A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland.
Center for Magnetic Resonance in Research, University of Minnesota, Minneapolis, Minnesota, USA.
Magn Reson Med. 2021 Oct;86(4):2137-2145. doi: 10.1002/mrm.28844. Epub 2021 May 18.
Electrical epidural spinal cord stimulation (SCS) is used as a treatment for chronic pain as well as to partially restore motor function after a spinal cord injury. Monitoring the spinal cord activity during SCS with fMRI could provide important and objective measures of integrative responses to treatment. Unfortunately, spinal cord fMRI is severely challenged by motion and susceptibility artifacts induced by the implanted electrode and bones. This pilot study introduces multi-band sweep imaging with Fourier transformation (MB-SWIFT) technique for spinal cord fMRI during SCS in rats. Given the close to zero acquisition delay and high bandwidth in 3 dimensions, MB-SWIFT is demonstrated to be highly tolerant to motion and susceptibility-induced artifacts and thus holds promise for fMRI during SCS.
MB-SWIFT with 0.78 × 0.78 × 1.50 mm spatial resolution and 3-s temporal resolution was used at 9.4 Tesla in rats undergoing epidural SCS at different frequencies. Its performance was compared with spin echo EPI. The origin of the functional contrast was also explored using suppression bands.
MB-SWIFT was tolerant to electrode-induced artifacts and respiratory motion, leading to substantially higher fMRI sensitivity than spin echo fMRI. Clear stimulation frequency-dependent responses to SCS were detected in the rat spinal cord close to the stimulation site. The origin of MB-SWIFT fMRI signals was consistent with dominant inflow effects.
fMRI of the rat spinal cord during SCS can be consistently achieved with MB-SWIFT, thus providing a valuable experimental framework for assessing the effects of SCS on the central nervous system.
电硬膜外脊髓刺激（SCS）被用作慢性疼痛的治疗方法，也可在脊髓损伤后部分恢复运动功能。利用 fMRI 监测 SCS 过程中的脊髓活动，可为治疗的综合反应提供重要的客观测量指标。不幸的是，脊髓 fMRI 受到由植入电极和骨骼引起的运动和敏感性伪影的严重挑战。这项初步研究介绍了用于大鼠 SCS 期间脊髓 fMRI 的多频带扫频成像与傅里叶变换（MB-SWIFT）技术。由于在 3 个维度上接近零采集延迟和高带宽，MB-SWIFT 被证明对运动和敏感性引起的伪影具有高度耐受性，因此有望在 SCS 期间进行 fMRI。
在接受硬膜外 SCS 的大鼠中，在 9.4T 下使用具有 0.78×0.78×1.50mm 空间分辨率和 3s 时间分辨率的 MB-SWIFT，以不同频率进行 SCS。其性能与自旋回波 EPI 进行了比较。还使用抑制带探索了功能对比的起源。
MB-SWIFT 耐受电极引起的伪影和呼吸运动，导致 fMRI 灵敏度大大高于自旋回波 fMRI。在靠近刺激部位的大鼠脊髓中，检测到与 SCS 刺激频率相关的清晰响应。MB-SWIFT fMRI 信号的起源与主导流入效应一致。
可以使用 MB-SWIFT 一致地实现 SCS 期间大鼠脊髓的 fMRI，从而为评估 SCS 对中枢神经系统的影响提供了有价值的实验框架。
