LOW N ACETYL & HIGH CHOLINE GRAY MATTER CONC IN ALZHEIMERS: COGNITIVE FUNCTIONS

按顺序通常是用来观察 单个体素内的代谢物。然而，类脂是共振性的。 用乳酸盐，在传统的新闻采集中，两个峰 不容易辨别。因此，理想的是 将高效的乳酸盐/脂类歧视融入印刷机 序列。方法：我们实现了一种两次乳酸过滤器， 在窄带和宽带之间交替打开180度脉冲 连续收购。90度激励之间的时间 脉搏，乳酸滤光器为1/2J(72ms)。我们把中心设在 光谱选择性乳酸滤光片在CH3上的频率 双份乳酸盐。第一序列的较窄的过滤器具有 带宽为+/-1.57PPM(100赫兹)，包括NAA和脂质。 第二序列的更宽的滤波器具有+/-7.83ppm的带宽 (500)赫兹，包括乳酸四重奏。乳酸盐双打是 在第二个序列中逆转，但其他代谢物是 不受影响。减去从这两个序列获取的数据， 只产生乳酸信号，从而抑制脂质。求和 从两个序列获取的数据产生另一个共振， 即NAA和血脂。结论：通过交织两个光谱 选择性180度射频脉冲，我们实现了乳酸/脂质的目标 在保留其他代谢物信息的同时进行辨别。 这种方法对于确定身份可能非常有用 单个体素中的乳酸(即使存在额外的脂类) 实验，避免了在其他地方获取额外数据的需要 回声时间通常是这样做的。

Introduction: The PRESS sequence is commonly used to observe the metabolites within a single voxel. However, lipids are co-resonant with lactate, and in a conventional PRESS acquisition the two peaks can not be easily distinguished. Hence, it is desirable to incorporate efficient lactate/lipid discrimination into a PRESS sequence. Methods: We implemented a two-shot lactate filter that alternates between a narrow and wide band 180 degree pulse on sequential acquisitions. The time between the 90 degree excitation pulse and the lactate filter is 1/2J (72ms). We set the center frequency of the spectrally selective lactate filter on the CH3 doublet of lactate. The narrower filter of the first sequence has a bandwidth of +/-1.57ppm (100Hz), which includes the NAA and lipids. The wider filter of the second sequence has a bandwidth of +/-7.83ppm (500)Hz, which includes the lactate quartet. The lactate doublet is reversed in the second sequence but the other metabolites are unaffected. Subtracting the data acquired from these two sequences, yields only the lactate signal, hence suppressing the lipids. Summing the data acquired from the two sequences, yields the other resonances, namely NAA and lipids. Conclusions: By interleaving two spectrally selective 180 degree RF pulses, we achieved the goal of lactate/lipid discrimination while keeping the information of the other metabolites. This method is potentially very useful for definitively identifying lactate (even in the presence of additional lipids) in a single voxel experiment, and avoids the need to acquire additional data at other echo times as is commonly done.