Lawry T J, Karczmar G S, Weiner M W, Matson G B
Magnetic Resonance Unit, Veterans Administration Medical Center, San Francisco, California.
Magn Reson Med. 1989 Mar;9(3):299-314. doi: 10.1002/mrm.1910090302.
Computer simulations were used to evaluate the ISIS localization technique as implemented with both head and surface coils. The effects of chemical shift, B1 inhomogeneity, repetition time, T2 relaxation, a postacquisition saturation pulse, and a B1 insensitive observation pulse were examined. Integrals of ISIS signals over the sample volume showed that significant signal loss from the volume of interest (VOI) and contamination from outside the VOI can occur for both head and surface coil ISIS experiments. The results showed that the saturation pulse, order of the various ISIS acquisitions, and repetition time affect contamination but not signal loss. In addition, short T2 and high RF power can combine synergistically to degrade the selective inversion pulses, causing further contamination and signal loss.
利用计算机模拟来评估使用头部线圈和表面线圈实施的ISIS定位技术。研究了化学位移、B1不均匀性、重复时间、T2弛豫、采集后饱和脉冲以及B1不敏感观测脉冲的影响。样本体积上ISIS信号的积分表明，对于头部线圈和表面线圈的ISIS实验，感兴趣体积（VOI）会出现显著的信号损失，并且VOI外部会产生污染。结果表明，饱和脉冲、各种ISIS采集的顺序以及重复时间会影响污染，但不会影响信号损失。此外，短T2和高射频功率可协同作用，使选择性反转脉冲退化，导致进一步的污染和信号损失。
