## Abstract Diffusionโweighted steadyโstate free precession (DWโSSFP) accumulates signal from multiple echoes over several TRs yielding a strong sensitivity to diffusion with short gradient durations and imaging times. Although the DWโSSFP signal is well characterized for isotropic, Gaussian diffus
Signal-to-noise ratio behavior of steady-state free precession
โ Scribed by Scott B. Reeder; Daniel A. Herzka; Elliot R. McVeigh
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 566 KB
- Volume
- 52
- Category
- Article
- ISSN
- 0740-3194
No coin nor oath required. For personal study only.
โฆ Synopsis
Steady-state free precession (SSFP) is a rapid gradient-echo imaging technique that has recently gained popularity and is used in a variety of applications, including cardiac and real-time imaging, because of its high signal and favorable contrast between blood and myocardium. The purpose of this work was to examine the signal-to-noise ratio (SNR) behavior of images acquired with SSFP, and the dependence of SNR on imaging parameters such as TR, bandwidth, and image resolution, and the use of multi-echo sequences. In this work it is shown that the SNR of SSFP sequences is dependent only on pulse sequence efficiency, voxel dimensions, and relaxation parameters (T1 and T2). Notably, SNR is insensitive to bandwidth unless increases in bandwidth significantly decrease efficiency. Finally, we examined the relationship between pulse sequence performance (TR and efficiency) and gradient performance (maximum gradient strength and slew rate) for several imaging scenarios, including multi-echo sequences, to determine the optimum matching of maximum gradient strength and slew rate for gradient hardware designs. For standard modern gradient hardware (40 mT/m and 150 mT/m/ms), we found that the maximum gradient strength is more than adequate for the imaging resolution that is commonly encountered with rapid scouting (3 mm x 4 mm x 10 mm voxel). It is well matched for typical CINE and real-time cardiac imaging applications (1.5 mm x 2 mm x 6 mm voxel), and is inadequate for optimal matching with slew rate for high-resolution applications such as musculoskeletal imaging (0.5 x 0.8 x 3 mm voxel). For the lower-resolution methods, efficiency could be improved with higher slew rates; this provokes interest in designing methods for limiting dB/dt peripherally while achieving high switching rates in the imaging field of view. The use of multi-echo SSFP acquisitions leads to substantial improvements in sequence performance (i.e., increased efficiency and shorter TR).
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## Abstract The transient phase of shortโTR steadyโstate free precession (SSFP) sequences exhibits an often striking complexity and is not only important for nonequilibrium applications (e.g., rapid __T__~1~โmeasurements), but can also cause severe artifacts in conventional imaging. In both cases,
## Abstract Missing pulse steady state free precession (MPโSSFP), an extension of steady state free precession (SSFP), was evaluated for its ability to measure slow fluid flows. In experiments using flow phantoms, the MPโSSFP signal was sensitive to fluid velocities in the millimeters per second ra
An NMR imaging technique sensitive to slow flow (approximately 1 mm/s) using a conventional imaging gradient strength (0.025 mT/cm) is described. Two projections with different spatial magnetic periodicity (determined by the SSFP pulse interval), and thus with different flow sensitivities, are subtr