• 한국자기공명학회논문지
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• 제9권2호
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• pp.93-102
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• 2005

Purpose: To develop an advanced non-linear curve fitting (NLCF) algorithm for dynamic susceptibility contrast study of brain. Materials and Methods: The first pass effects give rise to spuriously high estimates of $K^{trans}$ in voxels with large vascular components. An explicit threshold value has been used to reject voxels. Results: By using this non-linear curve fitting algorithm, the blood perfusion and the volume estimation were accurately evaluated in T2*-weighted dynamic contrast enhanced (DCE)-MR images. From the recalculated each parameters, perfusion weighted image were outlined by using modified non-linear curve fitting algorithm. This results were improved estimation of T2*-weighted dynamic series. Conclusion: The present study demonstrated an improvement of an estimation of kinetic parameters from dynamic contrast-enhanced (DCE) T2*-weighted magnetic resonance imaging data, using contrast agents. The advanced kinetic models include the relation of volume transfer constant $K^{trans}\;(min^{-1})$ and the volume of extravascular extracellular space (EES) per unit volume of tissue $\nu_e$.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2003년도 제8차 학술대회 초록집
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• pp.98-98
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• 2003

We will present various MR findings of hyperacute ischemic stroke with our own experiences in the management of the patients according to the findings. 대상 및 방법： A total of 441 patients were underwent 'acute stroke MR' imaging protocol between Mar. 2001 and Jun. 2003. The protocol included initial T2-weighted image (WI), diffusion WI (DWI, b=2000), time-of-flight (TOF) MR angiography (MRA), and pefusion WI(PWI), and follow-up T2WI, DWI, TOF MRA, and neck vessel contrast-enhanced MRA obtained three to five days after the insult. Among them, we retrospectively reviewed the MR findings and clinical courses of 193 patients with anterior circulation territorial infarction. Those ICA and MCA lesions were divided into six and five groups respectively according to the level and mechanism of the occlusion. PWI findings can be another factor in the management planning.

• 대한방사선기술학회지:방사선기술과학
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• 제26권3호
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• pp.33-39
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• 2003

잡견의 간흡충증에서 조영기법의 역동적 CT 영상과 MIP 기법을 적용한 자기공명 영상의 질을 비교하여 임상적 적용 가능성을 알아보고자 하였다. 20마리의 잡견(평균 20kg)에 실험적으로 간흡충증을 유발한 후 13주 동안에 간을 중심으로 CT 영상과 MR 영상을 얻었다. CT는 이중나선식방법으로 영상을 획득하였고, bolustracking 방법으로 조영제를 주입하여 arterial phase는 5초 후에 정맥기는 동맥기 scan후 15초에 시작하여 single dynamic scan을 하고, 데이터를 다 단면 영상을 얻기 위해 MnP로 재구성을 하였다. MR 영상은 circularly polarized phased away body coil을 사용하였고, HASTE, FLASH, TSE 기법을 이용하여 모두 2차원 영상을 얻었다. HASTE와 TSE는 해상력을 증가시키기 위하여 interpolation과 지방소거기법을 적용하였다. 데이터를 획득하는 방식으로는 담관을 중심으로 3방향으로 수집한 다음 최대강도투사법으로 재구성하였다. CT와 MR 영상의 평가 방법으로서는 간내담관의 확장, 동맥기에 담관벽의 조영증강, 담관 말단부의 확장, 간의 실질조직묘사, 배경유무를 기점으로 병리학과 의사 1명과 방사선과 의사 3명, 방사선사 5명이 시각적으로 평가를 하였다. MR 영상의 경우 sequence 비교를 위해 정량적분석방법인 CNR과 CR로 평가를 하였다. 감염 후 5마리의 잡견은 죽었으며, 15마리 잡견에서 CT와 MR 검사에서 간내 담관의 만성 확장을 보여 주었다. 조영증강기법인 CT 영상에서는 간 실질조직을 비롯하여 담관벽의 조영증강이 보였고, MR 영상에서는 간내담관 형태와 담관의 말단부의 확장이 MIP 기법을 이용하여 3차원적으로 관찰되었고, CNR과 CR 값이 HASTE($16{\pm}0.83$, 73.3%), TSE($7.06{\pm}3.0$, 62.3%), FLASH($1.19{\pm}0.2$, 6.4%) 순으로 나타났다. CT와 MR 영상은 짧은 검사기법과 다양한 검사기법을 포함하고 있어 간흡충증을 영상화하는데 있어서 진단적 가치가 있다. CT와 MR 영상 검사의 장 단점을 서로 보안하여 검사를 시행한다면 높은 임상적 적용 가능성이 있다.

• Investigative Magnetic Resonance Imaging
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• 제19권3호
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• pp.146-152
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• 2015

Purpose: The purpose of this study was to evaluate the associated brain parenchymal abnormalities of developmental venous anomalies (DVA) with susceptibility-weighted image (SWI). Materials and Methods: Between January 2012 and June 2013, 2356 patients underwent brain MR examinations with contrast enhancement. We retrospectively reviewed their MR examinations and data were collected as per the following criteria: incidence, locations, and associated parenchymal signal abnormalities of DVAs on T2-weighted image, fluid-attenuated inversion recovery (FLAIR), and SWI. Contrast enhanced T1-weighted image was used to diagnose DVA. Results: Of the 2356 patients examined, 57 DVAs were detected in 57 patients (2.4%); 47 (82.4%) were in either lobe of the supratentorial brain, 9 (15.7%) were in the cerebellum, and 1 (1.7%) was in the pons. Of the 57 DVAs identified, 20 (35.1%) had associated parenchymal abnormalities in the drainage area. Among the 20 DVAs which had associated parenchymal abnormalities, 13 showed hemorrhagic foci on SWI, and 7 demonstrated only increased parenchymal signal abnormalities on T2-weighted and FLAIR images. In 5 of the 13 patients (38.5%) who had hemorrhagic foci, the hemorrhagic lesions were demonstrated only on SWI. Conclusion: The overall incidence of DVAs was 2.4%. Parenchymal abnormalities were associated with DVAs in 35.1% of the cases. On SWI, hemorrhage was detected in 22.8% of DVAs. Thus, we conclude that SWI might give a potential for understanding of the pathophysiology of parenchymal abnormalities in DVAs.

• Investigative Magnetic Resonance Imaging
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• 제1권1호
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• pp.119-124
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• 1997

목적: 뇌종양에서 자기공명 뇌혈류량지도(MR cerebral blood volume map)의 유용성을 평가하고자 하였다. 대상 및 방법: 15예의 두개강내 종괴(다형성 교모세포종 2예, 저등급 교종 3예, 뇌농양 2예, 뇌수막종 3예, 신경세포종 1예, 배아종 1예, 방사선괴사 1예, 전이암 1예) 에서 관류 MR영상을 수술전에 시행하였다. 환자의 평균연령은 42세였고(22-68), 남자 10명, 여자 5명이었다. MR영상기기는 1.5T unit(Signa, GE Medical Systems, Milwaukee, Wisconsin)를 사용하였다. 조영제 주입후 조영제의 일차 통과시 나타나는 자화율을 얻었다. (조영제는 최오의 MR 촬영시작후 10초부터 시작하여, 총량 15cc 의 Gadopentate dimeglumine(Magnevist)를 약 2ml/sec의 속도로 손으로 주입하였다). 각 환자마다 160초 동안 6 slice에서 slice당 80 image씩 총 480 image를 얻었으며 interleaved single shot gradient EPI기법을 사용하였다. 영상변수는 TR 2000ms, TE 50ms, FOV $240{\times}240mm,{\;}matrix{\;}size{\;}128{\times}128$, slice thickness/gap 5/ 2.5mm, flip angle $90^{\circ}$로 하였다. 얻은 영상데이터는 GE workstation으로 전송한 후, 자체적으로 개발한 software에 의해 각 kvoxel마다 시간경과에 따른 신호크기의 로그변화곡선(${\Delta}R2^{*}=-In(S/S_0$)의 적분값을 구하여 국소뇌혈류량(rCBV)영상을 구성하였다. 이의 시각적 해석을 용이하게 하기 위해 정상 뇌백질의 관류정도를 기준으로 하여 상대적인 RGB 색수치로 변환하여, color rCBV map을 얻었다. 관류의 정도와 조영증강정도를 중심으로 관류 MR 영상소견과 조직학적 소견을 관련지어 분석하였다. 결과: 조영증강 T1강조MR영상에서 환상조영증강을 보이는 다형성 교보세포종 2예에서는 변연부 외륜이 고관류를, 중심부의 괴사부위는 저관류로 나타났다. 저등급 교종은 경계가 불분명한 저관류부위로 보였다. 뇌농양 2예는 변연부 외륜이 경도의 고관류를, 중심부는 저관류로 나타났다. 뇌수막종은 미만성의 균일한 중등도 혹은 고도의 고관류로 보였으며, 임파종과 배아종은 경계가 명확한 저관류부위로 나타났다. 신경세포종은 종괴\ulcorner 일부에 중등도 혹은 고도의 고관류부위가 관찰되었고, 전이암은 다수병변중 일부에서 중등도의 고관류를 보였다. 방사선괴사는 저관류부위내에 국소적 고관류부위를 보였다. 결론: 관류 MR영상은 뇌종양의 관류상태를 비교적 잘 반영하며, 조직학적 특성을 예측하는데에 도움을 주 수 있을 것으로 기대된다. 뇌종야에서의 관류MR영상의 분명한 역할을 규명하기 위해서는 앞으로 더 많은 임상적 연구가 필요할 것으로 생각된다.

• 대한방사선기술학회지:방사선기술과학
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• 제38권2호
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• pp.115-120
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• 2015

Gadoxetic acid (GA) 조영증강 자기공명(MR) 영상에서 일반적으로 많이 이용되는 숙임각(flip angle, FA) $11^{\circ}$와 비교하여 FA $30^{\circ}$를 이용한 3분, 10분 및 15분 영상에서 국소성 간 병변 검출 차이를 알아보고자 하였다. 대상 및 방법 : 3.0T MR 기기로 GA 조영증강지연기 MR영상을 시행 받은 69명의 환자를 대상으로 하였다. 대상 환자는 간세포암 23명과 전이암 12명으로 총 35명(남성 23, 여성12, 평균연령 60.4세)이었다. GA 주입 후 3분, 10분, 15분의 영상에서 각각 FA $11^{\circ}$와 $30^{\circ}$ 영상을 획득하였다. 각각의 영상에서 정량적평가와 정성적평가를 한 뒤 독립표본 T검정을 이용하여 통계적 분석을 하였다. 정량적 평가와 정성적 평가 모두 조영제 주입 후 3분과 10분 영상에서 FA $30^{\circ}$ 영상이 FA $11^{\circ}$ 영상보다 약간 우수하였으나 통계적 유의성은 없었다. 그러나 15분 영상에서는 FA $30^{\circ}$ 영상이 FA $11^{\circ}$ 영상보다 통계적으로 유의하게 우수하였다(p<0.05). GA 조영증강 후 15분 MR영상에서 FA $30^{\circ}$ 영상은 기존의 FA $11^{\circ}$ 영상보다 간 병변을 민감하게 검출해낼 수 있다.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2003년도 제8차 학술대회 초록집
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• pp.97-97
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• 2003

Contrast-enhanced MR angiography (CE-MRA) gradually occupies its position as a primary evaluation tool forsteno-occlusive disease of supra-aortic cervical arteries. It has several advantages over time-of-flight (TOF) technique such as shorter imaging time, less saturation effect, and less flow- and motion-related artifacts. Diverse methods of k-space sampling, imaging sequences, and strategies for image acquisitiontiming have been introduced since its early clinical application. Especially, methods of k-space sampling and image acquisition timing are very important to achieve maximal arterial enhancement and suppress venous signal while maintaining large scan coverage and high spatial resolution. In addition, regardless of several advantages over TOF technique, it still has a tendency to overestimate the degree of stenosis in patients with carotid or vertebralartery disease. In this exhibit, we will overview the current techniques of CE-MRA with special attention to methods of k-space sampling and image acquisition timing. We will also discuss diagnostic accuracy of CE-MRA in patients with supra-aortic cervical artery stenosis and artifacts frequently misinterpreted as steno-occlusive lesion on CE-MRA.

• 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.

• 대한의용생체공학회:의공학회지
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• 제31권2호
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• pp.94-98
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• 2010

In magnetic resonance electrical impedance tomography (MREIT), a current-injection MR imaging method is adopted to produce a cross-sectional image of an electrical conductivity distribution in addition to MR images. The purpose of this study was to test the feasibility of MREIT for differentiating the canine lung parenchyma without and with pneumonia. Three normal healthy beagles and two mixed breed dogs with pneumonia were used. After attaching electrodes around the chest, we placed the dog inside our MR scanner. We injected as much as 30 mA current in a form of short pulses into the chest region. Reconstructed conductivity images of normal canine lungs exhibit a peculiar pattern of a relatively coarse salt and pepper noise. On the contrary, conductivity images of pneumonic canine lungs show significantly enhanced contrast of the lesions while the corresponding MR images show a little bit of contrast in the middle and caudal lung parenchyma due to the accumulation of pleural fluid. This preliminary study indicates that MREIT imaging of the chest may deliver unique new diagnostic information.

• Investigative Magnetic Resonance Imaging
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• 제21권2호
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• pp.71-81
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• 2017

Purpose: To compare three, motion-resistant, T1-weighted MR sequences on the hepatobiliary phase for gadoxetic acid-enhanced MR imaging of the liver. Materials and Methods: In this retrospective study, 79 patients underwent gadoxetic acid-enhanced, 3T liver MR imaging. Fifty-nine were examined using a standard protocol, and 20 were examined using a motion-resistant protocol. During the hepatocyte-specific phase, three MR sequences were acquired: 1) gradient recalled echo (GRE) with controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA); 2) radial GRE with the interleaved angle-bisection scheme (ILAB); and 3) radial GRE with golden-angle scheme (GA). Two readers independently assessed images with motion artifacts, streaking artifacts, liver-edge sharpness, hepatic vessel clarity, lesion conspicuity, and overall image quality, using a 5-point scale. The images were assessed by measurement of liver signal-to-noise ratio (SNR), and tumor-to-liver contrast-to-noise ratio (CNR). The results were compared, using repeated post-hoc, paired t-tests with Bonferroni correction and the Wilcoxon signed rank test with Bonferroni correction. Results: In the qualitative analysis of cooperative patients, the results for CAIPIRINHA had significantly higher ratings for streak artifacts, liver-edge sharpness, hepatic vessel clarity, and overall image quality as compared to, radial GRE, (P < 0.016). In the imaging of uncooperative patients, higher scores were recorded for ILAB and GA with respect to all of the qualitative assessments, except for streak artifact, compared with CAIPIRINHA (P < 0.016). However, no significant differences were found between ILAB and GA. For quantitative analysis in uncooperative patients, the mean liver SNR and lesion-to-liver CNR with radial GRE were significantly higher than those of CAIPIRINHA (P < 0.016). Conclusion: In uncooperative patients, the use of the radial GRE sequence can improve the image quality compared to GRE imaging with CAIPIRINHA, despite the data acquisition methods used. The GRE imaging with CAIPIRINHA is applicable for patients without breath-holding difficulties.