Magnetic susceptibility-induced echo-time shifts: Is there a bias in age-related fMRI studies?
Magnetic susceptibility-induced echo-time shifts: Is there a bias in age-related fMRI studies?
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DOI：
10.1002/jmri.25347
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发表时间：
2017-01
影响因子：
4.4
通讯作者：
Sutton, Bradley P.
中科院分区：
文献类型：
--
作者：
Ngo, Giang-Chau;Wong, Chelsea N.;Guo, Steve;Paine, Thomas;Kramer, Arthur F.;Sutton, Bradley P.
旨在评价功能性MRI（fMRI）老化研究中因磁场分布的年龄相关差异（可能影响回波时间和功能对比度）而产生偏倚的可能性。在3T扫描仪上拍摄了31名年轻人（年龄：22 ± 2.9岁）和46名老年人（年龄：66 ± 4.5岁）的磁场图。使用每个参与者的磁场图的空间梯度，模拟回波平面成像（EPI）轨迹。计算有效回波时间，即k空间轨迹最接近k空间中心的时间。这用于检查有效回波时间图中的受试者内和跨年龄组差异。还计算了由这些回波时间偏移引起的血氧水平依赖（BOLD）信号变化百分比，以确定其对fMRI老化研究的影响。对于单个受试者，有效回波时间在整个大脑中的变化高达± 5 ms。不同年龄组的有效回波时间之间的非配对t检验在大脑的几个区域中产生了显著差异（p<0.01）。回波时间的差异仅约为1 ms，但预计不会对BOLD fMRI信号变化百分比（< 4%）产生重要影响。磁化率诱导的磁场梯度会在梯度回波fMRI图像中诱导局部回波时间偏移，这会导致整个大脑的BOLD敏感性发生变化。然而，BOLD信号中与年龄相关的差异对于3T的fMRI研究来说预计很小。
To evaluate the potential for bias in functional MRI (fMRI) aging studies resulting from age-related differences in magnetic field distributions which can impact echo time and functional contrast. Magnetic field maps were taken on 31 younger adults (age: 22 ± 2.9 years) and 46 older adults (age: 66 ± 4.5 years) on a 3 T scanner. Using the spatial gradients of the magnetic field map for each participant, an echo planar imaging (EPI) trajectory was simulated. The effective echo time, time at which the k-space trajectory is the closest to the center of k-space, was calculated. This was used to examine both within-subject and across-age-group differences in the effective echo time maps. The Blood Oxygenation Level Dependent (BOLD) percent signal change resulting from those echo time shifts was also calculated to determine their impact on fMRI aging studies. For a single subject, the effective echo time varied as much as ± 5 ms across the brain. An unpaired t-test between the effective echo time across age group resulted in significant differences in several regions of the brain (p<0.01). The difference in echo time was only approximately 1 ms, however which is not expected to have an important impact on BOLD fMRI percent signal change (< 4%). Susceptibility-induced magnetic field gradients induce local echo time shifts in gradient echo fMRI images, which can cause variable BOLD sensitivity across the brain. However, the age-related differences in BOLD signal are expected to be small for an fMRI study at 3 T.
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DOI：
10.1007/s10334-010-0215-x
发表时间：
2010-06-01
影响因子：
2.3
作者：
Rick, Jochen;Speck, Oliver;Zaitsev, Maxim
通讯作者：
Zaitsev, Maxim
影响因子：
3.3
作者：
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通讯作者：
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影响因子：
2.2
作者：
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通讯作者：
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影响因子：
5.7
作者：
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通讯作者：
Reichenbach, Juergen R.
影响因子：
4.8
作者：
Handwerker, Daniel A.;Gazzaley, Adam;D'Esposito, Mark
通讯作者：
D'Esposito, Mark