K space reconstruction method and device

A K-space, opposite direction technology, applied in magnetic resonance measurement, measurement using nuclear magnetic resonance imaging system, and magnetic variable measurement, etc., can solve the problems of limiting imaging speed, increasing time loss when collecting calibration data, and improving imaging speed. , to achieve the effect of eliminating artifacts and saving time.

Active Publication Date: 2014-12-03
SHANGHAI UNITED IMAGING HEALTHCARE
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Problems solved by technology

However, the acquisition of calibration data adds additional time consumption. For acquisitions with high multiple acceleration, the time spent in acquiring calibration data will greatly limit the imaging speed.

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  • K space reconstruction method and device

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Embodiment 1

[0045] Excite EPI (multishot EPI, MS-EPI) multiple times, and collect K-space data in parallel. Among them, after one RF pulse excitation, the readout gradient field is used to continuously switch to collect multiple gradient echoes, and to fill multiple phase encoding lines in K space, multiple RF pulse excitations and corresponding times of EPI acquisition and data roundabout filling are required to complete the entire process. Filling of K-space. The number of excitations required for MS-EPI depends on the K-space phase encoding step and the echo chain length (ETL). If the K-space phase encoding step is 128 and ETL=16, then 8 excitations are required.

[0046]Before the actual K-space data is collected, the K-space data to be collected is divided into multiple data groups, and the multiple data groups form a certain angle with each other in the frequency encoding direction, and some data overlap. For the convenience of description, this embodiment divides the K-space data...

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Abstract

The invention provides a K space reconstruction method comprising exciting echo planar imaging (EPI) sequence for many times and collecting K space data in parallel, wherein the collected data comprises at least two data groups, a certain angle in the frequency encoding direction is formed between every two data groups and overlap portions are formed between data groups; further dividing phase encoding lines in each data group into a first group and a second group according to the difference of collection directions, the phase encoding lines in the first group being opposite to the phase encoding lines in the second group in collection direction; adding each group to the K space for fixing, wherein a position, most associated with other groups already added to the K space, is found for fixing when each group is added; and carrying out undersampled data filling by utilizing optimized K space data to realize K space reconstruction. According to the K space reconstruction method and device, EPI artifact correction can be realized without collecting calibration data additionally, thereby saving collection time and improving imaging speed.

Description

technical field [0001] The invention relates to the field of magnetic resonance imaging, in particular to a K-space reconstruction method and device. Background technique [0002] Echo planar imaging (EPI) is based on frequency readout gradients in opposite directions to alternately acquire odd and even echoes of MR signals. Due to the polarization effect caused by factors such as magnetic sensitivity, chemical shift, and magnetic field inhomogeneity of the imaging object, the phase modulation of the K-space data is generated in the phase encoding. The phase offset of the signal receiving loop and the filter will cause a phase shift between the collected odd and even echoes. In addition, eddy currents caused by switching fields with high-speed gradients can also affect the accuracy of the echo timing. All these factors lead to obvious artifacts in the phase-encoding direction of the EPI image reconstructed by Fourier transform, which seriously damages the image quality. s...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R33/56
Inventor 翟人宽
Owner SHANGHAI UNITED IMAGING HEALTHCARE
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