Electroencephalograph

• US 4,236,511 A
• Filed: 06/09/1978
• Issued: 12/02/1980
• Est. Priority Date: 06/09/1978
• Status: Expired due to Term

• Current Assignee: Beckman Instruments, Inc. (Danaher Corporation)
• Original Assignee: Beckman Instruments, Inc. (Danaher Corporation)
• Inventors: Loeb, Phillip J.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/914,273
• Time in Patent Office: 907 Days
• Field of Search: 128/2.06 B, 128/2.06 F, 128/2.1 A, 128/2.1 B, 128/696, 128/706, 128/731, 128/902, 128/903, 128/904
• US Class Current: 600/544
• CPC Class Codes: A61B 5/276 Protection against electrode failure
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/31 for electroencephalography [EEG]
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16

Abstract

A multi-channel instrumentation system is provided wherein signals from selected electrode pairs are sequentially connected to the isolated input of a common signal amplifying path. The electrode pair selecting means is included in a portable head box which may be placed adjacent to the patient to be tested. Included in the head box are facilities for testing the impedance of any selected one of the patient electrodes and providing a visual indication of the magnitude of such impedance. The head box also includes facilities for selecting a group of patient electrodes which are connected together and used as an average or reference potential for one input of the common signal path. Facilities are also provided for calibrating the common signal path by applying a d.c. calibration signal to the input thereof by means isolated from system ground. An improved circuit arrangement is provided for limiting the current which can be drawn from the patient ground electrode to a small value to provide for the safety of the patient in the event of malfunctioning of the electrode selecting means. Facilities are provided in the common signal path for removing the d.c. components of the electrode pair signal voltages, and for selectively varying the gain of the common signal path on an individual channel basis.

Claims

1. In an EEG system having a plurality of patient electrodes each having an identifiable symbol and selectably connectable in pairs to provide the inputs for channels in a multi-channel recorder means for recording traces corresponding to signals developed in said channel, each of said channels having an identifying symbol, amplification means for amplifying analog signals selectively connected to said plurality of electrodes and to said recorder means, selecting means for selecting the gain of said amplification means for each of said channels, said gain being represented by a numerical value, keyboard means including a plurality of channel select keys, digital display means including a group of seven-segment display devices, interconnecting means interconnecting said keyboard means and said digital display means energized by actuation of any one or more of said channel select keys for displaying information on said digital display means, said interconnecting means including means energized by actuation of said channel select keys for displaying on said digital display means said numerical value representing the selected gain numerical value of said amplifier for the channel corresponding to the actuated channel select keys.

2. The EEG system of claim 1 wherein said amplification means includes a differential amplifier having first and second inputs and means for selectively connecting different pairs of said electrodes to said first and second inputs for different channels of said multi-channel recorder means, said interconnecting means also including means energized by actuations of said channel select keys for displaying on said digital display means the symbol identifying the selected channel and the symbol identifying the respective electrodes connected to said first and second amplifier outputs.

3. The EEG system of claim 2 also including means for selecting the time constant of said amplification means for each of said channels, said time constant being represented by a numerical value and said interconnecting means further including means energized by actuation of said channel select keys for displaying on said digital display means the selected time constant numerical value of said amplifier for the selected channel.

4. The EEG system of claim 3 wherein said keyboard means includes averaging means for selecting a group of said patient electrodes to act as an average reference, means for connecting said group as one input to said differential amplifier, said interconnecting means further including means energized by actuation of said channel select keys for displaying on said digital display means an average reference indication when said average reference is connected to one of said inputs.

5. The EEG system of claim 4, wherein said average reference indication provided by said first group of seven-segment display devices is AVG.

6. In an EEG system having a plurality of patient electrodes each having an identifiable symbol and selectably connectable in pairs to provide the inputs for channels in a multi-channel recorder means for recording traces corresponding to signals developed in said channel, amplification means for amplifying analog signals selectively connected to said plurality of electrodes and to said recorder means, selecting means for selecting the time constant of said amplification means for each of said channels, said time constant being represented by a numerical value, keyboard means including a plurality of channel select keys, digital display means including a group of seven-segment display devices, interconnecting means interconnecting said keyboard means and said digital display means energized by actuation of any one or more of said channel select keys for displaying information on said digital display means, said interconnecting means also includes means energized by actuation of said channel select keys for displaying on said digital display means the selected time constant numerical value of said amplifier for the channel number corresponding to said actuated channel select keys.