Systems and methods for reducing artifacts in MRI images

Patent metadata

Field	Value
Publication number	US-10634751-B2
Application number	US-201715721840-A
Country	US
Kind code	B2
Filing date	Sep 30, 2017
Priority date	Sep 30, 2017
Publication date	Apr 28, 2020
Grant date	Apr 28, 2020

Abstract

A method for modifying RF pulse infidelity is provided. The method may include obtaining a designed time-domain waveform. The method may also include directing a radio frequency power amplifier (RFPA) of a magnetic resonance imaging (MRI) scanner to generate an output RF pulse based on the designed time-domain waveform. The method may also include measuring an output time-domain waveform of the output RF pulse. The method may also include determining, based on the designed time-domain waveform and the output time-domain waveform, a modified time-domain waveform corresponding to an excitation RF pulse. The method may also include directing the MRI scanner to generate, using a waveform generator and the RFPA and based on the modified time-domain waveform, the excitation RF pulse to excite one or more slices of an object in an MRI scan.

First claim

What is claimed is:

1. A system, comprising:
one or more storage devices storing a set of instructions; and
one or more processors configured to communicate with the storage device, wherein when executing the set of instructions, the system is caused to:
obtain a designed time-domain waveform wherein the designed time-domain waveform is a scanning sequence;
direct a radio frequency power amplifier (RFPA) of a magnetic resonance imaging (MRI) scanner to generate an output RF pulse based on the designed time-domain waveform;
measure an output time-domain waveform of the output RF pulse;
determine, based on the designed time-domain waveform and the output time-domain waveform, a modified time-domain waveform corresponding to an excitation RF pulse wherein the modified time-domain waveform including a compensation time-domain waveform; and
direct the MRI scanner to generate, using a waveform generator and the RFPA and based on the modified time-domain waveform, the excitation RF pulse to excite one or more slices of an object in an MRI scan;
wherein to determine the modified time-domain waveform corresponding to the excitation RF pulse based on the designed time-domain waveform and the output time-domain waveform, the system is caused to:
transform the designed time-domain waveform into a designed frequency-domain waveform with one or more excitation bands;
transform the output time-domain waveform into the output frequency-domain waveform;
determine the one or more frequency-domain sidebands in the output frequency-domain waveform by comparing the designed frequency-domain waveform with the output frequency-domain waveform;
select a portion of the output frequency-domain waveform, the portion of the output frequency-domain waveform including the one or more frequency-domain sidebands but not the one or more excitation bands;
determine a compensation frequency-domain waveform based on the selected portion of the output frequency-domain waveform;
transform the compensation frequency-domain waveform into a compensation time-domain waveform; and
determine the modified time-domain waveform based on the compensation time-domain waveform and the designed time-domain waveform.

2. The system of claim 1 , wherein the modified time-domain waveform is closer to satisfying an execution capability criterion than the designed time-domain waveform, the execution capability criterion embodying a criterion for a refocusing flip angle of the designed RF pulse.

3. The system of claim 1 , wherein a phase difference between the selected portion of the output frequency-domain waveform and the compensation frequency-domain waveform is 180°.

4. The system of claim 1 , wherein to determine the modified time-domain waveform corresponding to the excitation RF pulse, the system is caused to:
repeatedly determine an updated time-domain waveform in an iteration process including a plurality of successive iterations until a termination criterion is satisfied, wherein the updated time-domain waveform determined at the end of the iteration process is the modified time-domain waveform.

5. The system of claim 4 , at least one of the plurality of iterations including:
determining the updated time-domain waveform based on the designed time-domain waveform and a previous output time-domain waveform, the previous time-domain waveform corresponding to the designed time-domain waveform in a first iteration of the iteration process or a previously updated time-domain waveform determined in a previous iteration, the updated time-domain waveform corresponding to an updated RF pulse;
directing the RFPA of the MRI scanner to generate the updated RF pulse; and
measuring an output time-domain waveform of the updated RF pulse.

6. The system of claim 5 , wherein at feast one of the plurality of iterations further includes:
determining an iteration count of iterations that have been performed;
determining that the iteration count is equal to or greater than a first threshold; and
terminating, based on the determination that the iteration count is equal to or greater than the first threshold, the iteration process.

7. The system of claim 5 , wherein at least one of the plurality of iterations further includes:
displaying, to a user, a frequency-domain waveform of an RF pulse generated by the RFPA based on the modified time-domain waveform updated in the at least one of the plurality of iterations;
receiving, from the user, an instruction related to the updated time-domain waveform determined in the at least one of the plurality of iterations; and
terminating, based on the received instruction, the iteration process.

8. The system of claim 7 , wherein the received instruction includes that the updated RF pulse generated by the RFPA based on the updated time-domain waveform generated in the at least one of the plurality of iterations is acceptable.

9. A method implemented on a computing device having one or more processors and one or more storage devices, the method comprising:
obtaining a designed time-domain waveform wherein the designed time-domain waveform is a scanning sequence;
directing a radio frequency power amplifier (RFPA) of a magnetic resonance imaging (MRI) scanner to generate an output RF pulse based on the designed time-domain waveform;
measuring an output time-domain waveform of the output RF pulse;
determining, based on the designed time-domain waveform and the output time-domain waveform, a modified time-domain waveform corresponding to an excitation RF pulse wherein the modified time-domain waveform including a compensation time-domain waveform; and
directing the MRI scanner to generate, using a waveform generator and the RFPA and based on the modified time-domain waveform, the excitation RF pulse to excite one or more slices of an object in an MRI scan;
wherein determining the modified time-domain waveform corresponding to the excitation RF pulse based on the designed time-domain waveform and the output time-domain waveform comprises:
transforming the designed time-domain waveform into a designed frequency-domain waveform with one or more excitation bands;
transforming the output time-domain waveform into an output frequency-domain waveform;
determining one or more frequency-domain sidebands in the output frequency-domain waveform by comparing the designed frequency-domain waveform with the output frequency-domain waveform;
selecting a portion of the output frequency-domain waveform, the portion of the output frequency-domain waveform including the one or more frequency-domain sidebands but not the one or more excitation bands;
determining a compensation frequency-domain waveform based on the selected portion of the output frequency-domain waveform;
transforming the compensation frequency-domain waveform into a compensation time-domain waveform; and
determining the modified time-domain waveform based on the compensation time-domain waveform and the designed time-domain waveform.

10. The method of claim 9 , wherein the modified time-domain waveform is closer to satisfying an execution capability criterion than the designed time-domain waveform, the execution capability criterion embodying a criterion for a refocusing flip angle of the designed RF pulse.

11. The method of claim 9 , wherein a phase difference between the selected portion of the output frequency-domain waveform and the compensation frequency-domain waveform is 180°.

12. The method of claim 9 , wherein determining the modified time-domain waveform corresponding to the excitation RF pulse comprises:
repeatedly determine an updated time-domain waveform in an iteration process including a plurality of suc

Assignees

• Uih America Inc

Inventors

• Zheng Yuan
• Ma Jinbo
• Ding Yu
• Wei Qing
• Shen Zhenhua

Classifications

• G01R33/5617 Primary

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

• G01R33/3607

  RF waveform generators, e.g. frequency generators, amplitude-, frequency- or phase modulators or shifters, pulse programmers, digital to analog converters for the RF signal, means for filtering or attenuating of the RF signal · CPC title

• G01R33/543

  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 title

• A61B5/055 Primary

  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging · CPC title

• G01R33/4835

  of multiple slices · CPC title