A method of multiple-averaging artifact reduction for rapid spin echoes

Abstract

The invention provides a method of multiple-averaging artifact reduction for rapid spin echoes. The method comprises the steps of: 1) triggering a target scanning part by using FSE sequences twice toobtain K space data; 2) performing scanning collection by using an alternate K space filling method to obtain first K space data, wherein a T2 weighting function of corresponding signals changes gently in the whole K space; 3) performing scanning collection by using an alternate center-combined K space filling method to obtain second K space data, wherein a T2 weighting function of corresponding signals changes gently in a half area in the middle of the K space; 4) adding the K space data obtained through first collection and the second collection and then calculating the average, and performing image reconstruction for the average. An image obtained through the method has a high contrast ratio and artifacts caused by noise and random movement can be reduced.

Description

technical field [0001] The present invention relates to a method for multiple averaging of fast spin echoes to mitigate artifacts. Background technique [0002] K-space refers to the Fourier dual space of rectangular coordinate volume space, and K-trajectory is the projection curve of MR signals in K-space, which usually reveals the data acquisition method and possible artifacts. The K space is also the positioning space of the MR signal, but the points in the K space are not in one-to-one correspondence with the points in the original positioning space of the image. The position of the MR signal data in the K space is determined by the gradient timing structure of the pulse sequence. The area of ​​the gradient pulse within the time is determined. The signal data obtained by the gradient pulse with a small area (low phase encoding) will be placed in the center of the K space, and the signal data obtained by the gradient pulse area with a large gradient pulse (high phase enco...

AI Technical Summary

Problems solved by technology

[0003] In the prior art, one of the traditional K-space filling methods is the K-space partition filling method, taking the multi-shotFSE sequence as an example, such as figure 1 Shown is a simplified diagram, assuming PE = 36, there are 4 shot excitations, ETL = 9, a line represents the echo of a shot, and the arrow points to the center of K space. It can be seen from the figure that four shots are placed in sequence, each The nine echoes after the shot are placed sequentially. The signal intensity corresponding to the Fourier line on one side of the K-space is high, and the signal intensity corresponding to the Fourier line on the other side is almost consistent with the noise. The basic idea is that after an RF pulse excitation Acquire multiple echoes, i.e. each 90° pulse followed by multiple 180° pulses, e.g. figure 2 As shown, Gs is the layer selection gradient, Gp is ​​the phase encoding gradient, and Gr is the frequency encoding gradient, corresponding to each 180° pulse, the phase encoding also increases in turn and each increment is the same, and the number of echoes is the same as that of the 180° The number of RF pulses is equal. Although the scanning and imaging time can be greatly reduced by using this technology, due to the problem of T2 spin attenuation in the FSE method, the signal intensity corresponding to each Fourier line is lower than the previous line. Low until it is consistent with the noise at the end. In order to solve the above problems (that is, the signal strength difference on both sides is very large, and the signal strength jumps at the junction of two shots at the same time), the center acquisition method can be used, that is, first fill the center of k space, and then fill k The edge part of the space, so that the signal strength filled from the center becomes weaker and weaker until it is at the same level as the noise, so that the K-space boundary signal is zero, resulting in low spatial resolution of the image and accompanied by slight artifacts; or It is also possible to use alternate K-space filling methods alone. However, since motion or noise is random, it may occur in the data acquisition after each shot. This arrangement will cause too much storage in the center of K-space due to motion or noise. the disturbance

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