SHORT ECHO TIME DUALBAND SPATIAL-SPECTRAL PULSE SEQUENCE FOR BRAIN MRSI AT 3T

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。所列机构为中心机构，不一定为研究者机构。简介：1H磁共振波谱成像（1H MRSI）是测量脑代谢物的有用技术。双波段空间光谱（SPSP）脉冲已被设计为在3 T完全激发感兴趣的代谢物，部分激发水，同时抑制脂质。然而，在这些序列中，180 SPSP脉冲必须具有非线性相位（沿着频谱方向），以便保持低于RF峰值功率极限，因此PRESS激励中的两个180脉冲都相对较长。这将TE限制为大脑的最小90 ms。在这项研究中，使用的PRESS序列只有一个双波段空间频谱线性相位90脉冲和两个标准的空间180脉冲提出了大脑MRSI。该序列提供了光谱选择性，同时允许比现有的SPSP PRESS序列显著更短的回波时间。 方法和讨论：线性相位90？设计了一个双波段SPSP脉冲，它由21个线性相位子脉冲组成，可以激励5 mm厚的切片，脉冲的通带包括3.2ppm的胆碱和2.0ppm的NAA，同时抑制1.3ppm及以下的脂质。部分水带被设计为在4.7ppm处激发2%的水信号。最终脉冲持续时间为24 ms，导致TE=60 ms。双波段SPSP 90？脉冲在代谢物通带中具有非常低的涟漪，但在部分水通带中具有相当大的涟漪。然而，由于我们只使用水作为频率参考，而不关心其幅度，因此这种涟漪是可以容忍的。体模和体内研究证明新脉冲序列达到了目标设计参数。 参考文献：[1] Star-Lack JM，et al. Magn Reson Med 2000; 43：325-330. [2]Cunningham CH，et al. Magn Reson Med. 2005 May; 53（5）：1033-9. [3]Barker PB，et al. Magn Reson Med. 2001 May;45（5）：765-9.致谢：卢卡斯基金会，NIH RR 09784，

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: 1H Magnetic resonance spectroscopic imaging (1H MRSI) is a useful technique for measuring brain metabolites. Dualband spatial-spectral (SPSP) pulses have been designed at 3T for fully exciting the metabolites of interest, partially exciting water, while suppressing lipids. However, in these sequences, the 180¿ SPSP pulses must have nonlinear phase (along the spectral direction) in order to stay below RF peak power limits and consequently both 180¿ pulses in the PRESS excitation are relatively long. This limits TE to a minimum of 90 ms for the brain. In this study, the use of a PRESS sequence with only one dualband spatial-spectral linear phase 90¿ pulse and two standard spatial 180¿ pulses is proposed for brain MRSI. This sequence provides spectral selectivity while allowing significantly shorter echo times than existing SPSP PRESS sequences for the brain. Methods and Discussion: A linear phase 90¿ dualband SPSP pulse was designed using twenty one linear phase subpulses that could excite a slice as thin as 5 mm. The passband for the pulse encompassed choline at 3.2 ppm to NAA at 2.0 ppm while suppressing the lipids at 1.3 ppm and below. The partial water band was designed to excite 2% of the water signal at 4.7 ppm. The final pulse duration was 24 ms resulting in TE=60 ms. The dualband SPSP 90¿ pulse had very low ripple in the metabolite passband but considerable ripple in the partial water passband. However, since we are only using water as a frequency reference and not concerned with its magnitude, this ripple is tolerable. Phantom and in vivo studies demonstrate the new pulse sequence achieved the targeted design parameters. References: [1] Star-Lack JM, et al. Magn Reson Med 2000; 43:325-330. [2] Cunningham CH, et al. Magn Reson Med. 2005 May; 53(5):1033-9. [3] Barker PB, et al. Magn Reson Med. 2001 May;45(5):765-9. Acknowledgements: Lucas Foundation, NIH RR09784,