Ultrasonic application device, robotic installation comprising such a device, and method for pressure control of the position of such a device

Abstract

Ultrasound application device, robotic installation comprising such a device, and method for pressure control of the position of such a device. The invention relates to an ultrasound application device (1) intended to be mounted on a robotic arm and comprising a focused ultrasonic transducer (2) and a means (3) for measuring contact pressure between said device (1), the skin of a subject, and an acoustic coupling interface (5) for transmitting waves from the transducer (2) to the skin upon contact. Device (1) characterized in that the coupling interface (5) comprises a closed enclosure (6) containing a substantially incompressible liquid and having a flexible wall (8), forming the part of the device (1) that comes into contact with the skin, and in that said enclosure (6) is in direct fluidic contact with a pressure sensor (3) measuring the contact pressure and forming part of said device (1).Figure to be published with the abbreviation: Fig. 3.

Description

Title of the invention: Ultrasonic application device, robotic installation comprising such a device, and method for pressure control of the position of such a device

[0001] The present invention relates to the field of devices, installations and methods related to the application of ultrasound, in particular with the use of focused ultrasound (or FUS for "Focused Ultrasounds"), for various therapeutic purposes, including (but not limited to) transcranial application.

[0002] In this context, the invention relates to an ultrasound application device, a robotic installation comprising such a device, a method for pressure control of the position of an ultrasound application device and automatic and semi-automatic methods of treatment by focused ultrasound applied by means of a aforementioned treatment ultrasound application device.

[0003] Unlike other invasive (surgery), percutaneous (interventional radiology), or non-invasive (magnetic fields) access methods, ultrasound waves can be focused onto deep targets with a spatial resolution on the order of millimeters, without damaging surrounding tissues. Worldwide, ultrasound is being extensively studied in the clinical field for various medical applications. It can be used in thermal ablation or tumor histotripsy, or at the brain level through high-precision neuromodulation or blood-brain barrier (BBB) ​​opening. The latter, by facilitating the local penetration of certain molecules, offers an approach to treating tumorous or neurodegenerative conditions such as Alzheimer's or Parkinson's disease.

[0004] A focused ultrasonic transducer generally has a discoidal (ring) or rectangular (array) shape, with dimensions ranging from approximately 3 cm to 8 cm, and an active surface that is either flat or concave. This active surface is composed of multiple piezoelectric elements whose vibrations are controlled by power electronics. Each piezoelectric element is excited with an electrical wave whose amplitude, frequency, and phase shift parameters are controlled to produce a spatial focusing of the acoustic waves through wave interference. This focusing significantly increases the pressure within the medium through which the waves propagate, in a region commonly called the focal spot, which corresponds to the pressure maximum.

[0005] Depending on the design of the transducers, frequencies on the order of hundreds of kHz up to approximately 1 MHz are used. In homogeneous liquid media, the Waves propagate at speeds that depend on the nature of the liquid. In water, depending on the directivity and the number of piezoelectric elements, the focal zone can thus be a few millimeters in size with an oval ellipsoid shape.

[0006] In the human body, for precise focusing, it is necessary to simulate the passage of acoustic waves through tissues because propagation speeds and attenuation vary depending on tissue density, such as cortical bone, trabecular bone, or the brain. Personalized treatment planning based on computed tomography and radiography is often required, particularly for transcranial FUS. The effect of the skull, in particular, is similar to a lensing effect, which can lead to wave defocusing. Due to this acoustic simulation-based planning and the required precision, a transducer positioning system providing extremely accurate positioning, with measurement tolerances on the order of millimeters, is necessary to precisely locate the transducer and position it optimally relative to the chosen target.For multi-element phased arrays, positioning errors can be partially compensated in three dimensions by electronic phase shifting (wave phase shifting). However, the most commonly used transducers, with a few ring elements, often only allow for axial shift of the focal point depth. Due to the lever arm related to the focal depth, often 50 mm to 60 mm relative to the transducer surface, a displacement of a few millimeters or a tilt error of a few degrees can lead to significant off-target focusing, or even complete defocusing due to the lensing effect of the skull bone, for example.

[0007] Furthermore, ultrasound waves are absorbed or deflected very strongly by air, or by the presence of air bubbles within the medium through which they propagate. Maintaining good acoustic contact, that is, contact via a liquid medium between the transducer and the patient's skin, is essential for achieving accurate targeting. Operators or technicians generally use ultrasound gel spread on the skin and cavity systems filled with degassed water equipped with an elastomeric membrane to create a nearly homogeneous and continuous medium from the surface of the transducer to the patient's skin. Depending on the amount of liquid in the cavity, the elastomeric membrane will inflate and take on the appearance of a balloon or dome, which will be compressed when the operator presses and flattens the transducer against the skin.In case of movement, the operator must maintain contact with the skin that will be covered with gel, and continue to maintain pressure to prevent the formation of air bubbles at the interface between the membrane and the skin.

[0008] Transducers are most often manipulated manually, using passive mechanical arms, or 3D-printed mounts attached directly to the patient. These procedures do not allow for the full exploitation of the spatial precision potential offered by FUS. It would therefore be desirable in this context to be able to maintain good quality acoustic contact in a virtually constant manner over time, particularly throughout the entire duration of a usage phase, and also, if possible, to obtain positioning accuracy consistent with the spatial accuracy achievable by FUS, i.e., on the order of 3 to 4 mm of error on average, while avoiding the use of an MRI or other imaging device.

[0009] US patent 10874871 already discloses, in the context of TMS, a device for applying a stimulation coil mounted on a robotic arm and comprising a resistive sensor in the form of a pressure-sensitive plate interposed between the robotic arm and the transducer. This known solution cannot be used with an ultrasound transducer because the sensor in contact with the skin would disrupt the transmission of the ultrasound waves. By placing the sensor upstream of the transducer, i.e., between the robot and the rear face of the transducer, to overcome the aforementioned drawback, the pressure measurement is then disrupted by the tension forces created by the transducer's power cable and by gravity. Thus, reliable operation cannot be guaranteed in all positions, which significantly reduces its usefulness.

[0010] The present invention aims to overcome these drawbacks and to overcome the aforementioned limitations.

[0011] To this end, it relates to an ultrasound application device or head intended to be mounted on a robotic arm and comprising a focused ultrasound transducer and a means for measuring a contact pressure between said device and a region of the skin of a subject against which said device rests, said device also comprising, at the level of the active face of the transducer intended to be directed towards the skin of the subject, an acoustic coupling interface for the transmission of waves from the transducer to the skin upon contact with the latter,

[0012] device characterized in that the coupling interface comprises a closed enclosure containing a substantially incompressible liquid, such as a gel or a degassed liquid, and having a flexible wall, forming the part of the device intended to come into contact with the skin, and in that said enclosure is in direct fluidic connection or contact with a pressure sensor, forming a means of measuring contact pressure and forming part of said device.

[0013] The invention will be better understood from the following description, which relates to preferred embodiments, given by way of non-limiting examples, and explained with reference to the accompanying schematic drawings, in which:

[0014] [Fig.1] is a perspective and top view of an ultrasound application device according to a first embodiment of the invention (only the transducer and the coupling interface are shown, the pressure sensor and associated electronics are not shown);

[0015] [Fig.2A], [Fig.2B] and [Fig.2C] are cross-sectional views respectively along the planes AA, BB and CC of the ultrasound application device shown [Fig.1];

[0016] [Fig.3] is a schematic lateral elevation view of an ultrasound application device according to a second embodiment of the invention (the pressure sensor and associated electronics being represented symbolically);

[0017] [Fig.4A] is a side elevation view of a first embodiment of the ultrasound application device shown [Fig.3] (only the transducer and the coupling interface are shown, the pressure sensor and associated electronics are not shown);

[0018] [Fig.4B] is an exploded perspective view of the ultrasound application device shown [Fig.4A] and [Fig.4C] is a cross-sectional view along DD of the ultrasound application device shown [Fig.4A] of the transducer and the coupling interface forming part of the device shown [Fig.4A];

[0019] [Fig.5A] is a perspective view of another variant embodiment of the device shown in figures 3 and 4 and [Fig.5B] is an exploded perspective view of the device shown [Fig.5A];

[0020] [Fig.6] is a schematic representation of a robotic installation for the transcranial application of focused ultrasound, according to an embodiment of the invention, comprising an ultrasound application device according to the first embodiment of the invention;

[0021] [Fig.7] is a flowchart illustrating the operational steps of the pressure control process for the position of an ultrasound application device according to the invention;

[0022] [Fig.8] is a schematic representation of a robotic installation for the transcranial application of focused ultrasound, according to an embodiment variant of the invention in relation to a semi-automatic processing method;

[0023] [Fig.9] is a flowchart illustrating the operational steps of a semi-automatic process of treatment by transcranial focused ultrasound applied by means of an ultrasound application device as shown in one of the figures 1 to 5 and implementing the installation of the [Fig.8];

[0024] [Fig. 10] is a schematic representation of a robotic installation for the transcranial application of focused ultrasound, according to an embodiment of the invention in relation to an automatic processing method, and,

[0025] [Fig. 11] is a flowchart illustrating the operational steps of an automatic process of treatment by transcranial focused ultrasound applied by means of an ultrasound application device as shown in one of the figures 1 to 5 and implementing the installation of the [Fig.10].

[0026] Figures 1 to 5 illustrate, according to a first aspect of the invention, an ultrasound application device or head (1) intended to be mounted on a robotic arm (1') and comprising a focused ultrasound transducer (2) and a means (3) for measuring contact pressure between said device (1) and a region (4') of the skin (4) of a subject against which said device (1) is placed. This device (1) also comprises, at the level of the active face (2') of the transducer (2) intended to be directed towards the skin (4) of the subject, an acoustic coupling interface (5) for the transmission of waves from the transducer (2) to the skin (4) upon contact with the latter.

[0027] According to the invention, the coupling interface (5) comprises a closed enclosure (6) containing a substantially incompressible liquid, such as a gel or a degassed liquid (7), and having a flexible wall (8), forming the part of the device (1) intended to come into contact with the skin (4), and said enclosure (6) is in direct fluidic connection or contact with a pressure sensor (3), forming a means for measuring contact pressure and forming part of said device (1).

[0028] Thanks to these arrangements, the device (1) directly and as closely as possible measures the effective contact pressure of the transducer (2) on the skin (4) through the coupling interface (5) and provides a real and reliable measurement usable in a robotic application. Thus, said device (1) performs a dual function, acting as both an ultrasound applicator and a pressure detector, the two being constructively and functionally integrated. Furthermore, a reliable measurement can be guaranteed regardless of the position or orientation of the device (1).

[0029] Advantageously, the pressure sensor (3) is connected to the enclosure (6) by a semi-rigid hydraulic link (9), simultaneously forming a fluidic link and a support link for said sensor (3), the latter being arranged as close as possible to the enclosure (6).

[0030] In accordance with a first embodiment, shown in Figures 1 and 2, the device (1) includes a support body (10) for the transducer (2), which defines a chamber (11) around and above the active face (2'), this chamber (11) being closed by the flexible wall (8), for example an elastic membrane in a compatible material such as latex, silicone or an elastomer, and forming with the latter the closed enclosure (6).

[0031] According to one possible practical construction of the invention, illustrated in Figures 1 and 2, the support body (10) comprises two constituent parts (12, 12') which, by cooperation, form a housing (13) for receiving the transducer (2) in order to its maintenance, namely, a first part (12) with means or a site (13') for attachment to a robotic arm (1') and a second part (12') laterally delimiting the chamber (11) and integrating fluid passages (14, 14', 14") opening into the chamber (11) and extending externally by connecting pipettes, for example two passages (14, 14') for filling or degassing the chamber (11) and one passage (14") for connecting the fluid link (9) with the pressure sensor (3).

[0032] As these figures also show, the flexible wall (8) is attached and held in a sealed manner around its periphery against the second constituent part (12'), to close the chamber (11) opposite the transducer (2), by means of a perforated piece (15) forming a cover or ring, said flexible wall (8) extending through this perforated piece (15), under the pressure of the liquid or gel, forming a dome. The flexible wall (8) and the perforated piece (15) are preferably dimensioned so that the bearing area has a diameter of approximately 60 to 80 mm.

[0033] According to a second embodiment, shown in Figures 3 and 4, the closed chamber (6) is in the form of a sealed, flexible-walled pouch (8), substantially lens-shaped and filled with gel, mounted in a concave recess (17) of the active face (2') of the transducer (2) and held peripherally in this recess (17) by a perforated cover or a ring (17'), which also advantageously constitutes a means of gripping the pouch, the pressure sensor (3) being located in the sealed pouch (8) or outside of it, with the fluidic connection in the form of a semi-rigid connection (9) possibly formed as a single piece with said pouch (6). The wall of the pouch (6) is also made, for example, of latex, silicone, or an elastomer.

[0034] An additional layer of gel (18), in the form of a block for example, can be attached to the pouch (6), for example by being attached in a removable manner to the ring (17') by clips (17”) or the like.

[0035] This layer (18) acts as a cushion to dampen the contact and move the transducer away if necessary.

[0036] In the two aforementioned variants, the semi-rigid connection (9) advantageously supports a pressure of up to 2 bars without elastic deformation.

[0037] The pressure sensor (3) is advantageously a micro-pressure sensor mounted on a printed circuit board and associated with electronics (3') and reading software for determining the pressure at regular intervals, for example on the order of milliseconds. A non-limiting example of such a sensor is that known under the designation MPR (MPRLS0300YG00001B) by Honeywell.

[0038] The invention also relates, as schematically illustrated in figures 6, 8 and 10, to a robotic installation (1”) for the application of focused ultrasound, automatically or semi-automatically, to the body of a subject.

[0039] This installation (1”) essentially comprises a robotic arm (1') with at least three axes or degrees of freedom, advantageously five or six, an ultrasound application device (1) mounted at the end of this robotic arm (1'), a command / control system (19) for said robotic arm (1'), a system (20) for optically or magnetically locating and tracking the position and orientation of a part of the subject's body or head (4”) and the robotic arm (1') and for compensating for head movements (4”) in cooperation with the aforementioned command / control system (19), a system (21) for supervising and controlling the installation (1”) which is associated with human-machine interface means and which coordinates the operation of the various constituent components (1, 1', 19, 20) of the installation (1”), and, optionally, a navigation system (22) for implementation of a planned treatment protocol,with at least one target defined in a medical image of at least one part of the body or head (4”) of the subject in question or by coordinates in a virtual anatomical model.

[0040] In accordance with the invention, the ultrasonic application device (1) is a device as described above, the pressure in the closed chamber (6) containing a substantially incompressible liquid being adjusted during manufacture or at the start of use of said device (1) to a rest value corresponding to a zero contact pressure level. The measurement therefore relates to differential pressure values ​​(relative to this set value).

[0041] The pressure sensor (3) remote by a hydraulic link (9) provides a relative measurement of the force directly applied by the robotic arm (1') in order to achieve sufficient acoustic coupling for the transmission of ultrasonic waves between the transducer and the skin (4), while avoiding excessive pressure.

[0042] An initial pressure value or calibration pressure defines a "zero" pressure level, from which a differential pressure is measured and used by the control system (19) for the robotic arm (1'). This value is defined at rest, once the pouch (6) is correctly positioned, or when the operator judges that the pressure causing the membrane (8) of the chamber (11) to inflate is sufficient for the chosen application point on the skin (4).

[0043] By way of example, the "zero" pressure level can be approximately 20 mbar for a flexible latex wall (8) 150 microns thick (65 mm diameter) and an operating range of the device (1), as a pressure measuring sensor, up to approximately 200 mbar. In this case, the setpoint or reference pressure (for the control process) can be located in a range of the order of 50 to 100 mbars for example.

[0044] Thanks to such a construction and such an operation of the device (1), a pressure is measured in the enclosure (6) and therefore inside the acoustic coupling interface (5) and thus directly the differential support pressure in contact with the skin (4).

[0045] The invention further relates to a method of pressure control of the position of an ultrasound application device (1) as described above, brought into contact under pressure with the skin (4) of a subject and carried by a robotic arm (1'), which advantageously forms part of a robotic installation (1”) as previously mentioned, in order to maintain the contact pressure of the device (1) with the skin of the (4) of the subject within a range of setpoint values.

[0046] This control method, illustrated by way of example in [Fig.7], is characterized in that it comprises the steps of measuring the contact pressure at regular intervals, advantageously at intervals of a few milliseconds, for example 4 ms, and converting the measured pressure value into an intensity level by comparison to threshold values, for example using a graduated scale with at least five intensity levels; comparing the current intensity level to a predefined reference value or to a range of reference values;depending on the result of the previous comparison, to maintain the current position of the device (1) or to move the device (1) so as to advance or retreat it relative to the skin (4) of the subject in order to increase or decrease the contact pressure, the direction of movement being perpendicular to the active face (2') of the transducer (2) and the speed of movement of the device (1) being advantageously modulated, in particular according to the direction of movement; to repeat the previous operations for a determined period, corresponding for example to the duration of a treatment protocol.

[0047] Thus, thanks to the direct measurement of the contact pressure with the device (1) an automatic and reactive control, aimed at maintaining a contact at limited pressure but of sufficient quality, can be obtained.

[0048] Advantageously, the servo method consists, in a preliminary phase, of aligning the ultrasound application device (1) above or opposite the targeted contact area (4') of the subject's skin (4), which depends on the target in question, either automatically via a supervisory and control system (21) functionally connected to a control system (19) for the robotic arm (1'), or manually by an operator; then engaging the pressure servo to bring the ultrasound application device (1) into controlled contact with the skin (4) and issuing a notification when a contact pressure intensity setpoint is reached. predetermined is checked, to indicate that the contact region (4') is contacted in accordance with predefined conditions.

[0049] In order to make the control method both safer and more adaptable to the circumstances of use, it may consist of modulating the speed of movement of the ultrasound application device (1), to advance or retreat it relative to the skin (4) of the subject, in order to increase or decrease the contact pressure, depending on the difference in pressure intensity levels between the measured pressure and the set pressure, by implementing a fuzzy logic type calculation algorithm with the aforementioned difference in levels as input variable and the aforementioned speed of movement as output variable, the speed of advance being preferentially reduced compared to the speed of retreat for the same absolute value of difference in level.

[0050] In order to be able to take into account and compensate for larger movements at the level of the subject, the servo method may further consist of carrying out, by means of a suitable tracking, monitoring and compensation system (21), cooperating with a control system (19) for the robotic arm (1'), optical or magnetic tracking of the position and orientation of the body part or head (4") of the subject, on the one hand, and of the robotic arm (1'), on the other hand, as well as compensation of the movements of the head (4") of the subject, with cyclic repetition, for example at a frequency between 10 and 120 Hz,by providing and exploiting at each repetition period of the aforementioned operational cycle the position of at least one marker (16) attached to a body part or the head (4”) or a point cloud of at least one relevant surface region of the body part or head (4”) and the position of the ultrasound application device (1) or the robotic arm (1”) carrying it, making it possible to detect any relative movement between the body part or head (4”) and the device (1), and, if necessary, to perform a near real-time realignment of said device (1) using the same relative displacement and / or rotation with respect to the initially targeted area, while maintaining by servo control the contact of the device (1) with the skin of the subject (4) with a pressure within a range of setpoint values, preferably a predetermined range.

[0051] In order to also take into account and manage situations of loss of contact, the servo method may consist, in the event of a break in contact between the ultrasound application device (1) and the skin (4) of the subject, of temporarily modulating the speed of movement of the ultrasound application device (1) according to the time elapsed since the last detected contact, and, based on the speed obtained, of performing a translational movement of the device (1) by numerical integration at each repetition period of an operational cycle, using a time law with limited acceleration, for example of the velocity trapezoid type, so as to arrive at a new setpoint position for the ultrasound application device (1) at each period.

[0052] A practical example of a method for controlling a robotic arm (1'), of the 5-axis or more type, which allows control that the pressure of an ultrasound application device (1) in contact with the skin remains within a setpoint range, will be described in more detail below.

[0053] The pressure value from the sensor (3) integrated into the device (1) is read digitally and periodically every 4 ms, then converted into an intensity level using thresholds. At level 0, the pressure is the non-contact pressure, defined during an initial zeroing or calibration step. Then, relative to this initial value, thresholds are defined to obtain a gradual scale from 0 to 'N', in terms of pressure intensity steps. Advantageously, a minimum of 5 intensity steps are provided, from 0 to 4, but it is possible to configure more intensity steps. Level 0 corresponds to a zero pressure difference (no contact), the higher levels correspond to higher pressures (the threshold levels can be configured).

[0054] Depending on the measured pressure intensity, the robotic arm (1') control / command system (19), possibly in conjunction with the installation (1") monitoring and control system (21), compares the current value to a reference intensity value, for example level 2, and determines whether the robotic arm (1') should move forward or backward to increase or decrease the pressure. If the intensity remains within the setpoint, the position is maintained at the current position.

[0055] The movement forward or backward (relative to part 4'' of the subject) is performed at a speed modulated by the difference in pressure intensity level, according to fuzzy logic where the difference in level is the input variable, and the speed of movement is the output variable. The speed of movement varies depending on whether one is moving forward or backward, and whether the value of the difference in level is large. In particular, the fuzzy logic calculation means (integrated into one of the systems 19 or 20) will favor a slower approach speed than the retreat speed. Furthermore, the fuzzy logic calculation means advantageously incorporate an anti-rebound system that will temporarily modulate the speed of movement, depending on the time elapsed since the last detected contact, thus acting as a shock absorber.Based on the calculated velocity, the robotic arm (1') control system (19) will command a translational movement of said arm by numerical integration at each period, using a limited acceleration time law of the velocity trapezoid type. This process makes it possible to generate a new setpoint position for the robot at each period of the cyclic servo method of the invention.

[0056] The axis of movement of the ultrasound application device (1) mounted at the end of this robotic arm (1') is linear in a Cartesian coordinate system attached to said arm, and corresponds to a direction normal to the active face (2') of the transducer (2): the movement along this axis brings the device (1) into contact with the skin when the robotic arm moves forward, or moves it away from the skin when it moves backward. The calculation of the Cartesian position to be reached at each period is converted into a position at the joints of the robotic arm (1') by the control system (19) of the robotic arm. The robotic arm advantageously has at least 5 degrees of freedom (3 translations, 2 rotations) and therefore at least 5 axes to ensure that any orientation and direction of translation is possible.

[0057] Before initiating pressure control, the robot's control system performs an alignment movement over the target and its associated contact area (4'). This movement can be performed either automatically, for example, by the system (21) for monitoring and controlling the installation (1"), such as a computer with a processing plan and a sensor to locate the target in space, or manually, in which case an operator positions the device (1) over the target. The pressure control process is then initiated, bringing the device (1) into contact with the skin area (4') and ensuring that it remains in position until the target moves or the operator stops the control. When the set pressure intensity is reached, and the target does not change, the process notifies the operator or the monitoring system (21).

[0058] The invention also relates, as schematically illustrated in Figures 8 and 9, to a semi-automatic method of treating a part (4”) of a subject’s body by focused ultrasound applied by means of an ultrasound application device (1) as described above, in particular the head of a patient, by implementing an installation (1”) of the type mentioned above and a method of position control of an ultrasound application device (1) also described above.

[0059] In this semi-automatic method, the ultrasound application device (1) carried by the robotic arm (1”) is manually brought to a short distance, for example a few centimeters, above the target skin area (4'), and said method then consists of recording the position of the device (1) and the head or part (4”) when the target area (4') is validated, activating the optical or magnetic tracking system for the position and orientation of the subject's head or part (4”) and the robotic arm (1') and compensating for the movements of the subject's head or part (4”), as well as the method for pressure-controlled position control of an ultrasound application device (1) and a protocol for applying ultrasound by said device (1), and allowing the treatment to proceed according to a pre-established protocol with a cyclical repetitive check of the relative positioning between device (1) and head or part (4”) of the subject, followed where appropriate by a phase of realignment or readjustment of said device (1), and possibly repeating these operations for at least one other target region.

[0060] An example of a practical implementation of this semi-automatic method of processing a part (4”) of a subject’s body, more particularly the head, which implements i) a manual positioning of the device (1) above a transcranial target and ii) a system (20) for optical or magnetic tracking and monitoring of the position and orientation of the head (4”) of the subject in question, enabling the detection of the subject’s head movements and the automatic compensation of these movements while maintaining contact, is described below.

[0061] The position and orientation of the subject's head are measured at a frequency of 10 Hz to 120 Hz by the optical or magnetic tracking system (20), which provides either the position of a marker (16) attached to the head and directly detectable by the tracking system (optical or magnetic markers), or directly the 3D position of the face or a point cloud of the head's surface, which serves as a surface model for the tracking system. The same tracking system (20) also determines the position of the robotic arm (1') using a marker (16) placed near the robotic arm (1') in order to calculate positions in the coordinate system attached to the latter.

[0062] At each acquisition period, the tracking system (20) provides the position of the marker (16) or the point cloud in its internal coordinate system and in the coordinate system of the robotic arm (1'), which allows a relative displacement to be deduced. The accuracy of the tracking system (20) is advantageously less than one millimeter. To filter measurement noise, an averaging system can be implemented.

[0063] The targets to be treated are, for example, located using a mark on a cap placed on the head, or directly from anatomical distance measurements. The operator points to the target by manually placing the robotic arm (1') a few centimeters above the contact region associated with it, and the systems (20 and 21) record the position of the robotic arm (1') and the position of the head (4'”) at the moment the operator validates the target.

[0064] Then the pressure control method for bringing and maintaining contact is activated, which brings the device (1) against the skin (4) of the subject along a descent axis perpendicular to the active face (2') of the transducer (2).

[0065] If a significant relative displacement or rotation of the head is detected by the tracking system (20), the command and control system (19) will realign the position of the robotic arm (1') in real time by performing the same relative translational or rotational movement on the initially pointed target, while maintaining contact through pressure control. An adjustable threshold filters out noise. of the tracking system (20) and to prevent the robotic arm (T) from moving continuously. Typical tolerance threshold values ​​are 1 mm in translation or 1 degree in rotation.

[0066] The target is indicated as hit when contact with the associated contact region is established and the position is stable, without movement, for a given time, for example 0.5s.

[0067] Finally, the invention also relates, as schematically illustrated in Figures 10 and 11, to an automatic method for treating a part (4”) of a subject’s body by focused ultrasound applied by means of an ultrasound application device (1) as described above, in particular the head of a patient, by implementing i) an installation (1”) of the type mentioned above, and including in particular a navigation system (22) for the implementation of a planned treatment protocol, and ii) a method for position control of an ultrasound application device (1) also described above.

[0068] In this automatic processing method, during a preliminary phase, at least one target is defined in a medical image of the head or part (4”) of the subject in question or by coordinates in a virtual anatomical model, then the medical image of the head or part (4”) is located relative to the head (4”) and the reference point of the robotic arm (1’) and the reference point attached to the head (4”) are correlated.

[0069] Said method then consists of activating the optical or magnetic tracking system of the position and orientation of the head or part (4”) of the subject and the robotic arm (1') and of compensating for the movements of the head or part (4”) of the subject, as well as the aforementioned method of pressure servo control of the position of an ultrasound application device (1) and a predetermined protocol for the application of ultrasound by said device (1), allowing the treatment to proceed under the control of the navigation system (22) with cyclical repetitive control of the relative positioning between device (1) and head or part (4”) of the subject, followed where appropriate by a realignment or readjustment phase of said device (1), and possibly repeating these operations for at least one other target region.

[0070] A practical embodiment of this automated method for treating a part (4”) of a subject's body, more specifically the head, is described below. This automated method implements i) control of the installation (1”) by a navigation system including treatment planning and target definition in an MRI or CT scan of the patient's head, or on an anatomical atlas model with generic coordinates (such as Talairach) and ii) at least one optical or magnetic tracking and monitoring system (20) for the position and orientation of the subject's head (4”), enabling the detection of head movements and the automatic compensation of these movements while maintaining contact.

[0071] The targets are stored in a treatment plan which is recorded on a medium readable by the robotic arm control system (1') or the navigation system. The initial coordinates of the treatment targets can be expressed in an anatomical atlas model, or directly in the image.

[0072] In this method, a preliminary registration step is necessary to locate the position of the MRI or CT scan image of the head relative to the subject's actual head. This step can be performed manually by pointing and measuring the head surface with the optical or magnetic tracking system (20), or automatically using a 3D point cloud measurement system. The same optical or magnetic measurement system is used to obtain the position of a marker (16) placed near the base of the robotic arm, in order to convert the coordinates between the robotic arm's reference frame (1') and the reference frame attached to the subject's head (4").

[0073] Once the registration has been performed, a position on the subject's actual head can be expressed both in the imaging or in the anatomical atlas model, and also in the coordinate system of the robotic arm (1'). Conversely, the targets of the treatment plane are converted into actual coordinates on the subject's head (4").

[0074] The implementation is then carried out directly from the piloting system which communicates with the control system (19) of the robotic arm (1') and can automatically move the robotic arm (1') over a target contained in the processing plane.

[0075] The control system also measures the relative displacements of the head and the target. If the translational displacement and / or rotation is significant, the control system will realign the position of the robotic arm (1') in real time using the new target coordinates. At the end of the process, the robotic arm (1') is automatically returned to its resting storage position.

[0076] Of course, the invention is not limited to the embodiments described and shown in the accompanying drawings. Modifications remain possible, particularly with regard to the composition of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

Demands

1. Ultrasound application device or head (1) intended to be mounted on a robotic arm (1') and comprising a focused ultrasound transducer (2) and a means (3) capable of measuring a contact pressure between said device (1) and a region (4') of the skin (4) of a subject against which said device (1) is pressed, said device (1) also comprising, at the level of the active face (2') of the transducer (2) intended to be directed towards the skin (4) of the subject, an acoustic coupling interface (5) for the transmission of waves from the transducer (2) to the skin (4) upon contact with the latter, device (1) characterized in that the coupling interface (5) comprises a closed enclosure (6) containing a substantially incompressible liquid, such as a gel or a degassed liquid (7), and having a flexible wall (8), forming the part of the device (1) intended to come into contact with the skin (4),and in that said enclosure (6) is in direct fluidic connection or contact with a pressure sensor (3), forming a means for measuring contact pressure and forming part of said device (1).

2. Ultrasonic application device or head (1) according to claim 1, characterized in that the pressure sensor (3) is connected to the enclosure (6) by a semi-rigid hydraulic link (9), simultaneously forming a fluidic link and a support link for said sensor (3), the latter being arranged as close as possible to the enclosure (6).

3. Ultrasonic application device or head (1) according to claim 1 or 2, characterized in that it comprises a support body (10) for the transducer (2), which defines a chamber (11) around and above the active face (2'), this chamber (11) being closed by the flexible wall (8), for example an elastic membrane made of a compatible material such as latex, silicone or an elastomer, and forming with the latter the closed enclosure (6).

4. Ultrasonic application device or head (1) according to claim 3, characterized in that the support body (10) comprises two constituent parts (12, 12') which, by cooperation, form a housing (13) for receiving the transducer (2) for its retention, namely, a first part (12) with means or a site (13') for attachment to a robotic arm (1') and a second part (12') delimiting laterally the chamber (11) and incorporating fluid passages (14, 14', 14") opening into the chamber (11) and extending externally by connecting pipettes, for example two passages (14, 14') for filling or degassing the chamber (11) and one passage (14") for connecting the fluid link (9) with the pressure sensor (3).

5. Ultrasonic application device or head (1) according to claim 4, characterized in that the flexible wall (8) is attached and held in a sealed manner peripherally against the second constituent part (12'), to close the chamber (11) opposite the transducer (2), by means of a perforated piece (15) forming a cover or ring, said flexible wall (8) extending through this perforated piece (15) under the pressure of the liquid or gel by forming a dome.

6. Ultrasonic application device or head (1) according to claim 1 or 2, characterized in that the closed enclosure (6) is in the form of a sealed, flexible-walled pouch (8), substantially lens-shaped and filled with gel, mounted in a concave recess (17) of the active face (2') of the transducer (2) and held peripherally in this recess (17) by a perforated cover or a ring (17'), which also advantageously constitutes a means of gripping the pouch, the pressure sensor (3) being located in the sealed pouch (8) or outside the latter, with the fluidic connection in the form of a semi-rigid connection (9) possibly formed in one piece with said pouch.

7. Ultrasonic application device or head (1) according to claim 6, characterized in that an additional layer of gel (18) is applied to the pouch (6), for example by being removably attached to the ring (17') by clips (17”) or the like.

8. A robotic installation (1”) for the automatic or semi-automatic application of focused ultrasound to the body of a subject, said installation (1”) essentially comprising a robotic arm (1') with at least three axes or degrees of freedom, an ultrasound application device (1) mounted at the end of this robotic arm (1'), a command / control system (19) for said robotic arm (1'), a system (20) for optically or magnetically locating and tracking the position and orientation of a part of the subject's body or head (4”) and the robotic arm (1') and for compensating for movements

9. of the head (4”) in cooperation with the aforementioned command / control system (19), a system (21) for supervising and controlling the installation (1”) which is associated with human-machine interface means and which coordinates the operation of the various constituent components of the installation (1”), and, optionally, a navigation system (22) for the implementation of a planned treatment protocol, with at least one target defined in a medical image of at least one part of the body or head (4”) of the subject concerned or by coordinates in a virtual anatomical model, installation (1”) characterized in that the ultrasound application device (1) is a device according to any one of claims 1 to 7, the pressure in the closed enclosure (6) containing a substantially incompressible liquid being adjusted at the manufacture or at the start of use of said device (1) to a resting value corresponding to a zero contact pressure level. A method for pressure-controlled position control of an ultrasound application device (1) according to any one of claims 1 to 7, brought into contact under pressure with the skin (4) of a subject and carried by a robotic arm (1'), which advantageously forms part of a robotic installation (1”) according to claim 8, in order to maintain the contact pressure of the device (1) with the skin of the subject (4) within a range of setpoint values, a method characterized in that it comprises the steps of: measuring the contact pressure at regular intervals, advantageously at intervals of a few milliseconds, for example 4 ms, and converting the measured pressure value into an intensity level by comparison to threshold values, for example using a graduated scale with at least five intensity levels; comparing the current intensity level to a predefined reference value or to a range of reference values;depending on the result of the previous comparison, to maintain the current position of the device (1) or to move the device (1) so as to advance or retreat it relative to the skin (4) of the subject in order to increase or decrease the contact pressure, the direction of movement being perpendicular to the active face (2') of the transducer (2) and the speed of movement of the device (1) being advantageously; modulated, in particular according to the direction of movement; to repeat the previous operations for a determined period, corresponding for example to the duration of a treatment protocol.

10. The method according to claim 9, characterized in that it consists, in a preliminary phase, of aligning the ultrasound application device (1) above or opposite the targeted contact region (4') of the subject's skin (4), which is a function of the target concerned, either automatically via a supervisory and control system (21) functionally connected to a control system (19) for the robotic arm (1'), or manually by an operator; then of engaging the pressure control to bring the ultrasound application device (1) into controlled contact with the skin (4) and of issuing a notification when the contact pressure intensity setpoint is verified, to indicate that the contact region (4') is contacted in accordance with predefined conditions.

11. A method according to claim 9 or 10, characterized in that it consists of modulating the speed of movement of the ultrasound application device (1), to advance or retreat it relative to the skin (4) of the subject, in order to increase or decrease the contact pressure, as a function of the difference in pressure intensity levels between the measured pressure and the setpoint pressure, by implementing a fuzzy logic type calculation algorithm with the aforementioned difference in levels as input variable and the aforementioned speed of movement as output variable, the speed of advance being preferably reduced compared to the speed of retreat for the same absolute value of difference in level.

12. A method according to any one of claims 9 to 11, characterized in that it consists of achieving, by means of a suitable tracking, monitoring and compensation system (21) cooperating with a robotic arm control system (19) for commanding / controlling the robotic arm (1'), optical or magnetic tracking of the position and orientation of the body part or head (4") of the subject, on the one hand, and of the robotic arm (1'), on the other hand, as well as compensation of the movements of the body part or head (4") of the subject, this with cyclic repetition, for example at a frequency between 10 and 120 Hz, by providing and exploiting at each repetition period of the aforementioned operational cycle the position of at least one marker (16) attached to the body part or head (4”) or a point cloud of at least a relevant surface region of the body part or head (4”) and the position of the ultrasound application device (1) or robotic arm (1”) carrying it, enabling the detection of any relative movement between the body part or head (4”) and the device (1), and, if necessary, to proceed with a near real-time realignment of said device (1) using the same relative displacement and / or rotation(s) with respect to the initially targeted area, while maintaining by servo control the contact of the device (1) with the skin of the subject (4) with a pressure within a range of setpoint values.

13. A method according to any one of claims 9 to 12, characterized in that it consists, in the event of a break in contact between the ultrasound application device (1) and the skin (4) of the subject, of temporarily modulating the speed of movement of the ultrasound application device (1) according to the time elapsed since the last contact detected, and, on the basis of the speed obtained, of carrying out a translational movement of the device (1) by numerical integration at each repetition period of an operational cycle, using a time law with limited acceleration, for example of the velocity trapezoid type, so as to arrive at a new setpoint position for the ultrasound application device (1) at each period.

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