Lin W, Haacke E M, Tkach J A
Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri 63110.
Magn Reson Med. 1994 Nov;32(5):678-83. doi: 10.1002/mrm.1910320522.
Uniform fat saturation over a large region of interest remains a problem in time-of-flight (TOF) magnetic resonance angiography applications. We demonstrate that a variable echo time with an opposed phase value at low spatial slice select frequencies can effectively reduce most of the fat signal in an otherwise standard three-dimensional TOF acquisition. We evaluated this method at 1.5 T using a short TE = 5.3 ms and a long TE = 6.75 ms for different values of the slice encoding gradient (i.e., different kz values). Shorter echo time (TE = 5.3 msec) was used at higher spatial slice select frequencies, but all echoes have the same gradient structures. By keeping the number of slice encoding steps with longer echoes to a minimum, field inhomogeneity effects on flow compensation remained small. A magnetization transfer saturation pulse was used to suppress signal of brain parenchyma. Overall, highly uniform and selective fat signal reduction was obtained while maintaining superior flow compensation in all volunteer studies.
在飞行时间（TOF）磁共振血管造影应用中，在大感兴趣区域实现均匀的脂肪饱和仍然是一个问题。我们证明，在低空间切片选择频率下具有相反相位值的可变回波时间可以在其他方面为标准的三维TOF采集中有效减少大部分脂肪信号。我们在1.5 T场强下，针对不同的切片编码梯度值（即不同的kz值），使用短TE = 5.3 ms和长TE = 6.75 ms评估了该方法。在较高的空间切片选择频率下使用较短的回波时间（TE = 5.3 msec），但所有回波具有相同的梯度结构。通过将具有较长回波的切片编码步数保持在最小值，场不均匀性对流动补偿的影响仍然很小。使用磁化传递饱和脉冲来抑制脑实质信号。总体而言，在所有志愿者研究中，在保持优异流动补偿的同时，实现了高度均匀且选择性的脂肪信号减少。
