B1+ mapping near metallic hardware

Patent metadata

Field	Value
Publication number	US-12313710-B2
Application number	US-202318115610-A
Country	US
Kind code	B2
Filing date	Feb 28, 2023
Priority date	Mar 1, 2022
Publication date	May 27, 2025
Grant date	May 27, 2025

Abstract

A method can include obtaining a scaling factor for a location proximate a metallic object by optimizing a function of an acquired dataset and a simulated dataset. The simulated dataset can include a first signal from a first pulse having a first excitation flip angle and a first refocusing flip angle. The simulated dataset can include a second signal from a second pulse having a second excitation flip angle and a second refocusing flip angle.

First claim

What is claimed is:

1. A method, comprising:
obtaining a scaling factor corresponding to a ratio of actual B 1 + to nominal B 1 + for a location proximate a metallic object by minimizing a function of an acquired dataset and a simulated dataset; and
obtaining a B 1 + map for a region proximate the metallic object based on the scaling factor;
wherein the simulated dataset comprises:
a first signal from a first pulse having a first excitation flip angle and a first refocusing flip angle; and
a second signal from a second pulse having a second excitation flip angle and a second refocusing flip angle.

2. The method of claim 1 , wherein the acquired dataset is generated according to a slice encoding for metal artifact correction (SEMAC) method.

3. The method of claim 1 , further comprising:
sampling a first center of k y -k z space for the first pulse; and
sampling a second center of k y -k z space for the second pulse.

4. The method of claim 1 , wherein the scaling factor is a first scaling factor and the location is a first location, the method further comprising:
obtaining a second scaling factor for a second location proximate the metallic object by minimizing the function of the acquired dataset and the simulated dataset.

5. The method of claim 1 , wherein the simulated dataset comprises a third signal from a third pulse having a third excitation flip angle and a third refocusing flip angle.

6. The method of claim 1 , wherein:
the simulated dataset comprises a third signal from a third pulse having a third excitation flip angle and a third refocusing flip angle; and
the first excitation flip angle is 30° and the first refocusing flip angle is 90°, the second excitation flip angle is 60° and the second refocusing flip angle is 120°, and the third excitation flip angle is 90° and the third refocusing flip angle is 150°.

7. The method of claim 1 , wherein:
the simulated dataset comprises:
a third signal from a third pulse having a third excitation flip angle and a third refocusing flip angle; and
a fourth signal from a fourth pulse having a fourth excitation flip angle and a fourth refocusing flip angle.

8. The method of claim 1 , wherein the first pulse is different from the second pulse.

9. The method of claim 1 , wherein the metallic object is an implant.

10. The method of claim 1 , wherein the acquired dataset is generated according to turbo-spin echo imaging.

11. The method of claim 1 , further comprising:
estimating a spatial distribution of a B 1 + field for the region proximate the metallic object.

12. A magnetic resonance imaging system, comprising:
at least one processor; and
a memory, with computer code instructions stored thereon, the computer code instructions, when executed by the at least one processor, cause the at least one processor to:
obtain a scaling factor corresponding to a ratio of actual B 1 + to nominal B 1 + for a location proximate a metallic object by minimizing a function of an acquired dataset and a simulated dataset; and
obtain a B 1 + map for a region proximate the metallic object based on the scaling factor;

wherein the simulated dataset comprises:
a first signal from a first pulse having a first excitation flip angle and a first refocusing flip angle; and
a second signal from a second pulse having a second excitation flip angle and a second refocusing flip angle.

13. The magnetic resonance imaging system of claim 12 , wherein the acquired dataset is generated according to a slice encoding for metal artifact correction (SEMAC) method.

14. The magnetic resonance imaging system of claim 12 , wherein the computer code instructions, when executed by the at least one processor, cause the at least one processor to:
sample a first center of k y -k z space for the first pulse; and
sample a second center of k y -k z space for the second pulse.

15. The magnetic resonance imaging system of claim 12 , wherein the scaling factor is a first scaling factor and the location is a first location, and wherein the computer code instructions, when executed by the at least one processor, cause the at least one processor to:
obtain a second scaling factor for a second location proximate the metallic object by minimizing the function of the acquired dataset and the simulated dataset.

16. The magnetic resonance imaging system of claim 12 , wherein the simulated dataset comprises a third signal from a third pulse having a third excitation flip angle and a third refocusing flip angle.

17. The magnetic resonance imaging system of claim 12 , wherein the metallic object is an implant.

18. The magnetic resonance imaging system of claim 12 , wherein the acquired dataset is generated according to turbo-spin echo imaging.

Assignees

• Siemens Healthineers Ag
• Univ New York

Inventors

• Keerthivasan Mahesh Bharath
• Khodarahmi Iman

Classifications

• G01R33/56536

  due to magnetic susceptibility variations · CPC title

• G01R33/5617

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

• G01R33/5659

  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 title

• G01R33/586

  for optimal flip angle of RF pulses · CPC title

• G01R33/56554

  caused by acquiring plural, differently encoded echo signals after one RF excitation, e.g. correction for readout gradients of alternating polarity in EPI · CPC title