Zhang Jing, Kolind Shannon H, Laule Cornelia, MacKay Alex L
UBC MRI Research Centre, Department of Radiology, University of British Columbia, Vancouver, Canada.
Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, Canada.
Magn Reson Med. 2015 Nov;74(5):1327-35. doi: 10.1002/mrm.25520. Epub 2014 Nov 14.
A steady-state approach that was termed multicomponent driven equilibrium single pulse observation of T1 and T2 (mcDESPOT) has recently been proposed for myelin water fraction (fM) mapping in brain development and demyelinating diseases. However, fMs estimated by mcDESPOT are significantly higher than myelin water fraction derived from multiecho spin echo T2-decay curve approaches. Magnetization transfer (MT), enhanced by the use of short, relatively high amplitude radiofrequency (RF) pulses in mcDESPOT, may artifactually influence fM maps. Our goal was to investigate the role of MT in mcDESPOT.
mcDESPOT data was collected twice from three healthy volunteers using short RF pulses with higher MT effect and long RF pulses with lower MT effect. MR parameters from 11 white and gray regions were compared using a paired student t-test. Whole slice difference images were also compared.
MT effects had a substantial influence on the signal generated by the balanced steady-state free procession sequences used in mcDESPOT. However, these MT effects were not clearly evident in the fM values determined by the conventional two-pool mcDESPOT analysis.
The signal generated from mcDESPOT is sensitive to MT, but the extracted myelin water fractions are relatively insensitive to changes of MT.
最近提出了一种稳态方法，称为多组分驱动平衡单脉冲T1和T2观测（mcDESPOT），用于脑发育和脱髓鞘疾病中的髓鞘水分数（fM）映射。然而，通过mcDESPOT估计的fM值明显高于从多回波自旋回波T2衰减曲线方法得出的髓鞘水分数。在mcDESPOT中，通过使用短的、相对高幅度的射频（RF）脉冲增强的磁化传递（MT）可能会人为地影响fM图。我们的目标是研究MT在mcDESPOT中的作用。
使用具有较高MT效应的短RF脉冲和具有较低MT效应的长RF脉冲，从三名健康志愿者那里两次采集mcDESPOT数据。使用配对学生t检验比较11个白质和灰质区域的MR参数。还比较了全切片差异图像。
MT效应对mcDESPOT中使用的平衡稳态自由进动序列产生的信号有重大影响。然而，在传统的双池mcDESPOT分析确定的fM值中，这些MT效应并不明显。
mcDESPOT产生的信号对MT敏感，但提取的髓鞘水分数对MT的变化相对不敏感。
