• Journal of Magnetics
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• 제17권3호
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• pp.219-224
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• 2012

In the present study, changes in signal-to-noise ratio (SNR) and apparent diffusion coefficient (ADC) of the diffusion-weighted images in the normal livers were investigated using changes in b values in 1.5 T MR (magnetic resonance) instruments. Respective diffusion-weighted images and ADC map images were obtained from 20 healthy individuals by increasing b values from 50 to 400 and 800 $s/mm^2$ using 1.5T MR scanner between January 2011 and November 2011. At each ADC map image obtained at each b value, ADCs in the right hepatic lobe, spleen and kidney were measured. As a result, ADCs of the right hepatic lobe, spleen and kidney have gradually decreased in the diffusion-weighted images in accordance with the reduced b value. This outcome may be used as preliminary data for applications to various abdominal diseases.

• 한국의학물리학회지:의학물리
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• 제21권1호
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• pp.52-59
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• 2010

요추 압박 골절이 있는 환자를 대상으로 1.5 T MR 기기에서 b value의 변화를 이용한 확산강조영상에서 압박 골절이 있는 요추의 신호대 잡음비와 현성 확산 계수가 어떤 변화를 나타내는지 알아보고자 하였다. 2008년 1월부터 2009년 11월까지 요추 MRI를 촬영한 환자 중에서 만성 골다공증으로 척추 압박 골절을 보였던 환자 30명을 대상으로 1.5T MR scanner를 이용하여 b value를 400, 600, 800, 1000, $1200\;s/mm^2$으로 점차 증가시켜가면서 확산강조영상을 각각 획득하였다. 각각의 b value로 획득한 확산강조영상에서 1~5번의 요추체중 척추 압박 골절이 있는 부위와 골절이 있는 부위의 위, 아래 추간판등 세 부위에서 신호대 잡음비를 측정하였고 각각의 b value로 획득한 ADC map 영상에서는 세 부위의 신호대 잡음비와 현성 확산 계수를 측정 하였다. 정량적 분석방법으로 b value $400\;s/mm^2$으로 획득한 확산강조영상과 ADC map영상을 기준으로 각각의 b value로 획득한 영상과 비교하였다. 정성적인 분석방법은 b value $400\;s/mm^2$ 확산강조영상과 ADC map영상의 1~5번의 요추체중 척추 압박 골절이 있는 부위의의 신호강도를 분석하여 이를 기준으로 각각의 b value를 증가시켰을 때의 확산강조영상과 ADC map영상에서 신호강도가 상대적으로 어떻게 변화하는지 알아보았다. 영상의 정량적 분석에서는 확산강조영상에서 b value가 증가함에 따라 척추 압박 골절이 있는 부위와 골절이 있는 부위의 위, 아래 추간판등 세 부위 모두 신호대 잡음비가 상대적으로 감소했다. ADC map영상에서는 b value가 증가함에 따라 척추 압박 골절이 있는 부위와 골절이 있는 부위의 위, 아래 추간판등 세 부위 모두 신호대 잡음비가 상대적으로 감소했다. ADC map영상에서 b value에 따른 관심영역의 현성 확산 계수는 b value가 증가함에 따라 척추 압박 골절이 있는 부위와 골절이 있는 부위의 위, 아래 추간판등 세 부위 모두 현성 확산 계수가 상대적으로 감소했다. 영상의 정성적 분석에서 b value를 $400\;s/mm^2$ 이상으로 증가시킴에 따라 척추 압박 골절이 있는 부위와 골절이 있는 부위의 위, 아래 추간판등 세 부위 모두 신호강도가 점차 감소하였고 b value를 $1,000\;s/mm^2$ 이상으로 했을 때에는 세 부위 모두 영상의 잡음이 매우 심했다. 또한 척추 압박 골절이 있는 부위는 상대적으로 위, 아래 추간판 보다 높은 신호강도를 보였다. 확산강조영상에서 b value를 증가시킴에 따라 척추 압박 골절이 있는 부위와 골절이 있는 부위의 위, 아래 추간판 등 세부위 모두 신호대 잡음비와 현성확산계수가 점차 감소하는 결과를 얻었고 향후 확산강조영상 검사 시 Multi b value를 사용하여 신호의 변화를 인지함으로서 여러 가지 척추질환으로의 적용에 도움을 줄 것이라 사료된다.

• Asian Pacific Journal of Cancer Prevention
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• 제16권8호
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• pp.3407-3412
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• 2015

Background: The aim of this study was to evaluate and compare the accuracy of diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC) value, and time-intensity curve (TIC) type analysis derived from dynamic contrast-enhanced MR imaging (DCE-MRI) in differentiating benign from malignant adnexal masses. Materials and Methods: 47 patients with 56 adnexal masses (27 malignant and 29 benign) underwent DWI and DCE-MRI examinations, prior to surgery. DWI signal intensity, mean ADC value, and TIC type were determined for all the masses. Results: High signal intensity on DWI and type 3 TIC were helpful in differentiating benign from malignant adnexal masses (p<0.001). The mean ADC value was significantly lower in malignant adnexal masses (p<0.001). An ADC value< $1.20{\times}10^{-3}mm^2/s$ may be the optimal cutoff for differentiating between benign and malignant tumors. The negative predictive value for low signal intensity on DWI, and type 1 TIC were 100%. The pairwise comparison among the receiver operating characteristic (ROC) curves showed that the area under the curve (AUC) of TIC was significantly larger than the AUCs of DWI and ADC (p<0.001 for comparison of TIC and DWI, p<0.02 for comparison of TIC and ADC value). Conclusions: DWI, ADC value and TIC type derived from DCE-MRI are all sensitive and relatively specific methods for differentiating benign from malignant adnexal masses. By comparing these functional MR techniques, TIC was found to be more accurate than DWI and ADC.

• Journal of Magnetics
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• 제22권1호
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• pp.146-149
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• 2017

In this study, we compared the standardized value of each signal intensity, the apparent diffusion coefficient (ADC) that digitizes the diffusion of water molecules, and the signal to noise ratio (SNR) using b value 0 400, 1400 ($s/mm^2$). From March 2013 to December 2013, patients with suspicion of simple compound fracture and metastatic spine cancer were included in the MR readout. We used a 1.5 Tesla Achieva MRI system and a Syn-Spine Coil. Sequence is a DWI SE-EPI sagittal (diffusion weighted imaging spin echo-echo planar imaging sagittal) image with b-factor ($s/mm^2$) 0, 400, 1400 were used. Data analysis showed ROI (Region of Interest) in diseased area with high SI (signal intensity) in diffusion-weighted image b value 0 ($s/mm^2$) Using the MRIcro program, each SI was calculated with images of b-value 0, 400, and 1400 ($s/mm^2$), ADC map was obtained using Metlab Software with each image of b-value, The ADC is obtained by applying the ROI to the same position. The standardized values ($SI_{400}/SI_0$, $SI_{400}/SI_0$) of simple compression fractures were $0.47{\pm}0.04$ and $0.23{\pm}0.03$ and the standardized values ($SI_{400}/SI_0$, $SI_{400}/SI_0$) of the metastatic spine were $0.57{\pm}0.07$ and $0.32{\pm}0.08$ And the standardized values of the two diseases were statistically significant (p < 0.05). The ADC ($mm^2/s$) for b value 400 ($s/mm^2$) and 1400 ($s/mm^2$) of the simple compression fracture disease site were $1.70{\pm}0.16$ and $0.93{\pm}0.28$ and $1.24{\pm}0.21$ and $0.80{\pm}0.15$ for the metastatic spine. The ADC ($mm^2/s$) for b value 400($s/mm^2$) was statistically significant (p < 0.05) but the ADC ($mm^2/s$) for b value 1400 (p > 0.05). In conclusion, multi - b value recognition of signal changes in diffusion - weighted imaging is very important for the diagnosis of various spinal diseases.

• Investigative Magnetic Resonance Imaging
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• 제18권1호
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• pp.25-33
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• 2014

목적: 확산강조영상 (DW-MRI)과 역동적 조영증강 자기공명영상 (DCE-MRI)에서 도출한 정량적 매개변수들이 서로 연관되어 있는지 알아보고자 하였다. 대상과 방법: 치료시작 전 DWI와 DCE-MRI를 시행한 조직학적으로 혹은 임상적으로 진단된 골전이암을 가진 13명의 환자를 대상으로 하였다. 주 병변의 겉보기 확산계수 (ADC) 그리고 관류지수 중 $K^{trans}$와 $V_e$ 값을 측정하여 Pearson 연관분석을 사용하여 통계적으로 분석하였다. 결과: 15개의 병변 중 11개는 ADC와 $K^{trans}$ 값 간에 유의한 상관관계를 보였다. 이 중 7개의 병변은 음의 연관성을, 그리고 4개는 양의 연관성을 보였다. 9개의 병변은 ADC와 $V_e$ 값 간에 유의한 상관관계를 보였다. 이 중 4개는 음의 연관성을, 그리고 5개는 양의 연관성을 보였다. 결론: 골전이암의 ADC 값과 $K^{trans}$ 값, 혹은 ADC 값과 $V_e$ 값은 일정한 연관성이 없었다.

• 대한디지털의료영상학회논문지
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• 제14권1호
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• pp.21-29
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• 2012

The purpose of this study is to evaluate the mutual relations by measuring SNR from T2 weighted image and ADC values on the basis of the stiffness values from liver tissues. This study was conducted that total 37 people(23 of males and 11 of females) were taken the liver MRI examination and average age was $54.5{\pm}12.7$ years old. The equipment was MAGNETOM Skyra 3.0T (SIEMENS, Erlangen, Germany) and 32 channel body-array coil. The examination were conducted with HASTE T2 weighted image by axial plane, Spin-echo EPI (echo planner image) DWI (b-value = 800) and Magnetic resonance elastography. The ROIs (region of interest: 200-300 $mm^2$) were established on the basis of the first axial stiffness image corresponded 95% confidence interval from axial stiffness image and then were measured values. After drawing the grid lines, signals were measured SNR from T2 weighted image and ADC values on the same locations that were analysed other 3 planes respectively. The results were showed correlation (0.057) that were increased to SNR from T2 weighted image by increasing stiffness value that no significant difference statistically p = 0.003. Other results were showed correlations (-0.301) that were decreased to ADC values by increasing stiffness values that no significant difference statistically p = 0.088. In the 3.0T equipment, the results may be error in much the same fashion as the 1.5T from ADC values by evaluation of fibrosis stage. However, Magnetic resonance elastography would be useful method that is used to diagnose exactly liver fibrosis stages in the 3.0T.

• Journal of Korean Neurosurgical Society
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• 제41권6호
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• pp.371-376
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• 2007

Objective : The aim of this study was to investigate the usefulness of diffusion-weighted imaging [DWI] and apparent diffusion coefficiency [ADC] in distinguishing brain abscesses from cystic or necrotic brain tumors, which are difficult to be differentiated by conventional magnetic resonance imaging techniques. Methods : Seven patients with brain abscesses and ten patients with cystic brain tumors were studied from September 2003 to October 2005. Abscess, subdural empyema and ventriculitis were categorized to the abscess group and cystic or necrotic brain gliomas or metastatic brain tumors into the tumor group. Preoperative magnetic resonance images were performed in all patients and diffusion-weighted images and apparent diffusion coefficiency values of lesions were calculated directly from software of 1.5 tesla MRI [General Electrics, USA]. The ratio of the ADC of the lesion to contralateral regional ADC was also measured [relative ADC, rADC]. Results : The average ADC value of pyogenic abscesses group was $0.82+/-0.14{\times}10^{-3}\;[mean+/-S.D.]\;mm^2/s$ and mean rADC was 0.75. Cystic or necrotic areas had high ADC values [$2.49+/-0.79{\times}10^{-3}\;mm^2/s$, mean rADC=2.14]. ADC and rADC values of abscesses group showed about three times lower values than those of cystic or necrotic tumor group. Conclusion : This study results based on numerical comparison of signal intensities and quantitative analysis to distinguish between brain abscess and cystic or necrotic tumor, DWI and ADC mapping are thought to be very useful diagnostic tools.

• 한국방사선학회논문지
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• 제12권6호
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• pp.755-762
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• 2018

유방암을 진단받고 수술 전 확산텐서영상에서 도출된 정량적 확산 지표인 비등방성 확산의 크기(FA)와 현성 확산계수(ADC) 값을 비교하고, 상관관계를 분석하여 보기로 하였다. 확산 그레디언트는 20방향(b-value, 0 및 $1,000s/mm^2$)을 사용하여 정량적 확산 지표를 도출하였다. 정량적 분석은 피어슨의 상관분석, 정성적 분석은 급내 상관계수를 적용하여 분석하였다. 연구 결과는 FAmin, FAmean, FAmax 평균값은 $0.098{\pm}0.065$, $0.302{\pm}0.142$, $0.634{\pm}0.236$이고 ADCmin, ADCmean, ADCmax은 $0.741{\pm}0.403$, $1.095{\pm}0.394$, $1.530{\pm}0.447$로 나타났다(p > 0.05). 병변 평가에서 Category 6이면서 시간대 신호 강도 그래프가 유실형(Pattern III)의 경우는 $FA_{min}$, $FA_{mean}$, $FA_{max}$ 평균값은 $0.132{\pm}0.050$, $0.418{\pm}0.094$, $0.770{\pm}0.164$이고 $ADC_{min}$, $ADC_{mean}$, $ADC_{max}$는 $0.753{\pm}0.189$, $1.120{\pm}0.236$, $1.615{\pm}0.372$로 나타났다. 정량적 분석 결과 $ADC_{mean}-FA_{mean}$, $ADC_{maximal}-FA_{max}$는 음의 상관관계가 나타났다(p = 0.001, 0.003). 정성적 분석 결과 내부 평가자의 경우 ADC 0.628(p = 0.001), FA 0.620(p = 0.001)이고, 외부 평가자의 경우 ADC 0.677(p = 0.001), FA 0.695(p = 0.001)로 나타났다. 결론적으로 형태학적 조직 검사를 바탕으로 동적 조영 검사에서 시간대 신호 강도 그래프는 유실(pattern III: wash out) 형태이며, $ADC_{mean}$ $1.120{\pm}0.236$, $FA_{mean}$값이 $0.032{\pm}0.142$로 피어슨 상관분석의 결과 음의 상관관계(Y=1.44-1.12X)로 나타났다. 따라서, 시간대 신호강도 그래프의 형태와 ADC와 FA의 상호관계를 파악한다면 유방암에서 악성 질환을 구분하는 기준이 되리라 생각된다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(2)
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• pp.305-308
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• 2002

An 1.8V 6bit IGSPS ADC for high speed data acquisition is discussed in this paper. This ADC is based on a flash ADC architecture because the flash ADC is the only practical architecture at conversion rates of IGSPS and beyond. A straightforward 6bit full flash A/D converter consists of two resistive ladders with 63 laps, 63 comparators and digital blocks. One important source of errors in flash A/D converter is caused by the capacitive feedthrough of the high frequency input signal to the resistive reference-lauder. Consequently. the voltage at each tap of the ladder network can change its nominal DC value. This means large transistors have a large parasitic capacitance. Therefore, a dual resistive ladder with capacitor is employed to fix the DC value. Each resistive ladder generates 32 clean reference voltages which alternates with each other. And a two-stage amplifier is also used to reduce the effect of the capacitive feedthrough by minimizing the size of MOS connected to reference voltage. The proposed ADC is based on 0.18${\mu}{\textrm}{m}$ 1-poly 6-metal n-well CMOS technology, and it consumes 307㎽ at 1.8V power supply.

• 반도체디스플레이기술학회지
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• 제12권2호
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• pp.13-17
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• 2013

In lighting system where several large-area organic light-emitting diode (OLED) lighting panels are involved, panel aging may appear differently from each other, resulting in a falling-off in lighting quality. To achieve uniform light output across large-area OLED lighting panels, we have employed an optical feedback circuit. Light output from each OLED panel is monitored by the optical feedback circuit that consists of a photodiode, I-V converter, 10-bit analogdigital converter (ADC), and comparator. A photodiode generates current by detecting OLED light from one side of the glass substrate (i.e., edge emission). Namely, the target luminance from the emission area (bottom emission) of OLED panels is monitored by current generated from the photodiode mounted on a glass edge. To this end, we need to establish a mapping table between the ADC value and the luminance of bottom emission. The reference ADC value corresponds to the target luminance of OLED panels. If the ADC value is lower or higher than the reference one (i.e., when the luminance of OLED panel is lower or higher than its target luminance), a micro controller unit (MCU) adjusts the pulse width modulation (PWM) used for the control of the power supplied to OLED panels in such a way that the ADC value obtained from optical feedback is the same as the reference one. As such, the target luminance of each individual OLED panel is unchanged. With the optical feedback circuit included in the lighting system, we have observed only 2% difference in relative intensity of neighboring OLED panels.