Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, UK.
Neuroimage. 2010 Jan 1;49(1):272-81. doi: 10.1016/j.neuroimage.2009.08.022. Epub 2009 Aug 14.
Magnetization transfer is an important source of contrast in magnetic resonance imaging which is sensitive to the concentration of macromolecules and other solutes present in the tissue. Magnetization transfer effects can be visualized in magnetization transfer ratio images or quantified via the z-spectrum. This paper presents methods of measuring the z-spectrum and of producing high-resolution MTR images and maps of z-spectrum asymmetry in vivo at 7 T, within SAR limits. It also uses a 3-compartment model to measure chemical exchange and magnetization transfer parameters from the z-spectrum data. The peak in the z-spectrum associated with chemical exchange between amide and water protons (amide proton transfer, APT, effects) is much more apparent at 7 T than at 3 T. Furthermore at 7 T quantitative APT results varied between the corpus callosum and other white matter structures, suggesting that quantitative APT imaging could be used as a method of measuring myelination. The results also suggest that chemical exchange is not responsible for the phase shift observed in susceptibility weighted images between grey matter and white matter.
磁化传递是磁共振成像中的一种重要对比源，对组织中大分子和其他溶质的浓度敏感。磁化传递效应可以在磁化传递比图像中可视化，或者通过 z 谱定量。本文介绍了在 7T 下，在 SAR 限制内测量 z 谱和产生高分辨率 MTR 图像和 z 谱不对称图谱的方法。它还使用三房室模型从 z 谱数据测量化学交换和磁化传递参数。与酰胺质子和水质子之间的化学交换相关的 z 谱峰（酰胺质子转移，APT 效应）在 7T 下比在 3T 下明显得多。此外，在 7T 下，胼胝体和其他白质结构之间的定量 APT 结果有所不同，这表明定量 APT 成像可用于测量髓鞘形成。结果还表明，化学交换不是在磁敏感加权图像中观察到的灰质和白质之间的相位偏移的原因。
