Wood M L, Silver M, Runge V M
Department of Radiation Oncology, New England Medical Center, Boston, Massachusetts 02111.
Magn Reson Imaging. 1987;5(6):455-63. doi: 10.1016/0730-725x(87)90379-1.
The FLASH technique for fast magnetic resonance (MR) imaging often employs strong magnetic field gradients, called spoiler gradients, to dephase the transverse magnetization after it has been measured. Otherwise, image artifacts can develop. The effectiveness of spoiler gradients at suppressing these artifacts was evaluated experimentally on two-dimensional MR images of a uniform phantom and patients. It was informative to compare the magnetization immediately before the RF excitation in each phase encoding step. Only spoiler gradients in the slice selection direction were effective. Spoiler gradients that decreased steadily from a large amplitude in the first phase encoding step to zero in the last minimized the transverse magnetization and suppressed the image artifact, without changing the image contrast.
用于快速磁共振（MR）成像的FLASH技术通常采用强磁场梯度，即扰相梯度，在测量横向磁化后使其失相。否则，会产生图像伪影。在均匀体模和患者的二维MR图像上通过实验评估了扰相梯度抑制这些伪影的有效性。比较每个相位编码步骤中射频激发前的磁化情况很有意义。只有层面选择方向上的扰相梯度有效。从第一个相位编码步骤中的大幅度稳定下降到最后一个步骤中降为零的扰相梯度能使横向磁化最小化并抑制图像伪影，同时不改变图像对比度。
