Improving the amplitude-modulated control experiment for multislice continuous arterial spin labeling
Improving the amplitude-modulated control experiment for multislice continuous arterial spin labeling
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DOI：
10.1002/mrm.20443
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发表时间：
2005-05-01
影响因子：
3.3
通讯作者：
Jansen, O
中科院分区：
文献类型：
--
作者：
Werner, R;Norris, DG;Jansen, O
在对照实验中使用调幅射频（RF）脉冲是一种经过验证的方法，可用于控制多层连续动脉自旋标记（CASL）实验中的非共振效应。这种方法也被称为双绝热反演。引入了单个半脉冲的绝热因子β（1/2）和一个新的无量纲参数α，该参数是由标记参数和流速得到的。这使得有可能区分三种不同的情况：1）在低a时，发生双重反转。2)在α>=类似于4的情况下，纵向磁化返回到z轴的效率取决于自旋穿过标记平面的中心时的振幅调制的相位。3)在中间区域，效率显示出不期望的波动。在Bloch方程模拟中，确定了三个优化参数集。接近理想的性能应该总是通过β（1/2）>=类似于2和α类似于π/β（1/2）的参数组合来实现。在志愿者研究中实现了效率的提高，显示了所建议的优化的实际应用。(c)2005 Wiley-Liss，Inc.
The use of an amplitude-modulated radiofrequency (RF) pulse for a control experiment is a proven method to control for off-resonance effects in multislice continuous arterial spin labeling (CASL) experiments. This method is also known as double adiabatic inversion. The adiabaticity factor of a single half-pulse, beta(1/2), and a new dimensionless parameter alpha, which is obtained from the labeling parameters and the flow velocity, are introduced. This makes it possible to distinguish three distinct cases: 1) With low a, a double inversion occurs. 2) With alpha >= similar to 4, the efficiency with which the longitudinal magnetization is returned to the z-axis depends on the phase of the amplitude modulation at the time the spins cross the center of the labeling plane. 3) In the intermediate region, the efficiency shows undesirable fluctuations. In a Bloch equation simulation, three optimized parameter sets are determined. Near ideal performance should always be achieved by combinations of parameters for which beta(1/2) >= similar to 2 and alpha similar to pi/beta(1/2). The efficiency increases were realized in a volunteer study, showing the practical application of the suggested optimization. (c) 2005 Wiley-Liss, Inc.