MR Center of Excellence, Department of Radiology, Medical University Vienna, A-1090 Wien, Lazarettgasse 14, Austria.
Eur J Radiol. 2013 May;82(5):745-51. doi: 10.1016/j.ejrad.2011.09.024. Epub 2011 Dec 10.
Phosphorous ((31)P) magnetization transfer (MT) experiments enable the non-invasive investigation of human muscle metabolism in various physiological and pathological conditions. The purpose of our study was to investigate the feasibility of time-resolved MT, and to compare the results of MT experiments at 3 T and 7 T. Six healthy volunteers were examined on a 3T and a 7 T MR scanner using the same setup and identical measurement protocols. In the calf muscle of all volunteers, four separate MT experiments (each ∼10 min duration) were performed in one session. The forward rate constant of the ATP synthesis reaction (kATP) and creatine kinase reaction (kCK), as well as corresponding metabolic fluxes (FATP, FCK), were estimated. A comparison of these exchange parameters, apparent T₁s, data quality, quantification precision, and reproducibility was performed. The data quality and reproducibility of the same MT experiments at 7 T was significantly higher (i.e., kATP 2.7 times higher and kCK 3.4 times higher) than at 3 T (p<0.05). The values for kATP (p=0.35) and kCK (p=0.09) at both field strengths were indistinguishable. Even a single MT experiment at 7 T provided better data quality than did a 4 times-longer MT experiment at 3T. The minimal time-resolution to reliably quantify both FATP and FCK at 7 T was ∼6 min. Our results show that MT experiments at 7 T can be at least 4 times faster than 3 T MT experiments and still provide significantly better quantification. This enables time-resolved MT experiments for the observation of slow metabolic changes in the human calf muscle at 7 T.
磷（31）P）磁化转移（MT）实验使人们能够在各种生理和病理条件下对人体肌肉代谢进行非侵入性研究。本研究旨在探讨时间分辨 MT 的可行性，并比较 3T 和 7T 下 MT 实验的结果。六名健康志愿者在 3T 和 7T 磁共振扫描仪上使用相同的设置和相同的测量方案进行检查。在所有志愿者的小腿肌肉中，在一次检查中进行了四次独立的 MT 实验（每次约 10 分钟）。估计了 ATP 合成反应（kATP）和肌酸激酶反应（kCK）的正向速率常数以及相应的代谢通量（FATP、FCK）。对这些交换参数、表观 T₁s、数据质量、定量精度和可重复性进行了比较。7T 下相同 MT 实验的数据质量和可重复性明显更高（即 kATP 高 2.7 倍，kCK 高 3.4 倍）（p<0.05）。两种场强下的 kATP（p=0.35）和 kCK（p=0.09）值无显著差异。即使在 7T 下进行单次 MT 实验，也能提供比在 3T 下进行 4 倍长的 MT 实验更好的数据质量。在 7T 下可靠地定量测定 FATP 和 FCK 的最小时间分辨率约为 6 分钟。我们的结果表明，7T 下的 MT 实验速度至少可以比 3T MT 实验快 4 倍，并且仍然可以提供更好的定量结果。这使得在 7T 下观察人体小腿肌肉中缓慢代谢变化的时间分辨 MT 实验成为可能。
