Department of Electrical and Computer Engineering, Auburn University, Auburn, Alabama, USA.
Auburn University MRI Research Center, Auburn University, Auburn, Alabama, USA.
NMR Biomed. 2024 Jan;37(1):e5042. doi: 10.1002/nbm.5042. Epub 2023 Sep 28.
Magnetic resonance spectroscopic imaging (MRSI) provides information about the spatial distribution of metabolites in the brain. These metabolite maps can be valuable in diagnosing central nervous system pathology. However, MRSI generally suffers from a long acquisition time, poor spatial resolution, and a low metabolite signal-to-noise ratio (SNR). Ultrahigh field strengths (≥ 7 T) can benefit MRSI with an improved SNR and allow high-resolution metabolic mapping. Non-Cartesian spatial-spectral encoding techniques, such as rosette spectroscopic imaging, can efficiently sample spatial and temporal domains, which significantly reduces the imaging time and enables high-resolution metabolic mapping in a clinically relevant scan time. In the current study, high-resolution (in-plane resolution of 2 × 2 mm ) mapping of proton ( H) metabolites in the human brain at 7 T, is demonstrated. Five healthy subjects participated in the study. Using a time-efficient rosette trajectory and short TR/TE free induction decay MRSI, high-resolution maps of H metabolites were obtained in a clinically relevant imaging time (6 min). Suppression of the water signal was achieved with an optimized water suppression enhanced through T1 effects approach and lipid removal was performed using L -regularization in the postprocessing. Spatial distributions of N-acetyl-aspartate, total choline, creatine, N-acetyl-aspartyl glutamate, myo-inositol, and glutamate were generated with Cramer-Rao lower bounds of less than 20%.
磁共振波谱成像（MRSI）提供了关于脑内代谢物空间分布的信息。这些代谢物图谱在诊断中枢神经系统病变方面具有重要价值。然而，MRSI 通常存在采集时间长、空间分辨率差和代谢物信噪比（SNR）低的问题。超高场强（≥7T）可以通过提高 SNR 来改善 MRSI，并允许进行高分辨率代谢映射。非笛卡尔空间-谱编码技术，如梅花形光谱成像，可以有效地对空间和时间域进行采样，从而显著缩短成像时间，并在临床相关的扫描时间内实现高分辨率代谢映射。在当前的研究中，在 7T 下演示了人脑中质子（ H）代谢物的高分辨率（平面分辨率为 2×2mm）映射。五名健康受试者参与了这项研究。使用高效的梅花形轨迹和短 TR/TE 自由感应衰减 MRSI，在临床相关的成像时间（6 分钟）内获得了高分辨率的 H 代谢物图谱。通过优化的通过 T1 效应增强的水抑制方法实现了对水信号的抑制，并在后期处理中使用 L-正则化去除脂质。通过生成 Cramer-Rao 下限小于 20%，生成了 N-乙酰天冬氨酸、总胆碱、肌酸、N-乙酰天冬氨酸谷氨酸、肌醇和谷氨酸的空间分布。
