Design of Multidimensional Large -Tip -Angle Radiofrequency Pulses for Parallel Transmission in Magnetic Resonance Imaging

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Electrical and Computer Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Xu, Dan

Contributors dc:contributor

• Liang, Zhi-Pei

• Engineering, Biomedical

Language dc:language

eng

Identifier

(MiAaPQ)AAI3301253

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/81072