MR图像Ghost伪影的校正  

Ghost Correction in MRI

作　　者：陈春晓[1] 罗立民[1] 陶华[1] 王世杰[1] 

机构地区：[1]东南大学生物医学工程系

出　　处：《中国生物医学工程学报》2005年第3期350-352,380,共4页Chinese Journal of Biomedical Engineering

基　　金：国家 973计划资助 (编号 :2 0 0 3CB71610 2 )。

摘　　要：原始K空间奇偶回波单独重建图像数据时,根据二维多项式拟合参考扫描各点相位漂移估计值对图像进行相位校证,可减轻伪影的影响。但在噪声较严重的情况下,校正后的图像仍含有较严重的残余伪影。按相位编码方向对图像数据采用基于最小二乘法多项式拟合的方法可减轻噪声对图像的干扰,再利用二维抑制Ghost伪影算法能更有效地消除EPI成像过程中由于涡流引起的伪影。该算法的缺点是会引起图像信息强度的变化及造成图像高频信息的衰减。但由于MRI图像主要集中为低频信息,且Ghost伪影信息强度不超过图像信息最大强度2 0 %时,该方法对图像信息的损失不会影响对病灶的识别。A residual ghost artifact in echo-plannar imaging (EPI) remains after the correction procedure based on twodimensional phasemodulation of the spectra of even or odd echoes. In this paper, a polynomial fit method is put forward to deal with the measured values along the phase-encoded direction before two-dimensional phase modulation to reduce the artifact. The polynomial fit method is based on the least square errors theory. Hewever the image of EPI mainly contain signals of low frequency, and if the level of the residual artifact is less than 20% of the image intensity, such losses are negligible in diagnosing.

关 键 词：磁共振成像 Ghosl伪影 自旋回波平面成像 

分 类 号：R445.2[医药卫生—影像医学与核医学]