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State Free Precession (state + free_precession)

Distribution by Scientific Domains
Medical Sciences100%

Kinds of State Free Precession

  • steady state free precession
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    Selected Abstracts

    Three-dimensional balanced steady state free precession imaging of the prostate: Flip angle dependency of the signal based on a two component T2-decay model

    JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 5 2010
    Tryggve H. Storås MS
    Abstract Purpose: To investigate the contrast of three-dimensional balanced steady state free precession (3D bSSFP) in the two component T2 model and to apply the results to optimize 3D bSSFP for prostate imaging at 1.5 Tesla. Materials and Methods: In each of seven healthy volunteers, six 3D bSSFP acquisitions were performed with flip angles (,) equally spaced between 10° and 110°. Predictions of signal and contrast were obtained from synthetic bSSFP images calculated from relaxation parameters obtained from a multi-spin-echo acquisition. One biexponential and two monoexponential models were applied. Measured and predicted signals were compared by simple linear regression. Results: The measured contrast to signal ratio increased continuously with ,. Mean R2 for the biexponential model was almost constant for , in the range 50,110°. The biexponential model was a better predictor of the measured signal than the monoexponential model. A monoexponential model restricted to the echoes TE = 50,125 ms performed similar to the biexponential model. The predicted contrast peaked at , between 50° and 90°. Conclusion: Prostate imaging with bSSFP benefited from high flip angles. The biexponential model provided good signal prediction while predictions from the monoexponential models are dependent on the range of TE used for T2 determination. J. Magn. Reson. Imaging 2010;31:1124,1131. © 2010 Wiley-Liss, Inc. [source]

    Artifact-reduced two-dimensional cine steady state free precession for myocardial blood- oxygen-level-dependent imaging

    JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2010
    Xiangzhi Zhou PhD
    Abstract Purpose: To minimize image artifacts in long TR cardiac phase-resolved steady state free precession (SSFP) based blood-oxygen-level-dependent (BOLD) imaging. Materials and Methods: Nine healthy dogs (four male, five female, 20,25 kg) were studied in a clinical 1.5 Tesla MRI scanner to investigate the effect of temporal resolution, readout bandwidth, and motion compensation on long repetition time (TR) SSFP images. Breath-held 2D SSFP cine sequences with various temporal resolutions (10,204 ms), bandwidths (239,930 Hz/pixel), with and without first-order motion compensation were prescribed in the basal, mid-ventricular, and apical along the short axis. Preliminary myocardial BOLD studies in dogs with controllable coronary stenosis were performed to assess the benefits of artifact-reduction strategies. Results: Shortening the readout time by means of increasing readout bandwidth had no observable reduction in image artifacts. However, increasing the temporal resolution in the presence of first-order motion compensation led to significant reduction in image artifacts. Preliminary studies demonstrated that BOLD signal changes can be reliably detected throughout the cardiac cycle. Conclusion: Artifact-reduction methods used in this study provide significant improvement in image quality compared with conventional long TR SSFP BOLD MRI. It is envisioned that the methods proposed here may enable reliable detection of myocardial oxygenation changes throughout the cardiac cycle with long TR SSFP-based myocardial BOLD MRI. J. Magn. Reson. Imaging 2010;31:863,871. ©2010 Wiley-Liss, Inc. [source]

    In vivo ultra-high-field magnetic resonance imaging of trabecular bone microarchitecture at 7 T

    JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2008
    Roland Krug PhD
    Abstract Purpose To investigate the feasibility of 7T magnetic resonance imaging (MRI) to visualize and quantify trabecular bone structure in vivo by comparison with 3T MRI and in vivo three-dimensional (3D) high-resolution peripheral quantitative computed tomography (HR-pQCT). Materials and Methods The distal tibiae of 10 healthy volunteers were imaged. Therefore, fully balanced steady state free precession (bSSFP) and spin-echo (bSSSE) pulse sequences were implemented and optimized for 7T. Structural bone parameters, such as apparent bone-volume over total-volume fraction (app.BV/TV), apparent trabecular plate separation (app.TbSp), apparent trabecular plate thickness (app.TbTh), and apparent trabecular plate number (app.TbN), were derived. Results All structural trabecular bone parameters correlated well (r > 0.6) between 7T and 3T, and between 7T and HR-pQCT (r > 0.69), with the exception of app.TbTh, which correlated modestly (r = 0.41) between field strengths and very low with HR-pQCT (r < 0.16). Regarding absolute values, app.TbN varied only 4% between field strengths, and only 0.6% between 7T and HR-pQCT. App.TbSp correlated best between 7T and HR-pQCT (r = 0.89). Using bSSSE, significant smaller trabecular thickness and significant higher trabecular number were found compared to bSSFP. Conclusion We concluded that imaging and quantification of the trabecular bone architecture at 7T is feasible and preferably done using bSSSE. There exists great potential for ultra-high-field (UHF) MRI applied to trabecular bone measurements. J. Magn. Reson. Imaging 2008;27:854,859. © 2008 Wiley-Liss, Inc. [source]

    View ordering for magnetization prepared steady state free precession acquisition: Application in contrast-enhanced MR angiography

    MAGNETIC RESONANCE IN MEDICINE, Issue 3 2004
    Pascal Spincemaille
    Abstract Magnetization prepared segmented acquisition requires a view order that maximizes signal contrast during the acquisition of the central portion of k -space. Steady state free precession (SSFP) acquisition further requires a view order that minimizes changes in phase-encoding gradients from one repetition to the next in order to minimize eddy current artifacts. In this article, optimal view ordering schemes satisfying these two requirements are formulated and applied to inversion prepared 3D SSFP contrast-enhanced MR angiography (MRA). Experiments on phantoms and pigs demonstrated improved background suppression and reduced image artifacts. Magn Reson Med 52:461,466, 2004. © 2004 Wiley-Liss, Inc. [source]