Naji Nashwan, Sun Hongfu, Wilman Alan H
Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada.
School of Information Technology and Electrical Engineering, University of Queensland, Brisbane, Queensland, Australia.
Magn Reson Med. 2020 Sep;84(3):1486-1500. doi: 10.1002/mrm.28226. Epub 2020 Mar 3.
Quantitative susceptibility mapping (QSM) has been employed for both iron evaluation and segmentation of deep gray matter (DGM), but QSM sequences are not typically used in standard brain volumetric studies, which use T1-weighted magnetization-prepared rapid acquisition with gradient echo (MPRAGE) with short TE. Here, QSM produced directly from standard MPRAGE phase ( ) is evaluated for segmentation and quantification of highly iron-rich DGM regions.
Simulations were used to explore quality and possible limitations. In addition, QSM from a standard multi-echo gradient-echo ( ) was compared to in 40 healthy adults at 3T. DGM structures with weak contrast on MPRAGE magnitude were evaluated for improving segmentation with , with focus on the iron-rich globus pallidus (GP). Furthermore, susceptibility quantification was assessed on six DGM nuclei and compared to standard .
Limited by TE and signal-to-noise ratio, only iron-rich regions like GP and dentate nucleus produced adequate contrast on , confining applications to such regions. improved GP segmentation with mean Dice scores raised by 9.0%, and mean volumetric differences reduced by 9.7%. Simulations suggested that phase contrast-to-noise ratio (CNR) should be above 3.0 to attain segmentation improvement. For quantification purposes, higher CNR is required, and typical provided comparable estimates to in large iron-rich DGM nuclei.
Despite the short TE of standard MPRAGE, can improve GP segmentation over the use of MPRAGE magnitude alone and roughly quantify high-iron regions in DGM. Thus, reconstructing can be a useful addition to volumetric studies that rarely include standard .
定量磁化率成像（QSM）已用于铁含量评估和深部灰质（DGM）分割，但QSM序列通常不用于标准脑容积研究，标准脑容积研究使用具有短回波时间（TE）的T1加权磁化准备快速梯度回波序列（MPRAGE）。在此，对直接从标准MPRAGE相位（）生成的QSM进行评估，以用于对富含铁的DGM区域进行分割和定量分析。
采用模拟方法探究其质量和可能存在的局限性。此外，将来自标准多回波梯度回波序列（）的QSM与40名3T场强下的健康成年人的MPRAGE进行比较。对MPRAGE幅值上对比度较弱的DGM结构进行评估，以利用QSM改善分割效果，重点关注富含铁的苍白球（GP）。此外，对六个DGM核团进行磁化率定量分析，并与标准MPRAGE进行比较。
受TE和信噪比限制，只有像GP和齿状核这样富含铁的区域在QSM上产生了足够的对比度，因此其应用局限于这些区域。QSM改善了GP分割，平均骰子系数得分提高了9.0%，平均体积差异降低了9.7%。模拟结果表明，相位对比噪声比（CNR）应高于3.0才能实现分割改善。为了进行定量分析，需要更高的CNR，并且在富含铁的大型DGM核团中，典型的QSM提供了与MPRAGE相当的估计值。
尽管标准MPRAGE的TE较短，但与单独使用MPRAGE幅值相比，QSM仍可改善GP分割，并大致定量分析DGM中的高铁区域。因此，重建QSM对于很少包括标准QSM序列的容积研究可能是一个有用的补充。
