherein for each of the plurality of orthogonal axes, the step of applying the plurality of motion sensitizing magnetic field gradients includes the step of applying four alternating polarity motion sensitizing magnetic field gradients, with one of the four motion sensitizing magnetic field gradients being applied during a first predefined time interval between a first and second of the RF pulses, two of the motion sensitizing magnetic field gradients being applied during a second predefined time interval between the second and a third of the RF pulses, and one of the four motion sensitizing magnetic field gradients being applied during a third predefined interval between the third and a fourth of the RF pulses.

8. The method of claim 1 , wherein the step of applying the plurality of motion sensitizing magnetic field gradients is configured to suppress phase coherence among spins in the moving blood.

9. A non-transitory storage medium storing instructions readable and executable by a computing device to cause the computing device to:
(a) control a magnetic resonance imaging (MRI) device to administer a blood suppression preparatory sequence to a site in a subject, wherein the blood suppression preparatory sequence comprises:
(i) four radio frequency (RF) pulses applied to the site at predefined time intervals;
(ii) a plurality of motion sensitizing magnetic field gradients applied to the site, for each of a plurality of orthogonal axes; and
(iii) a spoiler magnetic field gradient applied to the site after a last of the four RF pulses; and

(b) control the MRI device to implement an image acquisition sequence after completion of the blood suppression preparatory sequence to acquire a magnetic resonance image signal that is usable to image the site;
wherein the plurality of motion sensitizing magnetic field gradients are configured to be applied so that a phase coherence among stationary spins at the site is retained.

10. An apparatus, comprising:
a memory in which are stored machine readable instructions; and
a processor that is operatively coupled to the memory and to a magnetic resonance imaging device, the processor configured to read and execute the machine readable instructions stored in the memory to perform operations including:
(i) controlling a magnetic resonance imaging (MRI) device to administer a preparatory sequence comprising:
(1) four radio frequency (RF) pulses applied to the site at predefined time intervals;
(2) a plurality of motion sensitizing magnetic field gradients applied to the site, for each of a plurality of orthogonal axes; and
(3) a spoiler magnetic field gradient applied to the site after a last of the four RF pulses; and

(ii) controlling the MRI device, to perform an image acquisition sequence to acquire a magnetic resonance image of the site with contribution to the magnetic resonance image from flowing blood at the site reduced by the administered preparatory sequence;
wherein the plurality of motion sensitizing magnetic field gradients are configured so that a phase coherence among stationary spins at the site is retained.

11. The apparatus of claim 10 , wherein the four RF pulses of the preparatory sequence are, in order:
(a) a first 90 degree RF pulse;
(b) a first 180 degree RF pulse;
(c) a second 180 degree RF pulse; and
(d) a second 90 degree pulse.

12. The apparatus of claim 11 , wherein the four RF pulses are applied to the site over a predefined preparation period, TE prep , using predefined time intervals between the first 90 degree RF pulse and the first 180 degree RF pulse, and between the second 180 degree RF pulse and the second 90 degree pulse that are equal to TE prep /4, and using a predefined time interval between the first 180 degree RF pulse and the second 180 degree RF pulse that is equal to TE prep /2.

13. The apparatus of claim 12 , wherein the plurality of motion sensitizing magnetic field gradients are configured to increase a first order gradient moment so as to suppress phase coherence among spins in the flowing blood.

14. The apparatus of claim 10 , wherein the four RF pulses applied to the site are configured to:
(a) rotate a magnetization at the site from a sel

Assignees

• Wang Jinnan
• Yarnykh Vasily
• Yuan Chun
• Univ Washington

Inventors

• Wang Jinnan
• Yarnykh Vasily
• Yuan Chun

Classifications

• G01R33/563

  of moving material, e.g. flow contrast angiography · CPC title

• G01R33/5617

  using RF refocusing, e.g. RARE · CPC title

• G01R33/56 Primary

  Image enhancement or correction, e.g. subtraction or averaging techniques {, e.g. improvement of signal-to-noise ratio and resolution} · CPC title

• G01R33/5607

  by reducing the NMR signal of a particular spin species, e.g. of a chemical species for fat suppression, or of a moving spin species for black-blood imaging · CPC title

• A61B5/05

  Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves (measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24) · CPC title