FR2689760A1 - Device for generating pressure waves with a very flexible flat membrane and treatment apparatus comprising such a device. - Google Patents

Abstract

Pressure wave generating device comprising a membrane (18). The device is characterized in that the highly flexible flat membrane is inflatable at very low pressure. The membrane is simple to make and inexpensive while facilitating treatment.

Description

Device for generating pressure waves with a very flexible flat membrane and treatment apparatus comprising such a device
The present invention essentially relates to a device for generating pressure waves with a very flexible flat membrane and a treatment apparatus comprising such a device.

 There are already known, for example from document EP-A-0 226 041, devices generating pressure waves comprising membranes, in particular with a particularly complex bellows structure.

 The proposed membranes are for the most part thick and have the main disadvantage of being difficult to produce industrially by requiring complex moldings and of not allowing flush treatment of the generator and therefore of limiting the depth of treatment while requiring high pressures. to inflate them which creates a significant force on the patient's skin and results in a systematic displacement of the patient while then shifting the position of the target to be treated.

 The object of the present invention is therefore to solve the new technical problem consisting in providing a solution allowing the use of a membrane which is easy to produce industrially, allowing treatment at the level of the generator and thus not limiting the depth of treatment. and on the other hand requiring only a very low inflation pressure so as not to push or move the patient during inflation.

 This technical problem is solved for the first time by the present invention in a particularly simple, reliable, inexpensive manner, usable on an industrial and medical scale.

 Thus, according to a first aspect, the present invention provides a pressure wave generating device comprising a focusing curved active surface defining a cavity filled with an acoustic coupling medium, in particular a liquid medium, sealed by a membrane. , characterized in that said membrane, at least on the opposite part of said cavity, is flat and very flexible.

 According to a particularly advantageous embodiment, this membrane is made of a thin elastomeric material having a high coefficient of elongation and a low hardness, this membrane thus having very great flexibility and requiring only a very low inflation pressure .

 Preferably, the elongation coefficient of the membrane is greater than 400% and even better still 500% and even better still 600%.

Advantageously, the hardness of the material used to manufacture the membrane is less than 50 Shores A or better still less than 30 * Shores A.

 The thickness of this membrane is preferably of the order of a millimeter, or preferably less than about 1 mm. A particularly preferred thickness is about 0.7mm. This membrane can be made of a silicone elastomer or a latex.

 According to an advantageous alternative embodiment, this membrane has the shape of a substantially circular disc whose lateral edges form an extra thickness to increase the mechanical resistance to tearing at the place of attachment of the membrane to the periphery outside. of the generating device.

 According to a particularly advantageous embodiment, this membrane is mounted on a "cover" type opening / closing device articulated outside the generator device, thus making it possible to hold the membrane in a particularly simple manner, and to close the generator tightly.

 According to a particularly advantageous embodiment, this device also includes means for inflating the membrane with the coupling medium.

 According to a particularly advantageous embodiment, this device comprises a means for purging the air enclosed in the cavity of the device closed by the membrane. Preferably, said membrane substantially comprises in its center a ring for hooking the end of this purge device, such as a purge pipe, in order to allow a particularly simple and automatic evacuation of the air or enclosed gas. in the device cavity or generated in the device cavity. A liquid detection device can be provided in this purge pipe which actuates the solenoid valves to close this pipe, which makes it possible to ensure that there is no more air under the membrane.

 According to a preferred embodiment, the acoustic coupling medium is a liquid such as degassed water or, preferably, an electrically conductive liquid, such as a solution of highly ionized water, as described in the previous application of the Applicant FR-89 08 846.

 According to another particularly advantageous embodiment, the generator device is mounted in rotation about its axis of symmetry.

 According to another particularly advantageous embodiment, this generating device is also equipped with a device forming an imaging probe, preferably of the ultrasound type, mounted outside of it at its periphery. This imaging device is advantageously mounted on a support means allowing a rotational movement around the periphery of the device, by permanently viewing the focus of the generator constituting the focal point of the pressure waves, as described in the previous document of the depositor. FR-88 1414. Thus, this imaging device can also be mounted for rotation about its axis and in translation parallel to its longitudinal axis.

 According to a second aspect, the present invention also provides a processing apparatus, characterized in that it comprises a pressure wave generator device as previously defined. Preferably, this pressure wave generator device comprises a truncated ellipsoidal reflector comprising an internal focal point immersed in the coupling liquid and an external focal point intended to be placed in coincidence with a target to be treated. This treatment device can in particular be a device for treating a target formed by a concretion in the context of lithotripsy, of a benign or malignant tumor, or of a bone in the context of osteothritia.

 It is thus understood that the invention makes it possible to provide all the technical advantages determining previously stated as well as those which will appear clearly to those skilled in the art from the following description.

Other objects, characteristics and advantages of the invention will appear clearly in the light of the explanatory description which will follow made with reference to the appended drawings representing a particularly preferred embodiment of the invention given simply by way of illustration and which therefore cannot in any way limit the scope of the invention. In the drawings:
- Figure 1 shows a cross-sectional view along a plane of symmetry of a pressure wave generator device according to the present invention, schematically;
- Figure 2 shows a sectional view of the flat membrane according to the invention in the undeformed or uninflated state;
- Figure 3 shows a cross-sectional view similar to that of Figure 1 of a pressure wave generator device equipped with a cover type opening / closing device on which is mounted the flat membrane according to invention;
- Figure 4 shows the generator device according to the invention object of Figures 1 to 3 with the membrane in the inflated state, equipped with the device for purging air or gas contained therein;
- Figure 5 shows a schematic external elevation view of the generator device with the membrane in the inflated state, the latter being equipped with an image forming device rotatably mounted externally to the generator at its upper periphery, a patient being schematically represented as well as compression in the kidney, placed in coincidence with the external focus of the generator; and
- Figure 6 shows schematically the circuit for regulating the inflation pressure of the membrane.

 Referring to Figure 1, there is shown the currently preferred embodiment of the pressure wave generator device according to the invention represented by the general reference number 10. This generator device preferably has here a focusing active surface 12 defining a cavity 14 filled with a coupling medium, preferably a liquid such as degassed water, even better an electrically conductive liquid as described in the aforementioned applicant's prior application which is incorporated here by reference. In FIGS. 1 to 6, the pressure wave generating device 10 comprises a truncated ellipsoidal reflector 16 having an internal focus F1 where the pressure waves are emitted, for example by electrical discharge between two immersed electrodes arranged symmetrically with respect to the internal focus F1, which are then focused on the external focus F2.

 This generator device is closed in a sealed manner by a membrane 18 which is shown alone and enlarged in FIG. 2 for a better understanding.

 This membrane is according to the present invention characterized in that it has a flat shape at least on its part for transmitting pressure waves closing the cavity 14. A partially inflated position of the membrane is represented by the reference 18 'and a position fully inflated is shown in position 18 "in Figure 1.

 This membrane is according to the present invention characterized in that it is of flat geometric shape and made of a very flexible material. A particularly preferred material is an elastomer having a high coefficient of elongation, advantageously greater than 400%, better still greater than 500% and more preferably greater than 600%. The hardness of this material is very low, preferably less than 50. Shores A or better still less than 30 * Shores A.

 The thickness of the membrane according to the invention is very small on its active part, this small thickness being small compared to the wavelength of the pressure wave. A preferred thickness is of the order of a millimeter, or better still less than about 1 mm. A particularly preferred thickness is about 0.7 mm. This small thickness, thanks to the fact that it is small compared to the wavelength of the pressure wave, avoids excessive attenuation effects and makes it possible to inflate the membrane with low pressure thanks to its very large flexibility.

 Particularly suitable materials are elastomers such as silicone elastomers or latex elastomers, which are well known to those skilled in the art.

 Naturally, it is advantageous for the interior and exterior surface condition of the membrane at the level of contact with the patient to be particularly smooth, in order to avoid the presence of air bubbles which obstruct the propagation of shock waves. A coupling gel can be used between the membrane and the patient.

 With reference to FIG. 2, it can be observed that this membrane 18 has a small thickness on its active central part for transmitting pressure waves 18a and a greater thickness with a peripheral bead 19 to increase its resistance when it is joined to the pressure wave generator 10, in particular to allow mounting in an opening / closing device 20 visible in FIG. 3. This opening / closing device 20 has a hinge 22 mounted outside the generating device 10 to allow the sealed opening or closing of the cavity 14 with the membrane 18, a locking device 24, 26 for example by clipping being provided on the opposite side of the generator as clearly visible in FIG. 3. L sealing is advantageously done by compressing the membrane 18 between the support device 20 and the upper peripheral edge 17 of the reflector 16 as is well understandable for a person skilled in the art. The membrane already has an extra thickness at this level as can be understood from the consideration of FIG. 2.

 On the other hand, according to an advantageous embodiment, the membrane 18 comprises substantially in its center a device 30 for hooking a purge means to purge the air trapped in the cavity closed by the membrane, such as a purge pipe, for example in the form of a ring 32 forming a body with the membrane 18 or attached under this membrane after manufacture.

 FIG. 4 shows the membrane 18 in the inflated state with the attachment means 30 and the purge means 34, such as a purge pipe which terminates outside the reflector 16 by passing through it. a passage orifice 36. A closure means such as a solenoid valve 38 can be provided on this drain pipe, as well as a reservoir 40 equipped with a liquid level detection means, such as a float or any liquid level detection device well known to those skilled in the art.

 Referring to Figure 5, there is shown the generator device 10 which is advantageously rotatably mounted on a rotation control device 40 such as a rotary drum well known to those skilled in the art. This rotary drum is also mounted on a displacement device in any position of the space in the directions X, Y, Z as described in the previous patent of the applicant US-A-4,915,094 which is incorporated here by reference.

 This pressure wave generator device 10 is advantageously also equipped with an image forming device 50, for example formed by an ultrasound probe, mounted on a support device 52 optionally displaceable in rotation on displacement means 54 or fixed at the outer periphery of the upper edge of the generator 10. This image-forming device 50 is movable according to 3 degrees of freedom, in rotation about the axis passing through the two focal points of the reflector 10 thanks to the rotation device 40, thus that in rotation about its longitudinal axis and in translation around its longitudinal axis 56, as described in the previous document of the applicant FR-88 1114 incorporated here by reference. This image-forming device has its axial direction 56 which permanently targets the second focus F2 of the generator device 10 in order to permanently observe the target area C, such as a concretion inside the kidney R of a patient P .

 Referring to Figure 6, there is shown the principle diagram of circulation of the coupling fluid such as a liquid, for example degassed water. It is observed that the coupling fluid is, for example, stored in a storage tank 60 comprising a pipe 62 for supplying coupling fluid such as degassed water and a pipe 64 for degassing under vacuum. A conduit 66 is provided for bringing the coupling fluid through the pumping device 68 into the cavity 14 of the generator device 10 to inflate the membrane 18, as shown, so that the air possibly trapped in the volume defined by the membrane 18 and the cavity 14 is evacuated by the purge means 34. In order to inflate the membrane 18, an accumulator device 70 can be provided, filled with coupling fluid which is introduced or expelled by the use of a compressor 72 compressing a gas such as air 74 from the atmosphere, and comprising for example a pressure regulating device 76.

 Since the membrane 18 according to the present invention is flat and of great flexibility, it can therefore be inflated to a very low pressure usually and preferably less than about 100 mbar, con-sign pressure which is given by the regulating device 76.

It should be noted that there is no separating membrane between the gas such as air and the coupling liquid such as water contained in the accumulator device 70, which makes it possible to obtain pressures of very precise regulation and especially no inertia in the regulation. This parameter is very important since when the membrane 18 inflates, we especially want to avoid moving the patient, which means that as soon as the set pressure, such as for example 100 mbar, is obtained by means of the pressure reducing device 76, we require that the membrane stops swelling and therefore the regulation takes place immediately, either because of contact of the membrane with the patient's skin, or because of an excessive deformation of the membrane. This characteristic is therefore obtained by the direct gas interface such as air / coupling liquid such as water in the accumulator device 70.

 It is understood that with the present invention, the membrane can be manufactured very easily on an industrial scale at a lower cost, which will to some extent allow the membrane to be considered as a consumable object for hygienic reasons since it is in contact with the patient's skin. It is also possible to treat patients who are obese or who have a target, such as a very deep calculation, flush with the reflector. This also reduces the size of the lithotripter due to the use of a flat membrane, which also makes it possible to pass a linear detector for example of X-rays above the generator device, when another geometry would not allow it.

 It is also easier to change the electrodes of the pressure wave generator thanks to the very simple and very rapid opening / closing device while maintaining perfect tightness, in particular by compression of the membrane 18 between the opening support device / closure 20 and the upper edge 17 of the device.

The operation of the treatment apparatus according to the invention comprising the pressure wave generating device according to the invention is immediately apparent to those skilled in the art. The main phases are as follows:
The cavity 14 of the reflector 16 is filled by sending air through the compressor device 72 into the accumulator device 70, which has the effect of inflating the membrane and the air which is trapped under the membrane 18 and purged by the purge means 34.

As soon as the air purge is complete, by detecting the presence of liquid in the reservoir 40, the solenoid valve 38 is actuated which stops the flow of the coupling liquid. The air pressure is supplied by the compressor 72 and the set pressure is fixed by the regulator 76. This set pressure is preferably approximately equal to 100 mbar. This set pressure allows the membrane 18 to swell until it meets the skin of the patient P. At this time, the pressure on the membrane 18 increases and the pressure reducing device 76 eventually releases a sufficient volume of air to keep the inflation pressure 18 of the constant membrane; a particularly simple regulatory system is thus obtained.

 The drain for decommissioning is ensured by the main pumping device 68 as well as a set of solenoid valves not shown in FIG. 6 since these systems are well known to those skilled in the art.

 It is thus understood that the invention makes it possible to achieve all the determining technical advantages previously stated.

 On the other hand, Figures 1 to 6 are an integral part of the invention and therefore of the present description. The invention also covers any characteristic which will appear new from the previous description including Figures 1 to 6, vis-à-vis any prior art.

Claims (10)

 1. Pressure wave generator device comprising an active surface (12) focusing in a focus (F2) defining a cavity (14) filled with a coupling medium, such as a liquid, closed by a membrane (18) , characterized in that said membrane is flat and very flexible.  2. Device according to claim 1, characterized in that the membrane (18) has an elongation coefficient greater than 400%, better still greater than 500% and even better still greater than 600%.  3. Device according to claim 1 or 2, characterized in that the membrane (18) has a low hardness, its hardness is preferably less than 500 Shores A or better still less than 30 Shores A.  4. Device according to one of claims 1 to 3, characterized in that the membrane (18) has a small thickness, advantageously small compared to the wavelength of the pressure wave, this thickness preferably being the order of a millimeter or less than a millimeter.  5. Device according to one of claims 1 to 4, characterized in that the aforementioned membrane is made of an elastomer, in particular a silicone or latex elastomer.  6. Device according to one of claims 1 to 5, characterized in that the membrane (18) has substantially in its center an attachment means (30) of a purge means (34) to purge the trapped air in the cavity closed by the membrane.  7. Device according to one of claims 1 to 6, characterized in that it comprises means (60 to 76) for inflating the membrane (18) with the coupling medium, such as a liquid as well as means for regulating the inflation pressure (76) to a set pressure value, which is preferably less than about 100 mbar.  8. Device according to one of the preceding claims, characterized in that the membrane (18) is mounted on a device (20) for opening / closing of the hinged cover type (at 22) outside the device (10).  9. Treatment apparatus, characterized in that it comprises a pressure wave generating device (10) as defined in any one of the preceding claims.  10. Treatment apparatus according to claim 9, characterized in that the pressure wave generator device comprises a truncated ellipsoidal reflector (16) comprising an internal focus (F1) and an external focus (F2).