MRI of weak periodic currents using balanced Steady State Free Precession

使用平衡稳态自由进动的弱周期电流 MRI

• 批准号: 7644307
• 负责人: GIEDRIUS T BURACAS
• 金额: $ 19.31万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN DIEGO
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7644307
• 关键词: Achievement; Acoustic Stimulation; Address; Affect; Animals; Arteriogram; Blood Vessels; Brain; Brain imaging; Caffeine; Carbon Dioxide; Cardiac; Cerebrovascular Circulation; Cerebrum; Characteristics; Computer Simulation; Coupling; Data; Detection; Electromagnetics; Equilibrium; Financial compensation; Frequencies; Goals; Head; Heating; Human; Image; Magnetic Resonance Imaging; Magnetoencephalography; Measures; Metabolic; Methods; Motion; Neuromodulator; Neurons; Noise; Pattern; Phase; Physiologic pulse; Physiological; Problem Solving; Protocols documentation; Radio; Rattus; Reporting; Research; Resolution; Respiration; Scanning; Signal Transduction; Source; Spin Labels; Stimulus; Techniques; Testing; Time; Variant; Vibrissae; Visual; base; blood oxygen level dependent; blood oxygenation level dependent response; imaging modality; in vivo; magnetic field; public health relevance; relating to nervous system; research study; respiratory; response; theories

DESCRIPTION (provided by applicant): Existing functional brain MR imaging methods such as blood oxygenation level dependent (BOLD) imaging are based on vascular and metabolic responses to variations in underlying neuronal activity and thus reflect the latter only indirectly. It has been proposed (e.g. Bodurka & Bandettini, 2002) that magnetic field perturbations caused by neuronal currents in the brain in principle ought to be detectable by means of MRI. Several research groups have demonstrated the feasibility of this idea in theory, electric current phantoms and in vivo. However, relatively low signal-to-noise ratio achieved to date renders existing methods impractical. Balanced Steady State Free Precession (bSSFP, also known as TrueFISP, FIESTA) pulse sequence is unique in that it can afford the highest known SNR per unit time and thus application of bSSFP for functional neural current imaging can potentially solve the problem of low SNR. Recent studies suggest that certain SSFP sequences might be exquisitely sensitive to minute periodic perturbations of the spin phase. Thus, periodic currents locked to RF excitation pulse result in an alternating balanced steady state (ABSS) that can effectively amplify the phase offset induced by currents. Our theoretical calculations and the data acquired with bSSFP at 3T using a current phantom indicates SNR of the signal induced by periodic currents that is substantially superior to that achieved previously using standard gradient and spin echo imaging (Buracas et al., 2007). We propose to develop optimized alternating steady-state imaging protocols for imaging of periodic electric currents. First, we will optimize, analytically, in computer simulations, and current phantom experiments the sensitivity of the ABSS method to weak periodic currents and address the impact of various sources of noise on the ABSS signal. Next, we will apply this method to imaging neuronal currents in vivo (using rat whisker stimulation and human audiovisual stimulation paradigms). We will implement noise compensation for magnetic field fluctuation due to respiration and scanner drift and motion compensation. In conclusion, the current proposal will address the possibility to measure electromagnetic correlates of cerebral neuronal activity by means of ABSS and will address critical sources of noise. Accomplishment of the proposed aims has a potential of introducing a new imaging modality for functional brain imaging - high resolution MRI-based magnetoencephalography. PUBLIC HEALTH RELEVANCE: Established functional brain MR imaging methods are susceptible to factors influencing neurovascular coupling. It has been recently proposed and demonstrated that MRI can be used for imaging neuronal currents directly, but existing methods are impractical due to their low SNR. The proposed research will develop ultra- sensitive MRI methods for imaging neuronal currents using balanced Steady State Free Precession pulse sequences that possess best known SNR efficiency.

描述（由申请人提供）：现有的功能性脑MR成像方法，例如血液氧合水平依赖（BOLD）成像基于对潜在神经元活性变异的血管和代谢反应，因此仅间接地反映了后者。已经提出（例如Bodurka＆Bandettini，2002年），应该通过MRI来检测到由大脑中神经元电流引起的磁场扰动。几个研究小组在理论上，电流幻象和体内都证明了这一想法的可行性。但是，相对较低的信噪比与迄今为止达到的现有方法是不切实际的。平衡的无稳态进动（BSSFP，也称为TrueFISP，Fiesta）脉冲序列是独一无二的，因为它可以负担得起每单位时间最高的SNR，因此BSSFP在功能性神经电流成像中的应用可能会解决低SNR的问题。最近的研究表明，某些SSFP序列可能对自旋阶段的微小周期性扰动非常敏感。因此，锁定到RF激发脉冲的周期电流导致交替平衡的稳态（ABS），可以有效地扩大电流引起的相位偏移。我们的理论计算以及使用当前幻影在3T处用BSSFP获取的数据表明，周期电流引起的信号的SNR基本上优于先前使用标准梯度和自旋回声成像获得的信号（Buracas等，2007）。我们建议开发优化的交替稳态成像协议，以进行周期性电流的成像。首先，我们将在计算机模拟和当前的幻影实验中对ABS进行弱周期性电流的敏感性进行优化，并解决噪声源对ABS信号的影响。接下来，我们将将这种方法应用于体内神经元电流（使用大鼠晶须刺激和人类视听刺激范式）。我们将由于呼吸和扫描仪漂移和运动补偿而实施磁场波动的噪声补偿。总之，当前的建议将解决通过ABS通过ABS测量脑神经元活性的电磁相关的可能性，并将解决关键的噪声来源。提出的目标的完成具有为功能性脑成像引入新的成像方式 - 高分辨率基于MRI的磁脑摄影。公共卫生相关性：已建立的功能性脑MR成像方法易受影响神经血管耦合的因素。最近已经提出并证明了MRI可直接用于成像神经元电流，但是由于其低SNR，现有方法是不切实际的。拟议的研究将开发使用具有均衡的稳态无动脉冲序列的超敏感MRI方法，以对神经元电流进行成像，这些脉冲具有最著名的SNR效率。

项目成果

On multiple alternating steady states induced by periodic spin phase perturbation waveforms.

关于由周期性自旋相位扰动波形引起的多个交替稳态。

• DOI: 10.1002/mrm.23105
• 发表时间: 2012
• 期刊: Magnetic resonance in medicine
• 影响因子: 3.3
• 作者: Buračas,GiedriusT;Jung,Youngkyoo;Lee,Jongho;Buxton,RichardB;Wong,EricC;Liu,ThomasT
• 通讯作者: Liu,ThomasT