DEVI E FOR THE JOINT ACQUISITION OF AT LEAST ONE SURFACE

I . ECT R< ) M Y <)( J R A 1* H I O SIGNAL AND ONE ECH RAPU!C I MAC OF A SAME PORTION OF A MUSCLE OF A LIVING BEING, IN PA TICULAR FOR NON-!NVASIVE APPLICATIONS. AM. ⁾ MANUFACTURING METHOD

THE EOF

DESCRIPTION

The present, invention relates to a device for the joint acquisition of a! least one surface electromyographic signal (slTiVIG) anil one eeho^raphic image of a same portion of a muscle of a living being, in particular lor non-invasive applications, in accordance with the preamble of ^' claim ! .

The present invention furlhcr relates to method for manufacturing said device.

It is known in the art that electromyography (EMG) is the representation of the electric signals generated b the contraction of a muscle,

Invasive or non-invasi e techniques may be used in order to record an electromyographic signal ( ΠΜ G ).

Invasive techniques require the use of intramuscular needles nnd ^' or wires, through which one. can gel information about specific and spatially-concentrated muscle areas, so as to be able to observe the activity of a few motor units or lens of motor units.

I stead, non-invasive techniques utilize surface electrodes to be positioned on an individual ^' s skin, said surface electrodes allowing to obtain more general and global information, while at the same time detecting the activity of hundreds of motor units. This type of surface electromyography (sh ^' MG) allows extracting informat ion about:

- the instants of activation of the muscle,

- the amplitude of the surface electromyographic signal sivYK.i). said amplitude being correlated to the number of motor units recruited,

- (he spectral characteristics of the signal, which vary ;.is a fund ion of muscular recruitment and fatigue.

Consequently, surface electromyography (sEMG) is a non-invasive Technique which allows studying (he phenomena at the basis of muscle contraction through the analysis of the electric signal generated during the contraction.

The electric potentials detected on the skin provide a surface representation of the potentials generated at muscular fibre level: for this reason, their properties depend on the geometric characteristics of the fibres, such as those relating to the position and orientation thereof with respect to the signal detection system.

During a muscle contraction, the position and orientation of the fibres with respect to the signal detection system may vary significantly, thus modifying the electromyographic diagram (EMG) accordingly. For this reason, many laboratory studies are based on a constant-force isometric contraction paradigm, which allows to conjecture the stationariness of the muscular architecture. However, in most applicative studies this paradigm is not applicable because it is not representative of the "physiological" muscle contraction and because the electromyographic signal (EMG) must be analyzed in dynamic conditions.

It is nonetheless important to observe that the muscular architecture may change significantly, for different contraction levels, also in strictly isometric conditions.

For these reasons, it is important to integrate the information of the electromyographic signal (EMG) with information about the anatomical characteristics of the signal source; such characteristics can be observed by using ultrasounds and the corresponding ultrasonographic images.

Said ultrasonographic images, in fact, make it possible to study the architecture of the muscle in vivo and to observe any geometric variations thereof during its contraction. For example, one interesting field of application of the joint analysis of echographic and surface electromyographic (sEMG) images is the study of the erect posture. In particular, it might be useful to be able to correlate the variations in the architecture of the surae triceps to the EMG electromyographic activation of muscular compartments in response to postural oscillations.

Consequently, a joint study of the surface electromyographic signal (sEMG) with at least one echographic image would turn out to be very useful to widen one's knowledge in this field.

Other application areas relating to the acquisition of electromyographic signals on the skin in conjunction with echographic images may find significant applications in sports medicine, ergonomics, and clinical neurophysiology. In these fields, in fact, many applications are possible which concern the sphere of neuromuscular system research: from basic studies on muscular electrophysiology to studies on the mechanisms that regulate postural control.

Possible clinical applications may concern the screening and diagnosis of myopathies and neuropathies. For example, a particularly interesting clinical application may relate to the early screening of amyotrophic lateral sclerosis (ALS), in that the joint utilization of ultrasound and surface electromyography (sEMG) may significantly increase the diagnostic sensitivity of said sclerosis.

A few publications have discussed the joint acquisition of a surface electromyographic signal (sEMG) and echographic images. The following publications can be referred to by way of example:

- De Oliveira L.F., Menegaldo L.L. "Individual-specific muscle maximum force estimation using ultrasound for ankle joint torque prediction using an EMG-driven Hill-type modeF. J. Biomech. 2010 Oct 19;43(14):2816-21 ;

- Rudroff T., Staudenmann D., Enoka R. M. "Electromyographic measures of muscle activation and changes in muscle architecture of human elbow flexors during fatiguing contractions". J. Appl. Physiol. 2008 Jun; 104(6): 1720-6.

- Mademli L, Arampatzis A. "Mechanical and morphological properties of the triceps surae muscle-tendon unit in old and young adults and their interaction with a submaximal fatiguing contraction" . J Electromyogr. Kinesiol. 2008 Feb;18(l):89-98.

- Loram ID, Maganaris CN, Lakie M. "Human postural sway results from frequent, ballistic bias impulses by soleus and gastrocnemius". J. Physiol. 2005 Apr. l ;564(Pt 1):295-311.

- Hodges PW, Pengel LH, Herbert RD, Gandevia SC. "Measurement of muscle contraction with ultrasound imaging". Muscle Nerve. 2003 Jun;27(6):682-92.

It must be pointed out that in all of the above-mentioned publications the surface electromyographic signal (sEMG) and the echographic images have been acquired at distinct moments or from different muscle portions; as a consequence, the signals thus acquired and possibly recorded cannot be considered to be representative of a muscular contraction of one well-determined and precise muscle portion.

In particular, in the cases described in the above-mentioned publications, the echographic images and the surface electromyographic signals (sEMG) have been recorded at distinct moments or from different muscle portions because, in order to carry out the echographic analysis and the surface electromyographic analysis on the same muscle portion, it would have been necessary to position the echographic probe over the electrodes for detecting said surface electromyographic signals (sEMG). In the cases described in the above-mentioned publications, after positioning of the echographic probe over known electrodes for detecting said surface electromyographic signals, the echographic image of the muscle tissue would have turned out deformed by the high acoustic impedance of the materials composing the known electrodes, while the gel used as an interface between the echographic probe and the skin would have caused short circuits between the known electrodes for detecting the surface electromyographic signal (sEMG).

Document WO2009089280 relates to a device for acquiring at least one electromyographic signal and at least one echographic image of a living being; in particular, according to said document the device is used in an invasive manner, particularly in order to obtain an image of the prostate of a human being.

It must be pointed out that, for invasive applications, the problem of the interface between the ultrasonographic probe and the tissue is less important than in non-invasive applications, since in invasive applications the interface is mediated by the mucosa, which improves the interface between the probe and the tissue.

However, no mucosa is present on the surface of the skin of a living being, and therefore it cannot improve the interface between the probe and the tissue. It is thus apparent that the teachings of document WO2009089280 cannot be adopted for non-invasive applications in order to obtain a device for the joint acquisition of at least one surface electromyographic signal (sEMG) and at least one echographic image of a same portion of a muscle of a living being.

In this frame, it is the main object of the present invention to overcome the drawbacks of the prior art by providing a device which allows to acquire at least one surface electromyographic signal (sEMG) in conjunction with at least one echographic image of a same portion of a muscle of a living being, in particular for non-invasive applications. It is a further main object of the present invention to design said device in such a way that the echographic probe can be positioned over the electrodes for detecting the electromyographic signals in a manner such that said echographic probe will not be adversely affected by the presence of said electrodes.

In particular, it is one object of the present invention to design said device in such a way that the echographic image will not be deformed by the acoustic impedance of the materials used for manufacturing the device itself or those used for manufacturing the electrodes for detecting said electromyographic signals.

It is another main object of the present invention to design said device in such a way that no short circuit will occur between the elements that make up the device, in particular between the electrodes for detecting the surface electromyographic signal (sEMG). Yet another main object of the present invention is to provide a device which is particularly suited to non-invasive applications.

Said objects are achieved by the present invention through a device for the joint acquisition of at least one surface electromyographic signal (sEMG) and at least one echographic image of a same portion of a muscle of a living being, in particular for noninvasive applications, and through a corresponding method for manufacturing said device, which incorporate the features set out in the appended claims, which are an integral part of the present description.

Further objects, features and advantages of the present invention will become apparent from the following detailed description and from the annexed drawings, which are supplied by way of non-limiting example, wherein:

- Figs, la and lb respectively show a perspective view and a sectional view of a portion of the device for acquiring at least one surface electromyographic signal

(sEMG), in particular for non-invasive applications, in accordance with the present invention;

- Fig. 2 shows a sectional view of a second embodiment of the device of Fig. 1 ;

- Figures 3 a to 4d show different steps of a method for manufacturing the device depicted in Figures 1 and 2.

Referring now to the annexed drawings, in Figs, la and lb reference numeral 1 designates as a whole a device for acquiring at least one surface electromyographic signal (sEMG) of a muscle of a living being, in particular for non-invasive applications. In accordance with the present invention, said device 1 comprises a first layer 10 consisting of cross-linked polymers, said first layer 10 comprising at least one cavity 11 adapted to house at least one first portion 12A of an electrode 12 for acquiring said at least one surface electromyographic signal (sEMG).

Preferably, said first layer 10 is so designed as to be adapted to adhere to the skin of said living being, so as to reduce the presence of any air bubbles.

Furthermore, in accordance with the present invention said first layer 10 is transparent to ultrasounds, so as to allow obtaining an acoustic impedance adaptation such that a joint acquisition of said at least one surface electromyographic signal and of said at least one echographic image of a same muscle portion can be obtained. Said first layer 10 consisting of cross-linked polymers is made of rubber, in particular low-density rubber; in particular, said first rubber layer 10 has a base mass/catalyst concentration (or mixing ratio) substantially equivalent to a ratio of 1 to 3.

In substance, said first layer 10 has a base mass/catalyst concentration substantially suitable for satisfying the following relation (A):

base mass : catalyst = 1 : 3

Preferably, said base mass and said catalyst consist of the material known as Elite Double 8 ^® , available from company Zhermack S.p.A.

According to the present invention, said electrode 12 is of the wire type, in particular being made of metallic material; preferably, the thickness of said wire electrode 12 is comprised between 20 μιη and 150 μιη, in particular substantially equal to 50 μηι.

In a preferred embodiment, said wire electrode 12 is made of chlorinated silver, so as to optimize the interface between the electrode 12 and a conductive paste (not shown in the drawings) housed in said cavity 1 1. It is however clear that the wire electrode 12 may also be made of different types of metal.

As can be seen especially in Fig. lb, said electrode 12 comprises a second portion 12B adapted to be connected to a printed circuit board 2, said printed circuit board 2 allowing the electrode 12 to be connected to a processing and/or display system 3. For example, said processing and/or display system 3 (diagrammatically shown in Fig. lb) may comprise a processor associated with a screen to process and display the signals coming from said electrode 12.

In addition, the electrode 12 comprises a third portion 12C, which is hook-shaped or bridge-shaped and preferably positioned above said first layer 10.

In a preferred embodiment, said at least one cavity 11 comprises a plurality of cavities 1 1 adapted to house at least one first portion 12A of a plurality of electrodes 12; preferably, the cavities 11 of said plurality of cavities 1 1 are arranged in matrix form, the centre of each cavity 11 being in particular positioned at a distance comprised between 2.5 mm and 70 mm, preferably at a distance of approximately 10 mm, from the centre of a contiguous cavity 11.

Moreover, said cavity 1 1 is adapted to house a conductive paste (not shown in the drawings), in particular water-based, which allows creating an optimal connection between the skin of a living being and said electrode 12, in particular said first portion

12P of the electrode 12. Preferably, said conductive paste comprises the following components: Polyoxyethylene (20) Cetyl Ether, Water, Glycerin, Calcium Carbonate, 1 ,2-Propanediol, Potassium Chloride, Gelwhite ^® , Sodium Chloride, Polyoxyethylene (20) Sorbitol, Methylparaben, Propylparaben.

In particular, said conductive paste is the product known as Ten 20 ^® Conductive Paste, available from Weaver and Company.

In accordance with the present invention, said device 1 further comprises a second layer 20 consisting of cross-linked polymers having a higher density than the first layer 10, said second layer 20 being adapted to give mechanical consistency to the device 1, to incorporate at least one second portion 12B of said electrode 12, and to allow it to be connected to a printed circuit board 2.

In particular, also the second layer 20 is transparent to ultrasounds and allows obtaining an acoustic impedance adaptation such that a joint acquisition of said at least one surface electromyographic signal and of said at least one echographic image of a same muscle portion can be obtained.

Preferably, said second layer 20 is made of rubber, in particular said second layer 20 having a base mass/catalyst concentration (or mixing ratio) substantially equivalent to a ratio of 1 to 1.

In substance, said second layer 20 has a base mass/catalyst concentration substantially suitable for satisfying the following relation (B):

base mass : catalyst = 1 : 1

Preferably, also for the second layer 20 said base mass and said catalyst consist of the material known as Elite Double 8 ^® , available from company Zhermack S.p.A.

Fig. 2 shows a sectional view of a second embodiment of the device 1 according to the present invention.

In this figure, one can see that said device 1 comprises a third layer 30 for facilitating the coupling of the device 1 to an echographic probe 4, in particular said third layer 30 being made of a material substantially corresponding to that of the first layer 10.

As a consequence, also the third layer 30 consists of cross-linked polymers; preferably, said third layer 30 is made of rubber, in particular said third layer 30 having a base mass/catalyst concentration (or mixing ratio) substantially equivalent to a ratio of 1 to 3. In this embodiment, also the echographic probe 4 preferably comprises at least one first surface 4 A suitable for being coupled to said third layer 30, in particular said at least one surface 4A being made of a material substantially corresponding to that of the third layer 30.

The echographic probe 4 preferably further comprises at least one second surface 4B for supporting and/or holding up said echographic probe 4.

In Fig. 2 it can then be observed that also the echographic probe 4 is connected to said processing and/or display system 3, so that a joint acquisition of said at least one surface electromyographic signal and of at least one echographic image of a same portion of said muscle can be obtained.

It must be pointed out that the representation shown in Fig. 2 of the echographic probe 4 and of the connection thereof to the processing and display system 3 may also be adopted in the first embodiment of the device 1 shown in Figs, la and lb; for example, the echographic probe 4 of Fig. 2 may differ from an echographic probe (not shown) suitable for the first embodiment for lacking the first surface 4A. It is also clear that said echographic probe 4 may have a different shape than shown in Fig. 2.

It is apparent from the above description that the particular design of the device 1 according to the present invention allows to overcome the drawbacks of the prior art and to provide a device 1 which is suitable for acquiring at least one surface electromyographic signal (sEMG) in conjunction with at least one echographic image of a same portion of a muscle of a living being.

In fact, the special design of the device 1 allows positioning an echographic probe (e.g. like the one designated by reference numeral 4 in Fig. 2) over the electrodes 12, so that it will not be adversely affected by the presence of said electrodes 12 or from other parts making up the device 1, particularly the first layer 10 and possibly also the second layer 20 and the third layer 30.

In particular, the device 1 according to the present invention is so designed as to allow obtaining an echographic image which will not be deformed by the acoustic impedance of the materials that compose the device 1 itself, in particular those of said electrodes 12, of the first layer 10, and possibly also of the second layer 20 and the third layer 30. Furthermore, the special provisions of the device 1 according to the present invention allow to prevent any short circuits from occurring between the elements that make up the device 1 ; in particular, the presence of the cavities 11 (which are adapted to house the electrodes 12 and a conductive paste) allows creating an optimal connection between the skin of a living being and said electrodes 12, while at the same time preventing any short circuits from occurring between the electrodes 12.

Thanks to the special provisions of the present invention, it is apparent that the device 1 is particularly suited to non-invasive applications.

The following will describe a method for manufacturing a device 1 for the joint acquisition of at least one surface electromyographic signal (sEMG) and one echographic image of a same portion of a muscle of a living being, in particular for noninvasive applications.

In particular, said method is shown in Figures 3a to 4d and comprises the following steps:

a) preparing a mould 100 having a base 101 and an edge 102 protruding from said base 101, said base 101 comprising at least one hole 110 (see Fig. 3a);

b) positioning at least one body 120, in particular cylindrical in shape, into said at least one hole 110 (see Fig. 3b);

c) inserting a first layer 10 consisting of cross-linked polymers into said mould 100 (see Fig. 3c), said first layer 10 being transparent to ultrasounds;

d) removing said at least one body 120 from said at least one hole 110 when the first layer 10 is polymerized, so as to obtain at least one cavity 1 1 in the first layer 10, in particular said removal of the body 120 from the hole 1 10 taking place in a direction (D in Figs. 4a and 4b) opposite to said first layer 10 (see Figs. 4a and 4b); e) inserting into said cavity 1 1 at least one first portion 12A of an electrode 12 of the wire type, in particular made of metallic material, suitable for the acquisition of at least one surface electromyographic signal (sEMG), in particular said electrode 12 comprising a third portion 12C, which is hook-shaped or bridge-shaped and preferably positioned above said first layer 10 (see Fig. 4b).

Preferably, said wire electrode 12 is made of chlorinated silver; however, said electrode 12 may also be made of different materials.

Furthermore, the first layer 10 is so designed as to be adapted to adhere to the skin of said living being, so as to reduce the presence of any air bubbles.

The method for manufacturing the device 1 according to the present invention may further comprise the following steps:

f) positioning into the mould 100 at least one printed circuit board 2, in particular of the flexible type, and connecting a second portion 12B of the electrode 12 to said printed circuit board 2 (see Fig. 4c); g) inserting into said mould 100 a second layer 20 consisting of cross-linked polymers having a higher density than the first layer 10, said second layer 20 being adapted to give mechanical consistency to the device 1, to incorporate at least one second portion 12B of said electrode 12, and to allow it to be connected to said printed circuit board 2 (see Fig. 4d).

According to the present invention, said step c) is preferably obtained by inserting into said mould 100 a first layer 10 made of rubber, in particular low-density rubber, said first layer 10 having a base mass/catalyst concentration (or mixing ratio) substantially equivalent to a ratio of 1 to 3, i.e. a base mass/catalyst concentration which can substantially satisfy the following relation (A):

base mass : catalyst = 1 : 3

Furthermore, according to the present invention, said step g) is obtained by inserting into said mould 100 a second rubber layer 20 having a base mass/catalyst concentration (or mixing ratio) substantially equivalent to a ratio of 1 to 1, i.e. a base mass/catalyst concentration which can substantially satisfy the following relation (B):

base mass : catalyst = 1 : 1

Said base mass and said catalyst of the first layer 10 and of the second layer 20 preferably consist of the material known as Elite Double 8 ^® , available from company Zhermack S.p.A.

It is therefore clear that the first layer 10 and the second layer 20 are adapted to create an impedance adaptation such that a joint acquisition of said at least one surface electromyographic signal and at least one echographic image of a same portion of said muscle can be obtained.

The method according to the present invention may further comprise the step h) of inserting into said mould 100 a third layer 30, in particular made of a material substantially corresponding to that of the first layer 10.

Moreover, in accordance with the method of the present invention, said step a) may be carried out by making a plurality of holes 110 on said base 101, and said step b) may be carried out by positioning a plurality of bodies 120 into said plurality of holes 110.

Said step d) may then be carried out by inserting a portion of the printed circuit board 2 into at least one groove 102S (especially visible in Figures 3a to 3c and 4c to 4d) present in the edge 102.

In a preferred embodiment, said step e) is preceded by a step e-1) of making said electrode 12 of the wire type with a thickness comprised between 20 and 150 μπι, in particular substantially corresponding to 50 μιη.

Furthermore, said step e) and/or said step g) and/or said step h) may be followed by a step i) of inserting into said at least one cavity 1 1 a conductive paste, in particular water- based, which allows creating an optimal connection between the skin of a living being and said electrode 12.

The advantages of a device 1 for the acquisition of a surface electromyographic signal of a muscle of a living being, in particular for non-invasive applications, and of a related manufacturing method according to the present invention are apparent from the above description.

In particular, such advantages lie in the fact that the particular design of the device 1 allows to overcome the drawbacks of the prior art and to provide a device 1 which is suitable for acquiring at least one surface electromyographic signal (sEMG) in conjunction with at least one echographic image of a same portion of a muscle of a living being.

In fact, the special design of the device 1 allows positioning an echographic probe (designated by reference numeral 4 in Fig. 2, although said echographic probe may be made differently than shown in said Figure) over the electrodes 12, so that it will not be adversely affected by the presence of said electrodes 12 or from other parts making up the device 1, particularly the first layer 10, the second layer 20, and possibly also the third layer 30.

In particular, the device 1 according to the present invention is so designed as to allow obtaining an echographic image which will not be deformed by the acoustic impedance of the materials of the device 1 itself, in particular of said electrodes 12.

Furthermore, the special provisions of the device 1 according to the present invention allow to prevent any short circuits from occurring between the elements that make up the device 1 ; in particular, the presence of the cavities 1 1 (which are adapted to house the electrodes 12 and a conductive paste) allows creating an optimal connection between the skin of a living being and said electrodes 12, while at the same time preventing any short circuits from occurring between the electrodes 12.

Thanks to the special provisions of the present invention, it is apparent that the device 1 is particularly suited to non-invasive applications.

The device and method described herein by way of example may be subject to many possible variations without departing from the novelty spirit of the inventive idea; it is also clear that in the practical implementation of the invention the illustrated details may have different shapes or be replaced with other technically equivalent elements.

It can therefore be easily understood that the present invention is not limited to the above-described device and method, but may be subject to many modifications, improvements or replacements of equivalent parts and elements without departing from the inventive idea, as clearly specified in the following claims.