Steady-state free precession imaging

About: Steady-state free precession imaging is a research topic. Over the lifetime, 1118 publications have been published within this topic receiving 34223 citations. The topic is also known as: SSFP imaging.

Magnetic Resonance Imaging: Physical Principles and Sequence Design

Abstract: Magnetic Resonance Imaging: A Preview. Classical of a Single Nucleus to a Magnetic Field. Rotating Reference Frames and Resonance. Magnetization, Relaxation and the Bloch Equation. The Quantum Mechanical Basis of Precession and Excitation. The Quantum Mechanical Basis of Thermal Equilibrium and Longitudinal Relaxation. Signal Detection Concepts. Introductory Signal Acquisition Methods: Free Induction Decay, Spin Echoes, Inversion Recovery and Spectroscopy. One-Dimensional Fourier Imaging, k-Space and Gradient Echoes. Multi-Dimensional Fourier Imaging and Slice Excitation. The Continuous and Discrete Fourier Transforms. Sampling and Aliasing in Image Reconstruction. Filtering and Resolution in Fourier Transform Image Reconstruction. Projection Reconstruction of Images. Signal, Contrast and Noise. A Closer Look at Radiofrequency Pulses. Water/Fat Separation Techniques. Fast Imaging in the Steady State. Segmented k-Space and Echo Planar Imaging. Magnetic Field Inhomogeneity Effects and T-2 Dephasing. Random Walks, Relaxation and Diffusion. Spin Density, T-1 and T-2 Quantification Methods in MR Imaging. Motion Artifacts and Flow Compensation. MR Angiography and Flow Quantification. Magnetic Properties of Tissues: Theory and Measurement. Sequence Design, Artifacts and Nomenclature. Introduction to MRI Coils and Magnets. Appendices. Index.

Rapid combined T1 and T2 mapping using gradient recalled acquisition in the steady state.

Abstract: A novel, fully 3D, high-resolution T(1) and T(2) relaxation time mapping method is presented. The method is based on steady-state imaging with T(1) and T(2) information derived from either spoiling or fully refocusing the transverse magnetization following each excitation pulse. T(1) is extracted from a pair of spoiled gradient recalled echo (SPGR) images acquired at optimized flip angles. This T(1) information is combined with two refocused steady-state free precession (SSFP) images to determine T(2). T(1) and T(2) accuracy was evaluated against inversion recovery (IR) and spin-echo (SE) results, respectively. Error within the T(1) and T(2) maps, determined from both phantom and in vivo measurements, is approximately 7% for T(1) between 300 and 2000 ms and 7% for T(2) between 30 and 150 ms. The efficiency of the method, defined as the signal-to-noise ratio (SNR) of the final map per voxel volume per square root scan time, was evaluated against alternative mapping methods. With an efficiency of three times that of multipoint IR and three times that of multiecho SE, our combined approach represents the most efficient of those examined. Acquisition time for a whole brain T(1) map (25 x 25 x 10 cm) is less than 8 min with 1 mm(3) isotropic voxels. An additional 7 min is required for an identically sized T(2) map and postprocessing time is less than 1 min on a 1 GHz PIII PC. The method therefore permits real-time clinical acquisition and display of whole brain T(1) and T(2) maps for the first time.

Normal human left and right ventricular dimensions for MRI as assessed by turbo gradient echo and steady-state free precession imaging sequences.

Abstract: Purpose To establish normal ranges of left ventricular (LV) and right ventricular (RV) dimensions as determined by the current pulse sequences in cardiac magnetic resonance imaging (MRI). Materials and Methods Sixty normal subjects (30 male and 30 female; age range, 20–65) were examined; both turbo gradient echo (TGE) and steady-state free precession (SSFP) pulse sequences were used to obtain contiguous short-axis cine data sets from the ventricular apex to the base of the heart. The LV and RV volumes and LV mass were calculated by modified Simpson's rule. Results Normal ranges were established and indexed to both body surface area (BSA) and height. There were statistically significant differences in the measurements between the genders and between TGE and SSFP pulse sequences. For TGE the LV end-diastolic volume (EDV)/BSA (mL/m2) in males was 74.4 ± 14.6 and in females was 70.9 ± 11.7, while in SSFP in males it was 82.3 ± 14.7 and in females it was 77.7 ± 10.8. For the TGE the LV mass/BSA (g/m2) in males was 77.8 ± 9.1 and in females it was 61.5 ± 7.5, while in SSFP in males it was 64.7 ± 9.3 and in females it was 52.0 ± 7.4. For TGE the RV EDV/BSA (mL/m2) in males was 78.4 ± 14.0 and in females it was 67.5 ± 12.7, while in SSFP in males it was 86.2 ± 14.1 and in females it was 75.2 ± 13.8. Conclusion We have provided normal ranges that are gender specific as well as data that can be used for age-specific normal ranges for both SSFP and TGE pulse sequences. J. Magn. Reson. Imaging 2003;17:323–329. © 2003 Wiley-Liss, Inc.

Principles and applications of balanced SSFP techniques

Abstract: During the past 5 years balanced steady-state free precession (SSFP) has become increasingly important for diagnostic and functional imaging. Balanced SSFP is characterized by two unique features: it offers a very high signal-to noise ratio and a T2/T1-weighted image contrast. This article focuses on the physical principles, on the signal formation, and on the resulting properties of balanced SSFP. Mechanisms for contrast modification, recent clinical application, and potential extensions of this technique are discussed.

T2 quantification for improved detection of myocardial edema

Abstract: Background: T2-Weighted (T2W) magnetic resonance imaging (MRI) pulse sequences have been used to detect edema in patients with acute myocardial infarction and differentiate acute from chronic infarction. T2W sequences have suffered from several problems including (i) signal intensity variability caused by phased array coils, (ii) high signal from slow moving ventricular chamber blood that can mimic and mask elevated T2 in sub-endocardial myocardium, (iii) motion artifacts, and (iv) the subjective nature of T2W image interpretation. In this work we demonstrate the advantages of a quantitative T2 mapping technique to accurately and reliably detect regions of edematous myocardial tissue without the limitations of qualitative T2W imaging. Methods: Methods of T2 mapping were evaluated on phantoms; the best of these protocols was then optimized for in vivo imaging. The optimized protocol was used to study the spatial, viewdependent, and inter-subject variability and motion sensitivity in healthy subjects. Using the insights gained from this, the utility of T2 mapping was demonstrated in a porcine model of acute myocardial infarction (AMI) and in three patients with AMI. Results: T2-prepared SSFP demonstrated greater accuracy in estimating the T2 of phantoms than multi-echo turbo spin echo. The T2 of human myocardium was found to be 52.18 ± 3.4 ms (range: 48.96 ms to 55.67 ms), with variability between subjects unrelated to heart rate. Unlike T2W images, T2 maps did not show any signal variation due to the variable sensitivity of phased array coils and were insensitive to cardiac motion. In the three pigs and three patients with AMI, the T2 of the infarcted region was significantly higher than that of remote myocardium. Conclusion: Quantitative T2 mapping addresses the well-known problems associated with T2W imaging of the heart and offers the potential for increased accuracy in the detection of myocardial edema.