• Investigative Magnetic Resonance Imaging
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• 제26권2호
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• pp.125-134
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• 2022

Purpose: The aim of this study was to investigate the change in signal sensitivity over different acquisition start times and optimize the scanning window to provide the maximal signal sensitivity of [1-¹³C]pyruvate and its metabolic products, lactate and alanine, using spatially localized hyperpolarized 3D ¹³C magnetic resonance spectroscopic imaging (MRSI). Materials and Methods: We acquired 3D ¹³C MRSI data from the brain (n = 3), kidney (n = 3), and liver (n = 3) of rats using a 3T clinical scanner and a custom RF coil after the injection of hyperpolarized [1-¹³C]pyruvate. For each organ, we obtained three consecutive 3D ¹³C MRSI datasets with different acquisition start times per animal from a total of three animals. The mean signal-to-noise ratios (SNRs) of pyruvate, lactate, and alanine were calculated and compared between different acquisition start times. Based on the SNRs of lactate and alanine, we identified the optimal acquisition start timing for each organ. Results: For the brain, the acquisition start time of 18 s provided the highest mean SNR of lactate. At 18 s, however, the lactate signal predominantly originated from not the brain, but the blood vessels; therefore, the acquisition start time of 22 s was recommended for 3D ¹³C MRSI of the rat brain. For the kidney, all three metabolites demonstrated the highest mean SNR at the acquisition start time of 32 s. Similarly, the acquisition start time of 22 s provided the highest SNRs for all three metabolites in the liver. Conclusion: In this study, the acquisition start timing was optimized in an attempt to maximize metabolic signals in hyperpolarized 3D ¹³C MRSI examination with [1-¹³C] pyruvate as a substrate. We investigated the changes in metabolic signal sensitivity in the brain, kidney, and liver of rats to establish the optimal acquisition start time for each organ. We expect the results from this study to be of help in future studies.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.517-527
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• 1997

Magnetic Resonance Spectroscopic Imaging is a methodology combining the imaging and spectroscopy. It can provide the spectrum of each areas of image so that one can easily compare the spectrum of one position to another position of the image. In this study, we developed pulse sequence or the spectroscopic imaging method, RF wave forms or the saturation of water signal, computer simulations to validate our method, and confirmed the methodology with phantom experiment. Then we applied the spectroscopic method to human subject and identified a few important metabolites in in vivo. To develope a water saturating RF waveform, we used Shinnar-Le-Roux algorithm and obtained maximum phase RF waveform. With this RF pulse, it could suppress the water signal to 1:1000. The magnet is shimmed to under 1.0ppm with auto-shimming technique. The saturation bandwidth is 80Hz(2ppm). The water and fat seperation is 3.3ppm(about 140Hz at 1 Tesla magnet), the bandwidth is enough to resolve the difference. But we are more concerned about the narrow window in between the two peaks, in which the small quantity of metabolites reside. We performed the computer simulation and phantom experiments in 8*8 matrix form and showed good agreement in the image and spectrum. Finally we applied spectroscopic imaging to the brain of human subject. Only the lipid signal was shown in the periphery region which agrees with the at distribution in human head surface area. The spectrum inside the brain shows the important metabolites such as NAA, Cr/PCr, Choline. We here have shown the spectroscopic imaging which is normally done above 1.5 Tesla machine can be performed in the 1 Tesla Magnetic Resonance Imaging Unit.

• 대한의용생체공학회:의공학회지
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• 제27권2호
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• pp.53-58
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• 2006

In this study, transverse relaxation time (T2) measurement and the evaluation of the characteristics of the spectral peak related to stomach tissue metabolites were performed using ex vivo proton magnetic resonance spectroscopic imaging (MRSI) at 1.5-T MRI/S instruments. Thirty-two gastric tissues resected from 12 patients during gastric cancer surgery, of which 19 were normal tissue and 13 were cancerous tissue, were used to measure the $T_2$ of the magnetic resonance spectroscopy (MRS) peaks. The volume of interest data results from the MRSI measurements were extracted from the proper muscle (MUS) layer and the composite mucosa/submucosa (MC/SMC) layer and were statistically analyzed. MR spectra were acquired using the chemical shift imaging (CSI) point resolved spectroscopy (CSI-PRESS) technique with the parameters of pulse repetition time (TR) and echo times (TE) TR/(TE1,TE2)=1500 msec/(35 msec, 144 msec), matrix $size=24{\times}24$, NA=1, and voxel $size=2.2{\times}2.2{\times}4mm^3$. In conclusion, the measured $T_2$ of the metabolite peaks, such as choline (3.21ppm) and lipid (1.33ppm), were significantly decreased (p<0.01 and p<0.05, respectively) in the cancerous stomach tissue.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회.한국자기공명학회 2005년도 공동학술대회
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• pp.73-73
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• 2005

• Clinical and Experimental Pediatrics
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• 제55권10호
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• pp.397-402
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• 2012

Pelizaeus-Merzbacher disease (PMD) is a rare, X-linked recessive disorder characterized by dysmyelination in the central nervous system. PMD results from deletion, mutation, or duplication of the proteolipid protein gene (PLP1) located at Xq22, leading to the failure of axon myelination by oligodendrocytes in the central nervous system. PMD may be suspected when there are clinical manifestations such as nystagmus, developmental delays, and spasticity, and genetic analysis can confirm the diagnosis. Further diagnostic manifestations of the disease include a lack of myelination on brain magnetic resonance (MR) imaging and aberrant N-acetyl aspartate (NAA) and choline concentrations that reflect axonal and myelination abnormalities on phroton MR spectroscopy. We report 5 cases of PMD (in 1 girl and 4 boys). PLP1 duplication was detected in 2 patients. Brain MR analyses and MR spectroscopy were performed for all the patients. The brain MR images showed white matter abnormalities typical of PMD, and the MR spectroscopic images showed diverse patterns of NAA, creatinine, and choline concentrations. We propose that MR spectroscopic analysis of metabolic alterations can aid the PMD diagnosis and can contribute to a better understanding of the pathogenesis of the disease.

• Investigative Magnetic Resonance Imaging
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• 제16권1호
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• pp.40-46
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• 2012

목적: 폐암의 생체 수소자기공명분광법의 실행가능성을 탐색하고자 하였다. 대상과 방법: 이 전향적 연구는 해당병원의 임상시험심사위원회로 승인을 받았고 모든 환자로부터 사전동의를 받았다. 병리적으로 폐암으로 확인된 (평균 직경, 56.8 mm; 범위, 44-77 mm) 10명의 환자들에서 (남자 7명, 여자 3명; 평균나이, 64.4세) 단일 복셀 수소자기공명분광기법으로 호흡 유발 PRESS (point-resolved spectroscopic sequence)를 사용하여 1.5 T 수소자기공명 분광법을 시행하였다. 스펙트럼 습득의 기술적 성공률을 평가하고 실패한 증례들의 이유를 고찰하였다. 결과: 10개의 폐암 중 8개 폐암에서 분석 가능한 수소자기공명 분광 스펙트럼을 획득했다 (기술적 성공률, 80%). 두 개의 수소자기공명 분광 데이터는 심각한 기준치 왜곡으로 분석할 수 없었다. 대표적인 대사물질로 choline과 lipid들이 관찰되었다. 결론: 비록 제한적 수의 환자에서의 결과이지만 폐암에서 얻어진 생체 수소 자기공명 분광 스펙트럼이 분석가능하고 높은 성공률로 획득하였기 때문에 폐암 환자에서 호흡 유발 PRESS 방법을 사용한 생체 수소자기공명분광법이 실행가능하다고 판단된다.

• 대한의용생체공학회:의공학회지
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• 제31권5호
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• pp.412-416
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• 2010

In this study, we measured the chemical shift change of metabolite peaks in the brain-metabolite phantom according to the temperature variation using nuclear magnetic resonance(NMR). The temperature range in NMR system was controled from 25 to 80 (5 step) by internal temperature controller. Temperature coefficients of each metabolite peaks were also calculated from the measured chemical shift depending on the temperature. The chemical shift changes depending on temperature were validated by linear regression method for each metabolite peaks. The temperature coefficients of $_{tot}Cr$, Cho, Cr, NAA, and Lac were 0.0086, 0.0088, 0.0091, 0.0089, and 0.0088ppm/$^{\circ}C$, respectively. This study shows that chemical shift change of brain metabolite and temperature variation have linear relationship each other. This also makes authors believe that brain temperature measurement is possible using MR spectroscopic imaging technique.

• 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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• 제12권1호
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• pp.27-32
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• 2008

목적: 점구분-분광술을 이용한 여기법과 나선형 판독경사를 이용하여 삼차원 화학적변위영상을 개발하고자 하였다. 대상 및 방법: 상수 밀도를 갖는 나선형 판독경사를 디자인하는 분석식을 이용하여 스캐너에서 실시간으로 각종 지표들을 바꿀수 있도록 개발하였다 ($32{\times}32$ 행렬, $24{\times}24\;cm$ FOV). 생체내 뇌 데이터를 수집하였고 그리딩 알고리즘을 이용하여 분광학 영상을 재구성하였다. 결과: 본 연구에서 개발한 영상 기법을 이용하면, 점구분 분광술의 이점인 뇌 표면의 지방의 신호를 제거하면서 나선형 패턴이 갖는 장점들을 이용할 수 있다. 나선형 샘플링은 영상을 얻는데 걸리는 시간과 영상의 해상도를 자유로이 조절할 수 있는 유연성을 가지고 있다. 삼차원 고해상도 점구분-분광술 영상을 $5760\;cm^3$의 공간에서 얻는데 걸리는 총 시간이 12.5 분이었다. 결론: 점구분 분광술과 나선형 샘플링을 결합하여 삼차원 화학적 변위 영상을 얻는 새로운 방법을 개발하였다. 이를 통해 넓은 공간을 확보하며 동시에 지방 신호를 제거하는 기법을 사용할수 있게 되었다.

• Korean Journal of Radiology
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• 제20권6호
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• pp.916-930
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• 2019

Objective: To investigate the relationships of T₂^*-corrected 6-echo Dixon volumetric interpolated breath-hold examination (VIBE) imaging-based fat fraction (FF) and R₂^* values with bone mineral density (BMD); determine their associations with sex, age, and menopause; and evaluate the diagnostic performance of the FF and R₂^* for predicting osteopenia and osteoporosis. Materials and Methods: This study included 153 subjects who had undergone magnetic resonance (MR) imaging, including MR spectroscopy (MRS) and T₂^*-corrected 6-echo Dixon VIBE imaging. The FF and R₂^* were measured at the L4 vertebra. The male and female groups were divided into two subgroups according to age or menopause. Lin's concordance and Pearson's correlation coefficients, Bland-Altman 95% limits of agreement, and the area under the curve (AUC) were calculated. Results: The correlation between the spectroscopic and 6-echo Dixon VIBE imaging-based FF values was statistically significant for both readers (p_c = 0.940 [reader 1], 0.908 [reader 2]; both p < 0.001). A small measurement bias was observed for the MRS-based FF for both readers (mean difference = -0.3% [reader 1], 0.1% [reader 2]). We found a moderate negative correlation between BMD and the FF (r = -0.411 [reader 1], -0.436 [reader 2]; both p <0.001) with younger men and premenopausal women showing higher correlations. R₂^* and BMD were more significantly correlated in women than in men, and the highest correlation was observed in postmenopausal women (r = 0.626 [reader 1], 0.644 [reader 2]; both p < 0.001). For predicting osteopenia and osteoporosis, the FF had a higher AUC in men and R₂^* had a higher AUC in women. The AUC for predicting osteoporosis was highest with a combination of the FF and R₂^* in postmenopausal women (AUC = 0.872 [reader 1], 0.867 [reader 2]; both p < 0.001). Conclusion: The FF and R₂^* measured using T₂^*-corrected 6-echo Dixon VIBE imaging can serve as predictors of osteopenia and osteoporosis. R₂^* might be useful for predicting osteoporosis, especially in postmenopausal women.