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Magnetic resonance imager

A gradient pulse, intensity technology, applied in magnetic resonance measurement, measurement using nuclear magnetic resonance imaging system, measurement device, etc., can solve the problem of image quality degradation, magnetization change, inability to accurately measure the distribution of static magnetic field inhomogeneity, etc. question

Inactive Publication Date: 2006-08-09
GE MEDICAL SYST GLOBAL TECH CO LLC
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Problems solved by technology

[0014] As mentioned above, there is a problem with the conventional static magnetic field inhomogeneity distribution measurement sequence SQJ that it cannot accurately measure the static magnetic field inhomogeneity distribution because the magnetization varies due to gradient pulses
[0015] Therefore, correct image correction cannot be performed, and the image quality will be significantly reduced, especially when an imaging method that utilizes the resonance frequency difference between water and fat is used in an MRI device with a medium-low intensity magnetic field (0.3-0.5T), such as CHESS (Chemical Substitution Selective Imaging) method, especially
[0016] In order to solve this problem, the inventors of the present invention studied the effect of using the device disclosed in Japanese Patent Application No. 2001-54510, but the distribution of the static magnetic field inhomogeneity cannot be measured very accurately only by using this device

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Embodiment approach

[0103] Although the present invention is applied to the static magnetic field non-uniformity distribution measurement method in the foregoing description, in general, the present invention can be applied to a pulse sequence for obtaining MR data. Specifically, by applying one of the following measures, the influence of the residual magnetization generated by the gradient pulse can be suppressed:

[0104] (1) Let the intensity of the phase reversal gradient pulse equal to half or roughly half the intensity of the phase encoding gradient pulse;

[0105] (2) Let the intensity of the slice reversal gradient pulse equal to half or roughly half of the intensity of the slice encoding gradient pulse;

[0106] (3) Apply a degaussing gradient pulse with an intensity equal to the intensity of the slice selective gradient pulse to the slice axis; and

[0107] (4) After the gradient pulse is read out, a degaussing gradient pulse with an intensity equal to that of the read gradient pulse is app...

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Abstract

For the purpose of thoroughly reducing the effect of residual magnetization caused by gradient pulses, the strength of a phase rewinding gradient is made half or about half of that of a phase encoding gradient; the strength of a slice rewinding gradient is made half or about half of that of a slice encoding gradient; a killer gradient having an intensity equal to that of the slice selective gradient is applied to the slice axis; and a killer gradient having an intensity equal to that of a readout gradient is applied to the frequency axis subsequent to the readout gradient.

Description

Technical field [0001] The invention relates to a static magnetic field inhomogeneity distribution measurement method, a static magnetic field homogenization method, an MR (magnetic resonance) data acquisition method and an MRI (magnetic resonance imaging) device, in particular to a static magnetic field inhomogeneity measurement method , Static magnetic field homogenization method, MR data acquisition method, and MRI device, which can completely reduce the residual magnetization effect generated by the gradient pulse. technical background [0002] A known measurement sequence SQJ of the inhomogeneity distribution of the static magnetic field is illustrated in FIG. 7. [0003] This static magnetic field inhomogeneity distribution measurement sequence SQJ uses a radio frequency pulse P1 and a slice selective gradient pulse Ss1; then a slice rephasing gradient pulse Sr1' is applied, and its intensity (amplitude) is equal to the slice selective gradient pulse Ss1 Intensity (amplitud...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): A61B5/055G01R33/20G01R33/48G01R33/387G01R33/565
CPCG01R33/56563G01R33/387G01R33/56518
Inventor 浅野健二小杉进
Owner GE MEDICAL SYST GLOBAL TECH CO LLC