Development of radiofrequency pulses for fast and motion-robust brain MRI

This thesis is based on three projects and the three scientific articles that were the result of each project. Each project deals with various kinds of technical software development in the field of magnetic resonance imaging (MRI). The projects are in many ways very different, encompassing several acquisition and reconstruction strategies. However, there are at least two common denominators. The first is the projects shared the same goal of producing fast and motion robust methods. The second common denominator is that all the projects were carried out with a particular focus on the radiofrequency (RF) pulses used.

The first project combined the acceleration method simultaneous multi-slice (SMS) with the acquisition method called PROPELLER. This combination was utilized to acquire motion-corrected thin-sliced reformattable T2-weighted and T1-FLAIR image volumes, thereby producing a motion robust alternative to 3D sequences. The second project analyzed the effect of the excitation RF pulse on T1-weighted images acquired with 3D echo planar imaging (EPI). It turned out that an RF pulse that reduced magnetization transfer (MT) effects significantly increased the gray/white matter contrast. The 3D EPI sequence was then used to rapidly image tumor patients after gadolinium enhancement. The third project combined PROPELLER’s retrospective motion correction with the prospective motion correction of an intelligent marker (the WRAD). With this combination, sharp T1-FLAIR images were acquired during large continuous head movements.

List of scientific papers

I. Simultaneous Multi-Slice combined with PROPELLER. Ola Norbeck, Enrico Avventi, Mathias Engström, Henric Rydén, & Stefan Skare. 2018. Magnetic Resonance in Medicine. 80(2), 496–506.
https://doi.org/10.1002/mrm.27041

II. Optimizing 3D EPI for Rapid T1-weighted Imaging. Ola Norbeck, Tim Sprenger, Enrico Avventi, Henric Rydén, Annika Kits, Johan Berglund, & Stefan Skare. 2020. Magnetic Resonance in Medicine. 84, 1441–1455.
https://doi.org/10.1002/mrm.28222

III. T1-w FLAIR imaging during continuous head motion: combining PROPELLER with an intelligent marker. Ola Norbeck, Adam van Niekerk, Enrico Avventi, Henric Rydén, Johan Berglund, Tim Sprenger, & Stefan Skare. Magnetic Resonance in Medicine. [Accepted]
https://doi.org/10.1002/mrm.28477