WO2017202628A1

WO2017202628A1 - Method and device for characterising the skin

Info

Publication number: WO2017202628A1
Application number: PCT/EP2017/061463
Authority: WO
Inventors: Jean-Luc Gennisson; Charles HUDIN; Mickaël TANTER; Miguel BERNAL RESTREPO
Original assignee: Centre National De La Recherche Scientifique - Cnrs -; INSERM (Institut National de la Santé et de la Recherche Médicale)
Priority date: 2016-05-27
Filing date: 2017-05-12
Publication date: 2017-11-30
Also published as: FR3051657A1

Abstract

A method for characterising the skin, that involves propagating shear waves in the skin (P) of a mammal while subjecting the skin to different successive stretching operations in a stretching direction (D), and capturing the shear waves after propagation in order to determine values of a shear wave propagation parameter depending on the stretching operation. Said measurements are carried out in first and second different directions (X, Y). A reference stretching operation is determined, for which the propagation parameter is identical in the first and second propagation directions, and the natural tension of the skin is determined as a stretching stress in the skin corresponding to the reference stretching operation.

Description

Method and device for characterizing the skin

FIELD OF THE INVENTION

The present invention relates to methods and devices for characterizing the skin.

BACKGROUND OF THE INVENTION

The FR3016791 discloses a method of charac ^¬ authorization of the skin, comprising a measuring step during which it is propagating waves shearing in a measurement zone belonging to the skin of a mammal while subjecting the skin in the area of me ^¬ sure, at different successive stretching in a di ^¬ rection stretching (stretching the value of this can be positive - elongation of the skin - negative - skin contraction - or zero), it captures said waves shear ^¬ LEMENT after propagation and is determined from the sensed waves, values of at least one shear wave propagation parameter in the measurement area in func ^¬ of stretching,

the method further comprising at least one step of charac ^¬ térisation during which it is determined, based on said values ^¬ propagation parameter, a natural voltage value of the skin (i.e. the voltage of the skin at rest, in the absence of stretching).

OBJECTS AND SUMMARY OF THE INVENTION

The present invention is intended to per ^¬ fectionner this method and apparatus the implementing, in particular to determine more reliably the natural tension of the skin.

For this purpose, the invention proposes a device for characterizing the skin, comprising:

at least one of these wave generating probe ^¬ saillement adapted to be applied against the skin of a mammal and for generating in the skin a wave cisail- also,

at least one probe of ultrasound measurement adap ted ^¬ to be applied against the skin and for measuring at least one shear wave propagation parameter in a measurement area of the skin,

- a strain gauge adapted to apply to the skin, in the measuring zone at successive stretches dif ^¬ ent in a specific direction of stretching,

a control device for controlling the shear wave generating probe, the probe me ^¬ sour and the extensometer, the control device being adapted to perform successive measurements of said para ^¬ meter shear wave propagation in the measurement zone, and to apply dif stretching ^¬ ent to the skin by the extensometer,

the characterization means adapted to note ^¬ riser of the first and second sets of corres measures ^¬ respectively sponding to the first and second direc ^¬ different tions of propagation of shear waves, each of the first and second sets of measurement include an ^¬ ing at least one of values of the propagation parameter for different stretches, said characterization means being adapted to determine a reference stretch for which said propagation parameter is identical in the first and second propagation directions, and to determine the natural tension of the skin as a con ^¬ constraint stretching in the skin corresponding to said going ^¬ their reference stretching.

Thanks to these provisions, the natural tension of the skin can be determined reliably and simply.

In embodiments of the device according to the invention, one or more of the following provisions may also be used:

the device comprises means for moving the shear wave generation probe and the measurement probe so as to successively align them according to the first and second propagation directions (alternately with each stretching value, or by moving the probes between two series of measurements to different stretching values);

the device comprises first and second pairs of probes, each comprising a probe genera ^¬ shear wave tion and a measuring probe échogra- phic, the first pair of probes being aligned in the first direction of propagation and the second pair sensors being aligned in the second direction of propaga ^¬,

the control means being adapted to perform the first set of measurements by the first pair and the second set of measurements by the second pair;

The extensometer comprises a force sensor adapted to measure a stretching force applied to the skin for each stretching value, the control means being adapted to store a value representative of said stretching force for each stretching value. and to determine the natural tension of the skin by a predetermined re ^¬ tion from said stretching force corresponding to the reference stretch.

Furthermore, the invention also provides a characterization of the skin using a device as defined above, comprising a measuring step during which it is propagating shear waves in ^¬ a measurement area belonging to the skin of a mammal while subjecting the skin, in the area of me ^¬ sour at different successive stretching in a di rection ^¬ constant stretching, it captures said shear wave after propagation and the values of at least one parameter of the pro- pagation of the shear wave in the measurement zone according to the stretch,

the method further comprising at least one characterization step during which a value of natural tension of the skin is determined from said values of the propagation parameter,

characterized in that in the measuring step, the shear waves are propagated respectively in first and second different directions substantially parallel to the skin and said at least one propagation parameter is determined in each of said first and second ^di¬ rections at different stretching values,

and in that the step of ion caractérisât, determining a reference for stretching said propagation parameter which is same in the first and second propagation ^¬ direc tions and skin natural voltage is determined as a stretching stress in the skin corresponding to said reference stretch.

In embodiments of the method according to the invention, one or more of the following provisions may also be used:

- the propagation parameter measured during the measuring step is representative of a speed of propa ^¬ shear wave gation in the skin;

- during the measuring step, the shear wave is generated from an outer surface of the skin and measuring said parameter from said outer face ^¬ ultrasound;

during the measuring step, the generating shear waves by shear wave generating probe pressed against the surface of OUTSIDE ^¬ higher skin and measuring said parameter propaga ^¬ using a probe ultrasound measurement app ^¬ cated against said outer surface, and one imposes said sequentially stretching said outer surface, and during said measuring step, the shear wave ge ^¬ neration probe and the measurement probe ali ^{¬ ¬} ings are arranged successively in the first and second propagation directions;

during the measuring step, first and second pairs of probes applied to the outer surface of the skin, each comprising a shear wave generation probe and an ultrasound measurement probe, are used, the first pair of probes being aligned in the first direction of propagation and the second pair of probes being aligned in the second direction of propagation,

first shear waves are generated by the shear wave generation probe of the first pair and said propagation parameter for said first shear waves is measured using the measurement probe of the first pair,

second shear waves are generated by the second pair shear wave generation probe and said propagation parameter for said second shear waves is measured using the second pair measurement probe;

the first and second directions of propagation are substantially perpendicular to one another; - the first propagation direction is sensitive ^¬ parallel to the direction of stretching;

during the measuring step, a stretching force applied to the skin is measured for each stretching value and the natural skin tension is calculated by a predetermined relationship from said stretching force corresponding to the stretching reference.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention In the following description of two of its embodiments, given by way of non-limiting example, with reference to the accompanying drawings, will appear.

On the drawings:

- Figure 1 is a schematic view of a wholesaler ^¬ skin characterization operative part according to a first embodiment of the invention,

FIG. 2 is a view from below of the ultrasonic measuring head of the device of FIG. 1,

FIG. 3 is a block diagram of the device of FIG. 1,

FIG. 4 is a schematic example of a propagation velocity curve of a shear wave between the ultrasound probes of the device of FIG. 1, in two different directions,

and FIGS. 5 to 7 are views similar to FIGS. 1 to 3, in a second embodiment of the invention.

DESCRIPTION DETAILED

In the different figures, the same references designate identical or similar elements.

Figure 1 shows a characterization device 1 for characterizing the skin P of an animal or human mammal. In humans, the skin P may have a total thickness of the order of 1 to 3 mm, usually of the order of 1 mm, depending on the location of the body in the usual cases. The skin P consists of the epidermis located on the surface of the skin and having a small thickness, for example of the order of 0.1 mm, and the dermis which is underlying the epidermis. The dermis covers a layer of subcutaneous fat.

The Characterization 1 device may include a measuring device 2 and a former controller 3 ^¬ dull. The external control device 3 may for example be a computer, a "smartphone" or other. The external control device 3 can be connected to dispo ^¬ operative part measuring 2 via a wired or wireless link for the transmission of data and commands.

The measuring device 2 may possibly be a portable device intended to be held in the hand by a user. It may comprise an extensometer comprising two stretching members 3, 4 which are movably mounted on the body of the measuring device 2 so as to be able to move away from or close to each other along the double arrow D, in parallel to an X axis.

The stretching members 3, 4 may have, for example, in the form of rigid plates intended to be applied to the skin P with a certain force along an axis Z perpendicular to the skin. The stretching members 3, 4 may for example have, on their faces coming into con tact with the skin ^¬ P, sufficiently rough surfaces so that the relative movements of the stretching members 3, 4 result in stretching of the skin P in the measurement zone between the two stretching members 3, 4. The value of this stretch can be positive (skin elongation), negative (contraction of the skin) or zero.

As shown in Figure 2, the measuring device 1 further comprises at least one wave generating ultrasonic probe 7 shear adapted to be ap ^¬ pliquée against the skin P to generate therein a wave Shear ^¬ LEMENT, and at least one ultrasound measurement probe 8 adapted to be applied against the skin P and to capture the shear wave after propagation in the skin P.

These probes 7, 8 may for example be included in a measuring head 6 (FIGS. 1 and 2) belonging to the measuring device 2. More particularly, the probes 7, 8 may be disposed on a face 6a of the measuring head 6, intended to be applied to the skin P.

The measuring head 6 can be mounted movably on the body of the measuring device 2 according to the double arrow H, parallel to the aforementioned Z axis, so as to be able to apply the measuring head 6 to the skin P.

In the first embodiment shown in FIGS. 1 and 2, the measuring head 6 can be rotatably mounted relative to the body of the measuring device 2, around a ZO axis of rotation parallel to the above-mentioned Z axis. ^¬ mentioned, according to the double arrow R.

The measuring head may optionally be carried by a rigid arm 5 mounted to move on the body of the measuring device 2 according to the double arrow H, the measuring head 6 being rotatable according to the double arrow R with respect to the arm 5. The arm 5 may for example extend along a Y axis perpendicular to the aforementioned X, Z axes.

As shown in FIG. 3, the measuring device may comprise an electronic controller (CU) 12 or other central unit, connected to:

to the ultrasonic probes 7, 8 (S1, S2), to actuators 9-11 (M1, M2, M3) such as stepper motors respectively controlling the movements of at least one of the stretching members 4, 5 according to the double arrow D (corresponding to the so-called stretch direction), the arm 5 along the double arrow H and the measuring head according to the double arrow R,

a force sensor 13 (F) sensing the stretching force applied to the skin P by the stretching members 3, 4.

The probes 7, 8 here each comprise at least one ultrasound transducer in the example considered here, but the probe used to generate the shear waves. could possibly be another device such as mechanical percussion device capable of generating a shock at the surface of the skin P, a speaker or pot vibrate generating low frequency acoustic pulses, or other.

When the probe shear wave generation ^¬ 5 includes an ultrasonic transducer generates an ultrasonic wave preferably compression focused in the thickness of the skin and in particular the dermis, to a depth of for example 0, 1 and 3 mm, preferably between 0.1 and 1 mm (especially at a depth of the order of 0.5 mm). This ultrasound wave is emitted pen ^¬ ing a short time for each measurement, and generates the wave above ^¬ saillement by moving the skin tissue by a phenomenon of radiation pressure, known per se.

When it is desired to perform measurements ca ^¬ ractériser the skin P, stretching the bodies is applied 3, 4 and the measurement head 6 of the skin P and launches a series of measurements using the control device external 3.

The external control device 3 makes, by means of the controller 12, a first measurement in the initial position of the stretching members 3, 4 (that is to say for a zero stretch) with the probes 7, 8 aligned in a first direction of propagation. During this measurement, the controller 12 causes a shear wave to be emitted by the probe 7, in a manner known per se, for example by causing the probe 5 to transmit an ultrasound wave of compression focused in the skin, for example on the principle general explained in WO2004 / 021038.

Then the controller 12 causes the passage of this shear wave to be detected by the ultrasound probe 8. For this purpose, the controller 12 causes the echo probe to emit graph 8 compression ultrasound waves, of pre ^¬ ference not focused or focused at long distance, fast rate (for example 300 shots per second or more), and said ultrasound probe 8 captures ultrasonic signals reverberated by the skin, as explained in particular in documents WO00 / 55616 and WO2004 / 021038: these measurements make it possible (in particular by virtue of the presence of re ^¬ flexing particles of ultrasound in skin P) to determine the internal displacements or deformations of skin P over time in comparison with the ultrasound probe 8, for example by correlation calculations on the cap ^¬ tees signals, and thus to identify the passage of the elastic shear wave opposite the ultrasound probe 6, and at each depth in the For example, the passage of the shear wave can be located at a predetermined number of depths in the skin, for example between 10 and 30 depths. s. The controller 12 then deter ^¬ mine, at each depth, the flight time t of the shear wave between the probes 7, 8, which it can deduce the propagation velocity of v = d / t, where d is the said ^¬ As a variant, the controller 12 could determine another propagation parameter of the shear wave from the flight time t.

The propagation parameter (v or other) is transmitted by the controller 12 to the external control device 3 with the measurement f given by the force sensor 13. The external control device 3 furthermore has the stretch, by the relative displacement x between the stretching members 3, 4 at each measurement relative to the initial position of the stretching members 3, 4 (in this case x = 0 for the initial measurement). The ex ^¬ control device 3 can deduce the tensile stress c imposed on the skin P from the stretching force f, by a predetermined rela ^¬ tion specific to the configuration of the organs 3, 4. This predetermined relationship can be determined, for example empirically once and for all, during the design of the control device.

This predetermined relationship may be of the type c = f / (lh), where 1 is the length of skin P secured with each stretching member 3, 4 (length along the Y axis) and h the thickness of the skin P . the thickness h may be possible ^¬ determined by the ultrasound probe 8 to the skin P being characterized, or the thickness h may be fixed once and for all to a mean value, for example 2 mm.

This measurement is repeated for x = 0 by aligning the probes 7, 8 in a second direction of propagation different from the first direction of propagation. To do this, the controller 12 can raise the arm 5 to move the measuring head 6 of the skin P, rotate the measuring head 6 and then down to apply against the skin P.

The first and second directions are perpendicular to each sow advantageously and preferably cor ^¬ spond respectively to the axes X, Y.

The measurements in the first and second propagation direc tions ^¬ X, Y are then repeated in MOVE ^¬ cant successively stretching members 3, 4 relative to each other along the stretching direction D, pre ^¬ ference in both directions from the position ini tial ^¬, and while maintaining the stretching members 3, 4 and the measurement head 6 pressed against the skin P.

It will be noted that the measuring device 2 could possibly first perform all the measurements in the first direction of propagation X then all the measurements in the second direction of propagation Y.

During these steps, successive steps, the pa ^¬ rameter propagation v and the tensile stress are recorded by the external controller 3 for the first and second propagation directions X, Y.

At the end of the measurements, as shown in fi ^¬ Figure 4, the external control device 3 therefore provides:

- a first curve propaga parameter ^¬ v in the first direction of propagation X func ^¬ tion of the tensile stress c, shown in phantom on Figure 4,

- a second curve of the propagation parameter v in the second direction of propagation Y func ^¬ tion of the tensile stress c, represented in solid lines in the figure 4.

In Figure 4, note that the first curve may have a hysteresis (path different from the first curve when putting in tension and when RelA ^¬ mation traction). Note also that con ^¬ entte is noted in Figure 4 arbitrary unit (for example by dividing the actual stress by a predetermined reference stress).

The first and second curves intersect a point corresponding to a so-called reference stretch, reference stretching, corresponding to a stress of trac ^¬ negative tion -C0 imposed on the skin (therefore a compressive stress). This tensile stress is the opposite of the natural tension of the skin C0.

This C0 value is particularly useful for cosmetology or dermatology in order to characterize the state of the skin.

The second embodiment of the invention, shown in Figures 5 to 7, similarly to the pre ^¬ Mière embodiment, in its structure and func tioning ^¬. This second embodiment is say ^¬ guishes of the first embodiment in that the measuring head 6 is not rotatable and has two pairs of probes 7, 8, 7a (S'1), 8a (S'2). The first pair of sensors 7, 8 is identical to the pair of probe of the first embodiment and looking in the pre ^¬ Mière propagation direction (e.g., along the axis X), while the second pair of probes 7, 8 is identical to the pair of probes of the first embodiment but oriented in the second direction of propagation (for example along the Y axis). In this case, the actuator 11 mentioned above is deleted. This second embodiment of ^¬ tion makes it possible to perform measurements faster, since it is not necessary to rotate the measuring head 6 to make the measurements in the first and second propagation directions. For each amount of stretch, can successively carry out the measurement of the propagation parameter in the first direction using the pre ^¬ Mière pair of probes 7, 8, then in the second direction using the second pair of probes 7a, 8a.

In all cases, the direction of stretch D is constant throughout the characterization process.

Claims

1. Device for characterizing the skin, ^comprising :

at least one ci ^¬ sonillement wave generation probe (7, 7a) adapted to be applied against the skin of a mammal and to generate a shear wave in the skin,

at least one echographic measuring probe (8, 8a) adapted to be applied against the skin and for measuring at least one parameter of propagation of the shear wave in a measurement zone of the skin,

an extensometer (3, 4, M1) adapted to apply to the skin, in the measurement zone, successive stretching ^¬ different sifs in a direction of stretching (D) determmi ^¬ born,

a control device (12) for controlling the generation of shear wave probe, the probe me ^¬ sour and the extensometer, the control device being adapted to perform successive measurements of said para ^¬ meter spread of shear wave in the measurement zone, and to apply dif stretching ^¬ ent to the skin by one extensometer (3, 4, Ml)

characterization means (3) adapted to store first and second sets of measurements cor ^¬ corresponding respectively to first and second different propagation ^direc¬ tions (X, Y) ci ^¬ winding waves, each of the first and second sets me ^¬ sour comprising at least propa parameter values ^¬ gation for different stretching, said means for charac- térisation (3) being adapted to determine a reference for stretching said propagation parameter which is identical in the first and second directions ^¬ pagation of (X, Y), and determining the natural tension of the skin as a stretching stress in the corre sponding to said skin ^¬ reference stretch value.

2. Device according to claim 1, comprising means (M2, M3) for moving the shear wave generating probe (7) and the measuring probe (8) fa ^¬ CON align successively in the first and deu ^¬ xth propagation directions (X, Y).

3. Device according to claim 1, having first and second pairs of probes (7, 8, 7a, 8a), each comprising a wave generating probe will ^¬ saillement (7, 7a) and a measuring probe ( 8, 8a) échogra- phic, the first pair (7, 8) of sensors being aligned in the first direction of propagation (X) and deu ^¬ xth pair (7a, 8a) of probes being aligned in the direction of deu- xth of propagation (Y),

the control means being adapted to perform the first set of measurements by the first pair and the second set of measurements by the second pair.

4. Device according to any one of claims 1 to 3, wherein the extensometer comprises a force sensor (13) adapted to measure a stretching force ap ^¬ plied to the skin for each stretching value,

the control means (12) being adapted to store a value representative of said stretching force to each stretch value and to determine the voltage ^¬ na tural skin by a predetermined relationship from said corresponding stretching force at the reference stretch.

5. A method of characterizing the skin with the aid of a device according to any one of the preceding claims, comprising a measuring step during ^¬ which is propagated shear waves in a measurement zone belonging to the skin (P) of a mammal while subjecting the skin, in the measurement zone, to different sequential stretching in a stretching direction (D) constant, said waves are sensed ci ^¬ saillement after propagation and is determined from the sensed waves, values of at least one propagation parameter of the wave shear in the measurement zone according to the stretch,

the method further comprising at least one step of charac- térisation during which it is determined, based on said values ^¬ propagation parameter, a natural voltage value of the skin,

characterized in that the measuring step, the shear wave is made propagate respectively in different first and second directions (X, Y) substantially pa ^¬ rallèles to the skin (P) and said determining at least one parameter propagating in each of said first and second directions (X, Y) at different stretching values,

and in that the characterization step, one determines a reference for stretching said propagation parameter which is same in the first and second propagation ^¬ direc tions and skin natural voltage determining (C0) as a stretching constraint in the skin corresponding to said reference stretch.

6. The method as claimed in claim 5, wherein the propagation parameter measured during the ^measurement step is representative of a propagation speed in the skin (P).

7. The method of claim 5 or revendi ^¬ cation 6, wherein during the measuring step, it gen- erates the shear wave from a surface of OUTSIDE ^¬ higher skin (P) and said parameter is measured from said outer surface by ultrasound.

8. Process according to any one of revendica ^¬ tions 5 to 7, wherein during the measuring step, one causes the shear waves to be generated by a shear wave ge ^neration probe (7) applied against the outer surface of the skin (P) and said propagation param ^¬ meter is measured using an echo graphing probe. (8) applied against said outer surface, and said successive stretching is imposed on said outer surface,

and in said measuring step, there is the shear wave generating probe (7) and the measuring probe (8) aligned in succession in the first and deu ^¬ xth propagation directions (X, Y) .

9. A method according to any one of revendica ^¬ tions 5 to 7, wherein during the measuring step, is used first and second pairs of probes (7, 8, 7a, 8a) applied to the outer surface of the skin (P), each comprising a shear wave generation probe (7, 7a) and an ultrasound measurement probe (8, 8a), the first pair of probes (7, 8) being aligned in the first direction of propagation (X) and the xth deu- probe pair (7a, 8a) being aligned in the xth deu ^¬ propagation direction (Y),

is made generating first shear waves by shear wave generating sensor (7) of the pre ^¬ Mière pair and measuring said propagation parameter to said first shear wave using the measuring probe (8) the first pair,

is made generating second shear waves by shear wave generating sensor (7a) of the xth deu ^¬ pair and measuring said propagation parameter to said second shear wave using the measuring probe (8a) the second pair.

10. A method according to any CLAIMS ^¬ tions 5 to 9, wherein the first and second propagation ^¬ direc tions (X, Y) are substantially at right between them.

11. A method according to any CLAIMS ^¬ tions 5 to 10, wherein the first direction of propaga ^¬ (X) is substantially parallel to the stretching direction (D).

12. A method according to any one of revendica ^¬ tions 5 to 11, wherein during the measuring step, measuring a stretching force applied to the skin for each stretching value and the natural tension of the skin is calculated by a predetermined relationship from said stretching force.