Sampling Rate Effects on Resting State fMRI Metrics
Sampling Rate Effects on Resting State fMRI Metrics
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DOI：
10.3389/fnins.2019.00279
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发表时间：
2019-04-02
影响因子：
4.3
通讯作者：
Korhonen, Vesa O.
中科院分区：
文献类型：
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作者：
Huotari, Niko;Raitamaa, Lauri;Korhonen, Vesa O.
在静息状态功能磁共振成像(RS-fMRI)中使用的低图像采样率可能会导致心肺搏动在甚低频(VLF)大胆信号波动上的混叠，这反映到功能连接性(FC)。在这项研究中，我们考察了采样率对当前使用的RS-fMRI FC指标的影响。用TR0.1 S采样的超快功能磁共振脑成像数据，下采样到不同的亚采样重复次数(Str，范围0.3-3 S)进行比较。回波平面k空间采样(TR2.15 S)和交错层析采集方案也与3D单次激发轨迹在2.2 S应力下进行了比较。量化的连通性指标包括静态的空间、时间和频率域，以及动态分析。时间域方法包括基于SEED的功能连通性分析、区域同质性(REHO)、变异系数和空间域组水平概率独立分量分析(ICA)。在频域分析中，我们考察了低频波动的分数和幅度。通过比较不同STR的VLF(0.01-0.1 Hz)、呼吸(0.12-0.35 Hz)和心功率(0.9-1.3 Hz)的FFT图，对混叠效应进行空间和频谱分析。分析了VLF事件的准周期模式(QPP)对动态FC方法的影响。在不同的采样率下，传统的时间域和空间域分析的结果几乎保持不变。在频域上，混叠主要发生在较高的应力(1-2 S)，心功能混叠超过呼吸功能。甚低频功率图受STR增加的影响最小。与3D采样相比，交错数据重建导致较低的REHO(p<；0.001)。梯度回波平面成像(EPI BOLD)数据产生了更好和更差的指标。在QPP分析中，VLF脉冲检测的重复性随着应力的增加而线性降低。总而言之，常规静息状态指标(如Fc、ICA)不受不同RR(S)的影响。然而，心肺信号表现出最强的混叠在中央脑区的Str1-2 S。搏动性QPP和其他动态分析受益于短的TR扫描。
Low image sampling rates used in resting state functional magnetic resonance imaging (rs-fMRI) may cause aliasing of the cardiorespiratory pulsations over the very low frequency (VLF) BOLD signal fluctuations which reflects to functional connectivity (FC). In this study, we examine the effect of sampling rate on currently used rs-fMRI FC metrics. Ultra-fast fMRI magnetic resonance encephalography (MREG) data, sampled with TR 0.1 s, was downsampled to different subsampled repetition times (sTR, range 0.3-3 s) for comparisons. Echo planar k-space sampling (TR 2.15 s) and interleaved slice collection schemes were also compared against the 3D single shot trajectory at 2.2 s sTR. The quantified connectivity metrics included stationary spatial, time, and frequency domains, as well as dynamic analyses. Time domain methods included analyses of seed-based functional connectivity, regional homogeneity (ReHo), coefficient of variation, and spatial domain group level probabilistic independent component analysis (ICA). In frequency domain analyses, we examined fractional and amplitude of low frequency fluctuations. Aliasing effects were spatially and spectrally analyzed by comparing VLF (0.01-0.1 Hz), respiratory (0.12-0.35 Hz) and cardiac power (0.9-1.3 Hz) FFT maps at different sTRs. Quasi-periodic pattern (QPP) of VLF events were analyzed for effects on dynamic FC methods. The results in conventional time and spatial domain analyses remained virtually unchanged by the different sampling rates. In frequency domain, the aliasing occurred mainly in higher sTR (1-2 s) where cardiac power aliases over respiratory power. The VLF power maps suffered minimally from increasing sTRs. Interleaved data reconstruction induced lower ReHo compared to 3D sampling (p < 0.001). Gradient recalled echo-planar imaging (EPI BOLD) data produced both better and worse metrics. In QPP analyses, the repeatability of the VLF pulse detection becomes linearly reduced with increasing sTR. In conclusion, the conventional resting state metrics (e.g., FC, ICA) were not markedly affected by different TRs (0.1-3 s). However, cardiorespiratory signals showed strongest aliasing in central brain regions in sTR 1-2 s. Pulsatile QPP and other dynamic analyses benefit linearly from short TR scanning.