The Cerca OPM-MEG System uses a unique helmet design to place 64 sensors as close as possible to the scalp surface, and an advanced array design which ensures effective cancellation of magnetic fields of no interest arising from interference sources. Given OPMs and shielding, OPM-MEG requires a solution to the non-trivial problem of integrating an array of OPMs into a wearable helmet ensuring that the array is optimised to characterise the magnetic fields generated by the brain, and allowing it to “talk” to the shielding to provide the best MEG data possible. This shielding facilitates the perfect environment for an OPM-MEG system. All of this combined has led to an exceptional magnetic environment with fields below 1 nT a shielding factor of over 50,000. Recent developments have enabled the construction of new types of MSR, with built-in degaussing to remove residual magnetisation and reduce the static magnetic field parallel work has enabled the design and construction of electromagnetic coils which allow high fidelity control of residual fields and their variation over space inside the MSR. If OPMs are to be used and participants allowed to move freely, this field must be removed. ![]() magnetic fields that vary over time), however in conventionally designed rooms, the presence of the metal means that there is a residual static magnetic field. This acts to reduce magnetic interference (i.e. ![]() Conventional MEG systems are housed inside a magnetically-shielded room (MSR) which comprises multiple layers of high permeability material known as MuMetal ®, as well as a single layer of highly conductive material such as copper. Because the magnetic fields measured by MEG are so small, the scanner needs to be sited in a well-controlled, low magnetic field environment.
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