Smart Surgical Microscope based on Optical Coherence Domain Reflectometry

Abstract

Over the several decades, there have been clinical needs that requires advanced technologies in medicine. Optical coherence tomography (OCT), one of the newly emerged medical imaging devices, provides non-invasive cross-sectional images in high resolution which is mainly used in ophthalmology. However, due to the limited penetration depth of 1-2 mm in bio-samples, there is a limit to be widely used. In order to easily integrate with existing medical tools and be convenient to users, it is necessary that the sample unit of OCT should be compact and simple. In this study, we developed high-speed swept-source OCT (SS-OCT) for advanced screening of otolaryngology. Synchronized signal sampling with a high-speed digitizer using a clock signal from a swept laser source, its trigger signal is also used to synchronize with the movement of the scanning mirror. The SS-OCT system can reliably provide high-throughput images, and two-axis scanning of galvano mirrors enables real-time acquisition of 3D data. Graphic processing unit (GPU) can performs high-speed data processing through parallel programming, and can also implement perspective projection 3D OCT visualization with optimal ray casting techniques. In the Clinical Study of Otolaryngology, OCT was applied to identify the microscopic extrathyroidal extension (mETE) of papillary thyroid cancer (PTC). As a result to detect the mETE of around 60% in conventional ultrasonography, it could be improved to 84.1% accuracy in our study. The detection ratio of the mETE was calculated by the pathologist analyzing the histologic image. In chapter 3, we present a novel study using combined OCT system integrated with a conventional surgical microscope. In the current set-up of surgical microscope, only two-dimensional microscopic images through the eyepiece view are provided to the surgeon. Thus, image-guided surgery, which provides real-time image information of the tissues or the organs, has been developed as an advanced surgical technique. This study illustrate newly designed optical set-up of smart surgical microscope that combined sample arm of the OCT with an existing microscope. Specifically, we used a beam projector to overlay OCT images on existing eyepiece views, and demonstrated augmented reality images. In chapter 4, in order to develop novel microsurgical instruments, optical coherence domain reflectometry (OCDR) was applied. Introduces smart surgical forceps using OCDR as a sensor that provides high-speed, high-resolution distance information in the tissue. To attach the sensor to the forceps, the lensed fiber which is a small and high sensitivity sensor was fabricated and the results are shown to be less affected by the tilt angle. In addition, the piezo actuator compensates the hand tremor, resulting in a reduction in the human hand tremor of 5 to 15 Hz. Finally, M-mode OCT needle is proposed for microsurgery guidance in ophthalmic surgery. Stepwise transitional core (STC) fiber was applied as a sensor to measure information within the tissue and attached to a 26 gauge needle. It shows the modified OCT system and the position-guided needle design of the sample stage and shows the algorithm flowchart of M-mode OCT imaging software. The developed M-mode OCT needle has been applied to animal studies using rabbit eyes and demonstrates the big-bubble deep anterior lamellar keratoplasty (DALK) surgery for corneal transplantation. Through this study, we propose a novel microsurgical instrument for lamellar keratoplasty and evaluate its feasibility with conventional regular OCT system images. In conclusion, for fundamental study required new augmented reality guided surgery with smart surgical microscope, it is expected that OCT combined with surgical microscope can be widely used. We demonstrated a novel microsurgical instrument to share with light source and the various optical components. Acquired information throughout our integrated system would be a key method to meet a wide range of different clinical needs in the real world.