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

OPTICAL COHERENCE TOMOGRAPHY FOR NEUROSURGEY AND CANCER RESEARCH

Optical Coherence Tomography (OCT) provides non-labeling, real-time and high resolution images, which has the potential to transform the paradigm of surgical guidance and preclinical animal studies. The design and development of OCT devices for neurosurgery guidance and novel imaging algorithms for monitoring anti-cancer therapy have been pursued in this work. A forward-imaging needle-type OCT probe was developed which can fit into minimally invasive tools (I.D. ~ 1mm), detect the at-risk blood vessels, and identify tissue micro-landmarks. This promising guidance tool improves the safety and the accuracy of needle-based procedures, which are currently performed without imaging feedback. Despite the great imaging capability, OCT is limited by the shallow imaging depth (1-2 mm). In order to address this issue, the first MRI compatible OCT system has been developed. The multi-scale and multi-contrast MRI/OCT imaging combination significantly improves the accuracy of intra-operative MRI by two orders (from 1mm to 0.01 mm). In contrast to imaging systems, a thin (0.125 mm), low-cost (1/10 cost of OCT system) and simple fiber sensor technology called coherence gated Doppler (CGD) was developed which can be integrated with many surgical tools and aid in the avoidance of intracranial hemorrhage. Furthermore, intra-vital OCT is a powerful tool to study the mechanism of anti-cancer therapy. Photo-immunotherapy (PIT) is a low-side-effect cancer therapy based on an armed antibody conjugate that induces highly selective cancer cell necrosis after exposure to near infrared light both in vitro and in vivo. With novel algorithms that remove the bulk motion and track the vessel lumen automatically, OCT reveals dramatic hemodynamic changes during PIT and helps to elucidate the mechanisms behind the PIT treatment. The transformative guidance tools and the novel image processing algorithms pave a new avenue to better clinical outcomes and preclinical animal studies

DESIGN, DEVELOPMENT, AND EVALUATION OF A DISCRETELY ACTUATED STEERABLE CANNULA

Needle-based procedures require the guidance of the needle to a target region to deliver therapy or to remove tissue samples for diagnosis. During needle insertion, needle deflection occurs due to needle-tissue interaction which deviates the needle from its insertion direction. Manipulating the needle at the base provides limited control over the needle trajectory after the insertion. Furthermore, some sites are inaccessible using straight-line trajectories due to delicate structures that need to be avoided. The goal of this research is to develop a discretely actuated steerable cannula to enable active trajectory corrections and achieve accurate targeting in needle-based procedures. The cannula is composed of straight segments connected by shape memory alloy (SMA) actuators and has multiple degrees-of-freedom. To control the motion of the cannula two approaches have been explored. One approach is to measure the cannula configuration directly from the imaging modality and to use this information as a feedback to control the joint motion. The second approach is a model-based controller where the strain of the SMA actuator is controlled by controlling the temperature of the SMA actuator. The constitutive model relates the stress, strain and the temperature of the SMA actuator. The uniaxial constitutive model of the SMA that describes the tensile behavior was extended to one-dimensional pure- bending case to model the phase transformation of the arc-shaped SMA wire. An experimental characterization procedure was devised to obtain the parameters of the SMA that are used in the constitutive model. Experimental results demonstrate that temperature feedback can be effectively used to control the strain of the SMA actuator and image feedback can be reliably used to control the joint motion. Using tools from differential geometry and the configuration control approach, motion planning algorithms were developed to create pre-operative plans that steer the cannula to a desired surgical site (nodule or suspicious tissue). Ultrasound-based tracking algorithms were developed to automate the needle insertion procedure using 2D ultrasound guidance. The effectiveness of the proposed in-plane and out-of-plane tracking methods were demonstrated through experiments inside tissue phantom made of gelatin and ex-vivo experiments. An optical coherence tomography probe was integrated into the cannula and in-situ microscale imaging was performed. The results demonstrate the use of the cannula as a delivery mechanism for diagnostic applications. The tools that were developed in this dissertation form the foundations of developing a complete steerable-cannula system. It is anticipated that the cannula could be used as a delivery mechanism in image-guided needle-based interventions to introduce therapeutic and diagnostic tools to a target region

Imaging Sensors and Applications

In past decades, various sensor technologies have been used in all areas of our lives, thus improving our quality of life. In particular, imaging sensors have been widely applied in the development of various imaging approaches such as optical imaging, ultrasound imaging, X-ray imaging, and nuclear imaging, and contributed to achieve high sensitivity, miniaturization, and real-time imaging. These advanced image sensing technologies play an important role not only in the medical field but also in the industrial field. This Special Issue covers broad topics on imaging sensors and applications. The scope range of imaging sensors can be extended to novel imaging sensors and diverse imaging systems, including hardware and software advancements. Additionally, biomedical and nondestructive sensing applications are welcome

Enhanced visualization of fine needles under sonographic guidance using a MEMS actuator

Localization of a needle tip is important for biopsy examinations in clinics. However, the needle tip is sometimes difficult to discern under the guidance of sonography due to its poor visibility. A mini actuator that radiates a low-intensity ultrasound wave was manufactured using micro-electro-mechanical system (MEMS) technology. Interference between the radiated and diagnostic ultrasound pulses was observed as bright lines in the B-mode ultrasound image, from which the mini actuator could be recognized with ease. Because the distance between the mini actuator and the needle tip is fixed, the needle tip can be determined despite its inconsistent appearance in the sonography. Both gel phantom and ex vivo tissue evaluation showed that the needle tip can be determined reliably utilizing the acoustic interference pattern.Published versio