Patent No. 5279305 Electroencephalograph incorporating at least one wireless link

 

Patent No. 5279305

Electroencephalograph incorporating at least one wireless link (Zimmerman, et al., Jan 18, 1994)

Abstract

An improved EEG system (10) for telemetrically transmitting brain activity data from a portable transmitter to a processing console. The improved EEG system (10) includes a lightweight transmitter (12) which amplifies and digitizes the EEG signals from a set of electrodes (16) and transmits the digital signals along with a checksum to a receiver (14). The transmitter (12) may be carried by the subject under observation. The transmitter (12) of the preferred embodiment includes at least four circuit boards including a selectively interchangeable montage board (18), an amplifier board (24), a processor board (34), and a transmitter board (54). A signal is transmitted toward the receiver (14) and delivered to a conventional computer-controlled broadcast television tuner (80). The selected receiver (14) outputs data which is in an acceptable form for connection to standard microprocessor peripherals. The incoming data is processed and inspected to verify the validity thereof with any invalid data being marked as invalid. All data is then continuously and simultaneously displayed and recorded, with any invalid data being easily recognized as such and therefore disregarded.

Notes:  

Electroencephalograph incorporating at least one wireless link. Filed August 1992, granted January 1994. Not on previous list/s. Uses telemetry method for transmitting signals. Uses conventional computer controlled broadcast television tuner.

TECHNICAL FIELD

This invention relates to the field of monitoring brain activity. More specifically, this invention relates to an electroencephalograph (or EEG) device for monitoring and recording brain activity wherein wireless links are incorporated for communication between activity-detecting electrodes and a processing device.

BACKGROUND ART

In the field of monitoring brain activity the use of electroencephalograph devices (EEG's) is well known. EEG's are used to measure and record small electrical signals which occur on the surface of the scalp as a result of brain activity. Typically, an EEG system includes a plurality of electrodes attached at selected positions on the subject's scalp, a corresponding number of lead wires, and a processing console. Typically, each electrode is connected to the processing console via a separate lead wire. The processing console is provided for signal selection, amplification, and conditioning. Also included in EEG systems are means for measuring electrode impedance, calibrating equipment, and observing and permanently recording data processed by the processing console.

It is well known that the processing console and the observation and recording equipment are often incorporated within a single unit. The single unit, however, is too large to be easily transportable by the subject under observation. Further, because long wires between the electrodes and the processing console are impractical, the subject must remain relatively stationary when using most available EEG systems.

Some EEG systems have been developed to overcome the problem of the subject having to remain still during observation. These devices include portable recorders which may be carried by the subject under observation. These systems do not, however, include means for contemporaneous observation of the record. It is well known that such observation is often desired.

One method for making EEG measurements and contemporaneous observations more practical is to replace the wire links between the electrodes and the processing console with wireless links. Thus, situations such as those described above--i.e., when long wires might encumber other simultaneous attention needed by the subject or when the mobility of the subject might be impaired--would be at least partially resolved.

Other devices have been produced to monitor, process and record data received from the vital organs of a body. Typical of the art are those described in the following U.S. Patents:

____________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 3,253,588 R. F. Vuilleumier, et al. May 31, 1966

3,859,988 C. C. Lencioni, Jr. Jan. 14, 1975

3,943,918 R. A. Lewis Mar. 16, 1976

4,089,329 L. A. Couvillon, Jr., et al. May 16, 1978

4,186,749 T. B. Fryer Feb. 5, 1980

4,245,645 P. M. Arseneault, et al Jan. 20, 1981

4,279,258 E. R. John Jul. 21, 1981

4,409,987 R. A. McIntyre Oct. 18, 1983

4,471,786 H. Inagaki, et al. Sep. 18, 1984

4,495,950 D. E. Schneider Jan. 29, 1985

Of these patents, the U.S. Pat. Nos. 3,253,588 ('588); 3,943,918 ('918); 4,089,329 ('329); 4,186,749 ('749); and 4,471,786 ('786) patents disclose devices which incorporate telemetric transmittal of sensed data to a selected processing center. Each discloses a device using transmission over radio frequencies (r-f) using amplitude modulation (AM) or frequency modulation (FM) methods similar to those used for broadcast radio. The transmitted signals are thus subject to the same interference and distortion as broadcast radio signals.

It is well known that FM transmissions are more reliable than AM transmissions. However, it is also known that FM signals are subject to distortion and interference from signals broadcast from other stations. Though in the field of radio broadcasting these disturbances are mostly annoyances to signal receptors, in the field of EEG monitoring such disturbances will provide erroneous data concerning the brain activity of the subject. In this context, distortion and interference is detrimental to accurate analysis and is therefore undesirable.

Therefore, it is an object of this invention to provide a means for transmitting signals detected by electrodes placed on a subject's body to a signal processor using telemetric methods.

It is also an object of the present invention to substantially reduce the distortion and interference typically present in standard transmission of radio frequency signals.

Another object of the present invention is to provide an electroencephalographic monitoring and recording device wherein digital data communications is incorporated to provide accurate transmission of detected brain activity signals.

Still another object of the present invention is to provide a lightweight transmitter for amplifying and digitizing EEG signals from the electrodes.

Yet another object of the present invention is to provide a means whereby the data transmitted may be checked and verified to insure that data received by a receiving device is valid, and further that any invalid data received is ignored.

DISCLOSURE OF THE INVENTION

Other objects and advantages will be accomplished by the present invention which serves to detect brain activity in a subject and transmit the detected signals telemetrically to a processing center. The telemetric method used incorporates digital data communications in order to provide accurate transmittal of the detected signals. The improved EEG system of the present invention includes a lightweight transmitter which amplifies and digitizes the EEG signals from a set of electrodes and transmits the digital signals along with a checksum to a receiver. The checksum allows the receiver to verify the validity of the received data and to denote any data which has been distorted or subjected to interference between the transmitter and receiver.

The transmitter is designed to be carried by the subject under observation. A plurality of electrodes are electrically connected to the transmitter and are attached to the subject in a conventional fashion. The transmitter of the illustrated embodiment includes four circuit boards upon which the electronic circuitry is configured. These circuit boards include a selectively interchangeable montage board, an amplifier board, a processor board, and a transmitter board.

The montage board is provided for selectively configuring the connections between the electrodes and the remainder of the EEG system. The montage board may be selectively interchanged to change the configuration of the electrode connections.

The amplifier board is provided for amplifying the small signals detected by the electrodes. In the preferred embodiment, the amplifier board includes a plurality of signal amplifiers. The connection of the amplifiers to the electrodes is determined by the selected montage board installed with a selected pair of electrodes being connected to the respected inputs of a signal amplifier.

The processor board digitizes the amplified signals and converts them to a form suitable for transmission. The processor board includes a plurality of inputs for receiving the individual outputs of the signal amplifiers. In the preferred embodiment, the processor board is programmed to control multiplexing, conversion of the selected amplifier outputs within the A-D converter to binary-coded digital data, calculation of a binary checksum number, conversion of the binary-coded digital numbers and checksum number to a selected code suitable for transmission of digital data, and generation of a precisely-timed serial data stream from the numbers coded in the selected code.

The transmitter board further converts the signals into radio frequency (r-f) signals for transmission. The serial data stream generated by the microprocessor is delivered through an amplifier to an oscillator carried by the transmitter board. The amplifier is also used to select the rate of frequency change of the oscillator in order to conform to regulations imposed by the Federal Communications Commission (FCC) and further to meet other selected output requirements as well. The oscillator is also controlled by a phase-locked-loop system which will allow for the control of the center frequency of the oscillator.

The output of the oscillator is connected to an antenna via a trap, the trap serving to filter out unwanted harmonic frequencies in order to avoid interference with other transmissions.

The signal from the transmitter is received by the receiver antenna and delivered to a conventional computer-controlled broadcast television tuner. The output of the TV tuner is connected to a selected receiver. The combination of the TV tuner and the selected receiver form a double-superheterodyne receiver capable of rejecting out-of-band image signals.

The selected receiver outputs a reconstituted serial data stream substantially identical to the selectively-coded serial data stream generated by a microcontroller incorporated by the transmitter processor board. The data stream is sent to a decoder for converting the coded data stream to a synchronous nonreturn-to-zero code (NRZ) serial data stream. The synchronous NRZ serial data is an acceptable form for connection to standard microprocessor peripherals.

The incoming data is processed by a selected microprocessor which inspects the checksum generated by the transmitter microcontroller. For any checksum detected to be incorrect, the associated data is marked such that observation of the distorted data will reflect the distortion and can be easily disregarded. All data, whether valid or invalid, is sent to a second communications interface configured to perform as a standard asynchronous serial port which may be connected to any standard computer serial port. The data may then be displayed and recorded as desired.

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While a preferred embodiment has been shown and described, it will be understood that it is not intended to limit the disclosure, but rather it is intended to cover all modifications and alternate methods falling within the spirit and the scope of the invention as defined in the appended claims.