Optimal repetition time reduction for single subject event-related functional magnetic resonance imaging.
Optimal repetition time reduction for single subject event-related functional magnetic resonance imaging.
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DOI：
10.1002/mrm.27498
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发表时间：
2019-03
影响因子：
3.3
通讯作者：
Carmichael DW
中科院分区：
文献类型：
--
作者：
McDowell AR;Carmichael DW
短TR越来越多地用于功能磁共振成像的快速序列，如同时多层激励变得可用。这些都与明显的敏感性改善，虽然更大的时间自相关在较短的TR可以膨胀的敏感性测量，导致不确定性的最佳方法。在志愿者（n = 10）中，针对事件相关设计（视觉刺激），在单个受试者水平评估最佳TR，4个TR值（412 - 2550 ms）下显示4个频率。获得每个个体中定位于视觉皮层的T值，并通过在不同阈值下对预期任务活动区域内外的体素进行计数来进行受试者工作特征（ROC）分析。使用4种不同的自回归（AR）模型重复该分析; SPM AR（1）和SPM AR（快速）用于全局估计自相关性，fMRIstat AR（1）和AR（5）用于局部估计。如视觉皮层和ROC分析中较高的T值所示，使用2或3的适度多波段因子并将TR降低至1000 ± 200 ms具有更高的灵敏度和特异性。在这些TR，ROC分析表明，局部AR模型拟合提高了性能，而高阶AR模型是不必要的。适度的TR降低（至1000 ± 200 ms）最佳地改善了事件相关fMRI性能，与设计频率无关。自回归模型与当地，而不是全球的拟合表现更好，而低阶自回归模型是足够的最佳TR。
Short TRs are increasingly used for fMRI as fast sequences such as simultaneous multislice excitation become available. These have been associated with apparent sensitivity improvements, although greater temporal autocorrelation at shorter TRs can inflate sensitivity measurements leading to uncertainty regarding the optimal approach. In volunteers (n = 10), the optimal TR was assessed at the single subject level for event‐related designs (visual stimulation) with 4 frequencies of presentation at 4 TR values (412‐2550 ms). T‐values in the visual cortex localized in each individual were obtained and receiver operating characteristics (ROC) analysis was performed by counting voxels within and outside expected task active regions at different thresholds. This analysis was repeated using 4 different autoregressive (AR) models; SPM AR(1) and SPM AR(fast) which globally estimate autocorrelation, and fMRIstat AR(1) and AR(5) that use a local estimate. The use of modest multiband factors of 2 or 3 with a reduction in TR to 1000 ± 200 ms had greater sensitivity and specificity as shown by higher T‐values in visual cortex and ROC analysis. At these TRs, the ROC analysis demonstrated that a local AR model fit improved performance while high order AR models were unnecessary. Modest TR reductions (to 1000 ± 200 ms) optimally improved event‐related fMRI performance independent of design frequency. Autoregressive models with a local as opposed to global fit performed better, while low order autoregressive models were sufficient at the optimal TR.
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影响因子：
5.7
作者：
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通讯作者：
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通讯作者：
Carmichael DW