Analysis of Flow and Motion Effects in Burst Imaging

脉冲串成像可以在100毫秒内获得磁共振（MR）图像。尽管其超快的特点，突发成像是非常敏感的运动的对象被成像。在读出方向上的运动在所获得的图像中产生显著的伪影。为了研究运动对猝发成像的影响，我们对匀速运动体模的MR信号进行了实验分析，并对猝发成像序列产生的MR信号进行了计算机模拟，实验数据分析和计算机模拟表明，运动对MR信号的相位有一定的影响，但对每个信号的相位变化并不均匀。这种运动效应是由于激发脉冲在猝发成像中的特殊应用而产生的。计算机模拟进一步表明，相位的变化可以通过简单的后处理方法进行校正，在此数据评估的基础上，我们提出了一种突发成像的运动校正方法，并将该方法应用于不同速度范围的运动体模实验数据。该方法成功地校正了信号的相位，校正后的图像消除了突发成像中运动引起的图像伪影。

Burst imaging can obtain a magnetic resonance (MR) image within 100 msec. In spite of its ultrafast feature, burst imaging is very sensitive to motion of the object to be imaged. The motion in the readout direction produces significant artifacts in the obtained image. To investigate the motion effects in burst imaging, we have analyzed the experimental MR signal obtained from a moving phantom with constant velocity and have performed a computer simulation of MR signal produced by burst imaging sequence.The analysis of the experimental data and the computer simulation on burst imaging signal demonstrated that the phase of the MR signal was affected by the motion but its change was not even for each signal. Such motion effect was originated from the characteristic use of excitation pulses in burst imaging. The computer simulation further suggested the change of the phase can be corrected by a simple post-processing method.Being based on such data assessment, we have proposed a motion correction method for burst imaging and the method was applied to experimental data of motion phantom with various range of velocity. The method have successfully correct the phase of the signal and the corrected image have removed the motion induced image artifact of burst imaging.