Now you see it, now you don't: optimal parameters for interslice stimulation in concurrent TMS-fMRI
Now you see it, now you don't: optimal parameters for interslice stimulation in concurrent TMS-fMRI
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现在您看到了，现在您没有：并发 TMS-fMRI 中层间刺激的最佳参数
DOI：
10.1101/2021.05.28.446111
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Scrivener C
中科院分区：
文献类型：
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作者：
Scrivener C
经颅磁刺激（TMS）与功能性磁共振成像（fMRI）的强大结合为大脑活动和行为之间的因果关系提供了罕见的见解。尽管最近流行起来，TMS-fMRI在技术上仍然具有挑战性。在这里，我们研究了在功能磁共振切片之间的短间隙应用经颅磁刺激的可行性，以避免在功能磁共振数据中产生伪影。我们量化了在切片开始前100ms到后100ms时间点呈现的TMS脉冲的信号丢失和时间信噪比（tSNR）的变化。使用MagVenture的mr兼容TMS线圈，每体积最多可传送3个脉冲。我们在西门子3T Prisma-fit扫描仪上使用了一个球形幻影，两个7通道tms专用表面线圈，以及一个多波段（MB）序列（因子=2），夹层间隙为100ms和40ms。为了进行比较，我们使用更标准的单通道TxRx（鸟笼）线圈重复了参数子集，并设置了人类参与者和表面线圈。我们发现，即使在100%的刺激器输出，从切片读出开始至少- 40ms/+50ms施加的脉冲也可以避免产生伪影。这是所有三个设置的情况。因此，使用标准的EPI序列（片采集时间：62.5ms，片间隙：40ms），可以实现频率高达~10 Hz的片间协议。更快的刺激频率需要更短的切片采集时间，例如使用面内加速。夹层TMS- fmri协议提供了一个有前途的途径，以保持灵活的时间刺激传递，而不会产生TMS伪影。
The powerful combination of transcranial magnetic stimulation (TMS) concurrent with functional magnetic resonance imaging (fMRI) provides rare insights into the causal relationships between brain activity and behaviour. Despite a recent resurgence in popularity, TMS-fMRI remains technically challenging. Here we examined the feasibility of applying TMS during short gaps between fMRI slices to avoid incurring artefacts in the fMRI data. We quantified signal dropout and changes in temporal signal-to-noise ratio (tSNR) for TMS pulses presented at timepoints from 100ms before to 100ms after slice onset. Up to 3 pulses were delivered per volume using MagVenture’s MR-compatible TMS coil. We used a spherical phantom, two 7-channel TMS-dedicated surface coils, and a multiband (MB) sequence (factor=2) with interslice gaps of 100ms and 40ms, on a Siemens 3T Prisma-fit scanner. For comparison we repeated a subset of parameters with a more standard single-channel TxRx (birdcage) coil, and with a human participant and surface coil set up. We found that, even at 100% stimulator output, pulses applied at least - 40ms/+50ms from the onset of slice readout avoid incurring artifacts. This was the case for all three setups. Thus, an interslice protocol can be achieved with a frequency of up to ~10 Hz, using a standard EPI sequence (slice acquisition time: 62.5ms, interslice gap: 40ms). Faster stimulation frequencies would require shorter slice acquisition times, for example using in-plane acceleration. Interslice TMS-fMRI protocols provide a promising avenue for retaining flexible timing of stimulus delivery without incurring TMS artifacts.