Real-time intraoperative 4D full-range FD-OCT based on the dual graphics processing units architecture for microsurgery guidance

Real-time 4D full-range complex-conjugate-free Fourier-domain optical coherence tomography (FD-OCT) is implemented using a dual graphics processing units (dual-GPUs) architecture. One GPU is dedicated to the FD-OCT data processing while the second one is used for the volume rendering and display. GPU accelerated non-uniform fast Fourier transform (NUFFT) is also implemented to suppress the side lobes of the point spread function to improve the image quality. Using a 128,000 A-scan/second OCT spectrometer, we obtained 5 volumes/second real-time full-range 3D OCT imaging. A complete micro-manipulation of a phantom using a microsurgical tool is monitored by multiple volume renderings of the same 3D date set with different view angles. Compared to the conventional surgical microscope, this technology would provide the surgeons a more comprehensive spatial view of the microsurgical site and could serve as an effective intraoperative guidance tool

Development and preliminary results of bimanual smart micro-surgical system using a ball-lens coupled OCT distance sensor

Bimanual surgery enhances surgical effectiveness and is required to successfully accomplish complex microsurgical tasks. The essential advantage is the ability to simultaneously grasp tissue with one hand to provide counter traction or exposure, while dissecting with the other. Towards enhancing the precision and safety of bimanual microsurgery we present a bimanual SMART micro-surgical system for a preliminary ex-vivo study. To the best of our knowledge, this is the first demonstration of a handheld bimanual microsurgical system. The essential components include a ball-lens coupled common-path swept source optical coherence tomography sensor. This system effectively suppresses asynchronous hand tremor using two PZT motors in feedback control loop and efficiently assists ambidextrous tasks. It allows precise bimanual dissection of biological tissues with a reduction in operating time as compared to the same tasks performed with conventional onehanded approaches. © 2016 Optical Society of America.1

Optical signal processing for efficient information networks

With the internet and rise of personal electronics there is an ever increasing amount of data collected and transmitted every day; modern communication systems will soon be overwhelmed. The driving force behind the demand is an increasing speed of signal acquisition, in the public domain, as well as medicine and industry; newer technologies allow massive amounts of data produced through text, voice, and video. This puts strain on both signal acquisition systems and communications systems to increase the total information flow. Transmission down fiber links is enabled by the large but limited bandwidth of optical fiber, and as we look toward the future, efficient use of the available optical bandwidth is paramount. I apply the large bandwidth of fiber and ultrafast speed of nonlinear optics to solve these problems, implementing high-speed and efficient signal acquisition and communication systems. With the increased volume of information being transferred, compression of data has become essential to allow multimedia communication. Data is acquired then compressed and transmitted, requiring massive computing power. Using the information theory technique coined “compressed sensing”, we demonstrate real time compression at signal acquisition, removing a timeconsuming and bandwidth inefficient step in a complete communication link. I use dispersion and nonlinear wave mixing in optical fiber, and gigahertz electro-optics to shape light at terahertz speeds, reaching towards the limit of compressed image acquisition. To complete a high-speed communications link, I investigate the use of Nyquist optical time division multiplexing to maximize spectral efficiency. The square spectral shape of a Nyquist pulse is ideal, but the pulse ripples on forever in the time domain, presenting problems for demultiplexing Nyquist signals at the receiver. I present a solution using coherent detection with a biorthogonal Nyquist pulse to eliminate interference from neighboring channels, and implement a proof of concept system using nonlinear wave mixing. Stable clock transfer is essential for coherent communication, but environmental fluctuations erode clock information, reducing the effective data rate of the communications channel. I present a versatile solution for stable time and frequency transfer using dispersion and nonlinear wave mixing in optical fiber

Versatile Optical Imaging Technique for Dynamic Monitoring and Quantitative Analysis in Tissue Engineering

Department of Biomedical EngineeringMany researches in the tissue engineering are investigating the development of technologies that have covered a broad range of applications and closely associated with the tissue regeneration and replacement of lost or damaged tissues as well as tissue manipulation. However, there are challenges regarding monitoring and assessing outcomes to analyze a variety of morphological and structural changes in tissue engineering applications. Most tissue engineering studies have utilized histopathological techniques for morphological analysis and evaluation of the tissues. Although the conventional methods provided a high definition and clear distinction under optical microscopy, it has still limitations in the visualization of tissue constructs without destruction of the tissues. Also, these methods have not allowed a volumetric assessment and functional information. Due to the destructive process and limited information in a two-dimensional approach, the conventional methods were difficult not only to analyze the specimens at continuous time points but also to compare inconsistencies of the results between different samples. For these reasons, there are clear needs for the development of advanced optical imaging techniques available for non-invasive and consistent observation and quantitative analysis in tissue engineering applications. Optical coherence tomography (OCT) has emerged as appropriate candidate for studying tissue morphology dynamically and quantitatively. OCT equips optimal imaging characteristics for dynamic monitoring because it offers cross-sectional, high-resolution, real-time tissue imaging in a non-invasive manner. Unlike most optical imaging techniques, OCT does not require any contrast agent or labeling process even it provides a deep penetration depth of about 2 mm in the tissue. Here, we utilized OCT technique to carry out application for the tissue engineering research ranging from the observation of biological tissues, dynamic monitoring, and quantitative analysis, as well as fabrication of image-guided engineered tissue. In the chapter 2, we utilized 3D OCT imaging to observe the tissue regeneration after laser irradiation, epidermal biopsy, and skin incision in in vitro and in vivo skin model. We utilized OCT system to monitor and analyze the wound recovery process after laser irradiation on the engineered skin. Also, we presented a quantitative evaluation of drug efficiency that affect the wound recovery on the engineered skin model after epidermal biopsy. Next, we analyzed quantitatively a recovery process of the wound width and depth in skin incised rat model in vivo with tissue adhesives treatment under the OCT monitoring. In the chapter 3, we utilized optical coherence microscopy (OCM) imaging modality to observe and quantitatively analyze the morphological changes of biological tissue in subcellular level. We introduced depth trajectory-tracking technique to acquire homogenous quality OCM images regardless of the height difference of the sample surface. Also, we developed the serial block-face OCM (SB-OCM) system to acquire the whole tissue information by repeating tissue sectioning and image acquisition using the serial block-face imaging technique. In the chapter 4, we developed the hand-held probe based portable OCT system for convenience in human target studies. We monitored and quantitatively analyzed various changes in the human skin using the hand-held probe based portable OCT system. Especially, we studied quantitative analysis of human skin wrinkle in terms of depth and volume as well as roughness parameters in comparison with conventional platforms. In the chapter 5, we suggested the feasibility to fabricate the engineered tissue based on a volumetric information of optical imaging. Here, we studied a fabrication of wrinkle mimicked engineered skin for anti-aging assessment and a protocol of imaging guided personalized engineered cornea for cornea transplantation. In conclusion, we confirmed that OCT system was able to provide various quantitative information from the biological tissues by its advantages such as high-resolution, non-invasive, label-free, deep penetration depth with real-time imaging. These characteristics of OCT imaging enables the quantitative analysis of tissue recovery and replacement as well as tissue manipulation in the tissue engineering research.clos

Optical Coherence Tomography Distal Sensor Based Handheld Microsurgical Tools

Microsurgery is typically differentiated from a general surgery in that it requires a precise sub-millimeter manipulation that could only be achievable under optical magnification. For instance, microsurgeons use surgical microscopes to view surgical sites and train themselves several years to acquire surgical skills to perform the delicate procedures. However, such microsurgical approach imposes considerable physical stress and mental fatigue on the surgeons and these could be sources for surgical risks and complications. For these reasons, a variety of robotic based surgical guidance methods have been developed and studied with the hope of providing safer and more precise microsurgery. These robotic arm based systems have been developed to provide precise tool movement and to remove physiological hand tremor, which is one of the main limiting factors that prevents precise tool manipulation. In another approaches use simpler system that adds robotic functions to existing handheld surgical tools. It is a hybrid system that incorporates the advantages of conventional manual system and robot-assist system. The advantages of such hybrid handheld systems include portability, disposability, and elimination of the large robotic-assist systems in complex surgical environment. The most critical benefit of the hybrid handheld system is its ease of use since it allows surgeons to manipulate tools mostly using their hand. However due to the imprecise nature of tool control using hands, tool tracking is more critical in handheld microsurgical tool systems than that of robotic arm systems. In general, the accuracy of the tool control is largely determined by the resolution of the sensors and the actuators. Therefore, it is essential to develop a real-time high resolution sensor in order to develop a practical microsurgical tools. For this reason, a novel intuitive targeting and tracking scheme that utilizes a common-path swept source optical coherence tomography (CP-SSOCT) distal sensor was developed integrated with handheld microsurgical tools. To achieve micron-order precision control, a reliable and accurate OCT distal sensing method was developed. The method uses a prediction algorithm is necessary to compensate for the system delay associated with the computational, mechanical and electronic latencies. Due to the multi-layered structure of retina, it was also necessary to develop effective surface detection methods rather than simple peak detection. The OCT distal sensor was integrated into handheld motion-guided micro-forceps system for highly accurate depth controlled epiretinal membranectomy. A touch sensor and two motors were used in the forceps design to minimize the motion artifact induced by squeezing, and to independently control the depth guidance of the tool-tip and the grasping action. We also built a depth guided micro-injector system that enables micro-injection with precise injection depth control. For these applications, a smart motion monitoring and a guiding algorithm were developed to provide precise and intuitive freehand control. Finally, phantom and ex-vivo bovine eye experiments were performed to evaluate the performance of the proposed OCT distal sensor and validate the effectiveness of the depth-guided micro-forceps and micro-injector over the freehand performance