WO2022023968A1

WO2022023968A1 - A medical device with ultrasonic waves emission

Info

Publication number: WO2022023968A1
Application number: PCT/IB2021/056797
Authority: WO
Inventors: Enrico FERMI; Enrico Pasquino
Original assignee: Opconsulting S.R.L.; Myra Medical S.à.r.l.
Priority date: 2020-07-28
Filing date: 2021-07-27
Publication date: 2022-02-03
Also published as: IT202000018322A1

Abstract

The invention relates to a medical device (1) for treating occlusive vascular lesions, such as calcified atherosclerotic plaques or blood clots present in the lumen of the blood vessels, the device comprising two ablation units (10, 20) that emit ultrasonic waves at frequencies of the order of a few MHz and slightly different from one another, where the first ablation unit (10) is mounted on a vascular catheter (3) and the second external ablation unit (20) is housed in a handpiece or in a plate to be positioned on the outside of the body, i.e., on the skin, at the area of the occluded vessel.

Description

TITLE

“A MEDICAL DEVICE WITH ULTRASONIC WAVES EMISSION”

DESCRIPTION

The present invention relates to an ultrasonic wave emission device for treating chronic occlusive vascular lesions of the coronary and peripheral vessels to restore vascular patency. In particular, the present invention concerns a device provided with several components that emit ultrasonic waves at single frequencies, for treating calcified plaques present in vascular walls. More in particular, the device is provided with at least two ultrasonic wave emitter components, positioned one in a blood vessel and the other one on the outside of the body, on the skin of the patient.

The ultrasonic emission device according to the present invention is, in particular, usable in mini-invasive vascular surgical procedures, for treatment for the recanalization of blood vessels combined with break up of calcified deposits present in atherosclerotic plaques of arterial vessels with chronic total occlusion. These deposits can form in the tunica intima and in the tunica media of the arterial vessels.

The importance of reduction, or even total ablation, of these deposits lies in preventing the onset or reducing the worsening of circulatory diseases, due to progressive stenosis, i.e., to the progressive reduction in blood flow caused by calcifications, so as to prevent potential dramatic events such as strokes, heart attacks, kidney failure and peripheral ischemic diseases.

It is known that calcifications can form in atherosclerotic plaques present in the tunica intima (inner layer) or tunica media (middle layer) of arterial blood vessels. Atherosclerotic calcifications of the tunica media of arterial vessels, for example, are often associated with kidney diseases, diabetes, hypertension and old age, while those affecting the tunica intima are more often associated with thrombotic occlusion of the arteries and, therefore, with strokes, peripheral ischemic diseases, etc. In the human body, calcification is in actual fact part of a dystrophic disease and of aging. Calcifications form in the vessels, in the heart or in the valves, due to the presence of Calcium and Phosphorus ions present in the blood stream that tend to give rise to ossification processes with the formation of aggregations of hydroxyapatite crystals.

Ultrasonic wave emitting devices have already been used for some time for therapeutic procedures of similar diseases, such as in the treatment of treating kidney stones that can be eliminated via lithotripsy, which allows the stones in kidneys to be broken up and reduced in size. Recently, these ultrasonic devices have also been used in procedures to break up and/or ablate calcified plaques present in the lumen of the blood vessels.

Lithotripsy uses pulsed ultrasonic waves, i.e., a succession of a direct compression positive pulse followed by a negative pulse, with negative recovery voltage, as represented in Fig. 1. This allows the cavitation bubbles to be expanded and rapidly collapsed, generating an effect of disintegration of the calcified deposits.

In general, the ultrasonic waves of said devices produce the desired effect because the waves act on said plaques through an acoustic pressure pulse, or shock wave, i.e., a pulse that strikes the calcified plaque and acts thereon directly as mechanical stress force that causes disintegration of the plaque. A second disintegrating effect is of indirect type and is due to the energy released when the cavitation bubbles that form in the tissue collapse. As shown in Fig. 1, the shock wave has the form of short positive pulse, followed by a negative pressure pulse.

Some of these devices are designed for a treatment of transcatheter type, i.e., with access through an artery, for example, femoral, of said deposits in arterial vessels, such as according to the known shockwave method.

To facilitate unblocking of the vessel combined methods are also known, in particular surgical and pharmacological, which are based on the combination of the administration of drugs and of an ultrasonic transcatheter system for treating acute and chronic thromboses. However, this method has the drawback of using drugs that expose the patient to the risk of potential side effects, at times even serious or fatal.

Moreover, the devices currently used for said treatments have a power such that, generally, the results are only achieved after prolonged treatment times, even of a few hours. Said treatment length is clearly a problem as, for example, using one device for a single patient, this reduces the number of patients that can be treated per day.

Also, it has been noted that said prior art devices cause in the patient a non-negligible increase of the temperature in the part treated; usually, the heat delivered causes thermal damage to the tissue. Said effect is therefore undesirable and, currently, is kept under control through the circulation of a cooling liquid in the ultrasonic emission system. However, this expedient involves a significant complication of the device and a considerable increase in its cost.

Therefore, in the sector there is a need to improve known ultrasonic devices so as to optimize their efficiency with regard to disintegration of calcifications of the vessel wall.

Moreover, it is desirable to reduce the treatment times of these known devices.

Finally, but no less importantly, it is desirable to limit or prevent the formation of damage to the tissues caused by the increase of the temperature of the parts of the device in contact with said tissues.

The Applicant has now developed a new ultrasonic device that can be used in a treatment of atherosclerotic plaques on the inner walls of the blood vessels in conformity with the appended claim 1.

This device produces a noteworthy effect of disintegration of the calcifications following the action of the ultrasonic waves, which are emitted at frequencies that are only slightly different and suitably combined.

The waves are applied through ablation units, generally at least two, of which a first ablation unit is positioned inside the vessel to be treated, in which there is an occlusion caused by the calcified plaque, through a vascular catheter with percutaneous access, and a second ablation unit is positioned on the outside of the body, i.e., on the skin, at the area of the occluded vessel.

To simplify the following description, hereinafter the adjectives “internal” and “external” attributed to the ablation units, to the ultrasonic waves and to the ultrasonic field are used to designate the ablation units that during use of the device are positioned, respectively, one in the vessel and the other on the skin, and consequently the ultrasonic waves and the ultrasonic field emitted by each of said ablation units.

This device has such a high disintegrating effect that it does not require, primarily, a simultaneous administration of drugs; this in itself in many respects offers a clear advantage, both therapeutic (for example no side effects caused by the administration of drugs, failure to adhere to the pharmacological treatment plan) and in regard to costs for the patient.

Moreover, the high disintegrating power reduces both the length of time of each single treatment session and the total number of sessions required to complete the whole treatment cycle, with clear advantages, such as treating a larger number of patients, obtaining clinical results in less time and lower treatment costs.

Finally, the device according to the present invention, which operates with both the ablation units at frequencies of a few MHz, allows the total energy of the waves emitted over a short period of time to be increased without having to use excessively high electric power. This is advantageous as it avoids an excessive increase in temperature in the tissues struck by the waves, which can damage them, and therefore their integrity can be preserved.

As mentioned previously, operation of the device according to the present invention is based on the interaction of the ultrasonic fields emitted by the two different ablation units for the creation of cavitation bubbles and the consequent decalcifying effect. In particular, operation of the device according to the present invention is based, prevalently, on a suitable combination of ultrasonic fields at different frequencies, and this allows, as described in the literature, the effect of cavitation to be strengthened. The result is an increase in the efficiency of the treatment to break up the calcified plaque.

More in particular, the overall disintegrating effect according to the present invention is obtained by using several techniques known per se in the field of ultrasonic waves.

The first technique is the focusing of an ultrasonic wave field coming from ultrasonic transducers housed in said second ablation unit, i.e., the external unit. Focusing conveys the ultrasonic waves on the length of the blood vessel to be treated.

The ultrasonic field emitted by the external ablation unit is focused using the “adjust phase” technique (Fig. 2) in the body volume to be treated, for example a portion of limb or the heart, in the case of treating calcification of coronary arteries. Said external ultrasonic field is combined with the internal ultrasonic field emitted by the first internal ablation unit.

Moreover, the “phased array” technique, known in the ultrasonic field as diagnostic imaging, is used so that the external ultrasonic field is emitted with a certain angle.

In accordance with this technique, the various transduction elements are activated by applying small phase differences to the electric power supply signals, i.e., delays, which generate an interference model the result of which is an angulation of the ultrasonic wave field.

By using two sources with different phases the emission angle θ₁ of the waves is a function of the distance d between the sources and of their phase difference (φ₁-φ₂) and is obtained from the following equation:

Said technique is described in the literature, in particular for imaging applications, for example in a “Practical Guide to Ultrasound Beam Forming: Beam Pattern and Image Reconstruction Analysis”, Applied Sciences, 2018, and therefore will not be further described.

The angle and focus of the field depend on the extent of the progressive delay. Therefore, by modifying this phase difference between the transducers, it is possible to “electronically” orient and focus the ultrasonic field emitted, as represented in Fig. 3. It should be noted that the pulsed signals sent to the transducers do not arrive simultaneously, but with a programmable delay, or phase difference. Said phase difference allows the ultrasonic beam to be focused at the desired distance and with a given angle of refraction.

According to another aspect of the present invention, the device makes use of the phenomenon known with the term “beating”, i.e., the phenomenon that occurs by means of a particular multifrequency combination, i.e., a combination of two fields of ultrasonic waves. In more detail, the phenomenon of beating is generated when at least two fields of ultrasonic waves are combined, each having a given frequency, more precisely the frequencies of the two fields are slightly different from each other. This combination generates an ultrasonic field having a lower frequency with respect to the frequency of the single fields that are combined.

In fact, it is known that when two acoustic pressure waves, with slightly different frequencies, are superimposed, a wave with a new frequency, lower and proportional to the difference between the first two frequencies, is obtained.

If the two waves at the two different frequencies f₁ and f₂ of amplitude A₁ and A₂ are indicated with y₁ and y₂, the two waves can be represented by the following equations (1), (2): y₁ = A₁ sin(2π f₁t) (1) and y₂ = A₂ sin(2π f₂t) (2), said waves once combined, as focused in the same volume, will give rise to the resultant wave represented by the equation (3): y = y₁ + y₂ = A₁ sin (ω₁t) + A₂ sin (ω₂t) (3).

Considering A+A₁ = A₂ and applying the prosthaphaeresis formulae we obtain the equation (4):

The equation (4) corresponds to a new wave, with variable amplitude representable by the equation (5):

The beat effect is evident if y₁ and y₂ have frequencies close to each other (Figs. 3a and 3b). The beat frequency is equal to f_b= |f1-f2| (Fig. 3c).

During the interaction between the waves, the contributions are algebraically summed, so that if the waves are in phase with one another, the maximum value of the amplitude of the resultant wave is obtained. Maintaining the different amplitudes, also in counter phase, the contributions would not be completely cancelled for the term A sin(ω₂t).

Considering now the interaction between waves with different frequency and phases the following equations can be written (6), (7):

If the difference of frequencies f1-f2 is relatively small, the difference of phase is variable in time according to the following equation (8):

If the difference Δ_f = (f₁ — f₂) is much lower than the mean frequency f_media ⁼ , the second factor can be considered a harmonic signal of frequency f_media ,

while the first factor is a signal with amplitude dependent on the time according to the following equation (9):

The amplitude is dependent on the time with the difference of phase between the two signals that increases, in time, according to the following equation (10):

(10) 2πΔd × t + const

Consequently, the interference between the two signals alternates constructive and destructive effects, with a power that varies increasing and then decreasing alternately.

Indicating the powers of the two signals with Pi and P2, the total power is given by the following equation (11): (11)

The contribution given by the interference oscillates at the beat frequency, i.e. f_b= Δf= |f1-f2| wherein the beat frequency represents the frequency with the lowest value.

Therefore, the subject of the present invention is a medical device for treating occlusive vascular lesions comprising the following components:

- a control unit that includes an electrical signal generator;

- a vascular catheter with a radially expansible element;

- a first ablation unit mounted on said expansible catheter, connected to the control unit and housing ultrasonic transducers that receive pulsed electrical signals from the control unit;

- a second ablation unit connected to the control unit and housing ultrasonic transducers receiving pulsed electrical signals from the control unit.

Said transducers of the first ablation unit (hereinafter also called “internal ablation unit”) and said transducers of the second ablation unit (hereinafter also called “external ablation unit”) each emit ultrasonic waves with respective frequencies (f1, f2) comprised between 1 MHz and 3 MHz, preferably comprised between 1.5 MHz and 2.5 MHz. Moreover, the difference between the frequency (f1) of the waves emitted by the first ablation unit and the frequency (f2) of the waves emitted by the second ablation unit is comprised between 30 kHz and 300 KHz, preferably between 30 KHz and 200 KHz, more preferably between 80 KHz and 180 KHz. As explained above, said ultrasonic waves emitted at the first and second frequencies (f1, f2) by the first and second ablation units generate, through the physical phenomenon of beating, ultrasonic waves with a lower frequency (fb) equal to the absolute value of the difference (Δf) between said first and second frequencies (f1, f2). The totality of the waves generated by the transducers and by the phenomenon of beating induce the phenomenon of cavitation in the lumen of the vessel, which allows break up of the calcified plaques.

Unlike known devices in which two frequencies, one high and one low, relatively different from each other are combined to promote cavitation, in the case of the present invention the ultrasonic wave fields destined to be combined to obtain the phenomenon of beating have similar frequencies of the order of a few MHz, with which a generated ultrasonic field having frequency of the order of KHz is obtained. Due to the beat effect thus produced, an even greater increase in the effectiveness of cavitation with the same sound energy is obtained.

Due to the use of two electrical signals with similar frequencies, for the internal and external ablation units respectively, in the order of MHz, it is also possible to use a single electrical signal generator thereby simplifying the control unit of the device.

The use of moderately high frequencies (over one MHz) also allows the use of thin transducers that are particularly suitable for application to the expansible catheter of the internal ablation unit considering the limited radial size that this element must have.

In particular, the device according to the present invention is designed to simultaneously emit ultrasonic waves at two different frequencies and each ablation unit emits waves having a different frequency from the other ablation unit. The device according to the present invention comprises, in addition to said control unit, vascular catheter and ablation units, also a control handpiece. Said components are assembled in the same way in which they are assembled in the aforesaid prior art ultrasonic wave devices for similar uses. Consequently, these components will not be described in detail, unless they differ from the components present in said prior art devices.

In brief, said control unit is electrically connected to the control handpiece, generally by means of one or more electrical cables. This latter control handpiece is connected to a first end of the vascular catheter.

Said control handpiece, like prior art handpieces, comprises an access port for a central guide wire, an access port for a line for inflating the expansible element (balloon) and the mechanical controls for inserting the catheter through the artery and reaching the area to be treated.

The vascular catheter with the radially expansible element is also a prior art device, called vascular balloon catheter. In the present invention, it is a catheter that has said expansible element, of elongated shape, at one end thereof; this end is identified here as free end, to distinguish it from the first end, which is constrained to the control handpiece, and is opposite said free end. This free end carries the first internal ablation unit destined to treat the calcified lesion in the vessel.

The catheter generally has a length of 100 - 150 cm and comprises a lumen for the guide wire, one or more lumens for electrical cables destined to supply the internal ablation unit, a lumen for the inflation line of the balloon and optionally one or two lines (in and out) for conveying a cooling liquid destined to cool said internal ablation unit.

The second external ablation unit is also electrically connected to the control unit by means of one or more electrical cables.

According to the invention, this external ablation unit is housed in an element, for example, in the form of a handpiece or a plate, according to the embodiment of the present invention.

Just like the internal ablation units in similar prior art devices, the internal ablation unit according to the present invention is a probe. This unit comprises transducers to generate ultrasonic waves and, usually and preferably, an insertion tip of the catheter.

Said internal ablation unit has the overall shape of an elongated body, preferably with a circular, typically cylindrical or truncated cone shaped, section.

Said internal ablation unit has a first end closer to the control handpiece and a second end opposite the first end, where said insertion tip is positioned.

A first portion of said internal ablation unit comprises an array of transducers of ultrasonic waves.

The array of transducers has the form of a cylindrical or truncated cone shaped segmented portion. Each segment of said segmented portion is defined here as “transducer unit”. The array of transducers comprises several transducer units, preferably from three to twelve of said units.

The transducer units are fixed to the external surface of the expansible element of the catheter.

According to the embodiment of the present invention, each transducer unit can have one or more of the features listed below, i.e.:

- it has the shape of a solid selected from cylinder and truncated cone;

- it has a central through hole, i.e. along the axis of extension of the cylinder or of the truncated cone;

- it comprises at least two components separated physically from one another, typically from two to six, at least one of which is a transducer for generating ultrasonic waves.

Typically, said two or more components have the same size and shape as one another.

According to a preferred variant of the invention, these components of the transducer unit have a cross section in the shape of a sector of annulus. When the expansible element is in retracted condition, the transducer unit therefore has, as a whole, a cross section in the form of an annulus.

The array of transducers has an arrangement of the transducer units in series. The transducer units are, preferably, all spaced from one another. Typically, the distance between two facing transducer units is, generally, the same for all the pairs of facing transducer units present in the same internal ablation unit.

Generally, two facing transducer units are spaced part by a distance, for example, between 1 mm and 4 mm, which is proportional to the total length of said segmented portion. This latter has a length that varies, normally, from 10 mm to 100 mm.

This spacing is preferable as it gives the catheter on which the internal ablation unit is positioned the flexibility required during positioning of said ablation units in the blood vessel of the patient. Moreover, this arrangement facilitates passage in the blood vessels, for example coronary vessels, until reaching the calcified stenosis to be treated.

The transducer units and in particular the single transducers of which they are formed, are connected to one another in parallel.

In the preferred variant of embodiment of the present invention with the annulus shaped internal ablation unit, the array of transducers has a general cylinder shape. This shape refers specifically to the condition in which the expansible element of the vascular catheter is retracted or not expanded.

According to another embodiment of the invention, the internal ablation unit has a shape slightly tapered toward the tip, i.e., is substantially truncated cone shaped. In this case, all the transducer units are truncated cone shaped, and have different sizes of the diameter of the bases in relation to one another. The transducer units are arranged with a decreasing order of the sizes of the bases proceeding from the unit positioned at the first end in the direction of the last unit positioned at the second end of the array of transducers. Therefore, the array of transducers preferably has a profile with a constant line of slope, i.e., has no steps. In this last variant of embodiment, the transducer units can have a thickness (or height) of a value that is the same or, preferably, different to one another, typically constantly decreasing in the direction from the transducer unit positioned at said first end toward the transducer unit positioned at said second end of the array of transducers.

Said last variant of embodiment, i.e., in the case of the truncated cone shaped array of transducers, makes it easier to insert the internal ablation unit into the blood vessels.

As mentioned previously, each single transducer units comprises at least two components that are physically separated from one another.

Said component preferably has a regular shape, in particular a section of annulus. Therefore, each component has curved sides, so that once the components of a transducer unit are placed side by side and arranged in a circle, the transducer units take, in cross section, an annulus shape, thus having a circular central hole.

In the transducer unit, the transducers are preferably selected from ceramic (or piezoceramic) piezoelectric transducers and electropolymers.

Following this shape and arrangement of the transducer units, the array of transducers has a hole that runs along the whole of its axis of extension, i.e., from the transducer unit that is closest to the control handpiece to the transducer unit that is closest to the insertion tip present in said internal ablation unit. Hereinafter, for brevity, said two units will be defined, respectively, as first transducer unit and last transducer unit.

As mentioned above, the internal ablation unit is positioned on said catheter, more precisely is positioned on said expansible element of the catheter. Said expansible element is housed inside said hole present in the array of transducers. Due to this positioning of said internal ablation unit, when the expansible element expands, the single components of the single transducer units move radially away from one another and thus improve their contact with the walls of the blood vessel into which the internal ablation unit is inserted.

As mentioned above, the internal ablation unit preferably also comprises an insertion tip. The tip is located at the second end of said array of transducers, i.e., after and adjacent to the last transducer unit.

This tip can have various embodiments in regard to shape and, above all, size. The external shape of the tip is generally cone, truncated cone or funnel shaped.

As mentioned above, the device of the present invention also comprises a second ablation unit, also called “external ablation unit” as, in the formation in use, this unit is applied to an external part of the body of a patient, in particular to the area of the skin over the occluded vessel that has the calcified plaque to be treated with the ultrasonic waves emitted by the internal ablation unit.

The external ablation unit has an array of transducers. In this unit the transducers are arranged, for example, in several rows, typically two, three or four rows.

According to a preferred variant of embodiment, the device according to the present invention further comprises a diffuse reflection system of the ultrasonic field. In particular, in this variant, at least one of the components of the transducer units of the internal ablation unit is formed by a diffuse reflection element. More in particular, this transducer unit comprises at least one transducer and at least one diffuse reflection element. In this variant, greater focusing of the external field in the endovascular calcified volume is obtained, leading to an increase of the ultrasonic power emitted and, therefore, a higher disintegrating effect on the calcified plaque.

According to a further variant of embodiment of the present invention, the tip of the internal ablation unit is of active type, i.e., unlike prior art tips, it carries out a vibratory movement in the direction of movement of the catheter.

This tip, hereinafter defined “vibrating tip”, is in fact conceived, as regards, in particular, shape and material with which it is made, to increase the efficiency of the treatments in cases in which the vessels have severe, or even total, occlusion, forming a sort of “plug” inside the blood vessel. In a case like this, it is necessary firstly to be able to perforate said plug and disintegrate it to form a sufficiently large cavity into which to insert at least part, in length, of the first ablation unit. For this purpose, according to this variant, the ablation unit comprises a vibrating element, typically a piezoelectric transducer, preferably positioned at the base of the tip.

In this variant, the vibrating tip behaves as a sort of percussion hammer operated by the first transducer which, vibrating in longitudinal direction to the blood vessel into which the tip is inserted, transfers the mechanical movement to the whole tip, which is thus able to break up the calcified plaque and advance through the blood vessel.

This transducer of the vibrating element, hereinafter “first transducer”, generally has an annular, disc or hollow cylindrical shape.

In detail, the vibrating element is preferably disc shaped. This element is placed aligned with the array of transducers of the internal ablation unit and is positioned adjacent to the second end of said array of transducers, i.e., to the last transducer unit. Said vibrating element has a diameter the same as or smaller than the diameter of the last transducer unit of the array of transducers.

According to a preferred particular embodiment, the tip has a cage structure, substantially cone or truncated cone shaped with a tapered terminal element (also called tip).

The cage preferably has a base and a frame mounted on said base that supports the tapered terminal element. Said tapered element is therefore positioned on the cage on the opposite side to said base.

The frame comprises bars, preferably at least two, more preferably at least three, four or five. The bars preferably extend in longitudinal direction, i.e., in the direction of extension of the internal ablation unit.

The cage houses internally a second transducer, preferably cylindrical in shape. Said second transducer is preferably positioned centrally in the internal space of the cage, preferably aligned with the axis of the internal ablation unit. This arrangement of the second transducer allows the prevalently radial emission of ultrasonic waves. This transducer is, for example, piezoelectric.

The empty space between the bars allows the ultrasonic waves emitted by the second transducer to exit from the cage.

According to this particular variant, the second transducer works synergically with the vibrating element, emitting sonic waves that break up the calcified plaque located in the area at the side of the tip.

The transducer that forms the vibrating element of the tip and said second further transducer in the cage are also connected to the control unit of the device.

The tapered element has the form of a probe, for example funnel shaped, and forms the terminal element of the tip and, therefore, of the first ablation unit.

In general, the tip, in particular the whole of the vibrating tip, even more in particular the probe, is made of a rigid material with adequate mechanical strength, typically steel or titanium.

The present invention also concerns a method for treating occlusive vascular lesions caused by calcified plaques present in the lumen of the blood vessels, this method comprising the simultaneous use of ultrasonic waves at different frequencies (f1, f2) emitted by transducers of two first and second ablation units, wherein the transducers of the first ablation unit and the transducers of the second ablation unit each emit ultrasonic waves with respective frequencies (f1, f2) comprised between 1 MHz and 3 MHz, and wherein the difference between the frequency (f1) of the waves emitted by the first ablation unit and the frequency (f2) of the waves emitted by the second ablation unit is comprised between 30 kHz and 300 KHz, said first ablation unit being in intravascular position and said second ablation unit being in position on the skin.

Other features and advantages of the invention will be apparent from the detailed description hereunder of non-limiting embodiments of the invention, with reference to the accompanying figures, wherein:

- Fig. 1 represents the shock wave pulsed signal waveform;

- Fig. 2 is a schematic representation of the “adjust phase” technique for focusing the ultrasonic field emitted by a transducer unit;

- Fig. 3 represents three time- amplitude graphs respectively ultrasonic waves;

- Figs. 4a and 4b represent schematic views of the device according to an embodiment of the present invention in the condition of use;

- Figs. 5a and 5b represent schematic views of the device according to a variant of the present invention in the condition of use;

- Figs. 6a and 6b are perspective views of the first internal ablation unit according to an embodiment of the present invention;

- Fig. 7 is a perspective view of a transducer unit of the first internal ablation unit according to the present invention;

- Figs. 8a and 8b are perspective views of the internal ablation unit of Figs. 6a and 6b with the balloon of the catheter in the expanded condition;

- Fig. 9 is a sectional view according to a transverse plane of the internal ablation unit of Fig. 6a;

- Fig. 10 is a sectional view according to a transverse plane of the internal ablation unit of Fig. 8a;

- Fig. 11 schematically represents types of reflection of an ultrasonic wave;

- Fig. 12 is a perspective view of the tip of the internal ablation unit according to an embodiment of the present invention;

- Figs. 13 and 14 are perspective views of the internal ablation unit according to a variant of the invention;

- Figs. 15 and 16 are perspective views of the second external ablation unit according to an embodiment of the present invention; - Fig. 17 represents the internal ablation unit of the device according to the present invention in an anatomical region;

- Fig. 18 is a schematic representation of the interaction between two sources of ultrasonic field, one inside the vessel and one outside the body, according to the present invention.

With reference to Figs. 4a-4b and 5a-5b, number 1 indicates as a whole the medical device according to the present invention.

In the context of the present invention, the terms “internal”, “external” refer to the components of the device 1, in the position of use, i.e., with the ablation units positioned one inside and the other resting on the body of the patient, as illustrated in Figs. 4a-4b and 5a- 5b.

As shown in the aforesaid figures, the device 1 comprises a control unit 2, a vascular balloon catheter 3, a first ablation unit 10, mounted on said catheter 3, and a second ablation unit 20.

The vascular catheter 3 is connected at one end 3 a to a control handpiece 5 and has a guide wire 8. The first internal ablation unit 10 is positioned at the opposite end 3b of the vascular catheter 3, more precisely on the length occupied by the balloon 30.

The guide wire 8 runs in a centrale tube of the catheter, and exits through the tip of the internal ablation unit. The guide wire is moved manually, inserted through a hole in the handpiece, and pushed or retracted in the central tube to guide the movement of the vascular catheter to reach the area to be treated, in general through the femoral artery.

A cable 7 connects the control handpiece 5 to the control unit 2.

Similarly, also the second external ablation unit 20 is connected with a respective cable 21 to said control unit 2.

The internal ablation unit 10 comprises transducers organized in an array of transducers indicated as a whole with 11. The array of transducers 12 comprises transducer units 12 (Figs. 6a, 6b) arranged in sequence side by side along the direction of extension of the catheter and regularly spaced from one another. These transducer units 12 are connected to one another in parallel.

The distance between two adjacent transducer units can depend on the level of flexibility required by the catheter and by the size of its cross section.

Also the number of transducer units depends on the area to be treated, i.e., on the features of shape and size of the vessel into which the catheter is inserted.

Fig. 7 illustrates the transducer unit 12 of cylindrical shape, and more precisely in the shape of an annulus. In the example of the figure, the transducer unit 12 comprises three components 12a, 12b, 12c.

These components are separated from one another and are arranged so that each single transducer unit 11 has the shape of an annulus. In practice, each component of the transducer unit has the shape of a sector of annulus.

In Figs. 6a and 6b, the transducer units 12 of the array of transducers 11 are all the same as each other in shape and size, i.e., external and internal diameters and height h.

As mentioned above, the internal ablation unit 4 can be positioned on the balloon 30 of the catheter 3, i.e., the expansible element thereof. When the balloon 30 is not expanded, the components 12a, 12b, 12c of the transducer units 12 of the internal ablation unit 4 are close to one another, as shown in Figs. 6a, 6b and 8a. When the balloon 30 is expanded, said components of the transducer units 12 are moved away from one another radially, as shown in Figs. 8b, 13 and 14.

The transducers 12a- 12c are electrically connected to one another, in parallel. Two insulated electrical cables (not illustrated in the figures) inside the catheter 3 allow connection of a first transducer 12a- 12c, i.e., one of the unit 12 closer to the control handpiece 5, to the control unit 2. Preferably, said cables are interrupted in the control handpiece 5 and carry connectors at the end, housed in said handpiece, which allow connection with respective connectors of the cable 7, allowing connection of the internal ablation unit 10 to the control unit 2. Preferably, the control handpiece 5 comprises a switch that allows opening or closing of the connection of the electrical signal coming from the control unit 2 toward the internal ablation unit 10.

The internal ablation unit 10 is contained in a sheath 18, in turn contained in the vascular catheter. The outer sheath is retracted, to release the ablation unit, through a control positioned on the handpiece 5, for example in the form of a slider or wheel that allows mechanical sliding of the sheath.

The array of transducers 11 of the internal ablation unit 4 is provided, as shown in Figs. 6b and 8b, with high flexibility, to facilitate insertion of the ablation unit into the blood vessels, in particular into the peripheral vessels.

In the embodiments illustrated in the figures, said three components 12a, 12b, 12c of the transducer units 12 are all piezoelectric transducers, preferably of piezoceramic type.

In a variant of embodiment (not illustrated), at least one of the components in at least one transducer unit 12 can be replaced with a reflection element, i.e., an element that is capable of reflecting the ultrasonic wave with diffuse features generated by the at least one transducer present in the same transducer unit (Fig. 12). For this purpose, the reflection element typically has a rough surface. This reflection element can be made of a material selected from aluminum, copper, nickel, steel or titanium. According to a further embodiment illustrated in Fig. 12, the tip 13 of the internal ablation unit 10 is adapted to be able to vibrate. As illustrated in this figure, said vibrating tip comprises a vibrating element 14, generally consisting of a piezoelectric transducer, and a cage 15 of tapered or pointed shape, for example truncated cone shaped, with a tapered terminal element 16.

In detail, the vibrating element 14 is positioned in series with respect to the last transducer unit 12 of the array of transducers 11. The cage 15 has a base 15a and a frame, integral with the base, formed of bars 15b, four in number in the example of the figures, which converge toward the terminal element 16. The base 15a of the cage 15 is in contact with said vibrating element 14.

The cage 15 houses internally a second transducer 17 of cylindrical shape. Said second transducer is placed centrally in the internal space of the cage, aligned with the axis of the internal ablation unit. This second transducer 17 is of piezoelectric type.

Figs. 4a, 4b, 5a and 5b illustrate the second external ablation unit 20 accommodated in a handpiece 22 (Figs. 4a, 4b) or in a plate 23 (Figs. 5a, 5b).

With reference to Figs. 15 and 16, the external ablation unit 20 comprises an array of transducers 25, typically of piezoelectric type. Said transducers 25 are arranged in parallel rows, for example two, three or four in number, as illustrated in the figures. These transducers emit the ultrasonic field, focused on the area to be treated.

In use, said external ablation unit 20 is positioned on the outside of the body of the patient, precisely resting on the skin at the area to be treated inside the body where the internal ablation unit is positioned, as shown in Figs. 4a, 4b, 5a and 5b.

According to an embodiment illustrated in Figs. 5a and 5b, the plate 23 is provided with an elastic strap 26 that allows said plate to be held in position on the part (limb or chest, for example) of the patient to be treated, on the one hand, without the aid of a third person and, on the other, to ensure said unit 20 remains in the same position for the entire treatment period.

In the embodiment with handpiece, the external ablation unit 20 can be integrated with an ultrasonic probe 27 (Figs. 15, 16).

Positioning of the internal ablation unit 10 takes place according to the prior art. The internal ablation unit 10 is inserted by means of vascular catheter, until reaching the area to be treated, with the aid of the control handpiece 5 and of the guide wire 8, inserted into the central housing of the catheter.

In Figs. 13 and 14, the internal ablation unit 10 is wrapped in a sheath 18 that covers the whole array of transducers 11. The sheath 18 guarantees electrical insulation.

After reaching the desired area, the internal ablation unit 10 is activated to carry out the treatment through ultrasound. As a function of the size of the lumen, the balloon is expanded to a greater or lesser extent to take the components of the transducer units 12 close to or in contact with the areas to be treated.

Fig. 17 represents the internal ablation unit of the device according to the present invention in a coronary artery.

Fig. 18 represents the interaction between the external field emitted by the external ablation unit 20 combined with the field emitted by the internal ablation unit 10 when the device of the present invention is in use.

As mentioned previously, the interaction between the ultrasonic wave fields that have frequencies of the order of a few MHz, but with a difference between the two frequencies, allows the effect of combination called “beating”, i.e. the generation of a lower frequency, to be exploited. The total ultrasonic field generated by said interaction therefore produces a lower frequency, of the order of KHz. In this way an increase in the effectiveness of cavitation, as described in the literature, is obtained.

The thickness of the piezoelectric transducers, i.e., the size in the direction of extension of the catheter 3, is selected as a function of the field frequency to be generated. Naturally, the invention is not limited to the embodiments illustrated and described above, and those skilled in the art can make modifications and variants without departing from the scope of the invention.

Claims

1. A medical device (1) for treating occlusive vascular lesions caused by calcified plaques present in the lumen of the blood vessels, said device (1) comprising: at least one control unit (2) that includes at least one electrical signal generator; a vascular catheter (3) with expansible element (30); a first ablation unit (10) mounted on the catheter (3), connected to the control unit (2) and housing ultrasonic transducers (12) that receive pulsed electrical signals from the control unit (2); a second ablation unit (20) connected to the control unit (2) and housing ultrasonic transducers (25) receiving pulsed electrical signals from the control unit (2); wherein said transducers (12) of the first ablation unit (10) and said transducers (25) of the second ablation unit (20) emit ultrasonic waves with respective frequencies (f1, f2) of the same order of magnitude and comprised between 1 MHz and 3 MHz, wherein the difference (Δf) between the frequency (f1) of the waves emitted by the first ablation unit (10) and the frequency (f2) of the waves emitted by the second ablation unit (20) is comprised between 30 kHz and 300 KHz and wherein said ultrasonic waves emitted at the first and second frequencies (f1, f2) by the first and second ablation units (10, 20) generate, through the physical phenomenon of beat, ultrasonic waves with a lower frequency (fb) equal to the absolute value of the difference (Δf) between said first and second frequencies (f1, f2), said ultrasonic waves emitted at the frequencies (f1, f2, fb) bringing about a phenomenon of cavitation in the lumen of the vessel which causes fragmentation of the calcified plaques.

2. The medical device (1) according to claim 1, wherein the difference between the frequency of the ultrasonic wave emitted by the first ablation unit (20) and the frequency of the ultrasonic wave emitted by the second ablation unit (20) is comprised in the interval from 30-200 KHz, preferably 80-180 KHz.

3. The medical device (1) according to any one of the preceding claims, wherein the transducers (12, 25) are piezoelectric or electropolymeric.

4. The medical device (1) according to any one of the preceding claims, wherein the first ablation unit (10), mounted on said expansible element (30), comprises an array of transducers (11) comprising several transducer units (12), said transducer units (12) each having a central through hole and being arranged side by side along the direction of extension of the catheter (3).

5. The medical device (1) according to claim 4, wherein the transducer units (12) are electrically connected in parallel.

6. The medical device (1) according to claim 4 or 5, wherein each transducer unit (12) is formed by at least two components (12a, 12b, 12c) physically separated from each other, at least one of which is an ultrasonic transducer.

7. The medical device (1) according to the preceding claim, wherein at least one of the components (12a, 12b, 12c) of the transducer units (12) is a reflecting element.

8. The medical device (1) according to any one of the preceding claims, wherein the internal ablation unit (10) comprises a tip (13) equipped with a piezoelectric transducer (14) to impart a vibrational movement to the tip (13).

9. The medical device (1) according to the preceding claim, wherein the tip (13) further comprises a second piezoelectric transducer (17).

10. The medical device (1) according to any one of the preceding claims, wherein the second ablation unit (20) comprises an array of transducers (25) arranged in one or more rows, said second ablation unit (20) being housed in a handpiece or handle (22) or in a plate (23).

11. A method for treating occlusive vascular lesions caused by calcified plaques present in the lumen of the blood vessels that comprises the simultaneous use of ultrasonic waves at different frequencies (f1, f2) and emitted by transducers of first and second ablation units (10, 20), wherein the transducers (12) of the first ablation unit (10) and the transducers (25) of the second ablation unit (20) each emit ultrasonic waves with respective frequencies (f1, f2) comprised between 1 MHz and 3 MHz, and wherein the difference between the frequency (f1) of the waves emitted by the first ablation unit (10) and the frequency (f2) of the waves emitted by the second ablation unit (20) is comprised between 30 kHz and 300 KHz, said first ablation unit (10) being in intravascular position and said second ablation unit (20) being positioned on the skin.