We present an ultra-thin fiber-body endoscopy probe for optical coherence tomography (OCT) which is based on a stepwise transitional core (STC) fiber. In a minimalistic design, our probe was made of spliced specialty fibers that could be directly used for beam probing optics without using a lens. In our probe, the OCT light delivered through a single-mode fiber was efficiently expanded to a large mode field of 24 μm diameter for a low beam divergence. The size of our probe was 85 μm in the probe's diameter while operated in a 160-μm thick protective tubing. Through theoretical and experimental analyses, our probe was found to exhibit various attractive features in terms of compactness, flexibility and reliability along with its excellent fabrication simplicity.

This study is the first experimental trial, assessing the value of multimodal imaging using OCT and EUS in a rabbit VX2 laryngeal tumor model. Combining OCT and EUS helped to identify changes in laryngeal mucous membranes, and could potentially be used to identify laryngeal tumors and predict how tumors progress. This combined modality could help in determining tumor extent, assisting in diagnosis, and establishing a treatment plan for laryngeal cancer.

The 3D printing technique was able to reliably fabricate the double-layered phantoms emulating a variety of skin types (I-VI) along with the comparable optical and mechanical properties. Further investigations will incorporate artificial chromophores into the fabricated skin phantoms to reliably evaluate the new therapeutic wavelengths for laser tattoo removal.

Endovenous laser ablation (EVLA) has frequently been used to treat varicose veins for 20 years. In spite of 90˜95% occlusion rates, clinical complications such as burn and ecchymosis still occur due to excessive thermal injury to perivenous tissue. In the current study, a glass-capped diffusing applicator is designed to validate the feasibility of EVLA as an effective therapeutic device by applying circumferential light distribution. The proposed device is evaluated with a flat fiber as a reference in terms of temperature elevation, fiber degradation, and degree of coagulative necrosis after 532 nm-assisted EVLA at 100 J/cm. The diffusing fiber generates a 40% lower maximum temperature with a 90% lower transient temperature change in blood, compared to the flat fiber. Due to low irradiance (13.5 kW/cm ) and wide light distribution, the diffuser tip experiences no significant thermal degradation while severe carbonization occurs at the flat fiber tip. Ex vivo tissue tests verify that the diffusing fiber induces circumferential and consistent tissue denaturation to the vein wall (107.8 ± 7.8 µm) along with 19% vessel shrinkage. The proposed glass-capped diffusing applicator can be a feasible therapeutic device for EVLA with minimal complications by entailing low maximum temperatures and uniform tissue denaturation in the venous tissue.

Acquired airway injury is frequently caused by endotracheal intubations, long-term tracheostomies, trauma, airway burns, and some systemic diseases. An effective and less invasive technique for both the early assessment and the early interventional treatment of acquired airway stenosis is therefore needed. Optical coherence tomography (OCT) has been proposed to have unique potential for early monitoring from the proliferative epithelium to the cartilage in acute airway injury. Additionally, stem cell therapy using adipose stem cells is being investigated as an option for early interventional treatment in airway and lung injury. Over the past decade, it has become possible to monitor the level of injury using OCT and to track the engraftment of stem cells using stem cell imaging in regenerative tissue. The purpose of this study was to assess the engraftment of exogenous adipose stem cells in injured tracheal epithelium with fluorescent microscopy and to detect and monitor the degree of airway injury in the same tracheal epithelium with OCT. OCT detected thickening of both the epithelium and basement membrane after tracheal scraping. The engraftment of adipose stem cells was successfully detected by fluorescent staining in the regenerative epithelium of injured tracheas. OCT has the potential to be a high-resolution imaging modality capable of detecting airway injury in combination with stem cell imaging in the same tracheal mucosa. Berns, S. C. George, Z. Chen, and M. Brenner, "Detection and monitoring of early airway injury effects of halfmustard (2-chloroethylethylsulfide) exposure using high-resolution optical coherence tomography," J. Biomed.

We performed a feasibility study of in vivo visualization of real-time airway dynamics. To our best knowledge, this is the first report of real-time integrated airway dynamics including the right intermedius bronchus and alveoli during a bronchial challenge test. OCT showed bronchial constriction and alveolar collapse with a higher methacholine dose. OCT images correlated with the measured airway resistance. Therefore, OCT could be a potential diagnostic device for airway hyper-responsiveness and airway remodeling.

Mechanical property of tissue is closely related to diseases such as breast cancer, prostate cancer, cirrhosis of the liver, and atherosclerosis. Therefore measurement of tissue mechanical property is important for a better diagnosis. Ultrasound elastography has been developed as a diagnostic modality for a number of diseases that maps mechanical property of tissue. Optical coherence elastography (OCE) has a higher spatial resolution than ultrasound elastography. OCE, therefore, could be a great help for early diagnosis. In this study, we made tissue phantoms and measured their compressive moduli with a rheometer measuring the response to applied force. Uniaxial strain of the tissue phantom was also measured with OCE by using cross-correlation of speckles and compared with the results from the rheometer. In order to compare stiffness of tissue phantoms by OCE, the applied force should be measured in addition to the strain. We, however, did not use a load cell that directly measures the applied force for each sample. Instead, we utilized one silicone film (called as reference phantom) for all OCE measurements that indirectly indicated the amount of the applied force by deformation. Therefore, all measurements were based on displacement, which was natural and effective for image-based elastography such as OCE.

Sarcopenia, or reduced muscle mass and volume, is due to various factors such as senile change, neuronal degeneration, drug, malignancy, and sepsis. Sarcopenia with the aging process has been evidenced by the decline in muscle mass by 0.5 to 1% per year with 3-5% reduction in muscle strength for 10 years between the ages of 40 and 50, and a 1-2% of decline of mass every year in people aged 60-70. Therefore, early diagnosis and understanding the mechanism of sarcopenia are crucial in the prevention of muscle loss. However, it is still difficult to image changes of muscle microstructure due to a lack of techniques. In this study, we developed an animal model using denervated rats to induce a rapid atrophy in the tibialis anterior (TA) and imaged its structural changes using optical coherence tomography (OCT) along with histologic and ultrasound analyses. Ultrasound showed changes of overall muscle size. Histology revealed that the atrophic TA muscle displayed an increased size variability of muscle fiber and inflammatory changes. Three dimensional OCT imaged the changes of perimysial grid and muscle fiber structure in real time without sacrifice. These observed advantages of multimodal imaging using OCT and ultrasound would provide clinical benefits in the diagnosis of sarcopenia.