• 방송공학회논문지
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• 제22권3호
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• pp.327-338
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• 2017

노출 합성은 두 장 이상의 서로 다른 노출 값을 갖는 좁은 동적 영역 영상을 합쳐 한 장의 넓은 동적 영역을 갖는 결과 영상을 생성하는 알고리듬이다. 본 논문은 블록기반의 지역적 특성을 고려한 노출 조정 기법과 개선된 채도 특성 요소를 이용해 가중치 맵을 생성하는 알고리듬을 제안한다. 제안하는 노출 조정 기법은 인간시각체계의 특성을 고려하여 입력 영상의 노출 값을 보정함으로써 노출 합성 결과 영상 내의 세밀한 부분을 효과적으로 보존한다. 개선된 채도 영상은 입력 영상 내의 포화 영역을 효과적으로 반영한 가중치맵을 생성한다. 본 논문은 기존의 대표적인 노출 합성 알고리듬과의 주관적 화질과 MEF-SSIM, 수행 시간 비교를 통해 제안하는 알고리듬의 우수성을 입증하였다.

• Molecules and Cells
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• 제26권2호
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• pp.113-120
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• 2008

Laser light microscopy enables observation of various simultaneously occurring events in living cells. This capability is important for monitoring the spatiotemporal patterns of the molecular interactions underlying such events. Two-photon excited fluorescence microscopy (two-photon microscopy), a technology based on multiphoton excitation, is one of the most promising candidates for such imaging. The advantages of two-photon microscopy have spurred wider adoption of the method, especially in neurological studies. Multicolor excitation capability, one advantage of two-photon microscopy, has enabled the quantification of spatiotemporal patterns of $[Ca^{2+}]_i$ and single episodes of fusion pore openings during exocytosis. In pancreatic acinar cells, we have successfully demonstrated the existence of "sequential compound exocytosis" for the first time, a process which has subsequently been identified in a wide variety of secretory cells including exocrine, endocrine and blood cells. Our newly developed method, the two-photon extracellular polar-tracer imaging-based quantification (TEPIQ) method, can be used for determining fusion pores and the diameters of vesicles smaller than the diffraction-limited resolution. Furthermore, two-photon microscopy has the demonstrated capability of obtaining cross-sectional images from deep layers within nearly intact tissue samples over long observation times with excellent spatial resolution. Recently, we have successfully observed a neuron located deeper than 0.9 mm from the brain cortex surface in an anesthetized mouse. This microscopy also enables the monitoring of long-term changes in neural or glial cells in a living mouse. This minireview describes both the current and anticipated capabilities of two-photon microscopy, based on a discussion of previous publications and recently obtained data.

• 대한영상의학회지
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• 제85권1호
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• pp.36-53
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• 2024

척추 수술의 빈도 증가와 더불어 radiography, CT, MRI 등의 의료 영상 촬영 건수도 증가하고 있으며, 이와 관련된 영상 판독의 중요성이 점점 더 커지고 있다. 본 논문에서는 척추 수술 후 발생 가능한 다양한 합병증을 이해하고, 이를 정확하고 효과적으로 진단하는 영상 검사의 중요 소견에 대해 다루고자 한다. 특히, 수술 후 초기 및 중장기 합병증을 구분하여, 각 시기별 특징적인 영상 소견을 자세히 설명한다. 척추 수술 후 초기 합병증으로는 부적절한 수술 기구 배치(instrument malposition), 장액종(seroma), 혈종(hematoma), 거짓수막류(pseudomeningocele), 수술 주변 감염(infection) 등이 있으며, 중장기 합병증으로는 수술 기구 주변의 골용해(osteolysis), 융합 실패(failure of fusion), 인접 분절 질환(adjacent segment disease), 경막외 섬유화 또는 흉터 조직(epidural fibrosis or scar) 형성 등이 포함된다. 이러한 척수 수술 후 발생하는 합병증 관련 영상 평가에 대한 정확한 이해는 척추 수술 후 합병증을 적시에 정확하게 진단하여 효과적인 환자 치료에 기여할 것이다.

• 센서학회지
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• 제21권4호
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• pp.270-275
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• 2012

In this study, we have developed a mobile-based visible/NIR(Near InfraRed) imaging equipment for the animal testing. This equipment can provide visible, NIR and merged image through the viewer program. Especially, merged image help researcher to understand visual messages at animal in-vivo test. Also, it is available to send real-time images through the smart phone. Researcher can communicate with another researcher who is a long distance away. Also, the equipment was made with portable small size to enable it to commercialize.

• Current Optics and Photonics
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• 제7권5호
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• pp.545-556
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• 2023

This paper introduces volume-sharing multi-aperture imaging (VMAI), a potential approach proposed for volume reduction in space-borne imagers, with the aim of achieving high-resolution ground spatial imagery using deep learning methods, with reduced volume compared to conventional approaches. As an intermediate step in the VMAI payload development, we present a phase-1 design targeting a 1-meter ground sampling distance (GSD) at 500 km altitude. Although its optical imaging capability does not surpass conventional approaches, it remains attractive for specific applications on small satellite platforms, particularly surveillance missions. The design integrates one wide-field and three narrow-field cameras with volume sharing and no optical interference. Capturing independent images from the four cameras, the payload emulates a large circular aperture to address diffraction and synthesizes high-resolution images using deep learning. Computational simulations validated the VMAI approach, while addressing challenges like lower signal-to-noise (SNR) values resulting from aperture segmentation. Future work will focus on further reducing the volume and refining SNR management.

• Investigative Magnetic Resonance Imaging
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• 제24권3호
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• pp.95-122
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• 2020

In this article, we evaluated the performance of radiofrequency (RF) coils in terms of the signal-to-noise ratio (S/N) and homogeneity of magnetic resonance images when used for ultrahigh-frequency (UHF) 7T magnetic resonance imaging (MRI). High-quality MRI can be obtained when these two basic requirements are met. However, because of the dielectric effect, 7T magnetic resonance imaging still produces essentially a non-uniform magnetic flux (|B₁|) density distribution. In general, heterogeneous and homogeneous RF coils may be designed using electromagnetic (EM) modeling. Heterogeneous coils, which are surface coils, are used in consideration of scalability in the |B₁| region with a high S/N as multichannel loop coils rather than selecting a single loop. Loop coils are considered state of the art for their simplicity yet effective |B₁|-field distribution and intensity. In addition, combining multiple loop coils allows phase arrays (PA). PA coils have gained great interest for use in receiving signals because of parallel imaging (PI) techniques, such as sensitivity encoding (SENSE) and generalized autocalibrating partial parallel acquisition (GRAPPA), which drastically reduce the acquisition time. With the introduction of a parallel transmit coil (pTx) system, a form of transceiver loop arrays has also been proposed. In this article, we discussed the applications and proposed designs of loop coils. RF homogeneous coils for volume imaging include Alderman-Grant resonators, birdcage coils, saddle coils, traveling wave coils, transmission line arrays, composite right-/left-handed arrays, and fusion coils. In this article, we also discussed the basic operation, design, and applications of these coils.

• Journal of Korean Neurosurgical Society
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• 제46권5호
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• pp.437-442
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• 2009

Objective : To characterize perioperative biomechanical changes after thoracic spine surgery. Methods : Fifty-eight patients underwent spinal instrumented fusions and simple laminectomies on the thoracolumbar spine from April 2003 to October 2008. Patients were allocated to three groups; namely, the laminectomy without fusion group (group I, n = 17), the thoracolumbar fusion group (group II, n = 27), and the thoracic spine fusion group (group III, n = 14). Sagittal (ADS) and coronal (ADC) angles for adjacent segments were measured from two disc spaces above lesions at the upper margins, to two disc spaces below lesions at the lower margins. Sagittal (TLS) and coronal (TLC) angles of the thoracolumbar junction were measured from the lower margin of the 11th thoracic vertebra body to the upper margin of the 2nd lumbar vertebra body on plane radiographs. Adjacent segment disc heights and disc signal changes were determined using simple spinal examinations and by magnetic resonance imaging. Clinical outcome indices were determined using a visual analog scale. Results : The three groups demonstrated statistically significant differences in terms of angle changes by ANOVA (p<0.05). All angles in group I showed significantly smaller angles changes than in groups II and III by Turkey's multiple comparison analysis. Coronal Cobb's angles of the thoracolumbar spine (TLC) were not significantly different in the three groups. Conclusion : Postoperative sagittal balance is expected to change in the adjacent and thoracolumbar areas after thoracic spine fusion. However, its prevalence seems to be higher when the thoracolumbar spine is included in instrumented fusion.

• Journal of Korean Neurosurgical Society
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• 제51권4호
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• pp.203-207
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• 2012

Objective: The purpose of this prospective study was to evaluate the efficacy and safety of screw fixation without bone fusion for unstable thoracolumbar and lumbar burst fracture. Methods: Nine patients younger than 40 years underwent screw fixation without bone fusion, following postural reduction using a soft roll at the involved vertebra, in cases of burst fracture. Their motor power was intact in spite of severe canal compromise. The surgical procedure included postural reduction for 3 days and screw fixations at one level above, one level below and at the fractured level itself. The patients underwent removal of implants 12 months after the initial operation, due to possibility of implant failure. Imaging and clinical findings, including canal encroachment, vertebral height, clinical outcome, and complications were analyzed. Results: Prior to surgery, the mean pain score (visual analogue scale) was 8.2, which decreased to 2.2 at 12 months after screw fixation. None of the patients complained of worsening of pain during 6 months after implant removal. All patients were graded as having excellent or good outcomes at 6 months after implant removal. The proportion of canal compromise at the fractured level improved from 55% to 35% at 12 months after surgery. The mean preoperative vertebral height loss was 45.3%, which improved to 20.6% at 6 months after implant removal. There were no neurological deficits related to neural injury. The improved vertebral height and canal compromise were maintained at 6 months after implant removal. Conclusion: Short segment pedicle screw fixation, including fractured level itself, without bone fusion following postural reduction can be an effective and safe operative technique in the management of selected young patients suffering from unstable burst fracture.

• 한국컴퓨터정보학회논문지
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• 제12권2호
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• pp.123-130
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• 2007

본 논문에서는 소동물 생체내 실험시 서로 다른 장비에서 획득된 영상의 융합 및 정합을 위한 방법을 제안한다. 마우스의 꼬리 정맥에 $[[^{18}F]FDG$를 주사하여 60분 섭취후 서로 다른 장비에서 동일한 위치의 영상을 획득하기 위하여 아크릴 재질의 소동물 가이드에 기준마크를 설정하고 microPET과 CT 영상을 획득하였다. MicroPET으로 획득된 리스트모드(list-mode) 데이터는 Fourier Rebinning(FRB) 방법을 사용하여 사이노그램(Sinogram)으로 변환 후 4 번의 반복횟수를 가지는 Ordered Subset Expectation Maximization(OSEM) 알고리즘으로 재구성하였다. MicroPET 영상획득후 PET/CT의 CT를 이용하여 CT영상을 획득하였다. MicroPET 영상에서 폐영역을 정확히 찾아내는 어려움이 있어. 해부학적 정보를 제공하는 CT 영상을 이용하여 폐 영역을 구분하였다. 영상 융합을 위한 불일치 부분을 해결하기 위하여 기준마크의 정보와 폐 영역의 정보를 이용하여 회전과 이동정보를 가지는 어파인 (affine) 변환 행렬 구하여 영상 정합에 사용하였다. 이 방법은 정량적 정확성과 영상 해석의 정확성을 개선할 것으로 기대된다.

• Asian Spine Journal
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• 제12권6호
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• pp.1017-1027
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• 2018

Study Design: This retrospective study was conducted including 18 patients who underwent posterior-only stabilization and fusion procedure for pseudoarthrosis in the ankylosed spine from October 2007 to May 2015. Purpose: This study aimed to describe the treatment outcomes in 18 patients with Andersson lesion (AL) who were managed using the posterior-only approach. Literature Review: AL is an unstable, localized, vertebral, or discovertebral lesion of the spine. It is observed in patients with ankylosing spondylitis. The exact etiology of this disorder remains unclear, and the treatment guidelines are not clearly described. Methods: We analyzed 18 patients with AL who were treated with posterior long segment spinal fusion without any anterior interbody grafting or posterior osteotomy. Pre- and postoperative radiography, computed tomography, and recent follow-up images were examined. The pre- and postoperative Visual Analog Scale score and the Oswestry Disability Index score were evaluated for all patients. Whiteclouds' outcome analysis criteria were applied at the follow-up. Moreover, at study completion, patient feedback was collected; all the patients were asked to provide their opinion regarding the surgery and were asked whether they would recommend this procedure to other patients and them self undergo the same procedure again if required. Results: The most common site was the thoracolumbar junction. The symptom duration ranged from 1 month to 10 years preoperatively. Most patients experienced fusion by the end of 1 year, and the fusion mass could be observed as early as 4 months. Pseudoarthrosis void of up to 2.5 cm was noted to be healed in subsequent imaging. In addition, clinically, the patients reported good symptomatic relief. No patient required revision surgery. Whiteclouds' outcome analysis score at the latest follow-up revealed goodto-excellent outcomes in all patients. Conclusions: ALs can be treated using the posterior-only approach with long segment fixation and posterior spinal fusion. This is a safe, simple, and quick procedure that prevents the morbidity of anterior surgery.