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04 March 2014

Risto Ilmoniemi – Picture this: a better image of our brain

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Scientists have been devising new ways of looking inside the human mind, via brain imaging. 

Brain researchers have recently associated a technique called magnetoencephalography, or MEG, with magnetic resonance imaging, or MRI, technology. This is a bit like combining in-depth photography of the brain using MRI with a high-resolution video recorder using MEG. MRI shows structure, whereas MEG shows activity as it records the electrical activity of brain cells as they signal to one another. 

A combined instrument would help scientists studying how the brain works, facilitate our understanding of conditions like schizophrenia and help some patients such as those who suffer from epilepsy. Here, Risto Ilmoniemi professor of biomedical engineering at Aalto University in Finland and a leading expert on MEG speaks to about the new ways of looking inside the human brain, building on the findings of an EU-funded project, called MEG-MRI, completed in 2012.

What is MEG?
It is the recording the magnetic fields produced by the human brain. By measuring such magnetic fields we can locate [brain cells’] activity. For instance, when people listen to words or look at images, we can see where the brain activity is and how it evolves over time. We can also see the background activity of the brain.

Why is it interesting to combine MEG with MRI?
During the project, our aim was to be able to use the same magnetic sensors that we use in MEG also for MRI. We need MRI to interpret the MEG results anyway, because MRI gives the structure, shape and important details of the tissue in the brain. MEG gives just the activity, so we need both. There are many benefits from combining the two and relying on just one instrument. Now that we have a new technology for combining both, this will save time and money. Another advantage is that we will be able to get the localisation of activity with much greater accuracy.

What are MEG’s main advantages over other brain activity imaging technologies such as functional MRI?
The main advantage of MEG is that the time resolution is better. It is faster. We can measure fast events, whereas [functional] MRI—as opposed to merely structural MRI—is very slow. So we have to wait several seconds before we get a good signal. This way, we can find which part of the brain is active but we cannot really determine what the order of activity is. With MEG we can very accurately determine the order of activation. We can see sequences of activity happening in the brain, as it reacts to sounds or sights for example. But the two imaging techniques complement one another. 

Why is it a challenge to combine MRI and MEG?
The magnetic fields produced by the brain are very weak. Therefore the MEG sensors have to be very sensitive to measure these signals. That is one the difficulties, because in MRI the magnetic fields used are usually very strong. Sometimes, I compare the strong magnetic pulse from MRI to a hurricane wind, so really very strong. And then a fraction of a second later we turn it off and measure small vibrations [in MEG].

Which patients will most likely benefit from MEG?
Epileptic patients, for example. Typically with epileptic seizures, there are spikes of activity that happen in time and we cannot detect these with MRI. These are very brief, like a fraction of a second. Another example of MEG applications is for people who have cancer of the brain and are waiting for surgery. With MEG, we can locate important parts such as motor or language areas that should be spared during surgery.

When is MEG combined with MRI likely to be widely available?
We still need to overcome technical challenges and improve the sensors. This should be feasible but it will take another four to five years. If we make the first medical prototype in five years, it will take some time before it is commercialised once permissions are granted and after it has been recognised as medically acceptable. provides its content to all media free of charge. We would appreciate if you could acknowledge as the source of the content.