EP0610434A1

EP0610434A1 - Method for reducing damage to and lesions of surfaces in the propagation field of high-energy pressure waves, using an agent for reducing bubble formation caused by the pressure waves, and pressure wave generating device for implementing said method

Info

Publication number: EP0610434A1
Application number: EP92924746A
Authority: EP
Inventors: Chantal Delon-Martin; Dominique Cathignol; Jean-Yves Chapelon; Emmanuel Blanc
Original assignee: Institut National de la Sante et de la Recherche Medicale INSERM; Technomed Medical Systems SA; Technomed International SA
Current assignee: Institut National de la Sante et de la Recherche Medicale INSERM; Technomed Medical Systems SA
Priority date: 1991-10-31
Filing date: 1992-10-28
Publication date: 1994-08-17
Also published as: WO1993008749A1

Abstract

L'invention concerne un procédé de réduction des phénomènes de destructions ou de lésions à l'interface de deux milieux, liquide ou solide, en particulier à l'interface d'un milieu liquide et d'un tissu d'un être vivant, ou interface d'un milieu liquide et d'un milieu solide en particulier une membrane, ou encore à l'interface d'un milieu solide en particulier une membrane et d'un tissu d'un être vivant, ainsi qu'un appareil en comportant application. L'appareil comprend un dispositif générateur d'ondes de pression (12) équipé d'une membrane (16) définissant une cavité remplie complètement d'un liquide de couplage (18). Selon l'invention, la surface interne (19) et externe (20) de la membrane (16) est enduite ou recouverte d'un agent (24) réduisant les destructions ou lésions à l'interface, de préférence constitué par une huile silicone. L'invention trouve application dans les appareils de génération d'ondes de pression permettant de réaliser des traitements extracorporels sans phénomène de destruction ou de lésion associé, même à la plus grande puissance.The invention relates to a method for reducing the phenomena of destruction or damage at the interface of two media, liquid or solid, in particular at the interface of a liquid medium and a tissue of a living being, or interface of a liquid medium and a solid medium, in particular a membrane, or even at the interface of a solid medium, in particular a membrane, and a tissue of a living being, as well as an apparatus comprising it application. The apparatus comprises a pressure wave generator device (12) equipped with a membrane (16) defining a cavity completely filled with a coupling liquid (18). According to the invention, the internal (19) and external (20) surface of the membrane (16) is coated or covered with an agent (24) reducing the destruction or lesions at the interface, preferably consisting of a silicone oil . The invention finds application in devices for generating pressure waves making it possible to carry out extracorporeal treatments without the phenomenon of destruction or associated lesion, even at the highest power.

Description

05 generating pressure waves with application

The present invention essentially relates to a process for reducing the phenomena of destruction or damage to surfaces located in the field of propagation of power pressure waves, by the use of an agent which reduces the formation of bubbles created by pressure waves, and apparatus for generating pressure waves with application.

It is known that bubbles are generated by power pressure waves used to perform therapy. This is for example the case of pressure waves generated by shock waves such as those used in lithotripsy, as well as pressure waves generated by focused ultrasonic waves. These bubbles thus generated are then imploded by pressure waves subsequently emitted. All of these phenomena are often commonly referred to as cavitation phenomena.

This phenomenon of generation of gas bubbles leads to destruction or damage to the surfaces located in the field of propagation of the pressure waves, which is unacceptable in the case of a therapy where such surfaces are generally formed by the patient's skin. The creation of bubbles and their implosion is all the stronger the higher the pressure. Now, a high pressure is necessary for the pressure wave to be effective and in particular to induce a rapid rise in temperature of the tissues to reach an efficiency threshold itself dependent on * 30 The pressure. Therefore, the phenomenon of genera-

* ^" tion of bubbles on the surfaces located in the field of propagation of the pressure waves and in particular of the tissue-liquid coupling interfaces when it is desired to treat in depth the tissues by power pressure waves, such as by example The focused pressure waves, whether shock waves or ultrasonic waves.

It has already been proposed to limit the presence of gas bubbles by using degassed coupling water by vacuum treatment, recycling being carried out continuously (see EP-A-0 090 138).

On the other hand, it has also been proposed by document EP-A-0226041 a method and a device for coupling a membrane to the skin of the human body by means of a bag filled with a gel which can be inserted or removed from the bag through longitudinal holes in the direction of a gel reserve. Likewise, document EP-A-0229 241 cites the use of a gel between the body and the membrane, in combination with a device for removing air bubbles by mechanical means of the wiper type.

However, it appears that the use of a gel does not make it possible to effectively eliminate cavitation phenomena and that this solution cannot be used in practice, in particular in the context of treatment by thermotherapy where the waves of pressures are of relatively long duration, that is to say of a duration greater than the microsecond.

Again, it is known from document US-A-4886 068 KANEK0 an ultrasonic coupling agent of low viscosity using a silicone-based oil which is essentially soluble in the aqueous solution, in order to avoid imprisonment ¬ ment of air bubbles between the surface of the probe and the patient's skin, while the diagnostic probe is in the air.

However, in the context of thermotherapy treatment, the pressure waves are generated in a coupling liquid, this coupling liquid being in contact with the patient's skin, so that the accidental presence of air bubbles between the coupling and the patient's skin does not constitute a real problem, due in particular to the fact that they are evacuated naturally. However, the major problem lies in the creation of gas bubbles resulting from the cavitation phenomena inherent in the transmission of high power ultrasonic pressure waves, this cavitation phenomenon being nonexistent in ultrasonic diagnostic probes.

This cavitation phenomenon is particularly aggravated in the context of thermotherapy treatment where the pressure waves are of relatively long duration, that is to say of a duration greater than the microsecond.

Consequently, the main object of the present invention is to solve the new technical problem consisting in providing a solution making it possible to reduce the phenomena of destruction or damage to surfaces located in the field of propagation of pressure waves of power, thereby making it possible to make more effective the use of focused pressure wave for therapeutic purposes, preferably by thermotherapy, in particular the use of focused power ultrasound; or focused shock waves such as in lithotripsy, treatment of tumors or bones.

The main object of the present invention is also to solve the new technical problem consisting in providing a solution making it possible to increase the power of pressure waves, in particular ultrasonic pressure waves, without any significant phenomenon of bubble creation. by power pressure waves, unlike previous solutions.

The object of the present invention is to solve these technical problems in a simple, inexpensive manner which can be used on an industrial scale, making it possible to carry out therapeutic treatments under excellent conditions of efficiency and safety for the patient.

The present invention makes it possible for the first time to solve the above-mentioned technical problems in a simultaneous, simple, inexpensive manner and therefore usable on an industrial and medical scale.

Thus, according to a first aspect, the present invention provides a method for reducing the phenomena of destruction or damage at the interface of two media, liquid or solid, in particular at the interface of a liquid medium and a fabric of a being living, especially a human being; or at the interface of a liquid medium and a solid medium, in particular a membrane, or even at the interface of a solid medium, in particular a membrane, and of a tissue of a living being, said interface being traversed by power pressure waves, characterized in that at least one of said interfaces is applied an agent reducing the destruction or damage to said interface. Preferably, this agent reduces the formation of bubbles by cavitation.

According to an advantageous embodiment, this agent reducing destruction or damage comprises a silicon oil. Advantageously, this silicone oil is essentially insoluble in water.

According to another advantageous embodiment, this agent reducing destruction or damage is applied in the form of a substantially continuous coating on said interface where the phenomenon of cavitation is likely to occur, in particular on the area of the skin of a being. living, in particular a human being, crossed by pressure waves for the treatment of a target inside the body. This target can be a concretion, a tumor tissue or a bone to be treated.

According to another advantageous embodiment, the agent reducing destruction or damage is applied in the form of a substantially continuous coating on the internal and external surfaces of a membrane containing a liquid used for coupling pressure waves, in particular focused, for the treatment of a target inside the body of a living being, in particular a human being.

According to another advantageous characteristic, the aforementioned silicone oil is used in an essentially pure state. We prefer to use a silicone oil with a very low

_2 vapor pressure, typically around 10 millibars at o

200 C and / or which has a low surface tension, typically 20 millinewtons per meter, and / or a high compressibility. It is preferred that this oil has a viscosity of the order of 100 centipoise. It is possible, for example, to use a silicone oil in the pure state marketed by the Rhône-Poulenc company under the RH0D0RSIL Q> brand - type 47V and more particularly type 47V100.

According to another particular embodiment, this agent for reducing destruction or damage comprises a silicone oil in the excipient state at a concentration of at least 50%. Advantageously, a product containing at least 50% of silicone oil is a cosmetic or pharmaceutical product, such as a moisturizing or sun cream. Such products are well known to those skilled in the art. According to a second aspect, the present invention also covers an apparatus for generating therapy pressure waves, comprising a device generating pressure waves, comprising a focusing cavity completely filled with a cou¬ liquid, characterized in that that it comprises means for coating or covering at least partially with a substantially continuous layer, at least the interface zone traversed by said pressure waves, of a tissue of a living being, such as the skin , in contact with the coupling liquid, with an agent which reduces destruction or damage. According to a third aspect, the present invention also covers an apparatus for generating pressure waves, comprising a device generating pressure waves having a cavity closed in a substantially sealed manner by a membrane, said cavity being completely filled with a liquid. coupling, characterized in that the external surface and / or the internal surface of said membrane is coated or covered at least partially with a substantially continuous layer of a reducing agent. destruction or damage of a tissue of a living being in contact with the membrane and / or of the membrane, with an agent reducing the destruction or damage, at least in the area traversed by said pressure waves.

According to a preferred embodiment, this agent reducing destruction or damage comprises a silicone oil. Preferably, this silicone oil is essentially insoluble in water.

According to another advantageous characteristic, the oil The aforementioned silicone is used in an essentially pure state. We prefer to use a silicone oil with a very low

-2 vapor pressure, typically of the order of 10 millibars a o

200 C and / or which has a low surface tension, typically 20 milline tons per meter, and / or a high compressibility. It is preferred that this oil has a viscosity of the order of 100 ceπtipoises. It is possible, for example, to use a silicone oil in the pure state marketed by the company Rhône-Poulenc under the brand RHODORSIL, type 47V and more particularly type 47V100.

According to another particular embodiment, the agent reducing destruction or damage comprises a silicone oil in the excipient state at a concentration of at least 50%, for example in the form of a cosmetic or pharmaceutical product, such than a moisturizer or sunscreen.

According to a particular embodiment, the pressure wave generator device is a generator device of the ultrasonic type, in particular focused. This ultrasonic generator device can comprise at least one piezoelectric transducer element of spherical shape, achieving natural focusing or a piezoelectric transducer element of any shape focusing the pressure waves by electronic means.

Preferably, this device is an extracorporeal treatment device for a target inside the body of a living being, in particular a human being, such as a concretion, a benign or tumor tissue or a bone to be treated.

Thanks to the invention, unexpectedly reduces the burning phenomena of the skin which receives the pressure waves transmitted by the coupling liquid, burning phenomena which are particularly traumatic for the patient and for which no satisfactory solution exists. 'was previously proposed. Also, the phenomena of destruction or damage to the coupling membrane are avoided or reduced. The elimination of the cavitation phenomenon is demonstrated by the following example given by way of illustration which does not therefore in no way limit the scope of the invention.

In the drawings:

FIG. 1 schematically represents a partial section of a pressure wave generating apparatus comprising a pressure wave generating device closed by a membrane, the internal surface and the external surface of which are here covered with a silicone oil , as will be explained in detail using the following example; and figure 2 represents a curve representing

2 the intensity of the pressure field in / cm on the y-axis as a function of the electric intensity sent to the piezoelectric transducer element of spherical shape defining a geometric center or focal point F, to which the emitted ultrasonic waves are focused, from device object of FIG. 1. Curve 1 with the squares is obtained with the use of a liquid coupling medium such as degassed tap water without agent reducing the destruction or damage of the tissues of a living being in contact with the coupling liquid (comparative curve), while curve 2 connecting the points is obtained with the same coupling liquid, but the membrane has its internal and external faces coated or covered with a substantially continuous layer of an agent reducing the destruction or damage to tissues of a living being, for example the skin, here the essentially pure silicone oil constituted by the silicone oil available commercially this under the trade name RHODORSIL. ^ de Rhône-Poulenc, type 47V100.

This curve is explained in more detail with reference to the following example.

Example

In Figure 1, there is shown a pressure wave generating device represented by the general reference number 10. This pressure wave generating device more particularly comprises a pressure wave generating device referenced 12 comprising preferably at least one piezoelectric transducer element 14, here in the form of a spherical cap achieving natural focusing at a focal point F. This generator device 12 is also equipped with an elastic membrane 16 characterized by its acoustic transparency, such as a mem¬ brane made of latex or silicone. The cavity defined inside the membrane 16 and the spherical cap 14 is completely filled with a coupling liquid 18, such as advantageously dega¬ zed water, as is well known to those skilled in the art. 'art.

According to the invention, the internal face 19 and the external face 20, at least on the zone intended to come into contact with the skin 22 of a patient P, are coated or covered with a substantially continuous layer of a agent 24 reducing the destruction or damage of the interface tissues in contact with the membrane here the skin 22 of the patient P as well as of the membrane with the coupling liquid, consisting of a silicone oil, for example available silicone oil commercially under the trade name RH0D0RSIL ^R from Rhône-Poulenc, type 47V100.

With such a device, a progressive electric intensity is sent to the transducer element 14 and the pressure wave pressure is measured at the focal zone F. This experiment is carried out first of all without coating the internal or external surfaces of the membrane 16, to serve as a comparison and the results obtained are reported in FIG. 2 in curve 1.

The curves in Figure 2 give the ordinate the intensity

2 site at the focal point expressed in / cm as a function of the supply voltage of the transducer element 16, this voltage being squared to obtain direct proportionality with the

2 tensite, expressed in mV.

On the other hand, the experiment is carried out with the device according to the invention as shown in FIG. 1 and comprising an internal and external layer of silicone oil on the membrane and the curve 2 in FIG. 2 is obtained. .

It can thus be seen that the pressure field passing through the membrane coated with silicone oil (curve 2 according to the invention) is greater than that crossing the untreated membrane (curve 1, prior art). Also with the coated membrane of silicone oil, the pressure collected remains approximately linearly much longer as a function of the electrical intensity sent to the transducer element, thus indicating the absence of cavitation for higher pressures, while, in the case of a membrane not coated with an agent according to the invention (curve 1, prior art), a non-linear effect is observed very early resulting from a phenomenon of cavitation.

During in vivo tests, it has thus been found that, in the absence of the use of a silicone oil on the internal and / or external face of the membrane, burns are obtained on the patient's skin, while that, with the use of a silicone oil in accordance with the invention, no phenomenon of burning of the patient's skin could be observed, which constitutes a particularly unexpected result. It is thus understood that the invention makes it possible to solve the technical problems previously stated and to significantly reduce the phenomena of destruction or damage to the tissues in contact with the coupling liquid or with a membrane interposed between the patient's skin and the liquid. coupling, which also makes it possible to use higher power pressure waves, in particular higher power focused ultrasonic waves. This makes it possible to effectively carry out an extracorporeal treatment in the case of therapeutic treatment. It is known that pressure wave generating devices can be used for the extracorporeal treatment of concretions, tumors, bone areas, in particular fractures (osteotritis), the area to be treated being placed in coincidence with the focal area of the device generating focused pressure waves, it also delays the destruction or lesion of the membrane.

Naturally, the invention includes all the means constituting technical equivalents of the means described as well as their various combinations.

Claims

1. Method for reducing the phenomena of destruction or damage at the interface of two media, liquid or solid, in particular at the interface of a liquid medium and a tissue of a living being, in particular a being human ; or at the interface of a liquid medium and a solid medium, in particular a membrane, or even at the interface of a solid medium, in particular a membrane and of a tissue of a living being, said interface being traversed by power pressure waves, characterized in that at least one of said interfaces is applied an agent reducing the destruction or damage to said interface.

2. Method according to claim 1, characterized in that the aforementioned agent comprises a silicone oil, in particular a silicone oil insoluble in water.

3. Method according to claim 2, characterized in that the silicone oil has a very low vapor pressure,

-2 ° typically of the order of 10 millibars at 200 ° C., and / or a low surface tension typically of 20 millinewtoπs per meter, and / or a high compressibility, and / or a viscosity of the order of

100 centipoises.

4. Method according to claim 2, characterized in that the aforementioned agent comprises at least 50% of silicone oil, for example comprises a cosmetic or pharmaceutical product containing at least 50% of silicone oil, for example a moisturizer or solar.

5. Method according to one of the preceding claims, characterized in that the aforementioned agent is deposited on the internal and / or external face of a membrane enclosing a coupling liquid of acoustic pressure waves.

6. Method according to claim 5, characterized in that the membrane is mounted on a device for generating pressure waves, in particular focused, for the treatment of a target inside the body of a living being, in particular of a human being, such as a concretion, a tumor tissue or a bone to be treated.

7. Therapy pressure wave generation apparatus, comprising a therapy pressure wave generating device, a coupling liquid coupling said therapy pressure waves, with a tissue of a living being, in particular a human being, characterized in that it comprises means for coating or covering at least partially with a substantially continuous layer, at least the interface zone traversed by said therapy pressure waves, with an agent reducing destruction or damage.

8. Apparatus according to claim 7, characterized in that it comprises a membrane transparent to pressure waves, interposed between the coupling liquid and the fabric, the aforementioned means for coating or covering also being used for coating or covering the internal surface and / or external of said membrane.

9. Apparatus according to claim 7 or 8, characterized in that the aforementioned agent comprises a silicone oil, in particu¬ bind a silicone oil insoluble in water.

10. Apparatus according to claim 9, characterized in that the aforementioned agent consists of a silicone oil having a very low vapor pressure, typically of

-2 ° the order of 10 millibars at 200 C, and / or a typical low tension of 20 millinewtons per meter, and a high compressibility, and / or a viscosity of the order of 100 centipoise.

11. Apparatus according to claim 8 or 9, characterized in that the aforementioned agent comprises at least 50% silicone oil, in particular comprises a cosmetic or pharmaceutical product containing at least 50% silicone oil, such as a moisturizer or sunscreen.

12. Apparatus according to one of claims 7 to 11, characterized in that the pressure wave generator device is a generator device of the ultrasonic type, in particular focused, for example by having a spherical cap shape.

13. Apparatus according to one of claims 7 to 12, characterized in that it is an extracorporeal treatment apparatus of a target inside the body of a living being, in particular a human being, such as a concretion, a fabric ^• cumo- rai or bone to treat.