Khlebnikov Vitaliy, Geades Nicolas, Klomp Dennis W J, Hoogduin Hans, Gowland Penny, Mougin Olivier
Department of Radiology, University Medical Center Utrecht, Utrecht, the Netherlands.
Sir Peter Mansfield Imaging Center, School of Physics and Astronomy, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom.
Magn Reson Med. 2017 Jun;77(6):2280-2287. doi: 10.1002/mrm.26323. Epub 2016 Jul 25.
To compare two pulsed, volumetric chemical exchange saturation transfer (CEST) acquisition schemes: steady state (SS) and pseudosteady state (PS) for the same brain coverage, spatial/spectral resolution and scan time.
Both schemes were optimized for maximum sensitivity to amide proton transfer (APT) and nuclear Overhauser enhancement (NOE) effects through Bloch-McConnell simulations, and compared in terms of sensitivity to APT and NOE effects, and to transmit field inhomogeneity. Five consented healthy volunteers were scanned on a 7 Tesla Philips MR-system using the optimized protocols at three nominal B amplitudes: 1 μT, 2 μT, and 3 μT.
Region of interest based analysis revealed that PS is more sensitive (P < 0.05) to APT and NOE effects compared with SS at low B amplitudes (0.7-1.0 μT). Also, both sequences have similar dependence on the transmit field inhomogeneity. For the optimum CEST presaturation parameters (1 μT and 2 μT for APT and NOE, respectively), NOE is less sensitive to the inhomogeneity effects (15% signal to noise ratio [SNR] change for a B dropout of 40%) compared with APT (35% SNR change for a B dropout of 40%).
For the same brain coverage, spatial/spectral resolution and scan time, at low power levels PS is more sensitive to the slow chemical exchange-mediated processes compared with SS. Magn Reson Med 77:2280-2287, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
比较两种脉冲式容积化学交换饱和转移（CEST）采集方案：稳态（SS）和伪稳态（PS），用于相同的脑覆盖范围、空间/频谱分辨率和扫描时间。
通过Bloch-McConnell模拟对两种方案进行优化，以实现对酰胺质子转移（APT）和核Overhauser增强（NOE）效应的最大灵敏度，并在对APT和NOE效应的灵敏度以及对发射场不均匀性方面进行比较。在7特斯拉飞利浦磁共振系统上，使用优化方案对五名同意参与的健康志愿者在三个标称B幅度（1μT、2μT和3μT）下进行扫描。
基于感兴趣区域的分析表明，在低B幅度（0.7 - 1.0μT）下，与SS相比，PS对APT和NOE效应更敏感（P < 0.05）。此外，两个序列对发射场不均匀性的依赖性相似。对于最佳CEST预饱和参数（分别为APT的1μT和NOE的2μT），与APT（40%的B失谐导致35%的信噪比[SNR]变化）相比，NOE对不均匀性效应的敏感度较低（40%的B失谐导致15%的SNR变化）。
对于相同的脑覆盖范围、空间/频谱分辨率和扫描时间，在低功率水平下，与SS相比，PS对缓慢化学交换介导的过程更敏感。《磁共振医学》77:2280 - 2287，2017。© 2016作者。《磁共振医学》由Wiley Periodicals, Inc.代表国际磁共振医学学会出版。这是一篇根据知识共享署名 - 非商业性使用许可协议发布的开放获取文章，允许在任何媒介中使用、分发和复制，前提是原始作品得到适当引用且不用于商业目的。
