Magnetic resonance RF pulse design for simultaneous multislice imaging

Magnetic Resonance Imaging (MRI) is one of the leading non-invasive medical imaging techniques to image healthy and pathological anatomy and physiological processes of the body and is primarily known for its excellent soft tissue contrast.
Contrary to other high resolution imaging techniques, MRI is based on strong magnetic and electric fields and does not require ionizing radiation.
Image acquisition, however, is often limited by long acquisition times resulting from the need to repeat the measurement several times to encode multiple k-space data points.
In addition to lengthy acquisition times, limited MR hardware performance as well as physical and physiological effects further restrict the MR sequence parameters, which results in lower signal to noise ratio and increased sensitivity to motion or magnetic susceptibility effects.
This thesis is dedicated to the development and practical implementation of tailored large tip-angle radio frequency (RF) pulses and slice selective gradient shapes with increased excitation accuracy, lower power requirement and reduced pulse duration.
The presented optimal control based RF pulse design methods are formulated for the joint design of RF and slice selective gradient shape for different large tip-angle applications.
The focus of this work is on simultaneous multislice (SMS) applications to push acceleration of existing 2D MRI acquisition strategies.
The extension to constrained RF pulse optimization allows exploitation of various MR hardware limits and yields accurate low power RF pulses and slice selective gradient shapes with short pulse durations.
The optimized waveforms proved to outperform existing RF pulses and can be used to reduce the minimal echo spacing and echo time.
Numerous simulation and experimental examples based on phantom and in-vivo measurements demonstrate the increased excitation accuracy and the reduction of both RF power and RF duration.