• Investigative Magnetic Resonance Imaging
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• 제3권1호
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• pp.47-52
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• 1999

목적 : 시각자극을 이용하여 대뇌 후두엽에서 BOLD(blood oxygen level dependent)효과에 의한 기능적 자기공명영상과 양성자 자기공명분광법을 이용한 대사물질영상( metabolic i image)을 얻어 그 결과를 평가하고자 하였다. 대상 및 방법 : 24세에서 30세 사이의 8명의 남자와 2명의 여자를 포함하는 10명의 정상 성인 남녀를 대상으로 1.5T MRI에서 시각 지극을 이용하여 echo planar imaging펠스시퀀스를 사용하여 BOLD효과에 의한 영상들을 대뇌 후두엽에서 얻었다. 시각자극은 8Hz의 red flicker를 이용한 광 자극을 주였다. MR에서 얻어진 영상들을 workstation으로 전송한 뒤 자체 개발한 분석프로그램을 사용하여 상관계수방법을 이용하여 기능적 영상을 구하였다. 그리고 얻어진 영상의 활성화 부위를 선정한 뒤 양성자 자기공명 분광법을 사용하여 시각 자극에 의한 뇌 활성화시 대사물질의 변화를 분석했다. 그 후 자가공명분광영상법(magnetic resonance spectro-scopic imaging)를 실행하여 젖산(lactate)의 대사물질 영상을 얻었다. 결과 : 시각 자극에 따른 BOLD효과에 의한 뚜렷한 활성화 부위가 후두염 대뇌피질에 나타났다. 또한 이들 활성화 부위에서 자기공명분광법을 시행한 결과 휴식상태와 시각자극상태에서 NAA(N-acetyle aspartate)/Cr(creatine)이 $1.79{\pm}0.28$에서 $1.88{\pm}O.20$으로 거의 변화가 없는 것에 반해 lactate는 자극 전후 $9.48{\pm}4.38$배로 증가하였으며 이를 바탕으로 lactate에 대한 대사물질영상을 얻을 수 있었다. 결론 : 시각자극에 의한 뇌 활성화시 BOLD효과를 이용한 자기공명영상볍으로 활성화 부위를 확인할 수 있었고, 같은 부위에서 자기공명분광법을 이용하여 lactate의 증가를 확인하였다. 또한 lactate의 증가를 대사물질영상으로 표현함으로써 두 결과에 대한 상관관계 및 뇌 기능적영상에 대한 신뢰성을 높일 수 있게 되었다.

• Investigative Magnetic Resonance Imaging
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• 제3권1호
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• pp.53-59
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• 1999

목적 : 언어기능의 지도화(language mapping) 및 우세반구 결정에 있어서 기능적 자기공명영상의 유용서을 알아보고자 하였다. 대상 및 방법 : 자원자 10명(남자 6명, 여자 4명, 오른손잡이 7명, 왼손잡이 3명)을 대상으로 단어생성 과제(명사만들기, 동사만들기)와 판단과제를 이용하여 언어영역의 활성화를 유도하였다. 1.5T 초진도 자기공명영상장치에서 EPI로 BOLD 기법을 이용하여 기능적 영상을 얻었으며, 여앙후처리는 SPM 분석 프로그램을 이용하였다. 기능적 영상은 2번의 활성기와 3번의 휴식기를 번갈아 시행하였고 스캔 시간은 각각30초였으며 총 영상획득시간은 162초였다. 유의수준 p<0.001을 기준ㅇ로 자극 과제에 따라 활성화된 뇌영역을 분석하였고 반구별로 활성화된 화소의 수를 측정하여 편재화지수(lateralization index)를 구하였다. 결과 : 왼손잡이 1명을 제외한 9명에서 성공적으로 기능적 영상을 얻었으며 양측 전운동영역(premotor area), 하전두회, 두정엽, 중측두회 등의 여러 영역에서 활성화 신호가 나타났다. 오른손잡이의 경우 편재화지수는 평균 0,64(0.16~1)로 모두 좌측으로 편재화 되었다. 과제별로는 동사만들기 과제가 명사만들기 및 판단 과제에 비해 언어 영역의 활성화가 많았고 편재화지수의 값도 높았다. 결론 : 기능적 자기공명영상은 언어영역의 뇌기능지도화 및 우세반구 결저에 있어서 유용한 검사 방법이 될 수 있으리라 생각된다.

• Investigative Magnetic Resonance Imaging
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• 제25권1호
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• pp.1-9
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• 2021

The aim of this study was to provide a new assessment of rotator cuff muscle activity. Eight male subjects (24.7 ± 3.2 years old,171.2 ± 9.8 cm tall, and weighing 63.8 ± 11.9 kg) performed the study exercises. The subjects performed 10 sets of the exercise while fixing the elbow at 90 degrees flexure and lying supine on a bed. One exercise set consisted of the subject performing external shoulder rotation 50 times using training equipment. Two imaging protocols were employed: (a) true fast imaging with steady precession (TrueFISP) at an acquisition time of 12 seconds and (b) multi-shot spin-echo echo-planar imaging (MSSE-EPI) at an acquisition time of 30 seconds for one echo. The main method of assessing rotator cuff muscle activity was functional T2 mapping using ultrafast imaging (fast-acquired muscle functional MRI [fast-mfMRI]). Fast-mfMRI enabled real-time imaging for the identification and evaluation of the degree of muscle activity induced by the exercise. Regions of interest were set at several places in the musculus subscapularis (sub), musculus supraspinatus (sup), musculus teres minor (ter), and deltoid muscle (del). We used the MR signal of the images and transverse relaxation time (T2) for comparison. Most of the TrueFISP signal was not changed by exercise and there was no significant difference from the resting values. Only the T2 in the musculus teres minor was increased after one set and the change were seen on the T2 images. Additionally, except for those after one and two sets, the changes in T2 were significant compared to those at rest (P < 0.01). We also demonstrated identify and visualize the extent to which muscles involved in muscle activity by exercise. In addition, we showed that muscle activity in a region such as a shoulder, which is susceptible to B0 inhomogeneity, could be easily detected using this technique.

• 한국자기공명학회논문지
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• 제7권1호
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• pp.1-15
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• 2003

PURPOSE - To investigate neurometabolism from the brain destructive lesions and striatal putamen-pallidus regions to the clinically worst side in patients with Parkinson's disease after stereotactic functional neurosurgery. METHODS - Using proton magnetic resonance spectroscopy ($^1$H MRS), fifteen patients (7 males and 8 females; mean age 56.5 years; age range 43-67 years) with Parkinson's disease (PD) were studied to measure N-acetylaspartate (NAA), creatine (Cr), choline-containing compounds (Cho) and lactate (Lac) levels on the neurosurgical lesions of thalamus, globus pallidus and striatal putamen-pallidus regions in a brain. RESULTS - Brain destructive lesion and striatal putamen-pallidus region in PD compared with controls were highly and significantly related to NAA/Cho ratios reduction, respectively (P =0.002, P =0.04), but showed no difference from the same regions of PD prior to neurosergery (P =0.06, P =0.77). Increased lactate peaks at 1.3 ppm were present in all the cerebral lesions, and these resonances were confirmed at a long TE =136 ms, indicating that these signals distinguished from lipids. CONCLUSIONS - Our results suggest that NAA/Cho ratios may provide as a neurometabolite marker for neurochemical changes in brain surgical lesion, and the ratios might be related to functional change of neuropathophysiological status in the striatal putamen-pallidus region of PD. Increase of lactate signals, being remarkable in surgical lesions, could be consistent with a common consequence of surgical necrosis. Therefore, MR spectroscopy could be a sensitive diagnostic tool in monitoring neurometabolic changes in PD with neurosurgical treatment.

• Investigative Magnetic Resonance Imaging
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• 제3권1호
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• pp.78-83
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• 1999

목적: 기능적 자기공명영상을 이용하여 읽기 과제에서 활성화되는 뇌영역을 알아보고, 읽기 과제의 종류에 따른 활성화 영여의 차이를 규명하고자 하였다. 대상 및 방법: 오른손잡이 자원자 9명(남자 7명, 여자 2명)을 대상으로 한글의 자음, 가짜단어, 단어를 속으로 읽도록 하면서 기능적 영상을 얻었다. 1.5T 초전도 자기공명여앙장치에서 EPI의 BOLD 기법을 이용하여 20 절편의 활성화 영상을 얻었고(gradient echo single shot EI, TR/TE 3000/60, flip angle $90^{\circ}$, matrix $64{\times}64$, 5mm thickness, no slice gap), 영상후처리는 SPM 분석 프로그램을 이용하였다. 2번가의 활성기와 3번의 휴식기를 번갈아 시행하였고 스캔 시간은 각각30초였다. 유의수준 p<0.01을 기준으로 자극 과제에 따라 활성화된 뇌지도를 얻어 활성화 영역을 육안으로 비교 분석하여다. 결과: 9명 모두에서 성공적으로 활성화 영상을 얻었고, 활성화 신호는 모든 자극과제에서 후두엽의 화성화를 제외하고 좌측으로 편재되는 경향을 보였으며, 전두엽, 측두엽, 두정엽, 후두엽의 여러 부위에서 활성화 신호가 나타났다. 가짜단어와 자음을 읽은 경우가 단어를 읽은 경우에 비하여 언어영역의 활성화가 많았다. 가짜단어를 읽은 경우가 자으을 읽은 경우에 비해 활성화 신호가 좌측으로 편재화 되는 경향을 나타냈다. 결론: 자음이나 단어형태를 읽는 것 만으로도 언어와 관련된 여러 뇌영역에 활성화가 유도됨을 확인하였으며, 자음이나 가짜단어를 읽는 것이 익숙한 단어를 읽는 것에 비해 활성화 신호가 많았다.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2002년도 제7차 학술대회 초록집
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• pp.111-111
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• 2002

Purpose： This study is to compare the distinct brain activation between implicit and explicit memory retrieval tasks using a non-invasive blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging(fMRI). Materials ＆ Methods： We studied seven right-handed, healthy volunteers aged 21-25 years(mean；22 years) were scanned under a 1.5T Signa Horizon Echospeed MR imager(GE Medical Systems, Milwaukee, U.S.A.). During the implicit and explicit memory retrieval tasks of previously teamed words under the conceptual processing, we acquired fMRI data using gradient-echo EPI with 50ms TE, 3000ms TR, 26cm${\times}$26cm field-of-view, 128${\times}$128 matrix, and ten slices(6mm slice thickness, 1 mm gap) parallel to the AC-PC(anterior commissure and posterior commissure) line. By using the program of statistical parametric mapping(SPM99), functional activation maps were reconstructed and quantified.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권11호
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• pp.3479-3492
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• 2022

Longitudinal quantification of brain changes due to development, aging or disease plays an important role in the filed of personalized-medicine applications. However, due to the temporal variability in shape and different imaging equipment and parameters, estimating anatomical changes in longitudinal studies is significantly challenging. In this paper, a longitudinal Magnetic Resonance(MR) brain image segmentation algorithm proposed by combining intensity information and anisotropic smoothness term which contain a spatial smoothness constraint and longitudinal consistent constraint into a variational framework. The minimization of the proposed energy functional is strictly and effectively derived from a fast optimization algorithm. A large number of experimental results show that the proposed method can guarantee segmentation accuracy and longitudinal consistency in both simulated and real longitudinal MR brain images for analysis of anatomical changes over time.

• IEIE Transactions on Smart Processing and Computing
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• 제4권5호
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• pp.311-317
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• 2015

The aim of this study is to develop a 3D registration algorithm for positron emission tomography/computed tomography (PET/CT) and magnetic resonance (MR) images acquired from independent PET/CT and MR imaging systems. Combined PET/CT images provide anatomic and functional information, and MR images have high resolution for soft tissue. With the registration technique, the strengths of each modality image can be combined to achieve higher performance in diagnosis and radiotherapy planning. The proposed method consists of two stages: normalized mutual information (NMI)-based global matching and independent component analysis (ICA)-based refinement. In global matching, the field of view of the CT and MR images are adjusted to the same size in the preprocessing step. Then, the target image is geometrically transformed, and the similarities between the two images are measured with NMI. The optimization step updates the transformation parameters to efficiently find the best matched parameter set. In the refinement stage, ICA planes from the windowed image slices are extracted and the similarity between the images is measured to determine the transformation parameters of the control points. B-spline. based freeform deformation is performed for the geometric transformation. The results show good agreement between PET/CT and MR images.

• Korean Journal of Radiology
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• 제25권1호
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• pp.24-32
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• 2024

Despite improvements in operative techniques and perioperative care, post-hepatectomy liver failure (PHLF) remains the most serious cause of morbidity and mortality after surgery, and several risk factors have been identified to predict PHLF. Although volumetric assessment using imaging contributes to surgical simulation by estimating the function of future liver remnants in predicting PHLF, liver function is assumed to be homogeneous throughout the liver. The combination of volumetric and functional analyses may be more useful for an accurate evaluation of liver function and prediction of PHLF than only volumetric analysis. Gadoxetic acid is a hepatocyte-specific magnetic resonance (MR) contrast agent that is taken up by hepatocytes via the OATP1 transporter after intravenous administration. Gadoxetic acid-enhanced MR imaging (MRI) offers information regarding both global and regional functions, leading to a more precise evaluation even in cases with heterogeneous liver function. Various indices, including signal intensity-based methods and MR relaxometry, have been proposed for the estimation of liver function and prediction of PHLF using gadoxetic acid-enhanced MRI. Recent developments in MR techniques, including high-resolution hepatobiliary phase images using deep learning image reconstruction and whole-liver T1 map acquisition, have enabled a more detailed and accurate estimation of liver function in gadoxetic acid-enhanced MRI.

• Investigative Magnetic Resonance Imaging
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• 제21권4호
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• pp.223-232
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• 2017

Purpose: To report the use of multiband accelerated echo-planar imaging (EPI) for resting-state functional MRI (rs-fMRI) to achieve rapid high temporal resolution at 3T compared to conventional EPI. Materials and Methods: rs-fMRI data were acquired from 20 healthy right-handed volunteers by using three methods: conventional single-band gradient-echo EPI acquisition (Data 1), multiband gradient-echo EPI acquisition with 240 volumes (Data 2) and 480 volumes (Data 3). Temporal signal-to-noise ratio (tSNR) maps were obtained by dividing the mean of the time course of each voxel by its temporal standard deviation. The resting-state sensorimotor network (SMN) and default mode network (DMN) were estimated using independent component analysis (ICA) and a seed-based method. One-way analysis of variance (ANOVA) was performed between the tSNR map, SMN, and DMN from the three data sets for between-group analysis. P < 0.05 with a family-wise error (FWE) correction for multiple comparisons was considered statistically significant. Results: One-way ANOVA and post-hoc two-sample t-tests showed that the tSNR was higher in Data 1 than Data 2 and 3 in white matter structures such as the striatum and medial and superior longitudinal fasciculus. One-way ANOVA revealed no differences in SMN or DMN across the three data sets. Conclusion: Within the adapted metrics estimated under specific imaging conditions employed in this study, multiband accelerated EPI, which substantially reduced scan times, provides the same quality image of functional connectivity as rs-fMRI by using conventional EPI at 3T. Under employed imaging conditions, this technique shows strong potential for clinical acceptance and translation of rs-fMRI protocols with potential advantages in spatial and/or temporal resolution. However, further study is warranted to evaluate whether the current findings can be generalized in diverse settings.