• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.17-17
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• 2003

목적： 생체 조직에서의 전기임피던스 분포는 생리적 기능에 대하여 풍부한 정보를 가지고 있다. 이러한 전기임피던스 분포는 전기임피던스단층촬영법(EIT)으로 구할 수 있으나 공간해상도가 열악하여 그 사용이 보편화되지 못하고 있다. 기존의 EIT의 한계점을 극복하기 위하여 EIT와 MRI 기술을 결합한 자기공명임피던스단층촬영법(MREIT： Magnetic Resonance Electrical Impedance Tomography)이 최근 제안되었다. MREIT는 영상복원 과정에서 x, y, z 3방향의 자속밀도 벡터를 필요로 하므로 MRI용 자석 내에서 물체를 3차원으로 회전하여 자속밀도 벡터를 구해야 한다. 이러한 3차원 회전은 MREIT가 실제 임상에 적용되는데 있어서 한계점으로 지적되고 있다. 본 논문에서는 물체 회전을 하지 않고 전기임피던스 분포를 얻을 수 있는 새로운 MREIT 방법을 제안하였다. 새로운 MREIT 방법의 원리에 대해서 소개하고 0.3T의 주자장세기를 갖는 연구용 MRI 시스템에서 얻은 MREIT영상을 소개하고자 한다.

• Journal of the Korean Magnetics Society
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• v.26 no.5
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• pp.168-172
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• 2016

The purpose of the optimal environment of the MRI room to measured luminance and illuminance of the MRI room and the monitor. University Hospital (n = 6) of the MRI (n = 10) in the luminance and illuminance Light Probe Xi Unfors (Unfors Instruments AB, Billdal, Sweden) was measured by using the. Black luminance level and white level of illuminance is repeated three times in the middle of the side of the monitor to obtain the mean and standard deviation using a t-test statistical processing was of significance test. Monitor luminance and black level in the average $1.78cd/m^2$, the standard deviation was $0.85cd/m^2$, white level average of $43.58cd/m^2$, the standard deviation of $13.19cd/m^2$. Illuminance of MRI room was the lowest value measured in accordance with the 30.5 lux, the maximum value is 601.3 lux, mean was measured by a variety of 177.86 lux. Luminance and illuminance of the MRI room and monitor is found to have statistically significant difference (p < .05). In conclusion, refer to the recommended standard of MRI and room monitor luminance and illuminance and to create an optimal environment.

• Investigative Magnetic Resonance Imaging
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• v.3 no.1
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• pp.53-59
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• 1999

Purpose : To evaluate the usefulness of functional MR imaging (fMRI) for language mapping and determination of language lateralization. Materials and Methods : Functional maps of the language area were obtained during word generation tasks and decision task in ten volunteers (7 right handed, 3 left-handed). MR examinations were performed at 1.5T scanner with EPI BOLD technique. Each task consisted of three resting periods and two activation periods with each period of 30 seconds. Total acquisition time was 162 sec. SPM program was used for the postprocessing of images. Statistical comparisons were performed by using t-statistics on a pixel-by- pixel basis after global normalization by ANCOVA. Activation areas were topographically analyzed (p>0.001) and activated pixels in each hemisphere were compared quantitatively by lateralization index. Results : Significant activation signals were demonstrated in 9 of 10 volunteers. Activation signals were found in the premotor and motor cortices, the inferior frontal, inferior parietal, and mid-temporal lobes during stimulation tasks. In the right handed seven volunteers, activation of language areas was lateralized to the left side. Verb generation task produced stronger activation in the language areas and higher value of lateralization index than noun generation task or decision task. Conclusion : fMRI could be a useful non-invasive method for language mapping and determination of language dominance.

• Investigative Magnetic Resonance Imaging
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• v.3 no.2
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• pp.179-187
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• 1999

Purpose : This paper introduces a computationally inexpensive context-dependent classification of multi-echo MRI with Bayes compound decision model. In order to produce accurate region segmentation especially in homogeneous area and along boundaries of the regions, we propose a classification method that uses contextual information of local enighborhood system in the image. Material and Methods : The performance of the context free classifier over a statistically heterogeneous image can be improved if the local stationary regions in the image are disassociated from each other through the mechanism of the interaction parameters defined at he local neighborhood level. In order to improve the classification accuracy, we use the contextual information which resolves ambiguities in the class assignment of a pattern based on the labels of the neighboring patterns in classifying the image. Since the data immediately surrounding a given pixel is intimately associated with this given pixel., then if the true nature of the surrounding pixel is known this can be used to extract the true nature of the given pixel. The proposed context-dependent compound decision model uses the compound Bayes decision rule with the contextual information. As for the contextual information in the model, the directional transition probabilities estimated from the local neighborhood system are used for the interaction parameters. Results : The context-dependent classification paradigm with compound Bayesian model for multi-echo MR images is developed. Compared to context free classification which does not consider contextual information, context-dependent classifier show improved classification results especially in homogeneous and along boundaries of regions since contextual information is used during the classification. Conclusion : We introduce a new paradigm to classify multi-echo MRI using clustering analysis and Bayesian compound decision model to improve the classification results.

• Progress in Medical Physics
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• v.10 no.1
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• pp.23-32
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• 1999

Combined MRI and Relaxogram approach was introduced as a very useful tool for fat study. The phantoms simulating homogeneous mixture of fat and non-fat environments were measured with spin echo pulse sequence on a 0.15 T whole body imager. From 45 scans, the Tl values were obtained by fitting the data to continuous distribution (CONTIN) of relaxation time. This relaxogram gives broad distributions of relaxation time, which are characterized by a number of peaks with characteristic T1 values. Two distinct peaks in relaxogram were observed and identified as signals from com oil and gelatin gel. This model system can be served as simulating the distribution of fat in muscle. Also the relative ratio of two components, which is proportional to the area under the peak, is estimated and compared to nominal values. Based on the good agreement between two predictions, the values from our proposed method agreed with nominal values within $\pm$7 % error. The effects of different concentration of contrast agent and different region of interest are presented. To optimize total scan times, the minimum required data points and so further reduction in total scan times are discussed.

• Investigative Magnetic Resonance Imaging
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• v.14 no.1
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• pp.21-30
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• 2010

Purpose : To examine the imaging findings of mucinous breast carcinoma and to evaluate the difference in these findings based on the histopathologic grade. Materials and Methods : We retrospectively analyzed the imaging features according to BI-RADS in 29 patients with surgically proven mucinous carcinoma. The histopathologic grade was classified as well-differentiated, moderately-differentiated and poorly-differentiated. Based on these criteria, the differences in imaging findings were statistically analyzed. Results : Mammography was available in 20 cases, which contained 17 mass lesions (85%) and 3 cases of normal findings. On ultrasonography (27 cases), mucinous carcinoma was observed as a mass with an oval shape (59.3%), a microlobulated margin (55.6%) or an inhomogeneous isoechogenicity (74.1%). On MRI (21 cases), mucinous carcinoma was commonly observed to have a lobular shape (76%), smooth margin (86%) or heterogeneous contrast-enhancement (61.9%). On the kinetic curve, there was a delayed wash-out pattern (52.3%). There were no significant differences in the imaging findings for each histopathologic grade except that a welldifferentiated tumor had an abrupt interface. Conclusion : A well-differentiated mucinous carcinoma tended to have an abrupt interface on ultrasonography, as compared with the moderately-differentiated one. Mucinous carcinoma showed a heterogeneous enhancement and a delayed washout kinetic curve pattern on dynamic MRI.

• Journal of Veterinary Clinics
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• v.30 no.4
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• pp.320-323
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• 2013

Spinal cord infarction is becoming recognized as an important cause of acute myelopathy in cats. Although the definitive diagnosis is confirmed through postmortem histopathologic examination, MR imaging features provide valuable informations for the diagnosis of spinal cord infarction. The aim of this report is to describe MR findings of acute spinal cord infarction in two cats and to evaluate usefulness of low field MRI (0.3Tesla) as a potential diagnostic tool of acute spinal cord infarction. A cat (unknown age, neutered male mixed breed cat) was referred one day after the acute onset of non-ambulatory spastic tetraparesis and the other cat (a 9-year-old, neutered female domestic short hair cat) was presented due to the acute onset of non-ambulatory paraparesis and one day later paraplegia. The lesions of the MR images were shown on the spinal cord parenchyma over C2 to C6 in case 1 and L2 to L5 in case 2. The MR images in these two cases were characterized by focal intramedullary lesions, mainly involving grey matter which were hyperintense T2 weighted and FLAIR images and hyperintense on DWI and hypointense on ADC map. The MR findings in both cases were highly suggestive of acute spinal cord infarctions, based upon previous reported small animal cases and human cases. In conclusion, based on MR features, together with the history and clinical examination findings, MRI modality can be used as an antemortem tool for the diagnosis of acute spinal cord infarction in cats.

• Journal of the Korean Society of Radiology
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• v.13 no.1
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• pp.55-63
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• 2019

It was reported that there were some cases in which signal was not inhibited but high signal appeared in cerebrospinal fluid on FLAIR(fluid attenuated inversion recovery) of MRI(Magnetic Resonance Imaging) in case a person inhales high-concentration oxygen. This study was to prepare basic database. We produced a phantom fixed with agar gel and by using it, obtained the images of the signals of normal saline into which oxygen was injected and normal saline diluted with contrast media by changing the TI(Inversion Time) of FLAIR technique and analyzed them. In the result of FLAIR technique of MRI using Philips Achieva MR 3.0T in Busan P Hospital, the SNR(Signal to Noise Ratio) of normal saline into which oxygen was injected was higher than the SNR of normal saline into which oxygen was not injected. However, it was not higher than the SNR of normal saline diluted with contrast media. In the TI 1,800ms, we could obtain the images which do not have the rise of the signal due to oxygen. In the CNR(Contrast to Noise Ratio) of normal saline into which oxygen was injected and normal saline diluted with contrast media as well, it was higher in the TI 1,800ms than in the TI 2,800ms that is mainly used clinically. It is thought that the result of this study could be basic database for studies on change of signal of cerebrospinal fluid as a result of injection of oxygen in FLAIR technique of MRI.

• Proceedings of the Korea Multimedia Society Conference
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• 2001.11a
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• pp.447-452
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• 2001

내용 기반 이미지 검색에서 질감정보는 이미지의 검색 속성으로 사용할 수 있는 중요한 정보를 가지고 있다. 본 논문에서는 검색의 이미지 속성으로서 질감 특징을 사용한다. 의료영상 MRI 중 특히 뇌영상의 검색에서 질감의 특징은 전체 이미지를 대상으로 한 전역 질감 특징 값과 종양이나 뇌출혈 부분 등 정상이 아닌 이상객체 부분의 지역 질감 특징 값을 3단계 웨이블릿 변환을 통해 추출하고 추출된 여러 개의 특징 중 검색 효율성을 높일 수 있는 특징만을 선별하여 검색에 이용하는 방안을 제안한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.295-295
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• 2004

본 연구에서는 한국인 20대 남자 50명(23$\pm$2세)과 여자 50명(20$\pm$1세)의 MR 뇌 영상을 KAIST 뇌과학 연구센터에 있는 37 MRI 기기로 획득하였고 Brain Voyager(B/V)를 이용하여 소뇌의 부피를 측정하고자 한다. 남자와 여자의 뇌의 구조가 부분적으로 차이가 있다는 것은 이미 밝혀진 사실이다 남자의 전체적인 brain volume이 약 10% 크다는 사실도 잘 알려져 있다. 그러므로 본 연구에서도 성별에 따라 소뇌의 부피의 차이가 있는지도 검증하고자 한다.(중략)