Simicic Dunja, Alves Brayan, Mosso Jessie, Briand Guillaume, Lê Thanh Phong, van Heeswijk Ruud B, Starčuková Jana, Lanz Bernard, Klauser Antoine, Strasser Bernhard, Bogner Wolfgang, Cudalbu Cristina
CIBM Center for Biomedical Imaging, Lausanne, Switzerland.
Animal Imaging and Technology, École Polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland.
NMR Biomed. 2025 Feb;38(2):e5304. doi: 10.1002/nbm.5304.
Magnetic resonance spectroscopic imaging (MRSI) enables the simultaneous noninvasive acquisition of MR spectra from multiple spatial locations inside the brain. Although H-MRSI is increasingly used in the human brain, it is not yet widely applied in the preclinical setting, mostly because of difficulties specifically related to very small nominal voxel size in the rat brain and low concentration of brain metabolites, resulting in low signal-to-noise ratio (SNR). In this context, we implemented a free induction decay H-MRSI sequence (H-FID-MRSI) in the rat brain at 14.1 T. We combined the advantages of H-FID-MRSI with the ultra-high magnetic field to achieve higher SNR, coverage, and spatial resolution in the rat brain and developed a custom dedicated processing pipeline with a graphical user interface for Bruker H-FID-MRSI: MRS4Brain toolbox. LCModel fit, using the simulated metabolite basis set and in vivo measured MM, provided reliable fits for the data at acquisition delays of 1.30 ms. The resulting Cramér-Rao lower bounds were sufficiently low (< 30%) for eight metabolites of interest (total creatine, N-acetylaspartate, N-acetylaspartate + N-acetylaspartylglutamate, total choline, glutamine, glutamate, myo-inositol, and taurine), leading to highly reproducible metabolic maps. Similar spectral quality and metabolic maps were obtained with one and two averages, with slightly better contrast and brain coverage due to increased SNR in the latter case. Furthermore, the obtained metabolic maps were accurate enough to confirm the previously known brain regional distribution of some metabolites. The acquisitions proved high reproducibility over time. We demonstrated that the increased SNR and spectral resolution at 14.1 T can be translated into high spatial resolution in H-FID-MRSI of the rat brain in 13 min using the sequence and processing pipeline described herein. High-resolution H-FID-MRSI at 14.1 T provided robust, reproducible, and high-quality metabolic mapping of brain metabolites with minimal technical limitations.
磁共振波谱成像（MRSI）能够从脑内多个空间位置同时无创采集磁共振波谱。尽管氢质子磁共振波谱成像（H-MRSI）在人类脑部的应用日益广泛，但在临床前研究中尚未得到广泛应用，主要原因是与大鼠脑内非常小的名义体素大小以及脑代谢物浓度低相关的困难，导致信噪比（SNR）较低。在此背景下，我们在14.1 T磁场下在大鼠脑中实施了自由感应衰减氢质子磁共振波谱成像序列（H-FID-MRSI）。我们将H-FID-MRSI的优势与超高磁场相结合，以在大鼠脑中实现更高的信噪比、覆盖范围和空间分辨率，并开发了一个带有图形用户界面的定制专用处理流程，用于布鲁克H-FID-MRSI：MRS4Brain工具箱。使用模拟代谢物基集和体内测量的水抑制（MM）进行LCModel拟合，在1.30 ms的采集延迟下为数据提供了可靠的拟合。对于八种感兴趣的代谢物（总肌酸、N-乙酰天门冬氨酸、N-乙酰天门冬氨酸 + N-乙酰天门冬氨酰谷氨酸、总胆碱、谷氨酰胺、谷氨酸、肌醇和牛磺酸），所得的克拉美罗下界足够低（< 30%），从而产生高度可重复的代谢图谱。单平均和双平均获得了相似的谱质量和代谢图谱，由于后者信噪比增加，对比度和脑覆盖范围略好。此外，获得的代谢图谱足够准确，能够确认一些代谢物先前已知的脑区分布。这些采集证明了随时间的高重现性。我们证明，使用本文所述的序列和处理流程，在13分钟内，14.1 T磁场下增加的信噪比和谱分辨率可以转化为大鼠脑H-FID-MRSI中的高空间分辨率。14.1 T磁场下的高分辨率H-FID-MRSI提供了强大、可重复且高质量的脑代谢物代谢图谱，技术限制最小。
