Preibisch C, Deichmann R
Brain Imaging Center, University Hospital, Frankfurt, Germany.
Magn Reson Med. 2009 Jan;61(1):125-35. doi: 10.1002/mrm.21776.
There is increasing interest in quantitative T(1) mapping techniques for a variety of applications. Several methods for T(1) quantification have been described. The acquisition of two spoiled gradient-echo data sets with different flip angles allows for the calculation of T(1) maps with a high spatial resolution and a relatively short experimental duration. However, the method requires complete spoiling of transverse magnetization. To achieve this goal, RF spoiling has to be applied. In this work it is investigated whether common RF spoiling techniques are sufficiently effective to allow for accurate T(1) quantification. It is shown that for most phase increments the apparent T(1) can deviate considerably from the true value. Correct results may be achieved with phase increments of 118.2 degrees or 121.8 degrees. However, for these values the method suffers from instabilities. In contrast, stable results are obtained with a phase increment of 50 degrees. An algorithm is presented that allows for the calculation of corrected T(1) maps from the apparent values. The method is tested both in phantom experiments and in vivo by acquiring whole-brain T(1) maps of the human brain.
对于各种应用而言，人们对定量T(1)映射技术的兴趣与日俱增。已经描述了几种T(1)定量方法。采集具有不同翻转角的两个扰相梯度回波数据集能够计算出具有高空间分辨率且实验持续时间相对较短的T(1)图。然而，该方法要求完全消除横向磁化。为实现这一目标，必须应用射频扰相。在本研究中，探究了常见的射频扰相技术是否足以有效地实现准确的T(1)定量。结果表明，对于大多数相位增量，表观T(1)可能会与真实值有相当大的偏差。相位增量为118.2度或121.8度时可获得正确结果。然而，对于这些值，该方法存在不稳定性。相比之下，相位增量为50度时可获得稳定结果。提出了一种算法，可根据表观值计算校正后的T(1)图。该方法在体模实验中以及通过采集人脑的全脑T(1)图在体内进行了测试。
