Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, UK.
NMR Biomed. 2013 Nov;26(11):1508-17. doi: 10.1002/nbm.2984. Epub 2013 Jun 26.
The aim of this study was to optimise a pulse sequence for high-resolution imaging sensitive to the effects of conventional macromolecular magnetisation transfer (MT(m)) and nuclear Overhauser enhancement (NOE), and to use it to investigate variations in these parameters across the cerebral cortex. A high-spatial-resolution magnetisation transfer-prepared turbo field echo (MT-TFE) sequence was designed to have high sensitivity to MT(m) and NOE effects, whilst being robust to B0 and B1 inhomogeneities, and producing a good point spread function across the cortex. This was achieved by optimising the saturation and imaging components of the sequence using simulations based on the Bloch equations, including exchange and an image simulator. This was used to study variations in these parameters across the cortex. Using the sequence designed to be sensitive to NOE and MT(m), a variation in signals corresponding to a variation in MT(m) and NOE across the cortex, consistent with a reduction in myelination from the white matter surface to the pial surface of the cortex, was observed. In regions in which the stria was visible on T2*-weighted images, it could also be detected in signals sensitive to MT(m) and NOE. There was greater variation in signals sensitive to NOE, suggesting that the NOE signal is more sensitive to myelination. A sequence has been designed to image variations in MT(m) and NOE at high spatial resolution and has been used to investigate variations in contrast in these parameters across the cortex.
本研究旨在优化一种脉冲序列，以实现对常规大分子磁化转移（MT(m)）和核奥弗豪瑟增强（NOE）效应敏感的高分辨率成像，并利用它来研究这些参数在大脑皮层中的变化。设计了一种高空间分辨率的磁化传递准备涡轮场回波（MT-TFE）序列，该序列对 MT(m)和 NOE 效应具有高灵敏度，同时对 B0 和 B1 不均匀性具有鲁棒性，并在皮层中产生良好的点扩散函数。这是通过使用基于布洛赫方程的模拟优化序列的饱和和成像分量来实现的，包括交换和图像模拟器。利用设计用于检测 NOE 和 MT(m)的序列，观察到与皮层表面从白质到脑膜表面的髓鞘形成减少相对应的信号变化，这与 MT(m)和 NOE 的变化一致。在 T2*-加权图像上可以看到纹状体的区域，也可以在对 MT(m)和 NOE 敏感的信号中检测到它。对 NOE 敏感的信号变化更大，表明 NOE 信号对髓鞘形成更敏感。已经设计了一种序列来以高空间分辨率成像 MT(m)和 NOE 的变化，并利用它来研究这些参数在皮层中的对比度变化。
