• Journal of Biomedical Engineering Research
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• v.18 no.3
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• pp.243-251
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• 1997

In this paper, we have reported two interesting flow effects arising in the TRFGE sequence using water flow phantom. First, we have shown that the TRFGE sequence is indeed not affected by "in-flow" effect from the unsaturated spins flowing into the imaging slice. Second, the enhancement of "in-plane flow" signal in the readout gradient direction was observed when the TRFGE sequence was used without flow compensation. These two results have many interesting applications in MR imaging other than fMRI. Results obtained were also compared with the results obtained by the conventional gradient echo(CGE) imaging. Experiments were performed at 4.7T MRI/S animal system (Biospec, BRUKER, Switzerland). A cylindrical phantom was made using acryl and a vinyl tube was inserted at the center(Fig. 1). The whole cylinder was filled with water doped with $MnCl_2$ and the center tube was filled with saline which flows in parallel to the main magnetic field along the tube. Tailored RF pulse was designed to have quadratic ($z^2$) phase distribution in slice direction(z). Imaging parameters were TR/TE = 55~85/10msec, flip angle = $30^{\circ}$, slice thickness = 2mm, matrix size = 256${\times}$256, and FOV= 10cm. In-flow effect : Axial images were obtained with and without flow using the CGE and TRFGE sequences, respectively. The flow direction was perpendicular to the image slice. In-plane flow : Sagittal images were obtained with and without flow using the TRGE sequence. The readout gradient was applied in parallel to the flow direction. We have observed that the "in-flow" effect did not affect the TRFGE image, while "in-plane flow" running along the readout gradient direction enhanced the signal in the TRFGE sequence when flow compensation gradient scheme was not used.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.129-134
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• 1996

1차 년도 G-7 개발 과제로 수행된 자기 공명 진단 장치 (Magnetic Resonance Imaging System)의 개발 내용을 간략히 소개하였다. 성공적인 IT Compact 자기 공명 진단 장치의 완성을 위해 일차적으로 (1)RF (고주파), Gradient(경사 자계), Spectrometer 등의 Hard-ware 관련 MRI 핵심부분, (2) RF, Gradient, Spectrometer, Magnet 등의 각 Sub-system을 연결, 조합, 조정하여 하나의 체계적인 시스템으로 통합하고 운영하는 과정(System Integration), (3)사용자와 시스템을 연결하는 User Interface, Data Base Management, Real time 운영 SW 등과 (4)임상에 적용하여 구체적인 성능과 효용성을 확인하는 기술 등에 대하여 집중 연구하였다. 개발 방법은 (1)지난 16년간 국내에 축적 된 연구 개발 인력들을 최대한 활용하고 (2)연구 개발을 국제화 시켜 필요한 경우 부분별로 개발 인력을 해외에서 보완하고 (3)소수 정예 전문 인력 주의와 요소 기술 또는 중요 부품을 경쟁성 검토 후 필요 시 Out-sourcing 활용으로 최저의 비용으로 개발 기간을 최소화 하는 데 두었다. 개발된 1.0Tesla자기 공명 영상 장치는 미국 물리 학회에서 규격화한 Phantom및 임상 적용을 통하여 서울대 의대 연구 팀과 지속적으로 성능을 평가해 왔다. 개발된 시스템의 해상도는 $256{\times}256$ head 영상에서 1mm 이 하의 해상도를 가짐을 resolution phantom 을 통하여 확인할 수 있었고, $512{\times}512$ 영상에서 는 약 0.5 mm 의 물체를 분리 해냄으로써 외제 시스템들 보다 우수하게 평가 되었다. 차폐 경사코일의 Eddy current영향은2%이내로 촬영 시 영향은 거의 무시할 수 있었다. 또한, 개발된 영상 기법들, 즉 Multislice/Multi Echo, Oblique angle imaging, 64 Echo train을 갖는 고속 촬영 기술들이 자기 공명 장치에 장착되어 임상 적용에 문제가 없도록 하였다. 또한 20mT/m/Amp의 강력한 능동 차폐 경사 자계 코일(Active Shield Gradient Coil)을 기본 사양으로 하고, 수신단을 최대 6개로 확장토록 하여 2차년도의 초고속 촬영 기법(EPI) 및 Phased Array 코일 촬영이 가능토록 하였다. 1차 년도 개발 과제 수행 결과와 향후 개발 과제를 바탕으로 최종 목표인 국제 경쟁력이 있는 자기 공명 진단 장치 즉 기능과 영상의 질은 선진국 제품과 동일하거나 우수하되, 저가격을 구현한 상용화 제품이 완성되어, 첨단 의료기기로서 산업 구조 고도화에 기여하고 수입대체 뿐만 아니 라 수출을 통한 국익 창출과 국가의 기술을 통한 위상 제고에 기여되길 기대한다.

• Journal of radiological science and technology
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• v.26 no.2
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• pp.57-61
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• 2003

The purpose of this study is to compare both 1.5T and 4.7T in Praietal White matter material Phantom using the same methodology at both field strengths. Data at both field strengths are compared in terms of $T_2$ relaxation times, line widths and SNRs MR imaging and $^1H$ MR spectroscopy were performed on GE 1.5T SIGNA system and Broker Biospec 4.7T/30 MRI/MRS system. After phantom axial scan $^1H$ MRS was obtained from T2 weighted image by 3-dimensional localization technique(PRESS : Point RE solved spectroscopy Sequence) this phantom is composed of an aqueous solution 36.7 mmol/L of NAA, 25.0 mmol/L of Cr, 6.3 mmol/L of choline chloride, 30.0 mmol/L or Glu, and 22.5 mmol/L of MI(adjusted to a pH of 7,15 in a phosphate buffet). Data processed using software developed inhouse. At 1.5T, T2 relaxation times for Cho, Cr, and NAA were $0.41{\pm}0.07,\;0.26{\pm}0.04,\;0.46{\pm}0.07$ while at 4.7T they were $0.17{\pm}0.03,\;0.14{\pm}0.05,\;0.20{\pm}0.03$ respectively. At 1.5T, line widths for water, Cho, Cr and NAA were $2.9{\pm}0.7,\;1.6{\pm}0.7,\;1.7{\pm}0.8,\;2.2{\pm}0.02Hz$ while at 4.7T they were $5.2{\pm}1.1,\;4.6{\pm}1.9,\;4.01{\pm}1.8,\;4.8{\pm}1.9Hz$ respectively. It can be seen that $T_2$ relaxation times were significantly shorter at 4.7 compared to 1.5T and that the line widths were also broader. The average SNRs for NAA for subjects at short and long TEs were $23.5{\pm}11.3$ at TE=20 msec ; $15.4{\pm}7.7$ at TE=272 msec at 1.5T and $40{\pm}8.3$ and $17{\pm}3.5$ respectively at 4.7T higher field strength is superior because of improved sensitivity and chemical shift dispersion. However these improvements are partially offset by increased line widths and decrease $T_2$ relaxation times, which act to reduce both sensitivity and resolution. In our experiments with the equipment available to us, 4.7T proton spectra at short TEs exhibit moderately improved sensitivity compared to 1.5T.

• Progress in Medical Physics
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• v.7 no.2
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• pp.67-77
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• 1996

Purpose: To get a 3-D coordinates of intracranial target position was investicated in axial, sagittal and coronal magnetic resonance imaging with a preliminary experimented target localizer. Material and methods : In preliminal experiments, the localizer is made of engineering plastic to avoid the distrubance of magnetic field during the MR image scan. The MR localizer displayed the 9 points in three different axial tomogram. The bright signal of localizer was obtjained from 0.1～0.3％ of paramagnetic gadolinium/DTPA solution in T1WI or T2WI. In this study, the 3-D position of virtual targets were examined from three different axial MR images and the streotactic position was compared to that of BRW stereotactic system in CT scan with same targets. Results: This study provided the actual target position could be obtained from single scan with MRI localizer which has inverse N-typed 9 bars. This experiment was accomplished with shimming test for detection of image distortion in MR image. However we have not found the image distortion in axial scan. The maximum error of target positions showed 1.0 mm in axial, 1.3 mm for sagittal and 1.7 mm for coronal image, respectivelly. The target localization in MR localizer was investicated with spherical virtual target in skull cadaver. Furthermore, the target position was confirmed with CRW stereotactic system showed a 1.3 mm in discrepancy. Summary : The intracranial target position was determined within 1.7 mm of discrepancy with designed MR localizer. We found the target position from axial image has more small discrepancy than that of sagittal and coronal image.

• Journal of Korean Neurosurgical Society
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• v.51 no.1
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• pp.8-13
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• 2012

Objective : This is prospective study of clinical outcomes of percutaneous plasma disc coagulation Therapy (PDCT) in patients with herniated lumbar disc disease (HLD) to evaluate the safety and efficacy in its clinical application and usefulness as a reliable alternative to microscopic discectomy. Methods : Forty-six patients were enrolled in this study from April 2006 to June 2010. All patients had one-level HLD. Disc degeneration was graded on routine T2-weighted magnetic resonance Image (MRI) using the Pfirrmann's grading system and all index levels were grade 3 and grade 4. Indications for surgery were radiculopathy caused by disc protrusion with soft consistency. MRI was done at one month after the procedure in all patients to check post-PDCT change. The clinical outcomes were evaluated using Visual Analog Scales (VAS) score and MacNab's criteria. Results : This study was approved by the Institutional Review Board of our institution. The age of the study population ranged from 16 to 59 years with a mean age of 37.2 years. There were 29 males and 17 females in this study. The mean period of clinical follow-up was 21 months. The average preoperative VAS score for radiculopathy was $7.4{\pm}1.4$, while the final follow-up VAS score was $1.4{\pm}0.7$ (p<0.001). In MacNab's criteria, 41 patients (89.1%) had achieved favorable improvement (excellent and good) until later follow-up. There were one patient from infection and two patients who needed to convert to open discectomy. Conclusion : PDCT is a safe and efficient treatment modality in a selective patient with HLD.

• Journal of The Korean Association For Science Education
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• v.27 no.1
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• pp.84-92
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• 2007

The purpose of this study was to investigate biologists' brain activation patterns during the generation of scientific questions on biological phenomena. Eight right-handed healthy biologists volunteered to be participants in the present study. The question-generation tasks were presented in a block design. The BOLD signals of the biologists' brain were measured by 3.0T fMRI system and data were analyzed using Statistical Parametric Mapping (SPM2). According to our results, the left inferior and middle frontal gyri, the medial prefrontal cortex, the bilateral hippocampus, the occipito-parietal route, the fusiform gyrus, and the cerebellum were activated significantly during the generation of scientific questions. Therefore, we suggested that generating scientific question is associated with analyzing observed situations, using verbal strategy, retrieving episodic memories for comparisons, and feeling cognitive conflicts.

• Journal of the Korean Magnetics Society
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• v.26 no.6
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• pp.219-225
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• 2016

In this study, for assessment of degenerative knee joint cartilage disease we acquired images by fat suppressed 3D spoiled gradient recalled (SPGR) and fat suppressed 3D $T2^*$ weighted imaging techniques. To do a quantitative evaluation, the knee joint cartilage was divided into medial femoral cartilage (MFC), medial tibial cartilage (MTC), lateral femoral cartilage (LFC), lateral femoral cartilage (LFC) and patella cartilage (Pat) to measure their respective signal intensity values, signal-to-noise ratio, and contrast-to-noise ratio. As for the measured values, statistical significance between two techniques was verified by using Mann-Whitney U-Test. To do a qualitative evaluation, two radiologists have examined images by techniques after which image artifact, cartilage surface, tissue contrast, and depiction of lesion distinguishing were evaluated based on 4-point scaling (1: bad, 2: appropriate, 3: good, 4: excellent), and based on the result, statistical significance was verified by using Kappa-value Test. 3.0T MR system and HD T/R 8ch knee array coil were used to acquire images. As a result of a quantitative analysis, based on SNR values measured by using two imaging techniques, MFC, LFC, LTC, and Pat showed statistical significance (p < 0.05), but MTC did not (p > 0.05). As a result of verifying statistical significance for measured CNR value, MFC, LFC, and Pat showed statistical significance (p < 0.05), while MTC and LTC did not show statistical significance (p > 0.05). As a result of a qualitative analysis, by comparing mean values for evaluated image items, 3D $T2^*$ weighted Image has indicated a slightly higher value. As for conformance verification between the two observers by using Kappa-value test, all evaluated items have indicated statistically significant results (p < 0.05). 3D $T2^*$ weighted technique holds a clinical value equal to or superior to 3D SPGR technique with respect to evaluating images, such as distinguishing knee joint cartilages, comparing nearby tissues contrast, and distinguishing lesions.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.73-73
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• 2003

Purpose: To determine the motor cortex dysfunction in hemiparetic patients due to deep intracerebral hematoma, authors performed proton magnetic resonance spectroscopy (lH MRS) for the evaluation of biochemical changes in the cortex on affected hemisphere according to axonal injury at the level of internal capsule. Methods: Ten control subjects and 14 patients with documentable hemiparesis of varying severity hemiparesis were included. All the hemiparesis was caused by deep intracerebral hematoma (putaminal and thalamic hemorrhage). In vivo 1H MRS study was performed on a 3T MRI/MRS system using STEAM sequence. As a single-voxel technique, Spectral parameters were: 20 ms TE, 2000 ms TR, 128 averages, 2500 Hz spectral width, and 2048 data points. Results: We found that the mean N-acetylaspartate (NAA)/phosphocreatine (Cr) and NAA/choline (Cho) ratios were significantly decreased in the motor cortex of the hemiparesis patients compared with control subjects. Conclusions: 1H MRS examinations of the motor cortex might help to differentiate distinct clinical entities of hemiparesis and to monitor pharmacological effects in therapeutic trials, providing a quantitative biological marker for motor neuron dysfunction. Acknowledgement: This study was supported by a grant of the Center for Functional and Metabolic Imaging Technology, Ministry of Health & Welfare, Republic of Korea. (02-PJ3-PG6-EV07-000).

• Journal of the Korean Arthroscopy Society
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• v.16 no.2
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• pp.140-146
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• 2012

Purpose: The objective of this study was to assess the clinical outcome of arthroscopic release of the extensor carpi radialis brevis (ECRB) tendon in chronic recalcitrant lateral epicondylitis and tried to determine any prognostic factors. Materials and Methods: A retrospective review of 24 patients with lateral epicondylitis treated by arthroscopic ECRB release was performed. Outcome measures included a patient self rating and visual analog scale (VAS). Functional evaluation was made with Quick-disabilities of the arm, shoulder and hand (DASH) score system to identify preoperative factors that might be associated with the outcomes. Results: Twenty one (88%) elbows received benefit from the procedure. A mean preoperative VAS pain score and the mean Quick-DASH were significantly improved at final follow up. Age, sex, dominant arm and duration of symptom, presence of capsular tear or calcification did not correlate significantly with the clinical outcome. Three of four patients without T2-weighted high signal focus of the ECRB origin on preoperative magnetic resonance imaging (MRI) showed higher Quick-DASH score. Conclusion: Arthroscopic release of the ECRB is an effective option for chronic recalcitrant lateral epicondylitis. Lack of high signal focus on preoperative MRI is significantly associated with a poor surgical outcome and a considerable factor for the proper surgical indication.

• Investigative Magnetic Resonance Imaging
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• v.12 no.1
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• pp.1-7
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• 2008

Purpose : To compare Multi Echo Data Image Combination (MEDIC) and fast SE T2-weighted images with fat saturation (T2FS) to suggest more accurate evaluation of the histologic components of soft-tissue tumors. Materials and Methods : The experimental group included 25 histologic tissues (5 vascular, 4 neural, 4 fibrous, 4 hypercellular, 2 hemorrhagic necroses, 2 cystic, 2 lipoid, 1 myxoid stroma, and 1 thrombus) in 10 patients who had pathologically confirmed schwannoma (n = 3), hemangioma (n = 2), lipoma (n = 1), angiokeratoma (n = 1), synovial sarcoma (n = 1), liposarcoma (n = 1), and malignant fibrous histiocytoma (n = 1). The inhomogeneity values were measured using the standard deviation value (SD) divided by the mean value as SD presents an error amount similar to that of imaging heterogeneity. Results : The inhomogeneity values of 25 histologic components were lower on MEDIC than those on T2FS (p < .001). Conclusion : We conclude that MEDIC is more accurate than T2FS for evaluating the tissue components of soft-tissue tumors using digitalized data because MEDIC images have far lower inhomogeneity.