• Journal of the Korean Society of Radiology
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• v.9 no.5
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• pp.301-306
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• 2015

X-ray can be applied to obtain a projection image of an object. It is not easy to obtain an high quality image for the object composed of low and high density materials. For the object with large difference in density, it is possible to realize high contrast image using images of low and high tube voltages and image processing. The plastic and metalic parts of the electronic components can be imaged by the dual energy technique which use low and high tube voltages and by processing pixel-by-pixel using visual C++. The contrast-enhanced image can be used to detect and observe defects within the electronic components.

• Korean Journal of Digital Imaging in Medicine
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• v.9 no.1
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• pp.7-15
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• 2007

This study aim to investigate image characteristics due to focus-grid and head phantom decentering from the armorphos silicon thin film transistor detector the fixed focus-grid is applied, wish to propose right use method of digital medical equipment. Acquired image according to focus-grid and head phantom position decentering using head phantom on armorphos silicon thin film transistor detector the fixed focus-grid is applied. acquired image evaluate pixel value, histogram, plot profile, surface plot using NIB (Image J) image analysis program and compared decentering image with standard image. Mean value and standard deviation value of focus-grid lateral decentering and duplex decentering of focus-grid and head phantom decreased by ratio, consequently increase of horizontality, diagonal decentering. also, deteriorated contrast of image because frequency of high pixel value decreases fairly. according increases decentering, image distortion phenomenon was increase, by next time, pixel mean value of head phantom decentering was no big change but horizontality, diagonal, mean value and standard deviation value of pixel decreased by ratio. Even if increase pixel noise of image because wide latitude and post processing ability of digital detector, radiotechnologist can not recognize. Therefore, radiotechnologist must recognize correctly the photographing factors which increases pixel noise on the grid system installation digital detector and should exam.

• Journal of the Korean Society of Radiology
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• v.9 no.5
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• pp.307-314
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• 2015

This study was conducted in reducing the involuntary motion artifacts because of lungs and heart movements as well as the aliasing artifacts generated during the use of the reduced-FOV EPI technique while performing breast MRI. Performed on a total of 38 obesity female subjects who visited the clinic for pre-examination before surgery within the period from August 1 to November 30, 2014. The 3.0T MRI scanner equipped with a breast scanning coil. Qualitative and quantitative analyses were each used for the evaluation of the acquired images while an Paired T-test and Wilcoxon rank test were performed to check the statistical significance. The variation ratio rose by 15.69% with the additional application of a pre-saturation pulse in the lesion, by 13.72% near the lesion, and 20.63% in the fat and the contrast-to-noise ratio rose by 10.58% in and near the lesion and by 12.03% in the lesion and fat, respectively. there were increases of 22.05% and 21.42% at 0 and 1000 respectively in qulitative evaluation and growth of 16.10% in apparent diffusion coefficient. it showed a statistically significant result(p<0.05) in signal to noise ratio, contrast to noise ratio, diffusion slope coefficient and apparent diffusion coefficient. The involuntary movements artifacts that occur in the phase encoding direction and the aliasing artifacts are considered to be reduced to obtain the best image in the additional use of the pre-saturation pulse as DWI is acquired.

• Investigative Magnetic Resonance Imaging
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• v.14 no.1
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• pp.31-40
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• 2010

Purpose : To compare the relative values of various fast breath-hold imaging sequences for superparamagnetic iron-oxide (SPIO)-enhanced hepatic MRI for the assessment of solid focal lesions with a 3T MRI unit. Materials and Methods : 102 consecutive patients with one or more solid malignant hepatic lesions were evaluated by spoiled gradient echo (GRE) sequences with three different echo times (2.4 msec [GRE_2.4], 5.8 msec [GRE_5.8], and 10 msec [GRE_10]) for $T2^*$-weighted imaging in addition to T2-weighted turbo spin echo (TSE) sequence following intravenous SPIO injection. Image qualities of the hepatic contour, vascular landmarks and artifacts were rated by two independent readers using a four-point scale. For quantitative analysis, contrast-to-noise ratio (CNR) was measured in 170 solid focal lesions larger than 1 cm (107 hepatocellular carcinomas, nine cholangiocarcinomas and 54 metastases). Results : GRE_5.8 showed the highest mean points for hepatic contour, vascular anatomy and imaging artifact presence among all of the subjected sequences (p<0.001) and was comparable (p=0.414) with GRE_10 with regard to lesion conspicuity. The mean CNRs were significantly higher (p<0.001) in the following order: GRE_10 ($24.4{\pm}14.5$), GRE_5.8 ($14.8{\pm}9.4$), TSE ($9.7{\pm}6.3$), and GRE_2.4 ($7.9{\pm}6.4$). The mean CNRs of CCCs and metastases were higher than those of HCCs for all imaging sequences (p<0.05). Conclusion : Regarding overall performances, GRE using a moderate echo time of 5.8 msec can provide the most reliable data among the various fast breath-hold SPIO-enhanced hepatic MRI sequences at 3T unit despite the lower CNR of GRE_5.8 compared to that of GRE_10.

• Proceedings of the KSMRM Conference
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• 1999.04a
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• pp.81-86
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• 1999

MR은 높은 조직 대조도와 축상, 시상 및 관상면 등의 multiplanar capability의 커다란 장점을 갖고 있어 뇌 신경계질환 진단에 필수적이며, 특히 ionizing radiation이 아니고 요오드계 IV 조영제를 사용하지 않는다는 점이 CT에 비해 더욱 유리하다. 소아에서의 뇌신경계 질환은 선천성 기형이나 대사성 질환이 많은 등 성인과는 다른 질환분포를 보인다. 따라서 성인에서와 같은 protocol을 그대로 적용하였을 때 좋은 질의 영상을 얻기 힘든 경우가 있으며, 연령 또는 질환에 따라 촬영기법도 다양하게 하여야 하므로 routine protocol을 정하지 않고 매 환아 마다 적절한 기법을 선택하고 있다. 또한 움직임을 억제하기 위하여 진정 (sedation)이 필요한 예가 대부분이며 적절한 잠재우기는 좋은 질의 영상을 얻기 위해 필수적이므로 이에 대한 지식을 필요로 한다.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.18-18
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• 2003

목적： MRI 시스템에서 얻어지는 Data는 TR(Repetition Time)과 TE(Echo Time)에 따라서 신호 대잡음비(SNR), 조직들간의 대조도(Contrast), Artifact 및 촬영시간이 결정된다. 이 연구에서는 TR/TE를 줄이는 기법을 이용한 Radial Imaging 영상기법을 제시하고자 한다. 대상 및 방법： 일반적인 Radial Imaging 기법에 HASTE 기법과 Non-uniform sampling 기법의 특징을 이용하여 구현하였으며, TR/TE를 줄일 수 있었으며 얻어진 K-space Data는 가변주파수 역 Fourier Transform을 이용하여 Projection Data를 재구성한 후 Back Projection 기법을 이용하여 최종 영상을 재구성한다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10d
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• pp.217-219
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• 2002

본 연구에서는 초음파 영상에서 간실질의 에코 명도분포를 분석하여 정량화 지방간 진단 파라미터인 규준화 에코 명도값을 추출하여 지방간의 진행 정도와의 상관성을 연구하였다. 임상 지방간지수와 본 연구의 규준화 에코 명도 값과의 선형 상관 계수를 구하였다. 신장대조 및 간문맥구조에서 추출한 규준화 에코 명도를 계산하여 비교한 결과, 임상 지방간지수와 높은 상관성을 보임을 알 수 있었고, 지방간 진단의 보조자료로 유용함을 확인하였다. 계산된 지방간지수와 상대명도의 선형상관계수는 0.69~0.79이다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.158-160
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• 2011

본 논문은 OLED 디스플레이를 위한 저전력 화질 개선 기법을 제안한다. 제안 기법에서는 영상의 대조비를 높이고, OLED 디스플레이 소비전력을 감소하는 기법을 선형 함수에 기반하여 유도하며, 지역적 특성을 고려하여 각 지역마다 서로 다른 매핑 함수를 적용하는 적응적 변환 함수를 구한다. 컴퓨터 모의실험을 통해 제안하는 기법이 전력 소비를 줄이는 동시에 영상의 화질을 개선하는 것을 확인한다.

• Journal of the Korean Society of Radiology
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• v.82 no.5
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• pp.1083-1102
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• 2021

Uterine cervical cancer is a common gynecological cancer prevalent in Korea. Early detection, precise diagnosis, and appropriate treatment can affect its prognosis. Imaging approaches play an important role in staging, treatment planning, and follow-up. MRI specifically provides the advantage of assessing tumor size and disease severity with high soft tissue contrast. The revised version of the International Federation of Gynecology and Obstetrics (FIGO) staging system has been introduced in 2018, which incorporates subdivided primary tumor size and lymph node metastasis. In this review, the staging of uterine cervical cancer based on previous studies, the recently revised FIGO staging, and various post-treatment images are primarily described using MRI.

• Journal of the Korean Society of Radiology
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• v.81 no.5
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• pp.1184-1193
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• 2020

Purpose This study was performed to evaluate the relationship between callosal microbleeds and anoxic brain injury. Materials and Methods Twenty-seven patients with anoxic brain injuries were analyzed and retrospectively compared to the control group of patients without a history of anoxic brain injury using Fisher's exact test regarding comorbidities and cerebral microbleeds. The patient group was subdivided according to the presence of callosal microbleeds. Fisher's exact test was used to compare the presence of typical MRI findings of anoxic brain injury, use of cardiopulmonary resuscitation, and prognosis. The Mann-Whitney U test was used to compare the interval between the occurrence of anoxic brain injury to MRI acquisition. Results The prevalence of cerebral microbleeds in the patient group was 29.6%, which was significantly higher than that in the control group at 3.7% (p = 0.012). All cerebral microbleeds in the patient group were in the corpus callosum. Compared with the callosal microbleed-absent group, the callosal microbleed-present group showed a tendency of good prognosis (6/8 vs. 11/19), fewer typical MRI findings of anoxic brain injury (2/8 vs. 10/19), and more cardiopulmonary resuscitation (6/8 vs. 12/19), although these differences did not reach statistical significance (p = 0.35, p = 0.19, and p = 0.45, respectively). Conclusion Callosal microbleeds may be an adjunctive MRI marker for anoxic brain injury.