WO2013135931A1

WO2013135931A1 - Device for measuring bioelectric signals on the surface of the body, based on adjustable ring sensors

Info

Publication number: WO2013135931A1
Application number: PCT/ES2013/070156
Authority: WO
Inventors: Gema PRATS BOLUDA; Francisco Javier GARCÍA CASADO; Yiyao YE LIN; José Luis MARTÍNEZ DE JUAN; Eduardo GARCÍA BREIJO; Javier IBAÑEZ CIVERA
Original assignee: Universitat Politècnica De València
Priority date: 2012-03-13
Filing date: 2013-03-12
Publication date: 2013-09-19
Also published as: ES2425692B2; ES2425692A1

Abstract

The sensor (1) comprises an insulating support (2), an adhesive (8) for attaching the support to the patient and a disk-shaped conductor (3) and at least one ring conductor (4) concentric with the disk-shaped conductor which are disposed on the support (2) in order to capture bioelectric signals. The conductors (3 and 4) are connected to a circuit (5) for processing the captured signals. The device is characterised in that the support (2) is flexible and the conductors (3 and 4) are printed thereon with conductive paste or ink, said support adapting to the surface to which it is attached. The sensor is modular and interchangeable. The circuit (5) is configured to provide different weights to the voltages of the conductors (3 and 4), generating multiple outputs, corresponding to different sensitivity-based spatial distributions, configured according to requirements for the capture of the bioelectric potentials to be measured. In addition, an array (9) of sensors (1) is provided to obtain different potential maps for each of the sensors (1).

Description

BIOELECTRIC SIGNAL MEASUREMENT DEVICE ON BODY SURFACE BASED ON ADJUSTABLE ANNULAR SENSORS

OBJECT OF THE INVENTION

The present invention, as expressed in the statement of this specification, consists of a body surface measuring device of bioelectric signals of the type comprising a support on which includes a disk-shaped conductor and at least an annular conductor concentric to the previous one, to capture the voltages corresponding to the bioelectric signals in the area where the support is fixed. The object of the invention is to provide an apparatus in which the measuring sensor is flexible obtaining greater comfort for the user, and all this in such a way that the sensor has an interchangeable modular configuration in the apparatus, in order to obtain greater hygiene.

Another of the important objectives of the invention is to provide the apparatus with a plurality of concentric annular conductors to provide a plurality of voltage outputs linear combination of the conductor voltages, the weights of which can be configured according to the different spatial distributions of sensitivity in relation to what is required in capturing the bioelectric potentials to be measured. It is also the object of the invention to provide an apparatus in which the sensor comprises an array of sensors arranged on a single support to achieve a map of bioelectric potentials.

In general, the invention is applicable in clinical settings such as hospitals, health centers, research centers or rehabilitation centers, it can also be applicable to the extent of physical activity, such as in athletes. More specifically the invention is It applies to perform the registration of bioelectric potentials such as the registration of the electrocardiographic signal (ECG), widely used in the diagnosis of cardiac pathologies, or in stress tests. Another outstanding example of application is the non-invasive recording of the uterine bioelectric signal during pregnancy and childbirth (EHG) that helps determine in advance how close the time of delivery is, and if it will be premature. It can also be applied in the case of the monitoring of the intestinal bioelectric activity, known as electroenterogram (EEnG) to determine alterations in the intestinal pacemaker activity, as is the case of intestinal ischemia as well as of pathologies that have associated dysfunctions in intestinal contractile activity such as mechanical obstruction, hypercontractivity and semi-optic or neuropathic disorders. In addition, the invention can be applied to the registration of the electromyogram (EMG), the electrogastrographic signal, the diaphragmatic signal, the encephalographic signal register, the oculogram or the retinogram. In general, the invention is applicable to the recording of any bioelectric signal capable of being captured on the body surface. BACKGROUND OF THE INVENTION

In the state of the art, the scientific article "Concentric ring electrode systems for non-invasive detection of single motor unit activity" can be cited, which describes the use of electrodes composed of a central disk and at least one ring around said central disk, both elements acting as electrical conductors, to register bioelectric potentials. It also describes that the ideal for increasing the spatial selectivity of said electrodes is that they have several rings, so that the greater the number of rings, the greater the ability to select spatially the captured signals. It should be added that in this article certain weights are assigned to each ring that allow canceling the orthogonal derivative to the collection surface on a single exit sign. This document does not propose the possibility of incorporating variable weights in the outputs, nor the possibility of adjusting the weights to vary the spatial distribution of sensitivity, optimizing the acquisition of the desired signal sources, eliminating other unwanted signal sources (interferences ). Nor does it offer different outputs with a single multi-ring electrode.

The description focuses on the detection of signals from certain muscle fibers of the human body, with the weights obtained according to the criteria mentioned.

Also in the state of the art the article whose title is "Development of a tri-polar concentric ring electrode for acquiring accurate Laplacian body surface potentials" in which annular sensors are used, which among other aspects comments that using three-pole electrodes, can be cited, Composed of a central disk plus two rings, unwanted signals are attenuated more efficiently than using electrodes with fewer conductive poles. This article does not describe the weighting of the weights of the rings to change the field of sensitivities to improve the acquisition of a certain signal source against other interferences, but the annular configuration itself reduces better than conventional bipolar registers or that bipolar rings the interference (or noise) that affects such records globally. In this regard, it is also possible to cite Patent WO201 1056626-A1 (WALTER BESIO) with priority number US61 / 255,635 describing a multipolar electrode formed by a central disk and three rings for acquiring and recording bioelectric potential data. This document is not limited to configurations of a maximum of three rings, but also describes the use of a plurality of rings of conductive material, as indicated in its third claim. The sensors of the indicated documents, have a rigid substrate or support that prevent their perfect adaptation to the body contour, with the inconvenience that this represents, since this lack of adaptation affects the quality of the recorded signals, which are of the order of tens or hundreds of microvolts, so increasing the quality of the signals that are detected is very important for diagnosis, and consequently conventional systems do not provide the precision required for diagnoses, apart from not offering the necessary comfort for the user, as with the invention in which the sensor has a flexible nature. The discs and rings on the rigid supports are located on one side of the support and their connection with the control circuit is carried out by means of "tracks" to bring the tension of the conductor from the face in contact with the patient's surface to the other face of the support up to the circuit

control. This connection cannot be made with a flexible substrate because it does not allow "ways" to work double-sided.

In addition, none of the aforementioned documents allows the establishment of outputs with variable weights, nor the possibility of adjusting the weights to vary the spatial distribution of sensitivity, a circumstance that occurs in the invention.

DESCRIPTION OF THE INVENTION

In order to achieve the objectives and solve the aforementioned drawbacks, the invention has developed a new apparatus for measuring bioelectric signals on the body surface, which, like those provided in the prior art, comprise a sensor, which in turn comprises a insulating support, a patient support fixation adhesive, a disk-shaped conductor and at least one annular conductor concentric to said disk-shaped conductor, which are arranged on the insulating support to capture the voltages corresponding to the bioelectric signals in the area in which the support is fixed. The apparatus also comprises a circuit for processing the signals captured by the sensor. The main novelty of the invention resides in the fact that it is characterized in that the insulating support is flexible, the conductor being in the form of a disk and the at least one concentric annular conductor printed in ink or in conductive paste on said support. In this way, a configuration is obtained such that the sensor adapts to the surface contour of the area of the patient in which it is fixed. Another essential feature of the invention is that the insulating support is provided with a connector to which the disk-shaped conductor and the at least one concentric annular conductor are connected to obtain an interchangeable modular sensor configuration, which provides greater hygiene. by allowing discarding the sensors with each user. For this, the circuit for processing the signals picked up by the sensor comprises a complementary connector to which the sensor connector is connected. The connection of the disk-shaped conductor and of the at least concentric annular conductor with the connector is carried out by means of conductive tracks printed on the support and covered with a dielectric, on which the disk-shaped conductor and the at least one are printed. concentric annular conductor at the crossing points with the conductive tracks, so that the conductive tracks are short-circuited with said disk-shaped conductor and with said at least one concentric annular conductor.

In one embodiment of the invention it is provided that the flexible insulating support comprises a plurality of concentric annular conductors, so that the apparatus provides a plurality of voltage outputs. The signal processing circuit is configured to establish different weights at the voltage of each conductor at each of the outputs of the device, so that each output corresponds to different spatial distribution maps of sensitivity to the capture of surface bioelectric potentials , in relation to what is required in each application of measurement of surface bioelectric signals.

Each output signal of the signal processing circuit is a linear combination of the voltage of each of the conductors N, defined by V _ou t / = ∑¡ ^N a¡ / ^■ V¡; where j = 1, 2, ... M, where Vi is the potential that the conductor "i" is and the weight given to said voltage for the jth output.

The assignment of the weights depends mainly on the location of the electrode and the location of the desired signal source and the sources of interference, which vary for each subject under study and each application. Weights can be determined by the expert user who tunes to see the desired signal, or weights can be assigned automatically by applying signal processing techniques such as independent component separation (ICA) that can be programmed in the circuit . You can also perform a combination of both options, one for coarse adjustment and one for fine adjustment.

In addition, another embodiment of the invention comprises a sensor array in which the flexible insulating support is common to all of them, such that it includes several pickup sensors embedded in a flexible and adhesive matrix. The invention provides for the possibility of incorporating means for transmitting the output signals of the circuit to a remote processing center. Said transmission means may be wireless or connected to the remote processing center via cable. In order to facilitate a better understanding of this descriptive report, and being an integral part thereof, a series of figures are attached in which the object of the invention has been shown as an illustrative and non-limiting nature. BRIEF STATEMENT OF THE FIGURES

Figure 1.- Shows a schematic representation of an example of embodiment of the invention in which the apparatus comprises a sensor formed by a plurality of concentric annular conductors that are connected to a signal processing circuit. Figure 2.- It shows a schematic representation of the sensor for a case in which it comprises two annular conductors, and in which the arrangement of the dielectric that allows the connection of conductors 3 and 4 to the circuit 5 for treating the sensors is appreciated. signals without short circuits.

Figure 3.- Shows another embodiment in which a matrix of sensors arranged on a single flexible support is provided. Each sensor, as in Figure 1, comprises a plurality of conductors

annular

DESCRIPTION OF THE PREFERRED EMBODIMENT

Below is a description of the invention based on the figures mentioned above.

The invention relates to an apparatus for the non-invasive recording of bioelectric signals on the body surface, for which it comprises a sensor 1 provided with an insulating support 2 in whose central part is provided with a disk-shaped conductor 3 around which It comprises at least one annular conductor 4, concentric to said disk-shaped conductor 3. In the exemplary embodiment of Figure 1, the arrangement of N conductors with N-1 annular conductors 4 is provided for the collection of bioelectric voltages of the area over which the sensor is arranged. In said figure 1 the first two annular conductors 4 have been shown in full line and one in dashed line to indicate the existence of said N-1 annular conductors 4. Each of the conductors 3 and 4 is connected to a circuit 5 of treatment of the signals captured by conductors 3 and 4, for which it is envisioned that the insulating support 2 is provided with a connector 6 complementary to a connector 7 provided in circuit 5, so that it receives the different voltages picked up by conductors 3 and 4.

The connection of the disk-shaped conductor 3 and the concentric annular conductors 4 with the connector 6 is carried out by means of conductive tracks 1 1 printed on the insulating support 2 and covered with a dielectric 12, on which the conductor is printed on disk shape 3 and the at least concentric annular conductor 4 at the crossing points with the conductive tracks 1 1 avoiding its short-circuiting, as shown in figure 2.

The previous configuration provides a modular sensor that allows you to make your change when required, providing greater hygiene.

In order to allow the sensor to be fixed on the contour of the surface on which it is applied to the patient, an adhesive 8 is provided.

In addition to facilitate the coupling of the sensor 1 on the contour of the surface on which it adheres, it is envisaged that the insulating support 2 is flexible in nature, compatible with biomedical applications and supporting the temperatures reached for the deposition of the tracks conductors 1 1 and conductors 3 and 4, which are constituted by inks or pastes that are deposited on the insulating support 2. Conductive inks or pastes comprising silver or other high conductivity materials, must have good adhesion on polymers , be compatible with biomedical applications and withstand its injection or high temperatures to allow its application by screen printing on the support. First, conductive tracks 1 1 are printed and then coated with dielectric 12, then conductors 3 and 4 are printed, so that conductive tracks 1 1 is prevented from being short-circuited with conductors 3 and 4. In addition the conductive tracks 1 1 are protected by dielectric 12. The dielectric material must also have good adhesion with polymers and conductors, be compatible with biomedical applications and allow application by screen printing or inkjet. In the invention it has been assessed that conductors 3 and 4 can be deposited by chemical attack techniques, which have been ruled out because the flexible printed circuit boards (pcb) available in the market, in addition to being expensive, do not they allow to reach the degree of flexibility offered by the supports used in the present invention. In addition, a multilayer design is required, with interconnecting paths, which is very difficult and expensive to implement in flexible pcb.

The circuit 5 for processing the signals captured by the sensor is configured to establish different variable weights at the voltages captured by the concentric conductors providing different output signals, corresponding to different spatial distributions of sensitivity according to the application to which it is intended the device, that is to say, depending on the measurement that is desired, optimizing the registration of the bioelectric potentials to be measured. The number of annular conductors 4 is strongly conditioned by the application to which the apparatus of the invention is destined, so that a greater number of rings means having more degrees of freedom when generating the output signals of the system, since a greater number of modifiable weights are available to obtain a sensitivity map appropriate to the desired output according to the measurement to be performed. On the other hand, a greater number of rings can also entail a higher cost associated with the electronic components for the conditioning of the signals, and a greater complexity of the apparatus. Thus, for example, a sensor comprising a conductor in the form of a disk 3 and a single ring conductor 4 would be sufficient, in the case of the most basic applications, in which the bioelectric signal to be recorded is of a considerable level, is not subject to the possible presence of relevant sources of interference that need to be canceled, and there are no high demands regarding the control of the sensitivities map to the capture of the activity. An example of such applications can be the ECG record to determine the heart rate. However, if you want to register several signal generating sources that are, for example, at different distances from the sensor or a source subject to interference, it will be necessary to use a larger number of annular conductors 4. The basic criterion is to use at least as many rings 4 conductors in the sensor, as signal sources and interference are to be captured. An example in this regard would be the monitoring of pregnant women in which it is desired to capture the uterine bioelectric activity and fetal ECG. In this case the uterine muscle is closer to the body surface than the heart of the fetus that is deeper. In addition, the maternal ECG may be a source of interference, so in this case it would be recommended to use at least three annular conductors 4 in addition to the central disk 3.

With regard to the dimensions of conductors 3 and 4, it is recommended that they have the same area so that the input impedances to the amplification and conditioning stage of circuit 5 are theoretically as similar as possible, thereby reducing differences in the inputs and the common mode rejection (CMRR) is improved. Furthermore, it is recommended that the radial distance between the middle radius of the central disk 3 as well as the separation between the consecutive intermediate radii be the same. It is also recommended that the separation between the conductors be as large as possible, since in this way, the greater the difference between the signals captured by them.

Circuit 5 includes analog and digital circuitry for conditioning (amplification, and filtering) and obtaining M signals at its analog and / or digital output 10, so that they can be sent to other equipment, and therefore also includes the transmission interface from the same. Each output signal of circuit 5 is a linear combination of the voltage of each of the conductors N, and is defined:

where j = 1, 2, ... M, where Vi is the potential of the conductor "i" and _j the weight given to said voltage for the jth output.

In the particular case of a conventional bipolar register of a single output signal (where M = 1) and two conductors 3 and 4 are used, the pickup stage is formed by the central disk 3 and an annular conductor 4, the weights being corresponding of each of these signals a1 = G and a2 = -G, so that:

V1 being the signal picked up by the central disk 3 and V2 the voltage picked up by the ring ring 4.

In the case of a three-pole register in a bipolar configuration with a single output, the acquisition stage consists of the central disk 3 and two annular conductors 4, the weights corresponding to each of the signals a-, = 0.5. G, a ₂ = -G and ₃ = 0.5.G, so that the sensor output voltage is:

V _out = (0.5- (V1 + V3) -V2) -G

Likewise, to map the bioelectric activity on a surface associated with a certain organ, muscle or member, the system allows the combined use of several recording sensors of the same or different dimensions, such as the one shown in Figure 3 for which It provides a matrix of sensors 1 that are connected to the circuit 5 for processing the signals captured by each of said sensors 1.

In this case the number of sensors (K), as well as their arrangement on the Surface may vary depending on the bioelectric activity under study. So that for the kth sensor of Nk conductors and Mk outputs it will have:

where j = 1, 2, .... M _k and k = 1, 2, ... K. The total number of output signals is ∑k ^K Mk referred to k voltage reference terminals.

The treatment circuit allows outputs 10 of circuit 5 to be transmitted wirelessly or via cable to a remote processing center.

The weights assigned to the outputs of circuit 5 can be adjusted manually by means of dials or through software allowing changes during the registration process itself to adapt said weights until the morphology or signal component being registered is obtained. This configuration allows the user to visualize the effect of the changes in the weights on the output signals until they adjust to what is desired. It is recommended to start with default weight values and, during monitoring, make a final adjustment if necessary.

Claims

13 04-10-2013 2013/135931 PCT / ES2013 / 070156 CLAIMS

1. - BIOELECTRIC SIGNALS MEASURING EQUIPMENT ON BODY SURFACE BASED ON ADJUSTABLE ANNULAR SENSORS, comprising:

- a sensor (1) which, in turn, comprises:

- an insulating support (2)

- an adhesive (8) for fixing the support to the patient,

- a disk-shaped conductor (3) and at least one annular conductor (4) concentric to the disk-shaped conductor disk (3) and which are arranged on the insulating support (2) to capture the voltages corresponding to the bioelectric signals in the area where the insulating support (2) is fixed;

- and a circuit (5) for processing the signals picked up by the sensor; characterized in that the insulating support (2) is flexible on which the disk-shaped conductor (3) and the at least one concentric annular conductor (4) are printed on a material selected between ink and conductive paste, to adapt the sensor (1) to the contour of the surface on which it is fixed; and the insulating support (2) comprising a connector (6) to which the disk-shaped conductor (3) and the at least one concentric annular conductor (4) are connected; of connection to a complementary connector (7) provided in the circuit (5).

2. - BIOELECTRIC SIGNAL EQUIPMENT IN BODY SURFACE BASED ON ADJUSTABLE RING SENSORS, according to claim 1, characterized in that the connection of the disk-shaped conductor (3) and at least the annular conductor (4) concentric with the connector ( 6) is carried out by means of conductive tracks (1 1) printed on the insulating support (2) and covered with a dielectric (12), on which the disk-shaped conductor (3) and the at least one annular conductor are printed ( 4) concentric at the crossing points with the tracks

REPLACEMENT SHEET (Rule 26) conductive (1 1) avoiding its short circuit.

3. - BIOELECTRIC SIGNAL MEASURING DEVICE ON BODY SURFACE BASED ON ADJUSTABLE RING SENSORS, according to claim 2, characterized in that the flexible insulating support (2) comprises a plurality of concentric annular conductors (4) that provide a plurality of voltage outputs .

4. - BIOELECTRIC SIGNALS MEASURING DEVICE ON BODY SURFACE BASED ON ANNULAR SENSORS

ADJUSTABLE, according to claim 3, characterized in that it comprises at least as many conductive rings (4) as sources of signal and interference are to be captured in the performance of the measurement.

5.- BIOELECTRIC SIGNALS MEASURING EQUIPMENT IN BODY SURFACE BASED ON ADJUSTABLE RING SENSORS, according to claim 3, characterized in that the signal processing circuit (5) is configured to establish different variable weights at the concentric conductor voltages providing different output signals, corresponding to different spatial distributions of sensitivity; each output signal of the signal processing circuit (5) being a linear combination of the voltage of each of the conductors N, defined by ^Vout -f ^{= ∑¡N a¡ 'V¡; where} J = - ² - ^■■■ M, where M is the number of outputs, I saw the potential of the conductor "i" and add the weight given to that voltage for the jth output.

6. - BIOELECTRIC SIGNALS MEASURING EQUIPMENT IN BODY SURFACE BASED ON ADJUSTABLE RING SENSORS, according to any one of the preceding claims, characterized in that it comprises a matrix (9) of sensors (1) in which the flexible insulating support (2) It is common to such sensors (1).

7. - BIOELECTRIC SIGNAL MEASUREMENT DEVICE IN

REPLACEMENT SHEET (Rule 26) BODY SURFACE BASED ON ADJUSTABLE ANNULAR SENSORS, according to any one of the preceding claims, characterized in that it comprises means for transmitting the signals provided by the circuit (5) to a processing center.

REPLACEMENT SHEET (Rule 26)