MP2RAGE, a self bias-field corrected sequence for improved segmentation and T1-mapping at high field
MP2RAGE, a self bias-field corrected sequence for improved segmentation and T1-mapping at high field
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DOI：
10.1016/j.neuroimage.2009.10.002
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发表时间：
2010-01-15
期刊：
影响因子：
5.7
通讯作者：
Gruetter, Rolf
中科院分区：
文献类型：
--
作者：
Marques, Jose P.;Kober, Tobias;Gruetter, Rolf
在高静磁场（B₀）下人体磁共振图像中可观察到的发射B₁⁺场的大空间不均匀性严重损害图像质量。为了在脑部T₁加权图像中克服这种影响，对磁化准备快速梯度回波（MPRAGE）序列进行了修改，以在不同的反转时间生成两种不同的图像，即MP2RAGE。通过以一种新颖的方式组合这两种图像，有可能创建出T₁加权图像，其中结果图像没有质子密度对比、T₂⁺对比、接收偏置场以及一阶发射场不均匀性。利用布洛赫方程对MP2RAGE序列参数进行了优化，以使脑组织之间单位时间的对比度噪声比最大化，并使B₁⁺在空间中的变化影响最小化。在3T和7T下获得了具有高解剖质量和出色脑组织区分度的图像，适用于分割和基于体素的形态测量等应用。从这些在12分钟内采集的T₁加权图像中，通常在7T下以亚毫米体素分辨率（各向同性0.65 - 0.85毫米）计算出高分辨率的3D T₁图。T₁图在体模实验中得到了验证。在人体中，7T下获得的白质（WM）的T₁值为1.15±0.06秒，灰质（GM）的T₁值为1.92±0.16秒，与在较低空间分辨率下获得的文献值非常吻合。在3T下，以各向同性1毫米体素在8分钟内采集全脑图像，所获得的T₁值（白质为0.81±0.03秒，灰质为1.35±0.05秒）再次被发现与文献中的值非常吻合。（C）2009爱思唯尔公司。保留所有权利。
The large spatial inhomogeneity in transmit B, field (B-1(+)) observable in human MR images at hi h static magnetic fields (B-0) severely impairs image quality. To overcome this effect in brain T-1-weighted images the, MPRAGE sequence was modified to generate two different images at different inversion times MP2RAGE By combining the two images in a novel fashion, it was possible to create T-1-weigthed images where the result image was free of proton density contrast, T-2* contrast, reception bias field, and, to first order transmit field inhomogeneity.MP2RAGE sequence parameters were optimized using Bloch equations to maximize contrast-to-noise ratio per unit of time between brain tissues and minimize the effect of B-1(+) variations through space. Images of high anatomical quality and excellent brain tissue differentiation suitable for applications such as segmentation and voxel-based morphometry were obtained at 3 and 7 T.From such T-1-weighted images, acquired within 12 min, high-resolution 3D T-1 maps were routinely calculated at 7 T with sub-millimeter voxel resolution (0.65-0.85 mm isotropic). T-1 maps were validated in phantom experiments. In humans, the T, values obtained at 7 T were 1.15 +/- 0.06 s for white matter (WM) and 1.92 +/- 0.16 s for grey matter (GM), in good agreement with literature values obtained at lower spatial resolution. At 3 T, where whole-brain acquisitions with 1 mm isotropic voxels were acquired in 8 min the T-1 values obtained (0.81 +/- 0.03 S for WM and 1.35 +/- 0.05 for GM) were once again found to be in very good agreement with values in the literature. (C) 2009 Elsevier Inc. All rights reserved.