共查询到20条相似文献，搜索用时 15 毫秒
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C. Stehning P. Brnert K. Nehrke H. Eggers M. Stuber 《Magnetic resonance in medicine》2005,54(2):476-480
Respiratory motion is a major source of artifacts in cardiac magnetic resonance imaging (MRI). Free-breathing techniques with pencil-beam navigators efficiently suppress respiratory motion and minimize the need for patient cooperation. However, the correlation between the measured navigator position and the actual position of the heart may be adversely affected by hysteretic effects, navigator position, and temporal delays between the navigators and the image acquisition. In addition, irregular breathing patterns during navigator-gated scanning may result in low scan efficiency and prolonged scan time. The purpose of this study was to develop and implement a self-navigated, free-breathing, whole-heart 3D coronary MRI technique that would overcome these shortcomings and improve the ease-of-use of coronary MRI. A signal synchronous with respiration was extracted directly from the echoes acquired for imaging, and the motion information was used for retrospective, rigid-body, through-plane motion correction. The images obtained from the self-navigated reconstruction were compared with the results from conventional, prospective, pencil-beam navigator tracking. Image quality was improved in phantom studies using self-navigation, while equivalent results were obtained with both techniques in preliminary in vivo studies. 相似文献
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Sergio Uribe Vivek Muthurangu Redha Boubertakh Tobias Schaeffter Reza Razavi Derek L G Hill Michael S Hansen 《Magnetic resonance in medicine》2007,57(3):606-613
Two-dimensional (2D) breath-hold cine MRI is used to assess cardiac anatomy and function. However, this technique requires cooperation from the patient, and in some cases the scan planning is complicated. Isotropic nonangulated three-dimensional (3D) cardiac MR can overcome some of these problems because it requires minimal planning and can be reformatted in any plane. However, current methods, even those that use undersampling techniques, involve breath-holding for periods that are too long for many patients. Free-breathing respiratory gating sequences represent a possible solution for realizing 3D cine imaging. A real-time respiratory self-gating technique for whole-heart cine MRI is presented. The technique enables assessment of cardiac anatomy and function with minimum planning or patient cooperation. Nonangulated isotropic 3D data were acquired from five healthy volunteers and then reformatted into 2D clinical views. The respiratory self-gating technique is shown to improve image quality in free-breathing scanning. In addition, ventricular volumetric data obtained using the 3D approach were comparable to those acquired with the conventional multislice 2D approach. 相似文献
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Ak?akaya M Basha TA Chan RH Rayatzadeh H Kissinger KV Goddu B Goepfert LA Manning WJ Nezafat R 《Magnetic resonance in medicine》2012,67(5):1434-1443
We sought to evaluate the efficacy of prospective random undersampling and low-dimensional-structure self-learning and thresholding reconstruction for highly accelerated contrast-enhanced whole-heart coronary MRI. A prospective random undersampling scheme was implemented using phase ordering to minimize artifacts due to gradient switching and was compared to a randomly undersampled acquisition with no profile ordering. This profile-ordering technique was then used to acquire contrast-enhanced whole-heart coronary MRI in 10 healthy subjects with 4-fold acceleration. Reconstructed images and the acquired zero-filled images were compared for depicted vessel length, vessel sharpness, and subjective image quality on a scale of 1 (poor) to 4 (excellent). In a pilot study, contrast-enhanced whole-heart coronary MRI was also acquired in four patients with suspected coronary artery disease with 3-fold acceleration. The undersampled images were reconstructed using low-dimensional-structure self-learning and thresholding, which showed significant improvement over the zero-filled images in both objective and subjective measures, with an overall score of 3.6 ± 0.5. Reconstructed images in patients were all diagnostic. Low-dimensional-structure self-learning and thresholding reconstruction allows contrast-enhanced whole-heart coronary MRI with acceleration as high as 4-fold using clinically available five-channel phased-array coil. 相似文献
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Volker Rasche Ludwig Binner Friedrich Cavagna Vinzenz Hombach Markus Kunze Jochen Spiess Matthias Stuber Nico Merkle 《Magnetic resonance in medicine》2007,57(6):1019-1026
The feasibility of three-dimensional (3D) whole-heart imaging of the coronary venous (CV) system was investigated. The hypothesis that coronary magnetic resonance venography (CMRV) can be improved by using an intravascular contrast agent (CA) was tested. A simplified model of the contrast in T(2)-prepared steady-state free precession (SSFP) imaging was applied to calculate optimal T(2)-preparation durations for the various deoxygenation levels expected in venous blood. Non-contrast-agent (nCA)- and CA-enhanced images were compared for the delineation of the coronary sinus (CS) and its main tributaries. A quantitative analysis of the resulting contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) in both approaches was performed. Precontrast visualization of the CV system was limited by the poor CNR between large portions of the venous blood and the surrounding tissue. Postcontrast, a significant increase in CNR between the venous blood and the myocardium (Myo) resulted in a clear delineation of the target vessels. The CNR improvement was 347% (P < 0.05) for the CS, 260% (P < 0.01) for the mid cardiac vein (MCV), and 430% (P < 0.05) for the great cardiac vein (GCV). The improvement in SNR was on average 155%, but was not statistically significant for the CS and the MCV. The signal of the Myo could be significantly reduced to about 25% (P < 0.001). 相似文献
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Christian T. Stoeck MSc Yuchi Han MD Dana C. Peters PhD Peng Hu PhD Susan B. Yeon MD Kraig V. Kissinger BS RT Beth Goddu RT Lois Goepfert RN MS Warren J. Manning MD Sebastian Kozerke PhD Reza Nezafat PhD 《Journal of magnetic resonance imaging : JMRI》2009,29(6):1293-1299
Purpose
To compare two coronary vein imaging techniques using whole‐heart balanced steady‐state free precession (SSFP) and a targeted double‐oblique spoiled gradient‐echo (GRE) sequences in combination with magnetization transfer (MT) preparation sequence for tissue contrast improvement.Materials and Methods
Nine healthy subjects were imaged with the proposed technique. The results are compared with optimized targeted MT prepared GRE acquisitions. Both quantitative and qualitative analyses were performed to evaluate each imaging method.Results
Whole‐heart images were successfully acquired with no visible image artifact in the vicinity of the coronary veins. The anatomical features and visual grading of both techniques were comparable. However, the targeted small slab acquisition of the left ventricular lateral wall was superior to whole‐heart acquisition for visualization of relevant information for cardiac resynchronization therapy (CRT) lead implantation.Conclusion
We demonstrated the feasibility of whole‐heart coronary vein MRI using a 3D MT‐SSFP imaging sequence. A targeted acquisition along the lateral left ventricular wall is preferred for visualization of branches commonly used in CRT lead implantation. J. Magn. Reson. Imaging 2009;29:1293–1299. © 2009 Wiley‐Liss, Inc. 相似文献13.
Lai P Larson AC Bi X Jerecic R Li D 《Journal of magnetic resonance imaging : JMRI》2008,28(3):612-620
PURPOSE: To investigate the accuracy of a dual-projection respiratory self-gating (DP-RSG) technique in dynamic heart position measurement and its feasibility for free-breathing whole-heart coronary MR angiography (MRA). MATERIALS AND METHODS: A DP-RSG method is proposed to enable accurate direct measurement of heart position by acquiring two whole-heart projections. On 14 volunteers we quantitatively evaluated the efficacy of DP-RSG by comparison with diaphragmatic navigator (NAV) and single-projection-based respiratory self-gating (SP-RSG) methods. For DP-RSG we also compared center-of-mass and two profile-matching algorithms in deriving heart motion. Coronary imaging was conducted on eight volunteers based on retrospective gating to preliminarily validate the effectiveness of DP-RSG for whole-heart coronary MRA. Comparison of vessel delineation was performed between images reconstructed using different gating methods. RESULTS: The quantitative evaluation shows that DP-RSG more accurately tracks heart motion than NAV with all gating window (GW) values and SP-RSG approaches with GW>or=2.5 mm and profile-matching algorithms are more reliable for motion derivation than center-of-mass calculations with GW>or=1.0 mm. Whole-heart coronary MRA studies demonstrate the feasibility of using DP-RSG to improve overall delineation of the coronary arteries. CONCLUSION: DP-RSG is a promising approach to better resolve respiratory motion for whole-heart coronary MRA compared to conventional NAV and SP-RSG. 相似文献
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Sergio Uribe Philipp Beerbaum Thomas Sangild Sørensen Allan Rasmusson Reza Razavi Tobias Schaeffter 《Magnetic resonance in medicine》2009,62(4):984-992
Four‐dimensional (4D) flow imaging has been used to study flow patterns and pathophysiology, usually focused on specific thoracic vessels and cardiac chambers. Whole‐heart 4D flow at high measurement accuracy covering the entire thoracic cardiovascular system would be desirable to simplify and improve hemodynamic assessment. This has been a challenge because compensation of respiratory motion is difficult to achieve, but it is paramount to limit artifacts and improve accuracy. In this work we propose a self‐gating technique for respiratory motion‐compensation integrated into a whole‐heart 4D flow acquisition that overcomes these challenges. Flow components are measured in all three directions for each pixel over the complete cardiac cycle, and 1D volume projections are obtained at certain time intervals for respiratory gating in real time during the acquisition. The technique was tested in 15 volunteers, in which stroke volumes (SVs) in the great arteries showed excellent agreement with standard 2D phase‐contrast (PC) scans. In contrast, nongated 4D flow with two averages had substantial disagreement with 2D flow. Applied to patients with congenital cardiac left‐to‐right shunting, the precision of flux data was highly beneficial. The methodology presented here has the potential to allow a complete study of flow pathophysiology of the thoracic cardiovascular system from a single free‐breathing scan. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc. 相似文献