Patent RU-2252692-C2 (RU)
Title: Method and device for studying functional state of brain and method for measuring subelectrode resistance
Inventor: ZAKHAROV S M
IPC: A61B5/329
Filed: 2003-07-25
Granted: 2005-05-27
Abstract: FIELD: medicine; medical engineering. 
     SUBSTANCE: method involves recording multichannel electroencephalogram, electrocardiogram record and carrying out functional test and computer analysis of electrophysiological signals synchronously with multichannel record of electroencephalogram and electrocardiogram in real time mode. Superslow brain activity is recorded, carotid and spinal artery pools rheoelectroencephalogram is recorded and photopletysmogram of fingers and/or toes is built and subelectrode resistance of electrodes for recording bioelectrical cerebral activity is measured. Physiological values of bioelectrical cerebral activity are calculated and visualized in integrated cardiac cycle time scale as absolute and relative values of alpha-activity, pathological slow wave activity in delta and theta wave bandwidth. Cerebral metabolism activity dynamics level values are calculated and visualized at constant potential level. Heart beat rate is determined from electrocardiogram, pulsating blood-filling of cerebral blood vessels are determined from rheological indices data. Peripheral blood vessel resistance level, peripheral blood vessel tonus are determined as peripheral photoplethysmogram pulsation amplitude, large blood vessel tonus is determined from pulse wave propagation time data beginning from Q-tooth signal of electrocardiogram to the beginning of systolic wave of peripheral photoplethysmogram. Postcapillary venular blood vessels tonus is determined from constant photoplethysmogram component. Functional brain state is determined from dynamic changes of physiological values before during and after the functional test. Device for evaluating functional brain state has in series connected multichannel analog-to-digital converter, microcomputer having galvanically isolated input/output ports and PC of standard configuration and electrode unit for reading bioelectric cerebral activity signals connected to multichannel bioelectric cerebral activity signals amplifier. Current and potential electrode unit for recording rheosignals, multichannel rheosignals amplifier, current rheosignals generator and synchronous rheosignals detector are available. The device additionally has two-frequency high precision current generator, master input of which is connected to microcomputer. The first output group is connected to working electrodes and the second one is connected to reference electrodes of electrode unit for reading bioelectrical cerebral activity signals. Lead switch is available with its first input group being connected to potential electrodes of current and potential electrodes unit for recording rheosignals. The second group of inputs is connected to outputs of current rheosignals oscillator. The first group of outputs is connected to current electrodes of current and potential electrodes unit for recording rheosignals. The second group of outputs is connected to inputs of synchronous detector of rheosignals. Demultiplexer input is connected to output of synchronous detector of rheosignals and its outputs are connected to multichannel rheosignals amplifier inputs. Outputs of multichannel bioelectrical cerebral activity signals amplifier, multichannel rheosignals amplifier and electrophysiological signal amplifier are connected to corresponding inputs of multichannel analog-to-digital converter. Microcomputer outputs are connected to control input of lead switch, control input of multichannel demultiplexer, control input of multichannel analog-to-digital converter and synchronization inputs of current rheosignals oscillator and synchronous detector of rheosignals. To measure subelectrode resistance, a signal from narrow bandwidth current generator of frequency f 1  exceeding the upper frequency f up  of signals under recording is supplied. A signal from narrow bandwidth current generator of frequency f 2 ≠ f 1 >f up  is supplied to reference electrode. Voltages are selected and measured at output of each amplifier with frequencies of f 1 , f 2  - U f1  and U f2  using narrow bandwidth filtering. Subelectrode resistance of each working electrode is determined from formula Z j =U jf1  :(J f1 xK j ), where Z j  is the subelectrode resistance of j-th electrode, U jf1  is the voltage at output from j-th amplifier with frequency of f 1 , K j  is the amplification coefficient of the j-th amplifier. Subelectrode resistance of reference electrode is determined from formula Z A =U jf2  :(J f2 xK j ), where Z A  is the subelectrode resistance of reference electrode, U jf2  is the voltage at output from j-th amplifier with frequency of f 2 , J f2  is the voltage of narrow bandwidth current oscillator with frequency of f 2 . 
     EFFECT: wide range of functional applications. 
     15 cl, 10 dwg