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Echo planar imaging method and system

A technology of planar echo imaging and reference echo, which is applied in medical science, measuring devices, instruments, etc., can solve the problems of inaccurate phase correction, poor reliability of phase correction results, and zero-order term estimation deviation, etc., to achieve accurate phase correction , Improve the operation speed, improve the effect of operation accuracy

Active Publication Date: 2017-08-11
SHANGHAI UNITED IMAGING HEALTHCARE
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Problems solved by technology

However, the reliability of the phase correction results obtained by the above item-by-item estimation method is poor, and a small deviation of the first-order term can lead to a large deviation in the estimation of the zero-order term, which in turn leads to inaccurate phase correction

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Embodiment 1

[0112] Multiple echo planar imaging data of the scanning part are obtained by multiple excitation EPI, and three reference echo signals are collected at the same time. The multiple echo planar imaging data include imaging data of odd echoes and imaging data of even echoes. The echo signals are respectively even signal, odd signal and even signal. Obtain the phase deviation correction parameters between the reference echo signals (usually the odd and even signals of adjacent reference echoes), and correct the phases of the imaging data of odd and even echoes in multiple echo signals according to the correction parameters deviation; finally, magnetic resonance images of the scanned site can be obtained from the multiple echo-planar imaging signals corrected for phase deviation.

[0113] The MRI reconstructed image can be decomposed into the sum of two images, which are respectively reconstructed from odd-numbered and even-numbered rows of K-space data. Assuming that the size of...

Embodiment 2

[0137] The correction methods of the echo-planar imaging sequences in this embodiment are generally the same, except that the correction parameter model is selected as a nonlinear model, and the similarity detection function is also different. Specifically: the correction parameter model selects a second-order function model containing zero-order items, first-order items, and second-order items:

[0138] θ=C 0 +C 1 ×X RO +C 2 ×X RO 2 (Formula 5)

[0139] Among them, X RO Indicates the coordinates of the frequency readout direction position; C 0 Indicates the phase correction parameter of the zero-order term; C 1 Indicates the phase correction parameter of the first-order term; C 2 Indicates the phase correction parameter of the second order term. The correction model contains three correction parameters, and the corresponding Hough space is a three-dimensional parameter space. In addition, since the phase of the echo signal has a periodicity of 2π, the length of ea...

Embodiment 3

[0149] When EPI is used to acquire multiple planar echo imaging data of the scanning part, several reference echo signals without phase encoding are collected. The reference echo signals can include odd signals and even signals, and those collected with the same gradient polarity are used for phase correction. The odd signal of the reference echo signal can be used to correct the echo-planar imaging data of the odd-numbered echo, and the even signal of the reference echo signal acquired with the same gradient polarity for phase correction can be used to correct the echo-planar imaging data of the odd-numbered echo The phase-corrected echo-planar imaging data is Fourier-transformed to obtain a magnetic resonance image of the scanned part.

[0150] In this embodiment, the multiple-excitation EPI acquires multiple echo signals of the scanning site, and simultaneously acquires at least four reference echo signals that have not undergone phase encoding, and the reference echo signal...

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Abstract

The invention discloses an echo planar imaging method, including: obtaining multiple echo planar imaging data of a scanned part and obtaining several reference echo signals that have not been subject to phase encoding; establishing a fitting model between the actual phase deviation of the reference echo signals and the readout direction position and establishing the Hoff space related to the parameters of the fitting model; based on the actual phase deviation of the reference echo signals and the readout direction position, determining the optimal parameter group in the Hoff space; according to fitting model and the optimal parameter group, correcting the echo planar imaging data; reconstructing the corrected echo planar imaging data and obtaining the magnetic resonance image of the scanned part. The echo planar imaging method of the invention can accurately correct the phases of an imaging signal. In addition, the invention also presents an echo planar imaging system.

Description

[0001] 【Technical field】 [0002] The present invention relates to the field of magnetic resonance imaging, in particular to an echo-planar imaging method and system. [0003] 【Background technique】 [0004] Magnetic Resonance Imaging (MRI) can image various parts of the human body from multiple angles and planes. It has high tissue resolution, spatial resolution, and no radiation damage. It is of great significance in medicine. Echo Planar Imaging (EPI) is one of the fastest MRI imaging technologies at present. It uses positive and negative frequency encoding gradients in the echo chain to collect data, and the encoding speed is rapidly improved. The EPI sequence can complete an image acquisition within tens of milliseconds. However, in MR imaging, the phase information is inevitably disturbed by various factors such as noise, eddy current, motion, temperature, inhomogeneity and drift of the static magnetic field, and chemical shifts caused by different components, thus disto...

Claims

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Application Information

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IPC IPC(8): G01R33/561G01R33/565A61B5/055
CPCA61B5/055G01R33/561G01R33/565
Inventor 周鑫魏青宋瑞波张卫国李强
Owner SHANGHAI UNITED IMAGING HEALTHCARE
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