Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
  • A61B5/25—Bioelectric electrodes therefor
  • A61B5/251—Means for maintaining electrode contact with the body
  • A61B5/257—Means for maintaining electrode contact with the body using adhesive means, e.g. adhesive pads or tapes
  • A61B5/259—Means for maintaining electrode contact with the body using adhesive means, e.g. adhesive pads or tapes using conductive adhesive means, e.g. gels
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
  • A61B2562/02—Details of sensors specially adapted for in-vivo measurements
  • A61B2562/0209—Special features of electrodes classified in A61B5/24, A61B5/25, A61B5/283, A61B5/291, A61B5/296, A61B5/053
  • A61B2562/0215—Silver or silver chloride containing

Definitions

• the present invention relates generally to an apparatus for screening or sensing disease states, injury sites or bodily conditions in a living organism by detecting the DC biopotential of the electromagnetic field present between a reference and a plurality of test points on the living organism to measure the gradient of electrical activity which occurs as a function of biological activity, and more particularly to DC biopotential sensing electrodes for use with such apparatus and an electroconductive medium with a high chloride ion content for use in such electrodes.
• the detection and diagnosis of disease states can be accomplished by using one measuring electrode situated externally on or near the disease site to provide a measurement of the polarity of the signal received from the site relative to that from the reference site. Where multiple measuring electrodes have been used, their outputs have merely been summed and averaged to obtain one average signal from which a polarity determination is made.
• This approach can be subject to major deficiencies which lead to diagnostic inaccuracy, particularly where only surface measurements are taken.
• the polarity of diseased tissue underlying a recording electrode has been found to change over time. This fact results in a potential change which confounds reliable diagnosis when only one external recording electrode is used. Additionally, the polarity of tissue as measured by skin surface recording is dependent not only upon the placement of the recording electrode, but also upon the placement of the reference electrode. Therefore, a measured negative polarity is not necessarily indicative of diseases such as cancer, since polarity at the disease site depends in part on the placement of the reference electrode. As disease states such as cancer progress, they produce local effects which include changes in vascularization, water content, and cell division rate. These effects alter ionic concentrations which can be measured at the skin surface and within the neoplastic tissues.
• Electrode and electrode circuit characteristics and electrode placement b e come important. Factors such as small DC offset potentials in the low millivolt range, which may have little effect on an AC biopotential measurement, such as ECG measurement, can destroy the accuracy of a DC biopotential measurement. For screening applications where many sensing electrodes are used, it is often critical for electrode characteristics to be uniform, for accurate electrode spacing to be maintained and for DC offsets to be substantially eliminated.
• DC biopotential sensing electrodes are packaged in a pre- gelled state wherein an electrolytic paste or gel is packaged as part of the electrode.
• the gel may be located in a central gel reservoir consisting of a molded cup, or it may be contained in a dye-cut hole in a foam which encapsulates a gel saturated open cell compressible foam column.
• the pre-gelled electrodes are sold ready for use with an electrically conductive material such as metal or a metal chloride in contact with the electrolyte gel.
• a pre-gelled electrode system is generally not a battery by itself, but forms a part of a battery-system consisting of two or more electrodes placed on the body.
• a complex battery is formed consisting of many interactive components including the electrode material (frequently silver/silver chloride), the electrode gel, internal body chemistry and external skin conditions, skin preparation, temperature, air condition and chemistry, etc.
• the electrode material frequently silver/silver chloride
• the electrode gel internal body chemistry and external skin conditions
• skin preparation temperature, air condition and chemistry, etc.
• temperature temperature
• artifacts such as DC offsets
• Most pre-gelled electrodes when introduced in the battery system outlined above contribute some unwanted DC voltage (polarization effect) to biopotential measurements. It is important to lower the possibility of such DC artifacts occurring to a degree sufficient to preclude them from having a substantial adverse effect on biopotential measurements.
• ECG electrocardiology
• EEG electroencephalography
• U.S. national standards for single use ECG electrodes allow the DC offset of an electrode pair (i.e., the spurious DC current generated by electrochemical interactions between electrode components) to be as high as 100 millivolts (ANSI/AAMI standard). Since effective use of DC signals for cancer diagnosis requires discrimination at the one millivolt level, standards for ECG electrodes are grossly excessive.
• ECG electrodes are intended for AC measurements which are not significantly affected by DC offset voltages in the electrode to the degree that DC biopotential measurements are adversely affected by such offset voltages.
• a pre-gelled electrode array is to be used effectively for disease detection, such as breast cane - screening, the array will require a relatively large number of spaced electrodes to cover substantially the entire surface of the breast. Not only must each of these electrodes be free from error causing offset potentials before use, but the electrodes must maintain contact with the curved surface of the breast without movement during the screening procedure and must maintain a predetermined array formation with specified electrode spacing. Consistent location and orientation of the electrical channels connected to the respective electrodes must also be maintained to prevent incorrect connection to the electrodes and to maintain positive contact between the electrodes and the electrical channel leads therefor.
• Another object of the present invention is to provide a novel and improved gel or cream for use as an electroconductive medium in a DC biopotential sensing electrode which transmits ions from the skin of a subject to an electrode sensing element wherein the gel or cream includes a chloride ion content which is within the range of chloride ion that is in isotonic or hypertonic fluids.
• a further object of the present invention is to provide a novel and improved DC biopotential sensing electrode having dual conductive paths through the electrical conductive elements of the electrode.
• Yet another object of the present invention is to provide a novel and improved gel or cream for a pre-gelled DC biopotential electrode having a high chloride ion content.
• the electrode structure is formed to be resistant to corrosion caused by ions in the gel or cream.
• Another object of the present invention is to provide a novel and improved DC biopotential sensing electrode which includes a gel or cream for transmitting ions from the skin of a subject to an electrode sensing element wherein the gel or cream includes a chloride content which is within the range of chloride that is an isotonic or hypertonic fluids.
• Another object of the present invention is to provide a novel and improved electrode and cable assembly which terminates at a single connector which may be connected to a connector for a cable system leading to a processor unit.
• the connector includes means to transmit identification signals to the processor unit.
• a further object of the present invention to provide a novel and improved electrode positioning harness for use with a biopotential measuring electrode array and device for disease, injury and bodily condition screening and sensing.
• a still further object of the present invention is to provide a novel and improved electrode positioning harness for use with a biopotential measuring electrode array for breast cancer screening which will effectively and comfortably accommodate various breast sizes based upon anthropometric data.
• Figure 1 is a block diagram of the apparatus for disease, injury and bodily condition screening or sensing with the DC biopotential sensing electrode assembly of the present invention
• Figure 2 is a flow diagram illustrating the operation of the apparatus of Figure 1;
• Figure 3 is a flow diagram illustrating the operation of the apparatus of Figure 1;
• Figure 4 is an exploded view of a DC biopotential sensing electrode for use with the apparatus of Figure 1 ;
• Figure 5 is a cross sectional view of the electrode of Figure 4.
• Figure 6 is a cross sectional view of the terminal for the electrode of Figure 4.
• Figure 7 is a cross sectional view of the sensor for the electrode of Figure 4;
• Figure 8 is a cross sectional view of the packaging unit for the electrode of Figure 4;
• Figure 9 is a plan view of the electrode of Figure 4 and the adhesive release strip therefor;
• Figure 10 is a diagram illustrating the sizing and electrode placement for a breast screening electrode array
• Figure 11 is an exploded perspective view of a lattice electrode array of the present invention.
• Figure 12 is a plan view of a second embodiment of a lattice electrode array of the present invention.
• Figure 13 is an exploded view of an electrode structure and pad of the lattice electrode array of Figure 12;
• Figure 14 is a perspective top view of a third embodiment of an electrode array of the present invention and the packaging therefor.
• Figure 1 discloses a basic block diagram of the measuring apparatus 10 for performing an analysis for indicating the presence, absence or state of a condition at a test site on a human or animal subject.
• the apparatus 10 will be described in connection with methods involving the screening or sensing of breast cancer.
• the apparatus can be similarly employed for providing an indication of disease, injury or other body condition of a living human or animal.
• a human subject 12 may have a cancerous lesion 14 on one breast 16. This cancerous lesion has a core 18 and an outer zone 20 surrounding the core where various differing local effects, such as changes in vascularization, water content and cell division rate occur.
• the electrode array includes a central electrode 24 surrounded by four peripheral electrodes 26, all of which are skin surface electrodes.
• this invention contemplates the use of a variety of different electrode arrays depending upon the intended application for which the device 10 is used. For example, in the diagnosis of clinically symptomatic breast or skin lesions, the electrode array should cover various areas of the lesion as well as relatively normal tissue near the lesion site.
• the array For breast cancer screening (where patients are asymptomatic), the array should give maximum coverage of the entire breast surface. The aim in both of these areas is to measure the gradient of electrical activity which occurs as a function of the underlying biological activity of the organ system.
• the number of electrodes used in the measurement will also be a function of specific application, and breast cancer screening may require the use of as few as twelve or as many as sixty or more electrodes for each breast, while in screening for prostate cancer, as few as two measurement electrodes might be used.
• the core electrode 24 and the peripheral electrodes 26 are mounted upon a flexible backing sheet 28 which permits the electrodes to be positioned against the curved surface of the breast 16 while still maintaining the position of the electrodes in predetermined pattern.
• odier electrode arrays may be employed wherein each individual electrode can be individually positioned, and the relative position between electrodes can be altered.
• the electrode array 22 is used in conjunction with one or more reference skin surface electrodes 30, and all of these electrodes are of a type used for detecting the potential level of the DC electromagnetic field present in a living organism.
• the device 10 is shown as a multi-channel device having electrode leads 34 extending separately from the central electrode 24, the peripheral electrodes 26, and the reference electrode 30 to a low pass filter amplifier 36.
• This filter amplifier operates to remove some undesirable high frequency AC components which appear on the slowly varying DC voltage signal outputs provided by each of the electrodes as a result of the electromagnetic field measurement.
• the output from the filter amplifier 36 is provided to an analog-to- digital converter 40 which converts each analog signal received thereby to a digital signal to be provided to the input of a central processing unit (CPU) 42.
• CPU central processing unit
• the central processing unit may respond directly to analog input signals or to digital or other coded signals produced directly by the electrode array 22, and in such cases, the analog to digital converter 40 and possibly even the filter 36 would be eliminated and the output from the electrode array would input directly to the CPU.
• the central processing unit is a component of a central control unit indicated generally at 44 which includes RAM and ROM memories 46 and 48.
• Digital input data from the analog-to-digital converter 40 is stored in memory and is processed by the CPU 42 in accordance with a stored program to perform various pattern recognition methods to be described.
• the digital signals may be subjected to digital filtering by the CPU before processing.
• the information derived by the CPU as a result of this processing is then fed to a suitable indicator device 50 which may constitute a printer, a CRT display device, a storage tape or disc, or a combination of such conventional indicators.
• One structure for accomplishing this incorporates the leads 34 into a cable 52 which is used to removably connect the electrode array 22 and the reference electrode 30 to the low pass filter amplifier 36.
• This cable can be a multichannel cable or a single channel cable, depending upon whether or not electrode multiplexing is employed.
• a conventional connector, not shown, is provided to connect one end of the cable to the low pass filter 36, or with a single channel filter, the connector may be plugged to a sequencing switch.
• Each cable lead 34 is connected to the output terminal for one of the electrodes in the electrode array 22.
• a separate connection is made between a conductor 54 within the cable and a conductor 56 leading directly to the CPU 42.
• the conductor 54 leads to an address identification chip 58 of known type which responds to an address interrogation signal provided over the conductor 54 to the address chip.
• the proper address interrogation signal is stored in the memory for the central control unit 44 and is sent over the conductor 56 by the CPU 42 when the apparatus 10 is initially activated. If this interrogation signal corresponds to a signal to which the address chip 58 responds, then a response from the address chip is passed by the conductors 54 and 56 back to the CPU 42 and the CPU initiates a measurement operation in response to a control program stored in the memory for the central control unit. Alternatively, if the wrong address chip, no address chip or no electrode array connection is present, no response is received from the address interrogation signal and the CPU 42 does not proceed with the stored control program.
• the central control unit 44 can be made responsive to other parameters in the electrode array 22 during an initial test period to assure that an acceptable electrode array is in place before a measurement program is begun.
• the presence of an offset potential in the electrode array is detrimental to the accuracy of DC biopotential measurements, and the magnitude of this offset potential can be measured during the test period of the apparatus 10. If the measured offset potential is less than a predetermined level, then the CPU may continue with a measurement operation in response to the stored control program, but if the offset potential exceeds the predetermined level, the measurement operation is not initiated by the CPU.
• the electrodes which are used as the electrodes 24, 26 and 30 should be manufactured to specific electrical tolerances if they are to be effectively used to provide accurate DC biopotential measurements.
• each electrode The electrical characteristics of each electrode are determined by elements of construction such as electrode size, the type of gel or cream used, and the types of metals and other materials used in constructing the electrode. These electrical characteristics may be measured in the same manner as the offset potential, and the measurement operation can be cancelled by the CPU if the proper electrode characteristics are not present.
• the CPU 42 can be programmed to run identification tests on a variety of electrode combinations, since diverse DC biopotential measurement applications require the use of different numbers of electrodes.
• the electrical characteristics of as few as two electrodes, a reference and a measurement electrode, plus a plurality of acceptable electrode array combinations would be stored in the memory of the control unit 44.
• each individual electrode with an address identification chip 58 having a lead or terminal 56 which could plug into a test block connected to the CPU . This would permit each individual electrode to be used during a measurement operation to be identified by the CPU 42 during an initialization operation.
• the unit 58 has been identified as an address identification chip, this unit constitutes any structure which responds to an interrogation signal in a definable manner.
• the unit 58 could be formed by a particular material having a specific response characteristic to an interrogation signal, and this material could actually be one which is used in the construction of the individual electrodes.
• the operation of the apparatus 10 will be clearly understood from a brief consideration of the broad method steps of the invention which the device is intended to perform.
• the electrode array 22 is positioned with electrodes 24 and 26 located over various diverse areas of a test site, and the reference electrode 30 is then brought into contact with the skin of the subject in spaced relationship to the electrode arrays.
• This reference electrode might, for example, be brought into contact with a hand of the subject.
• the electromagnetic field between the reference electrode and each of the electrodes 24 and 26 is measured, converted to a digital signal and stored for processing by the control unit 44.
• the program control for the central processor unit 42 causes a plurality of these measurements to be taken over a period of time, and the measurements on all channels are taken repetitively during a predetermined measurement time or test perior Sequential measurements between the reference electrode and one of th electrodes in the array 22 are taken until each channel is sampled, and then the sequential measurement is repeated jughout the duration of the predetermined test period.
• a plurality of measurements have been taken over a period of time and often from a plurality of electrodes, but then these plural measurements are merely averaged to provide a single average output indication.
• the measurement indications on each individual channel are not averaged with those from other channels, but are instead kept separate and averaged by channel within the CPU 42 at the end of the test period.
• the CPU will obtain five average signals indicative of the average electromagnetic field for the test period between the reference electrode 30 and each of the electrodes 24 and 26 in the electrode array 22.
• more reference electrod * can ' ; used, although only one reference electrode has been shown for purposes of illustration.
• MVD maximum voltage differential
• LER abnormally low individual electrode reading
• the general overall operation of the central processing unit 42 will best be understood with reference to the flow diagrams of Figures 2 and 3.
• the operation of the unit 10 is started by a suitable start switch as indicated at 78 to energize the central processing unit 42, and this triggers an initiate state 80.
• the various components of the device 10 are automatically brought to an operating mode, with for example, the indicator 50 being activated while various control registers for the central processing unit are reset to a desired state.
• a test period is initiated at 82 wherein the various components of the system are tested for proper operability.
• the electrode array 22 may also be tested to make certain that electrodes are being used which accurately measure DC biopotentials. This would involve interrogation of the address chip 58 and possibly the testing for other electrode characteristics.
• the address chip may be included in a disposable cable connector to be subsequently described, and it can be important that this cable connector be adapted for only one use. Therefore, the central processing unit may have the ability to disable the address chip once a proper address is received so that the cable connector cannot be reused with improper electrodes to provide a new address signal. This can be accomplished in a number of ways.
• the address chip 58 may be an EE PROM containing the address combined with a signal activated erase circuit for the EE PROM. Once the central processor receives the proper address, it would send a command signal to the erase circuit to erase the EE PROM.
• Another simple deactivation circuit would include a small fuse unit in the line 54 portion of a cable connector. Once the central processor receives the proper address, it would send a command signal over the line 56 to burn out or blow the fuse circuit and disconnect the address chip 58. If all system components test out properly during the system test period, then timing of the analog to digital converter in accordance with the AC line frequency begins at 84 and the timing of any switching systems or multiplexors begins at 86. It is now possible to monitor the biopotential signals from a test area during a monitoring period begun at 88. During this monitoring period, conditions in the test area contacted by the electrode array 22 are stabilized so that subsequent reliable measurements of DC biopotentials can be obtained.
• a predetermined monitoring period is initiated, and the signals on all channels are monitored and averaged. Then, at the end of the initial monitoring period, the individual sample voltages are compared to the average of all voltages sampled during the measurement period to obtain a differential, and if the differential is greater than a predetermined value x, then sufficient signal stabilization has not occurred during the monitoring period and a new monitoring period is initiated. Conversely, if the differential signals are less than the predetermined value x, then the monitoring period is terminated and a test period is initiated.
• the digitized signals received from the various sequenced channels are monitored at 92 to determine whether or not each biopotential represented by the signals is within the range of from -30 to +100 millivolts. Digitized signals indicative of DC signals outside this range are discarded at 94 and the remaining signals are used to provide an average or normalized value for each channel at 96. The averaged value for each channel is obtained by summing the values obtained for that channel during the test period and dividing the sum by the number of measurements taken. Then, at 98, the central processor unit determines whether the test period has expired and the desired number of measurements have been taken, and if not, the collection of measurement samples or values continues.
• a final average value for each channel derived from the measurements taken during the span of the test period is available, and from these average values, the highest and lowest average value obtain during the test period is sampled at 100.
• the lowest average channel value is subtracted from the highest average channel value at 102 to obtain a maximum voltage differential value.
• This maximum voltage differential value is then processed at 104 to indicate the presence or absence of a disease, injury, or other bodily condition, and during processing, can be compared with previously obtained differential values to determine the efficacy of treatment or the progress of a disease, injury or other bodily condition.
• the differential value may also be used to indicate the occurrence of a number of normal bodily functions such as ovulation, and normal or abnormal labor conditions.
• the digital signals stored by the central control unit and the average signals for each channel can be processed at 104 in a r ⁇ -.iiner to be described.
• a major design consideration for an effective DC biopotential measurement device 10 is to make the input impedance many times higher than that produced by the skin and sensor interfaces. Failure to do so results in decreased signal amplitude and, most important, loss of low frequency (e.g., DC) information.
• Sampling of DC potentials e.g., number of samples and over what time period
• microprocessor technology is utilized to its fullest. In digital systems, selection of the optimal sampling regimen is a balance between two factors:
• the DC biopotential sensing electrodes 24, 26 and 30 are responsible for transmitting ionic current from the skin of a subject through an electroconductive medium contained in the electrode, such as a cream or gel, which forms a conductive bridge between the skin surface and an electrode sensor element.
• the sensor element transduces ionic conduction to metallic conduction, and the resultant signal is then relayed by a cable system from the output of the sensing electrode.
• Ions from the skin surface are driven into the electroconductive medium by electromotive force, or the physical propensity of ionic concentrations to equilibrate.
• a charge gradient between ions in the gel or cream and the discharge of ic ⁇ from the sensor is formed. This has been referred to as the electrical double layer and can be visualized as two parallel sheets of charge with opposite sign. Maintenance of a stable double layer is an integral part of keeping noise to a minimum in DC measurement systems.
• Johnson noise Another source of potential noise is resistance in a circuit, oft "n referred to as Johnson noise, named after its discoverer. Resistance in any circuit creates spurious wide band voltages which result from the random motion of charge carriers in the conductor. Johnson noise can be ameliorated by using low resistance sensing electrodes and limiting the bandwidth of the measuring apparatus. Failure to control Johnson noise limits the level of minimum signal which is detectable.
• T e optimal single-use sensing electrode for biologic DC measurement requires both low DC offset and low resistance.
• Such a design circumvents the problem of a dissimilar metals reaction which can be exacerbated by use of low viscosity, high electrolyte ontent gels and creams.
• sensors of this type can be made with DC offsets less than 0.5 mV and with very low impedance characteristics.
• a DC biopotential sensing electrode which incorporates an electroconductive medium in the form of a gel or cream which has a chloride ion content within or higher than the range of chloride ion present in isotonic or hypertonic fluids.
• This chloride ion content includes a substantial amount of chloride ions derived from sodium chloride as well as an equal or greater amount of chloride ion derived from other ionic chloride salts, such as potassium chloride as well as calcium chloride, and this total chloride ion content is combined in a cream or gel formed from 8 % to 35 % solids mixed with water.
• the water must be free of impurities, such as heavy metals, which interfere with the DC biopotential signal sensed by the sensing electrode, and preferably pharmaceutical grade water is used in the formation of the gel or cream.
• the gel or cream is formed to have a pH within a range of 4 to 6.5, and a total chloride ion content within a range of 6-15 grams chloride ion per hundred grams of electroconductive medium.
• the total chloride ion content is preferably no more than 12g chloride ion per lOOg of electroconductive medium; the minimum amount is preferably 7 or 8g chloride ion per lOOg of electroconductive medium, depending on the physical form of the medium.
• the preferred lower limit is 7g chloride ion per lOOg of cream and 8g chloride ion per lOOg of gel.
• the conductivity of the gel or cream is within a range of from 10,500 to 220,000 micromhos; the micromho being the inverse of impedance indicated by the ohm.
• the conductivity of electroconductive cream is within a range of from 10,500 to 50,000 micromhos and the conductivity of electroconductive gel is within a range of from 182,000 to 220,000 micromhos.
• a stainless steel kettle such as Groen model No. KRE/1-40 with heating capability and appropriate capacity and rating is selected.
• the kettle must be equipped with a built-in agitator or be capable of having an add-on agitator system added to it.
• a typical synthesis of a » 100kg batch of electroconductive cream is detailed below with the reagents listed above scaled accordingly.
• the weighed USP purified water is added to the tank mixer and stirred.
• the kettle is heated until a temperature of 60 + /- 2°C is achieved.
• Sodium chloride is then slowly added over a 5 minute period to the kettle and the contents of the kettle are mixed thoroughly for 15 minutes after the addition is completed or until the sodium chloride is completely dissolved.
• Heating of the kettle is continued with the temperature maintained at 60 +/- 2°C.
• Potassium chloride is slowly added next over a 5 minute period and mixed thoroughly for 15 minutes after addition is completed or until the potassium chloride is completely dissolved. Heating is maintained at 60 +/- 2°C.
• Calcium chloride dihydrate is then slowly added over a 5 minute period and the contents of the kettle mixed thoroughly for 15 minutes after the addition is completed or until the calcium chloride dihydrate is completely dissolved. Care is again taken to maintain the temperature of the mixture at 60 +/- 2°C.
• the parabens (methylparabens, propylparabens and butylparabens) are then slowly added to the kettle over a 5 minute period and mixed thoroughly with the contents of the kettle for 5 minutes.
• the temperature of the mixture is maintained at 60 +/- 2°C.
• Propylene glycol is then next slowly added over a 5 minute period and the contents of the kettle are mixed thoroughly for 5 minutes maintaining a temperature of 60 +/- 2°C.
• Glycerol monostearate is slowly added over a 5 minute period and mixed thoroughly with the contents of the kettle for 5 minutes with the temperature maintained at 60 +/- 2°C.
• Polyethylene glycerol stearate is melted and slowly added to the contents of the kettle and the contents mixed thoroughly for 5 minutes or until all of the stearate has dispersed. The temperature is held at 60 +/- 2°C. Stearyl/cetyl alcohol blend is then melted and added in a thin stream to the contents of the kettle over a 5 minute period and mixed thoroughly for 5 minutes until all of the alcohol blend has melted and dispersed. The temperature is held at 60 +/- 2°C. Finally, the mineral oil is added in a thin stream over a 5 minute period and mixed thoroughly with the contents of the kettle with the temperature held at 60 +/- 2°C.
• the contents of the kettle are stirred thoroughly and slowly allowed to cool to 48 +/- 2°C. Stirring is continued and the contents of the kettle cooled to 25 +/- 5°C. The complete cream is then removed from the kettle and packaged in tightly sealed containers.
• the following tabulated nominal molarities and weights of component are preferred.
• the components may range from 2.33 - 2.92g Na + , 0.81-0.93g Ca +2 , 1.58-1.80g K + and 7.6-9.06g Cl per lOOg of cream and still yield clinically acceptable results for this particular formulation.
• the final cream exhibits a conductivity of 11,500-39,400 micromhos and a viscosity at 25°C of 14,000-16,000 cps.
• USP [APET] A stainless steel kettle with heating capability and appropriate capacity and rating is selected.
• the kettle must be equipped with a built-in agitator or be capable of having an add-on agitator system added to it.
• a typical synthesis of a * 100kg batch of electroconductive gel is detailed below with the reagents listed above scaled accordingly using either a g/L or g/lOOg formulation.
• the weighed USP purified water is added to the tank mixer and stirred.
• the kettle is heated until a temperature of 34 +/- 8°C is achieved.
• Potassium chloride is then slowly added over a 5 minute period to the kettle and the contents of the kettle are mixed thoroughly for 15 minutes after the addition is completed. Heating of the kettle is continued with the temperature maintained at 38 +/- 4°C.
• Sodium chloride is slowly added next over a 5 minute period and mixed thoroughly for 15 minutes after addition is completed.
• Calcium chloride dihydrate is then slowly added over a 5 minute period and the contents of the kettle mixed thoroughly for 30 minutes after the addition is completed. The temperature is then checked and maintained at 38 +/- 4°C.
• the kettle is then uncovered and Natrosol is slowly added over a 10 minute period using a fine-mesh stainless steel sifter in constant motion so as to not cause clumping of the thickener.
• the mixture is then stirred for 30 minutes.
• the temperature of the kettle is raised to 54 +/- 5°C and then heating is stopped.
• the kettle is then covered and the contents mixed thoroughly for 3 hours.
• the gel is allowed to cool. After 24 hours, the pH of the mixture is checked while stirring and is adjusted to a target pH of 6.5 using 1 % NaOH, if necessary.
• the completed gel is then removed from the kettle and packaged in tightly sealed containers.
• the following tabulated nominal molarities and weights of component are preferred.
• the components may range from 1.44-1.69g Na + , 2.10-2.30g Ca +2 , 5.9- 6.53g K + and 10.70-11.36g Cl per lOOg of gel and still yield clinically acceptable results for this particular formulation.
• the final gel exhibits a conductivity of 198,706-216,826 micromhos and a viscosity at 25 °C of 51,200-58,400 cps.
• the chloride ion content in the electroconductive medium of the present invention is much higher than that in conventional pregelled AC biopotential sensing electrodes, and this high chloride ion content will rapidly cause corrosion to occur in a conventional electrode rendering the electrode useless after a minimal shelf life period.
• the novel DC biopotential sensing electrode of the present invention indicated generally at 106 in Figures 4 and 5, has been uniquely designed to have a long shelf life in spite qf the high chloride ion content of the electroconductive medium used in the electrode and to exhibit both a low DC offset and a low AC impedance.
• the DC biopotential sensing electrode 106 of the present invention includes a sensor element 108 having a sensor body 110.
• the sensor body is formed from a round sensor disc 112 and a mounting pin 114 which projects outwardly from the sensor disc.
• a first, lower surface 116 of the sensor disc provides an interface surface for contact with the electroconductive medium contained in the electrode, while a second opposed surface 118 from which the mounting pin projects provides a sealing surface for sealing the electroconductive medium within the electrode.
• the diameter of the sensor disc can affect the DC biopotentials sensed, and preferably the diameter is within a range of .39- .43 inches.
• the biopotential sensing electrode 106 includes only a single metal component which >s highly resistant to corrosion when subjected to the high chloride ion co ⁇ .nt of the electroconductive medium for the electrode, for the inclusion of more than one metal would result in a bimetallic action that would enhance corrosion caused by chloride ion. Consequently, the body 110 of the sensor element 108 is formed of a nonmetallic material 120, such as plastic, glass, or a combination of both, and is then coated uniformly with a very thin coating 122 of an electrically conductive metal.
• the metal coating 122 is preferably only 1 mil. in thickness and should have a thickness within a range of .5 to 1.5 mil.
• the metal coating 122 must evenly coat all surfaces of the nonmetallic material 120 and provide an unbroken layer of substantially uniform thickness.
• This coating may consist of an electrically or chemically deposited silver coating which is then electrically or chemically treated to form an outer film 124 of silver chloride and an inner layer 126 of silver.
• the sensing electrode 106 is provided with dual conductive paths so that a second electrical path is formed through the nonmetallic material 120.
• an electrically conductive nonmetallic material such as an electrically conductive plastic, glass, or glass-plastic combination.
• a plastic such as ABS plastic, a glass, or a glass-plastic combination, impregnated with carbon within a total content range of from 20-40% by volume or weight has been found to be effective, and a preferred carbon content is 30% carbon by volume or weight.
• the sensor element 108 is designed to engage an electrode terminal 128 and to transfer a DC signal thereto.
• This electrode terminal includes a terminal body 130 having a button connector section 132 projecting outwardly from an annular skirt 134.
• the button section is round in cross section, and the uppermost portion 136 thereof has a diameter of .151 inches or greater and is of a greater cross sectional diameter than the remainder of the button section.
• the wall of the upper portion of the button section is of a greater thickness than the wall of the remainder of the button section.
• the body 130 of the electrode terminal includes a central chamber
• the edge of the opening into this central chamber is radiused at 140 to prevent surface chipping of the mounting pin as it enters and is forced into the central chamber. Additionally, the edge at the chamber innermost end is radiused at 141 to minimize cracking or chipping of the mounting pin 114 during assembly.
• the lead and trailing edges of the mounting pin are also radiused as indicated at 123 and 125, respectively.
• the radiused edges 123 and 141 are formed to conform and are thus radiused the same, while the edges 125 and 140 are also radiused equally but at a greater radius to form a larger arc than is formed at the edges 123 and 141. This provides a wider opening to the chamber 138.
• the outer diameter of the mounting pin 114 conform to the inner diameter of the central chamber 138 within a close tolerance.
• these diameters should be formed to a tolerance of + or minus .001 inches.
• the body 130 of the electrode 128 is formed of a nonmetallic material 142, such as plastic, glass or a combination of both coated uniformly with a thin coating 144 of electrically conductive metal.
• the metal coating on the nonmetallic material 142 must be formed of the same metal used to coat the nonmetallic material 120 of the sensor body 110 to preclude bimetallic support of corrosion within the biopotential sensing electrode 106.
• the thickness of metal coating 144 is preferably 1 mil. but is within a range of from .5 to 1.5 mil. When silver is used for the sensor element 108, silver will also be used to coat the electrode terminal 128.
• a second electrical path is formed via the nonmetallic material 142 by using conductive plastic, glass or combination of both for this material.
• This plastic, glass or glass-plastic combination may be impregnated with carbon and has a carbon content which is preferably 30% but within a range of from 20 to 40% by volume or weight.
• the outer edges 111 and 131, respectively, thereof are not substantially crowned but are radiused so that the metal layer is deposited evenly around each edge. Unradiused edges which provide a sharp edge or corner do not receive a uniform metal layer during electrical or chemical deposition and the metal layer on sharp edges is easily cracked or chipped. By providing relatively thick, radiused edges, the metal flows evenly around the edge during deposition and a uniform metal layer is achieved.
• a sheet of flexible, nonmetallic, liquid impervious barrier material 146 is positioned between the sensor element 108 and the electrode terminal 128 to form a barrier against the passage of liquid.
• This barrier material has a central opening 148 which permits the mounting pin 114 to pass through the barrier sheet and into the chamber 138 of the electrode terminal.
• the barrier sheet is adhered and sealed to the second surface 118 of the sensor disc 112 and with the sensor disc forms a primary seal to preclude passage of the electroconductive medium to the electrode terminal 128.
• the barrier sheet is preferably formed of a foil material such as polyvinyl chloride.
• a circular ring of flexible material 150 is secured and sealed to the barrier sheet 146 and is thicker than the barrier sheet so that a central opening 152 extending therebetween forms a well 154 which contains the electroconductive medium for the DC biopotential sensing electrode 106.
• This electroconductive medium is in the form of a gel or cream with a high chloride ion content as previously described.
• the well is positioned relative to the barrier sheet so that the sensor disc 112 is centrally positioned in the well at the end thereof sealed by the barrier sheet.
• the diameter of the well defines the cross sectional area of a patient's skin which will be contacted by the electroconductive medium, and it should be within a range which is equal to the diameter of the sensor disc to one and one half times the diameter of the sensor disc.
• the outside diameter of the circular ring of flexible material 150 is at least three times the diameter of the sensor disc 112.
• the distance between the edges of the sensor discs of the two electrodes will be at least twice the diameter of the sensor discs, which is a minimum spacing between discs. If the biopotential sensing electrodes are to provide signals from which a differential value is derived, the sensor discs should be sufficiently spaced so that two adjacent electrodes are not sensing a DC biopotential from the same area of tissue.
• the circular ring of flexible material 150 is preferably formed from a flexible foam, such as a cross-linked polyethylene foam, and includes a skin contact surface 156 which is coated with an adhesive acceptable for skin contact. It is this adhesive coated surface which adheres the biopotential sensing electrode 106 to the skin of a subject.
• a disc 160 of reticulated open cell plastic foam is mounted in the well and is impregnated with the electroconductive medium.
• This disc 160 extends outwardly from the well beyond the skin contact surface 156, and permits the spread of the electroconductive medium onto the skin of a subject when the biopotential sensing electrode 106 is pressed in place.
• the open cell plastic foam disc is preferably formed of open cell polyurethene or open cell polyester foam with a cell count which is determined to some extent by the viscosity of the electroconductive medium. Generally the cell count for the plastic foam disc is within a range of from 35-45 cells per square inch. In use, the disc 160 may be secured to the sheet of barrier material
• 146 or may be cut to a diameter slightly larger than the diameter of the well 154 so that it is retained in place within the well by tension.
• each electrode 106 is mounted upon a release liner 162 having an upper surface 164 which is an adhesive release surface.
• the skin contact surface 156 of the electrode 106 is adhered to this adhesive release surface by the adhesive acceptable for skin contact which coats this skin contact surface.
• the circular ring of flexible material 150 may be provided with a tab section 166, and the skin contact surface of this tab section is not coated with adhesive.
• the release liner 162 is formed with a concave depression 168 extending outwardly from the release surface 164 thereof, and this concave depression forms a cavity 170 which opens at the adhesive release surface of the release liner.
• the diameter of this opening is substantially the same as the diameter of the well 154, and the release liner is positioned so that the well and the opening to the cavity 170 are substantially in alignment.
• the cavity 170 contains both the disc 160 of reticulated open cell plastic foam as well as the electroconductive medium which impregnates this disc.
• the release liner is formed of plastic or of similar fluid and air impervious material, and therefore, seals the electroconductive medium within the well 154 and the cavity 170.
• the release liner allows the reticulated foam to retain 95% or more of the electroconductive medium and provides a barrier which prevents dehydration of the electroconductive medium while allowing easy removal of the sensor from the release liner.
• the release liner is formed of a cle ⁇ * r or transparent material, at least in the area of the concave depression 168, so that the electroconductive material in the cavity 170 and the well 154 may be observed. If visual observation indicates that there is not a sufficient amount of electroconductive material in the cavity 170 and the well 154, the electrode 106 should not r id.
• the release liner 162 is preferably formed in strips with a plurality ⁇ electrodes 106 mounted upon each strip.
• the release liner 162 is preferably formed in strips with a plurality ⁇ electrodes 106 mounted upon each strip.
• two strips of electrodes are placed back-to-back with the concave depressions 168 thereof in contact and with the electrode terminals 128 facing outwardly. It is important that the electrodes be packaged so that the electrode terminals for electrodes in the package are prevented from contacting the electrode terminal of another electrode.
• the two strips of electrodes are then encased and sealed within a liquid, vapor and gas impervious outer package 172 which is preferably formed of metal foil.
• the combination of the metal foil outer package and the sealing action provided by the release liner effectively prevents evaporation of the liquid in the electroconductive medium 158.
• electrode supports for breast screening can be formed to one of the five indicated sizes with electrode placement as illustrated by the chart of Figure 10.
• a properly positioned screening array of sensor electrodes would allow mapping of potentials of points in between the sensors by using vector interpolation.
• Color coding or grey scale
• corresponding to various levels of potential would provide visual imaging of the surface potential maps of both breasts.
• Vector interpolation involves summing the point source measurements (that is, the potential measurements actually measured from the skin surface) for each unmeasured point on the breast as a function of the distance each point source measurement is from the interpolated area.
• lattice type electrode arrays and wrap around electrode arrays have been developed to form at least a portion of the electrode array 22 of Figure 1.
• a simple lattice array 176 is illustrated which operates effectively as an aid in assuring proper electrode placement on a breast to be screened.
• the array is designed to be placed on the breast with the nipple 178 as the center registration point for the array, and the array is sized to one of the five sizes dependent upon measurements to the nipple as previously described.
• the basic lattice support 180 for the array is formed from thin, flexible, lightweight electrical insulating material, such as 10 MIL clear polyester film, which has been cut to the desired shape.
• the electrical circuitry 182 leading to each electrode for the array 176 is printed on the lattice support 180 with conductive ink or other printed circuit material, and the individual circuits extend in spaced relationship to one or more attachment tabs 184 formed from the polyester film. These individual circuits are connected to the apparatus 10 by a ribbon cable connector 186 which snaps onto the attachment tab 184 to connect each individual electrode printed circuit to a ribbon cable 188 which includes a separate lead for each electrode circuit.
• the lattice support has a conductive electrode mounting grommet 190 at the end of a radiating arm 192 of the lattice support, and a plurality of the radiating arms project outwardly from a central support ring 194.
• the electrode terminal 128 of an electrode 106 snaps into each of the electrically conductive mounting grommets 190, and each grommet is connected to a separate electrical circuit 182.
• the lattice array 176 with the electrodes 106 in place can be positioned on a breast to be screened without sliding contact and the radiating arms 192 are easily curved to conform to the curved surface of the breast.
• a lattice type electrode array 196 carrying many more electrodes than those shown for the array 176 of Figure 11 can be formed using a thin mylar or polyester film as a flexible support for the electrodes.
• the electrodes are formed directly on circular pads 198 formed on the various radiating arms of the film.
• each of the electrodes formed on the lattice array 196 is illustrated.
• the conductive path 200 is formed, and this conductive path includes a terminal contact 206 which is positioned over an aperture 208 in the pad 198.
• a layer of liquid impervious barrier material 210 is adhered to the pad, and this layer of barrier material includes a central aperture 212 to receive the mounting pin 114 of the sensor element 108.
• This mounting pin extends through the aperture 212 and the aperture 208 and is an electrical contact with the terminal contact 206.
• the sensor disc 112 is adhesively sealed to the barrier material 210, and the barrier material is also sealed to a circular ring of flexible material 150 as previously described.
• the well 154 of the circular ring of flexible material 150 includes the disc 160 of reticulated open cell plastic foam, and this disc is impregnated with the electroconductive medium for the electrode.
• the well 154 is closed by a release liner 162 having the cavity 170 to retain the electroconductive medium and the reticulated foam 160.
• the release liner may be formed as a large single sheet which extends beneath the complete lattice array 196 and which includes a depression 168 and cavity 170 beneath each electrode in the lattice array. In use, the thin film of the lattice array may be easily curved to conform to the curved surface of a breast or other portion of a subject while maintaining relative positioning between the electrodes of the array.
• an electrode assembly formed in accordance with the present invention may be packaged as an integral disposable unit as illustrated in Figure 14.
• the prepackaged disposable electrode array indicated generally at 214 includes a lattice electrode assembly 216 including five electrodes mounted upon a lattice film support 218.
• This lattice film support and the electrodes mounted thereon are similar to that shown in Figure 11, with the exception that the lattice support does not include the conductive ink circuits shown in Figure 11. Instead, the terminals 128 for the electrodes are engaged by snap terminals 220, each of which is connected to a separate conductor 222.
• the conductors 222 lead to an electrical connector 224 which may be plugged into the circuit to the low pass filter amplifier 36 of Figure 1.
• the connector 224 also includes the address chip 58 and the conductor 54 to provide a connection to the conductor 56. Since the terminal snaps 220 could be removed and connected to other sensing electrodes not suited for use with the device 10 of Fig in £ 1, the address chip 8 is preferably combined with circuitry of the tyj . previously described so that the address circuitry in the connector 224 is deactivated by the central processor 42 once the address circuitry has been interrogated and provided a proper address. In addition to the lattice electrode array 216, separate individual electrodes 226 of the type shown in Figures 4 and 5 are also connected to the connector 224 by separate cables 222.
• the electrode lattice array 216 and the individual electrodes 226 as well as the cables 222 and the connector 224 are packaged in a disposable packaging unit 228 which includes a layer of shock absorbing material 230, such as plastic foam or a shock absorbing paper or cardboard layer.
• This shock absorbing material 230 is provided with cut away depressions 232 and 234 to receive the lattice array 216 and the electrodes 226, respectively, as well as a cut away channel 236 for the cables 222 leading to a cut away section 238 for the connector 224.
• the bottom wall of the cut away sections 232 and 234 is formed by a layer of adhesive release material 240 formed in the same manner as the release material 162 of Figures 8 and 9.
• the layer of release material 240 includes the cavities 170 positioned beneath the electrodes in the lattice array 216 as well as beneath each of the electrodes 226.
• the lattice array 216 and separate cables 222 may be replaced by either of the lattice arrays 176 or 196 connected by the cable connectors 186 and ribbon cables 188 to the electrical connector 224.
• the DC biopotential sensing electrodes and electrode assemblies of the present invention may be effectively employed with an apparatus for screening or sensing disease states, injury sites or bodily conditions in a living organism by detecting the DC biopotential of the electromagnetic field present between a reference and a plurality of test points on the living organism.
• These electrodes and electrode assemblies provide an accurate measurement of the gradient of an electrical activity which occurs as a function of biological activi and yet are designed to resist corrosion and provide an extended shelf life.

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• 1995
  • 1995-10-05 IL IL11552495A patent/IL115524A/en not_active IP Right Cessation
  • 1995-10-16 BR BR9509370A patent/BR9509370A/pt not_active IP Right Cessation
  • 1995-10-16 AU AU38244/95A patent/AU3824495A/en not_active Abandoned
  • 1995-10-16 MX MX9702807A patent/MX9702807A/es unknown
  • 1995-10-16 WO PCT/US1995/012525 patent/WO1996011631A1/en not_active Application Discontinuation
  • 1995-10-16 EP EP95936217A patent/EP0786958A4/en not_active Withdrawn
  • 1995-10-16 JP JP8513253A patent/JPH10508227A/ja active Pending
  • 1995-10-16 CA CA002202749A patent/CA2202749C/en not_active Expired - Fee Related

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