Optical Coherence Tomography (OCT) is a promising non-invasive in vivo imaging technology visualizing the 3-dimensional microanatomy of retina, skin and vocal fold. In the field of laryngology, OCT probes installed in an existing laryngoscope have been widely studied. However, there are still a number of critical issues to be resolved to develop a successful phonomicrosurgical OCT system including high-resolution, long working distance (≥400 mm) and rapid 3D image reconstruction, etc. Here we introduce a long working distance OCT with 35µm lateral and 13µm axial resolutions. To the best of our knowledge, this is the first OCT with up to 450mm of working distance as well as µm-level resolutions to identify subepithelial tissue structure of vocal fold. The main purpose of this study is to investigate the feasibility and efficacy of the system in ex-vivo microstructure imaging of vocal fold, especially the Reinke’s space. We tested the imaging capability of the system with the freshly excised canine eyeball and larynx samples before proceeding the study with fresh human laryngectomized specimens. The acquired OCT images were then compared with the corresponding H&E stained histological sections. This correlation study allowed the identiﬁcation of the epithelial layer, lamina propria, subepithelial glandular structures and vessels of the canine and human specimens from both the OCT and the microscope images ensuring solid correspondence between two different types of visual tissue assessment. This OCT system is developed to directly confirm the lesions during phonomicrosurgeries enabling the clinicians to reduce the number of intraoperative biopsies.
The biggest clinical benefit of OCT as a diagnostic tool for retinal disorders is that it enables the discrimination of subtle pathologic changes in vivo. Though a large number of researches have been done to expand its applications, few of them proved sufficient utility in clinical settings. In laryngology, an OCT system attachable to and working in tandem with an operating microscope may provide solid clinical benefits. Nevertheless, such a system has not been introduced yet, while it is more common to find an OCT system with a hand-held type probe. Hence, we developed a phonomicrosurgical OCT with a long working distance and attachable to an existing operating microscope. The OCT also has a dichroic mirror which splits the coherent IR laser and visual projection to enable dual imaging. We evaluated the efficacy of the system in evaluating subepithelial tissue structure, especially in the Reinke’s space of vocal fold. We tested its imaging capability with excised canine larynx and eyeball. Then, we assessed the surgical margin with the OCT images after treating a live canine larynx with a CO2 laser under general anesthesia. In addition, we compared the images with corresponding histopathologic findings to confirm the diagnostic feasibility. The OCT and histopathologic images showed a significant correlation to identify the epithelial layer, lamina propria, subepithelial glandular structures and vessels from the OCT images. This is the first OCT system attachable to an operating microscope which may provide a promising alternative to frozen biopsies for intraoperative laryngeal cancer margin assessment.