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하악 무치악 부위의 임플란트 이식을 위한 전산화단층촬영 영상의 비교 평가
선경훈,정호걸,박혁,박창서,김기덕 대한구강악안면방사선학회 2009 Imaging Science in Dentistry Vol.39 No.1
Purpose : The purpose of this study was to evaluate the clinical usefulness of the recently developed multi-detector computed tomography and cone beam computed tomography in pre-operative implant evaluation, by comparing them with the single detector computed tomography, already confirmed for accuracy in this area. Materials and Methods : Five partially edentulous dry human mandibles, with 1×1 mm gutta percha cones, placed in 5 mm intervals posterior to the mental foramen on each side of the buccal part of the mandible, were used in this study. They were scanned as follows: 1) Single detector computed tomography: slice thickness 1 mm, 200 mA, 120 kV 2) Multi-detector computed tomography: slice thickness 0.75 mm, 250 mA, 120 kV 3) Cone beam computed tomography: 15 mAs, 120 kV Axial images acquired from three computed tomographies were transferred to personal computer, and then reformatted cross-sectional images were generated using V-Implant 2.0 (CyberMed Inc., Seoul, Korea) software. Among the cross-sectional images of the gutta percha cone, placed in the buccal body of the mandible, the most precise cross section was selected as the measuring point and the distance from the most superior border of the mandibular canal to the alveolar crest was measured and analyzed 10 times by a dentist. Results : There were no significant intraobserver differences in the distance from the most superior border of the mandibular canal to the alveolar crest (p>0.05). There were no significant differences among single detector computed tomography, multi-detector computed tomography and cone beam computed tomography in the distance from the most superior border of the mandibular canal to the alveolar crest (p>0.05). Conclusion : Multi-detector computed tomography and cone beam computed tomography are clinically useful in the evaluation of pre-operative site for mandibular dental implants, with consideration for radiation exposure dose and scanning time.
두개골의 3차원 영상 분석을 위한 전산화단층촬영 방법의 비교 : 상층 두께가 3차원 영상의 계측에 미치는 영향
정호걸,김기덕,박혁,김동욱,정해조,김희중,유선국,김용욱,박창서 대한구강악안면방사선학회 2004 Imaging Science in Dentistry Vol.34 No.3
Purpose : To evaluate the quantitative accuracy of three-dimensional (3D) images by means of comparing distance measurements on the 3D images with direct measurements of dry human skull according to slice thickness and scanning modes. Materials and Mathods : An observer directly measured the distance of 21 line items between 12 orthodontic landmarks on the skull surface using a digital vernier caliper and each was repeated five times. The dry human skull was scanned with a Helical CT with various slice thickness (3, 5, 7 mm) and acquisition modes (Conventional and Helical). The same observer measured corresponding distance of the same items on reconstructed 3D images with the internal program of V-works 4.0 (Cybermed Inc., Seoul, Korea). The quantitative accuracy of distance measurements were statistically evaluated with Wilcoxons’ two-sample test. Results : 11 line items in Conventional 3 mm, 8 in Helical 3mm, 11 in Conventional 5 mm, 10 in Helical 5 mm, 5 in Conventional 7 mm and 9 in Helical 7 mm showed no statistically significant difference. Average difference between direct measurements and measurements on 3D CT images was within 2 mm in 19 line items of Conventional 3 mm, 20 of Helical 3 mm, 15 of Conventional 5 mm, 18 of Helical 5 mm, 11 of Conventional 7mm and 16 of Helical 7 mm. Conclusion : Considering image quality and patient’s exposure time, scanning protocol of Helical 5 mm is recommended for 3D image analysis of the skull in CT.
Optimization of Operating Conditions for 112-Gb/s Polarization-Multiplexed 16-QAM Optical Modulation
Sun Hyok Chang,Hwan Seok Chung,Kwangjoon Kim IEEE 2011 IEEE photonics technology letters Vol.23 No.11
<P>In this letter, we analyze a 16-ary quadrature amplitude modulation (16-QAM) optical signal generated by applying four-level electrical signals to a single in-phase/quadrature (IQ)-modulator. The amplitude of optical output of the Mach-Zehnder modulator (MZM) in the IQ-modulator needs to be carefully adjusted, and the limited extinction ratio of MZM results in unwanted phase offset. Required optical signal-to-noise ratio is estimated in the 112-Gb/s polarization-division-multiplexed (PDM) 16-QAM signal by numerical simulations with various amplitudes of the electrical modulation signals. Optimal operating conditions are found to guarantee the best performance of the received PDM 16-QAM signal.</P>
Impact of Quadrature Imbalance in Optical Coherent QPSK Receiver
Sun Hyok Chang,Hwan Seok Chung,Kwangjoon Kim IEEE 2009 IEEE photonics technology letters Vol.21 No.11
<P>In this letter, we present the impact of quadrature imbalance in an optical coherent quadrature phase-shift-keying (QPSK) receiver. Arbitrary conjugate misalignment was realized in all-fiber optical hybrid and two correction algorithms of quadrature imbalance, the ellipse correction method, and the Gram-Schmidt orthogonalization method, were independently applied. Bit-error-rate curves versus optical signal-to-noise ratio (OSNR) were measured for the 20-Gb/s optical QPSK signal. We show that OSNR penalty is reduced from ~6 to 1 dB at ~20deg conjugate misalignment with the help of correction algorithms.</P>
Mode division multiplexed optical transmission enabled by all-fiber mode multiplexer.
Chang, Sun Hyok,Chung, Hwan Seok,Fontaine, Nicolas K,Ryf, Roland,Park, Kyung Jun,Kim, Kwangjoon,Lee, Jyung Chan,Lee, Jong Hyun,Kim, Byoung Yoon,Kim, Young Kie Optical Society of America 2014 Optics express Vol.22 No.12
<P>Mode division multiplexed optical transmission enabled by all-fiber mode multiplexer is investigated. The proposed all-fiber mode multiplexer is composed of consecutive mode selective couplers. It multiplexes or demultiplexes LP01, LP11, LP21, and LP02 modes simultaneously. We demonstrate successful transmission of three spatial modes with 120 Gb/s PDM-QPSK signals over 15 km of four mode fiber by using 6x6 MIMO digital signal processing.</P>
Performance of Bipolar Optical Spectral Encoding CDMA with Modified PN Codes
Sun Hyok Chang,김봉규,Heuk Park,Won Kyoung Lee,김광준 한국전자통신연구원 2006 ETRI Journal Vol.28 No.4
Experimental demonstration of bipolar spectral encoding code-division multiple-access with modified pseudorandom noise codes is presented. Bipolar spectral encoding is achieved with an erbium-doped fiber amplifier amplified spontaneous emission source and arrayed waveguide gratings. The bit-error rate performance of 1.25 Gbps signal transmission over 80 km single mode fiber is measured in a multiple-user environment.
All-fiber 6-mode multiplexers based on fiber mode selective couplers
Chang, Sun Hyok,Moon, Sang-Rok,Chen, Haoshuo,Ryf, Roland,Fontaine, Nicolas K.,Park, Kyung Jun,Kim, Kwangjoon,Lee, Joon Ki The Optical Society 2017 Optics express Vol.25 No.5
<P>All-fiber 6-mode multiplexer composed of two consecutive LP11-mode selective couplers (MSC), two LP21-MSCs and an LP02-MSC is fully characterized by wavelength-swept interferometer technique. The MSCs are fabricated by polished-type fiber couplers coupling LP01 mode of a single mode fiber into a higher-order mode of a few mode fiber. A pair of the mode multiplexers has minimum mode dependent loss of 4 dB and high mode group selectivity of over 15 dB. Mode division multiplexed transmission enabled by the all-fiber mode multiplexers is demonstrated over fiber spans of 117 km employing an in-line multi-mode optical amplifier. 6 modes of 120 Gb/s dual polarization quadrature phase shift keying signals combined with 30 wavelength channels are successfully transmitted. (C) 2017 Optical Society of America</P>
Chang, Sun Hyok,Chung, Hwan Seok,Ryf, Roland,Fontaine, Nicolas K,Han, Changyo,Park, Kyung Jun,Kim, Kwangjoon,Lee, Jyung Chan,Lee, Jong Hyun,Kim, Byoung Yoon,Kim, Young Kie Optical Society of America 2015 Optics express Vol.23 No.6
<P>We propose all-fiber mode multiplexer composed of two consecutive LP?????? mode selective couplers that allows for the multiplexing of LP?????? mode and two-fold degenerate LP?????? modes. We demonstrate WDM transmission of 32 wavelength channels with 100 GHz spacing, each carrying 3 modes of 120 Gb/s polarization division multiplexed quadrature phase shifted keying (PDM-QPSK) signal, over 560 km of few-mode fiber (FMF). Long distance transmission is achieved by 6??6 multiple-input multiple-output digital signal processing and modal differential group delay compensated link of FMF. The all-fiber mode multiplexer has considerable potential to be used in mode- and wavelength-division multiplexed transmission.</P>
Comparison of conventional lateral cephalograms with corresponding CBCT radiographs
Chang-Seo Park,Jae-Kyu Park,Huijin Kim,Sang-Sun Han,Ho-Gul Jeong,Hyok Park 대한구강악안면방사선학회 2012 Imaging Science in Dentistry Vol.42 No.4
Purpose: This study was performed to assess the compatibility of cone beam computed tomography (CBCT) synthesized cephalograms with conventional cephalograms, and to find a method for obtaining normative values for threedimensional (3D) assessments. Materials and Methods: The sample group consisted of 10 adults with normal occlusion and well-balanced faces. They were imaged using conventional and CBCT cephalograms. The CBCT cephalograms were synthesized from the CBCT data using OnDemand 3D software. Twenty-one angular and 12 linear measurements from each imaging modality were compared and analyzed using paired-t test. Results: The linear measurements between the two imaging modalities were not statistically different (p¤0.05) except for the U1 to facial plane distance. The angular measurements between the two imaging modalities were not statistically different (p¤0.05) with the exception of the gonial angle, ANB difference, and facial convexity. Conclusion: Two-dimensional cephalometric norms could be readily used for 3D quantitative assessment, if corrected for lateral cephalogram distortion.
Comparison of conventional lateral cephalograms with corresponding CBCT radiographs
Park, Chang-Seo,Park, Jae-Kyu,Kim, Huijun,Han, Sang-Sun,Jeong, Ho-Gul,Park, Hyok Korean Academy of Oral and Maxillofacial Radiology 2012 Imaging Science in Dentistry Vol.42 No.4
Purpose: This study was performed to assess the compatibility of cone beam computed tomography (CBCT) synthesized cephalograms with conventional cephalograms, and to find a method for obtaining normative values for three-dimensional (3D) assessments. Materials and Methods: The sample group consisted of 10 adults with normal occlusion and well-balanced faces. They were imaged using conventional and CBCT cephalograms. The CBCT cephalograms were synthesized from the CBCT data using OnDemand 3D software. Twenty-one angular and 12 linear measurements from each imaging modality were compared and analyzed using paired-t test. Results: The linear measurements between the two imaging modalities were not statistically different (p>0.05) except for the U1 to facial plane distance. The angular measurements between the two imaging modalities were not statistically different (p>0.05) with the exception of the gonial angle, ANB difference, and facial convexity. Conclusion: Two-dimensional cephalometric norms could be readily used for 3D quantitative assessment, if corrected for lateral cephalogram distortion.