Direct Processing of the MCG and MEG Signals Rostyslav SKLYAR Verchratskogo st. 15-1, Lviv 79010 UKRAINE Magnetocardiography (MCG) is a noninvasive method of detecting the cardiac magnetic fields above the body surface using DC superconducting quantum interference devices (SQUIDs) (Fig. 1). MCG has the potential to detect arrhythmia and ischemia with a lower level of adverse effects than electrocardiograms. Also most SQUIDs are incorporated into wholehead systems for magnetoencephalography (MEG)- the detection of magnetic fields (MFs) produced by brain. A typical helmet contains about 300 sensors, including a number of reference sensors for noise cancellation, cooled to 4.2 K. Implantable neural probes are generally preferred to have a minimum footprint as possible to minimize neural damage and to facilitate easy entry and movement through the brain tissue [1]. Implantable neural probes for neuroscience and brain machine interfaces are generally preferred to have a minimum footprint as possible to minimize neural damage (Fig. 2). Alternatively, a SuFET based neurotransducer with carbon nanotubes (CNT) or pickup coil (PC) kind of input circuit for the nerve and neuron impulse has been designed [2]. A further step should be synthesis of the said two methods in order to develop the external (nonimplantable) MCG&MEG signals-to-processor connection. The EM sensors are surface PCs, which are used in regular configuration where PCs with a small distance between each other are positioned within the helmet type surface to pick up the local signals within the place of interest. The problem of sensing the EM signal for amplification/switching it with a speed of light in a single (passive) solid-state device (EMT) has been advanced [2]. The said problem in the advanced method is solving by application of ferroelectric or ferroelectromagnetic (FE or FEM) crystals which are controlled by an electric or magnetic fields (EF or MF) respectively (Fig. 3). The term ‘MEG sensor array’ will mean the collection of EMTs (Fig. 4). Rejection of environmental noise can be improved by measuring a MF difference, rather than the field itself. Such flux transformers are referred to as gradiometers (i.e. the field difference approximates a component of the field gradient tensor) [3]. The radial gradiometer detects the radial gradient of a radial MF (radial with respect to the surface of the head) (Fig5). The 20 cm 2 array for sheathing of the heart or brain consists of 40 thous. EMTs which could be produced by printed electronics processes. These elements are set out into the square or rectangular matrices A ij and are included in further mathematical operations (Fig. 6). Control (and interaction) signals can be both in the current and voltage form to create MF or EF respectively. Signal contribution corresponding to a dipole of a specified rms amplitude and at a specified position within the model sphere, figure 5, was added to the noise covariance matrix and the resulting covariance matrix was used to compute SAM depth profiles. 1. HajjHassan M., Chodavarapu V., and Musallam S., NeuroMEMS: Neural Probe Microtechnologies (Review), Sensors, vol. 8, 2008, pp. 6704-6726; 2. Sklyar R., CNT and Organic FETs Based Two-Way Transducing of the Neurosignals, in: Nanotechnology 2008: Life Sciences, Medicine, and Bio Materials, Nano Science & Technology Institute, Cambridge, MA, USA, CRC Press, vol. II, Nano Medicine & Neurology, 810 pages (4 pages); 3. Vrba J. and Robinson S. E., SQUID sensor array configurations for magnetoencephalography applications (Topical Review), Supercond. Sci. Technol., vol. 15, 2002, pp. R51–R89.
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