Investigation of spatial resolution, partial volume effects and smoothing in functional MRI using artificial 3D time series
Investigation of spatial resolution, partial volume effects and smoothing in functional MRI using artificial 3D time series
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DOI：
10.1016/j.neuroimage.2008.02.015
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发表时间：
2008-06
期刊：
影响因子：
5.7
通讯作者：
A. Weibull;H. Gustavsson;S. Mattsson;J. Svensson
中科院分区：
文献类型：
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作者：
A. Weibull;H. Gustavsson;S. Mattsson;J. Svensson
本文研究了功能磁共振成像(FMRI)中时间信噪比(TSNR)和部分体积效应(PVE)之间的平衡，并研究了空间分辨率和平滑的选择对成像结果的影响。在功能磁共振成像中，由于生理时程是被监测的，因此tSNR比图像SNR更重要。当生理波动主导噪声时，通过增加体素体积来提高SNR可能是微不足道的。此外，在较大的体素体积时，PVE更加明显，从而导致整体性能下降。基于高分辨率解剖数据的人工fMRI时间序列被用来以受控的方式模拟大胆激活。随后，性能被量化，作为结果激活与模拟激活匹配程度的衡量标准。性能高度依赖于空间分辨率。在高对比度噪声比(CNR)下，最佳体素体积较小，即在23mm3范围内。研究还表明，在这种情况下使用更大的体素体积可能会潜在地抵消CNR的好处。最优平滑核宽度取决于信噪比，信噪比越差，最优平滑核宽度越大。在CNR>；1，很少的平滑或没有平滑被证明是有利的。人工时间序列的使用为定量研究部分体积和平滑效应在单受试者功能磁共振成像中的作用提供了机会。结果表明，选择合适的空间分辨率和平滑核宽度对fMRI的性能非常重要。
This work addresses the balance between temporal signal-to-noise ratio (tSNR) and partial volume effects (PVE) in functional magnetic resonance imaging (fMRI) and investigates the impact of the choice of spatial resolution and smoothing. In fMRI, since physiological time courses are monitored, tSNR is of greater importance than image SNR. Improving SNR by an increase in voxel volume may be of negligible benefit when physiological fluctuations dominate the noise. Furthermore, at large voxel volumes, PVE are more pronounced, leading to an overall loss in performance. Artificial fMRI time series, based on high-resolution anatomical data, were used to simulate BOLD activation in a controlled manner. The performance was subsequently quantified as a measure of how well the resulted activation matched the simulated activation. The performance was highly dependent on the spatial resolution. At high contrast-to-noise ratio (CNR), the optimal voxel volume was small, i.e. in the region of 23mm3. It was also shown that using a substantially larger voxel volume in this case could potentially negate the CNR benefits. The optimal smoothing kernel width was dependent on the CNR, being larger at poor CNR. At CNR >1, little or no smoothing proved advantageous. The use of artificial time series gave an opportunity to quantitatively investigate the effects of partial volume and smoothing in single subject fMRI. It was shown that a proper choice of spatial resolution and smoothing kernel width is important for fMRI performance.