• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.96-97
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• 1998

3D TOF MR Angiography is able to obtain thinner slice thickness, higher SNR, therefore higher spatial resolution than 2D TOF MR Angiography. Since it uses longer TR than 2D TOF MRA to allow stronger in-flow effect, the background tissue may not be fully saturated. Thus background tissue signal can be further suppressed by MTS(Magnetization Transfer Saturation). Flow-compensation was accomplished by GMN(Gradient Moment Nulling), and tracking saturation was used to suppress vein signal. The different flow signal at the entry of the slab and output of the slab can be compensated by TONE(Tilted Optimized Non-saturating Excitation) RF pulse.

• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.148-148
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• 2001

목적： 자기 공명 혈관 영상(MR Angiography)법으로 혈관 촬영시, 혈관 협착으로 인하여 난류 현상이 발생되는 곳에서는 영상 자체가 얻어지지 않는다. 기존에 TE를 줄이거나 또는 projection reconstruction 방법은 2차원 TOF(Time of Flight)에 적용이 되어서 좋은 결과를 얻었다. 그런데, 2차원 TOF보다는 3차원 TOF으로 보다 좋은 혈관 영상을 얻을 수가 있다. 하지만, 3차원 TOF 방법에 projection reconstruction 방법을 적용하는 데는 여러 가지 문제점이 있어서 개발되어 있는 것이 거의 없다. 본 연구에서는 3차원 TOF 방법에 projection reconstruction 방법을 적용하여서 혈관내의 난류 현상에 의한 영상의 왜곡을 극복하는 방법을 개발한다. 대상 및 방법： 3차원 projection reconstruction을 위한 pulse sequence를 실제 진단에 사용하는 GE사의 자기공명영상장치(1.5T)에 맞게 독자적으로 개발한다. GE사의 장비에서 자료를 얻어서 일반 컴퓨터에서 영상을 재구성하는 알고리즘을 자체 개발한다. 혈관에서와 비슷한 형태의 난류를 발생시킬 수 있는 기구를 만들어서 실제 혈관영상에 사용하는 방법과 개발한 방법으로 영상을 비교한다.

• Proceedings of the KSMRM Conference
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• 1997.10a
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• pp.19-19
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• 1997

• Proceedings of the KSMRM Conference
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• 2000.11a
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• pp.29-29
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• 2000

• Proceedings of the KSMRM Conference
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• 1999.11a
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• pp.45-45
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• 1999

• Investigative Magnetic Resonance Imaging
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• v.2 no.1
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• pp.96-103
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• 1998

Purpose : To assess the clinical utility of turbo contrast-enhanced magnetic resonance angiography(CE MRA) in the evaluation of the aortic arch and its major branches and to compare the image quality of CE MRA among different coils used. Materials and Methods : Turbo three-phase dynamic CE MRA encompassing aortic arch and its major branches was prospectively performed after manual bolus IV injection of contrast material in 29 patients with suspected cerebrovascular diseases at 1.0T MR unit. the raw data were obtained with 3-D FISH sequence (TR 5.4ms, TE 2.3ms, flip angle 30, slab thickness 80nm, effective slice thickness 4.0mm, matrix size $100{\times}256$, FOV 280mm). Total data acquisition time was 4. to 60 seconds. We subjectively evaluated the imge quality with three-rating scheme : "good" for unequivocal normal finding, "fair" for relatively satisfactory quality to diagnose 'normal' despite intravascular low signal, and "poor" for equivocal diagnosis or non-visualization of the origin or segment of the vessels due to low signal or artifacts which needs catheter angiography. At the level of the carotid bifurcation, it was compared with conventional 2D-TOF MRA image. Overall image quality was also compared visually and quantitatively by measuring signal-to-noise ratios (SNRs) of the ascending aorta, the innominate artery and both common carotid arteries among the three different coils used(CP body array(n=12), CP neck array(n=9), and head-and-neck(n=8). Results : Demonstration of the aortic arch and its major branches was rated as "good" in 55% (16/29) and "fair" in 34%(10/29). At the level of the carotid bifurcation, image quality of turbo CE MRA was same as or better than conventional 2D-TOF MRA in 65% (17/26). Overall image quality and SNR were significantlygreater with CP body array coil than with CP neck array or head-and-neck coil. Conclusions : Turbo CE MRA can be used as a screening exam in the evaluation of the major branches of the aortic arch from their origin to the skull base. Overall imagequality appears to be better with CP body array coil than with CP neck array coil or head-and-neck coil.

• Proceedings of the KSMRM Conference
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• 1999.11a
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• pp.105-105
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• 1999

• Proceedings of the KSMRM Conference
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• 1999.11a
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• pp.50-50
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• 1999

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.275-280
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• 2003

The method of simultaneous data acquisition of arteries and veins(SAAV) was suggested to obtain MR angiography of arteries and veins at 0.3T low filed MRI system (Magfinder, AlLab. Korea). Two separated artery- and vein-images were put together using AVCM(Artery-Vein Color Mapping) algorithm and presented in the same image. In this study, artery- and vein-separated angiograms of volunteer's neck were obtained. Two dimensioal blood-enhanced images wre sequentially obtained using SAAV pulse sequence based on time-of-flight(TOF) method with flow compensation. Imaging parameters were TR/TE=70/12msec. FOV=230mm, slice thickness = 3mm, flip angle=90$^{\circ}$, matrix size=256${\times}$256${\times}$64mm. TSat TH/SPA=15/20mm, Ts_v=10msec and Ts_a=40ms. 3D MRA images were reconstructed using the maximum intensity projection(MIP) and the artery-vein color mapping(AVCM) algorithm. This study showed good possibility of clinical applications of MRA in 0.3T which provides valuable diagnostic information of clinical vascular diseases.

• Korean Journal of Radiology
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• v.1 no.3
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• pp.142-151
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• 2000

Objective: To determine the optimal scan timing for contrast-enhanced magnetic resonance angiography and to evaluate a new timing method based on the arteriovenous circulation time. Materials and Methods: Eighty-nine contrast-enhanced magnetic resonance angiographic examinations were performed mainly in the extremities. A 1.5T scanner with a 3-D turbo-FLASH sequence was used, and during each study, two consecutive arterial phases and one venous phase were acquired. Scan delay time was calculated from the time-intensity curve by the traditional (n = 48) and/or the new (n = 41) method. This latter was based on arteriovenous circulation time rather than peak arterial enhancement time, as used in the traditional method. The numbers of first-phase images showing a properly enhanced arterial phase were compared between the two methods. Results: Mean scan delay time was 5.4 sec longer with the new method than with the traditional. Properly enhanced first-phase images were found in 65% of cases (31/48) using the traditional timing method, and 95% (39/41) using the new method. When cases in which there was mismatch between the target vessel and the time-intensity curve acquisition site are excluded, erroneous acquisition occurred in seven cases with the traditional method, but in none with the new method. Conclusion: The calculation of scan delay time on the basis of arteriovenous circulation time provides better timing for arterial phase acquisition than the traditional method.