Hertel S A, Galvosas P
MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140, New Zealand.
MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140, New Zealand.
J Magn Reson. 2017 Feb;275:90-97. doi: 10.1016/j.jmr.2016.12.006. Epub 2016 Dec 16.
Efficient phase cycling schemes remain a challenge for NMR techniques if the pulse sequences involve a large number of rf-pulses. Especially complex is the Carr Purcell Meiboom Gill (CPMG) pulse sequence where the number of rf-pulses can range from hundreds to several thousands. Our recent implementation of Magnetic Resonance Pore Imaging (MRPI) is based on a CPMG rf-pulse sequence in order to refocus the effect of internal gradients inherent in porous media. While the spin dynamics for spin-1/2 systems in CPMG like experiments are well understood it is still not straight forward to separate the desired pathway from the spectrum of unwanted coherence pathways. In this contribution we apply Phase Incremented Echo Train Acquisition (PIETA) to MRPI. We show how PIETA offers a convenient way to implement a working phase cycling scheme and how it allows one to gain deeper insights into the amplitudes of undesired pathways.
如果脉冲序列包含大量射频脉冲,高效的相位循环方案对于核磁共振技术来说仍然是一个挑战。特别复杂的是 Carr Purcell Meiboom Gill(CPMG)脉冲序列,其中射频脉冲的数量可以从数百个到数千个不等。我们最近实现的磁共振孔隙成像(MRPI)基于CPMG射频脉冲序列,以便重新聚焦多孔介质中固有内部梯度的影响。虽然在类似CPMG实验中自旋 - 1/2系统的自旋动力学已得到很好的理解,但从不需要的相干路径频谱中分离出所需路径仍然并非易事。在本论文中,我们将相位递增回波串采集(PIETA)应用于MRPI。我们展示了PIETA如何提供一种方便的方法来实现有效的相位循环方案,以及它如何使人们能够更深入地了解不需要路径的幅度。