Peters Andrew M, Brookes Matthew J, Hoogenraad Frank G, Gowland Penny A, Francis Susan T, Morris Peter G, Bowtell Richard
Sir Peter Mansfield Magnetic Resonance Center, School of Physics and Astronomy, University of Nottingham, NG7 2RD Nottingham, UK.
Magn Reson Imaging. 2007 Jul;25(6):748-53. doi: 10.1016/j.mri.2007.02.014. Epub 2007 Apr 25.
Measurements have been carried out in six subjects at magnetic fields of 1.5, 3 and 7 T, with the aim of characterizing the variation of T2* with field strength in human brain. Accurate measurement of T2* in the presence of macroscopic magnetic field inhomogeneity is problematic due to signal decay resulting from through-slice dephasing. The approach employed here allowed the signal decay due to through-slice dephasing to be characterized and removed from data, thus facilitating an accurate measurement of T2* even at ultrahigh field. Using double inversion recovery turbo spin-echo images for tissue classification, an analysis of T2* relaxation times in cortical grey matter and white matter was carried out, along with an evaluation of the variation of T2* with field strength in the caudate nucleus and putamen. The results show an approximately linear increase in relaxation rate R2* with field strength for all tissues, leading to a greater range of relaxation times across tissue types at 7 T that can be exploited in high-resolution T2*-weighted imaging.
已在6名受试者中于1.5、3和7特斯拉的磁场下进行了测量，目的是表征人脑T2随场强的变化。由于切片间去相位导致的信号衰减，在存在宏观磁场不均匀性的情况下准确测量T2存在问题。此处采用的方法能够表征并从数据中去除因切片间去相位导致的信号衰减，从而即使在超高场下也能准确测量T2*。使用双反转恢复快速自旋回波图像进行组织分类，对皮质灰质和白质中的T2弛豫时间进行了分析，并评估了尾状核和壳核中T2随场强的变化。结果表明，所有组织的弛豫率R2随场强近似呈线性增加，这使得在7特斯拉时不同组织类型的弛豫时间范围更大，可用于高分辨率T2加权成像。
