Smart Surgical Microscope based on Optical Coherence Domain Reflectometry

Department of Biomedical EngineeringOver 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.ope

Hydrodynamic Characteristics of Pile-Supported Vertical Wall Breakwaters

This paper describes the hydrodynamic characteristics of a pile-supported vertical wall breakwater, the upper part of which is a vertical wall and the lower part consists of an array of vertical piles. For regular waves, using the eigenfunction expansion method, a numerical model has been developed that can compute wave transmission, reflection, and run-up, and wave force acting on the breakwater. For irregular waves, the regular wave model is repeatedly used for each frequency component of the irregular wave spectrum. The wave period is determined according to the frequency of the component wave, while the root-mean-squared wave height is used for all the component waves to compute the energy dissipation between piles. To examine the validity of the developed models, large-scale laboratory experiments have been conducted for pile-supported vertical wall breakwaters with a constant spacing between piles but various drafts of the upper vertical wall. Comparisons between measurement and prediction show that the numerical model adequately reproduces most of the important features of the experimental results for both regular and irregular waves. The pile-supported vertical wall breakwater always gives smaller transmission and larger reflection than a curtain wall breakwater with the same draft as that of the upper wall, or a pile breakwater with the same porosity as that of the lower part, of the pile-supported vertical wall breakwater.author's final versio

Experimental Studies on Wave Interactions of Partially Perforated Wall under Obliquely Incident Waves

This study presents wave height distribution in terms of stem wave evolution phenomena on partially perforated wall structures through three-dimensional laboratory experiments. The plain and partially perforated walls were tested to understand their effects on the stem wave evolution under the monochromatic and random wave cases with the various wave conditions, incident angle (from 10 to 40 degrees), and configurations of front and side walls. The partially perforated wall reduced the relative wave heights more effectively compared to the plain wall structure. Partially perforated walls with side walls showed a better performance in terms of wave height reduction compared to the structure without the side wall. Moreover, the relative wave heights along the wall were relatively small when the relative chamber width is large, within the range of the chamber width in this study. The wave spectra showed a frequency dependency of the wave energy dissipation. In most cases, the existence of side wall is a more important factor than the porosity of the front wall in terms of the wave height reduction even if the partially perforated wall was still effective compared to the plain wall

Numerical Simulation and Large-Scale Physical Modelling of Coastal Sand Dune Erosion

Coastal sand dune system is important in the nearshore environment for sand supply, ecosystem, and hazard mitigation. In this study, a process-based morphological model was performed and the results were compared with large-scale laboratory experimental data. Two-dimensional large-scale laboratory experiments were conducted with 1:6 geometric scale in the large wave flume (104m (L) x 3.7 m (W) x 4.6 m (D)) of the Hinsdale Wave Research Laboratory at Oregon State University (Maddux et al, 2006). Several different wave conditions were used with different water levels in this experiment including pre-storm, storm, and post storm based on random wave time series by using TMA spectrum. The data set included cross-shore Wave heights, fluid velocities, and the profile changes of the beach and dune. The process based model, XBeach (Roelvink et al., 2009) was used to simulate the nearshore hydrodynamics and bed level change during storm wave condition. Several semi-empirical parameters were used in the)(Beach model to predict morphodynamic process (Roelvink et al., 2009) and recently the updated parameters (WTI settings) were suggested based on the results of field observations. The present study ran the)(Beach model by using both default and WTI settings and compared with the results from the experiments. The results showed that the model results with WTI settings showed good agreement with the measured beach profile while the model results with default settings over-predicted the offshore sediment transport and dune erosion. Especially, the wave skewness (facSk) and asymmetry (facAs) gave the highest contribution to predict dune erosion

Observations of wave run-up affected by dune scarp during storm conditions: a two dimensional large-scaled movable bed experiment

Artificial dunes serve as essential nature-based defenses against the increasing threats posed by climate change and rising sea levels along coastal regions. However, these man-made dunes are particularly susceptible to erosion during severe storm events, necessitating careful consideration of their design for effective coastal protection. Among the myriad factors influencing artificial dune design, wave run-up stands out as a paramount concern. Not only is wave run-up crucial in assessing the extent of coastal flooding, but it also plays a significant role in shaping shoreline dynamics. During intense storm events, wave run-up amplification leads to substantial erosion of sand dunes, forming dune scarps that resemble cliffs. To address these challenges, we conducted a series of innovative two-dimensional large-scale laboratory experiments using movable beds. These experiments aimed to provide a quantitative understanding of wave run-up characteristics on dune scarps. Additionally, our study explored the feasibility of using existing empirical formulas to predict the 2% exceedance of wave run-up (referred to as R2%) in such scenarios. Our results revealed a consistent trend in R2% values, irrespective of variations in the surf similarity parameter when wave run-up was influenced by a dune scarp. Notably, our findings recommend the adoption of the Stockdon empirical formula, incorporating beach slope from the still water level to the dune scarp toe, as an effective method for predicting R2% during highly erosive conditions. This approach can significantly enhance the design and functionality of artificial dunes, bolstering their capacity to safeguard coastal areas from the impacts of severe storms and erosion, thus contributing to resilient coastal ecosystems and sustainable coastal management

Lamellar keratoplasty using position-guided surgical needle and M-mode optical coherence tomography

Deep anterior lamellar keratoplasty (DALK) is an emerging surgical technique for the restoration of corneal clarity and vision acuity. The big-bubble technique in DALK surgery is the most essential procedure that includes the air injection through a thin syringe needle to separate the dysfunctional region of the cornea. Even though DALK is a well-known transplant method, it is still challenged to manipulate the needle inside the cornea under the surgical microscope, which varies its surgical yield. Here, we introduce the DALK protocol based on the position-guided needle and M-mode optical coherence tomography (OCT). Depth-resolved 26-gage needle was specially designed, fabricated by the stepwise transitional core fiber, and integrated with the swept source OCT system. Since our device is feasible to provide both the position information inside the cornea as well as air injection, it enables the accurate management of bubble formation during DALK. Our results show that real-time feedback of needle end position was intuitionally visualized and fast enough to adjust the location of the needle. Through our research, we realized that position-guided needle combined with M-mode OCT is a very efficient and promising surgical tool, which also to enhance the accuracy and stability of DALK

Anti-inflammatory function of arctiin by inhibiting COX-2 expression via NF-κB pathways

<p>Abstract</p> <p>Background</p> <p>Arctiin, isolated from <it>Forsythia suspensa </it>has been reported to have anti-inflammatory, anti-oxidant, antibacterial, and antiviral effects <it>in vitro</it>. However, there has been a lack of studies regarding its effects on immunological activity. The aim of this study is to investigate the anti-inflammatory potential and possible mechanisms of arctiin in LPS-induced macrophages.</p> <p>Methods</p> <p>We investigated the mRNA and protein levels of proinflammatory cytokines through RT-PCR and western blot analysis, followed by a FACS analysis for surface molecule changes.</p> <p>Results</p> <p>Arctiin dose dependently decreased the production of NO and proinflammatory cytokines such as IL-1β, IL-6, TNF-α, and PGE₂, and it reduced the gene and protein levels as determined by RT-PCR and western blot analysis, respectively. The expression of co-stimulatory molecules such as B7-1 and B7-2 were also inhibited by arctiin. Furthermore, the activation of the nuclear transcription factor, NF-κB in macrophages was inhibited by arctiin.</p> <p>Conclusion</p> <p>Taken together these results provide evidence of the bioactivity of arctiin in inflammatory diseases and suggest that arctiin may exert anti-inflammatory effect by inhibiting the pro-inflammatory mediators through the inactivation of NF-kB.</p

Tsunami Inundation Modeling in Constructed Environments: A Physical and Numerical Comparison of Free-Surface Elevation, Velocity, and Momentum Flux

A laboratory benchmark test for tsunami inundation through an urban waterfront including free surface elevation, velocity, and specific momentum flux is presented and compared with a numerical model (COULWAVE). The physical model was a 1:50 scale idealization of the town Seaside, Oregon, designed to observe the complex tsunami flow around the macro-roughness such as buildings idealized as impermeable, rectangular blocks. Free surface elevation and velocity time series were measured and analyzed at 31 points along 4 transects. Optical measurements of the leading bore front were used in conjunction with the in-situ velocity and free surface measurements to estimate the time-dependent specific momentum flux at each location. The maximum free surface elevation and specific momentum flux sharply decreased from the shoreline to the landward measurement locations, while the cross-shore velocity slowly decreased linearly. The experimental results show that the maximum specific momentum flux is overestimated by 60 to 260%, if it is calculated using the each maximum values of the free surface elevation and cross-shore velocity. Comparisons show that the numerical model is in good agreement with the physical model at most locations when tuned to a friction factor of 0.005. When the friction factor decreased by a factor of 10 (from 0.01 to 0.001), the average maximum free surface elevation increased 15%, and the average cross-shore velocity and specific momentum flux increased 95 and 208%, respectively. This highlights the importance of comparing velocity in the validation and verification process of numerical models of tsunami inundation.Keywords: COULWAVE, Friction factor, Tsunami, Inundation, Benchmark, Macro-roughnessKeywords: COULWAVE, Friction factor, Tsunami, Inundation, Benchmark, Macro-roughnes