• 대한방사선기술학회지:방사선기술과학
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• 제41권1호
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• pp.25-31
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• 2018

This study aimed to evaluate the range of maximum TE that could measure T2 relaxation time accurately by setting diverse maximum TE with using contrast medium phantoms. Contrast medium phantoms ranging from low to high concentrations were made by using Gadoteridol. The relaxation time and relaxation rate were compared and evaluated by conducting T2 mapping by using reference data based on various TEs and data obtained from different maximum TEs. It was found that accurate T2 relaxation time could be expressed only when the maximum TE over a certain range was used in the section with long T2 relaxation time, such as the low concentration section of saline or gadolinium contrast medium. Therefore, the maximum TE shall be longer than the T2 relation time for accurately maturing the T2 relaxation of a certain tissue or a substance.

• 대한디지털의료영상학회논문지
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• 제15권2호
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• pp.63-68
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• 2013

Purpose : The relaxation times of tissue in MRI depend on strength of magnetic field, morphology of nuclear, viscosity, size of molecules and temperature. This study intended to analyze quantitatively that materials' temperatures have effects on T1 and T2 relaxation times without changing of other conditions. Materials and Methods : The equipment was used MAGNETOM SKYRA of 3.0T(SIEMENS, Erlagen, Germany), 32 channel spine coil and Gd-DTPA water concentration phantom. To find out T1 relaxation time, Inversion Recovery Spin Echo sequences were used at 50, 400, 1100, 2500 ms of TI. To find out T2 relaxation time, Multi Echo Spin Echo sequences were used at 30, 60, 90, 120, 150, 180, 210, 240, 270 ms of TE. This experiment was scanned with 5 steps from 25 to $45^{\circ}C$. next, using MRmap(Messroghli, BMC Medical Imaging, 2012) T1 and T2 relaxation times were mapped. on the Piview STAR v5.0(Infinitt, Seoul, Korea) 5 steps were measured as the same ROI, and then mean values were calculated. Correlation between the temperatures and relaxation times were analyzed by SPSS(version 17.0, Chicago, IL, USA). Results : According to increase of temperatures, T1 relaxation times were $214.39{\pm}0.25$, $236.02{\pm}0.87$, $267.47{\pm}0.48$, $299.44{\pm}0.64$, $330.19{\pm}1.72$ ms. T2 relaxation times were $180.17{\pm}0.27$, $197.17{\pm}0.44$, $217.92{\pm}0.39$, $239.89{\pm}0.53$, $257.40{\pm}1.77$ ms. With the correlation analysis, the correlation coefficients of T1 and T2 relaxation times were statistically significant at 0.998 and 0.999 (p< 0.05). Conclusion : T1 and T2 relaxation times are increased as temperature of tissue goes up. In conclusion, we suggest to recognize errors of relaxation time caused local temperature's differences, and consider external factors as well in the quantitative analysis of relaxation time or clinical tests.

• Investigative Magnetic Resonance Imaging
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• 제12권1호
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• pp.20-26
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• 2008

목적 : 주요 뇌 대사물질들의 T1 및 T2 이완시간들을 1.5T 및 3.0T 자기공명영상에서 산출하고 비교하여, 실제 임상응용의 기초자료로 제시하고자 하였다. 대상 및 방법 : 1.5T와 3.0T에서 N-acetyl aspartate (NAA), Choline (Cho), Creatine (Cr)을 함유한 모형을 이용하여 STEAM (STimulated Echo-Acquisition Mode)방법으로 반복시간 (Repetition time)을 5000 ms, 에코시간 (Echo time)을 20 ms로 고정한 후 혼합시간 (Mixing time)을 11단계로 변화시켜서 획득된 스펙트럼들에서 뇌 대사물질들의 T1 이완시간을 산출하였으며, PRESS (Point-REsolved SpectroScopy)방법으로 반복시간을 3000 ms에 고정시킨 후 에코시간을 5단계로 변화시켜서 획득된 스펙트럼들에서 뇌 대사물질들의 T2 이완시간을 산출한 후 그 결과들을 1.5T와 3.0T사이에서 비교하였다. 결과 : T1 이완시간에 대하여, NAA는 1.5T에서 $2293\;{\pm}\;48\;ms$, 3.0T에서 $2559\;{\pm}\;124\;ms$로 산출되어 1.5T와 비교하여 3.0T에서 11.6% 길어졌고, Cho은 1.5T에서 $2540\;{\pm}\;57\;ms$, 3.0T에서 $2644\;{\pm}\;76\;ms$로 3.0T에서 4.1% 길어졌으며, Cr 은 1.5T에서 $2543\;{\pm}\;75\;ms$, 3.0T에서 $2665\;{\pm}\;94\;ms$로 3.0T에서 4.8% 길어졌다. T2 이완시간에 대하여, NAA는 1.5T에서 $526\;{\pm}\;81\;ms$, 3.0T에서 $468\;{\pm}\;74\;ms$로 산출되어 3.0T에서 11.0% 짧아졌고, Cho은 1.5T에서 $220\;{\pm}\;44\;ms, 3.0T에서 $182\;{\pm}\;35\;ms$로 3.0T에서 17.3% 짧아졌으며, Cr 은 1.5T에서 $289\;{\pm}\;47\;ms$, 3.0T에서 275\;{\pm}\;57\;ms$로, 3.0T에서 4.8% 짧아졌다. 결론 : 1.5T와 비교하여 3.0T에서 모형에 함유된 주요 뇌 대사물질들의 T1이완시간들은 $4.1%\;{\sim}\;11.6%$ 증가하였고, T2이완시간들은 4.8% ~ 17.3% 감소하였으므로, 자기공명분광법의 적정화를 위하여 3.0T에서 반복시간을 연장시키고, 에코시간은 단축시켜야 한다.

• Investigative Magnetic Resonance Imaging
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• 제7권1호
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• pp.39-46
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• 2003

목적 : 간(liver)과 림프절 특이성 등의 다기능성을 나타내는 미세 초상자성 산화철 입자(ultrasmall superparamagnetic iron oxide: USP IO)의 자기이완(magnetic relaxation)에 대한 이론적 모델을 제시하고 이러한 이론적 모델에 근거한 미세 초상자성 산화철 입자의 자기장의 세기에 따른 자기 이완시간의 변화를 컴퓨터 모의 실험을 통해 연구하였다. 대상 및 방법 : 초상자성 산화철 입자를 조영제로 사용하기 위해서는 생체적합성 고분자로 축약(encapsulation)시키게 되고 따라서 확산(diffusion) 및 전자스핀의 fluctuation 에 기인하여 발생하는 자유 물분자와 간접 상호작용인 "outsphere " 기전에 근거하여 자기이완모델을 개발하였다. 또한 초상자성체의 경우 자기 모멘트가 상자성 입자에 비해 최소 수백배에서 최대 수만배까지 더 크므로 일반적으로 상자성 조영제의 "out sphere" 기전에서 가정하는 저자장 근사치를 사용할 수 없고 따라서 본 연구에서는 Brillouin함수로 표현되는 총자화에 대한 표현을 적용하여 저자장뿐만 아니라 고자장의 경우까지를 모두 포함하는 "out sphere" 기전에 의한 T1 그리고 T2 이완율에 대한 모델을 개발하였다. 이렇게 개발된 자기이완모델을 사용하여 미세 초상자성 산화철 입자의 자기장의 세기에 따른 자기 이완시간의 변화를 symbolic computation tool 인 MathCad(MathCad, USA)를 사용한 컴퓨터 모의 실험을 통해 조사하였다. 결과 : 미세 초상자성 산화철 입자의 T1, T2 자기이완 특성은 먼저, 저자장 영역 (＜1.0 Mhz)에서는 이론적 모델의 spectral density function에 들어 있는 두 개의 correlation time중 $\tau$$_{s1}$ 중 (T2의 경우 ${\tau}_{S2}$)이 주된 역할을 하는 것을 알 수 있었고 이는 결과적으로 이러한 나노자성체 입자들이 낮은 자기장하에서는 열적으로 야기된 자기모멘트들의 재배열이 주된 역할을 하는 것으로 해석할 수 있다. 한편 고자장 영역에서는 correlation time 중 $\tau$가 주된 역할을 담당하는데는 $\tau$는 나노 입자의 크기와 연관되어 있으며 고자장에서 입자 크기에 따른 T1 이완율(R1)과 T2 이완율(R2)의 차이는 이러한 입자크기의 차이에 의해 발생하는 것으로 해석할 수 있다. 나노입자에 포함된 철 원자수를 변화시키는 경우 철 원자수가 증가 할 수록 R1과 R2가 증가하는 결과를 나타내었다. 한편 온도변화에 따른 T1, T2 자기이완시간의 변화는 정상체온 근처의 제한적인 온도범위내에서 저자장 영역에서의 아주 작은 변화를 제외하고는 큰 차이를 보이지 않았으나 T1에 비해 T2에서 이러한 변화가 상대적으로 더 작게 나타났다. 결론 : 임상적 다기능성을 나타낼 가능성이 많은 것으로 보고되고 있는 미세 초상자성 산화철 입자의 자기이완에 대한 이론적 모델을 초상자성 나노입자의 물리적 특성에 기초하여 제시하였고 이러한 이론적 모델에 근거한 미세 초상자성 산화철 입자의 자기장의 세기에 따른 자기 이완시간의 변화를 컴퓨터 모의 실험을 통해 조사하였다.다.

• 대한방사선기술학회지:방사선기술과학
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• 제41권2호
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• pp.103-107
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• 2018

In MR, the iodine CT contrast medium reduces the T1 and T2 relaxation times of the substance, resulting in a change in signal intensity. This study aimed to measure the relaxation rate of MR contrast medium with or without diluting CT contrast medium and analyzed the effect of CT contrast medium. Undiluted Gadoteridol solution was diluted with saline to prepare MR contrast medium phantoms with various levels of Gadoteridol concentrations. Moreover, undiluted Iomeprol was mixed with the prepared MR contrast medium phantoms at 1:1 ratio to make MR contrast medium phantoms with containing CT contrast medium for the experiment. T1 and T2 mappings were conducted to quantitatively evaluate the relaxation time and relaxation rate of these phantoms. The results showed that the T1 and T2 relaxation time and relaxation rate of MR contrast medium diluted with CT contrast medium were significantly (p<0.05) shorter than those of MR contrast medium not diluted with CT contrast medium. The results of this study imply that, when MR contrast medium shall be used after injecting CT contrast medium, CT contrast medium should be discharged enough. Moreover, it would be desirable to conduct CT test after taking MRI test in order to reduce the effects of CT contrast medium on MR contrast medium.

• 한국초전도ㆍ저온공학회논문지
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• 제25권3호
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• pp.28-33
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• 2023

Magnetic relaxation properties of pure MgB₂ powder samples and diluted water-treated MgB₂ powder samples were investigated. The magnetic field H-dependence, m(H), and the time t-dependence, m(t), of the magnetic moment m were measured and analyzed using the PPMS-VSM magnetometer equipment, respectively. The m(t) reduction rates of pure MgB₂ powder samples and diluted water-treated MgB₂ powder samples decreased to about 0.7 ~ 1.8% and 0.6 ~ 1.0% for about 7200 s, respectively, at temperature T = 15 K. The magnetic relaxation properties of the two types of MgB₂ powders were analyzed by calculating the magnetic relaxation rate S = -dln(M_irr)/dln(t) values according to Anderson-Kim theory. The magnetic relaxation ratio S values of the two types of MgB₂ powder samples were almost similar. As a result of the quantum creep effect, the constant magnetic relaxation rate S characteristic was confirmed at a temperature range of T = 10 K or less.

• 대한의용생체공학회:의공학회지
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• 제26권2호
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• pp.87-93
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• 2005

A new method for real-time estimating left ventricular relaxation time constant (T) from the left ventricular (LV) pressure waveform, based on the isovolumic relaxation model, is proposed. The presented method uses a recursive least squares (RLS) algorithm to accomplish real-time estimation. A new criterion to detect the end-point of the isovolumic relaxation period (IRP) for the estimation of T is also introduced, which is based on the pattern analysis of mean square errors between the original and reconstructed pressure waveforms. We have verified the performance of the new method in over 4,600 beats obtained from 70 patients. The results demonstrate that the proposed method provides more stable and reliable estimation of τ than the conventional 'off-line' methods.

• 한국자기공명학회논문지
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• 제14권1호
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• pp.9-17
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• 2010

The water proton relaxation rates increase linearly with concentrations of contrast agents, and could be expressed as a function of the concentrations. In this paper, we have investigated MR properties of two different contrast agents, $GdCl_3$ and $CoCl_2$. Relaxivity coefficients were calculated from individual contrast agent solutions, and used for predicting relaxation rates at mixtures of two contrast agents. From the experimental results, we have discussed the feasibility of constructing water solutions with the desired relaxation times using specific mixtures of contrast agents.

• Food Science and Biotechnology
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• 제17권5호
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• pp.895-898
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• 2008

The mobility of water in set yogurt during fermentation was studied using nuclear magnetic resonance (NMR) relaxometry. The spin-spin relaxation was analyzed using a 2-fraction model, resulting in 2 spin-spin relaxation time constants $T_{21}$ and $T_{22}$. Both $T_{21}$ and $T_{22}$ exhibited rapid changes between 2 and 4 hr of fermentation, coinciding with the drop in pH and the rise in lactic acid bacteria count. The spin-lattice relaxation time $T_1$ increased over the fermentation period. Both $T_1$ and $T_2$ showed an increase in the mobility of water upon gel formation during fermentation. Water redistribution within the gel matrix due to casein aggregation and structure forming may be responsible for the changes in mobility.

• 대한간호
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• 제31권2호
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• pp.70-85
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• 1992

Relaxation technique is an independent nursing intervention used in various stressful situations. The concept of relaxation must be explored for the meaning given by the people in their traditional thought and philosophy. Korean relaxation technique, wanting to become culturally acceptable and effective, is learning to recognize and develop Korean concepts, experiences, and musics of relaxation. This study was aimed at discovering Korean concepts, experiences and musics of relaxation and contributing the development of the relaxation technique for Korean people. The subjects were 59 mursing students, 39 hospitalized patients, 61 housewives, 21 rural residents and 16 researchers. Data were collected from September 4th to October 24th, 1991 by interviews or questionaires. The data analysis was done by qualitative research method, and validity assured by conformation of the concept and category by 2nursing scientists who had written a Master's thesis on the relaxation technique. The results of the study were summerized as follows; 1. The meaning of the relaxation concept; From 298 statements, 107 concepts were extracted and then 5 categories "Physical domain", "Psychological domain", "Complex domain", "Situation", and "environment" were organized. 'Don't have discomforts, 'don't have muscle tension', 'don't have energy(him in Korean)', 'don't have activities' subcategories were included in "Physical domain". 'Don't have anxiey', 'feel good', 'emotional stability', 'don't have wordly thoughts', 'feel one's brain muddled', 'loss of desire' subcategories were included in "physical domain" 'Comfort body and mind', 'don't have tension of body and mind', 'be sagged' 'liveliness of thoughts' subcategories were included in "Complex domain". 'Rest', 'sleep', 'others' subcategories were included in "Situation domain". And 'quite environment' & 'comfortable environment' subcategories were included in "Environmental domain". 2. The experiences of the relaxation; From 151 statements, 59 experiences were extracted. And then 9 categories-at rest after physical activities, after problem solving, fancy, bathing in the bed, situation, rest, particular time, others-were organized. 3. The musics of the relaxation; From 229 statements, 108 musics were extracted. and the 9 categories- Western classical music, semi classical music, Korean song, Korean popular classical music, song, western popular sonhg, hymn, characteristics of music, others - were organized. In conclusion, There are some differences between Korean concepts, experiences and musics of relasation and western concepts, experiences and musics of relaxation.