Browsing by Author "Ikaheimonen, Patrik"

In order to streamline the diagnosis process and increase the accessibility of both magnetic resonance imaging (MRI) and magnetoencephalocraphy (MEG), the department of Neuroscience and Biomedical Engineering at Aalto University is developing a new hybrid MEG--MRI device capable of performing both of these imaging methods. Both methods are measured using an array of Superconducting QUantum Interference Device (SQUID) magnetometers, which are extremely sensitive detectors capable of detecting the small magnetic fields generated by the human brain. However, the changing magnetic fields utilized in the MRI implementation cause eddy currents in the magnetically shielded walls of the MEG--MRI room, causing artefacts in the measured signals. In order to nullify these currents, an additional magnetic field of a specifically designed pulse waveform is fed into the room in a new technique called Dynamical Coupling for Additional dimeNsions (DynaCAN). To help in the development of DynaCAN, a program designed to detect and flag SQUIDs which saturate due to various different reasons, such as the induced eddy current fields, has been created and is presented in this work. This program finds saturated and faulty signals using four different Fault Detection Filters (FDFs) and tests if they are physically consistent with the signals of their neighboring detectors using Consistency Analysis (CA). It was found that the FDFs are able to find unambiguously faulty signals repeatably, while CA was more unreliable and was very susceptible to bad data present in the data set it was analysing.