Systems and methods for designing magnetic resonance imaging radio frequency pulses that are robust against physiological motion errors

• US 10,247,803 B2
• Filed: 04/24/2015
• Issued: 04/02/2019
• Est. Priority Date: 04/25/2014
• Status: Active Grant

• Current Assignee: Regents of The University of Minnesota (University of Minnesota)
• Original Assignee: Regents of The University of Minnesota (University of Minnesota)
• Inventors: Schmitter, Sebastian, van de Moortele, Pierre-Francois, Wu, Xiaoping, Ugurbil, Kamil
• Primary Examiner(s): Hoffa, Angela M
• Application Number:
  US14/696,099
• Publication Number:
  US 20150309147A1
• Time in Patent Office: 1,439 Days
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/7289 Retrospective gating, i.e. associating measured signals or images with a physiological event after the actual measurement or image acquisition, e.g. by simultaneously recording an additional physiological signal during the measurement or image acquisition
• CPC Class Codes: G01R 33/246 Spatial mapping of the RF magnetic field B1
• CPC Class Codes: G01R 33/443 Assessment of an electric or a magnetic field, e.g. spatial mapping, determination of a B0 drift or dosimetry
• CPC Class Codes: G01R 33/543 Control of the operation of the MR system, e.g. setting of acquisition parameters prior to or during MR data acquisition, dynamic shimming, use of one or more scout images for scan plane prescription G01R33/546 takes precedence
• CPC Class Codes: G01R 33/5612 Parallel RF transmission, i.e. RF pulse transmission using a plurality of independent transmission channels
• CPC Class Codes: G01R 33/56308 Characterization of motion or flow; Dynamic imaging
• CPC Class Codes: G01R 33/56325 Cine imaging
• CPC Class Codes: G01R 33/565 Correction of image distortions, e.g. due to magnetic field inhomogeneities
• CPC Class Codes: G01R 33/56509 due to motion, displacement or flow, e.g. gradient moment nulling G01R33/567 takes precedence
• CPC Class Codes: G01R 33/56563 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 Class Codes: G01R 33/5659 caused by a distortion of the RF magnetic field, e.g. spatial inhomogeneities of the RF magnetic field G01R33/56509, G01R33/56518, G01R33/56536 take precedence
• CPC Class Codes: G01R 33/567 gated by physiological signals , i.e. synchronization of acquired MR data with periodical motion of an object of interest, e.g. monitoring or triggering system for cardiac or respiratory gating
• CPC Class Codes: G01R 33/5673 Gating or triggering based on a physiological signal other than an MR signal, e.g. ECG gating or motion monitoring using optical systems for monitoring the motion of a fiducial marker
• CPC Class Codes: G01R 33/5676 Gating or triggering based on an MR signal, e.g. involving one or more navigator echoes for motion monitoring and correction

Abstract

Systems and methods for designing and/or using radio frequency (“RF”) pulses for in-vivo MRI applications, where the RF pulses are robust against errors due to physiological motion of organs during the respiratory cycle. For example, RF pulses are designed based on multi-channel B1+ maps correlated to different positions of the respiratory cycle.

Claims

1. A magnetic resonance imaging (MRI) system comprising:

a magnet system configured to generate a polarizing magnetic field about at least a region of interest (ROI) of a subject arranged in the MRI system, the ROI being subject to cyclical physiological motion including a plurality of different states of physiological motion;

a plurality of gradient coils configured to apply a gradient field with respect to the polarizing magnetic field;

a radio frequency (RF) system configured to apply RF excitation fields to the subject and acquire MR image data therefrom; and

a computer programmed to;

acquire a B₁⁺ calibration map for each of a plurality of selected ones of the plurality of different states of physiological motion in the subject, wherein each B₁⁺ calibration map is correlated with a state of the physiological motion in the subject during acquisition of the B₁⁺ calibration map;

using the B₁⁺ calibration maps and correlated state of the physiological motion in the subject, design an RF pulse waveform that reduces B1+ inhomogeneity at each correlated state of physiological motion;

control the plurality of gradient coils and the RF system to produce an RF field based on a portion of the RF pulse waveform to acquire the image data from the subject, wherein the portion of the RF pulse waveform is correlated with a state of physiological motion of the subject during acquisition of the image data; and

reconstruct an image of the subject from the image data.

2. The MRI system of claim 1, wherein the computer is further programmed to track a state of the physiological motion in the subject without performing a navigator pulse sequence.

3. The MRI system of claim 1, wherein the computer is further programmed to assemble the B₁⁺ calibration maps into groups of virtual slices within the ROI and, to design the RF pulse waveform, the computer is further programmed to simultaneously design the RF pulse waveform using the groups of virtual slices to reduce errors induced by the physiological motion in the ROI.

4. The MRI system of claim 3, wherein the computer is further programmed to simultaneously optimize the RF pulse waveform using the groups of virtual slices to minimize errors induced by the physiological motion in the ROI.

5. The MRI system of claim 1, wherein the computer is further programmed to design the RF pulse waveform as a parallel transmission RF pulse waveform.

6. The MRI system of claim 1, wherein the computer is further programmed to acquire B₀ calibration maps for each of a plurality of different states of physiological motion in a subject and use the B₀ calibration maps to design the RF pulse waveform.

7. The MRI system of claim 1, wherein the physiological motion is respiratory motion.