Abstract

Introduction: An important side effect of applying a frequency selective pulse is the introduction of a phase gradient across the spectrum. Flip angle deviations on the order of 5-10% significantly change the phase profile across the passband of the pulse. Methods: The frequency response of a spin-echo is calculated from the Cayley-Klein parameters for the two pulses in a 90-180 spin-echo pair. To design the pulses we first establish a goal profile which defines the ideal profile for a pair of amplitude-modulated pulses subject to B1 inhomogeneity. Least squares optimization by simulated annealing is then used to find the pulse pair that minimizes the deviation between the actual profile and the goal profile, for +/-20% variation in B1. Results: The pulses were implemented as spatial-spectral pulses for use in a fast spectroscopic imaging experiment. Measurements of phase variations over the volume of interest confirmed the stability of the phase profile. Conclusions: A joint design of 90-180 spin-echo pairs offers frequency profiles that are immune to up to 20% variation in RF homogeneity.

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
National Center for Research Resources (NCRR)
Type
Biotechnology Resource Grants (P41)
Project #
5P41RR009784-04
Application #
6282949
Study Section
Project Start
1998-01-01
Project End
1998-12-31
Budget Start
1997-10-01
Budget End
1998-09-30
Support Year
4
Fiscal Year
1998
Total Cost
Indirect Cost

  Institution

Name
Stanford University
Department
Type
DUNS #
800771545
City
Stanford
State
CA
Country
United States
Zip Code
94305

  Publications

Maclaren, Julian; Aksoy, Murat; Ooi, Melvyn B et al. (2018) Prospective motion correction using coil-mounted cameras: Cross-calibration considerations. Magn Reson Med 79:1911-1921
Guo, Jia; Holdsworth, Samantha J; Fan, Audrey P et al. (2018) Comparing accuracy and reproducibility of sequential and Hadamard-encoded multidelay pseudocontinuous arterial spin labeling for measuring cerebral blood flow and arterial transit time in healthy subjects: A simulation and in vivo study. J Magn Reson Imaging 47:1119-1132
Tamir, Jonathan I; Uecker, Martin; Chen, Weitian et al. (2017) T2 shuffling: Sharp, multicontrast, volumetric fast spin-echo imaging. Magn Reson Med 77:180-195
Lai, Lillian M; Cheng, Joseph Y; Alley, Marcus T et al. (2017) Feasibility of ferumoxytol-enhanced neonatal and young infant cardiac MRI without general anesthesia. J Magn Reson Imaging 45:1407-1418
Taviani, Valentina; Alley, Marcus T; Banerjee, Suchandrima et al. (2017) High-resolution diffusion-weighted imaging of the breast with multiband 2D radiofrequency pulses and a generalized parallel imaging reconstruction. Magn Reson Med 77:209-220
Uecker, Martin; Lustig, Michael (2017) Estimating absolute-phase maps using ESPIRiT and virtual conjugate coils. Magn Reson Med 77:1201-1207
Kogan, Feliks; Hargreaves, Brian A; Gold, Garry E (2017) Volumetric multislice gagCEST imaging of articular cartilage: Optimization and comparison with T1rho. Magn Reson Med 77:1134-1141
Aksoy, Murat; Maclaren, Julian; Bammer, Roland (2017) Prospective motion correction for 3D pseudo-continuous arterial spin labeling using an external optical tracking system. Magn Reson Imaging 39:44-52
Bian, W; Tranvinh, E; Tourdias, T et al. (2016) In Vivo 7T MR Quantitative Susceptibility Mapping Reveals Opposite Susceptibility Contrast between Cortical and White Matter Lesions in Multiple Sclerosis. AJNR Am J Neuroradiol 37:1808-1815
Vos, Sjoerd B; Aksoy, Murat; Han, Zhaoying et al. (2016) Trade-off between angular and spatial resolutions in in vivo fiber tractography. Neuroimage 129:117-132

Showing the most recent 10 out of 446 publications