• Investigative Magnetic Resonance Imaging
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• 제22권4호
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• pp.218-228
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• 2018

Purpose: The objective of this study is to determine the effect of physical changes on MR temperature imaging at 7.0T and to examine proton-resonance-frequency related changes of MR phase images and T1 related changes of MR magnitude images, which are obtained for MR thermometry at various magnetic field strengths. Materials and Methods: An MR-compatible capacitive-coupled radio-frequency hyperthermia system was implemented for heating a phantom and swine muscle tissue, which can be used for both 7.0T and 3.0T MRI. To determine the effect of flip angle correction on T1-based MR thermometry, proton resonance frequency, apparent T1, actual flip angle, and T1 images were obtained. For this purpose, three types of imaging sequences are used, namely, T1-weighted fast field echo with variable flip angle method, dual repetition time method, and variable flip angle method with radio-frequency field nonuniformity correction. Results: Signal-to-noise ratio of the proton resonance frequency shift-based temperature images obtained at 7.0T was five-fold higher than that at 3.0T. The T1 value increases with increasing temperature at both 3.0T and 7.0T. However, temperature measurement using apparent T1-based MR thermometry results in bias and error because B1 varies with temperature. After correcting for the effect of B1 changes, our experimental results confirmed that the calculated T1 increases with increasing temperature both at 3.0T and 7.0T. Conclusion: This study suggests that the temperature-induced flip angle variations need to be considered for accurate temperature measurements in T1-based MR thermometry.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회.한국자기공명학회 2005년도 공동학술대회
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• pp.68-68
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• 2005

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.98-99
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• 1998

In this paper, an interleaved spiral scan imaging is investigated for an ultra fast MR imaging. The interleaved spiral technique has relative advantage over single shot spiral imaging with improved resolution and less inhomogeneity-related artifact. An improved reconstruction algorithm is devised with DC-offset correction. Some preliminary experimental results are shown at 1.0 Tesla and 3.0 Tesla whole body MRI system.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.528-532
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• 1997

X-Ray Angiography has been gold standard or imaging of blood flow. However, patients have to take many risks such as catheterization procedure, iodine contrast agent and ionizing X-rays. MR Angiography has been suggested as a substitute for its non-hazard to patient. But the resolution and contrast was inferior to that of X-ray Angiography. Recently the resolution and the contrast have been much improved due to the development of fast imaging technique.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1995년도 춘계학술대회
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• pp.42-44
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• 1995

The original DANTE sequence and its variations have limitation in excitation profile (a sinc function-like excitation) due to the finite duration of the DANTE pulsetrain. This sinc function-like selection profile excites only a small fraction of the spins in the pixel thereby results in poor signal to noise ratio (only about ${\sim}1%$ of normal MR imaging sequence). Therefore, this poor signal to noise ratio (SNR) has been the main drawback of the original DANTE sequence. To improve the signal to noise ratio, phases of individual RF pulses in the DANTE pulse train were modulated so that more spins in the object were excited ($1{\sim}3$). We have introduced a new FM (Frequency Modulation) DANTE sequence and analyzed the signal intensity and excitation profiles.

• Investigative Magnetic Resonance Imaging
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• 제11권2호
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• pp.87-94
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• 2007

목적: 3T 장비의 신생아 뇌자기공명영상에서 T1 강조 고속 역전회복기법 (fast inversion recovery, FIR)과 자기화 삼차원 경사에코기법, (magnetization-prepared three dimensional gradient echo sequence, 3D GRE)을 스핀에코기법 (SE)과 비교하여 유용성을 알아보는 데 있다. 대상 및 방법: 20명의 신생아에서 T1 강조 SE, FIR, 그리고 3D GRE의 신호소음비 (SNR)와 대조소음비 (CNR)를 측정하고 시각적으로 회백질-백질 구별, 수초화 인식, 인공음영 발생을 점수화하여 비교하였다. 각 영상기법의 CNR 비교에는 Wilcoxon signed ranked test를 사용하였다. 결과: 세가지 영상기법 중 3D GRE가 가장 우수한 SNR을 보였고 CNR은 FIR과 3D GRE 모두 SE보다 우수하였으며 FIR보다 3D GRE가 더 우수하였다. 회백질-백질의 구분과 수초화 유무 역시 스핀에코보다 FIR과 3D GRE에서 더 잘 보였다. 그러나 3D GRE는 움직임에 의한 인공음영이 많았고 FIR에서 혈류에 의한 혈관의 고신호강도가 자주 발견되었다. 결론: 3T 장비에서 신생아 뇌영상을 얻을 때 FIR과 3D GRE 기법은 SE보다 좋은 T1 강조영상을 제공할 것으로 기대된다.

• 대한의용생체공학회:의공학회지
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• 제17권4호
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• pp.525-534
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• 1996

We have developed a fast steady state free precession interferometry (SSFPI) technique which is useful for the fMRl (functional Magnetic Resonance Imaging). As is known, SSFP sequence with a suitable adjustment of Vadient (readeut) allows us to measure precession angle 6 which in tw relates to the field inhomogeneity. Combining the two pulses (known as FID and Echo) in FADE (Fast Acquisition Double Echo) sequence, for example, one can obtain the interference term which is directly related to the precession angle It has been known that a fast high resolution magnetic field mapping is possible by use of the modified FADE sequence or SSFPI, and we have attempted to use the SSFPI technique for the susceptibility-induced fMRl. When the method is applied to the susceptibility effect based functional magnetic resonance imaging (fMRl), it was found that the direct susceptibility effect measurement was possible without perturbations such as the backgrounds and inflow effect. In this paper, simulation results and experimental results obtained with 2.0 Tesla MRI system are presented.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2001년도 제6차 학술대회 초록집
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• pp.109-109
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• 2001

Purpose： To assess the feasibility of sequential administration of ferumoxides and mangafodi trisodium in the same imaging protocols. Method： Thirty patients underwent double-contrast enhanced MR imaging of liver usi ferumoxides (Fe-MRI) and mangafodipir trisodium (Mn-MRI) on 1.5T GE Horizon system. In twenty patients, Mn-MRI was immediately followed by Fe-MRI. In ten patients, Fe-MR was performed first, then Mn-MRI was performed immediately, In all cases, precontras T1-weighted in-phase and opposed-phase spoiled gradient echo (GRE) images an T2-weighted fast spin-echo images (TR 4000ms, TE 102ms, ETL 8-12) were obtained Fe-MRI was performed with FSE and steady state GRE (TE 10 msec, flip angle 30 sequences. Mn-MRI was performed with in-phase and opposed-phase spoiled GR sequences. The SNR changes after the use of each contrast agents were calculated.

• 대한족부족관절학회지
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• 제7권2호
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• pp.208-217
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• 2003

Introduction: Soft-tissue impingement syndrome is now increasingly recognized as a significant cause of the chronic ankle pain. As a method to detect soft-tissue ankle impingement, a characteristic history and physical examination, routine MR imaging, and direct MR arthrography were used. The efficacy of routine MR imaging has been controversial for usefulness because of low sensitivity and specificity. Direct MR artrhography was recommaned for diagnosis because of the highest sensitivity, specificity and accuracy, but it requires an invasive procedure. The purpose of this study is to investigate the diagnostic accuracy of Fat suppressed, contrast enhanced, three-dimensional fast gradient recalled acquisition in the steady state with rediofrequency spoiling magnetic resonance imaging(CE 3D-FSPGR MRI) and to evaluate the clinical outcome of the arthroscopic treatment in assessing soft-tissue impingement associated with trauma of the ankle. Materials and Methods: We reviewed 38 patients who had arthroscopic evaluations and preoperative magnetic resonance imaging studies(3D-FSPGR MRI) for post-traumatic chronic ankle pain between January 2000 and August 2002. Among them, 24 patients had osteochondral lesion, lateral instability, loose body, malunion of lateral malleoli, and peroneal tendon dislocation. The patient group consisted of 23 men and 15 women with the average age of 34 years(16-81 years). The mean time interval from the initial trauma to the operation was 15.5 months(3 to 40 months), The mean follow-up duration of the assessment was 15.6months(12-48 months). MRI was simultaneously reviewed by two radiologists blinded to the clinical diagnosis. The sensitivity, specificity and accuracy of MRI was obtained from radiologic and arthroscopic finding. Arthroscopic debridement and additional operation for associated disease were performed. We used a standard protocol to evaluate patients before the operation and at follow-up which includes American Orthopedic Foot and Ankle Society Ankle-Hindfoot Score. Results: For the assessment of the synovitis and soft tissue impingement, fat suppressed CE 3D-FSPGR MR imaging had the sensitivity of 91.9%, the specificity of 84.4 and the accuracy of 87.5%. AOFAS Ankle-Hindfoot Score of preoperative state was 69.2, and the mean score of the last follow-up was 89.1. These were assessed as having 50% excellent(90-100) and 50% good(75-89). The presence of other associated disease didn't show the statistically significant difference(>0.05). Conclusion: Fat suppressed CE 3D-FSPGR MR imaging is useful method comparable to MR arthrography for diagnosis of synovitis or soft-tissue impingement, and arthroscopic debridement results in good clinical outcome.

• Investigative Magnetic Resonance Imaging
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• 제17권2호
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• pp.133-143
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• 2013

목적 : 직결장암 조직의 자기공명영상과 고주파 초음파검사를 시행한 후 종양의 탐지와 침윤 깊이에 대해 각각의 영상 소견과 병리 소견을 비교하여 진단적 정확도를 두 영상 기기 간 비교하고, 자기공명영상의 경우 종양의 침윤 깊이를 주변 정상 조직과 가장 명확히 보여주는 펄스 연쇄 (pulse sequence)에 대해 알아보았다. 대상 및 방법 : 직결장암으로 절제술을 시행한 45명의 환자에서 얻은 45예의 제거된 종양 조직을 수조에 넣고 생리 식염수에 담가서 고주파수 (5-17 MHz)의 선형 탐촉자를 이용하여 초음파영상을 얻었으며 8-channel 두경부 코일에 넣어 자기공명영상을 얻었다. 이 연구에 대하여 기관감사위원회의 공지에 입각한 동의는 면제되었다. 자기공명영상은 정- 및 탈위상 경사에코 T1 강조영상, 급속스핀에코 T2 강조영상 및 이의 지방억제 영상, fast imaging employing steady-state acquisition (FIESTA)와 이의 지방억제영상, 확산강조영상 등 일곱 가지 펄스 연쇄를 시행하였다. 각 조직의 자기공명영상과 초음파영상 소견을 각각 독립적으로 종양의 탐지와 침윤 깊이에 대하여 두 명의 영상의학과 의사가 합의 하에 평가하였고 각각의 영상 소견을 병리 조직 소견과 비교하여 두 영상 기기 간 진단적 정확도를 비교하였다. 자기공명영상의 일곱 가지 펄스 연쇄 중에 종양의 침윤 깊이를 주변 정상 조직과 구분하여 명확히 보여주는 펄스 연쇄에 대해 알아보았다. 결과 : 직결장암 조직의 종양 탐지와 침윤 깊이를 평가하는데 있어 자기공명영상과 초음파의 진단적 정확도는 각각 91.1%와 86.7%로 높게 나타났다. 조기 직결장암의 경우 초음파 검사의 정확도는 87.5%, 자기공명영상 검사의 정확도는 75.0%로 나왔다. 두 영상 기기 간에 통계적으로 유의한 차이는 없었다 (p > 0.05). MR의 펄스 연쇄 중에 종양의 침윤 깊이를 주변 정상 조직과 구분하여 명확하게 보여주는 영상은 직결장암 및 조기 직결장암 모두 급속 스핀에코 T2 강조영상이었다. 결론 : 자기공명영상과 초음파 검사는 직결장암 조직의 종양 탐지와 침윤 깊이를 평가하는데 높은 진단적 정확도를 가지고 있으며, 자기공명영상의 급속스핀에코 T2 강조영상이 직결장암 조직의 종양 침윤 깊이를 평가하는데 가장 우수하였다.