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Department of Biomedical EngineeringThe optical imaging has a critical role in biomedical research to analyze functional and morphological variation of an organ, tissue and even a single cell of animal models. Since the optical imaging modality has features of indirect access, volumetric analysis and high resolution, it has been used for biomedical analysis. Especially, as a low coherence interferometric imaging technique, optical coherence tomography (OCT) has been applied in scientific and medical fields from few decades ago. Since OCT can provide endogenous contrast of biological tissue using the infrared light source, it has high potential to be applied in practical medical diagnosis. However, it is hard to acquire uneven or thick sample due to the limited imaging window and penetration depth. To overcome those limitations, lots of optical, mathematical and chemical solutions comes within a decade such as adaptive optics, full-range method and tissue clearing. Despite the existence of suggested solutions, practical application of OCT is limitation due to the cost of time and effort. Here, we present practical methods to enhance acquirable endogenous information of sample through versatile scanning optical coherence tomography(VS-OCT). Conventional OCT utilizes dual-axis based flat focal plane scanning method providing limited depth information of curved samples. Thus, we developed advanced OCT, called VS-OCT, which can fully optimize imaging window by changing focal plane to dual plane and cylindrical plane. The VS-OCT is demonstrated for 1) quantification of engineered skin, 2) monitoring of tadpole development, 3) screening phenotype of zebrafish and 4) quantification of spinal cord injury (SCI) of mouse.ope

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

Smartphone-Based Endoscope System for Advanced Point-of-Care Diagnostics: Feasibility Study

Background: Endoscopic technique is often applied for the diagnosis of diseases affecting internal organs and image-guidance of surgical procedures. Although the endoscope has become an indispensable tool in the clinic, its utility has been limited to medical offices or operating rooms because of the large size of its ancillary devices. In addition, the basic design and imaging capability of the system have remained relatively unchanged for decades. Objective: The objective of this study was to develop a smartphone-based endoscope system capable of advanced endoscopic functionalities in a compact size and at an affordable cost and to demonstrate its feasibility of point-of-care through human subject imaging. Methods: We developed and designed to set up a smartphone-based endoscope system, incorporating a portable light source, relay-lens, custom adapter, and homebuilt Android app. We attached three different types of existing rigid or flexible endoscopic probes to our system and captured the endoscopic images using the homebuilt app. Both smartphone-based endoscope system and commercialized clinical endoscope system were utilized to compare the imaging quality and performance. Connecting the head-mounted display (HMD) wirelessly, the smartphone-based endoscope system could superimpose an endoscopic image to real-world view. Results: A total of 15 volunteers who were accepted into our study were captured using our smartphone-based endoscope system, as well as the commercialized clinical endoscope system. It was found that the imaging performance of our device had acceptable quality compared with that of the conventional endoscope system in the clinical setting. In addition, images captured from the HMD used in the smartphone-based endoscope system improved eye-hand coordination between the manipulating site and the smartphone screen, which in turn reduced spatial disorientation. Conclusions: The performance of our endoscope system was evaluated against a commercial system in routine otolaryngology examinations. We also demonstrated and evaluated the feasibility of conducting endoscopic procedures through a custom HMD

One-photon and two-photon stimulation of neurons in a microfluidic culture system

In this paper, we demonstrate a novel platform for optical stimulation of neural circuits combined with microfluidic culture method and microelectrode-arrays measurement. Neuron-on-a-chip was designed and fabricated to isolate axons without a soma or dendrite. Thus, it is readily able to manipulate the neuronal alignment and to investigate the neuronal activity at the locations we want to observe. We adapted the optical stimulation technique to the arranged neurons to generate the neuronal signals in a non-invasive fashion. A blue light emitting diode and a femtosecond laser with 780 nm center wavelength were used for neuronal activation, and the corresponding neuronal signals were measured by MEAs at the same time. We found that one-photon light via caged glutamate provoked periodic spiking. In contrast the femtosecond pulse irradiation generated the repetitive firing at constant rates. Response times of one-photon and two-photon stimulation were around 200 ms and 50 ms, respectively. We also quantified neural responses, by varying optical parameters such as exposure time and irradiation power.clos