• Journal of ILASS-Korea
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• v.21 no.2
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• pp.88-94
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• 2016

In this study digital holographic microscopy system for measurements of 3-D velocities of particles in MR fluid is developed. Holograms are recorded using either a CCD camera with a double pulse laser or a high-speed camera with a continuous laser. To process recorded holograms, the correlation coefficient method is used for focal plane determination of particles. To remove noise and improve the quality of holograms and reconstructed images, a Wiener filter is adopted. The two-threshold and image segmentation methods are used for binary image transformation. For particle pairing, the match probability method is adopted. The developed system will be applied to measurements of the characteristics of unsteady 3-D particle velocities in MR fluids through the next stage of this study.

• Proceedings of the KSMRM Conference
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• 2002.11a
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• pp.138-138
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• 2002

To determine the accuracy of magnetic resonance (MR) imaging for discrimination between intervertebral disk extrusion versus protrusion. MR images of 80 patients who had MR imaging of the spine and confirmed as intervertebral disk extrusion or protrusion were retrospectively reviewed by an experienced musculoskeletal radiologist. A 1.5-T scanner was used. After review of medical records, MR findings of disk extrusion and protrusion were compared using the chi-square test. Intraobserver agreement for differentiation of disk extrusion from protrusion was calculated by using coefficient.

• The Journal of the Acoustical Society of Korea
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• v.17 no.8
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• pp.34-40
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• 1998

본 논문에서는 일반 X-ray 필름을 사용하는 기존 아날로그 의료 영상 진단 체계의 문제점들을 해결하기 위해 연구 개발된 포괄적인 영상관리 전송 시스템(PACS)에서의 효율 적인 영상 전송과 저장을 위해 병원에서 매일 다량으로 발생하는 의료 영상들 중 CT와 MR영상을 대상으로 하여 새로운 무손실 영상 압축 기법인 CRAC 압축 알고리즘을 설계하 였다. CRAC 압축 알고리즘에서는 CT와 MR 영상의 파일구조를 분석하여 런랭스 코딩에 적합하도록 데이터를 재배열하는 전처리 작업을 설계하였으며, 이를 CT와 MR 영상에 최적 화 시킨 개선된 런랭스 알고리즘으로 1차 압축시켜 그 결과를 산술 부호화 알고리즘과 결합 함으로써 압축효율을 향상시켰다. 이러한 CRAC 압축 알고리즘은 무손실 압축 기법으로, 의 료 영상을 압축한 수 손실 없이 원 영상을 그대로 복원할 수 있기 때문에 PACS에서의 CT, MR 영상의 판독을 위한 단기 저장시에 적합한 압축 알고리즘으로 CT와 MR 영상의 무손 실 압축에 대해 새로운 전처리 방법을 제시하였고, 기존 무손실 압축 방법들과 비교 분석한 결과 압축률이 2.1%∼5.9% 정도 향상되었다.

• Investigative Magnetic Resonance Imaging
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• v.5 no.2
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• pp.149-154
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• 2001

Purpose : Our aim was to evaluate the usefulness of fluid-attenuated inversion recovery (FLAIR) MR imaging for detection of acute subarachnoid hemorrhage (SAH) compared with unenhanced CT. Materials and methods ; We compared FLAIR MR images with unenhanced CT scans in 28 patients with acute SAH. Findings of SAH on CT and MR images were graded as 0 (absence), 1 (suspicious), 2 (definite) in the cerebral sulci, sylvian fissure, basal cistern, and cisterns of the posterior fossa. We also compared FLAIR MR images of 28 patients with those of 35 normal subjects, and then the sensitivity, specificity, and diagnostic accuracy of FLAIR MR image for detection of acute SAH were calculated. Results : FLAIR MR image was superior to CT in detecting SAH in the posterior fossa ($1.41{\pm}0.74{\;}vs{\;}0.78{\pm}0.80$; p<0.05) and cortical sulci ($1.11{\pm}0.80{\;}vs{\;}0.70{\pm}0.83$; p<0.05). There was no significant difference between FLAIR MR image and CT in detecting SAH in the basal cistern and sylvian fissure. The sensitivity, specificity, and diagnostic accuracy of FLAIR MR image for detection of SAH were 100% in all. Conclusion : FLAIR MR image is useful in detecting acute SAH, especially in patients with small amount of SAH or SAH in the posterior fossa.

• Investigative Magnetic Resonance Imaging
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• v.2 no.1
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• pp.67-72
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• 1998

The mapping of the spin-spin relaxation time T2 in pixel-by-pixel was suggested as a quantitative diagnostic tool in medicine. although the CPMG pulse sequence has been known to be the best pulse sequence for T2 measurement in physics NMR, the supplied pulse sequence by the manufacture of MRI system was able to obtain the maximum of 4 CPMG images. Eight or more images with different echo time TEs are required to construct a reliable T2 map, so that two or more acquisitions were required, which easily took more than 10 minutes. 4-echo CPMG imaging pulse sequence was modified to generate the maximum of 8 MR images with evenly spaced echo time TEs. In human MR imaging, since patients tend to move at least several pixels between the different acquisitions, 8-echo CPMG imaging sequence reduces the acquisition time and may remove any mis-regitration of each pixels signal for the fitting of T2. The resultant T2 maps using the theoretically simulated images and using the MR images of the human brain suggested that 8 echo CPMG sequence with short echo spacing such as 17-20 msec can give the reliable T2 map.

• Journal of Yeungnam Medical Science
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• v.15 no.2
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• pp.306-315
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• 1998

MR findings in nine patients(three female, six male) with neuro-Behcet's disease were retrospectively analyzed. NeuroBehcet's disease was diagnosed on the basis of typical clinical symptoms. Involved site, pattern, signal intensity, and contrast enhancement pattern on MRI were evaluated. In addition, follow up MR imaging was performed in four patients. The midbrain(7/9), internal capsule(7/9), pons(6/9), thalamus(6/9), basal ganglia (5/9), middle cerebella peduncle(4/9), medulla oblongata(2/9), and subcortical white matter(2/9) are involved on MRI. The size of lesions was 1cm to 3cm and their margin was ill-defined and patchy. Inhomogeneous high signal intensity on the T2-weighted images and low signal intensity on T1-weighted images was seen respectively. In four of nine cases, there was focal enhancement. On follow up MR imaging, improvement or recurrance of the lesions was found. Also in two cases of follow up cases, there was artophy in brainstem and(or) middle cerebellar peduncles. In conclusion, MR imaging with systemic clinical symptoms is useful for diagnosing neuro-Behcet's disease.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.11
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• pp.1096-1100
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• 2010

In this paper, we propose an automatic segmentation of the meniscus based on active shape model using interpolated shape information in MR images. First, the statistical shape model of meniscus is constructed to reflect the shape variation in the training set. Second, the generation technique of interpolated shape information by using the weight according to shape similarity is proposed to robustly segment the meniscus with large variation. Finally, the automatic meniscus segmentation is performed through the active shape model fitting. For the evaluation of our method, we performed the visual inspection, accuracy measure and processing time. For accuracy evaluation, the average distance difference between automatic segmentation and semi-automatic segmentation are calculated and visualized by color-coded mapping. Experimental results show that the average distance difference was $0.54{\pm}0.16mm$ in medial meniscus and $0.73{\pm}0.39mm$ in lateral meniscus. The total processing time was 4.87 seconds on average.

• Journal of Korean Neurosurgical Society
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• v.47 no.6
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• pp.437-441
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• 2010

Objective : The precise intra- vs. extradural localization of aneurysms involving the paraclinoid internal carotid artery is critical for the evaluation of patients being considered for aneurysm surgery. The purpose of this study was to investigate the clinical usefulness of T2-weighted threedimensional (3-D) fast spin-echo (FSE) magnetic resonance (MR) imaging in the evaluation of unruptured paraclinoid aneurysms. Methods : Twenty-eight patients with unruptured cerebral aneurysms in their paraclinoid regions were prospectively evaluated using a T2- weighted 3-D FSE MR imaging technique with oblique coronal sections. The MR images were assessed for the location of the cerebral aneurysm in relation to the dural ring and other surrounding anatomic compartments, and were also compared with the surgical or angiographic findings. Results : All 28 aneurysms were identified by T2-weighted 3D FSE MR imaging, which showed the precise anatomic relationships in regards to the subarachnoid space and the surrounding anatomic structures. Consequently, 13 aneurysms were determined to be intradural and the other 15 were deemed extradural as they were confined to the cavernous sinus. Of the 13 aneurysms with intradural locations, three superior hypophyseal artery aneurysms were found to be situated intradurally upon operation. Conclusion : High-resolution T2-weighted 3-D FSE MR imaging is capable of confirming whether a cerebral aneurysm at the paraclinoid region is intradural or extradural, because of the MR imaging's high spatial resolution. The images may help in identifying patients with intradural aneurysms who require treatment, and they also can provide valuable information in the treatment plan for paraclinoid aneurysms.

• Journal of Biomedical Engineering Research
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• v.25 no.1
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• pp.33-41
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• 2004

Accuracy of registration between images acquired from various medical image modalities is one of the critical issues in radiation treatment planing. In this study, a method of accuracy evaluation of image registration using a homemade brain phantom was investigated. Chamfer matching of CT-MR and CT-SPECT imaging was applied for the multimodal image registration. The accuracy of image correlation was evaluated by comparing the center points of the inserted targets of the phantom. The three dimensional root-mean-square translation deviations of the CT-MR and CT-SPECT registration were 2.1${\pm}$0.8 mm and 2.8${\pm}$1.4 mm, respectively. The rotational errors were ＜ 2$^{\circ}$ for the three orthogonal axes. These errors were within a reasonable margin compared with the previous phantom studies. A visual inspection of the superimposed CT-MR and CT- SPECT images also showed good matching results.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.99-99
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• 2003

To exhibit our clinical experience of diffusion-weighted (DW) MR imaging for various brain pathologies and to determine its role in characterizing brain pathologies in children. DW images in 177 children (M：F＝96：81, mean age, 4.7 years) with various brain pathologies were retrospectively collected over past 3 years. DW images (b value： 1000 s/mm) were reviewed along with corresponding apparent diffusion coefficient (ADC) maps. Brain pathologies included cystic or solid brain tumor (n = 55), cerebral infarct (n = 32), cerebritis with or without brain abscess (n = 21), metabolic or toxic brain disorder (n = 19), demyelinating disease (n = 16), hypoxic-ischemic encephalopathy (n = 16), intracerebral hemorrhage including traumatic brain lesion (n = 15), and posterior reversible leukoencephalopathy (n = 3). We reviewed whether DW images and ADCmaps contribute to further characterization of brain pathologies by defining a chronological age of lesions, the presence of cytotoxic edema in lesions, and the nature of cystic lesions.