Zhang Jing, Kolind Shannon H, Laule Cornelia, MacKay Alex L
UBC MRI Research Centre, Department of Radiology, University of British Columbia, Vancouver, BC, Canada.
Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, BC, Canada.
Magn Reson Med. 2015 Jan;73(1):223-32. doi: 10.1002/mrm.25125. Epub 2014 Feb 11.
Myelin water fraction is conventionally measured from the T2 decay curve. Recently, a steady-state approach entitled multicomponent-driven equilibrium single pulse observation of T1 /T2 (mcDESPOT) was employed for myelin water fraction mapping. However, no direct comparison between the established multiecho T2 relaxation method and mcDESPOT has been performed.
Gradient and spin echo (GRASE) acquired T2 decay curve and mcDESPOT measurements were acquired from 10 healthy volunteers using a 3T MRI. We compared myelin water fraction, transmit radio frequency field (B1 ), and T2 's of intra- and extracellular water obtained from both methods.
For all brain regions examined, myelin water fractions from mcDESPOT were significantly higher than those from multiecho GRASE. B1 maps were qualitatively similar between GRASE and mcDESPOT, but multicomponent T2 times were significantly different. To investigate the effect of exchange, mcDESPOT data were analyzed with and without exchange. When exchange was turned off, intra- and extracellular T2 times from mcDESPOT were roughly consistent with GRASE results; however, myelin water fractions derived from mcDESPOT were still significantly higher than those derived from GRASE.
Myelin water fraction values derived from mcDESPOT cannot be considered to be equivalent to those derived from T2 decay curve approaches.
传统上通过T2衰减曲线测量髓磷脂水分数。最近，一种名为多组分驱动平衡单脉冲T1/T2观测（mcDESPOT）的稳态方法被用于髓磷脂水分数成像。然而，尚未对已确立的多回波T2弛豫方法与mcDESPOT进行直接比较。
使用3T磁共振成像（MRI）从10名健康志愿者身上获取梯度和自旋回波（GRASE）序列的T2衰减曲线以及mcDESPOT测量数据。我们比较了两种方法获得的髓磷脂水分数、发射射频场（B1）以及细胞内和细胞外水的T2*值。
在所有检查的脑区中，mcDESPOT方法得到的髓磷脂水分数显著高于多回波GRASE方法得到的结果。GRASE和mcDESPOT方法的B1图谱在质量上相似，但多组分T2时间存在显著差异。为了研究交换的影响，对mcDESPOT数据分别进行了有交换和无交换的分析。当关闭交换时，mcDESPOT方法得到的细胞内和细胞外T2时间与GRASE结果大致一致；然而，mcDESPOT方法得到的髓磷脂水分数仍显著高于GRASE方法得到的结果。
不能认为mcDESPOT方法得到的髓磷脂水分数值与T2衰减曲线方法得到的结果等效。
