Method and system for detecting acoustic coupling failure between an ultrasound device and tissue to be treated

Abstract

The invention relates to a device for treating a pathology, comprising: - a device (1) for generating ultrasound waves, - a remote control unit (2) for transmitting electrical power to the device (1), - means (31, 32) for electrically connecting the device (1) and the control unit (2), characterized in that the control unit (2) is programmed to evaluate the quality of the acoustic coupling between the ultrasound device (1) and the tissue to be treated.

Description

Technical Field

[0001] This invention relates to the general technical field of ultrasound devices (e.g., in vivo or implantable devices) intended for electrical connection to a remote control unit.

[0002] This device can be implanted in humans and mammals to help practitioners develop diagnostic and / or therapeutic methods for pathologies. Background Technology

[0003] A device for treating brain diseases can be found in document WO 2018 / 007500. (Reference) Figure 1 Such equipment consists of the following components:

[0004] - Ultrasonic device 1, which is made of non-ferromagnetic material.

[0005] - Control unit 2, which is located away from ultrasonic device 1, and

[0006] - A connecting device for connecting the ultrasonic device 1 and the control unit 2.

[0007] The ultrasound device 1 is designed to be positioned within a drill hole formed in the patient's skull. It is advantageously compatible with magnetic resonance imaging (IRM) technology and includes:

[0008] - At least one transducer 12, which is used to generate ultrasound waves for the treatment of brain diseases.

[0009] - Fixation device 13, which is used to fix the transducer 12 in the patient's skull.

[0010] - One (or more) electrical connection terminals 14, which are designed to cooperate with connection devices.

[0011] The control unit 2 is designed to supply electrical power to the ultrasonic device 1 and adjust its operating parameters.

[0012] Connection devices are designed to electrically connect the ultrasound device 1 to the control unit 2. They typically include:

[0013] - One (or more) electrical connection cables 31, one end of which is connected to the control unit, and

[0014] - One (or more) percutaneous needles 32, which are connected to the other end of the cable 31.

[0015] The device operates as follows. Once the ultrasound device 1 is implanted into the patient's skull, it provides a series of treatments to address the pathology affecting the patient. During each new treatment, the ultrasound device 1 is connected to the control unit 2 via a connector.

[0016] The practitioner connects cable 31 to control unit 2, and then inserts needle 32 through the patient's skin into terminal 14 of the ultrasound device.

[0017] Once the end of the needle 32 is connected to the terminal 14, the control unit 2 can be activated to supply power to the ultrasound device 1.

[0018] The detection method described in WO 2018 / 007500 proposes to check the quality of the electrical connection between the ultrasound device 1 and the control unit 2 before performing treatment.

[0019] More specifically, the systems and methods described in WO 2018 / 007500 allow for the detection of different types of defective electrical connections, such as:

[0020] - There is no electrical connection between cable 31 and control unit 2.

[0021] - There is no electrical connection between the percutaneous needle tip and terminal 14.

[0022] Checking the quality of the electrical connection between the ultrasound device 1 and the control unit 2 before performing treatment can limit the risk of treatment ineffectiveness.

[0023] However, other parameters may affect the effectiveness of the treatment, especially the acoustic coupling quality between the ultrasound device 1 and the tissue to be treated.

[0024] One object of the present invention is to provide a method and system that enables practitioners to detect potential faults in the acoustic coupling quality between:

[0025] - Ultrasonic device, and

[0026] - Tissue awaiting treatment.

[0027] Ultrasonic devices may also deteriorate over time. Specifically, the operation of one (or more) transducers may fail, for example if the electrical connection of one (or more) transducers is altered (short-circuited or open-circuited), such as when one (or more) connector is disconnected from one (or more) transducers.

[0028] Another object of the present invention is to provide a method and system that allows practitioners to detect malfunctions in one (or more) transducers of an ultrasonic device. Summary of the Invention

[0029] Therefore, the present invention proposes a device for treating pathological conditions, comprising:

[0030] - An ultrasonic device comprising at least one transducer capable of generating ultrasonic waves, the transducer having a front side designed to be oriented toward a target medium.

[0031] - A remote control unit is used to determine and monitor the operating parameters of the ultrasound device and to supply power to the ultrasound device for at least one treatment cycle, with a waiting period preceding each treatment cycle.

[0032] - An electrical connection device between the ultrasonic device and the control unit.

[0033] It is worth noting that the control unit is programmed to perform an estimation phase of the acoustic coupling quality between the ultrasonic device and the target medium, the estimation phase including:

[0034] - The control unit emits at least one monitoring signal, each monitoring signal having a corresponding frequency.

[0035] - At least one reflected signal is measured by the control unit, and each reflected signal corresponds to a corresponding monitoring signal.

[0036] -Process the reflected signal for detection:

[0037] ○ The presence of liquid in the ultrasonic device

[0038] Alternatively, the presence of a reflective material (e.g., a bubble) between the transducer and at least one transducer and the target medium.

[0039] Preferred, but not limiting, aspects of the present invention are as follows:

[0040] - The estimation phase may include a step of detecting the presence of liquid in the ultrasonic device, which includes the following sub-steps:

[0041] The control unit transmits a leakage current monitoring signal at the leakage current monitoring frequency.

[0042] ○ The reflected leakage current monitoring signal, corresponding to the portion of the leakage current monitoring signal that is not absorbed by the ultrasonic device, is measured by the control unit.

[0043] ○ Process the reflected leakage current monitoring signal to detect the presence of liquid in the ultrasonic device;

[0044] - The leakage current monitoring frequency can be a frequency that is not within the operating frequency range of the transducer. Specifically, for a transducer with an operating frequency of 1MHz, it is approximately a frequency of 600kHz.

[0045] - The estimation stage includes a step of detecting the presence of bubbles, which includes the following sub-steps:

[0046] The control unit transmits a gas monitoring signal at the gas monitoring frequency.

[0047] ○ The control unit measures the reflected gas monitoring signal corresponding to the portion of the gas monitoring signal that is not absorbed by the ultrasonic device.

[0048] ○ Process the reflected gas monitoring signal to detect the presence of bubbles between the transducer and the target medium.

[0049] - The bubble monitoring frequency can be a frequency within the operating frequency range of the transducer, more specifically, a frequency greater than 90% of the transducer's operating frequency, specifically, for a transducer with an operating frequency of 1MHz, approximately 962kHz.

[0050] - A step of detecting the presence of bubbles may be performed on each transducer during at least one waiting period, the step further comprising the following steps:

[0051] ○ Each transducer that did not detect bubbles is activated, and during the waiting period and at least one treatment cycle following at least one waiting period, electrical energy can be supplied to the activated transducers to generate ultrasound therapeutic waves.

[0052] ○ Each transducer that detects bubbles is deactivated, and no electrical energy is supplied to the deactivated transducers during the waiting period and the treatment cycle following at least one waiting period.

[0053] - Each treatment session may include multiple treatment cycles, during which the device emits ultrasound therapeutic waves to the tissue to be treated. A waiting period precedes each treatment cycle, and the control unit is programmed to perform the following:

[0054] ○ The step of detecting the presence of bubbles during each waiting period.

[0055] ○ The procedure for detecting the presence of fluid during each treatment cycle;

[0056] - The steps of detecting the presence of liquid and gas can be performed sequentially, with the step of detecting the presence of liquid performed after the step of detecting the presence of bubbles;

[0057] - The ultrasonic device may include a housing in which each transducer is housed, the housing including a bottom facing the front of each transducer, the bottom being made of polyetheretherketone (PEEK) for the operating frequency of the transducer being equal to 1 MHz, and the thickness of the bottom being between 0.3 mm and 0.8 mm, preferably between 0.3 mm and 0.6 mm, and even more preferably substantially equal to 0.4 mm ± 0.05 mm.

[0058] The estimation phase may include steps to detect the operation of each transducer, specifically short circuits or open circuits. For this purpose, the control unit sends a voltage to each transducer at a frequency F0, which is advantageously zero (DC voltage).

[0059] The present invention also proposes an implantable ultrasound device comprising at least one transducer capable of generating ultrasonic waves, said transducer comprising:

[0060] - At least one electroacoustic element, which is made of piezoelectric material, and

[0061] - A housing comprising a bottom, at least one side wall, and a top wall, the housing forming a sealed enclosure designed to house the electroacoustic element and at least one electroacoustic element.

[0062] It is worth noting that the material forming the bottom of the shell is polyetheretherketone (PEEK).

[0063] Preferred, but not limiting, aspects of the present invention are as follows:

[0064] - The electroacoustic element includes a front side for positioning towards the tissue to be treated and a back side opposite the front side, and the transducer includes a layer for reflecting sound waves, such as an air layer, which extends over the back side of the electroacoustic element.

[0065] It will be understood that when layer A is referred to as “extending above” layer B, layer A may be directly on layer B, or it may be located above layer B and separated from layer B by one or more intermediate layers, the acoustic effect of which is negligible at the transducer’s operating frequency.

[0066] - The front of the electroacoustic component contacts the bottom of the housing;

[0067] It will be understood that when layer A is referred to as being in "contact" with layer B, layer A may be in direct contact with layer B, or may be separated from layer B by one or more intermediate layers whose acoustic effect at the transducer's operating frequency is negligible.

[0068] - The material constituting the sidewall and at least one sidewall, as well as the cover of the shell, is also polyetheretherketone (PEEK);

[0069] - The thickness of the bottom of the shell satisfies the following relationship:

[0070] E 底部 =(V 声音 / 4F 工作 )×(0.8±0.4),

[0071] in:

[0072] -E 底部 The thickness (in mm) corresponding to the bottom of the shell.

[0073] -V 声音 The velocity of sound corresponds to the material at the bottom of the shell, and

[0074] -F 工作 Corresponding to the operating frequency (in MHz) of transducer 12, this operating frequency is selected from the useful frequency band of transducer 12.

[0075] - For an operating frequency of approximately 1 MHz, the thickness of the PEEK base is selected to be between 0.3 mm and 0.8 mm, preferably between 0.3 mm and 0.6 mm, and even more preferably approximately equal to 0.4 mm (±0.05 mm).

[0076] This invention proposes a device for treating pathological conditions, comprising:

[0077] - An ultrasonic device comprising an electronic card and at least one transducer electrically connected to the electronic card, the transducer being capable of generating ultrasonic waves.

[0078] - A remote control unit is used to determine and monitor the operating parameters of the ultrasound device and to supply power to the ultrasound device during at least one treatment cycle, with a waiting period preceding each treatment cycle.

[0079] - An electrical connection device between the ultrasonic device and the control unit.

[0080] It is worth noting that the control unit is programmed to implement a fault detection phase for each transducer of the ultrasonic device, the detection phase including:

[0081] - At least one test signal is emitted by the control unit, and each monitoring signal has a zero frequency.

[0082] -At least one reflection test signal is measured by the control unit.

[0083] -Process the reflection test signal for detection:

[0084] ○ Short circuit in the ultrasonic device

[0085] ○ Or, there is a fault in the electrical connection between the transducer and at least one transducer and the electronic card. Attached Figure Description

[0086] Other advantages and features of the method and system according to the invention will become better apparent from the description of several variations of the embodiments given by way of non-limiting example in the accompanying drawings, wherein:

[0087] - Figure 1 An example of a device for treating brain diseases is illustrated schematically, including an ultrasound device electrically connected to a remote control unit via a connection device (percutaneous needle + cable).

[0088] - Figure 2This is a schematic cross-sectional view of one of the transducers in an ultrasonic device.

[0089] - Figure 3 The absorption spectrum of the electrical power of the therapeutic transducer is shown.

[0090] - Figure 4 This is a schematic diagram of the main steps in a method for estimating acoustic coupling quality.

[0091] - Figure 5 The curve shows the power consumed by each transducer as a function of the frequency of the applied electrical signal for a batch of transducers.

[0092] - Figure 6 This is a schematic diagram of an alternative implementation of a method for estimating acoustic coupling quality.

[0093] - Figure 7 This is a schematic diagram of an alternative implementation of a method for detecting malfunctions in a transducer. Detailed Implementation

[0094] Different examples of systems and methods for estimating acoustic coupling quality will now be described with reference to the accompanying drawings. In these different drawings, equivalent elements are designated by the same reference numerals.

[0095] This estimation system and method enable practitioners to check whether the acoustic coupling between the ultrasound device implanted in the patient and the tissue to be treated has been correctly achieved.

[0096] The estimation system and method will be described below with reference to the apparatus described in document EP 2539021, which is referenced in International Application WO 2018 / 007500.

[0097] However, it will be apparent to those skilled in the art that the systems and methods according to the invention can be implemented with any type of therapeutic device, including implantable or non-implantable devices that acoustically couple to the tissue to be treated.

[0098] 1. Overview

[0099] 1.1. Treatment equipment

[0100] As previously stated, the device includes:

[0101] -Ultrasonic device 1,

[0102] -Control unit 2, and

[0103] - Connecting device.

[0104] The ultrasound device 1 is designed to be implanted into the patient's skull. It includes:

[0105] - Electronic cards, which are suitable for exchanging power supply and monitoring electrical signals with remote control units.

[0106] - Transducer 12, which is connected to an electronic card, the electronic card being used to generate ultrasonic waves, and

[0107] - Connecting terminal 14, which is designed to receive the percutaneous needle 32 of the electrical connection device.

[0108] In the following text, it will be assumed that ultrasound device 1 has been implanted, that is:

[0109] - The ultrasound device 1 has been inserted into the skull opening, so that the transducer extends towards the tissue to be treated.

[0110] - The ultrasound device 1 has been fixed to the periphery of the skull opening by any means known to those skilled in the art (anchor screws, adhesives, etc.), then

[0111] - The patient's scalp and head muscles have been repositioned to cover the ultrasound device 1.

[0112] The remote control unit 2 allows for the supply of electrical power to the ultrasonic device 1, adjustment of the operating parameters of the ultrasonic device 1, and reception of signals reflected by the device. Since such a control unit 2 is known to those skilled in the art, it will not be described in further detail below.

[0113] The connection device allows for the electrical connection between the ultrasound device 1 and the control unit 2. Specifically, the connection device includes:

[0114] - Percutaneous needle 32, which can be inserted into the connection terminal of the ultrasound device.

[0115] - Conductive cable 31, and

[0116] - A connection socket (not shown) that can be inserted into the complementary socket of the control unit 2.

[0117] 1.2. Equipment usage principles

[0118] Such equipment enables the treatment of brain diseases through several courses of treatment prescribed by practitioners.

[0119] In each new treatment session, the practitioner electrically connects the ultrasound device 1 to the remote control unit 2 using a connection device.

[0120] More specifically, the practitioner connects the connector to the remote control unit 2. Then, the practitioner inserts the percutaneous needle 32 into the patient's scalp and guides the end of the needle 32 into the blind hole of the connector terminal 14 to complete the electrical connection between the ultrasound device 1 and the remote control unit 2.

[0121] Once the ultrasound device 1 is connected to the control unit 2, a series of treatment cycles are executed, with a waiting period preceding each treatment cycle.

[0122] During the waiting period, ultrasound device 1 is deactivated for approximately 1 second. This deactivation is performed by not supplying power to ultrasound device 1.

[0123] When the waiting period expires, the treatment cycle is performed. During the treatment cycle, electrical energy is supplied to the ultrasound device 1 by applying an electrical excitation signal to the connection terminal during the treatment period (approximately 25 milliseconds).

[0124] The electrical excitation signal is transmitted by the control unit 2 at the operating frequency of the transducer 12.

[0125] In the context of this invention, "operating frequency" (or "treatment frequency") means the emission frequency of the ultrasonic therapeutic wave emitted by the transducer 12, which also corresponds to the frequency of the electrical excitation signal, enabling the supply of electrical energy to the ultrasonic device.

[0126] The operating frequency is contained within the useful frequency band of the transducer 12 (i.e., the operating frequency range of the transducer). When an electrical signal of a frequency not contained in the useful frequency band is applied to the transducer 12, the transducer 12 does not work (i.e., does not generate ultrasonic waves).

[0127] Advantageously, the transducer 12 can be selected to have maximum efficiency at the operating frequency. Therefore, the operating frequency corresponds to the treatment frequency of the ultrasound waves used to treat the tissue to be treated.

[0128] In response to the application of an electrical excitation signal during the treatment period, the transducer 12 generates ultrasound waves along the direction of the tissue to be treated.

[0129] When the treatment period ends, a new waiting period will be implemented, and so on until the course of treatment is completed.

[0130] 2. transducer

[0131] refer to Figure 2 The diagram shows a partial cross-sectional view of one of the transducers 12 of the ultrasonic device 1.

[0132] Transducer 12 includes:

[0133] - One (or more) electroacoustic elements 121, intended for use in healing (the pulse train is long and at a fixed frequency), and

[0134] - Housing 122, which contains electroacoustic elements.

[0135] 2.1. Electroacoustic components

[0136] Each electroacoustic therapeutic element 121 is made of a piezoelectric material, such as a "composite" (a combination of at least one piezoelectric material with one or more non-piezoelectric materials such as a polymer).

[0137] When the piezoelectric element 121 is of the "composite" type, its acoustic impedance is close to that of the tissue, and a quarter-wave plate is not required, specifically when the device is intended for therapeutic use.

[0138] Each electroacoustic element 121 is fixed to the bottom 1221 of the housing 122, for example by bonding using a thin adhesive layer (whose acoustic effect at the transducer's operating frequency is negligible).

[0139] like Figure 2 As shown, the transducer 12 also includes a reflective layer (or backing) on ​​the back surface 1212 of the electroacoustic element 121, such as one (or more) air layers 123, which (or each) air layer 123 extends over the back surface 1212 of the electroacoustic element 121.

[0140] Therefore, the transducer 12 has no absorbent material on the back side 1212 of the electroacoustic element 121, which is different from acoustic imaging devices (which use a technique called "pulse echo"), in which the back side of each electroacoustic element is covered with absorbent material to prevent the element from resonating for a long time after excitation.

[0141] Finally, the therapeutic transducer emits high energy (specifically due to the duration of the emission), so the temperature must not rise, especially if it is implanted in the patient.

[0142] Therefore, it is undesirable to have absorbent material on the back side of the electroacoustic element 121 of the transducer 12.

[0143] The reader will also understand that the air layer arranged on the back of the electroacoustic element 121 allows for improved energy efficiency of the transducer by reflecting all the acoustic energy generated by the element toward its front.

[0144] In fact, the piezoelectric element 121 includes:

[0145] - Front 1211, facing the tissue to be treated, and

[0146] - Reverse side 1212, which is opposite to front side 1211.

[0147] When electrical energy is supplied to component 121, it converts electrical energy into mechanical energy, and its vibration generates sound waves that can propagate forward and backward through the component.

[0148] The air layer 123 on the back side 1212 of the piezoelectric element acts as a mirror, reflecting waves directed toward the rear of the element 121 along the direction of its front side 1211. Therefore, the loss of some of the mechanical energy generated by the element 121 is avoided.

[0149] 2.2. case

[0150] The housing 122 includes a bottom 1221, sidewalls, and a cover 1222. Advantageously, the material constituting the housing 122 can be polyetheretherketone (hereinafter referred to as "PEEK"). Due to its many advantages, PEEK is particularly suitable for manufacturing implantable devices. PEEK is actually a material that:

[0151] - Highly sealed

[0152] -Biocompatible

[0153] - Electrically insulating, and

[0154] -Stable over time (during immersion).

[0155] exist Figure 2 In the illustrated embodiment, for an operating frequency of approximately 1 MHz, the thickness of the bottom 1221 of the PEEK (facing the front of said (or each) element 121) is selected to be between 0.3 mm and 0.8 mm, preferably between 0.3 mm and 0.6 mm, and even more preferably substantially equal to 0.4 mm (±0.05 mm).

[0156] Of course, the thickness of the bottom layer is chosen as a function of the operating frequency of the transducer 12. Therefore, the thickness selection based on the operating frequency satisfies the following relationship:

[0157] E 底部 =(V 声音 / 4F 工作 )×(0.8±0.4),

[0158] in:

[0159] -E 底部 The thickness (in mm) corresponding to the bottom of the shell.

[0160] -V 声音 The velocity of sound corresponds to the material at the bottom of the shell, and

[0161] -F 工作 Corresponding to the operating frequency (in MHz) of transducer 12, this operating frequency is selected from the useful frequency band of transducer 12.

[0162] This choice of thickness for the bottom 1221 of the housing 122 is contrary to the general knowledge of those skilled in the art, who would choose the thinnest possible bottom thickness so that:

[0163] - The absorption of ultrasonic energy emitted by element 121 is limited by the bottom of housing 122, and

[0164] - Reduce the size of the ultrasound device that can be implanted.

[0165] Conversely, the choice of this bottom thickness 1221 (in the case of a PEEK bottom) is to facilitate the detection of poor acoustic coupling between the ultrasound device 1 and the tissue to be treated.

[0166] In fact, using a PEEK bottom 1221 with a thickness of approximately 0.4 mm (±0.05 mm) allows for easy detection of air bubbles between the transducer 12 and the tissue to be treated. The electroabsorption spectrum varies greatly depending on whether the bottom is in acoustic contact with the gas on one side or with the propagation medium (in this case, the dura mater) on the other.

[0167] The transducer 12 may include a plurality of piezoelectric elements 121 mounted in the same housing 122. Each housing is sealed.

[0168] As an instruction, Figure 3 The absorption spectra of the transducer's electrical power (active power) are shown in relation to the bottom housing 1221 with different thicknesses. The vertical axis of the graph is P. a0 This corresponds to the power absorbed by the transducer for a 250mW incident power. It should be noted that impedance matching is inserted between the transducer and the generator.

[0169] - The first absorption spectrum (denoted as 311 in the case of acoustic coupling with the propagation medium, and as 312 in the case of acoustic coupling with the gas) corresponds to the transducer associated with a PEEK bottom with a thickness of 0.4 mm.

[0170] - The second absorption spectrum (denoted as 321 in the case of acoustic coupling with the propagation medium, and as 322 in the case of acoustic coupling with the gas) corresponds to the transducer associated with a PEEK bottom with a thickness of 0.2 mm.

[0171] - The third absorption spectrum (denoted as 331 in the case of acoustic coupling with the propagation medium and 332 in the case of acoustic coupling with the gas) corresponds to the transducer associated with the zero-thickness PEEK bottom, that is, the shell without a bottom (the front of the transducer is only covered with a layer of parylene).

[0172] from Figure 3The PEEK thickness of 400 μm is clearly visible, thus allowing the acoustic coupling between the transducer 12 and the tissue to be treated to be examined using emissions at different frequencies.

[0173] Therefore, for an operating frequency of approximately 1 MHz, the selection of a PEEK housing 122 with a bottom thickness between 0.3 mm and 0.8 mm, preferably between 0.3 mm and 0.6 mm, and even more preferably substantially equal to 0.4 mm (±0.05 mm) allows for:

[0174] - Increase the bandwidth used for treatment (enabling the use of a wider frequency range and greater robustness to variations) without reducing electroacoustic efficiency.

[0175] - Improve the electrical insulation, biocompatibility and lifespan of ultrasonic devices; in fact, it is well known that lead zirconate titanate (PZT) ceramics are not biocompatible (due to the presence of lead), parylene (which can be used as a protective film to cover each transducer) is porous, and PZT or “composite” type materials drift with humidity over time.

[0176] More generally, the reflected power spectrum (or impedance measurement) can be compared to a reference model or template (composed of minimum and maximum reference value curves). If the curve representing the measured reflected power spectrum is not included in the template, this indicates a fault. The fault (air, connection, short circuit, faulty transducer, etc.) can be defined by looking at the frequencies of the reflected power spectrum outside the template.

[0177] "Incident power" means the power transmitted from control unit 2 to transducer 12. "Active power" means the power consumed by transducer 12 (incident power - reflected power: part is converted into heat, and the other part is converted into ultrasound). "Reflected power" means the power flowing from transducer 12 to control unit 2.

[0178] Similarly, the reflected electrical signal (φ) r The reflected and incident electrical signals (φ0) are defined as the amplitudes of the reflected and incident electrical waves.

[0179] The reader will understand that the active power / reflected power / impedance spectrum can be obtained in several ways, for example:

[0180] ● Continuously transmit linear frequency-modulated test signals or extremely short signals (e.g., within the range of 0.2-1.6 MHz) and perform Fourier analysis.

[0181] ● Alternatively, prudently (which allows for limiting the cost of the relevant electronic equipment), one can wisely choose to emit several test pulses at different frequencies to allow for the detection of several types of faults from a limited number of pulses at different frequencies (e.g., four pulses at four different frequencies).

[0182] 2.3. Advantages related to the above configuration

[0183] The aforementioned transducer configuration (a reflective layer on the back of the piezoelectric element and a PEEK layer on the front of the piezoelectric element) allows for increased ability to distinguish between the presence of air and water on the front of the transducer, i.e., verification of proper coupling when the transducer is implanted. Because the transducer (air + piezoelectric composite + 1 / 4 wave) adapts well to water and its back is undamped, ultrasound waves can only be damped on the front (water / brain coupling). Therefore, the presence or absence of water on the front has a very significant impact on the transducer's impedance.

[0184] The transducer configuration also allows for:

[0185] - Increase the bandwidth of the transducer without reducing electroacoustic efficiency, thereby making its use more flexible;

[0186] - Improve the electrical insulation, biocompatibility and lifespan of the transducer.

[0187] 3. Issues related to the use of treatment equipment

[0188] As previously indicated, the quality of acoustic coupling (between the ultrasound device and the medium containing the tissue to be treated) can vary over time.

[0189] For example, air bubbles may form between the transducer 12 (or one of them) and the tissue to be treated during treatment. Similarly, air bubbles may be trapped between the transducer and the tissue to be treated during the operation of the implanted device. Moreover, bone calcification may form between the transducer and the tissue to be treated over time. The presence of such reflective material (air bubbles or bone growth) between the transducer and the tissue limits the propagation of ultrasound waves generated by the transducer 12 to the tissue to be treated, thereby limiting the effectiveness of the treatment.

[0190] Furthermore, liquid can enter the device 1, for example, during the insertion of the percutaneous needle 32 into the connection terminal 14, which may cause a short circuit (or more specifically, the occurrence of leakage current) and limit the effectiveness of the treatment.

[0191] This is why it is desirable to estimate the acoustic coupling quality between the ultrasound device 1 and the tissue to be treated in order to limit the risk of treatment ineffectiveness.

[0192] In addition, one (or more) transducers may have faults such as short circuits or open circuits (e.g., after one (or more) connection joints are disconnected from one (or more) transducers).

[0193] This is why it is also desirable to test for malfunctions in one (or more) transducers of the ultrasound device in order to limit the risk of treatment ineffectiveness.

[0194] The reader will understand that these two testing phases (i.e., estimation of coupling quality and detection of transducer malfunctions) can be performed independently or jointly. Therefore, in some implementations, the treatment device can be configured as follows:

[0195] - Perform only one type of acoustic coupling quality estimation, or

[0196] - To detect malfunctions in only one (or more) transducers of an ultrasonic device, or

[0197] - Perform both the estimation of acoustic coupling quality and the detection of malfunctions in one (or more) transducers of the ultrasonic device.

[0198] 4. Methods for estimating acoustic coupling quality

[0199] refer to Figure 4 The method for estimating acoustic coupling quality includes the following steps:

[0200] -At least one monitoring signal 411 is emitted by control unit 2.

[0201] -At least one feedback signal from 412 is obtained by control unit 2.

[0202] - Processing the 413 feedback signal to obtain information about the acoustic coupling quality between the ultrasound device 1 and the tissue to be treated, this processing allows:

[0203] ■Activate each transducer 12 whose acoustic coupling quality is higher than the quality threshold.

[0204] ■Disable the use of each transducer 12 whose acoustic coupling quality is below the quality threshold.

[0205] After assessing the acoustic coupling quality, electrical power can be supplied to the activated transducer (during each treatment cycle) to generate therapeutic ultrasound waves directed towards the tissue to be treated. The deactivated transducer itself is not powered by the control device 2.

[0206] Each monitoring signal is emitted with a lower electrical energy compared to the excitation signal (approximately 1% of the energy required for treatment). More specifically, the electrical power of each monitoring signal is such that any ultrasound waves generated by the ultrasound device (in response to the monitoring signal) do not cause any tissue effects.

[0207] To detect the possible presence of one of these factors (i.e., liquid in the ultrasound device and / or gas / bone bubbles between the bottom of the housing and the propagation medium, and / or transducer malfunction), multiple monitoring signals are emitted at a single frequency. For each signal, control unit 2 emits a signal of known amplitude and frequency to device 1. This signal is not perfectly impedance matched; specifically, due to imperfect acoustic matching between transducer 12 and the tissue, a portion of the signal (the feedback signal) is reflected back to the device. Control unit 2 measures the amplitude of this reflected signal and thereby infers the reflectivity. Control unit 2 can also measure the impedance of the circuitry of the implanted ultrasound device, determined by the transducer.

[0208] More specifically, the method includes the following steps for each transducer 12 of the ultrasonic device 1:

[0209] - Apply multiple monitoring signals at multiple frequencies, each monitoring signal having its own frequency.

[0210] - Measure multiple reflectivities of the monitoring signal, each measured reflectivity corresponding to its respective monitoring signal.

[0211] - Compare the reflectivity with a pre-established threshold and estimate the coupling quality between the transducer 12 under consideration and the tissue.

[0212] The reflectivity corresponds to the proportion of the monitoring signal reflected by transducer 12. The reflectivity (B) of the monitoring signal can be defined as the reflected electrical signal (φ). r The ratio between the incident electrical signal (φ0) and the incident electrical signal (φ0):

[0213] B = φ r / φ0.

[0214] In practice, the steps of applying monitoring signals include applying two, three, or four monitoring signals in sequence, each with its own frequency.

[0215] Choose the frequency of the monitoring signal to maximize the differentiation (of problem detection sensitivity) for each of the following four factors:

[0216] Electrical connection faults as described in WO 2018 / 007500

[0217] -The presence of air bubbles between transducer 12 and the tissue to be treated

[0218] - The presence of liquid in the ultrasound device (e.g., at the connection terminal containing the end of the percutaneous needle 32),

[0219] - Transducer malfunction (short circuit or open circuit)

[0220] The frequency selection is based on the following factors in the overall manufacturing of the transducers:

[0221] -Absorption spectrum, and

[0222] - Standard deviation of absorption spectrum.

[0223] Specifically, the frequency of the monitoring signal is selected to maximize the following ratio:

[0224] (average 水 -Kσ 水 ) / (average 空气 +Kσ 空气 ),

[0225] in:

[0226] - "Average", the average of the absorbance measurements of the sample population at the frequency considered.

[0227] - "σ", the standard deviation of the absorbance measurements of the sample population at the frequency under consideration (this standard deviation is explained by slight variations in transducer operation due to manufacturing tolerances).

[0228] - "K" is an integer between 1 and 3.

[0229] The advantage of using different monitoring signals, each with its own frequency (related to the choice of shell bottom thickness), is that it makes the evaluation method highly identifiable of different factors that may degrade coupling quality. In other words, the method according to the invention allows defining whether insufficient coupling quality is due to:

[0230] - Connection failure,

[0231] -The presence of bubbles, or

[0232] -The presence of liquid.

[0233] - A malfunction in one of the transducers.

[0234] Therefore, the nature of the detected problem can be more accurately communicated to the practitioner, enabling them to implement the most appropriate solution to resolve the problem.

[0235] 4.1. frequency

[0236] To identify possible coupling faults that prevent or render treatment ineffective, different monitoring signals at different frequencies are transmitted, each monitoring signal having a frequency different from the treatment frequency F1 (preferably).

[0237] 4.1.1. The frequency of the monitoring signal used for short circuit detection

[0238] Specifically, the monitoring signal used to detect short circuits or parasitic resistance (due to the presence of liquid at the connection terminals) is transmitted at a frequency of F2.

[0239] The frequency F2 is chosen to be much lower than the operating frequency F1, resulting in very low power consumption by the transducer (less than 40% of the incident power).

[0240] More specifically, the frequency F2 is chosen to be outside the useful frequency band of the transducer (i.e., the operating frequency range of the transducer); therefore, the measured reflectivity (at frequency F2) is much less than 1 (i.e., non-zero power consumption), indicating a short circuit due to the presence of liquid in the ultrasonic device.

[0241] Specifically, in one embodiment of the invention, the frequency F2 of the monitoring signal used to detect short circuits or parasitic resistance is substantially equal to 0.6 MHz.

[0242] 4.1.2. The frequency of the monitoring signal used for detecting electrical connection faults

[0243] The monitoring signal used to detect electrical connection faults (see WO 2018007500) is transmitted at frequency F3, which is different from frequency F2.

[0244] The frequency F3 is selected between frequency F2 and operating frequency F1. Specifically, in one embodiment of the invention, the frequency F3 of the monitoring signal used to detect electrical connection faults is approximately equal to 850 kHz.

[0245] Specifically, frequency F3 is chosen such that the power consumed by the transducer is independent of the medium located in front of the transducer. In other words, frequency F3 is chosen such that:

[0246] On the one hand, the power consumed by the transducer is at its maximum (specifically, greater than 40% of the incident power of the monitoring signal applied to the transducer), and makes...

[0247] ○ The power consumed by the transducer when the front of the transducer is in contact with a gas is basically the same as the power consumed by the transducer when the front of the transducer is in contact with a liquid or tissue.

[0248] Therefore, the measured reflectivity (at frequency F3) which is essentially equal to 1 (i.e., zero active power (= consumed power)) indicates the absence of an electrical connection between the ultrasonic device 1 (or one of the transducers 12 of the device 1) and the control unit 2.

[0249] 4.1.3. Frequency of the monitoring signal used to detect bubbles

[0250] The monitoring signal used to detect air bubbles between the transducer and the tissue to be treated is emitted at frequency F4, which is different from frequencies F2 and F3.

[0251] Specifically, the frequency F4 is chosen to maximize the power consumed by the transducer:

[0252] -Minimum is reached when the transducer faces the bubble (if the transmitted power is less than 64% of the incident power, the transducer is considered to be in air; conversely, if the transmitted power is less than 64% of the incident power, the transducer is considered to be in water), and

[0253] - It reaches its maximum when the front of the transducer faces the propagation medium, such as the dura mater, tissue, or liquid.

[0254] The frequency F4 is selected to be higher than frequency F3 and slightly lower (i.e., between 1% and 10%, preferably between 1% and 5%) or equal to the operating frequency F1.

[0255] Specifically, in one embodiment of the invention, the frequency F4 of the monitoring signal used to detect bubbles is substantially equal to 960 kHz (96% of the transducer's operating frequency).

[0256] Therefore, as Figure 5 As shown (which represents the power consumed by a batch of transducers based on the frequency of an applied electrical signal of 250mW), frequencies for different monitoring signals are selected to maximize the distinguishability between different types of faults that may affect the quality of treatment.

[0257] 4.1.4 The frequency of the monitoring signal used to detect transducer malfunctions (DC voltage: F0 = 0)

[0258] The monitoring signal used to detect transducer malfunctions is emitted at zero frequency F0, which gives the monitoring signal a DC voltage.

[0259] Therefore, a DC voltage monitoring signal can be applied to the implanted ultrasound device by the control unit. This zero-frequency F0 monitoring signal enables the detection of:

[0260] - A complete short circuit in the transducer (zero impedance when the transducer is activated),

[0261] - Or a fault in the connection cavity (if liquid is present, the impedance is too low, specifically if the impedance is too low regardless of whether the transducer is controlled or not, regardless of the controlled transducer).

[0262] This test allows for the completion of the test described in point 4.1.1 to detect at frequency F2. Transmitted monitoring signals Short circuit.

[0263] 4.2. Example of implementation of the estimation method

[0264] Now refer to Figure 6 The operational principle of the estimation method is described in more detail. This estimation method enables the detection of:

[0265] - There is air in front of the transmitter.

[0266] Is the transmitter working properly?

[0267] - Is there liquid (e.g., water) inside the ultrasound device?

[0268] In this implementation, some detection steps of the method are performed during each waiting period, and others are performed during each treatment period.

[0269] 4.2.1. Waiting period

[0270] During each waiting period, the method includes:

[0271] - The first step in detecting electrical connection faults, and

[0272] - The second step in detecting the presence of bubbles.

[0273] These first and second steps are performed sequentially for each transducer 12 of the ultrasonic device 1.

[0274] 4.2.1.1. Electrical connection fault

[0275] The first step in detecting electrical connection faults includes the following sub-steps:

[0276] - Transmit the first monitoring signal 401 at the first monitoring frequency F3:

[0277] The first monitoring signal, for example, consists of a pulse signal with a power of 250mW and a duration of 1ms.

[0278] The first frequency is chosen to be equal to 850kHz.

[0279] - Obtain the first reflected monitoring signal corresponding to the portion of the first monitoring signal that was not absorbed by the ultrasonic device: 402

[0280] Acquiring the first reflected signal may include measuring the electrical power of the reflected signal (e.g., by using a directional coupler) or any other information representing the power consumed by the transducer.

[0281] -Process the 403 first reflected monitoring signal to detect connection failure:

[0282] During the processing sub-step, information representing the power consumed by the transducer is extracted from the first reflected signal.

[0283] ○ This information representing the power consumed is compared with a first predefined threshold corresponding to 40% of the power of the first monitoring signal (i.e., 100mW in the case of a 250mW first monitoring signal):

[0284] ■ If the information indicating power consumption is below a first threshold, then transducer 12 is not properly connected to remote control unit 2 (i.e., an electrical connection between the transducer and the control unit is detected to be absent).

[0285] ■ If not, then the electrical connection between the transducer and the control unit under consideration is working properly (i.e., there is no defect in the electrical connection between the transducer and the control unit).

[0286] 4.2.1.2. The presence of gas

[0287] The step of detecting the presence of air bubbles includes the following sub-steps:

[0288] - Transmit the 404 second monitoring signal at the second monitoring frequency:

[0289] The second monitoring signal, for example, consists of a pulse signal with a power of 250mW and a duration of 1ms.

[0290] The second frequency is chosen to be equal to 962kHz.

[0291] -Acquire the second reflection monitoring signal of 405:

[0292] ○Still here, acquiring the second reflected signal may include measuring the signal from the transducer.

[0293] "Absorbed power", or "reflectivity", or impedance, or any other information indicating the power consumed by the transducer.

[0294] -Process the 406 second reflection monitoring signal to detect the presence of liquid in the ultrasonic device:

[0295] The information representing the power consumed by the transducer (extracted from the second reflected signal) is compared with a second predefined threshold corresponding to 64% of the power of the second monitoring signal (i.e., 160mW in the case of a second monitoring signal of 250mW):

[0296] ■ If the information indicating power consumption is below the second threshold, then the medium extending towards the front of the transducer is gas (i.e., air bubbles are detected between the transducer and the tissue to be treated).

[0297] ■ Otherwise, the medium extending towards the front of the transducer is a liquid or tissue (bubbles are not present).

[0298] 4.2.1.3. Detection of transducer malfunctions

[0299] See Figure 7 The steps for detecting operational faults include the following sub-steps:

[0300] - Transmit the 407 test signal at a zero-monitoring frequency.

[0301] - Acquire the 408 reflection test signal, which may include measuring the "power absorbed" by the transducer, or "reflectivity", or impedance, or any other information representing the power consumed by the transducer.

[0302] - Process the 409 reflection test signal to detect transducer malfunctions: Compare information representing the power consumed by the transducer (extracted from the reflection test signal) with a first predefined test threshold and a second predefined test threshold:

[0303] ■ If the information indicating power consumption is below the first test threshold (i.e., zero impedance or impedance too low), the transducer has a short circuit.

[0304] ■ If the information indicating power consumption is higher than the second test threshold (i.e., too high or infinite impedance), then the connection between the transducer and the electronic card is open.

[0305] ■ Otherwise, the transducer is working correctly (no malfunction exists).

[0306] The malfunction detection procedure is performed sequentially on each transducer of the ultrasonic device. Transducers that are found to be malfunctioning are deactivated, while those without malfunctions are activated.

[0307] 4.2.2. Treatment cycle

[0308] During each treatment cycle, the method includes a third step of detecting the presence of fluid in the ultrasound device.

[0309] This detection step is performed before each step of emitting therapeutic ultrasound waves via the ultrasound device. Therefore, the step of detecting the presence of liquid is performed before each step, including supplying electrical energy to the transducer to generate therapeutic ultrasound waves.

[0310] The third step of detecting the presence of liquid includes the following sub-steps:

[0311] - Transmit the 501 third monitoring signal at the third monitoring frequency F2:

[0312] The third monitoring signal, for example, consists of a pulse signal with a power of 500mW and a duration of 100μs.

[0313] The third frequency is chosen to be equal to 600kHz.

[0314] -Measure the third reflection monitoring signal corresponding to the portion of the third monitoring signal that was not absorbed by the ultrasonic device in the 502 measurement.

[0315] - Processing the 503 third reflection monitoring signal to detect the presence of liquid in the ultrasonic device: Compare the information representing the power consumed with a third predefined threshold corresponding to 40% of the power of the third monitoring signal (i.e., 200mW in the case of a 500mW third monitoring signal):

[0316] ○ If the information indicating power consumption is below the third threshold, then the ultrasonic device does not contain any liquid (i.e., there is no short circuit).

[0317] ○ If not, the ultrasonic device contains a liquid that could cause a short circuit.

[0318] Based on the results of the different tests mentioned above, the control unit 2 commands the ultrasound device 1 to emit therapeutic ultrasound waves.

[0319] Specifically, if no short circuit is detected, the control unit 2 provides the ultrasonic device 1 with an activated transducer 12 (the transducer is correctly electrically connected and its front side does not extend towards the bubble) for the absence of a detected coupling fault. This provisioning step includes applying an electrical power supply signal with a power between 7 and 8 watts to each activated transducer for 24 ms.

[0320] As an indication, the table below summarizes the different frequencies of the estimation phase for implementing coupling quality and the detection phase for transducer malfunctions.

[0321]

[0322]

[0323] Table 1: Frequency and Test Table

[0324] The reader will understand that the frequencies and thresholds used to estimate acoustic coupling quality and to detect transducer malfunctions can be:

[0325] - This is the same for all ultrasound devices, or

[0326] - Each ultrasound device is individualized.

[0327] This individualization allows for the consideration of any existing variations in the performance of different transducers, which can be correlated with the manufacturing tolerances of the transducers (such as variations in surface roughness or thickness for each transducer).

[0328] 5. in conclusion

[0329] The above method enables the assessment of the acoustic coupling quality between the ultrasound device and the tissue to be treated. It also enables the detection of any malfunctions in the transducer.

[0330] Therefore, it is possible to limit the risk of treatment ineffectiveness associated with, for example, the following:

[0331] - A bubble between one (or more) transducers and the tissue to be treated, and / or

[0332] - A short circuit in an ultrasonic device caused by liquid leakage at its connection terminals.

[0333] This detection of faults enables practitioners to be alerted, allowing them to implement solutions to correct these faults.

[0334] The reader will understand that many modifications can be made to the invention described above without substantially departing from the new teachings and advantages described herein.

[0335] Therefore, all modifications of this type are intended to be incorporated into the scope of the appended claims.

Claims

1. A therapeutic device for treating a pathology, comprising: - an ultrasound device (1) comprising at least one transducer (12) capable of generating ultrasound waves, said transducer having a front face intended to be positioned facing a target medium, - a remote control unit (2) for determining and monitoring the operating parameters of the ultrasound device (1) and for powering the ultrasound device (1) during at least one treatment period, each treatment period being preceded by a waiting period, - electrical connection means between the ultrasound device (1) and the control unit (2), the control unit (2) being programmed to implement an estimation phase of the quality of the acoustic coupling between the ultrasound device and the target medium, said estimation phase comprising: - the emission by the control unit of at least one monitoring signal, each monitoring signal having a respective frequency, - the measurement by the control unit of at least one reflected signal, each reflected signal corresponding to a respective monitoring signal, - the processing of the reflected signals to detect: o the presence of a liquid in the ultrasound device, o or the presence of a reflecting material between said transducer and the target medium and at least one transducer and the target medium; characterised in that the estimation phase comprises a step of detecting the presence of a liquid in the ultrasound device, said step comprising the following sub-steps: - the emission by the control unit of a leakage current monitoring signal at a leakage current monitoring frequency, - the measurement by the control unit of a reflected leakage current monitoring signal corresponding to the part of the leakage current monitoring signal that is not absorbed by the ultrasound device, - the processing of the reflected leakage current monitoring signal to detect the presence of a liquid in the ultrasound device.

2. The treatment device of claim 1, wherein, Said leakage current monitoring frequency is a frequency that does not belong to the operating frequency range of the transducer, in particular a frequency of approximately 600 kHz for a transducer for which the operating frequency is equal to 1 MHz.

3. The treatment apparatus of claim 1, wherein, The estimation phase comprises a step of detecting the presence of a gas bubble, this step comprising the following sub-steps: - the emission by the control unit of a gas monitoring signal at a gas monitoring frequency, - the measurement by the control unit of a reflected gas monitoring signal corresponding to the part of the gas monitoring signal that is not absorbed by the ultrasound device, - the processing of the reflected gas monitoring signal to detect the presence of a gas bubble between the transducer and the target medium.

4. The treatment apparatus of claim 3, wherein, The gas monitoring frequency is a frequency that belongs to the operating frequency range of the transducer.

5. The therapeutic device of claim 3, wherein, The step of detecting the presence of a gas bubble is implemented for each transducer during at least one waiting period, this step further comprising the following steps consisting in: - activating each transducer for which no gas bubble has been detected, it being possible to supply electrical energy to the activated transducers to generate ultrasound treatment waves during said waiting period and at least one treatment period following the at least one waiting period, - deactivating each transducer for which a gas bubble has been detected, it being not possible to supply electrical energy to the deactivated transducers during the treatment periods following the at least one waiting period.

6. The treatment apparatus of claim 1, wherein, Each course comprises a plurality of treatment periods during which the device emits ultrasound treatment waves towards the tissue to be treated, each treatment period being preceded by a waiting period, the control unit (2) being programmed to implement: - a step of detecting the presence of a gas bubble during each waiting period, - a step of detecting the presence of a liquid during each treatment period.

7. The treatment apparatus of claim 3, wherein, The steps of detecting the presence of a liquid and of a gas are implemented in succession, the step of detecting the presence of a liquid being implemented after the step of detecting the presence of a bubble.

8. The treatment apparatus of claim 1, wherein, The ultrasound device comprises a housing, each transducer being housed in the housing, the housing comprising a bottom facing the front face of each transducer, the bottom being made of polyether ether ketone, the thickness of the bottom being comprised between 0.3 mm and 0.8 mm for an operating frequency of the transducer equal to 1 MHz.

9. The treatment apparatus of claim 1, wherein, The ultrasound device comprises an electronic card, each transducer being electrically connected to the electronic card, the control unit (2) being further programmed to implement a detection phase of an operating fault of each transducer of the ultrasound device, the detection phase comprising: - the emission, by the control unit, of at least one test signal having a zero frequency, - the measurement, by the control unit, of at least one reflected test signal, - the processing of the reflected test signal to detect an electrical connection fault between the electronic card and the transducer.

10. The treatment apparatus of claim 4, wherein, The bubble monitoring frequency is a frequency greater than 90% of the operating frequency of the transducer.

11. The treatment device of claim 10, wherein, The bubble monitoring frequency is a frequency equal to 962 kHz for a transducer having an operating frequency equal to 1 MHz.

12. The treatment device of claim 8, wherein, The thickness of the bottom is comprised between 0.3 mm and 0.6 mm for an operating frequency of the transducer equal to 1 MHz.

13. The treatment device of claim 12, wherein, The thickness of the bottom is equal to 0.4 mm ± 0.05 mm.

14. The treatment apparatus of claim 1, wherein, The ultrasound device comprises an electronic card, each transducer being electrically connected to the electronic card, the control unit being further programmed to implement a detection phase of an operating fault of each transducer of the ultrasound device, the detection phase comprising: - the emission, by the control unit, of at least one test signal having a zero frequency, - the measurement, by the control unit, of at least one reflected test signal, - the processing of the reflected test signal to detect a short circuit between the electronic card and the transducer.

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