GE Global Research, Munich, Germany.
J Magn Reson. 2013 Feb;227:35-8. doi: 10.1016/j.jmr.2012.11.016. Epub 2012 Nov 29.
Scalar coupling relaxation, which is usually only associated with closely resonant nuclei (e.g., (79)Br-(13)C), can be a very effective relaxation mechanism. While working on hyperpolarized [5-(13)C]glutamine, fast liquid-state polarization decay during transfer to the MRI scanner was observed. This behavior could hypothetically be explained by substantial T(1) shortening due to a scalar coupling contribution (type II) to the relaxation caused by the fast-relaxing quadrupolar (14)N adjacent to the (13)C nucleus in the amide group. This contribution is only effective in low magnetic fields (i.e., less than 800 μT) and prevents the use of molecules bearing the (13)C-amide group as hyperpolarized MRS/MRI probes. In the present work, this hypothesis is explored both theoretically and experimentally. The results show that high hyperpolarization levels can be retained using either a (15)N-labeled amide or by applying a magnetic field during transfer of the sample from the polarizer to the MRI scanner.
标量偶合弛豫通常仅与近共振核(例如(79)Br-(13)C)有关,它可以是一种非常有效的弛豫机制。在研究高极化[5-(13)C]谷氨酰胺时,在转移到 MRI 扫描仪期间观察到快速的液相极化衰减。这种行为可以假设通过与酰胺基团中(13)C 核相邻的快速弛豫四极(14)N 对弛豫的标量偶合贡献(II 型)引起的实质性 T1 缩短来解释,这种贡献仅在低磁场中有效(即小于 800μT),并防止使用带有(13)C-酰胺基团的分子作为高极化 MRS/MRI 探针。在本工作中,从理论和实验两个方面探讨了这一假设。结果表明,使用(15)N 标记的酰胺或在从极化器向 MRI 扫描仪转移样品期间施加磁场,可以保留高的高极化水平。
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