Niess Fabian, Roat Sigrun, Bogner Wolfgang, Krššák Martin, Kemp Graham J, Schmid Albrecht I, Trattnig Siegfried, Moser Ewald, Zaitsev Maxim, Meyerspeer Martin
Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria.
High Field MR Center, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
Magn Reson Med. 2022 Mar;87(3):1174-1183. doi: 10.1002/mrm.29061. Epub 2021 Oct 31.
Lactate is a key metabolite in skeletal muscle and whole-body physiology. Its MR visibility in muscle is affected by overlapping lipid signals and fiber orientation. Double-quantum filtered (DQF) H MRS selectively detects lactate at 1.3 ppm, but at ultra-high field the efficiency of slice-selective 3D-localization with conventional RF pulses is limited by bandwidth. This novel 3D-localized H DQF MRS sequence uses adiabatic refocusing pulses to unambiguously detect lactate in skeletal muscle at 7 T.
Lactate double-quantum coherences were 3D-localized using slice-selective Shinnar-Le Roux optimized excitation and adiabatic refocusing pulses (similar to semi-LASER). DQF MR spectra were acquired at 7 T from lactate phantoms, meat specimens with injected lactate (exploring multiple TEs and fiber orientations), and human gastrocnemius in vivo during and after exercise (without cuff ischemia).
Lactate was readily detected, achieving the full potential of 50% signal with a DQF, in solution. The effects of fiber orientation and TE on the lactate doublet (peak splitting, amplitude, and phase) were in good agreement with theory and literature. Exercise-induced lactate accumulation was detected with 30 s time resolution.
This novel 3D-localized H DQF MRS sequence can dynamically detect glycolytically generated lactate in muscle during exercise and recovery at 7 T.
乳酸是骨骼肌和全身生理学中的关键代谢物。其在肌肉中的磁共振可见性受重叠脂质信号和纤维取向的影响。双量子滤波（DQF）氢磁共振波谱法在1.3 ppm处选择性检测乳酸，但在超高场中，传统射频脉冲的切片选择性三维定位效率受带宽限制。这种新型的三维定位氢DQF磁共振波谱序列使用绝热重聚焦脉冲，在7T磁场下明确检测骨骼肌中的乳酸。
使用切片选择性Shinnar-Le Roux优化激发和绝热重聚焦脉冲（类似于半激光）对乳酸双量子相干进行三维定位。在7T磁场下，从乳酸模型、注射乳酸的肉类标本（探索多个回波时间和纤维取向）以及运动期间和运动后（无袖带缺血）的人体腓肠肌体内采集DQF磁共振波谱。
在溶液中，乳酸很容易被检测到，通过DQF可实现50%信号的全部潜力。纤维取向和回波时间对乳酸双峰（峰分裂、幅度和相位）的影响与理论和文献结果高度一致。以30秒的时间分辨率检测到运动诱导的乳酸积累。
这种新型的三维定位氢DQF磁共振波谱序列能够在7T磁场下动态检测运动和恢复过程中肌肉中糖酵解产生的乳酸。
