Xu Xiang, Yadav Nirbhay N, Zeng Haifeng, Jones Craig K, Zhou Jinyuan, van Zijl Peter C M, Xu Jiadi
Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA.
Magn Reson Med. 2016 Jan;75(1):88-96. doi: 10.1002/mrm.25990. Epub 2015 Oct 7.
To use the variable delay multipulse (VDMP) chemical exchange saturation transfer (CEST) approach to obtain clean amide proton transfer (APT) and relayed Nuclear Overhauser enhancement (rNOE) CEST images in the human brain by suppressing the conventional magnetization transfer contrast (MTC) and reducing the direct water saturation contribution.
The VDMP CEST scheme consists of a train of RF pulses with a specific mixing time. The CEST signal with respect to the mixing time shows distinguishable characteristics for protons with different exchange rates. Exchange rate filtered CEST images are generated by subtracting images acquired at two mixing times at which the MTC signals are equal, while the APT and rNOE-CEST signals differ. Because the subtraction is performed at the same frequency offset for each voxel and the CEST signals are broad, no B0 correction is needed.
MTC-suppressed APT and rNOE-CEST images of human brain were obtained using the VDMP method. The APT-CEST data show hyperintensity in gray matter versus white matter, whereas the rNOE-CEST images show negligible contrast between gray and white matter.
The VDMP approach provides a simple and rapid way of recording MTC-suppressed APT-CEST and rNOE-CEST images without the need for B0 field correction.
使用可变延迟多脉冲（VDMP）化学交换饱和转移（CEST）方法，通过抑制传统的磁化传递对比（MTC）并减少直接水饱和贡献，在人脑获得清晰的酰胺质子转移（APT）和中继核Overhauser增强（rNOE）CEST图像。
VDMP CEST方案由一系列具有特定混合时间的射频脉冲组成。关于混合时间的CEST信号对于具有不同交换率的质子显示出可区分的特征。通过减去在两个混合时间采集的图像来生成交换率滤波后的CEST图像，在这两个混合时间MTC信号相等，而APT和rNOE-CEST信号不同。由于对每个体素在相同的频率偏移处进行减法，并且CEST信号很宽，因此不需要B0校正。
使用VDMP方法获得了人脑的MTC抑制的APT和rNOE-CEST图像。APT-CEST数据显示灰质相对于白质呈高信号，而rNOE-CEST图像显示灰质和白质之间的对比度可忽略不计。
VDMP方法提供了一种简单快速的方法来记录MTC抑制的APT-CEST和rNOE-CEST图像，而无需进行B0场校正。
