91ÇàÇà²Ý

Title of the doctoral thesis: Unconventional MRI scanner technology and intelligent dynamics

Doctoral student: Koos (Cornelis) Zevenhoven
Opponent: Prof. Lawrence Wald, Harvard Medical School, USA 
Custos: Prof. Lauri Parkkonen, Aalto University School of Science, Department of Neuroscience and Biomedical Engineering

Thesis available for public display 10 days prior to the defence at: 

New MRI scanner broadens application prospects and provides accurate information about the brain 

Magnetic resonance imaging (MRI) enables the non-invasive examination of the internal structure of the body in various clinical and scientific applications. The development of conventional MRI technology, however, has focused on increasing the magnetic field strength, which besides small improvements leads to more expensive, heavier, louder and more cramped devices. In addition, strong magnetic fields prevent the use of many other technologies in conjunction with MRI and can cause safety hazards. 

In this thesis, a new MRI scanner has been developed, in which the implementations of all parts differ from those of conventional MRI. Superconductivity – the quantum phenomenon where paired electrons form a matter wave that carries electric current without resistance – is applied both for extremely precise measurement of magnetic signals and for generating a so-called polarizing field. The approaches taken enable the use of significantly weaker magnetic fields. This work also covers theory, electronics, software and methods for use with the technology. 

Different variations made of the scanner demonstrate different benefits compared to conventional MRI. These include improved portability, lower cost, light weight, unobstructedness and greater spatial accuracy. A further result of this Thesis is a combination brain scanner that, in addition to MRI, can perform magnetoencephalography (MEG), which measures the location and dynamics of brain activity via magnetic fields. MEG and MRI are obtained accurately in the same coordinate system. 

Intelligent dynamics is one of the themes of this Thesis. Like brain activity, many components of the scanner involve complex and multi-dimensional dynamics. Dynamical pulse-waveform coupling (DynaCAN) is a class of techniques introduced in this thesis, in which suitably shaped pulses are used to produce a desired outcome. As some examples, unwanted eddy currents occurring in the device parts can be nulled accurately, or sensors can be restored into an operable state. According to preliminary brain-circuit simulations, the same principle is promising also in targeting brain stimulation. The approach may have a wider range of use cases. 

On commercialization, the imaging technologies developed in this Thesis will broaden the application area of MRI and open up new prospects for diagnosis and treatment planning.

Contact details:

Doctoral theses in the School of Science: