Fehlner Andreas, Hirsch Sebastian, Weygandt Martin, Christophel Thomas, Barnhill Eric, Kadobianskyi Mykola, Braun Jürgen, Bernarding Johannes, Lützkendorf Ralf, Sack Ingolf, Hetzer Stefan
Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany.
J Magn Reson Imaging. 2017 Jul;46(1):134-141. doi: 10.1002/jmri.25516. Epub 2016 Oct 20.
To improve the resolution of elasticity maps by adapting motion and distortion correction methods for phase-based magnetic resonance imaging (MRI) contrasts such as magnetic resonance elastography (MRE), a technique for measuring mechanical tissue properties in vivo.
MRE data of the brain were acquired with echo-planar imaging (EPI) at 3T (n = 14) and 7T (n = 18). Motion and distortion correction parameters were estimated using the magnitude images. The real and imaginary part of the complex MRE data were corrected separately and recombined. The width of the point-spread function (PSF) and the position variability were calculated. The images were normalized to the Montreal Neurological Institute (MNI) anatomical template. The gray-to-white matter separability of the elasticity maps was tested.
Motion correction sharpened the |G*| maps as demonstrated by a narrowing of the PSF by 0.78 ± 0.51 mm at 7T and 0.52 ± 0.63 mm at 3T. The amount of individual head motion during MRE acquisition correlated with the decrease in the width of the PSF at 7T (r = 0.53, P = 0.025) and at 3T (r = 0.69, P = 0.006) and with the increase of gray-to-white matter separability after motion correction at 7T (r = 0.64, P = 0.0039) and at 3T (r = 0.57, P = 0.0319). Improved spatial accuracy after distortion correction results in a significant increase in separability of gray and white matter stiffness (P = 0.0067), especially in inferior parts of the brain suffering from strong B inhomogeneities.
We demonstrate that our method leads to sharper images and higher spatial accuracy, raising the prospect of the investigation of smaller brain areas with increased sensitivity in studies using MRE.
1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:134-141.
通过采用适用于基于相位的磁共振成像（MRI）对比（如磁共振弹性成像（MRE），一种用于在体内测量组织力学特性的技术）的运动和畸变校正方法，提高弹性图的分辨率。
在3T（n = 14）和7T（n = 18）场强下，采用回波平面成像（EPI）采集脑部的MRE数据。利用幅度图像估计运动和畸变校正参数。对复MRE数据的实部和虚部分别进行校正并重新组合。计算点扩散函数（PSF）的宽度和位置变异性。将图像归一化到蒙特利尔神经学研究所（MNI）解剖模板。测试弹性图的灰质与白质可分离性。
运动校正使|G*|图锐化，7T场强下PSF变窄0.78±0.51mm，3T场强下为0.52±0.63mm。MRE采集过程中个体头部运动量与7T（r = 0.53，P = 0.025）和3T（r = 0.69，P = 0.006）场强下PSF宽度的减小相关，且与7T（r = 0.64，P = 0.0039）和3T（r = 0.57，P = 0.0319）场强下运动校正后灰质与白质可分离性的增加相关。畸变校正后空间精度的提高导致灰质和白质硬度可分离性显著增加（P = 0.0067），尤其是在受强磁场不均匀性影响的脑下部区域。
我们证明我们的方法能产生更清晰的图像和更高的空间精度，提高了在使用MRE的研究中以更高灵敏度研究更小脑区的可能性。
1 技术效能：1期 J. MAGN. RESON. IMAGING 2017;46:134 - 141。
