Patent Publication Number: US-2023157620-A1

Title: Method and System for Data Synchronization

Description:
CROSS REFERENCE 
     The present application is a division application of U.S. patent application Ser. No. 16/667,570, entitled “Method and System for Data Synchronization” and filed on Oct. 29, 2019, which relies on U.S. Patent Provisional Application No. 62/752,675, of the same title and filed on Oct. 30, 2018, for priority, both of which are herein incorporated by reference in their entirety. 
    
    
     FIELD 
     The present specification generally relates to the field of neuro-monitoring applications and more specifically to a system and method for synchronizing multiple amplifiers being used in conjunction for amplifying captured electroencephalography (EEG) signals and other biopotential signals. 
     BACKGROUND 
     Several medical procedures involve deploying multiple sensors on the human body for the recording and monitoring of data required for patient care. Information, such as vital health parameters, cardiac activity, bio-chemical activity, electrical activity in the brain, gastric activity and physiological data, is usually recorded through on-body or implanted sensors/electrodes which are connected through a wired or wireless link. Typical patient monitoring systems comprise a control unit connected through a wire to one or more electrodes coupled to the specific body parts of the patient. In some applications, such as with pulse oximeter or EKG (electrocardiograph) devices, the electrodes coupled to the body are easily managed as there are not too many. However, with procedures that require a large number of electrodes to be coupled to the human body, the overall set up, placement and management of electrodes is a cumbersome process. 
     One such procedure that requires a large number of electrodes is Long Term Electroencephalography (EEG) Monitoring (LTM). The purpose of LTM is to detect abnormal brain activity. The presence of abnormal brain activity may require medications and/or surgical interventions. During surgical procedures, LTM may reduce the risk to the patient of iatrogenic damage to the nervous system, and/or to provide functional guidance to the surgeon. Generally, neuromonitoring procedures such as EEG involve a large number of electrodes coupled to the human body. In an EEG procedure, the electrodes are used to record and monitor the electrical activity corresponding to various parts of the brain for detection and treatment of various ailments such as epilepsy, sleep disorders, tumors and coma. EEG procedures are either non-invasive or invasive. In non-invasive EEG, a number of surface electrodes are deployed on the human scalp for recording electrical activity in portions of the underlying brain. In invasive EEG, through surgical intervention, the electrodes are placed directly over sections of the brain, in the form of a strip or grid, or are positioned in the deeper areas of the brain in the form of a depth electrode. All of these electrode types are coupled to a wire lead which, in turn, is connected to a medical system adapted to receive and transmit electrical signals. The electrical activity pattern sensed by various electrodes is analyzed using standard algorithms to localize or spot the portion of brain which is responsible for causing the specific ailment. 
     The number of electrodes in EEG systems typically varies between 21 and 256. Increasing the number of electrodes in EEG procedures helps decrease the localization error and thus more ably assist the physician to better plan for surgical procedures. Accordingly, advanced EEG systems involve a high density electrode configuration with more than 256 electrodes, possibly 1024 electrodes, for separately mapping the electrical activity corresponding to every portion of the brain. However, the overall set up and verification process becomes more time consuming and error prone as the number of electrodes increases in the EEG procedures. 
     Most EEG monitoring systems comprise an amplifier for amplifying and digitizing the recorded signals before analyzing the signals. In EEG systems consisting of more than one amplifier, the data from each amplifier must be time synchronized with each other. Data synchronization is important since cerebral events such as seizures have a temporal significance and the EEG signals recorded from a patient may be acquired by more than one amplifier, as is the case in high channel count intracranial EEG monitoring systems. Also, any difference in sample rate between the amplifiers will result in beat frequency noise when the EEG channels in one amplifier are fed as reference to the EEG channels of another amplifier. Beat frequency noise is a periodic artifact added to the EEG signal and is a result of one amplifier&#39;s digitizer&#39;s (ADCs) sampling a common mode noise of another amplifier as a differential signal. The noise may inhibit analyzing the EEG signals. 
     Known methods of synchronizing multiple amplifiers include running multiple synchronizing clocks and signals from one amplifier to another or using high precision temperature controlled oscillators in each of the amplifiers, the latter of which requires extremely stable clock oscillators that are typically temperature controlled and an order of magnitude higher in cost than a voltage controlled oscillator, require much more power than a voltage controlled oscillator, and are also physically much larger in size. 
     The other method of synchronizing the data from different amplifiers comprises sharing the sample clocks of the amplifiers and sharing the ‘convert start’ signals among all the analog to digital converters (ADC) of all the amplifiers. Though it is possible to share such signals between all of the amplifiers, this is not a desirable topology because specialized and high current consumption equipment and cables would be required to do so and also because the ADC signals can be corrupted by electromagnetic interference, resulting in unexpected functioning of the ADCs. 
     Hence what is needed is a less complex method of synchronizing the data acquisition from multiple amplifiers than that provided by prior art. What is also needed is a method of synchronization that does not require specialized components, is cost effective and is not susceptible to interference from electrostatic discharge (ESD) interference, electric fast transient (EFT) interference, or other electromagnetic interferences. Such a method would preferably eliminate the need for distributing data from a high speed clock to each of the amplifiers. Distribution of high speed clock data between amplifiers is not desirable since this requires differential circuitry and cabling, and is susceptible to interference from ESD, EFT, and other electromagnetic interference. 
     SUMMARY 
     The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods, which are meant to be exemplary and illustrative, and not limiting in scope. The present application discloses numerous embodiments. 
     The present specification discloses a system for monitoring EEG signals comprising: a plurality of EEG sensors positioned on a layer of tissue for capturing EEG signals of a patient; at least one amplifier coupled to each of the plurality of EEG sensors, wherein the at least one amplifier is configured to amplify the captured EEG signals; and a first oscillator configured to generate a synchronizing signal; wherein the at least one amplifier comprises: an input for receiving the synchronizing signal transmitted from the first oscillator; a second oscillator; an analog to digital converter coupled with the second oscillator and configured to digitize the captured EEG signals; and a microcontroller configured to control a frequency of the second oscillator and an operation of the analog to digital converter (ADC) based on the synchronizing signal. 
     Optionally, the first oscillator is configured to generate the synchronizing signal having a frequency in a range of 0.1 Hz to 10 kHz. 
     Optionally, the second oscillator is voltage controlled. 
     Optionally, the plurality of EEG sensors are configured to monitor intracranial EEG signals. 
     Optionally, the system further comprises a computing device in data communication with the plurality of amplifiers for processing the amplified EEG signals. Optionally, the system further comprises a display in data communication with the computing device for displaying the amplified EEG signals. 
     Optionally, the input comprises a signal isolator configured to receive the synchronizing signal. Optionally, the signal isolator comprises one or more isolated DC-DC power converters. 
     Optionally, the synchronizing signal has a frequency of 1 Hz. 
     Optionally, the microcontroller comprises a digital to analog (DAC) converter and the microcontroller is configured to adjust the second oscillator by setting the DAC to a corresponding voltage. 
     Optionally, the at least one amplifier further comprises an internal timer and the microcontroller is configured to measure the period of the synchronizing signal using the internal timer. Optionally, the internal timer has a resolution in a microsecond numerical range. 
     Optionally, the at least one amplifier further comprises a filter configured to filter out high frequency noise present in an analog voltage transmission from the microcontroller, wherein the high frequency noise has a frequency greater than 2 kHz. 
     Optionally, the at least one amplifier comprises at least one unique amplifier in dedicated data communication with each of the plurality of EEG sensors. 
     The present specification also discloses a method for synchronizing EEG signals measured by an EEG monitoring system, wherein the EEG monitoring system comprises a plurality of EEG sensors positioned on a layer of tissue and wherein each of the plurality of EEG sensors is configured to capture EEG signals of a patient, at least one amplifier coupled to each of the plurality of EEG sensors and configured to amplify the captured EEG signals, and a first oscillator, wherein the at least one amplifier comprises an input for receiving a synchronizing signal from the first oscillator, the method comprising: distributing the synchronizing signal from the first oscillator to each of the at least one amplifier; measuring a period of the synchronizing signal; adjusting a second oscillator, having a frequency, in the at least one amplifier to match a timer count based on the period of the synchronizing signal; determining a function of the frequency of the second oscillator frequency to produce a clock signal; and adjusting a frequency of each of the second oscillators such that the frequencies of the second oscillators are identical. 
     Optionally, the first oscillator is configured to generate the synchronizing signal having a frequency in a range of 0.1 Hz to 10 kHz. 
     Optionally, the second oscillator is voltage controlled. 
     Optionally, the function of the frequency of the second oscillator frequency is determined by dividing the frequency to produce the clock signal. Optionally, the method further comprises using the clock signal to drive the analog to digital converter clock signal. Optionally, the at least one amplifier comprises the second oscillator, the analog to digital converter coupled to the second oscillator and configured to digitize the captured EEG signals, and a microcontroller configured to control the frequency of the second oscillator and an operation of the analog to digital converter based on the synchronizing signal. Optionally, the microcontroller comprises a signal isolator wherein the signal isolator comprises isolated DC-DC power converters. 
     Optionally, the method further comprises transmitting the amplified EEG signals to a computing device, wherein the computing device is configured to process the amplified EEG signals. 
     Optionally, the synchronizing signal has a frequency of 1 Hz. 
     Optionally, the microcontroller includes a digital to analog (DAC) converter and the microcontroller is configured to adjust the second oscillator by setting the DAC to a corresponding voltage. 
     Optionally, the at least one amplifier further comprises an internal timer having microsecond resolution and the microcontroller is configured to measure a period of the synchronizing signal using the internal timer. 
     Optionally, the at least one amplifier further comprises a filter configured to filter out high frequency noise, having a value range greater than 2 kHz, present in an analog voltage signal from the microcontroller output. 
     The present specification also discloses a system for monitoring EEG signals comprising: a plurality of EEG sensors spatially positioned on a layer of tissue for capturing EEG signals of a patient; a plurality of amplifiers coupled with the EEG sensors for amplifying the captured signals; and a low frequency oscillator; wherein each amplifier comprises: an input for receiving a low frequency synchronizing signal from the low frequency oscillator wherein the low frequency synchronizing signal is configured to be distributed to each amplifier of the plurality of amplifiers; a voltage controlled oscillator; an analog to digital converter coupled with the voltage controlled oscillator for digitizing the captured signals; and a microcontroller for controlling a frequency of the voltage controlled oscillator and operation of the analog to digital converter (ADC) based on the synchronizing signal. 
     The system may be used to monitor intracranial EEG signals. 
     Optionally, the system further comprises a computing device in data communication with the plurality of amplifiers for processing the amplified signals. Optionally, the system further comprises a display in data communication with the computing device for displaying the amplified signals. 
     Optionally, the input comprises a signal isolator for receiving the synchronizing signal. The signal isolator may comprise isolated DC-DC power converters. 
     Optionally, the synchronizing signal has a frequency of 1 Hz. 
     Optionally, the microcontroller includes an internal digital to analog (DAC) converter wherein the microcontroller is configured to adjust the voltage controlled oscillator by setting the internal DAC to a corresponding voltage. 
     Optionally, each amplifier further comprises an internal timer with microsecond resolution wherein the microcontroller is configured to measure the period of the synchronizing signal using the internal timer. 
     Optionally, each amplifier further comprises a low pass filter configured to filter out high frequency noise on analog voltage from the microcontroller output. 
     The present specification also discloses a method for synchronizing EEG signals measured by a an EEG monitoring system, wherein the EEG monitoring system comprises a plurality of EEG sensors spatially positioned on a layer of tissue for capturing EEG signals of a patient, a plurality of amplifiers coupled with the EEG sensors for amplifying the captured signals, and a low frequency oscillator, wherein each amplifier comprises: an input for receiving a low frequency synchronizing signal from the low frequency oscillator wherein the low frequency synchronizing signal is configured to be distributed to each amplifier of the plurality of amplifiers; a voltage controlled oscillator; an analog to digital converter coupled with the voltage controlled oscillator for digitizing the captured signals; and a microcontroller for controlling a frequency of the voltage controlled oscillator and operation of the analog to digital converter (ADC) based on the synchronizing signal, the method comprising: distributing a low frequency synchronizing signal from the low frequency oscillator to each of the plurality of amplifiers; measuring a period of the low frequency synchronizing signal; adjusting the voltage controlled oscillator of an amplifier of the plurality of amplifiers to match a timer count based on the period of the low frequency synchronizing signal; dividing a voltage controlled oscillator frequency to produce analog to digital converter clock and convert start signals; and adjusting the frequency of each voltage controlled oscillator of each of the plurality of amplifiers such that the frequency of each voltage controlled oscillator is identical. 
     The method may be used to monitor intracranial EEG signals. 
     Optionally, the EEG monitoring system further comprises a computing device in data communication with the plurality of amplifiers for processing the amplified signals. Optionally, the EEG monitoring system further comprises a display in data communication with the computing device for displaying the amplified signals. 
     Optionally, each input comprises a signal isolator for receiving the synchronizing signal. The signal isolator may comprise isolated DC-DC power converters. 
     Optionally, the synchronizing signal has a frequency of 1 Hz. 
     Optionally, the microcontroller includes an internal digital to analog (DAC) converter wherein the microcontroller is configured to adjust the voltage controlled oscillator by setting the internal DAC to a corresponding voltage. 
     Optionally, each amplifier further comprises an internal timer with microsecond resolution wherein the microcontroller is configured to measure the period of the synchronizing signal using the internal timer. 
     Optionally, each amplifier further comprises a low pass filter configured to filter out high frequency noise on analog voltage from the microcontroller output. 
     The aforementioned and other embodiments of the present shall be described in greater depth in the drawings and detailed description provided below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present specification will be further appreciated, as they become better understood by reference to the following detailed description when considered in connection with the accompanying drawings: 
         FIG.  1    shows a block diagram of a conventional medical system comprising a large number of electrodes deployed on a patient body; 
         FIG.  2    illustrates an electroencephalography (EEG) system for detecting, diagnosing, or predicting neurological events from EEG signals, in accordance with some embodiments of the present specification; 
         FIG.  3    is a block diagram illustrating an amplifier used for amplifying EEG signals recorded from a patient&#39;s brain, in accordance with an embodiment of the present specification; 
         FIG.  4 A  is a block diagram illustrating a system comprising a plurality of amplifiers synchronized operatively for amplifying EEG signals recorded from a patient&#39;s brain, in accordance with an embodiment of the present specification; 
         FIG.  4 B  illustrates a block diagram of an EEG system incorporating a plurality of amplifiers, in accordance with an embodiment of the present specification; and 
         FIG.  5    is a flowchart illustrating the steps involved in a method of distributing a low frequency signal to a plurality of synchronized amplifiers to measure EEG signals, in accordance with an embodiment of the present specification. 
     
    
    
     DETAILED DESCRIPTION 
     The present specification enables synchronization of EEG data between two or more amplifiers using a low frequency synchronizing signal that is shared using low power circuits and standard cables. By using the method of the present specification, electromagnetic interferences are filtered out since the frequencies of the low speed shared signal and of the interferences do not overlap. 
     In various embodiments, the present specification provides a simple and low cost method of synchronizing the data acquisition of multiple amplifiers during EEG monitoring. This method eliminates the need for distributing data from a high speed clock to each of the multiple amplifiers, thereby eliminating the need for high power consumption and specialized components/cables. 
     In an embodiment, the method of the present specification comprises distributing a low frequency clock among a plurality of amplifiers for synchronizing the data acquired by said amplifiers during EEG monitoring. The low frequency clock uses single ended circuitry and cabling whereby high frequency electromagnetic interference can be filtered out from the clock signal. 
     In various embodiments, the methods and systems of the present specification enable the synchronizing of a sample rate of EEG data acquired on different devices (amplifiers) with only a low frequency synchronizing signal. In some embodiments, a low frequency synchronizing signal is transmitted to the devices to be synchronized, wherein the term low frequency, in the context of a synchronizing signal, refers to a range of 0.1 Hz to 10 kHz, with a preferred range of 0.5 Hz to 2 Hz. It should be appreciated that the 0.5 Hz to 2 Hz range leads to a more accurate synchronization process. Each device measures the period of the synchronizing signal using an internal timer with microsecond resolution. The device then adjusts its microcontroller clock so that the expected number of ticks occurs between the low frequency synchronizing signal edges (for example, 1,000,000). This is done by adjusting the voltage to an external voltage-controlled oscillator in finite steps using a digital to analog converter (DAC) internal to the microcontroller. These adjustments can continue, to counter clock drift over time, in order to maintain synchronization. 
     A “computing device” is at least one of a cellular phone, PDA, smart phone, tablet computing device, patient monitor, custom kiosk, or other computing device capable of executing programmatic instructions. It should further be appreciated that each device and monitoring system may have wireless and wired receivers and transmitters capable of sending and receiving data. Each “computing device” may be coupled to at least one display, which displays information about the patient parameters and the functioning of the system, by means of a GUI. The GUI also presents various menus that allow users to configure settings according to their requirements. The system further comprises at least one processor to control the operation of the entire system and its components. It should further be appreciated that the at least one processor is capable of processing programmatic instructions, has a memory capable of storing programmatic instructions, and employs software comprised of a plurality of programmatic instructions for performing the processes described herein. In one embodiment, the at least one processor is a computing device capable of receiving, executing, and transmitting a plurality of programmatic instructions stored on a volatile or non-volatile computer readable medium. In addition, the software comprised of a plurality of programmatic instructions for performing the processes described herein may be implemented by a computer processor capable of processing programmatic instructions and a memory capable of storing programmatic instructions. 
     “Electrode” refers to a conductor used to establish electrical contact with a nonmetallic part of a circuit such as a patient&#39;s body. EEG electrodes are small metal discs, grids, strips or cylinders usually made of stainless steel, platinum, tin, gold or silver covered with a silver chloride coating. They are typically placed on the scalp on predetermined locations but may also be placed as intracranial electrodes directly on the surface of the brain or implanted into the brain to record electrical activity from the cerebral cortex. 
     An “electrode grid” is a thin sheet of material with multiple small (roughly a couple mm in size) recording electrodes implanted within it. These are placed directly on the surface of the brain and have the advantage of recording the EEG without the interference of the skin, fat tissue, muscle, and bone that may limit scalp EEG. Shapes and sizes of these sheets are chosen to best conform to the surface of the brain and the area of interest. 
     A “depth electrode” refers to small wires that are implanted within the brain itself. Each wire has electrodes which surround it. These electrodes are able to record brain activity along the entire length of the implanted wire. They have the advantage of recording activity from structures deeper in the brain. They can be implanted through small skin pokes. 
     The present specification is directed towards multiple embodiments. The following disclosure is provided in order to enable a person having ordinary skill in the art to practice the invention. Language used in this specification should not be interpreted as a general disavowal of any one specific embodiment or used to limit the claims beyond the meaning of the terms used therein. The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Also, the terminology and phraseology used is for the purpose of describing exemplary embodiments and should not be considered limiting. Thus, the present invention is to be accorded the widest scope encompassing numerous alternatives, modifications and equivalents consistent with the principles and features disclosed. For purpose of clarity, details relating to technical material that is known in the technical fields related to the invention have not been described in detail so as not to unnecessarily obscure the present invention. 
     In the description and claims of the application, each of the words “comprise” “include” and “have”, and forms thereof, are not necessarily limited to members in a list with which the words may be associated. It should be noted herein that any feature or component described in association with a specific embodiment may be used and implemented with any other embodiment unless clearly indicated otherwise. 
     As used herein, the indefinite articles “a” and “an” mean “at least one” or “one or more” unless the context clearly dictates otherwise. 
       FIG.  1    shows a block diagram of a conventional medical system  100  comprising a large number of electrodes deployed on the body of a patient  102 . The medical device  101  represents a conventional neuromonitoring medical system, such as an EEG (electroencephalography) system, which comprises a large number of electrodes for monitoring a neurological state of a patient for diagnosis and preventive treatment of certain diseases and for monitoring patients during anesthesia, among other procedures. As shown in  FIG.  1   , the medical device  101  is coupled to the patient  102  through a plurality of electrical leads  103  such that each of the leads  103  is coupled to an electrode (not shown) positioned at an appropriate location on the body of the patient  102 . 
       FIG.  2    illustrates an electroencephalography (EEG) system  200  for detecting, diagnosing, or predicting neurological events from EEG signals, in accordance with some embodiments of the present specification. The figure shows a plurality of EEG sensors or electrodes  205  spatially positioned on a layer of tissue such as the scalp of a patient  215 . In other embodiments, the plurality of electrodes is positioned intracranially, directly on the brain. For example, in some embodiments, the plurality of electrodes is placed on the brain by skull resection or via burr holes. The plurality of electrodes  205  are electrically connected with a multi-channel amplifier  220  that is in data communication with a computing device  240 . The computing device  240  is in data communication with a display unit  230  and at least one database  235 . 
     In various embodiments, the plurality of electrodes  205  are small metal discs, strips, grids, and/or cylinders typically made of stainless steel, platinum, tin, gold or silver covered with a silver chloride coating. The plurality of electrodes  205  sense electrical signals (EEG signals) from the patient&#39;s brain and conduct the analog signals over an electrical connection link to the multi-channel amplifier  220  that amplifies the signals, converts the signals from an analog EEG data set to a digital EEG data set, and communicates the resultant digital EEG signal to the computing device  240  over a communication link. In embodiments, the communication link may be wired or wireless links. In various embodiments, more than one amplifier  220  may be used for acquiring and amplifying the voltage sensed by the electrodes  205  in the EEG system. 
     The computing device  240  includes an input/output controller, at least one communications interface and system memory. The system memory includes at least one random access memory (RAM) and at least one read-only memory (ROM). These elements are in communication with a central processing unit (CPU) to enable operation of the computing device  240 . In various embodiments, the computing device  240  may be a conventional standalone computer or alternatively, the functions of the computing device  240  may be distributed across multiple computer systems and architectures. For example, in a distributed architecture, the at least one database  235  and processing circuitry are housed in separate units or locations. Some units perform primary processing functions and contain at a minimum a general controller or a processing circuitry and a system memory. 
     The computing device  240  executes EEG software  245  that implements a plurality of programmatic instructions or code to process, store, retrieve and display, on the display unit  230 , the patient&#39;s EEG data. In embodiments, the EEG software  245  processes the received digital EEG signals, extracts parameters that characterize the EEG data, and generates a display of the data for a user. The processed EEG data is either displayed on the display unit  230  in real-time or stored in at least one database  235  for later analyses. 
     In some embodiments, execution of sequences of programmatic instructions enables or causes the CPU to perform various functions and processes. In alternate embodiments, hard-wired circuitry may be used in place of, or in combination with, software instructions for implementation of the processes of systems and methods described in this specification. Thus, the systems and methods described are not limited to any specific combination of hardware and software. 
       FIG.  3    is a block diagram illustrating an amplifier  300  used for amplifying EEG signals recorded from a patient&#39;s brain, in accordance with an embodiment of the present specification. The amplifier  300  comprises a microcontroller  302 , a voltage controlled oscillator  304 , an analog-to-digital converter (ADC)  306  and a low pass filter  308 . As shown, EEG analog signals  310  recorded from a patient&#39;s brain by using a plurality of EEG electrodes are transmitted to the ADC  306  which converts the input analog signals to digital signals for output to the microcontroller  302 . The microcontroller  302  controls the operation of the voltage controlled oscillator  304  by controlling the voltage on the DAC output  307 , thereby adjusting the frequency of the voltage controlled oscillator  304  to a predefined frequency. More specifically, the microcontroller  302 , at the DAC output  307 , modulates the voltage amplitude and/or frequency which, in turn, controls the frequency at which the voltage controlled oscillator  304  oscillates. The microcontroller  302  controls the ADC  306  by generating the clock and start signals of the ADC  306 . The microcontroller  302  bases the control of the voltage control oscillator  304  and the ADC  306  on the input timer/frequency  301 . The low pass filter  308  filters out high frequency noise above 2 kHz on the analog voltage from the microcontroller DAC output  307  so as to provide a useful DC signal input  311  to the oscillator  304  thereby enabling the oscillator  304  to produce a stable oscillator frequency at an oscillator (OSC) input  309  of the microcontroller  302 . 
       FIG.  4 A  is a block diagram illustrating a system  400  comprising a plurality of amplifiers synchronized operatively for amplifying EEG signals recorded from a patient&#39;s brain, in accordance with an embodiment of the present specification. Each of the plurality of amplifiers  402   a  through  402   n  comprises a signal isolator  405 , a microcontroller  406 , a voltage controlled oscillator  408 , an analog to digital converter  410  and a low pass filter  412 . As shown, a low frequency oscillator  401  provides a low frequency synchronizing signal which is distributed to each of the plurality of amplifiers  402   a  through  402   n  that operate in conjunction to amplify and digitize intracranial EEG signals. In some embodiments, the synchronizing signal has a frequency in a range of 0.1 Hz to 10 kHz, more preferably in a range of 0.5 Hz to 2 Hz, and most preferably around 1 Hz. 
     In some embodiments, the low frequency oscillator  401  is external to the amplifiers  402   a  through  402   n . Each signal isolator  405 , associated with each of the plurality of amplifiers  402   a  through  402   n , electrically isolates each of the plurality of amplifiers  402   a  through  402   n  from ground. In some embodiments, each signal isolator  405  comprises isolated DC-DC power converters and provides an isolation barrier over which a low frequency signal can be easily coupled. Each voltage controlled oscillator  408  provides a master clock to the microcontroller  406  of its respective amplifier. In various embodiments, any synchronizing signal frequency may be provided by the low frequency oscillator  401 . However, a synchronizing signal frequency lower than 1 Hz increases the time taken to synchronize the signal while a synchronizing signal frequency higher than 1 Hz requires more microcontroller resources. 
     In embodiments, cables  403  are used to supply the synchronizing signal from the low frequency oscillator  401  to each of the plurality of amplifiers  402   a  through  402   n . In an embodiment, the synchronizing signal is carried by a 28 AWG cable/conductor. In alternate embodiments, cables having other AWG values may also be used. 
     During operation, a microcontroller  406  of each of the amplifiers  402   a  through  402   n  receives the 1 Hz synchronizing signal from the low frequency oscillator  401  via a timer input  407  and measures the period of the 1 Hz synchronizing signal using an internal timer. In some embodiments, the internal timer measures the period of the 1 Hz synchronizing signal with microsecond resolution. The microcontroller  406  then adjusts an operational frequency of the voltage controlled oscillator  408  by setting its internal DAC to a voltage value within a predefined range until the measured period of the synchronizing signal at timer input  407  matches a defined timer count based on the expected period of the synchronizing signal. 
     In some embodiments, the synchronization signal is a square wave with a frequency of 1 Hz and 50% duty cycle (high for half of the period, low for half of the period). The square wave is defined by “signal edges” referring to the rising edges of the square wave. Alternatively, “signal edges” may also refer to the falling edges of the square wave. In embodiments, one million “ticks” occur in a timer since a previous 1 Hz sync edge. In embodiments, if a timer is operated with microsecond resolution and the value of the timer is captured at each rising edge of the 1 Hz synchronization signal, one would expect a delta of 1,000,000 between consecutive timer captures since there are 1,000,000 microseconds in 1 second (1 Hz). Since the voltage controlled oscillator  408  is providing the master clock to the microcontroller  406 , adjusting the operational frequency of the voltage controlled oscillator  408  will adjust the frequency of all microcontroller clocks and timing signals produced by the microcontroller  406 . The microcontroller  406  adjusts the operational frequency of the voltage controlled oscillator  408  by setting the internal DAC of the microcontroller  406  to a certain voltage value which is then sent to the voltage controlled oscillator  408  by the microcontroller  406 . In embodiments, to maintain synchronization, the adjustments of the operational frequency of the voltage controlled oscillator  408  continue as the clocks drift over time and temperature. In some embodiments, the internal DAC of the microcontroller  406  is set to a voltage value in a range of 0 to 3.3 V. 
     Thereafter, the operational frequency of the voltage controlled oscillator  408  is divided by the microcontroller  406  to produce clock and ‘convert start’ signals of the analog to digital converter (ADC)  410 . Both the clock and ‘convert start’ signals determine the sample rate and timing of the analog to digital conversion within the ADC  410 . Thus, the ADC  410  is synchronized to the 1 Hz signal. 
     Each microcontroller  406  in each of the other amplifiers  402   n  adjusts the frequency of its associated voltage controlled oscillator so that its frequency is identical to the frequency of the voltage controlled oscillator  408 . In some embodiments, the voltage controlled oscillator  408  can be adjusted after multiple 1 Hz synchronizing signal periods or at any other frequency interval that results in a desired accuracy of synchronization of the amplifiers. For example, in an embodiment, the microcontroller  406  counts, using its internal timer, the number of microsecond ticks that occur over four 1 Hz synchronizing signal periods and adjust its clock until it reaches the desired count. This allows for greater accuracy of synchronization but with a tradeoff of more time elapsed to reach synchronization. 
     Without the voltage controlled oscillator  408 , the use of low frequency synchronizing signal is restricted to an accuracy of approximately 10 μsec of synchronization using calculations done on a host PC system for time-stamped data and stimulations. The microcontroller clocks are allowed to drift in this timing scheme with the host PC correcting the timestamps for the calculated drift. With the addition of the voltage controlled oscillator  408  and the method of measuring and compensating for oscillator inaccuracy, synchronization better than 1 μsec is achieved at the microcontroller clock level. This tighter frequency accuracy is necessary to avoid beat frequencies. 
       FIG.  4 B  illustrates a block diagram of an EEG system incorporating a plurality of amplifiers, in accordance with an embodiment of the present specification. Referring to  FIG.  4 B , a plurality of 128 channel amplifiers  450  receive input EEG signals via 128×4 electrode wires captured by a plurality of electrodes  452  connected to a patient. Digitized and amplified signals travel via a plurality of power/signal synchronization cables  454  between each of the plurality of amplifiers  450 . A first power/signal synchronization cable  455  carries the digitized and amplified signal communicated between each of the plurality of amplifiers  450  to a power unit comprising a low frequency oscillator  456  which is used to synchronize the signals received from the plurality of amplifiers  450 . The synchronized signals are transferred via data cables  458  to a computing device  460  (similar to computing device  240  described with reference to  FIG.  2 A ) and are displayed for analysis on a display device  462  coupled with the computing device  460 . 
       FIG.  5    is a flowchart illustrating a plurality of exemplary steps involved in a method of distributing a low frequency signal to a plurality of amplifiers for synchronization and to measure EEG signals, in accordance with an embodiment of the present specification. At step  502 , a low frequency oscillator of an EEG monitoring system of the present specification distributes a low frequency synchronizing signal to a plurality of amplifiers that are in data communication with the low frequency oscillator. In some embodiments, the low frequency synchronizing signal is a 1 Hz synchronizing signal. 
     At step  504 , a microcontroller in each of the plurality of amplifiers measures a period of the low frequency synchronizing signal using an internal timer. In some embodiments, the internal timer measures the period of the low frequency synchronizing signal with microsecond resolution. The microcontroller then adjusts an operational frequency of a voltage controlled oscillator of the amplifier by setting an internal DAC of the microcontroller to a voltage value, at step  506 , until the measured period of the low frequency synchronizing signal matches a timer count based on the expected period of the low frequency synchronizing signal. At step  508 , the microcontroller sends the voltage value of the internal DAC to the voltage controlled oscillator to enable the voltage controlled oscillator to produce a stable frequency to at an oscillator (OSC) input of the microcontroller. 
     At step  510 , the adjusted operational frequency of the voltage controlled oscillator is divided by the microcontroller to produce clock and convert start signals of an analog to digital converted (ADC) of the amplifier. Finally, at step  512 , each microcontroller in each of the other amplifiers (of the plurality of amplifiers) adjusts the frequency of its associated voltage controlled oscillator so that the frequency of each voltage controlled oscillator of each amplifier of the plurality of amplifiers is identical. In some embodiments, the frequency adjustment occurs at twice the low frequency synchronizing signal or at any interval that will result in the desired accuracy of synchronization of the amplifiers. 
     The above examples are merely illustrative of the many applications of the system and method of present specification. Although only a few embodiments of the present specification have been described herein, it should be understood that the present specification might be embodied in many other specific forms without departing from the spirit or scope of the specification. Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the specification may be modified within the scope of the appended claims.