High-resolution in vivo imaging of peripheral nerves using optical coherence tomography: a feasibility study

Abstract

OBJECTIVEBecause of their complex topography, long courses, and small diameters, peripheral nerves are challenging structures for radiological diagnostics. However, imaging techniques in the area of peripheral nerve diseases have undergone unexpected development in recent decades. They include MRI and high-resolution sonography (HRS). Yet none of those imaging techniques reaches a resolution comparable to that of histological sections. Fascicles are the smallest discernable structure. Optical coherence tomography (OCT) is the first imaging technique that is able to depict a nerve’s ultrastructure at micrometer resolution. In the current study, the authors present an in vivo assessment of human peripheral nerves using OCT.METHODSOCT measurement was performed in 34 patients with different peripheral nerve pathologies, i.e., nerve compression syndromes. The nerves were examined during surgery after their exposure. Only the sural nerve was twice examined ex vivo. The Thorlabs OCT systems Callisto and Ganymede were used. For intraoperative use, a hand probe was covered with a sterile foil. Different postprocessing imaging techniques were applied and evaluated. In order to highlight certain structures, five texture parameters based on gray-level co-occurrence matrices were calculated according to Haralick.RESULTSThe intraoperative use of OCT is easy and intuitive. Image artifacts are mainly caused by motion and the sterile foil. If the artifacts are kept at a low level, the hyporeflecting bundles of nerve fascicles and their inner parts can be displayed. In the Haralick evaluation, the second angular moment is most suitable to depict the connective tissue.CONCLUSIONSOCT is a new imaging technique that has shown promise in peripheral nerve surgery for particular questions. Its resolution exceeds that provided by recent radiological possibilities such as MRI and HRS. Since its field of view is relatively small, faster acquisition times would be highly desirable and have already been demonstrated by other groups. Currently, the method resembles an optical biopsy and can be a supplement to intraoperative sonography, giving high-resolution insight into a suspect area that has been located by sonography in advance.

Theranostic applications of optical coherence tomography in neurosurgery?

“…Intraoperative handheld OCT during peripheral nerve surgery could delineate single bundles of nerve fascicles [ 6 ]. Image quality was influenced by motion artifacts and wrapping of the imaging probe with sterile foil.…”

In Vivo Cellular‐Level 3D Imaging of Peripheral Nerves Using a Dual‐Focusing Technique for Intra‐Neural Interface Implantation

“…Recent attempts to visualize the human peripheral nerve using commercially available OCT have been unsuccessful in clearly distinguishing myelinated axons because of the motion artifacts, which are generated due to the slow imaging speed. [ 13 , 29 ] To increase the imaging speed, several techniques have been developed, such as stretched‐pulse mode‐locking based circular‐ranging OCT, [ 30 , 32 ] Fourier‐domain mode‐locking laser technique, [ 33 , 34 , 35 ] and space‐division multiplexing OCT. [ 36 , 37 , 38 ] These techniques enable A‐line rate of several MHz to near 1 MHz. However, the spectral ranges of the laser sources, with an axial resolution of less than 5 µm, are unsuitable for ultrahigh‐resolution imaging.…”

Fluorescence labeling of a NaV1.7-targeted peptide for near-infrared nerve visualization

“…Oncologic surgery, in particular, poses a risk of nerve injury as anatomy is often distorted by the disease [10][11][12][13][14][15][16][17]. Tools for pre and perioperative nerve enhancement exist [18][19][20] and fluorescent nerve imaging agents, as well as multimodal optical imaging techniques, are raising interest for intraoperative applications [21][22][23][24][25][26][27][28][29][30][31].…”