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Phase correction method and magnetic resonance imaging system

A phase correction and imaging technology, which is applied in the direction of using the nuclear magnetic resonance imaging system for measurement, magnetic resonance measurement, measurement of magnetic variables, etc., and can solve the problems of complex pulse sequence and complex control.

Inactive Publication Date: 2007-09-05
GE MEDICAL SYST GLOBAL TECH CO LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

So the pulse sequence is more complicated, so the control is complicated

Method used

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  • Phase correction method and magnetic resonance imaging system
  • Phase correction method and magnetic resonance imaging system
  • Phase correction method and magnetic resonance imaging system

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no. 1 example

[0087] Figure 1 is a block diagram of an MRI system according to an embodiment of the present invention.

[0088] In the MRI system 100, the magnet assembly 1 has a space portion (hole) in which a target is inserted, and the following components are provided to surround the space portion: a permanent magnet 1p that applies a constant main magnetic field to the target, a gradient magnetic field coil that generates a gradient magnetic field 1g (the gradient magnetic field coil has X-, Y-, and Z-axis coils, and the combination of these fields forms the layer selection axis, readout axis, and phase encoding axis), RF pulses are emitted to excite nuclear spins within the target The transmitter coil 1t and the receiver coil 1r receive the NMR signal from the target. The gradient magnetic field coil 1g, the transmitting coil 1t, and the receiving coil 1r are connected to the gradient magnetic field driving circuit 3, the RF power amplifier 4, and the preamplifier 5, respectively. A ...

no. 2 example

[0116] (Equation 1) and (Equation 2) can be replaced by the following formulas:

[0117] (equation 4)

[0118] φ0cor(n, m)=φ0NAV(n, 1)-φblock×(n-1) / N

[0119] (equation 5)

[0120] φ1cor(n,m)=φ1NAV(n,1)

[0121] FIG. 6 is a conceptual diagram showing the corresponding relationship between imaging data F(n, m) and correction data H(n, j) used in the phase correction process.

[0122] FIG. 7 is an explanatory view showing a phase error of imaging data f''(n, m) after phase correction.

[0123] The first term of φ0cor(n,m) of (Equation 4) and φ1cor(n,m) of (Equation 5) correct the motion phase error (black arrow). The second term of φ0cor(n,m) of (Equation 4) corrects the magnetic field inhomogeneity phase error (white arrow). As a result, the phase errors of the imaging data f''(n, m) are all the same and vary linearly to eliminate artifacts.

no. 3 example

[0125] can be replaced by the following formula (equation 1):

[0126] (equation 6)

[0127] φ0cor(n, m)=φ0NAV(n, (m-1)%2+1)+φblock×2×int{(m-1) / 2}

[0128] Here int{} is a function (rounding function) to take out the integer part.

[0129] Use (Equation 2) as it is.

[0130] FIG. 8 is an explanatory view showing a phase error of imaging data f''(n, m) after phase correction.

[0131] The first term of φ0cor(n,m) of (Equation 6) and φ1cor(n,m) of (Equation 2) correct the motion phase error (black arrow). The second term of φ0cor(n,m) of (Equation 6) corrects the magnetic field inhomogeneity phase error (white arrow). As a result, the phase errors of the imaging data f''(n, m) are all equal, thereby eliminating artifacts.

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Abstract

In order to correct motion and magnetic field inhomogeneity phase errors, inverting data collecting read gradients Nr1 and Nr2 are applied to collect correcting data H (n, 1) and H (n, 2) corresponding to focused navigation echoes Ne1 and Ne2, data collecting read gradients r1, . . . , rM which are inverted alternately are applied, and phase encode gradients pdn, p2, . . . , pM are applied at inverting, thereby collecting imaging data F (n, 1), . . . , F (n, M) corresponding to the focused imaging echoes e1, . . . , eM. This sequence is repeated for n=1, . . . , N while changing the magnitude of the phase encode gradient pdn, whereby data F (1, 1) to F (N, M) for filling a k space are collected. Based on the correcting data H (n, 1) and H (n, 2), the imaging data F (n, 1), . . . , F (n, M) are phase corrected.

Description

technical field [0001] The present invention relates to a phase correction method and an MRI (magnetic resonance imaging) system, more particularly, to a phase correction method and an MRI system capable of correcting motion phase errors and simplifying pulse sequences. technical background [0002] Figure 18 shows a basic example of a pulse sequence for the multishot diffusion enhanced EPI (Echo Plane Imaging) method. [0003] In this pulse sequence, an excitation pulse RF90 and a layer selection gradient SG90 are applied. MPG (Motion Detection Gradient) pulse MPG is then applied. An inverse RF pulse RF180 and a layer selection gradient SG180 are applied. Then apply the MPG pulse MPG. Apply a phase encoding gradient pdn. Continuously apply data-acquisition read gradients r1,...,rm alternately reversed as positive or negative, apply phase-encoding gradients p2,...,pM when reversed, and sample them timed to continuously focus on the first echo e1 to the Mth echo eM in or...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): A61B5/055G01R33/48G01R33/54G01R33/561
CPCG01R33/56554A61B5/055
Inventor 池崎吉和
Owner GE MEDICAL SYST GLOBAL TECH CO LLC