Erlangen University Hospital starts up 1.8 million euro magnetoencephalogram
The State Government of Bavaria and Erlangen University Hospital have invested approximately 1.8 million euros in a magnetoencephalogram (MEG) – the only one in Bavaria. The equipment, which weighs six tonnes and can show the brain’s thought processes without any contact, was turned on for the first time at the Neurology Clinic on Saturday 2 July 2011. Amongst other things, the device, called an “Alpha-Vis”, can be used to determine seizure triggers in patients with epilepsy, plan neurosurgical operations more precisely and, a world first, merge diagnostics using MEG, magnetic resonance tomography (MRT) and electroencephalography (EEG), within the framework of an interdisciplinary project being conducted by the DFG (German Research Foundation).
The MEG’s measurement is passive, i.e. it does not generate any magnetic fields. Using a 100kg sensor located in a head piece the size of an oil drum and cooled with helium to the temperature of outer space, magnetic fields in the femto and pico Tesla ranges are studied in a 4 x 5 x 3 metre shielded room. “The magnetic fields measured are hundreds of millions of times weaker than the earth’s magnetic field. That means, for instance, that a high speed train trundling through the station two kilometres from here can be seen on the MEG”, said Prof. Dr. Hermann Stefan, the first chairman of the interdisciplinary working group for bio magnetism at Erlangen University Hospital. “This allows us to watch people as they think.”
There are only around 100 MEG devices in the world. The one in Erlangen is an American “Magnes 3600WH” with cutting edge fittings (full-head multichannel MEG). It has a long tradition: the world’s first clinical multichannel MEG was launched in Erlangen in 1990. The new equipment is the third installation in Erlangen. “In the field of epilepsy MEG diagnosis, Erlangen has more experience than any other centre”, said Prof. Dr. Hajo Hamer, the Head of the Epilepsy Centre. “Thanks to the new full-head MEG, we can reap the full benefits of Prof. Stefan’s team’s years of experience in clinical epilepsy diagnostics in the Epilepsy Centre.”
World first in merger of electrophysiological and functional imaging
The Alpha Vis is operated by the Neurosurgical Clinic (director: Prof. Dr. Michael Buchfelder) in association with the Neurological Clinic (director Prof. Dr. Dr. h. c. Stefan Schwab) and the Epilepsy Centre at the Erlangen University Hospital. It is also to be shared for basic research by the HNO Clinic (director: Prof. Dr. Heinrich Iro), the Psychiatric and Psychotherapy Clinic (director: Prof. Dr. Johannes Kornhuber) and the Neuro-diagnosis Department (head: Prof. Dr. Arnd Dörfler) at Erlangen University Hospital and Friedrich Alexander University Erlangen Nuremberg (FAU) in cooperation with the University of Münster. “In the framework of a German Research Foundation project, we want to bring together diagnostics using MEG, EEG and MRT. A world first”, said Prof. Stefan. Research groups have been established with universities in Belgium (Ghent), France (Marseilles), Croatia (Zagreb), China (Chengdu), Japan (Tokyo) and the USA (Utah). “Our research results will directly benefit our patients”, Prof. Stefan assured.
The new MEG provides two procedures to record the brain’s electrical activity. “For many years now, recording the brain’s electrical activity has been an effective routine diagnostics method”, according to Prof. Stefan. In the first process, electrodes on the scalp surface are used to register data that is displayed as curves. This is called an electroencephalogram (EEG). Magnetoencephalography (MEG), using the magnetoencephalogram (also abbreviated to MEG) is another, newer technique for mapping brain activity. This technology makes it possible to record the magnetic fields that appear as a natural part of brain activity. Both processes can be used separately or together in the MEG device.
Then, EEG or MEG data can be used for a “source analysis” to determine the parts of the brain that generate the measured activity. This allows the origin of epileptic activity and the location of “functional areas”, i.e. the parts of the brain responsible for specific functions (movement, feeling, etc.) to be ascertained. Both can then be used at the Erlangen Epilepsy Centre to plan surgical interventions or even during an operation for “neuro navigation”.
“The advantage of the MEG is that the magnetic fields from the tissues around the brain (bones, skin, etc.) and from the brain tissues themselves, are not distorted”, said Prof. Stefan. That can be the case, however, with EEG. That distortion is particularly relevant when a patient has holes in the skull (from earlier operations, an accident, etc.). Even where there are significant deviations from a “normal” anatomy, such as different sized halves of the brain or lesions (e.g. tumours, vessel deformities) in the brain itself, such distortions can cause imprecision in the source analysis or in conventional diagnostics.
Furthermore, EEG and MEG are not equally sensitive to brain activity in different regions. That is why some studies showed epileptic spikes: short discharges between seizures that are only visible in the MEG or others that can only be seen using the EEG or both methods combined. Thus, in order to obtain as much information as possible, EEG and MEG measurements are combined in a single examination.
The measurement process itself is purely passive and does not generate any magnetic fields. That means it records only what comes from the brain’s own activity (“evoked”) to analyse the corresponding stimuli. This makes the examination harmless and painless. However, the patient must sit or lie still during the measurement, because any movement will cause a corresponding inaccuracy.
Because of the very weak electrical fields, a number of technical precautions have to be taken in order to record brain activity. The most obvious is the magnetically shielded room: a small room where the MEG device is located. This room is fitted with walls made of special material that shields against magnetic fields (e.g. the earth’s magnetic field, electrical conductors creating interference fields, etc.), but it is neither soundproof nor airtight. The examination itself is composed of several measurements which, including pre and post processing, take around two hours.
With the MEG examination, contact with the electrode system is not required, and it therefore does not stress patients. Further information for patients is available by phone 09131/85-34455 or online: www.epilepsiezentrum.uk-erlangen.de.
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Tel.: +49 (0)9131/85-36102
uni | press service | news No. 185/2011 on 01.07.2011