Design of Multidimensional Large -Tip -Angle Radiofrequency Pulses for Parallel Transmission in Magnetic Resonance Imaging
Xu, Dan
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/81072
Description
Title
Design of Multidimensional Large -Tip -Angle Radiofrequency Pulses for Parallel Transmission in Magnetic Resonance Imaging
Author(s)
Xu, Dan
Issue Date
2007
Doctoral Committee Chair(s)
Liang, Zhi-Pei
Department of Study
Electrical and Computer Engineering
Discipline
Electrical and Computer Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Biomedical
Language
eng
Abstract
To address the second issue, the difficulty of directly applying the variable-rate selective excitation principle to multidimensional RF pulses (including both single-channel and parallel transmission) is first identified. Then, an alternative approach using a new class of spiral trajectories, termed the variable slew-rate spirals, is proposed to locally reduce B 1 amplitude of 2D RF pulses. The peak B1 reduction is achieved by changing the gradient slew-rate profile, and hardware constraints such as gradient amplitude and slew-rate constraints are inherently satisfied by the design of variable slew-rate spiral gradient waveforms. The governing differential equations for a variable slew-rate spiral are derived, and both numeric and analytic solutions to the equations are given. The variable slew-rate spiral design is applicable to peak B 1 amplitude reduction of both single-channel and parallel transmission RF pulses. The localized manipulation of gradient waveforms empowers variable slew-rate spirals to generate shorter RF pulses than conventional constant slew-rate spiral-based pulses under the same hardware constraints. These shorter RF pulses are in general less sensitive to resonance frequency offsets.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
