For 4 days in the end of January, MedTech West hosted an elective course for eight medical students. Elin Eriksson Hagberg, Johan Wessberg and Roger Watkins, all from the Department of Neuroscience at Gothenburg University, were course leaders together with MedTech West´s Justin Schneiderman. The name of the course was “Catch the wave – visualization of brain activity”, and, as the title indicates, it focused on various techniques to catch and visualize neurophysiological signals from the cortex, with a focus on EEG and MEG. MedTech West is involved in several research projects in which these techniques are used, either separate or in combination.
Faster than MRI
MEG (magnetoencephalography) is more than a 100 times faster than fMRI when it comes to following rapid brain signals and activity. It has exceptional temporal resolution, typically less than 1 millisecond (in contrast to ~1 second for fMRI). The MEG sensors pick up the weak magnetic fields generated by the flow of neural currents in the brain. It´s non-invasive and safe (as opposed to PET that requires radioactive tracers into the body). Applications for MEG include, for example, pre-operative planning for brain surgery, localization of epileptic centers and diagnosis of dementia. Research projects based at MedTech West in collaboration with the Gillberg Neuropsychiatry Centre at the University of Gothenburg are examining autism. One of the projects aims at understanding what makes a brain “autistic”. This understanding can improve diagnosis: Being able to diagnose, for example, children with autism at an early age would be very helpful, since it´s critical to get the right help as early as possible.
On the third day, Christoph Pfeiffer, PhD student, demonstrated the MEG system that is under development at the Chalmers Department of Microtechnology and Nanoscience – MC2. The group of medical students went to visit the MEG lab at the MC2 Department at Chalmers. There, the physics professor Dag Winkler´s research group is developing a new high-Tc SQUID MEG device, and the medical students got the opportunity to be examined with the MEG system. While MEG research at MedTech West focuses on investigating the brain, this demonstration carried out by Justin Schneiderman and Christoph Pfeiffer, was measuring magnetic fields from the students´ heart beats, which is significantly stronger and therefore easier to measure.
In high-Tc systems the operating temperature of the sensors is higher than in state-of-the-art MEG systems that employ low-Tc technology. For example, the sensors in the NatMEG system at the Karolinska Institute require cooling down to -269 Celsius. Low-Tc MEG system sensors are cooled with liquid helium, which is a very expensive, non-renewable resource. The high-Tc MEG system being developed at Chalmers instead uses liquid nitrogen for cooling. Since liquid nitrogen doesn´t cool the sensors nearly as much as helium does- the nitrogen only cools down to -196 Celsius- the sensors can be put much closer to the head, which leads to significantly stronger signals and thereby better images. The reduction in distance goes from a few centimeters to approximately a millimeter. The moderate cooling systems also allow for much more flexibility in the design of the helmet: it can, for example, fit children´s heads better than today´s systems.
Since the magnetic signals from the heart or the brain are extremely weak as compared to, for example, the earth´s magnetic field, shielding is necessary and therefore a magnetic shielded room (MSR) has been constructed for the MEG equipment. The equipment is so sensitive that even when recorded inside the MSR, the recordings can catch large amounts of noise that has to be removed before analysis can start. Yet, the sensitivity is a great advantage, since MEG can pick up both very quick and very small differences in magnetic fields.
The high-Tc Focal MEG system that is under development at Chalmers will need quite some time before becoming a commercial system. The expectations are that this system can be used for research a lot sooner, hopefully within the year. While keeping their hopes high for a future MEG lab at the Sahlgrenska University Hospital, the MedTech West, Sahlgrenska Academy and Chalmers researchers will have to keep bringing their patients and healthy controls all the way to the lab at Karolinska Institutet in Stockholm for now. The NatMEG lab is presently the only research laboratory in Sweden for whole-head measurements of neuronal brain activity using MEG. It was inaugurated in October 2013 and is available for researchers from all across Sweden.
Text and photo: Helene Lindström, 2017-02-17