永磁磁共振扩散加权平面回波成像涡流伪影校正

Eddy Currents Artifacts Correction in Diffusion-Weighted Echo-Planar Imaging for Permanent MRI Scanner

研究了涡流对永磁磁共振扩散加权平面回波成像的影响,提出了一种针对永磁磁共振成像系统的涡流补偿算法,并对扩散加权EPI序列由于剩余涡流引起的相位误差提出了一种补偿方法.在0. 35 T永磁型磁共振成像系统上对算法进行了验证,不同的梯度方向经过涡流预加重补偿后,涡流最少也会降至未补偿前的1/15.对涡流补偿和未补偿的模体扩散加权EPI图像进行了比较,经过两次补偿后,图像几何畸变会降低5%,图像伪影会降低1/3.实验结果表明,所提出的算法可以有效抑制因涡流引起的扩散加权EPI伪影及畸变.

The effect of eddy currents on diffusion-weighted echo-planar imaging(EPI)was investigated for permanent magnetic resonance imaging(MRI)scanner.An automatic eddy currents calibration algorithm was presented,and a compensation method for phase errors caused by residual eddy currents in diffusion-weighted EPI was proposed.The method was tested and validated on a 0.35 T permanent magnet MRI scanner.For three different gradient directions after pre-emphasis compensation,the eddy currents reduced to at least 1/15 of that before compensation.The diffusion-weighted EPI images with and without eddy currents compensation were compared.After two times of compensations,the geometric distortion was reduced by 5%and artifacts was reduced by 1/3.The experimental results showed that the proposed algorithm can effectively suppressed the diffusion-weighted EPI artifacts and distortions caused by eddy currents.