In collaboration with scientists from the Ioffe Institute, HSE University researchers have developed an ultra-sensitive atomic magnetometric scheme with a sensitivity of 5 fTl×Hz-1/2, setting a performance record for sensors operating in the Earth's magnetic field. The scheme will be used to design a multichannel atomic magnetoencephalograph, expected to be the most accurate and compact device available today for non-invasive measurement of the brain's electrical activity. The cost of the new atomic magnetoencephalograph is estimated to be five to seven times lower than that of existing devices, making it an affordable tool for diagnosing epilepsy and other neurodegenerative diseases in a broad population of patients.
Several technologies are available today which allow physicians and researchers to detect and study brain activity non-invasively, without the need for surgery. Magnetoencephalography (MEG) measures the brain's electrical activity by recording magnetic fields generated by neural ensembles and is considered the most promising technique currently being developed. Central to this cutting edge technology are highly sensitive SQUID sensors (superconducting quantum interference devices) which operate in a state of superconductivity and require cooling to helium temperatures by being placed in a Dewar vessel with liquid helium. The downsides of such an approach to MEG include the bulkiness of the required equipment, expensive operating and maintenance and additional depreciation costs, but most importantly, the fact that such sensors must be contained in a Dewar flask with 3 – 3.5 cm walls and therefore cannot be brought close enough to a patient's scalp. Nevertheless, this is the most accurate and sensitive method of non-invasive functional brain mapping available today: under certain circumstances, it can differentiate millisecond scale bursts of activity in neural ensembles located a few millimetres apart.
No more than 400 such systems are currently available worldwide, which significantly limits access to this technology essential for the detailed diagnosis of neurological diseases, for planning neurosurgical interventions, and for studying brain functioning and the direct and side effects of pharmachological interventions.
New developments and achievements in atomic magnetometry physics mean that the use of SQUIDs can be avoided while enabling higher mapping accuracy and lowering the cost of the device and making it more mobile. Scientists in countries such as the U.S., the U.K., Germany and Finland have been working to develop a compact and cheap MEG system. In the last 18 months, a team of HSE researchers, in collaboration with the Ioffe Institute in St. Petersburg, have been implementing a project to develop and design a multichannel magnetoencephalography system using optically pumped magnetometers (OPM).
'Unlike the sensors used by some of our competitors, our main focus in developing an atomic MEG device is on sensors capable of operating in the Earth's magnetic field. As long as such sensors do not require a uniform magnetic field but can operate within its natural variations, there will be no need for additional magnetic field stabilization. We might even be able to skip the bulky magnetically shielded room and replace them with a compact shielding solution,' explains Alexey Ossadtchi, Director of the HSE Centre for Bioelectric Interfaces and the project leader from the HSE side.
To date, the researchers have been able to achieve a record sensitivity of 5 fTl×Hz-1/2 for a sensor operating in the Earth's magnetic field. This result allows smaller devices to be made; such compact optically pumped magnetometers (OPM) can then be combined in a multi-channel MEG system of a new generation with dramatically advanced capabilities.
According to the scientists, the device sensors will be located at a distance of five-millimetre or less from the scalp, which is 4-6 times closer than any other system available today, while their measurement accuracy will be an order of magnitude higher than that of the existing systems. The new technology will enable non-invasive visualization of brain activity with a degree of accuracy which currently requires a surgical intervention. More specifically, the system will be capable of separately detecting the activity of neural ensembles located a fraction of a millimetre apart.
The researchers estimate the cost of this MEG system to be 5-7 times lower than that of existing devices which currently hovers around $5 million.
This technological breakthrough has been made possible by collaboration of physicists, signal processing specialists, mathematicians and neurobiologists. Adapting advanced technology such as high-sensitivity quantum magnetometry to perform functional neuroimaging can result in a new generation of devices and open up wider opportunities for the diagnosis and rehabilitation of patients with epilepsy and a wide range of neurodegenerative diseases. The developers estimate the Russian market of optically pumped magnetometry (OPM) systems, including B2B services, at 100 billion rubles (lost profits not included).
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