Reproducibility of brain tissue volumes in longitudinal studies: Effects of changes in signal-to-noise ratio and scanner software
Reproducibility of brain tissue volumes in longitudinal studies: Effects of changes in signal-to-noise ratio and scanner software
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DOI：
10.1016/j.neuroimage.2008.02.003
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发表时间：
2008-06-01
期刊：
影响因子：
5.7
通讯作者：
Wang, Shih-Chang
中科院分区：
文献类型：
--
作者：
Shuter, Borys;Yeh, Ing Berne;Wang, Shih-Chang
基于体素的形态测量(VBM)的使用者必须意识到它的重复性和影响结果的因素。我们从至少两个连续的受试者的3DT1加权研究中评估了VBM软件包(SPM5)在测量灰质(GM)和白质(WM)体积方面的重复性。调查的因素包括研究间隔(ISI：2.2h~124d)、信噪比(SNR：图像平均数量(NA)=1或2)、扫描仪软件版本和空闲时间。通过直接估计组织噪声(SNRTN)和仅含噪声的体素的平均强度(SNRNO)来测量SNR。在扫描仪软件升级后，体素强度增加了5倍，WM平均SNRTN增加了24%(p<；0.001)。连续研究中WM和GM的平均体积变化接近0%(绝对标准差分别为7ml和10ml)。用原始扫描仪软件获得的研究显示，在5名受试者中，由于扫描仪维护导致SNRTN增加，GM的平均体积增加了1.6%。通用汽车的销量随着SNRTN在整个软件升级过程中的增长(高达4.3%；P<；0.01)和NA=2次收购(高达4.1%；P<；0.001)而增加。当ISI不包含软件变更时，GM和WM数量独立于ISI。N6小时的扫描仪空闲时间降低了7%的信噪比(p<；0.001)。仅2名受试者SPM5未包括可见的外周GM。在整个软件升级过程中，SNRTN的增幅大于SNRNO的增幅。结果表明，信噪比的变化对SPM5来源的GM体积有显著影响。SNR可能会受到扫描仪软件升级和硬件条件的影响，应该在脑体积研究中常规评估。(C)2008 Elsevier Inc.保留所有权利。
It is imperative that users of voxel-based morphometry (VBM) be aware of its reproducibility and the factors which influence results. We assessed the reproducibility of a VBM software package (SPM5) in measuring gray matter (GM) and white matter (WM) volumes from at least two consecutive 3D T1-weighted studies in 64 subjects. Factors investigated were the inter-study interval (ISI: 2.2 h to 124 days), signal-to-noise ratio (SNR: number of image averages (NA)= 1 or 2), scanner software version and idle time. SNR was measured by direct estimation of tissue noise (SNRTN) and mean intensity in noise-only voxels (SNRNO). After the scanner software upgrade, voxel intensity increased 5-fold and WM mean SNRTN by 24% (p < 0.001). Mean WM and GM volume changes in consecutive studies were near 0% (absolute SD of 7 ml and 10 ml respectively). Studies acquired with original scanner software showed a small (1.6%) mean GM volume increase attributed to SNRTN increases in five subjects due to scanner maintenance. GM volumes increased with SNRTN across the software upgrade (up to 4.3%; p < 0.01) and NA = 2 acquisitions (up to 4.1%; p < 0.001). GM and WM volumes were independent of ISI when ISI did not encompass the software change. Scanner idle times of N6 h decreased SNR by 7% (p < 0.001). SPM5 failed to include visible peripheral GM in only 2 subjects. SNRTN increases were greater than SNRNO increases across the software upgrade. It was concluded that SNR changes significantly influence SPM5-derived GM volumes. SNR may be influenced by scanner software upgrades and hardware condition and should be routinely assessed in studies of brain volume. (c) 2008 Elsevier Inc. All rights reserved.