Device for treating thrombosis of blood vessel by ultrasound

Abstract

The invention relates to a device for treating thrombosis of a blood vessel by ultrasound, comprising:-a therapeutic ultrasound transducer (TUT) adapted to generate focused ultrasound waves (OUF) propagating along a transmission axis (AE); -an imaging ultrasound transducer (TUI) for use with the therapeutic transducer; -means (SMDR, FEF) for moving the focal region of the therapeutic ultrasound transducer, for moving the focal region of the therapeutic ultrasound transducer relative to the imaging transducer along the emission axis; a motorized mechanical system (SMM) for translating the transducer at least along a first axis (AD1) parallel to the emission axis and a second axis (AD2) perpendicular to the first axis; -an electronic control system (SEC) for controlling the motorized mechanical system and means for moving the focal region of the treatment transducer.

Description

[0001] This application is a divisional application of the PCT patent application entered into China with Chinese patent application number 201880069105.9, invention name “Device for treating thrombosis in blood vessels by ultrasound” and application date October 18, 2018. Technical Field

[0002] The present invention relates to a device for treating thrombosis in blood vessels by means of ultrasound, more particularly by means of tissue destruction. Background Art

[0003] Blockage of a blood vessel, vein or artery by an acute thrombotic process (clot formation or thrombosis) is a common and serious mechanism responsible for the majority of deaths worldwide. In arteries, thrombosis is the cause of most strokes and myocardial infarctions. When thrombosis occurs in the venous network, it results in pain, edema and the risk of clot dislodgment, which can lead to pulmonary embolism. Persistent blockage of a vein by thrombosis may ultimately lead to chronic venous insufficiency, manifested by pain, edema and ulcers, which can lead to a substantial reduction in quality of life.

[0004] The principle of treatment for arterial or venous thrombosis is based on systemic anticoagulation to avoid the expansion of the thrombus and embolic complications. However, in the case of deep vein thrombosis, this treatment method is ineffective for chronic venous insufficiency because, in most cases, it cannot recanalize the thrombosed vein. The use of thrombolytic therapy can recanalize the blocked vein, but systemic administration is dangerous due to the possibility of inducing bleeding. Therefore, this treatment method is not recommended in the case of venous thrombosis without severe pulmonary embolism. The use of in situ thrombolysis can limit the systemic effect by local administration through a catheter. These techniques are invasive and usually require the implantation of an external device (usually a stent). Therefore, there are local risks (bleeding, infection) due to the continued presence of the intravascular device, and there is a risk of further obstruction. Another treatment method is the use of ultrasound alone or in combination with drugs. Specifically, it is well known that the technique called tissue destruction is used to break up the clot and thus reestablish circulation through the blocked blood vessel; then, "thrombus destruction" was proposed. Tissue destruction is the use of intense and focused ultrasound pulses to induce a local cavitation effect, thereby mechanically breaking down the targeted soft tissue.

[0005] Document US 5,827,204 describes a therapeutic device based on ultrasound, which can be used in particular for thrombus destruction therapy. The device comprises a therapeutic transducer coupled to an imaging transducer, the two transducers being connected to an actuator so that they move axially.

[0006] International patent application WO 2009 / 094554 and the following articles:

[0007] -Xi Zhang et al., “Histotripsy thrombolysis on retracted clots,” Ultrasound in Med. & Biol., Vol. 42, No. 8, August 2016, pp. 1903-1918;

[0008] -Xi Zhang et al., “Non-invasive thrombolysis using histotripsy in aporcine deep vein thrombosis model,” Ultrasound in Med. & Biol., Vol. 43, No. 7, July 2017; and

[0009] The thrombus-destroying technology was disclosed as having been validated through studies conducted in vitro and in pigs in a 2017 article.

[0010] In these cases, therapeutic ultrasound waves with a frequency of 1 MHz are applied by means of a multi-element "therapeutic" transducer of set focus, in the center of which is arranged a transducer for imaging with ultrasound (ultrasound echography). In in vitro studies, both the transducer and the capillary tube simulating the vein to be treated are immersed in an acoustic coupling liquid. In in vivo studies, the transducer is immersed in an acoustic coupling liquid confined by a bottomless bowl and a plate made of plastic that is in contact with the skin of the animal. The imaging transducer allows the vein to be treated and the focus of the therapeutic transducer to be located, which can be seen due to the generation of a cloud of cavitation bubbles. The assembly consisting of the therapeutic transducer and the imaging transducer is then mechanically moved until the focus coincides with the vein.

[0011] The article "Efficacy of histotripsy combined with rt-PA invitro" by KB Bader et al. (Phys. Med. Biol., July 21, 2016) studied the optimal operating conditions for the method of combining tissue destruction and administration of thrombolytic drugs to treat venous thrombosis. Only in vitro studies using a multi-ring treatment transducer, an imaging transducer (separated from the previous transducer), and a capillary tube simulating a vein (all immersed in a coupling liquid) are provided.

[0012] Acoustic coupling via a transducer immersed in a liquid is not practical. In addition, the imaging transducer must be kept at a certain distance from the patient's skin, which reduces the quality of the acquired image. Moreover, this distance is not constant, so the image quality varies. This reduces the precision of the treatment, thus reducing the effectiveness of the treatment, and increases the risk of damaging the vessel wall when using focused ultrasound therapy. Summary of the invention

[0013] The present invention aims to overcome the above-mentioned disadvantages of the prior art. More specifically, the present invention aims to provide an imaging-assisted thrombus destruction method that is easier to implement and can achieve higher treatment accuracy, especially reducing the risk of vascular wall damage.

[0014] According to the invention, this object is achieved by moving the focal point of the therapeutic ultrasound transducer relative to the imaging ultrasound transducer along the transmission axis by mechanical and / or electronic means. This enables the imaging transducer to remain in contact with the surface of the human or animal body to be treated, or more generally, to maintain a substantially constant distance from the latter, during the scanning of the area to be treated, thus obtaining images of higher quality. In turn, images of higher quality make it possible to locate the vessel wall to be treated more accurately, thus avoiding unintended damage to the vessel wall.

[0015] According to an advantageous embodiment of the invention, this object can also be achieved by using a therapeutic ultrasound transducer operating at a frequency greater than or equal to 2 MHz (instead of a therapeutic ultrasound transducer operating at a frequency of about 1 MHz as in the prior art). This allows a smaller and more stable focus to be obtained, which can take advantage of a better understanding of the position of the vessel wall in order to avoid damage to the vessel wall.

[0016] The subject of the present invention is therefore a device for treating thrombosis of blood vessels using ultrasound, comprising:

[0017] - a therapeutic ultrasound transducer adapted to generate focused ultrasound waves propagating along an emission axis;

[0018] - an imaging ultrasound transducer, which is used in conjunction with the therapeutic ultrasound transducer and is suitable for acquiring a two-dimensional or three-dimensional image of a region to be treated of the human or animal body, said region to be treated including the focal point of the therapeutic ultrasound transducer;

[0019] - means for moving the focus of the therapeutic ultrasound transducer, for moving the focus of the therapeutic ultrasound transducer relative to the imaging ultrasound transducer along the transmission axis;

[0020] a motorized mechanical system adapted to move the therapeutic ultrasound transducer and the imaging ultrasound transducer at least translationally along a first axis of motion parallel to the emission axis and translationally along or rotationally about a second axis of motion non-parallel to the first axis of motion; and

[0021] -Electronic control system, which is configured as follows:

[0022] - Driving a motorized mechanical system to scan the area to be treated while maintaining a predefined tolerance between the imaging ultrasound transducer and the surface of the human or animal body

[0023] Constant distance;

[0024] - driving the means for moving the focus of the therapeutic ultrasound transducer to control the position of the focus along the transmission axis during said scanning.

[0025] According to a specific embodiment of the present invention:

[0026] -The device may also include: a force sensor suitable for generating a signal indicating the force applied to the imaging ultrasound transducer in a direction parallel to the transmission axis; an electronic control system configured to acquire the signal and use the signal to drive a motorized mechanical system to keep the imaging ultrasound transducer in contact with the surface of the human or animal body during scanning.

[0027] - The electronic control system may further be configured to apply the imaging ultrasound transducer to the surface of the human or animal body with a constant force during scanning.

[0028] - The electronic control system may also be configured to analyse images acquired by the therapeutic ultrasound transducer to detect the surface of the human or animal body to drive the motorised mechanical system during the scanning.

[0029] The electronic control system may further be configured to drive the means for moving the focal point of the therapeutic ultrasound transducer in such a way that the focal point follows a predefined path inside the human or animal body during scanning.

[0030] - The electronic control system can also be configured as:

[0031] a) driving the motorized mechanical system to perform a first scan of the area to be treated;

[0032] b) acquiring, during this first scan, a plurality of images of the region while maintaining the therapeutic ultrasound transducer inactive;

[0033] c) driving the motorized mechanical system to perform a second scan of the area to be treated;

[0034] d) during this second scan, activating the therapeutic ultrasound transducer and driving the means for moving the focus of the therapeutic ultrasound transducer so that the focus follows a predefined path inside the body, the predefined path being identified from the images acquired during the first scan.

[0035] -More specifically, the electronic control system may also be configured as:

[0036] b1) analyzing the images acquired during the first scan to identify blood vessels in the area to be treated of the human or animal body;

[0037] b2) determining the predefined path inside the human body such that the predefined path corresponds to the blood vessel.

[0038] - In addition, the electronic control system may be further configured to drive the motorized mechanical system so that, during the second scan, the blood vessel is located in a central portion of the field of view of the imaging ultrasound transducer.

[0039] The electronic control system may also be configured to acquire, during the second scan, a plurality of images of the area to be treated and to use these images to drive the motorized mechanical system.

[0040] - The therapeutic ultrasound transducer may be a multi-element transducer, and the means for moving the focus of the therapeutic ultrasound transducer comprises: an electronic beam former configured to drive the elements of the transducer with variable delays so as to emit focused ultrasound waves with an adjustable focal length. More specifically, it may be a concentric multi-ring transducer.

[0041] - the means for moving the focal point of the therapeutic ultrasound transducer may comprise a mechanical system allowing relative movement of the therapeutic ultrasound transducer and the imaging ultrasound transducer along the transmission axis.

[0042] - The imaging ultrasound transducer may extend beyond the therapeutic ultrasound transducer in a direction parallel to the emission axis.

[0043] - The imaging ultrasound transducer may be arranged in the center of the therapeutic ultrasound transducer.

[0044] - The device may further comprise: an acoustic interface device adapted to couple the focused ultrasound waves generated by the therapeutic ultrasound transducer to the surface of the human or animal body.

[0045] - The motorized mechanical system may have three translational degrees of freedom and three rotational degrees of freedom.

[0046] - The therapeutic ultrasound transducer may be adapted to generate focused ultrasound waves having a frequency greater than or equal to 2 MHz.

[0047] - The electronic control system and the imaging ultrasound transducer may also be configured to monitor recanalization of the treated blood vessel by Doppler imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Other characteristics, details and advantages of the invention will become more apparent on reading the description given with reference to the accompanying drawings, which are provided and shown by way of example respectively:

[0049] - Figure 1 is a schematic diagram of an apparatus according to one embodiment of the present invention;

[0050] - Figure 2 is a flow chart of a treatment approach using this device. DETAILED DESCRIPTION

[0051] exist Figure 1 In the device, the therapeutic ultrasound transducer TUT is a multi-element annular transducer (i.e., it comprises a set of annular ultrasound transducers) or elements (referenced E1, E2, E3, E4) arranged concentrically with gradually decreasing radius to form a spherical shape, or more generally, a concave (e.g., parabolic) cap shape. Such a transducer is described, for example, in document US 5,520,188.

[0052] Of course, the number of transducers is not necessarily equal to 4; preferably, this number will be comprised between 4 and 20 to avoid excessive complexity.

[0053] The annular elements are preferably circular; more precisely, they may have a frustoconical shape with a circular base, but other shapes are envisioned. They may be continuous or consist of separate segments.

[0054] The ultrasound waves UF generated by the elements E1-E4 of the treatment transducer TUT are focused to a focus TFU, which generally has an elliptical shape. The main emission axis of the ultrasound waves is indicated by "z". For simplicity, although not necessary, this axis will be considered to be perpendicular to the surface SC (i.e., the skin) of the human or animal body C to be treated. The ultrasound waves are coupled to the body through an acoustic interface IA, which is formed, for example, by a pocket made of flexible plastic filled with gel or degassed water. The pocket has a convex surface in contact with the elements of the transducer and a substantially flat face intended to be in contact with the surface SC. In use, this flat face can in turn be coated with an acoustic coupling gel.

[0055] The concave shape of the transducer ensures that the ultrasound UF is focused along the z-axis at a "natural" or "geometric" focal length. Electronic focusing, obtained by introducing a phase shift between the drive signals of the elements, enables fine modification of this focal length. Figure 1In an embodiment of the present invention, these drive signals are generated by an electronic control system SEC and the phase shift is introduced by a beamforming circuit FEF driven by the system SEC.

[0056] Advantageously, the therapeutic transducer is configured to operate at a frequency, for example, higher than or equal to 2 MHz, equal to 2.25 MHz, whereas in the above-mentioned prior art, the frequency of the therapeutic ultrasound waves is about 1 MHz. In particular, for a given geometry of the transducer and a given focal length, the width (perpendicular to the propagation direction) and the length (parallel to the length) of the focus are inversely proportional to the frequency. Numerical simulations have confirmed this theoretical result. Therefore, by operating at 2 MHz instead of 1 MHz, the volume of the focus can be divided by a factor of 8. This allows better targeting of the clot to be broken up and minimizes the risk of damaging the vessel wall.

[0057] In vitro tests have confirmed the effectiveness of 2.25MHz ultrasound in thrombus destruction treatment. In these tests, human blood was placed in a tube of 6mm inner diameter made of silicone that simulates the femoral vein of a person, and the tube was kept in a vertical position. Blood coagulation was induced by adding 20nM calcium chloride, resulting in a clot of 2.5cm in length. Next, the test tube was placed in a horizontal position and loaded with saline solution (0.9% NaCl) under a pressure of 30cm H2O. Only the test tube containing the obstructive clot was retained and received thrombus destruction treatment. This treatment was carried out by two ultrasonic transducers working at 2.25MHz, with a focal length of 38mm and a diameter of 38mm. The tube, thrombus destruction transducer and imaging transducer were placed in a degassed water bath. Three treatment schemes were tested: passing 3 times at a speed of 1mm / s, 2mm / s and 3mm / s. In each case, two transducers were driven with a pulse of 8 cycles of 2.5kW to produce a peak negative pressure of -15MPa. The first protocol proved to be the best, resulting in effective recanalization (80 ± 7% of maximum flow) after 3 passes within a treatment time of 90 seconds. Very few debris particles with a size greater than 100 μm were detected (1.6 ± 1.7 per thrombus), but no debris particles with a size greater than 200 μm: this can be considered to indicate that there is no risk of embolism.

[0058] An ultrasound imaging transducer TUI (e.g. a two-dimensional or three-dimensional ultrasound probe) is arranged in the center of the therapy transducer (inside the element E4 of minimum radius). This transducer has a field of view CV extending mainly along the z-axis and including the area where the focus TFU can usually be found. More precisely, in Figure 1 In an embodiment of the present invention, the imaging ultrasound transducer TUI is of two-dimensional type and has a field of view in the xz plane. An imaging control system SEC drives the imaging transducer, receives the signals Im acquired by the latter and processes these signals to reconstruct an image of the region to be treated RAT of the body C.

[0059] Advantageously, the imaging transducer extends axially (ie in the z direction) beyond the outer edge of the therapeutic transducer. For example, it may extend by 10-50 mm, preferably 10-25 mm. The acoustic interface IA may have an aperture that allows passage of the imaging transducer, or, as Figure 1 The case shown has a groove commensurate with the imaging transducer. This allows the active face of the imaging transducer to be in "direct" contact with the surface SC of the body C (in fact, through the thin layer of acoustic coupling gel), or in "indirect" contact (through the pocket of the acoustic interface IA and the double thickness of the same gel layer) while the edge of the therapeutic transducer can be spaced from this surface.

[0060] exist Figure 1 In an embodiment of the present invention, the therapeutic transducer TUT and the imaging transducer TUI are connected by a mechanical system SMDR, allowing translational relative movement in the z direction. For example, the imaging transducer can be fixed to the base of the mechanical system, and the therapeutic transducer is connected to the base by three actuating cylinders (only two of which are shown in the figure) oriented along the z axis. The three actuating cylinders are driven synchronously by an electronic control system SEC, so that the therapeutic transducer moves in the z direction, and therefore the focus TFU of the focused ultrasound waves moves in the z direction without moving the imaging transducer at the same time. The mechanical system SMDR for achieving relative movement can also take other forms: for example, it can be based on a rack and pinion system.

[0061] The presence of the mechanical system SMDR is not necessary: ​​in particular, the multi-element structure of the treatment transducer and the beamforming circuit FEF also allow the focus TFU of the focused ultrasound to be moved in the z direction relative to the imaging transducer. In turn, the mechanical system SMDR can meet the requirements without the need to provide a multi-element transducer and an electronic focusing system. In any case, in the device according to the invention, the focus TFU can be positioned in the axial direction without moving the imaging transducer. In contrast, this is not possible in the devices described in the international patent application WO 2009 / 094554 and in the above-mentioned article by Xi Zhang et al., in which the focus can only be positioned by moving the treatment transducer and the imaging transducer together.

[0062] exist Figure 1In an embodiment of the invention, the imaging transducer TUI is connected to the base of the mechanical system SMDR, or more generally to the holding part, via a force sensor CF (which is, for example, piezoelectric), so as to measure the force applied to the transducer in the z direction. The force measurement signal SF acquired by the sensor is sent to the electronic control system SEC. This has a dual function: on the one hand, the detection of a non-zero force ensures that the imaging transducer is indeed in direct or indirect contact with the surface SC of the body C; on the other hand, the quantitative measurement of this force prevents the imaging transducer from being pressed too much against the surface SC and squeezing the tissue of the body C.

[0063] The presence of the force sensor CF is not essential. In particular, it is also possible to use techniques for analyzing images reconstructed by the electronic control system to detect the surface SC and determine its position relative to the transducer TUI.

[0064] The assembly comprising the therapy transducer TUT, the imaging transducer TUI and, where appropriate, the mechanical system SMDR for achieving relative movement and / or the force sensor CF is fixed to a motorized mechanical system SMM driven by an electronic control system SEC, allowing movement with at least two degrees of freedom relative to the base (and therefore relative to the body C):

[0065] - a translation along a first axis AD1 parallel to the z-axis; and

[0066] - a translation along or a rotation about a second axis AD2 which is non-parallel to and generally perpendicular to the first axis.

[0067] exist Figure 1 In an embodiment of the invention, the second degree of freedom is a translation along a second axis AD2 parallel to the x direction. More precisely, in this embodiment, the motorized mechanical system SMM comprises a carriage sliding along a track oriented along the axis AD2 (x) and carrying an actuating cylinder which ensures a translation along the axis AD1 (z). In a more complex embodiment, multiple degrees of freedom can be provided, for example three translations and three rotations, more specifically three translations along orthogonal axes x, y and z and three rotations around these axes. This can be achieved in particular by a mechanical arm.

[0068] As described above, the electronic control system SEC performs multiple functions: driving the mechanical system SMDR and the motorized mechanical system SMM for achieving relative motion, driving the therapeutic transducer and the imaging transducer, acquiring imaging signals, reconstructing and analyzing images, acquiring force measurement signals, etc. The system may include one or more computing devices and / or dedicated digital electronic boards. These components do not necessarily have to be located in one place, but may be connected specifically via a bus, a local area network or even the Internet.

[0069] The device according to the present invention can be used to implement Figure 2 Methods for treating thrombosis.

[0070] First, step a) - driving the motorized mechanical system SMM by the electronic control system SEC to perform a first scan of the surface SC of the body C according to the area to be treated RAT. At the same time, step b) - acquiring multiple images of the area RAT using the imaging ultrasound transducer TUI, preferably allowing a three-dimensional reconstruction of the latter. The motorized mechanical system SMM is driven so that the imaging transducer maintains a constant distance from the surface SC with a predefined tolerance that is typically less than or equal to 10% and preferably less than 1%. This distance is typically between 0 (direct or indirect contact, which is the preferred embodiment) and 40 mm to ensure a satisfactory and stable image quality during the scan. As mentioned above, in addition, when the imaging transducer is in contact with the surface SC, the force measurement signal SF can be used to keep the pressure exerted by the transducer on the surface constant (also with a tolerance that is typically less than or equal to 10% and preferably less than 1%).

[0071] During this first scan, the therapy transducer remains inactive.

[0072] Next, step b1) the electronic control system SEC analyses the images acquired during the first scan to automatically identify the blood vessels to be treated in the region RAT ( Figure 1 The blood vessel can be detected by selecting or reconstructing a plane ( Figure 1 In the case of the image, a cross-sectional view of the plane yz) is obtained, and this step is performed by applying a circle detection algorithm, which can be based on a Hough transform or a Canny-Dériche edge detection in conjunction with an accumulator that determines the position of the center of the circle using a voting mechanism. Other known algorithms can also be used. As a variant, where appropriate, the blood vessels can be detected by the operator using thresholds and / or edge detection of the acquired images. Next, step b2) - determining the path or trajectory inside the body C and along the identified blood vessel V. This operation can be performed automatically by the electronic control system SEC or manually by the operator.

[0073] Once these preparatory procedures are completed, the actual treatment can begin.

[0074] Step c) - The motorized mechanical system SMM is driven again by the electronic control system SEC to perform a second scan of the surface SC of the body C. As in the first scan, the drive is such that the imaging transducer is kept at a constant distance from the surface SC (this distance is preferably between 0 (preferably) and 40 mm, with a tolerance not higher than 10% or even not higher than 1%). Also as in the first scan, while the imaging transducer is in contact with the surface SC, the force measurement signal SF can be used to keep the pressure exerted by the transducer on said surface constant (also with a tolerance typically less than or equal to 10% and preferably less than 1%).

[0075] The second scan is usually different from the first scan. Specifically, the purpose of the first scan is to achieve a detailed exploration of the area to be treated containing the vessel V to be treated, while during the second scan, the motorized mechanical system SMM is driven so that the vessel V is located in the central area of ​​the field of view CV of the imaging transducer (for example, one third of the center along the z-axis and along the axis perpendicular to z). Advantageously, the images acquired during the second scan are used to drive the motorized mechanical system in a closed loop.

[0076] During the second scan, the therapeutic ultrasound transducer TUT is activated and the mechanical system SMDR and / or the beam forming circuit FEF for achieving relative movement are driven so that the focus TFU of the focused ultrasound waves emitted by the transducer TUT follows the path defined in step b2). Figure 2 The last step d) of the method.

[0077] Furthermore, during or after the second scan, Doppler ultrasound images may be acquired using an imaging ultrasound transducer under the control of the electronic system SEC to monitor recanalization of the treated blood vessel by Doppler imaging.

Claims

1. A device for treating thrombosis of a blood vessel using ultrasound, comprising: - a therapeutic ultrasound transducer (TUT) adapted to generate focused ultrasound waves (OUF) propagating along an emission axis (AE); - an imaging ultrasound transducer (TUI) adapted to acquire a two-dimensional or three-dimensional image (Im) of a region to be treated (RAT) of a human or animal body (C), said region to be treated including a focal point (TFU) of the therapeutic ultrasound transducer, in combination with the therapeutic ultrasound transducer; - means for moving the focus of the therapeutic ultrasound transducer (SMDR, FEF) for moving the focus of the therapeutic ultrasound transducer relative to the imaging ultrasound transducer along the transmission axis; The invention is characterized in that it also includes: - a motorized mechanical system (SMM) adapted to move the therapeutic ultrasound transducer and the imaging ultrasound transducer at least translationally along a first axis of motion (AD1) parallel to the emission axis and translationally along or rotationally around a second axis of motion (AD2) non-parallel to the first axis of motion; and - Electronic Control System (SEC), which is configured as follows: a) driving the motorized mechanical system to perform a first scan of the area to be treated; b) acquiring a plurality of images of the region while maintaining the therapeutic ultrasound transducer inactive during the first scan; c) driving the motorized mechanical system to perform a second scan of the area to be treated; d) during said second scan, activating a therapeutic ultrasound transducer and driving means for moving a focal point of the therapeutic ultrasound transducer such that said focal point follows a predefined path inside said human or animal body, said predefined path being identified from the images acquired during the first scan; The first scan and the second scan are performed such that a distance (SC) between the imaging ultrasound transducer and the surface of the human or animal body remains constant.

2. The device for treating thrombosis of a blood vessel using ultrasound according to claim 1, further comprising: a force sensor (CF) adapted to generate a signal (Sf) indicative of a force applied to the imaging ultrasound transducer in a direction parallel to the transmit axis; the electronic control system being configured to acquire the signal and to utilize the signal to drive a motorized mechanical system to keep the imaging ultrasound transducer in contact with the surface of the human or animal body during scanning.

3. The device for treating thrombosis of a blood vessel using ultrasound according to claim 2, wherein: The electronic control system is further configured to apply the imaging ultrasound transducer to the surface of the human or animal body at a constant force during scanning.

4. Device for treating thrombosis of a blood vessel using ultrasound according to one of the preceding claims, wherein: The electronic control system is further configured to analyze images acquired by the imaging ultrasound transducer to detect the surface of the human or animal body to drive the motorized mechanical system during the scanning.

5. The device for treating thrombosis of a blood vessel using ultrasound according to claim 1, wherein: The electronic control system is also configured as: b1) analyzing the images acquired during the first scan to identify blood vessels (V) in the area to be treated of the human or animal body; b2) determining the predefined path inside the human or animal body such that the predefined path corresponds to the blood vessel.

6. The device for treating thrombosis of a blood vessel using ultrasound according to claim 5, wherein: The electronic control system is further configured to drive the motorized mechanical system such that, during the second scan, the blood vessel is located in a central portion of a field of view (CV) of the imaging ultrasound transducer.

7. The device for treating thrombosis of a blood vessel using ultrasound according to claim 6, wherein: The electronic control system is further configured to acquire a plurality of images of the area to be treated during the second scan and utilize the images to drive the motorized mechanical system.

8. The device for treating thrombosis of a blood vessel using ultrasound according to claim 1, wherein: The therapeutic ultrasound transducer is a multi-element transducer, and the device for moving the focus of the therapeutic ultrasound transducer includes: an electronic beam forming device (FEF) configured to drive the elements (E1, E2, E3, E4) of the transducer with variable delays to transmit focused ultrasound waves with an adjustable focal length.

9. The device for treating thrombosis of a blood vessel using ultrasound according to claim 8, wherein: The therapeutic ultrasound transducer is a concentric multi-ring transducer.

10. The device for treating thrombosis of a blood vessel using ultrasound according to claim 1, wherein: The means for moving the focal point of the therapeutic ultrasound transducer comprises a mechanical system (SMDR) which allows relative movement of the therapeutic ultrasound transducer and the imaging ultrasound transducer along the transmission axis.

11. The device for treating thrombosis of a blood vessel using ultrasound according to claim 1, wherein: The imaging ultrasound transducer extends beyond the therapeutic ultrasound transducer in a direction parallel to the transmit axis.

12. The device for treating thrombosis of a blood vessel using ultrasound according to claim 1, wherein: The imaging ultrasound transducer is arranged at the center of the therapeutic ultrasound transducer.

13. The device for treating thrombosis of a blood vessel using ultrasound according to claim 1, further comprising: An acoustic interface arrangement (IA) is adapted to couple focused ultrasound waves generated by a therapeutic ultrasound transducer to said surface of the human or animal body.

14. The device for treating thrombosis of a blood vessel using ultrasound according to claim 1, wherein: The motorized mechanical system has three translational degrees of freedom and three rotational degrees of freedom.

15. The device for treating thrombosis of a blood vessel using ultrasound according to claim 1, wherein: The therapeutic ultrasound transducer is suitable for generating focused ultrasound waves with a frequency greater than or equal to 2 MHz.

16. The device for treating thrombosis of a blood vessel using ultrasound according to claim 1, wherein: The electronic control system and imaging ultrasound transducer are also configured to monitor recanalization of the treated blood vessel by Doppler imaging.

Images