Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, United Kingdom.
Magn Reson Med. 2010 Nov;64(5):1440-5. doi: 10.1002/mrm.22522.
Measuring T(2) at 7.0 T is not trivial due to RF inhomogeneity effects, however, gradient echo sampling of a spin echo is insensitive to RF pulse errors, does not suffer from significant distortions, and allows T'(2) and T(2) to be estimated simultaneously. Gradient echo sampling of a spin echo results are relatively sensitive to noise and therefore fitting methods and timing parameters were optimized: a weighted linear fit reduced the errors in T(2) compared to a nonlinear fit, the optimum spin echo time was approximately equal to the expected T(2) and decreasing the number of gradient echoes minimized the error of the estimated T(2). T(2), T'(2), and T*(2) decreased with field strength in frontal gray matter, occipital gray matter, and white matter, with T(2) having a linear dependence (frontal gray matter: 87, 76, 47 ms, occipital gray matter: 80, 68, 46 ms and white matter: 80, 71, 47 ms at 1.5, 3.0 and 7.0 T, respectively).
在 7.0T 下测量 T(2)并不简单，因为存在射频不均匀性的影响，但是，自旋回波的梯度回波采样对射频脉冲误差不敏感，不受显著失真的影响，并且允许同时估计 T'(2)和 T(2)。自旋回波的梯度回波采样结果对噪声相对敏感，因此优化了拟合方法和定时参数：加权线性拟合比非线性拟合减少了 T(2)的误差，最佳自旋回波时间大约等于预期的 T(2)，减少梯度回波的数量可以最小化估计的 T(2)的误差。T(2)、T'(2)和 T*(2)随场强在额状灰质、枕状灰质和白质中降低，T(2)具有线性依赖性（额状灰质：1.5、3.0 和 7.0T 时分别为 87、76、47ms，枕状灰质：80、68、46ms，白质：80、71、47ms）。
