基于切片的动态匀场在脑和脊髓 fMRI 中的应用。
Dynamic per slice shimming for simultaneous brain and spinal cord fMRI.
机构信息
Department of Bioengineering, Stanford University, Stanford, California.
Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Stanford, California.
出版信息
Magn Reson Med. 2019 Feb;81(2):825-838. doi: 10.1002/mrm.27388. Epub 2018 Oct 4.
PURPOSE
Simultaneous brain and spinal cord functional MRI is emerging as a new tool to study the central nervous system but is challenging. Poor B homogeneity and small size of the spinal cord are principal obstacles to this nascent technology. Here we extend a dynamic shimming approach, first posed by Finsterbusch, by shimming per slice for both the brain and spinal cord.
METHODS
We shim dynamically by a simple and fast optimization of linear field gradients and frequency offset separately for each slice in order to minimize off-resonance for both the brain and spinal cord. Simultaneous acquisition of brain and spinal cord fMRI is achieved with high spatial resolution in the spinal cord by means of an echo-planar RF pulse for reduced FOV. Brain slice acquisition is full FOV.
RESULTS
T2*-weighted images of brain and spinal cord are acquired with high clarity and minimal observable image artifacts. Fist-clenching fMRI experiments reveal task-consistent activation in motor cortices, cerebellum, and C6-T1 spinal segments.
CONCLUSIONS
High quality functional results are obtained for a sensory-motor task. Consistent activation in both the brain and spinal cord is observed at individual levels, not only at group level. Because reduced FOV excitation is applicable to any spinal cord section, future continuation of these methods holds great potential.
目的
同时进行脑和脊髓的功能磁共振成像作为研究中枢神经系统的新工具正在兴起，但具有挑战性。较差的 B 同质性和脊髓较小的尺寸是这项新兴技术的主要障碍。在这里，我们扩展了 Finsterbusch 首次提出的动态匀场方法，对大脑和脊髓的每个切片进行逐片匀场。
方法
我们通过单独对每个切片的线性磁场梯度和频率偏移进行简单而快速的优化来动态匀场，以最小化脑和脊髓的离共振。通过用于减小视场的回波平面 RF 脉冲，实现了高空间分辨率的脊髓和脑的同时 fMRI 采集。大脑切片采集是全视场。
结果
获得了具有高清晰度和最小可观察图像伪影的脑和脊髓 T2*-加权图像。握拳 fMRI 实验揭示了运动皮质、小脑和 C6-T1 脊髓节段的一致激活。
结论
对于感觉运动任务，获得了高质量的功能结果。在个体水平上观察到大脑和脊髓的一致激活，而不仅在群体水平上。由于减小的视场激发适用于任何脊髓节段，因此这些方法的进一步发展具有很大的潜力。
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