• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.123-126
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• 1997

We present a method for the estimation of 3D solid angle assessment of the acetabular coverage of the femoral head in 3D space. At first, femoral head and acetabulum is segmented from the original CT scan images. The slice thickness is 1.5mm and the number of slices is usually 30-40 to cover the entire acetabulum. The superior half of the femoral head is modeled as part of a sphere. Thus, the axial cross sections of the upper half of the femoral head are also modeled as circles. A set of points from each outline image of femoral head is fitted recursively into a circle by minimizing root-mean-square (RMS) error. With these fitted circles, a center point of the femoral head model is evaluated. This is a reference point for calculating the solid angle of the acetabular inner surface. Next, the tangent lines connecting from a set of points of the acetabular edge to the center of the fitted sphere are obtained. The lines pass through the unit sphere whose center is the same as that of the femoral head. With the points on the unit sphere, we calculate area and estimate the solid angle. Based on this solid angle, the deformity of the acetabulum is analyzed. In case of normal subject, the solid angle is about 4.3 (rad) and acetabular coverage is 68%.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.66-71
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• 1998

High spatial resolution ultrasonic imaging is necessary in several fields of investigation, in order to permit greater precision of clinical diagnosis in the dermatology, ophthalmology etc. We present a B-mode scan system using sector scanning probe of 20MHz center frequency. This developed system allow the high resolution image of 250${\mu}m$ in lateral and 80${\mu}m$ in axial, which of display the size of a $5mm {\times} 5mm$ image with 20 frames/sec. We have shown the images of various structural elements of the human skin and of the nail. We have compared the skin images obtained for each of the different age and we have shown in a general with the age, the atrophy of the skin thickness and the appearance of the abnormal hypoechogene band under epidermis (named SENEB : Sub Epidermal Non Echogene Band).

• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.176-182
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• 2006

Although several artificial disc designs have been developed for the treatment of discogenic low back pain, biomechanical changes with its implantation were rarely studied. To evaluate the effect of artificial disc implantation on the biomechanics of functional spinal unit, a nonlinear three-dimensional finite element model of L4-L5 was developed with 1-mm CT scan data. Biomechanical analysis was performed for two different types of artificial disc having constrained and unconstrained instant center of rotation(ICR), ProDisc and SB Charite III model. The implanted model predictions were compared with that of intact model. Angular motion of vertebral body, forces on the spinal ligaments and facet joint, and stress distribution of vertebral endplate for flexion-extension, lateral bending, and axial rotation with a compressive preload of 400N were compared. The implanted model showed increased flexion-extension range of motion compared to that of intact model. Under 6Nm moment, the range of motion were 140%, 170% and 200% of intact in SB Charite III model and 133%, 137%, and 138% in ProDisc model. The increased stress distribution on vertebral endplate for implanted cases could be able to explain the heterotopic ossification around vertebral body in clinical observation. As a result of this study, it is obvious that implanted segment with artificial disc suffers from increased motion and stress that can result in accelerated degenerated change of surrounding structure. Unconstrained ICR model showed increased in motion but less stress in the implanted segment than constrained model.

• Journal of Korean Neurosurgical Society
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• v.52 no.6
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• pp.541-546
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• 2012

Objective : The prefabrication of customized cranioplastic implants has been introduced to overcome the difficulties of intra-operative implant molding. The authors present a new technique, which consists of the prefabrication of implant molds using three-dimensional (3D) printers and polymethyl-methacrylate (PMMA) casting. Methods : A total of 16 patients with large skull defects (>100 $cm^2$) underwent cranioplasty between November 2009 and April 2011. For unilateral cranial defects, 3D images of the skull were obtained from preoperative axial 1-mm spiral computed tomography (CT) scans. The image of the implant was generated by a digital subtraction mirror-imaging process using the normal side of the cranium as a model. For bilateral cranial defects, precraniectomy routine spiral CT scan data were merged with postcraniectomy 3D CT images following a smoothing process. Prefabrication of the mold was performed by the 3D printer. Intraoperatively, the PMMA implant was created with the prefabricated mold, and fit into the cranial defect. Results : The median operation time was $184.36{\pm}26.07$ minutes. Postoperative CT scans showed excellent restoration of the symmetrical contours and curvature of the cranium in all cases. The median follow-up period was 23 months (range, 14-28 months). Postoperative infection was developed in one case (6.2%) who had an open wound defect previously. Conclusion : Customized cranioplasty PMMA implants using 3D printer may be a useful technique for the reconstruction of various cranial defects.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.10a
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• pp.56-56
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• 1999

For advanced TFT-LCD manufacturing processes, dry etching of thin-film layers(a-Si, $SiN_x$, SID & gate electrodes, ITO etc.) is increasingly preferred instead of conventional wet etching processes. To dry etch Al gate electrode which is advantageous for reducing propagation delay time of scan signals, high etch rate, slope angle control, and etch uniformity are required. For the Al gate electrode, some metals such as Ti and Nd are added in Al to prevent hillocks during post-annealing processes in addition to gaining low-resistivity($<10u{\Omega}{\cdot}cm$), high performance to heat tolerance and corrosion tolerance of Al thin films. In the case of AI-Nd alloy films, however, low etch rate and poor selectivity over photoresist are remained as a problem. In this study, to enhance the etch rates together with etch uniformity of AI-Nd alloys, magnetized inductively coupled plasma(MICP) have been used instead of conventional ICP and the effects of various magnets and processes conditions have been studied. MICP was consisted of fourteen pairs of permanent magnets arranged along the inside of chamber wall and also a Helmholtz type axial electromagnets was located outside the chamber. Gas combinations of $Cl_2,{\;}BCl_3$, and HBr were used with pressures between 5mTorr and 30mTorr, rf-bias voltages from -50Vto -200V, and inductive powers from 400W to 800W. In the case of $Cl_2/BCl_3$ plasma chemistry, the etch rate of AI-Nd films and etch selectivity over photoresist increased with $BCl_3$ rich etch chemistries for both with and without the magnets. The highest etch rate of $1,000{\AA}/min$, however, could be obtained with the magnets(both the multi-dipole magnets and the electromagnets). Under an optimized electromagnetic strength, etch uniformity of less than 5% also could be obtained under the above conditions.

• Korean Journal of Bronchoesophagology
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• v.6 no.1
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• pp.7-15
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• 2000

Background and Objectives:Submucosal spread of hypopharyngeal canceris frequently incriminated for the high incidence of local recurrence after resection. Although mucosal spread is better detected by means of direct visualization, submucosal spread is better evaluated by using cross-sectional imaging rather than endoscopy. This study was designed to evaluate the efficacy of MRI in diagnosing involvement of inferior margin of hypopharyngeal cancer. Materials and Method : Eight patients with hypopharyngeal cancer underwent MRI prior to surgery. And postoperative histopathopogic involvement of tumor was compared with the preoperative MRI axial scan. Results : In preoperative MRI findings, involvement of pyriform sinus apex was 6 cases(definitive 5 cases, probable 1 cases), that of esophageal inlet was 1 case(probable), that of cervical esophagus was 1 case(probable). In postoperative histopathologic findings, the results were same. Conclusion : MRI evaluation for patient with hypopharyngeal cancer ensures accurate staging and provides essential information about the tumor involvement of inferior margin. And there is needed to be thin section thickness in evaluation of inferior margin of hypopharyngeal cancer.

• Smart Media Journal
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• v.5 no.1
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• pp.44-48
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• 2016

In a longitudinal neuroimaging study, the upgrades of a magnetic resonance imaging (MRI) scanner due to outdated hardwares and softwares make it difficult to maintain the same MRI conditions in the long-term research period. Particularly, high field MRI systems such 3T scanners become popular in recent years. However, it is still unclear whether an integrated analysis of 3T and 1.5T images is possible without consideration of the field strength. In this study, we evaluated the reproducibility of hippocampal volumes between brain images with different field strengths and slice orientations. 296 participants underwent both 3T and 1.5T MRI and both sagittal and axial scans for high resolution brain images, and their hippocampal volumes were measured using Freesurfer, a well-known software for neuroimaging analysis. Paired t-tests showed that the hippocampal volumes were significantly different between the image types. These results suggest that it is necessary to develop data analysis techniques for integrating diverse types of MRI images.

• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.91-96
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• 2013

We report a method for optical monitoring of tumors in an animal model using optical coherence tomography (OCT). In a spectral domain OCT system, a superluminescent diode light source with a full width of 66 nm at half maximum and peak wavelength of 950 nm was used to take images having an axial resolution of 6.8 ${\mu}m$. Cancer cells of PC-3 were cultured and inoculated into the hypodermis of auricle tissues in BALB/c nude mice. We observed tumor formation and growth at the injection region of cancer cells in vivo and obtained the images of tumor mass center and sparse circumferences. On the $5^{th}$ day from an inoculation of cancer cells, histological images of the tumor region using cross-sectional slicing and dye staining of specimens were taken in order to confirm the correlation with the high resolution OCT images. The OCT image of tumor mass compared with normal tissues was analyzed using its A-scan data so as to obtain a tissue attenuation rate which increases according to tumor growth.

• Clinics in Shoulder and Elbow
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• v.22 no.1
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• pp.3-8
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• 2019

Background: This study aimed to compare the subscapularis muscle volume between the intact groups (group I) and supraspinatus tendon tear groups (group T) based on the sex and three different age groups. Methods: Subjects with a group I and subjects with group T without any other lesions were retrospectively evaluated from among patients who received a magnetic resonance imaging (MRI) scan between January 2011 and December 2013. The MRI scans were studied by a consultant radiologist. The subscapularis muscle volume was compared according to the age and sex; the age groups were categorized as patients in their 40s, 50s, and 60s. The volume of subscapularis muscle was measured by three-dimensional reconstructed images acquired through the axial section of 1.5T MRI. Results: No statistically significant differences were observed between subscapularis muscle volume of the group I and group T, except for male patients in their 50s (group I: $100,650mm^3$ vs. group T: $106,488mm^3$) and 60s (group I: $76,347mm^3$ vs. group T: $99,549mm^3$) (p<0.05). Males had a larger mean volume of subscapularis muscle than females, and the subscapularis muscle volume decreased in a linear manner with increasing age. Conclusions: Decrease in subscapularis muscle volume was observed with increasing age, and the impact of supraspinatus tear on subscapularis muscle volume is age and sex dependent.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.211-218
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• 2019

Purpose: The purpose of the present study was to compare the accuracy of four different metal copings fabricated by CAD/CAM technology and to evaluate clinical effectiveness. Materials and methods: Composite resin tooth of the maxillary central incisor was prepared for a metal ceramic crown and duplicated metal die was fabricated. Then scan the metal die for 12 times to obtain STL files using a confocal microscopy type oral scanner. Metal copings with a thickness of 0.5 mm and a cement space of $50{\mu}m$ were designed on a CAD program. The Co-Cr metal copings were fabricated by the following four methods: Wax pattern milling & Casting (WM), Resin pattern 3D Printing & casting (RP), Milling & Sintering (MS), Selective laser melting (SLM). Silicone replica technique was used to measure marginal and internal discrepancies. The data was statistically analyzed with One-way analysis of variance and appropriate post hoc test (Scheffe test) (${\alpha}=.05$). Results: Mean marginal discrepancy was significantly smaller in the Group WM ($27.66{\pm}9.85{\mu}m$) and Group MS ($28.88{\pm}10.13{\mu}m$) than in the Group RP ($38.09{\pm}11.14{\mu}m$). Mean cervical discrepancy was significantly smaller in the Group MS than in the Group RP. Mean axial discrepancy was significantly smaller in the Group WM and Group MS then in the Group RP and Group SLM. Mean incisal discrepancies was significantly smaller in the Group RP than in all other groups. Conclusion: The marginal and axial discrepancies of the Co-Cr coping fabricated by the Wax pattern milling and Milling/Sintering method were better than those of the other groups. The marginal, cervical and axial fit of Co-Cr copings in all groups are within a clinically acceptable range.