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Publications (4)26.12 Total impact

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    ABSTRACT: Coronary in-stent restenosis cannot be directly assessed by magnetic resonance angiography (MRA) because of the local signal void of currently used stainless steel stents. The aim of this study was to investigate the potential of a new, dedicated, coronary MR imaging (MRI) stent for artifact-free, coronary MRA and in-stent lumen and vessel wall visualization. Fifteen prototype stents were deployed in coronary arteries of 15 healthy swine and investigated with a double-oblique, navigator-gated, free-breathing, T2-prepared, 3D cartesian gradient-echo sequence; a T2-prepared, 3D spiral gradient-echo sequence; and a T2-prepared, 3D steady-state, free-precession coronary MRA sequence. Furthermore, black-blood vessel wall imaging by a dual-inversion-recovery, turbo spin-echo sequence was performed. Artifacts of the stented vessel segment and signal intensities of the coronary vessel lumen inside and outside the stent were assessed. With all investigated sequences, the vessel lumen and wall could be visualized without artifacts, including the stented vessel segment. No signal intensity alterations inside the stent when compared with the vessel lumen outside the stent were found. The new, coronary MRI stent allows for completely artifact-free coronary MRA and vessel wall imaging.
    Circulation 04/2005; 111(8):1019-26. · 15.20 Impact Factor
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    ABSTRACT: The objective of this study was to investigate the potential for artifact-free coronary magnetic resonance angiography (cMRA) in the presence of dedicated metallic MR stents in vitro and in a swine model. All investigations were performed at 1.5 T, applying a standard cMRA gradient echo sequence with a T2 preparation pulse. Two prototypes of each hand-woven, mechanically woven, and lasered Aachen Resonance Coronary MR Stents made out of an MR-compatible metallic alloy and dilated to 2.5 mm and 4 mm were examined in a water bath. Artifact behavior was judged independently by 2 radiologists as showing "no artifacts" for all tested stent types. Signal-to-noise ratios inside and outside of the stents were measured yielding a Pearson correlation coefficient of 0.98 (y = 1.22 + 0.92x). Nineteen stents (8 hand woven, 3 mechanically woven, 8 lasered) were deployed in coronary arteries of 19 domestic pigs and were examined by cMRA. Artifact behavior of the stents was analyzed by measuring the signal-to-noise ratio at the stent positions and compared with signal-to-noise ratio measurements outside of the stents, yielding a Pearson correlation coefficient of 0.90 (y = -0.75 + 1.06x). All 3 prototypes of coronary MR stents allowed complete visualization of the stent lumen and consequently determination of stent patency by cMRA.
    Investigative Radiology 06/2004; 39(5):250-3. · 5.46 Impact Factor
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    ABSTRACT: Recent developments of magnetic resonance imaging enabled free-breathing coronary MRA (cMRA) using steady-state-free-precession (SSFP) for endogenous contrast. The purpose of this study was a systematic comparison of SSFP cMRA with standard T2-prepared gradient-echo and spiral cMRA. Navigator-gated free-breathing T2-prepared SSFP-, T2-prepared gradient-echo- and T2-prepared spiral cMRA was performed in 18 healthy swine (45-68 kg body-weight). Image quality was investigated subjectively and signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and vessel sharpness were compared. SSFP cMRA allowed for high quality cMRA during free breathing with substantial improvements in SNR, CNR and vessel sharpness when compared with standard T2-prepared gradient-echo imaging. Spiral imaging demonstrated the highest SNR while image quality score and vessel definition was best for SSFP imaging. Navigator-gated free-breathing T2-prepared SSFP cMRA is a promising new imaging approach for high signal and high contrast imaging of the coronary arteries with improved vessel border definition.
    Investigative Radiology 06/2003; 38(5):263-8. · 5.46 Impact Factor
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    Trung Hieu Nguyen
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    ABSTRACT: Derzeit befindet sich die Magnetresonanz-Koronarangiographie (MRKA) noch in der Entwicklungsphase. Um neue Erkenntnisse über das technische Potenzial dieser nicht invasiven diagnostischen Methode zu erlangen, wurde in dieser Arbeit ein Vergleich zwischen vier MRKA-Sequenzen vorgenommen. Als Vergleich diente jene Sequenz (Standard T2 präparierte 3D Gradienten Echo Sequenz), welche bisher als einzige in einer validierten Studie auf die Nutzung als MRKA-Sequenz untersucht worden ist. Ihr wurden drei verschiedene Sequenzen gegenübergestellt, welche in anderen Studien eine erfolgreiche technische Implementation erzielt hatten. Es zeigte sich, dass keine der vier Sequenzen bei den üblichen Vergleichskriterien als insgesamt überragende Sequenz hervorging. Die Ergebnisse erlaubten jedoch die Schlussfolgerung, dass zwei Sequenzen (T2 präpariert 3D steady-state free precession Sequenz mit kartesischer und radialer k-Raumabtastung) gegenüber der Vergleichssequenz bei differenzierter Interpretation der Vergleichskriterien überlegen waren. Insbesondere die radiale k-Raumabtastung könnte das derzeit größte Problem in der MRKA, die Bewegungsartefaktunterdrückung, sehr günstig beeinflussen. Daher sind zukünftige Studien mit der SSFP-Technik zur Verbesserung dieser viel versprechenden Sequenzen zu erwarten. At the moment coronary magnetic resonance angiography (corMRA) is still in research. To get more information about the potential of this non invasive method of diagnosis we compared four corMRA sequences. The sequence we used for reference sequence is the only one which has been investigated in a validated study so far. The three sequences we used for comparison have already been successfully technically implemented in former studies. With respect to the usual comparison criteria this study showed that none of the four sequences turned out as a generally outstanding sequence. However, differentiated interpretation of the comparison criteria allowed the conclusion that the reference sequence (Standard T2 Prepared 3D Gradient-Echo Sequence) could not reach the performance of two other sequences (two T2 Prepared 3D SSFP Sequences, one with cartesian and the other one with radial k-space sampling). In particular, radial k-space sampling could solve the currently largest problem in corMRA, the suppression of motion artifacts. Therefore we can surely expect new studies with improvement of these promising sequences.