• 대한수의학회지
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• 제44권2호
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• pp.311-315
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• 2004

The detection of lymph node metastasis is an important step in tumor staging and is significant for therapy planning. It has been challenged to yield an appropriate image with diagnostic methods such as Magnetic Resonance (MR) and Computed Tomography (CT). Though CT has been used widely and accessed easily to show internal organs, it can hardly provide difference between lymph node and adjacent vessel or fat tissue. It has been well established that MR can reveal the subtle discrepancy within soft tissue. This study investigated the suitability of MR lymph node imaging without contrast enhancement by comparison of T1-weighted image (T1WI) and T2- weighted image (T2WI) in ten normal rabbits. According to the pulse sequence optimized from preliminary study, T1-weighted spin-echo (repetition time/echo time=400/12 ms) and T-2 weighted fast spin-echo (repetition time/echo time=3500/84 ms) images covering the hind limbs and pelvic region were acquired at 1.5 T. Two radiologists scrupulously evaluated the MR images in consensus. And signal intensity of lymph nodes was compared with that of adjacent fat. Statistical analysis showed that T1-weighted coronal image visualized the lymph nodes (iliac, superficial inguinal and popliteal lymph nodes) quickly and consistently rather than T2-weighted one. Conclusively, T1WI for evaluation of lymph nodes is moderately better than T2WI and appears to have potential for quick and sufficient mapping of the lymph nodes. In addition, this normal MR image of lymph nodes could be applied to further study for the evaluation of lymphatic system in abscess and tumor bearing animal model.

• 대한디지털의료영상학회논문지
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• 제15권2호
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• pp.55-61
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• 2013

The purpose of this study is to evaluate image blurring according to variation of the ETL and propose the clinically appropriate ETL range. SIEMENS MAGNETOM Skyra 3.0T and 20 channel head coil were used for the study. MRI phantom was kept the lines horizontally to three direction(X,Y,Z) of the coil and T1, T2 weighted images that used the fast spin echo technique acquired. The ETL with increase of 10 was applied from 10 to 80. In addition, the ETL with increase of 1 was applied in the interval statistically significant differences occurred. And T1, T2 weighted images that used the conventional spin echo technique acquired to compare image blurring of the images that used the fast spin echo technique. The slope of lattice in the images was measured using Image J 1.47v program to evaluate image blurring. And image blurring was determined by the degree of the slope. The statistical significance of both techniques was evaluated by the Kruskal-Wallis test of the SPSS 17.0v. And the correlation of the ETL and image blurring was evaluated quantitatively by regression analysis. The slope of the T1, T2 weighted images that used fast spin echo technique decreased as contrasted with conventional spin echo technique. In the result of the Kruskal-Wallis test, the T1, T2 weighted images that used fast spin echo technique made a significant difference with conventional spin echo technique. Particularly, in the Tomhane' T2 test, the T1, T2 weighted images made a significant difference from ETL 22 and 31 respectively. In the result of the regression analysis, the R-squared of the T1, T2 weighted images are 0.762 and 0.793. It is difficult to apply the long ETL in the T1 weighted image caused by the short TR and multi-slices study. Therefore, clinical impact according to variation of the ETL is very slight in the T1 weighted images. But the application of the proper ETL is demanded in T2 weighted images using the fast spin echo technique in order to prevent image blurring.

• Journal of Magnetics
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• 제17권2호
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• pp.153-157
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• 2012

This study evaluated the ability of Diffusion-Weight Image (DWI), which is one of pulse sequences used in MRI based on the T2 weighted images, to detect samples placed within phantoms according to their size. Two identically sized phantoms, which could be inserted into the breast coil bilaterally, were prepared. Five samples with different sizes were placed in the phantoms, and the T2 weighted images and DWI were obtained. The Breast 2 channel coil of SIEMENS MAGNETOM Avanto 1.5 Tesla equipment was used for the experiments. 2D T2 weighted images were obtained using the following parameters: TR/TE = 6700/74 msec, Thickness/gap = 5/1 mm, Inversion Time (TI) = 130 ms, and matrix = $224{\times}448$. The parameters of DWI were that TR/TE = 8100/90 msec, Thickness/gap = 5/1 mm, matrix = $128{\times}128$, Inversion Time = 185 ms, and b-value = 0, 100, 300, 600, 1000 s/mm. The ratio of the sample volume on DWI compared to the T2 weighted images, which show excellent ability to detect lesions on MR images, was presented as the mean b-value. The measured b-value of the samples was obtained: 0.5${\times}$0.5 cm=0.33/0.34 square ${\times}$ cm (103%), 1${\times}$1 cm=1.28/1.25 square ${\times}$ cm (102.4%), 1.5${\times}$1.5 cm = 2.28/2.67 square ${\times}$ cm (85.39%), 2${\times}$2 cm=3.56/4.08 square ${\times}$ cm (87.25%), and 2.5${\times}$2.5 cm=7.53/8.77 square ${\times}$ cm (85.86%). In conclusion, the detection ability by the size of a sample was measured to be over 85% compared to T2 weighted image, but the detection ability of DWI was relatively lower than that of T2 weighted image.

• 대한디지털의료영상학회논문지
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• 제14권1호
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• pp.21-29
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• 2012

The purpose of this study is to evaluate the mutual relations by measuring SNR from T2 weighted image and ADC values on the basis of the stiffness values from liver tissues. This study was conducted that total 37 people(23 of males and 11 of females) were taken the liver MRI examination and average age was $54.5{\pm}12.7$ years old. The equipment was MAGNETOM Skyra 3.0T (SIEMENS, Erlangen, Germany) and 32 channel body-array coil. The examination were conducted with HASTE T2 weighted image by axial plane, Spin-echo EPI (echo planner image) DWI (b-value = 800) and Magnetic resonance elastography. The ROIs (region of interest: 200-300 $mm^2$) were established on the basis of the first axial stiffness image corresponded 95% confidence interval from axial stiffness image and then were measured values. After drawing the grid lines, signals were measured SNR from T2 weighted image and ADC values on the same locations that were analysed other 3 planes respectively. The results were showed correlation (0.057) that were increased to SNR from T2 weighted image by increasing stiffness value that no significant difference statistically p = 0.003. Other results were showed correlations (-0.301) that were decreased to ADC values by increasing stiffness values that no significant difference statistically p = 0.088. In the 3.0T equipment, the results may be error in much the same fashion as the 1.5T from ADC values by evaluation of fibrosis stage. However, Magnetic resonance elastography would be useful method that is used to diagnose exactly liver fibrosis stages in the 3.0T.

• Investigative Magnetic Resonance Imaging
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• 제13권1호
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• pp.9-14
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• 2009

T1, T2강조영상, FLAIR (fluid attenuated inversion recovery) 영상기법은 뇌 MRI의 가장 기본적인 영상기법들이다. T1강조영상은 짧은 TR과 짧은 TE를 이용한 스핀에코 기법으로서 조직의 T1이완시간의 차이를 신호 차이로 반영하는 기법이다. 짧은 TR을 사용하면 조직 간에 종축 자기화의 회복 정도가 크게 차이나게 되며 이를 신호에 반영하는 것이다. T2강조영상은 긴 TR과 긴 TE를 이용한 스핀에코 기법으로서 조직의 T2이완시간의 차이를 신호 차이로 반영하는 기법이다. 긴 TE을 사용하면 조직 간에 횡축 자기화의 붕괴가 크게 차이나게 되며 이를 신호에 반영하는 것이다. FLAIR는 180도 반전펄스를 먼저 가하는 반전회복 (inversion recovery) 기법의 일종으로서 뇌척수액의 신호를 억제하기 위하여 2500 msec 정도의 반전시간을 적용한다.

• 한국방사선학회논문지
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• 제18권1호
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• pp.37-44
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• 2024

MR은 우수한 연조직 대비와 기능 정보를 보여줄 수 있지만, 방사선치료에서 정확한 선량 계산을 위해서는 CT영상의 전자밀도 정보가 필요하다. 방사선치료(Radiotherapy) 계획 워크플로우에서 MR영상과 CT영상을 융합하기 위해 환자는 일반적으로 MR과 CT영상 방식 모두에서 스캔된다. 최근에 딥러닝기술 덕분에 MR영상에서 딥러닝 기반의 CT영상 생성이 가능해졌다. 이로 인해 CT 스캔 작업을 할 필요가 없게 된다. 본 연구에서는 MR영상으로부터 CycleGan 딥러닝 기반 CT영상생성을 구현했다. T1가중이나 T2가중 중에 한 가지 또는 그 둘다의 MR영상을 가지고 합습한 3가지의 인공지능 CT생성기를 만들었다. 결과에서 우리는 T1가중 MR 영상 기반으로 학습한 생성기가 T1가중 MR영상이 입력될 때 다른 CT생성기보다 더 나은 결과를 생성할 수 있음을 발견했다. 반면, T2가중 MR영상 기반 CT생성기는 T2가중 MR영상을 입력 받을 때, 다른 시퀀스기반 CT생성기보다 더 나은 결과를 생성할 수 있습니다. MR영상을 기반으로 한 CT생성기는 곧 임상현장에 적용될 수 있는 기술이다. 특정 시퀀스 MR영상으로 학습한 머신러닝 CT생성기는 다른 시퀀스 MR영상으로 학습한 생성기보다 더 그 특정 시퀀스와 같은 MR영상을 입력받을 때 더 나은 CT영상을 생성할 수 있음을 보여주었다.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제15권9호
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• pp.700-704
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• 2009

본 논문은 영상보정 및 다단계 정합을 통한 전립선의 MR 영상과 병리 영상 간의 융합방법을 제안한다. 제안 방법은 영상보정, 강체 정합, 비강체 정합, 영상융합의 네 단계로 이루어진다. 첫째, 영상보정 단계에서 T2 MR 강조 영상의 출혈 부위의 자기값을 T1 MR 강조 영상의 자기값으로 대체시키고, 2, 4장으로 분리된 병리 영상을 한장의 영상으로 만든 후 MR 영상과 동일한 해상도로 줄인다. 둘째, 전립선의 T2 MR 강조 영상과 병리 영상 간에 자기간의 상호정보를 최적화하는 강체변환을 구한다. 셋째, TPS 와핑을 이용하여 병리 영상의 전립선 부위가 T2 MR 강조 영상의 전립선 부위에 정합되는 비강체변환을 구한다. 넷째, MR 영상과 변환을 적용시킨 병리 영상을 융합한다. 실험 결과 영상보정 및 다단계 정합 후의 전립선의 T2 MR 강조 영상과 병리 영상의 간의 평균 거리 오차는 0.8815 mm였고, 두 영상의 융합을 통해 T2 MR 강조 영상에서 전립선 암의 위치를 정확하게 볼 수 있었다.

• Journal of Korean Neurosurgical Society
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• 제49권6호
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• pp.363-366
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• 2011

Cerebellar pilocytic astrocytomas (PAs) are benign gliomas predominantly found in the pediatric population. Intracranial hemorrhages are extremely rare in initial presentations of cerebellar PAs. There are no reports in the medical literature of adult cerebellar PA cases presenting with intratumoral hemorrhage. We report 2 cases of adult cerebellar pilocytic astrocytomas with intratumoral hemorrhage. The first case is a 37-year-old woman presenting with severe headache, nausea, and vomitting. Computed tomography demonstrated an acute hemorrhage adjacent to the right cerebellar hemisphere and hydrocephalus. Magnetic resonance imaging (MRI) revealed a cerebellar vermian tumor with the hemorrhage as a mixed isoin-tense area in the T2-weighted image, and as a mixed hyperintense area in the contrast-enhanced T1-weighted image. The second case is a 53-year-old man presenting with headache for 3 weeks. MRI revealed a cerebellar hemispheric tumor with the hemorrhage as a mixed hyperintense area. It had a cystic mass with a heterogeneous enhanced mural nodule in the gadolinium-enhanced T1-weighted image and a fluid-fluid level within the cyst in the T2-weighted image. Both of them underwent radical resections of their respective lesions. Histological examination of the specimens revealed typical astrocytoma, including a hemorrhagic portion. Both patients recovered postoperatively and continue to do well at present. The medical literature on hemorrhagic cerebellar PAs is also reviewed.

• 대한방사선기술학회지:방사선기술과학
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• 제24권2호
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• pp.19-22
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• 2001

The purpose of this study is to evaluate time course of signal enhancement on Gadomer-17 enhance MRI, and to correlate the size of enhanced area with that of the infarct area on 2'3'5'-triphenyl tetrazolium chloride(TTC) histochemical examination for the assessment of myocardial viability in reperfused Myocardial Infarction in a cat model. Tan cats(average weight: 3.8 kg) which had undergone 90 minutes of occlusion of the LAD followed by 90 minutes of reperfusion underwent MR T2-weighted imaging, and T1-weighted imaging, enhanced T1-weighted imaging. We used 1.5T Magneton Vision MRI system(Siemens, Erlangen, Germany). Signal intensities were measured in the enhanced and non-enhanced areas of enhanced T1-weighted imaging. and TTC histochemical staining the size of the abnormal signal area on each image was compared with that of the infarct area. Maximum enhancement was detected during a $40{\sim}60$ minute period with an average enhancement of $168{\pm}9.9%$ of normal myocardium. TTC staining revealed that the size of the high signal area on T2-weighted images and of the enhanced area on enhanced T1-weighted images was greater than that of the infarct area($T2=48.1%{\pm}3.7$, enhanced $T1=47.2%{\pm}2.6$, TTC $staining=38.7%{\pm}3.1$ ; p<0.05). In reperfused Myocardial Infarction in a cat model, enhanced MR imaging delineates reversibly and irreversibly damaged myocardium, with a strong enhancement and a broad temporal window. We may therefore expect that enhanced MR image is useful for demonstrating myocardial injury.

• 대한의생명과학회지
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• 제10권4호
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• pp.367-373
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• 2004

Evaluated the hyperacute embolic effects of triolein and oleic acid in cat brains by using MR image and electron microscopy. In fat embolism, free fatty acid is more toxic than neutral fat in terms of tissue damage. T2-Weighted imaging, diffusion-weighted imaging, and contrast-enhanced T1-weighted imaging were performed in cat brains after the injection of triolein (group 1, n=8) or oleic acid (group 2, n=10) into the internal carotid artery. MR image were quantitatively assessed by comparing the lesions with their counterparts on T2-weighted images, apparent diffusion coefficient (ADC) maps, and contrast-enhanced T1-weighted images. Electron microscopic findings in group 1 were compared with those in group 2. Qualitatively, MR images revealed two types of lesions. Type 1 lesions were hyperintense on diffusion-weighted images and hypointense of ADC maps. Type 2 lesions were isointense or mildly hyperintense on diffusion-weighted images and isointense on ADC maps. Quantitatively, the signal intensity rations of type 1 lesions in group 2 specimens were significantly higher on T2-weighted images (P=.013)/(P=.027) and lower on ADC maps compared with those of group 1. Electron microscopy of type 1 lesions in both groups revealed more prominent widening of the perivascular space and swelling of the neural cells in groups 1. MR and electron microscopic data on cerebral fat embolism induced by either triolein or oleic acid revealed characteristics suggestive of both vasogenic and cytotoxic edema in the hyperacute stage. Tissue damage appeared more severe in the oleic acid group than in the triolein group.