Human Brain Proton Metabolite Mapping at Short TE

描述(由申请人提供)： 高场磁共振波谱成像(MRSI)定量质子代谢产物的一个主要问题是从不均匀和变化的基线中分离代谢物共振。一些基线波动是由于体积不足的水和脂肪信号，而另一些变化是由于大分子的存在。我们提出了一系列措施来提高代谢产物和基线信号的分离能力，其中最重要的涉及利用包括紧密间隔的180度脉冲(CP脉冲串)的序列在不同TE时间获得一系列中等信噪比(S/N)频谱，以在采集之前减少强耦合自旋的J演化。这保留了强耦合共振在不同TE值处的频谱模式，即使由于T2弛豫导致的信号幅度衰减，该组频谱的同时拟合有望实现代谢物信号与基线的改进分离，并提供代谢物共振区域的更可靠的估计。包括改进CP脉冲串的双曲正割脉冲和具有对B1非均质性免疫的自旋回波脉冲级联，2)改进的垫片方法，3)改进的MRSI采集序列，4)改进的代谢物光谱处理方法，以及5)改进机构单位的代谢物定量，基于与组织分段的结构MRI数据的协同分析，最后将开发正常大脑的代谢物图谱，反映区域代谢物水平和变化。这一建议与合作伙伴IRPG关于共享程序、脉冲、数据和信息的建议相协调，以加强两个地点的研究。

DESCRIPTION (provided by applicant): A major problem in quantification of proton metabolites obtained by high field magnetic resonance (MR) spectroscopic imaging (MRSI) at short TE is separating the metabolite resonances from the uneven and varying baseline Some of the baseline fluctuations are due to out-of-volume water and lipid signals, while other variations are due to the presence of macromolecules We propose a series of measures to improve the ability to separate metabolite and baseline signals, the most important of which involves obtaining a series of moderate signal-to noise (S/N) spectra at differing TE times with a sequence that includes closely spaced 180 degrees pulses (CP pulse train) to reduce J evolution for strongly coupled spins prior to acquisition This preserves the spectral patterns for strongly coupled resonances at the different TE values even though the signal amplitudes decay due to T2 relaxation Simultaneous fitting of the suite of spectra is expected to enable improved separation of metabolite signals from baseline, and to provide more reliable estimates of metabolite resonance areas A number of additional measures including 1) improved RF pulses, including improvement of hyperbolic secant pulses and a spin echo pulse cascade with immunity to B1 inhomogenicity for the CP pulse train, 2) improved methods of shimming, 3) improved MRSI acquisition sequences, 4) improved methods for processing of metabolite spectra, and 5) improvements for metabolite quantification in institutional units, based on coanalysis with tissue segmented structural MRI data, are planned Finally, a metabolite atlas of normal brain, reflecting regional metabolite levels and variations, will be developed This proposal is coordinated with the partner IRPG proposal for sharing of programs, pulses, data, and information to enhance the research at both sites.