Electrophysiological and Anatomical Correlates of Spinal Cord Optical Coherence Tomography

Despite the continuous improvement in medical imaging technology, visualizing the spinal cord poses severe problems due to structural or incidental causes, such as small access space and motion artifacts. In addition, positional guidance on the spinal cord is not commonly available during surgery, with the exception of neuronavigation techniques based on static pre-surgical data and of radiation-based methods, such as fluoroscopy. A fast, bedside, intraoperative real-time imaging, particularly necessary during the positioning of endoscopic probes or tools, is an unsolved issue. The objective of our work, performed on experimental rats, is to demonstrate potential intraoperative spinal cord imaging and probe guidance by optical coherence tomography (OCT). Concurrently, we aimed to demonstrate that the electromagnetic OCT irradiation exerted no particular effect at the neuronal and synaptic levels. OCT is a user-friendly, low-cost and endoscopy-compatible photonics-based imaging technique. In particular, by using a Fourier-domain OCT imager, operating at 850 nm wavelength and scanning transversally with respect to the spinal cord, we have been able to: 1) accurately image tissue structures in an animal model (muscle, spine bone, cerebro-spinal fluid, dura mater and spinal cord), and 2) identify the position of a recording microelectrode approaching and inserting into the cord tissue 3) check that the infrared radiation has no actual effect on the electrophysiological activity of spinal neurons. The technique, potentially extendable to full three-dimensional image reconstruction, shows prospective further application not only in endoscopic intraoperative analyses and for probe insertion guidance, but also in emergency and adverse situations (e.g. after trauma) for damage recognition, diagnosis and fast image-guided intervention.

尽管医学成像技术持续迭代升级，但受结构特性或偶然干扰因素（如操作空间狭小、运动伪影）影响，脊髓可视化仍面临严峻挑战。此外，术中脊髓位置引导手段较为稀缺，目前仅有的方案包括基于术前静态数据的神经导航（neuronavigation）技术，以及荧光透视（fluoroscopy）等辐射类成像方法。快速、可床边部署的术中实时成像技术仍是尚未解决的技术难题，尤其在内窥镜探针或手术器械定位环节不可或缺。
本研究以实验大鼠为研究对象，旨在验证光学相干断层成像（optical coherence tomography, OCT）用于术中脊髓成像与探针引导的可行性；同时验证电磁式OCT辐照不会对神经元及突触水平产生异常影响。OCT是一种操作简便、成本低廉且兼容内窥镜的光子学成像技术。
具体而言，本研究采用工作波长为850 nm、沿脊髓横向扫描的傅里叶域OCT成像系统，达成了以下目标：1）在动物模型中精准成像肌肉、脊柱骨、脑脊液、硬脑膜及脊髓等组织结构；2）准确定位逼近并插入脊髓组织的记录用微电极位置；3）确认红外辐射不会对脊髓神经元的电生理活动产生实质影响。
该技术有望拓展至全三维图像重建领域，其潜在应用场景不仅包括内窥镜术中分析与探针插入引导，还可用于创伤后等紧急及特殊场景中的损伤识别、诊断与快速影像引导介入操作。