• 대한관절경학회지
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• 제13권2호
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• pp.161-164
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• 2009

외상성 슬관절 탈구 중 도수 정복되지 않는 경우는 매우 드물며 대개는 관혈적 정복술을 요한다. 본 증례는 도수 정복되지않는 슬관절 탈구에 대한 관절경적 치료 경험으로 자기공명 영상에서 정복을 방해하는 내측 인대 및 관절낭 구조물을 관찰하고 관절경 검사로 확인한 후 대퇴골 내측와가 완전히 관찰되고 관절이 정복 될 때까지 끼어있는 조직을 제거하였으며 인대 봉합이나 재건술은 시행하지 않았다. 술 후 약 4주간의 신전상태에서 고정 후 점진적인 관절운동 및 체중부하 보행을 허용하였다. 3년 추시 관찰에서 경도의 슬관절 불안정성은 있었으나 일상생활에 지장 없었으며 정상범위의 관절운동범위를 회복하였다.

• 한국임상수의학회지
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• 제26권5호
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• pp.490-494
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• 2009

A 2-year-old Maltese and a 5-month-old Yorkshire terrier were presented with ataxia. Tetraparesis was observed in a 9-year -old Yorkshire terrier. The localizations of the lesions suggested brain or cervical spinal cord by the neurological examination, and the following images was achieved: radiography, axial images of computed tomography (CT), reconstruction image of CT such as multi-planar reformation(MPR) and 3-dimensional(3D) reconstruction and magnetic resonance imaging (MRI). On radiography, the misalignment between atlas (C1) and axis (C2), absent dens of axis, and increased space between the dorsal arch of C1 and spinous process of C2 were found. The discontinuation between dens and body of C2 was identified through axial CT images, and the fragmentation of dens separated from axis was observed through MPR and 3D image in all case. The hyperintense lesions and the spinal cord compression on T2-weighted MR images were represented in a dog with tetraparesis, the others represented only spinal cord compression. Three dogs were diagnosed as atlantoaxial instability (AAI) by dens fracture of C2. The dog with tetraparesis was euthanized due to guarded prognosis. The others were recovered completely. It is difficult to differentiate dens fracture of C2 from abnormal dens such as agenesis and hypoplasia. We thought that CT is very useful to evaluate the dens of C2 and differentiate the causes of AAI, and the reconstruction images of CT such as MPR and 3D make the translation of the fragmented dens or axis of AAI more precisely evaluate.

• 대한의용생체공학회:의공학회지
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• 제32권3호
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• pp.245-250
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• 2011

Parallel imaging technique can provide several advantages for a multitude of MRI applications. Especially, in SENSE technique, sensitivity maps were always required in order to determine the reconstruction matrix, therefore, a number of difference approaches using sensitivity information from coils have been demonstrated to improve of image quality. Moreover, many filtering methods were proposed such as adaptive matched filter and nonlinear diffusion technique to optimize the suppression of background noise and to improve of image quality. In this study, we performed SENSE reconstruction using computer simulations to confirm the most suitable method for the feasibility of filtering effect and according to changing order of polynomial fit that were applied on variation of spatial resolution of sensitivity map. The image was obtained at 0.32T(Magfinder II, Genpia, Korea) MRI system using spin-echo pulse sequence(TR/TE = 500/20 ms, FOV = 300 mm, matrix = $128{\times}128$, thickness = 8 mm). For the simulation, obtained image was multiplied with four linear-array coil sensitivities which were formed of 2D-gaussian distribution and the image was complex white gaussian noise was added. Image processing was separated to apply two methods which were polynomial fitting and filtering according to spatial resolution of sensitivity map and each coil image was subsampled corresponding to reduction factor(r-factor) of 2 and 4. The results were compared to mean value of geomety factor(g-factor) and artifact power(AP) according to r-factor 2 and 4. Our results were represented while changing of spatial resolution of sensitivity map and r-factor, polynomial fit methods were represented the better results compared with general filtering methods. Although our result had limitation of computer simulation study instead of applying to experiment and coil geometric array such as linear, our method may be useful for determination of optimal sensitivity map in a linear coil array.

• 한국인지과학회:학술대회논문집
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• 한국인지과학회 2005년도 춘계학술대회
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• pp.151-153
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• 2005

We investigated the brain substrate of repetition priming on the implicit memory taskusing low-resolution electromagnetic tomography (LORETA) with high-density 128 channel EEG and individual MRI as a realistic head model. Thirteen right-handed, healthy subjects performed a word/nonword discrimination task, in which the words and nonwords were presented visually,and some of the words appeared twice with a lag of one or five items. All of the subjects exhibited repetition priming with respect to the behavioral data, in which a faster reaction time was observed to the repeated word (old word) than to the first presentation of the word (new word). The old words elicited more positive-going potentials than the new words, beginning at 200 ms and lasting until 500 ms post-stimulus. We conducted source reconstruction using LORETA at a latency of 400 ms with the peak mean global field potentials and used statistical parametric mapping for the statistical analysis. We found that the source elicited by the old words exhibited a statistically significant current density reduction in the left inferior frontal gyrus. This is the first study to investigate the generators of repetition priming using voxel-by-voxel statistical mapping of the current density with individual MRI and high-density EEG.

• Investigative Magnetic Resonance Imaging
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• 제20권4호
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• pp.215-223
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• 2016

Purpose: The management of metal-induced field inhomogeneities is one of the major concerns of distortion-free magnetic resonance images near metallic implants. The recently proposed method called "Slice Encoding for Metal Artifact Correction (SEMAC)" is an effective spin echo pulse sequence of magnetic resonance imaging (MRI) near metallic implants. However, as SEMAC uses the noisy resolved data elements, SEMAC images can have a major problem for improving the signal-to-noise ratio (SNR) without compromising the correction of metal artifacts. To address that issue, this paper presents a novel reconstruction technique for providing an improvement of the SNR in SEMAC images without sacrificing the correction of metal artifacts. Materials and Methods: Low-rank approximation in each coil image is first performed to suppress the noise in the slice direction, because the signal is highly correlated between SEMAC-encoded slices. Secondly, SEMAC images are reconstructed by the best linear unbiased estimator (BLUE), also known as Gauss-Markov or weighted least squares. Noise levels and correlation in the receiver channels are considered for the sake of SNR optimization. To this end, since distorted excitation profiles are sparse, $l_1$ minimization performs well in recovering the sparse distorted excitation profiles and the sparse modeling of our approach offers excellent correction of metal-induced distortions. Results: Three images reconstructed using SEMAC, SEMAC with the conventional two-step noise reduction, and the proposed image denoising for metal MRI exploiting sparsity and low rank approximation algorithm were compared. The proposed algorithm outperformed two methods and produced 119% SNR better than SEMAC and 89% SNR better than SEMAC with the conventional two-step noise reduction. Conclusion: We successfully demonstrated that the proposed, novel algorithm for SEMAC, if compared with conventional de-noising methods, substantially improves SNR and reduces artifacts.

• 핵의학기술
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• 제22권1호
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• pp.43-45
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• 2018

NEMA IEC body phantom으로 PET/MR 스캐너를 이용해 MR 영상 기반의 감쇠보정 된 PET 영상을 얻고, 반복재구성 기반의 점 확산 함수(PSF)에 적용 유무에 따라 PET 영상을 Contrast recovery 와 SNR 의 평가 인자를 적용해 평가하였다. 또한, 동일한 재구성 방법에 따라 본원의 내원한 환자의 영상도 평가하였다. 데이터는 임상환자 와 팬텀 실험 모두 PSF를 적용해 재구성한 영상이 모두 영상의 질이 향상됨을 확인하였다. MR 기반으로 얻어진 PET 영상 평가가 추후에도 계속해서 필요하다고 사료된다.

• 인지과학
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• 제22권4호
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• pp.347-364
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• 2011

본 논문에서는 fMRI를 사용하여 뇌신경 반응을 측정한 후, 자극으로 주어진 $10{\times}10$ 크기의 이진 영상을 사전 정보 없이 복원하기 위해 비음수 행렬 분해를 이용한 자동화된 영상 기저 추출 방법을 제안한다. 영상 기저란 영상을 표현하는 기본 단위로, 기존 연구에서는 사전에 정의된 $1{\times}1$, $2{\times}1$, $1{\times}2$, $2{\times}2$의 크기를 갖는 총 361개의 영상 기저에 반응하는 뇌 신호를 분석하여 기저 영상으로 복원하고, 모든 기저에 대한 복원 결과를 선형 결합하여 최종복원 영상을 획득하였다. 사람이 사전에 정의한 영상 기저를 필요로 하는 기존 연구와는 달리, 본 연구에서는 비음수 행렬 분해를 기반으로 학습 데이터로 주어진 이진 영상을 가장 잘 표현하는 영상 기저를 자동 추출하였다. 자동으로 추출된 영상 기저를 사용하여 이진 영상을 복원한 결과, 기존 연구 방법보다 개선된 복원 정확도를 보였다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.506-508
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• 2002

As an advancement of medical imaging modalities and analyzing software with multi-function, active researches to acquire high contrast and high resolution image being done. In recently, development of medical imaging modalities like as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) is aiming to display anatomical structure more accuracy and faster. Thus, one of the important areas in CT today is the use of CT scanner for the quantitative evaluation of 3-D reconstruction images from 2-D tomographic images. In CT system, the effective slice thickness and the quality of 3-D reconstructed image will be influenced by imaging acquisition parameters (e.g. pitch and scan mode). In diagnosis and surgical planning, the accurate distance measurements of 3-D anatomical structures play an important role and the accuracy of distance measurements will depend on the acquisition parameters such as slice thickness, pitch, and scan mode. The skull phantom was scanned with SDCT for various acquisition parameters and acquisition slice thicknesses were 3 and 5 mm, and reconstruction intervals were 1, 2, and 3 mm to each pitch. 3-D visualizations and distance measurements were performed with PC based 3-D rendering and analyzing software. Results showed that the image quality and the measurement accuracy of 3-D SDCT images are independent to the reconstruction intervals and pitches.

• 대한관절경학회지
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• 제10권2호
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• pp.187-191
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• 2006

전방 십자 인대 재건술 후 대퇴 간섭 나사가 후방 구획으로 전위된 예는 극히 드물게 보고되고 있다. 이는 대개의 경우 기계적인 증상을 일으키므로 수술적인 제거술이 요구된다. 그러나 나사를 관절경적으로 제거하는 것은 기술적으로 어려운 술기이며 특히, 나사가 후방 구획으로 이동되었으나 전방 십자 인대가 잘 유지되어 있는 경우, 혹은 나사 주위가 막으로 둘러 쌓여 있을 경우 관절경적 제거는 더욱 어렵다. 저자들은 전방 십자 인대 재건술 후 재건 인대가 생착된 11년 후에 대퇴 간섭 나사가 후방 구획으로 전위된 1예를 보고하고자 한다. 저자들은 경우 가장 힘든 후방 구획에 위치한 전위된 대퇴 간섭 나사를 전방십자인대 이식건의 손상 없이 후방 경격막 도달법을 이용한 관절경적으로 제거하여 좋은 결과를 얻었기에 문헌고찰과 함께 보고하고자 한다.

• 대한관절경학회지
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• 제12권3호
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• pp.198-204
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• 2008

목적: 본 연구의 목적은 동종건을 통한 단일다발 및 이중다발 전방십자인대 재건술의 수술 결과를 관절경적, 방사선학적, 임상적으로 비교 분석하여 이중 다발 재건술의 장점과 문제점을 분석하여 향후 개선점을 도출하는데 있다. 대상 및 방법: 동종건을 이용한 전방십자인대 재건술을 시행 받은 환자들 중 최소 1년 이상의 관찰이 가능하였던 27명의 환자를 대상으로 전후방 전위 정도, Pivot shift 검사, 사두박근 및 슬괵근의 등속성 최대우력, Tegner 활동 점수, IKDC 주관적 점수, 그리고 Lysholm 슬관절 점수를 측정하였고, 술후 1년에서 2년사이에 자기공명영상 및 2차 관절경 검사를 시행하였다. 결과: Lysholm 슬관절 검사는 평균값이 단일다발에서 $87.23{\pm}11.50$, 이중다발에서 $93.36{\pm}9.92$ (p=0.033), IKDC 주관적 검사는 단일다발에서 $80.55{\pm}12.96$, 이중다발에서 $85.91{\pm}13.78$ (p=0.105), Tegner 활동 검사는 단일다발에서 $5.23{\pm}1.36$, 이중다발에서 $6.64{\pm}2.21$ (p=0.048)이었다. Pivot shift검사상 단일다발에서 Grade 0 이 10예, 1+가 1예, 2+가 2예 있었으며, 이중다발에서 Grade 0이 13예, 2+가 1예 있었다. 60도 및 180도에서의 굴곡 및 신전 결손율은 단일다발과 이중다발사이에 통계학적으로 유의한 차이가 나타나지 않았다. 2차관절경 검사 시행상 단일다발에서 우수(excellent)가 6례, 그리고 보통(fair)이 7례 있었다. 이중다발에서는 전내측 다발은 우수가 13예, 보통이 1예, 후외측 다발에서는 우수가 4예, 보통이 9예, 불량이 1예로 후외측 다발이 전내측 다발보다 손상이 많은 것으로 나타났다. 결론: 이중다발 재건술은 젊고 활동적인 환자에게서 좋은 결과를 기대할 수 있는 수술적 방법이나 후외측 다발의 손상을 줄일 수 있는 수술 및 재활 방법의 개선을 요한다.