Method and system for measuring and calibrating imaging magnetic field in magnetic resonance apparatus

Patent metadata

Field	Value
Publication number	US-9784814-B2
Application number	US-201414155166-A
Country	US
Kind code	B2
Filing date	Jan 14, 2014
Priority date	May 21, 2013
Publication date	Oct 10, 2017
Grant date	Oct 10, 2017

Abstract

A method and a system for measuring and calibrating an imaging magnetic field in a magnetic resonance apparatus are provided. The method includes: providing the imaging magnetic field, where the imaging magnetic field is adapted for scanning an object; sampling a signal corresponding to the imaging magnetic field; processing the signal to obtain an actual magnetic field intensity; and calibrating based on a difference between the actual magnetic field intensity and a target magnetic field intensity. The system includes: a magnetic component, adapted for scanning an object to be imaged; a sampling unit, adapted for sampling a signal corresponding to the imaging magnetic field; a processing unit, adapted for processing the signal to obtain an actual magnetic field intensity; a calibration unit, adapted for calibrating based on a difference between the actual magnetic field intensity and a target magnetic field intensity; and a control unit, adapted for controlling the system.

First claim

What is claimed is:

1. An MRI method for measuring and calibrating an imaging magnetic field in a magnetic resonance apparatus connected to a computer, comprising:
providing the imaging magnetic field including a main imaging magnetic field and a gradient magnetic field, where the imaging magnetic field is configured to scan an object to be imaged;
sampling, by a probe, a signal corresponding to the imaging magnetic field;
processing, by the computer, the signal to obtain an actual magnetic field intensity;
obtaining, by the computer, an imaging magnetic field calibration value based on a difference between the actual magnetic field intensity and the target magnetic field intensity;
obtaining, by the computer, a current calibration value of the magnetic component according to the imaging magnetic field calibration value; and
calibrating, by the computer, the imaging magnetic field provided by the magnetic component based on the current calibration value of the magnetic component, where the difference between the actual magnetic field intensity and the target magnetic field intensity is divided into a uniform deviation, a linear deviation and a high-order deviation after calculation.

2. The method according to claim 1 , wherein the step of providing the imaging magnetic field comprises: providing the imaging magnetic field by a magnetic component in the magnetic resonance apparatus;
the step of sampling a signal corresponding to the imaging magnetic field comprises: providing a measurement RF signal to stimulate a monitoring sample and generate a measurement magnetic resonance signal corresponding to the imaging magnetic field; and sampling the measurement magnetic resonance signal; and
the step of processing the signal to obtain an actual magnetic field intensity comprises: obtaining the actual magnetic field intensity according to the measurement magnetic resonance signal based on magnetic resonance principle.

3. The method according to claim 2 , wherein the step of providing a measurement RF signal comprises: providing the measurement RF signal by a probe or a body coil fixed in the magnetic component.

4. The method according to claim 3 , wherein in the step of providing a measurement RF signal to stimulate a monitoring sample, the monitoring sample generates the measurement magnetic resonance signal corresponding to the imaging magnetic field.

5. The method according to claim 2 , wherein a method for forming the measurement RF signal comprises: adopting protons as the monitoring sample to generate the measurement RF signal, where the protons are same with or different from protons in an imaging process.

6. The method according to claim 1 , wherein the imaging magnetic field is measured and calibrated before scanning the object to be imaged.

7. The method according to claim 1 , wherein the imaging magnetic field is measured and calibrated in a process of scanning the object to be imaged.

8. The method according to claim 2 , wherein the step of sampling the measurement magnetic resonance signal comprises: obtaining the measurement magnetic resonance signal in a manner of multiple-stimulation and multiple-sampling, or in a manner of single-stimulation and multiple-sampling.

9. The method according to claim 2 , wherein the step of sampling the measurement magnetic resonance signal comprises: sampling a group of measurement magnetic resonance signals; and
the step of processing the signal to obtain an actual magnetic field intensity comprises: establishing a physical model of the actual magnetic field intensity based on the group of measurement magnetic resonance signals, so as to predict change of the actual magnetic field intensity.

10. The method according to claim 1 , wherein the magnetic component comprises a gradient coil;
the step of obtaining a current calibration value of the magnetic component according to the imaging magnetic field calibration value comprises: obtaining a current calibration value of the gradient coil according to the imaging magnetic field calibration value; and
the step of calibrating the imaging magnetic field provided by the magnetic component based on the current calibration value of the magnetic component comprises: calibrating a current of the gradient coil to calibrate the linear deviation.

11. The method according to claim 10 , wherein the magnetic component further comprises a shim coil;
the step of obtaining a current calibration value of the magnetic component according to the imaging magnetic field calibration value comprises: obtaining a current calibration value of the shim coil according to the imaging magnetic field calibration value; and
the step of calibrating the imaging magnetic field provided by the magnetic component based on the current calibration value of the magnetic component comprises: calibrating a current of the shim coil to calibrate the linear deviation and the high-order deviation.

12. The method according to claim 10 , wherein the magnetic component further comprises a drift supply coil for a main imaging magnetic field;
the step of obtaining a current calibration value of the magnetic component according to the imaging magnetic field calibration value comprises: obtaining a current calibration value of the drift supply coil for the main imaging magnetic field according to the imaging magnetic field calibration value; and
the step of calibrating the imaging magnetic field provided by the magnetic component based on the current calibration value of the magnetic component comprises: calibrating a current of the drift supply coil for the main imaging magnetic field to calibrate the uniform deviation.

13. The method according to claim 11 , wherein the magnetic component further comprises a drift supply coil for a main imaging magnetic field;
the step of obtaining a current calibration value of the magnetic component according to the imaging magnetic field calibration value comprises: obtaining a current calibration value of the drift supply coil for the main imaging magnetic field according to the imaging magnetic field calibration value; and
the step of calibrating the imaging magnetic field provided by the magnetic component based on the current calibration value of the magnetic component comprises: calibrating a current of the drift supply coil for the main imaging magnetic field to calibrate the uniform deviation.

14. The method according to claim 2 , wherein the magnetic component further performs image reconstruction; and
the step of performing calibration based on a difference between the actual magnetic field intensity and a target magnetic field intensity comprises: performing the image reconstruction according to data obtained by the actual magnetic field intensity in combination with the difference between the actual magnetic field intensity and the target magnetic field intensity, so as to output a calibrated image.

15. The method according to claim 1 , wherein the step of sampling a signal corresponding to the imaging magnetic field comprises: inducing a change of the imaging magnetic field to form an alternating electromotive force corresponding to the imaging magnetic field, and sampling the alternating electromotive force; and
the step of processing the signal to obtain an actual magnetic field intensity comprises: obtaining the actual magnetic field intensity according to the alternating electromotive force based on electromagnetic induction principle.

16. An MRI system for measuring and calibrating an imaging magnetic field in a magnetic resonance apparatus, comprising:
a magnetic component configured to s

Assignees

• Shanghai United Imaging Healthcare Co Ltd

Inventors

• Tsai Kunyu
• Zhang Weiguo
• Zhang Qiang

Classifications

• G01R33/56563 Primary

  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

• G01R33/58

  Calibration of imaging systems, e.g. using test probes {, Phantoms; Calibration objects or fiducial markers such as active or passive RF coils surrounding an MR active material} · CPC title

• G01R33/243

  Spatial mapping of the polarizing magnetic field · CPC title

• G01R35/005 Primary

  Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references (G01R33/0035, G01R35/002 take precedence) · CPC title