Motion-Insensitive Determination of B1+ Amplitudes Based on the Bloch-Siegert Shift in Single Voxels of Moving Organs Including the Human Heart
Motion-Insensitive Determination of B1+ Amplitudes Based on the Bloch-Siegert Shift in Single Voxels of Moving Organs Including the Human Heart
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DOI：
10.1002/mrm.25763
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发表时间：
2016-05-01
影响因子：
3.3
通讯作者：
Boesch, Chris
中科院分区：
文献类型：
--
作者：
Dokumaci, Ayse Sila;Pouymayou, Bertrand;Boesch, Chris
目的：为了可靠地确定发射射频（B-1（+））场的幅度在运动器官，如肝脏和心脏，其中大多数当前的技术通常是不可行的。方法：B-1（+）场测量的基础上引起的Bloch-Siegert位移的一对费米脉冲在一个双触发的修改点解析光谱（PRESS）序列与运动补偿破碎梯度已被开发。序列的性能进行了测试，在移动体模和肌肉，肝脏，和6名健康志愿者的心脏，使用不同的发射/接收线圈的安排。结果：B-1（+）在移动体模的测定几乎是独立的类型和幅度的运动，并符合理论。在体内，如果费米脉冲的幅度选择在适当的水平之上，则重复测量导致非常小的方差系数（CV（肌肉中的CV为0.6%，肝脏中的CV为1.6%，心脏中的CV为2.3%，具有中等幅度的费米脉冲，以及具有更强费米脉冲的CV为1.2%）。所提出的序列示出了即使在具有挑战性的条件下（使用表面线圈的传输或在心脏中没有屏气的测量）也非常稳健地确定单个体素中的B-1（+）。(C)2015 Wiley Periodicals，Inc.
Purpose: To reliably determine the amplitude of the transmit radiofrequency (B-1(+)) field in moving organs like the liver and heart, where most current techniques are usually not feasible.Methods: B-1(+) field measurement based on the Bloch-Siegert shift induced by a pair of Fermi pulses in a double-triggered modified Point RESolved Spectroscopy (PRESS) sequence with motion-compensated crusher gradients has been developed. Performance of the sequence was tested in moving phantoms and in muscle, liver, and heart of six healthy volunteers each, using different arrangements of transmit/receive coils.Results: B-1(+) determination in a moving phantom was almost independent of type and amplitude of the motion and agreed well with theory. In vivo, repeated measurements led to very small coefficients of variance (CV) if the amplitude of the Fermi pulse was chosen above an appropriate level (CV in muscle 0.6%, liver 1.6%, heart 2.3% with moderate amplitude of the Fermi pulses and 1.2% with stronger Fermi pulses).Conclusion: The proposed sequence shows a very robust determination of B-1(+) in a single voxel even under challenging conditions (transmission with a surface coil or measurements in the heart without breath-hold). (C) 2015 Wiley Periodicals, Inc.