• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.103-105
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• 2003

After fifteen years of development, Magnetic Resonance (MR) technology for human imaging and spectroscopy is reaching a refined state with FDA approved 3T clinical products from Siemens, GE, and Philips. Broker has cleared CE approval with a 4T system. Varian supports a 4T system platform as well. Shielded magnets are standard at 3T from GE, Oxford, Magnex, and IGC. A shielded 4T whole body magnet is available from Oxford. Stronger switched gradients and dynamic shim coils, desired at any field, areespecially useful at higher static magnetic fields B0. In addition to the higher currents required for higher resolution slice or volume selection afforded by higher SNR, whole body gradient coils will be driven at increasing slew rates to meet the needs of new cardiac applications and other requirements. For example 3T and 4T systems are now being equipped with 2kV, 500A gradient coils and amplifiers capable of generating 4G/cm in 200msec, over a 67+/-cm bore diameter. High field EPI applications require oscillation rates at 1 kHz and higher. To achieve a benchmark 0.2 ppm shim over a 30cm sphere in a high field magnet, at least four stages of shimming need to be considered. 1) A good high field magnet will be built to a homogeneity spec. falling in the range of 100 to 150 ppm over this 30cm spherical "sweet spot" 2) Most modern high field magnets will also have superconducting shim coils capable of finding 1.5 ppm by their adjustment during system installation. 3) Passive ferro-magnetic shimming combined with 4) active, high order room temperature shim coils (as many as five orders are now being recommended) will accomplish 0.2 ppm over the 30cm sphere, and 0.1 ppm over a human brain in even the highest field magnets for human studies. Safety concerns for strong, fast gradients at any B0 field include acoustic noise and peripheral nerve stimulation. One or more of the mechanical decoupling methods may lead to quieter gradients. Patient positioning relative to asymmetric or short gradient coils may limit peripheral nerve stimulation at higher slew rates. Gradient designs combining a short coil for local speed and strength with a longer coil for coverage are being developed for 3T systems. Local gradients give another approach to maximizing performance over a limited region while keeping within the physiologically imposed dB0/dt performance limits.

• Investigative Magnetic Resonance Imaging
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• v.8 no.2
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• pp.79-85
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• 2004

Purpose : To evaluate the usefulness and reproducibility of $^1H$ MRS in different 1.5 T MR machines with different coils to compare the SNR, scan time and the spectral patterns in different brain regions in normal volunteers. Materials and Methods : Localized $^1H$ MR spectroscopy ($^1H$ MRS) was performed in a total of 10 normal volunteers (age; 20-45 years) with spectral parameters adjusted by the autoprescan routine (PROBE package). In all volunteers, MRS was performed in a three times using conventional MRS (Signa Horizon) with 1 channel coil and upgraded MRS (Echospeed plus with EXCITE) with both 1 channel and 8 channel coil. Using these three different machines and coils, SNRs of the spectra in both phantom and volunteers and (pre)scan time of MRS were compared. Two regions of the human brain (basal ganglia and deep white matter) were examined and relative metabolite ratios (NAA/Cr, Cho/Cr, and mI/Cr ratios) were measured in all volunteers. For all spectra, a STEAM localization sequence with three-pulse CHESS $H_2O$ suppression was used, with the following acquisition parameters: TR=3.0/2.0 sec, TE=30 msec, TM=13.7 msec, SW=2500 Hz, SI=2048 pts, AVG : 64/128, and NEX=2/8 (Signa/Echospeed). Results : The SNR was about over $30\%$ higher in Echospeed machine and time for prescan and scan was almost same in different machines and coils. Reliable spectra were obtained on both MRS systems and there were no significant differences in spectral patterns and relative metabolite ratios in two brain regions (p>0.05). Conclusion : Both conventional and new MRI systems are highly reliable and reproducible for $^1H$ MR spectroscopic examinations in human brains and there are no significant differences in applications for $^1H$ MRS between two different MRI systems.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.5
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• pp.544-555
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• 2002

The aim of this study is to develop the $^1H$-MRS data postprocessing software for both single-voxel and multi-voxel technique, which plays and important role as a diagnostic tool in clinical field. This software is based on graphical user interface(GUI) under windows operating system of personal computer(PC). In case of single-voxel MRS, both of raw data in time-domain and spectrum data in frequency-domain are simultaneously displayed in a screen. Several functions such as DC correction, zero filling, line broadening, Lorentz-Gauss filtering and phase correction, etc. are included to increase the quality of spectrum data. In case of multi-voxel analysis, spectroscopic image reconstructed by 3-D FFT was displayed as a spectral grid and overlapped over previously obtained T1- or T2-weighted image for the spectra to be spatially registered with the image. The analysis of MRS peaks were performed by obtaining the ratio of peak area. In single-voxel method, statistically processed peak-area ratios of MRS data obtained from normal human brain are presented. Using multi-voxel method, MR spectroscopic image and metabolite image acquired from brain tumor are demonstrated.

• Proceedings of the KSMRM Conference
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• 2002.11a
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• pp.50-56
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• 2002

최근 3-4년간 MR의 hardware와 software의 급격한 발전으로 마침내 작년 말에 3.0 Tesla whole body MR 장비가 미국 FDA의 공인을 받았다. 한국에서도 일찍부터 3T MR장비의 개발이 이루어 졌고 이미 설치되어 연구와 임상이 이용되고 있다. 여러 회사에서 개발 및 연구된 전신 3.0T MR 장비가 여러가지 가능성을 보이고 임상 도입 단계에 있지만 아직까지 실지 임상에서는 뇌신경계 분야가 주류를 이루고 있다. 지금 뇌신경계 분야에서 보편적으로 늘리 사용되고 있는 1.5T MR 장비는 모든 면에서 상당히 안정적으로 임상 및 연구에 이용되고 있다. 1-2년 전만 해도 3.0 T MR기기는 뇌신경계 영역에서도 임상적으로 늘리 사용되기에는 안정적인 면에서는 1.5T 기기에 비해서 떨어지는 것이 사실이었다. 그래서 주로 연구실 영역에서 많이 이용되고 있었다. 그러나 지금 본원에 설치 완료되어 임상에 적용한지 6개월 정도 이용한 예에서 보면 (about 2300 cases/6months) hardware, software적인 면에서 아직 조금의 불편함이 있지만 많은 부분이 충분히 인지되고 개선이 가능한 부분으로 거의 불편함이 사라질 것으로 기대되고 있고, 불편함을 넘을 수 있는 여러 가지 장점이 있다고 본다. 고자장 (>3.0 T) MRI의 매력은 자장에 비례적으로 SNR, spectral resolution이 높아지고, T1, BOLD등에 의한 대조도가 향상한다는 것이다. SNR의 증가는 temporal, spatial 분해능을 증가시키고, spectral resolution이 높아짐에 따라 MR spectroscopy상에서 주요 대사물질 이외 작은 대사물질에 관한 스펙트럼의 분석을 향상시킨다. 이처럼 고자장 MR은 근본적인 장점을 가지고 있고 이러한 장점이 고자장 MR 시대로 가야 할 이유을 모두 설명하고 있다고 생각된다.세포질등이 있으며, 이들중에서 lysosomes, peroxisomes, 그리고 미토콘드리아가 특정한 유전성 백질질환에 중요한 역할을 하는 것이 밝혀졌다. 이러한 질환들은 최소한 각 소기관에 의한 질환군으로 분류될 수 있다.SXR이 ER의 transactivation 효과를 약간 촉진한 반면 MDA-MB-231세포는 SXR을 제외한 CAR와 PPAR${\gamma}$에 의해 ER의 transactivation 효과가 약간 증가되는 경향을 보였다. 이러한 결과는 유방암세포에서는 CAR, SXR, PPAR${\gamma}$과 같은 xenobiotic nuclear receptor에 의한 ER transactivation 효과가 간암세포와는 다르게 나타나며, 유방암의 종류에 따라서 endogenous CAR, SXR, PPAR${\gamma}$수용체가 다르게 발현됨으로써 이들에 대한 반응이 서로 상이한 특징을 나타낼 수 있을 것으로 사료된다. 따라서 estrogen receptor에 의해 매개되는 estrogn의 전사활성조절기전이 표적세포에 따라 다른 경로를 포함 할 수 있음을 시사한다.서 흡착 능력이 우수하게 나타났으며, 황화수소는 펄라이트, 왕겨, 소나무수피에서 상대적으로 우수한 것으로 나타났으며, 혼합충전재는 암모니아의 경우 코코넛과 펄라이트의 비율이 7：3인 혼합 재료 3번과 소나무수피와 펄라이트의 비율이 7：3인 혼합 재료 6번에서 다른 혼합 재료에 비하여 우수한 것으로 나타났다. 4. 코코넛과 소나무수피의 경우 암모니아 가스에 대한 흡착 능력은 거의 비슷한 것으로 사료되며, 코코넛의 경우 전량을 수입에 의존하고 있다는 점에서 국내 조달이 용이하며, 구입 비용도 적게 소요되는 소나무수피를 사용하는 것이 경제적이라고 사료된다. 5. 마지막으로 악취제거 미생물균주를 접종한 소나무수피 50%와 펄라이트

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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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.

• Investigative Magnetic Resonance Imaging
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• v.3 no.2
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• pp.146-153
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• 1999

Purpose : To evaluate the proton MR spectroscopy (MRS) findings of early and late ischemic infarcts and to compare these MRS findings with clinical symptoms. Materials and Methods : We obtained MRs spectra of 28 consecutive patients with early ischemic infarct (15 me, 13 women) between 2-10 (mean 6.2) days after stroke onset. Follow-up MRS was carried out between 20-32 (mean 25) days in 12 patients. The MRs spectra were acquired at 1.5T MR unit using single voxel technique with PRESS sequence, TR of 2000ms, TE of 288 (144)ms, and voxel size of 2cm x 2cm x 2cm in the three areas; an infarct lesion, the brain parenchyma adjacent to the lesion, and contralateral normal brain parenchyma. The NAA/creatine, choline/creatine, and lactate/creatine ratios were calculated in each spectrum. The spectra of MRS were compared with clinical symptoms. Results : In early infarct, decreased NAA/creatine ratio (n=22) and increased lactate/creatine ratio (n=25) were found in the infarct lesion. Choline/creastine ratio was within normal range (n=25). On follow-up MRS in late stage, NAA/creatine ratio in the infarct lesion decreased further (n=5), did not change (n=6), or increased (n=1). Lactate/creatine ratio became less elevated (n=10), or did not changed (n=2). Choline/creatine ratio had a trend for increase. The decreased NAA/creatine and increased lactate/creatine ratios were correlated well with the severity of symptoms, respectively. Conclusion : Decreased NAA/creatine and increased lactate/creatine ratios were common MRS findings characteristic in early ischemic infarct and correlated well with clinical severity. On follow-up MRS in late stage, NAA/creatine ratio decreased further or did not change, and lactate/creatine ratio became less elevated.

• The Korean Journal of Nuclear Medicine
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• v.34 no.6
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• pp.465-477
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• 2000

Purpose: Thallim-201 ($^{201}Tl$) brain SPECT and proton ($^1H$) magnetic resonance spectroscopy (MRS) have been used to evaluate tumor grade and viability of glioma. We assessed the correlations between $^{201}Tl$ brain index or spectrum of metabolites of $^1H$ MRS and grade of glioma or histopathologic findings. Materials and Methods: We studied 17 patients (4 astrocytoma, 7 anaplastic astrocytoma and 6 glioblastoma). On $^{201}Tl$ Brain SPECT, $^{201}Tl$ index was measured as the ratio of average counts for region of interest to those for the contralateral normal brain. On $^1H$ MRS, we calculated choline (Cho) /creatine (Cr) ratio and N-acetylaspartate (NAA)/Cr ratio in ROI defined as tumor center. Histopathologic findings were graded by Ki-67 index, cellularity, mitosis, pleomorphism, necrosis and endothelial proliferation. An unpaired t test and statistical correlations were performed to evaluate these data. Results: Tl-index showed the best correlation with Ki-67 index (p<0.01), less correlations with cellularity, mitosis, and endothelial proliferation, but no correlation with results of MRS, pleomorphism, or necrosis. The findings of MRS did not correlate with all of the above. The cases of glioblastoma demonstrated a higher Tl-index, Cho/cr ratio, Ki-67 index and lower NAA/Cr ratio, albeit without statistical significance. Conclusion: Even though $^{201}Tl$ brain SPECT did not correlate directly with grade of malignancy, it may still be useful in determining biological aggressiveness of tumor and prognosis of patients because it correlated well with Ki-67 index, a growth fraction of glioma, cellularity, mitosis and endothelial proliferation.

• Progress in Medical Physics
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• v.17 no.2
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• pp.83-88
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• 2006

Purpose: We Investigated to achieve high resolution magnetic resonance (MR) Imaging and spectra of human skin in vitro with using a 14.1 T MRI/MRS system, and to evaluate the hydration effect of a moisturizer by measuring the skin's water concentration. Materials and Methods: We used the Brukrer 14.1 T MRI/MRS system with a vertical standard bore that was equipped with a DMX spectrometer gradient system (200 G/cm at a maximum 40 A), RF resonators (2, 5 and 10 mm) and Para Vision software. Spin echo and fast spin echo pulse sequences were employed for obtaining the high resolution MR images. The 3D-localized point resolved spectroscopy (PRESS) method was used to acquire the MR spectra. Results: The high resolution MR images and spectra of human skin in vitro were successfully obtained on a 14.IT system. The water concentration of human skin after applying a moisturizer was higher than that before applying a moisturizer. Conclusions: The present study demonstrated that the high-resolution MR images and spectra of human skin from a high field MRS instrument could be applicable to evaluating the hydration state of the stratum corneum.

• Investigative Magnetic Resonance Imaging
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• v.12 no.1
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• pp.33-39
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• 2008

Purpose : There is debate concerning the observation of metabolite changes on MRS at the designated cortex during some tasks. The purpose of this study is to assess the change of the lactate content at the motor cortex during hand-grasping tasks with performing real-time fMRI-guided fMRS. Materials and Methods : Seven healthy volunteers (23-28 years old) underwent realtime fMRI during right hand grasping tasks with using a 1.5 T system. After confirming the activating area, single voxel MRS was preformed at 1) the baseline, 2) during the task and 3) after the task on the activating cortex. The three consecutive spectra were compared for observing the changes of the lactate content by the tasks. The Cho/Cr, NAA/Cr and Lac/Cr ratios were calculated manually from those spectra. Results : MRS during the tasks revealed the lactate peaks at the 1.33 ppm resonance frequency with great conspicuity at the activated area, which was identified on the real-time fMRI. After the task scan, the lactate peaks completely disappeared and the spectra recovered to the values of the baseline scan in all volunteers. At baseline, during the task and after the task, the Cho/Cr ratios were 0.81, 0.76 and 0.77, respectively, and the NAA/Cr ratios were 1.68, 1.65 and 1.72, respectively, and the Lac/Cr ratios were 0.28, 0.41 and 0.30, respectively. During the task, Lac was significantly increased by 46%. Conclusion : We observed prominent lactate peaks on MRS during hand-grasping tasks at the activated area, as was shown on the real-time fMRI. We suggest that fMRS can be used as a sensitive tool for observing the metabolite changes of the functioning brain.

• Korean Journal of Radiology
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• v.20 no.6
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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.