Water saturation shift referencing (WASSR) for chemical exchange saturation transfer (CEST) experiments.
Water saturation shift referencing (WASSR) for chemical exchange saturation transfer (CEST) experiments.
复制标题
DOI：
10.1002/mrm.21873
复制
发表时间：
2009-06
影响因子：
3.3
通讯作者：
van Zijl PC
中科院分区：
文献类型：
--
作者：
Kim M;Gillen J;Landman BA;Zhou J;van Zijl PC
化学交换满意度转移（CEST）是一种对比机制，利用基于交换的磁化转移（MT）在固体和水蛋白之间的效果与直接水满意度和常规MT过程竞争，并且通常只能通过对水的不对称分析进行量化饱和光谱（Z-spectrum）相对于水频率，这一过程对磁场不均匀敏感。结果表明，直接的水饱和成像可以测量每个体素中的绝对水频率，从而使Z-Spectra在voxel-ny-voxel基础上适当地居中，而不是空间B0场的最佳习得参数。使用蒙特卡洛模拟估算了参考”或“ WASSR”方法，后来在实验中确认了WASSR扫描宽度与直接宽度的最佳比率。信号与噪声比的频率误差小于1 Hz，将WASSR方法应用于研究糖原，其中3T羟基（OH）质子和块状水质子之间的化学位移差异很小（0.75 –1.25 ppm）认为CEST频谱在没有适当参考的情况下尚无定论。
Chemical exchange saturation transfer (CEST) is a contrast mechanism exploiting exchange-based magnetization transfer (MT) between solute and water protons. CEST effects compete with direct water saturation and conventional MT processes and generally can only be quantified through an asymmetry analysis of the water saturation spectrum (Z-spectrum) with respect to the water frequency, a process that is exquisitely sensitive to magnetic field inhomogeneities. Here, it is shown that direct water saturation imaging allows measurement of the absolute water frequency in each voxel, allowing proper centering of Z-spectra on a voxel-by-voxel basis independent of spatial B0 field variations. Optimal acquisition parameters for this “water saturation shift referencing” or “WASSR” approach were estimated using Monte Carlo simulations and later confirmed experimentally. The optimal ratio of the WASSR sweep width to the linewidth of the direct saturation curve was found to be 3.3–4.0, requiring a sampling of 16–32 points. The frequency error was smaller than 1 Hz at signal to noise ratios of 40 or higher. The WASSR method was applied to study glycogen, where the chemical shift difference between the hydroxyl (OH) protons and bulk water protons at 3T is so small (0.75–1.25 ppm) that the CEST spectrum is inconclusive without proper referencing.
登录
查看更多内容
影响因子：
3.3
作者：
SCHNEIDER, E;GLOVER, G
通讯作者：
GLOVER, G
影响因子：
3.3
作者：
Liu, Guanshu;Li, Yuguo;Pagel, Mark D.
通讯作者：
Pagel, Mark D.
影响因子：
3.3
作者：
Snoussi, K;Bulte, JWM;van Zijl, PCM
通讯作者：
van Zijl, PCM
影响因子：
158.5
作者：
Cline, GW;Petersen, KF;Shulman, GI
通讯作者：
Shulman, GI
影响因子：
3.1
作者：
Lagarias, JC;Reeds, JA;Wright, PE
通讯作者：
Wright, PE