Center for Functional MRI, Department of Radiology, University of California, San Diego, La Jolla, California 92037, USA.
Magn Reson Med. 2012 May;67(5):1412-8. doi: 10.1002/mrm.23105. Epub 2011 Aug 8.
Direct measurement of neural currents by means of MRI can potentially open a high temporal resolution (10-100 ms) window applicable for monitoring dynamics of neuronal activity without loss of the high spatial resolution afforded by MRI. Previously, we have shown that the alternating balanced steady state imaging affords high sensitivity to weak periodic currents owing to its amplification of periodic spin phase perturbations. This technique, however, requires precise synchronization of such perturbations to the radiofrequency pulses. Herein, we extend alternating balanced steady state imaging to multiple balanced alternating steady states for estimation of neural current waveforms. Simulations and phantom experiments show that the off-resonance profile of the multiple alternating steady state signal carries information about the frequency content of driving waveforms. In addition, the method is less sensitive than alternating balanced steady state to precise waveform timing relative to radiofrequency pulses. Thus, multiple alternating steady state technique is potentially applicable to MR imaging of the waveforms of periodic neuronal activity.
通过 MRI 直接测量神经电流有可能开辟一个高时间分辨率（10-100ms）的窗口，适用于监测神经元活动的动态，而不会损失 MRI 提供的高空间分辨率。以前，我们已经表明，交替平衡稳态成像由于其对周期性自旋相位扰动的放大作用，对弱周期性电流具有高灵敏度。然而，该技术要求将这种扰动精确地与射频脉冲同步。在这里，我们将交替平衡稳态成像扩展到多个平衡交替稳态，以估计神经电流波形。模拟和体模实验表明，多个平衡稳态信号的离频轮廓携带有关驱动波形频率内容的信息。此外，与射频脉冲相比，该方法对精确的波形定时的敏感性低于交替平衡稳态。因此，多稳态交替技术有可能适用于周期性神经元活动的磁共振成像。
