Short symmetric and highly selective asymmetric first and second order gradient modulated offset independent adiabaticity (GOIA) pulses for applications in clinical MRS and MRSI.
Short symmetric and highly selective asymmetric first and second order gradient modulated offset independent adiabaticity (GOIA) pulses for applications in clinical MRS and MRSI.
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DOI：
10.1016/j.jmr.2022.107247
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发表时间：
2022-08
期刊：
影响因子：
--
通讯作者：
de Graaf RA
中科院分区：
文献类型：
--
作者：
Kumaragamage C;Coppoli A;Brown PB;McIntyre S;Nixon TW;De Feyter HM;Mason GF;de Graaf RA
梯度调制RF脉冲，特别是梯度偏移独立绝热（GOIA）脉冲，由于其B1峰振幅和相关功率需求较低，相对于非调制绝热全通道脉冲，在高场临床磁共振波谱和光谱成像（MRS/MRSI）中越来越受到关注。在这项工作中，我们描述了两种GOIA射频脉冲的发展：1)一种低功耗，3.0 ms宽带均匀速率平滑截断（WURST）调制RF脉冲，带宽为15 kHz，兼容临床可行的峰值B1振幅0.87 kHz（或20 μT）； 2)一种高选择性的非对称6.66 ms RF脉冲，带宽为20 kHz，旨在实现单面，分数过渡宽度仅为1.7%。通过仿真和实验研究了3ms GOIA-WURST射频脉冲中射频和梯度调制（GM）波形之间的电位异步效应。结果表明，当使用较大的RF偏移量来实现平移时，RF和GM函数之间的20+ μs的异步性会大大降低反演性能。提出了一种基于投影的方法，可以在临床前/临床MR系统上快速校准RF和GM异步。非对称GOIA脉冲在多脉冲OVS序列中实现，以实现功率高效，高选择性和B1和t1无关的颅外脂质抑制信号。开发的GOIA脉冲利用线性梯度调制（X， Y， Z梯度场）和二阶场调制（Z2， X2Y2梯度场）为MRS和MRSI采集提供椭圆形状的兴趣区域。两种描述的GOIA-RF脉冲具有重要的临床价值；其中，3.0 ms GOIA- wurst脉冲有利于实现短TE激光定位质子MRS/MRSI序列，非对称GOIA RF脉冲可用于高选择性外体积信号抑制，以便以全强度对颅外近端组织脂质进行探测。
Gradient modulated RF pulses, especially gradient offset independent adiabaticity (GOIA) pulses, are increasingly gaining attention for high field clinical magnetic resonance spectroscopy and spectroscopic imaging (MRS/MRSI) due to the lower peak B1 amplitude and associated power demands achievable relative to its non-modulated adiabatic full passage counterparts. In this work we describe the development of two GOIA RF pulses: 1) A power efficient, 3.0 ms wideband uniform rate with smooth truncation (WURST) modulated RF pulse with 15 kHz bandwidth compatible with a clinically feasible peak B1 amplitude of 0.87 kHz (or 20 μT), and 2) A highly selective asymmetric 6.66 ms RF pulse with 20 kHz bandwidth designed to achieve a single-sided, fractional transition width of only 1.7%. Effects of potential asynchrony between RF and gradient-modulated (GM) waveforms for 3 ms GOIA-WURST RF pulses was evaluated by simulation and experimentally. Results demonstrate that a 20+ μs asynchrony between RF and GM functions substantially degrades inversion performance when using large RF offsets to achieve translation. A projection-based method is presented that allows a quick calibration of RF and GM asynchrony on pre-clinical/clinical MR systems. The asymmetric GOIA pulse was implemented within a multi-pulse OVS sequence to achieve power efficient, highly-selective, and B1 and T1-independent signal suppression for extracranial lipid suppression. The developed GOIA pulses were utilized with linear gradient modulation (X, Y, Z gradient fields), and with second-order-field modulations (Z2, X2Y2 gradient fields) to provide elliptically-shaped regions-of-interest for MRS and MRSI acquisitions. Both described GOIA-RF pulses have substantial clinical value; specifically, the 3.0 ms GOIA-WURST pulse is beneficial to realize short TE sLASER localized proton MRS/MRSI sequences, and the asymmetric GOIA RF pulse has applications in highly selective outer volume signal suppression to allow interrogation of tissue proximal to extracranial lipids with full-intensity.
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影响因子：
2.9
作者：
通讯作者：
--
影响因子：
2.9
作者：
de Graaf RA;Brown PB;De Feyter HM;McIntyre S;Nixon TW
通讯作者：
Nixon TW
影响因子：
2.9
作者：
Maudsley AA;Andronesi OC;Barker PB;Bizzi A;Bogner W;Henning A;Nelson SJ;Posse S;Shungu DC;Soher BJ
通讯作者：
Soher BJ
影响因子：
7.4
作者：
de Graaf, Robin A.;Chowdhury, Golam M. I.;Behar, Kevin L.
通讯作者：
Behar, Kevin L.
影响因子：
3.3
作者：
Ordidge, RJ;Wylezinska, M;Franconi, F
通讯作者：
Franconi, F