Woo Choi - Academia.edu (original) (raw)

Papers by Woo Choi

Coherence Domain Optical Methods and Optical Coherence Tomography in Biomedicine X, 2006

We implemented a fiber-based optical coherence tomography (OCT) system by using a photonic crysta... more We implemented a fiber-based optical coherence tomography (OCT) system by using a photonic crystal fiber (PCF) coupler which could support an ultra-wideband spectral bandwidth. The PCF coupler fabricated by the fused biconical tapered (FBT) method showed rather flat coupling efficiency over a broad spectral bandwidth. Furthermore, the mode-field shapes at the output ports of the PCF coupler showed single mode

Foot & ankle international, Jan 13, 2015

Previous reports suggest that prolonged instability of the ankle may contribute to development of... more Previous reports suggest that prolonged instability of the ankle may contribute to development of osteochondral lesions and eventually lead to osteoarthritis. However, no studies have directly compared osteochondral lesions in ankles with chronic lateral ankle instability (CLAI) to those without instability. This study was performed to determine characteristics and resulting clinical outcomes associated with osteochondral lesions of the talus (OLT) in patients with and without instability. Of 420 patients who underwent primary arthroscopic marrow stimulation for OLT, 74 patients were identified as having concomitant CLAI. After considering age, sex, body mass index, and initial trauma history for the propensity score (1:2 ratio), a total of 148 patients without CLAI were matched from the remainder of the cohort. Demographics and lesion characteristics were compared using preoperative magnetic resonance imaging (MRI) and arthroscopy. Clinical outcomes were compared using a visual ana...

Yonsei medical journal, 2015

The aim of this study was to compare clinical and radiographic outcomes of proximal opening wedge... more The aim of this study was to compare clinical and radiographic outcomes of proximal opening wedge osteotomy using a straight versus oblique osteotomy. We retrospectively reviewed 104 consecutive first metatarsal proximal opening wedge osteotomies performed in 95 patients with hallux valgus deformity. Twenty-six feet were treated using straight metatarsal osteotomy (group A), whereas 78 feet were treated using oblique metatarsal osteotomy (group B). The hallux valgus angle (HVA), intermetatarsal angle (IMA), distal metatarsal articular angle, and distance from the first to the second metatarsal (distance) were measured for radiographic evaluation, whereas the American Orthopaedic Foot and Ankle Society (AOFAS) forefoot score was used for clinical evaluation. Significant corrections in the HVA, IMA, and distance from the first to the second metatarsal were obtained in both groups at the last follow-up (p<0.001). There was no difference in the mean IMA correction between the 2 group...

Korean Journal of Anesthesiology, 2008

The American journal of sports medicine, Jan 6, 2014

Several studies have reported on the outcome of arthroscopic treatment or osteochondral autologou... more Several studies have reported on the outcome of arthroscopic treatment or osteochondral autologous transplantation (OAT) for osteochondral lesions of the talus (OLT), with mixed results. None of these studies has compared the results of repeat arthroscopy and OAT after failed primary arthroscopic treatment. To compare the outcomes of OAT and repeat arthroscopy for the treatment of OLT after primary arthroscopy STUDY DESIGN: Cohort study; Level of evidence, 3. This study included 22 patients who underwent OAT (group A) and 22 patients who underwent repeat arthroscopy (group B) after failed treatment of OLT among 399 patients who received primary arthroscopic marrow stimulation at single institution between 2001 and 2009. All patients were evaluated clinically using the visual analog scale (VAS) for pain and American Orthopaedic Foot and Ankle Society (AOFAS) Ankle Hindfoot Scale. The cumulative success rates were compared by use of Kaplan-Meier life table analysis. The patients' ...

Foot & ankle international, 2014

Tendinopathy is a clinical problem for which treatment shows mixed results and treatment options ... more Tendinopathy is a clinical problem for which treatment shows mixed results and treatment options are limited. Gene expression signatures early in the mechanotransduction pathway can accurately predict risk and correlate with different clinical outcomes. Studies aimed at elucidating the molecular mechanisms of tendinopathy have focused on small cohorts of genes that show an incomplete picture of the degeneration process. This study compared the effect of cyclic strain on gene expression in tendon cells from normal tendon and chronically painful areas of tendinopathy in 3 patients. We measured a panel of mechanotransduction genes and cytoskeletal tensional balance with and without cyclic strain, which disrupts connective tissue synthetic-degradative equilibrium. Normal and degenerative tendons were obtained from patients undergoing surgery to treat chronic painful tendinopathy. A cyclic strain model was established to measure cytoskeletal tensional homeostasis. Prior to cyclic strain,...

Clinics in Podiatric Medicine and Surgery, 2013

The ultimate goal of primary total ankle replacement is to provide a well-balanced soft-tissue en... more The ultimate goal of primary total ankle replacement is to provide a well-balanced soft-tissue envelope around a well-aligned, well-fixated implant. Some surgeons have emphasized that good outcomes in total ankle replacement are more dependent on ligament balancing, along with the procedure itself, than the extent of preoperative coronal deformity in the ankle. Thus, it is imperative that the surgeon be familiar with additional procedures to address the varus, valgus, and other associated deformities commonly encountered in primary total ankle replacement.

Cancer research and treatment : official journal of Korean Cancer Association, 2008

Bone Morphogenetic Proteins (BMPs) are members of the TGF-beta superfamily and it has been demons... more Bone Morphogenetic Proteins (BMPs) are members of the TGF-beta superfamily and it has been demonstrated that BMPs enhance migration, invasion and metastasis. The purpose of this study was to identify the association between the serum BMP-2 level and the progression status of gastric cancer. Fifty-five patients with metastatic gastric cancer (metastatic disease group), six patients with early gastric cancer without lymph node metastasis (the EGC group), and ten healthy control subjects were enrolled in this study. The serum BMP-2 level was quantified by use of a commercially available ELISA kit. In EGC group patients and patients with metastatic disease, whole blood was obtained before endoscopic mucosal resection and before the commencement of a scheduled cycle of systemic chemotherapy, respectively. No significant difference in the mean serum BMP-2 levels was observed between the control subjects and the EGC group patients (87.95 pg/ml for the control subjects and 84.50 pg/ml for t...

Journal of biomedical optics, 2014

In breast-conserving surgery, an optical wire is a useful surgical guiding tool to optically loca... more In breast-conserving surgery, an optical wire is a useful surgical guiding tool to optically locate small lesions within the breast tissue. However, the use of a long silica glass fiber as the optical wire can be burdensome to patients because of its stiffness and nonbiocompatibility. We investigate the use of a biocompatible fiber for light localization in tissue. A surgical suture with a diameter of 400 μm and a few centimeters long is employed as the biocompatible optical waveguide to transport the visible laser light to the inner tissue site. Optical location is confirmed with glow ball-like red laser illumination at the tip of the suture embedded within a fresh chicken breast tissue. Effective optical power coupling to the suture is made by using a double-cladding fiber coupler. From this preliminary result, we realize practical light localization with biopolymer waveguides.

Journal of Korean Medical Science, 2007

The aims of this study were to analyze lymphocyte and eosinophil counts in consecutive peripheral... more The aims of this study were to analyze lymphocyte and eosinophil counts in consecutive peripheral blood samples taken during immunotherapy for metastatic renal cell carcinoma (mRCC) and to correlate the findings with objective response and survival. A total of 40 patients with mRCC who received immunotherapy with interleukin-2, interferon-alpha, and 5-fluorouracil were analyzed. Objective responses were observed in 14 patients, including 2 (5%) who showed a complete response (CR) and 12 (30%) who showed a partial response (PR). Eleven patients (27%) achieved stable disease (SD), and 15 patients (38%) had progressive disease (PD). Changes from baseline in the total lymphocyte counts were significantly higher in the responding patients (CR+PR+SD) than in the non-responding patients (PD) (p=0.017), but no difference was seen in the total eosinophil counts (p=0.275). Univariate analysis identified the Eastern Cooperative Oncology Group (ECOG) performance status (p=0.017), the presence of a primary renal tumor (p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001) and the peripheral lymphocyte counts at week 4 (p=0.034) as prognostic factors, but a low ECOG performance status (p=0.003) and the presence of a primary renal tumor (p=0.001) were identified as independent poor prognostic factors by multivariate analysis. This study provides further evidence that changes in blood lymphocyte counts may serve as an objective indicator of objective responses.

$Research paper thumbnail of Full-field optical coherence microscopy for identifying live cancer cells by quantitative measurement of refractive index distribution$

Optics Express, 2011

Chemical mechanical polishing (CMP) is a key process for global planarization of silicon wafers f... more Chemical mechanical polishing (CMP) is a key process for global planarization of silicon wafers for semiconductors and AlTiC wafers for magnetic heads. Removal rate of wafer material is directly dependent on the surface roughness of a CMP pad, thus the structure of the pad surface has been evaluated with variable techniques. However, under in situ CMP process, the measurements have been severely limited due to the existence of polishing fluids including the slurry on the pad surface. In here, we newly introduce ultra-high resolution full-field optical coherence tomography (FF-OCT) to investigate the surface of wet pads. With FF-OCT, the wet pad surface could be quantitatively characterized in terms of the polishing pad lifetime, and also be three-dimensionally visualized. We found that reasonable polishing span could be evaluated from the surface roughness measurement and the groove depth measurement made by FF-OCT.

Measurement Science and Technology, 2010

Korean Journal of Chemical Engineering, 2008

Journal of Electroceramics, 2006

Journal of Crystal Growth, 2005

The effect of InxGa1−xAs (x=0.1, 0.2) asymmetric strain release layers (ASRLs) on the microstruct... more The effect of InxGa1−xAs (x=0.1, 0.2) asymmetric strain release layers (ASRLs) on the microstructural and the interband transition properties of InAs/GaAs quantum dots (QDs) grown by using molecular beam epitaxy (MBE) and atomic layer epitaxy was investigated by using high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) measurements. When the thickness of the ASRL covering the QDs was increased in

Journal of Biomedical Optics, 2012