一种消除MRI拉链伪影的脉冲序列

A pulse sequence eliminating zipper artifact of MRI

背景:磁共振成像会产生各种类型的伪影,经常出现的有运动伪影、卷褶伪影、金属伪影、部分容积效应伪影、化学位移伪影、相位伪影和拉链伪影等,但由自旋回波序列成像过程中形成拉链伪影的控制和校正方法还未见报道。目的:通过分析自旋回波序列成像过程中拉链伪影的产生机制,探索出一种新的消除拉链伪影的脉冲序列。方法:编写标准SE序列得到标准图,编写伪影序列得到直线干扰图像和拉链伪影图,编写改进序列得到改进后的除拉链伪影图。结果与结论:5°-瞬间梯度-120°回波序列可得到直线干扰图像,90°-瞬间梯度-120°回波序列可得到拉链伪影图,而改进后序列90°-120°-瞬间梯度回波可彻底消除拉链伪影。结果提示,改进后的脉冲序列显示的图形效果彻底消除了拉链伪影。

BACKGROUND： Various artifacts are found to be appeared in the nuclear magnetic resonance; the frequently appearing ones are the motion artifacts, plait artifacts, metallic artifacts, partial volume effect artifacts, chemical shift artifacts, phase artifacts, zipper artifacts and so on. However, there is still has no report on the controlling and revising method of the zipper artifacts which is produced in the spin-echo sequence imaging process. OBJECTIVE： Based on the discussion of the mechanism of the production of zipper artifact in the spin-echo sequence imaging process, a new impulse sequence is worked out to avoid the zipper artifact. METHODS： Standard SE sequence was complied to obtain the standard image, and compiling the artifact sequence to obtain the linear disturbance image and zipper artifact image, compiling the modified sequence to obtain the modified zipper artifact image. RESULTS AND CONCLUSION： Usually, the linear disturbance image could obtained in the instantaneous gradient of 5 degree with the echo sequence of 120 degree, and the zipper artifact will be obtained in the instantaneous gradient of 90 degree with the echo sequence of 120 degree. Modified sequence instantaneous gradient of 90 degree with the echo sequence of 120 degree can completely eliminate zipper artifact. The interesting result obtained in this paper is that the zipper artifact can be totally avoided with this new impulse sequence.