Apparatus and method for measuring viscoelasticity of a viscoelastic medium

Abstract

A device (DEV) for vibration controlled transient elastography, in particular for quantifying liver fibrosis is disclosed. The device comprises an ultrasound probe (1) for elastography, the ultrasound probe (1) comprising a probe housing, at least one ultrasound transducer (US) having a symmetry axis (A), a vibrator (VIB) and a force sensor (FS), wherein the vibrator is arranged to cause a movement of the probe housing along the symmetry axis of the ultrasound transducer, the ultrasound transducer being fixed on the probe housing such that the ultrasound transducer does not move relative to the probe housing, and wherein the device comprises a signal generator (9) configured to emit a contact ready signal when a force exerted by the probe on a viscoelastic medium to be measured is greater than a minimum contact force threshold. The signal generator can also be configured to emit a measurement ready signal when the force is greater than a minimum measurement force threshold.

Description

[0001] This application is a divisional application of the invention patent application filed on March 26, 2018, with application number 201880022597.6 and entitled "Apparatus and method for measuring the viscoelasticity of a viscoelastic medium". Technical Field

[0002] This invention relates to an apparatus for measuring the viscoelasticity of a viscoelastic medium (e.g., a human or animal organ). Specifically, the invention can be used to measure the viscoelasticity of the liver, allowing for the quantification of the amount of fibrosis present in the liver. The invention also relates to a method for measuring the viscoelasticity of a viscoelastic medium. Background Technology

[0003] Chronic hepatitis caused by alcohol, virus, or other reasons has a fibrotic effect, which is important for assessing and determining the optimal time to treat hepatitis.

[0004] One of the most reliable and effective techniques for measuring liver stiffness is transient elastography (see, for example, “WFUMB guidelines and recommendations for clinical use of ultrasound elastography part 3: liver” by G. Ferraioli et al., published in Ultrasound in Med. And Biol. 41, 5, 2015).

[0005] The applicant has developed and commercialized a technology called (For example, see the device in patents EP1169636 and EP1531733). This device uses an elastography technique developed by the applicant, called "Vibration-Controlled Transient Elastography" (VCTE), to measure liver stiffness.

[0006] When applying VCTE, the measurement of liver stiffness depends on measuring the propagation speed of the instantaneous shear wave within the tissue.

[0007] To perform the above measurements, a specific probe has been developed. The probe includes at least one electric actuator and at least one ultrasonic transducer mounted at the tip of the probe.

[0008] For example, in In the probe, a vibrator moves an ultrasound transducer, causing it to press against the patient's body. This pulsed motion generates transient shear waves that propagate within the liver. The displacement caused by these propagating shear waves is probed by transmitting short pulses or beams of high-frequency ultrasound within the medium.

[0009] Thanks to The advantageous geometry used (e.g., see Figure 1a The mechanical actuator and the ultrasonic transducer share the same axis of symmetry, such as... Figure 1a As shown by the dashed line in the diagram. This geometric arrangement avoids systematic errors when measuring the propagation velocity of shear waves: the shear waves and the ultrasonic beam propagate in the same direction.

[0010] also, The probe provides a motion sensor, such as a Hall effect position sensor, capable of measuring the displacement of the probe tip relative to the probe housing. Measurements are only valid if the tip trajectory follows a predetermined envelope, such as a sine curve. In conventional VCTE probes, only the relative motion of the probe tip with respect to the probe housing is measured. That is, in conventional VCTE probes, the motion of the probe tip is measured within a reference frame of the probe housing.

[0011] A relevant issue with currently available VCTE probes is the control of the actual movement of the probe tip when applying a transient shear wave to the tissue being examined. For example, when a shear wave is applied, the recoil force of the probe can be increased in the movement of the tip, and the applied pulse can be deformed. This issue involves the recoil force of the operator's hand and the control of the force that the operator must apply to keep the probe against the patient's body: Proper use of VCTE probes according to existing technology requires a skilled or qualified operator.

[0012] Without controlling the probe's recoil force, the actual movement of the probe tip relative to the patient's body cannot be known. Measurements may depend on the force applied by the operator during the generation of the shear wave.

[0013] Patent applications US8333704B2 ("Hand-held force-controlled ultrasound probe" filed by Anthony et al. on December 18, 2010) and US2012 / 0316407A1 ("Sonographer fatigue monitoring" filed by Anthony et al. on June 12, 2012) disclose an ultrasonic probe with a linear actuator and a force sensor. Figure 1bThe apparatus described in document US8333704 is shown. According to these documents, an ultrasonic transducer is moved by an electric actuator to control the force applied to the tissue to be analyzed. The movement of the ultrasonic transducer is controlled based on a signal provided by a force sensor and used as a feedback signal.

[0014] These documents address the problem of applying constant or time-dependent forces during ultrasonic measurements, but these published technical solutions have several drawbacks.

[0015] For example, these devices described in the prior art include external mechanically movable parts: such as Figure 1b As indicated by the arrow, the ultrasonic transducer moves relative to the probe housing. Several defects are associated with this external moving part, such as the need for frequency calibration operations.

[0016] The paper "Probe Oscillation Shear Elastography (PEOSE): A high Frame-Rate Method for Two-dimensional ultrasound shear waveelastography" by D. Mellema et al. (published in IEEE Transactions on Medical Imaging, Vol. 35, No. 9, 2016) describes another approach described in the prior art. This approach describes a probe for continuous wave elastography. However, this approach is not suitable for applying instantaneous shear pulses to tissue; it is only applicable to continuous wave shear wave oscillations. Furthermore, this elastography probe consists of two separate components, which is a significant drawback for in-vivo applications. For example, the probe is difficult to manipulate due to the presence of multiple parts.

[0017] Furthermore, depending on the operator, it is difficult to control the applied force when placing the ultrasound transducer on the patient's body. Therefore, the device cannot perform accurate and reproducible measurements regardless of the operator.

[0018] In addition, if too much force is applied to the patient's body, the device's electric actuator may be damaged.

[0019] Finally, the acoustic energy transmitted to the patient by the ultrasonic transducer of the sensor may be very high, and unnecessary use may lead to injury to the patient, electrical failure, and premature damage to the ultrasonic transducer. Summary of the Invention

[0020] One aspect of the present invention is an apparatus for overcoming the aforementioned deficiencies. Therefore, one aspect of the present invention is an apparatus for accurately and reproducibly measuring the viscoelasticity of a viscoelastic medium, thereby limiting health risks to the patient and extending the lifespan of the apparatus.

[0021] To achieve this objective, a first aspect of the present invention relates to an apparatus for measuring the viscoelasticity of a viscoelastic medium, said medium having an ultrasonic signal after being subjected to an ultrasonic pulse, said apparatus comprising:

[0022] - Probes for transient elastic imaging include:

[0023] • Probe housing;

[0024] • At least one ultrasonic transducer having an axis of symmetry;

[0025] • At least one vibrator, said vibrator being located inside the probe housing;

[0026] • Force sensor, configured to measure the force exerted by the probe on the viscoelastic medium to be measured;

[0027] -Signal generator;

[0028] The device is characterized in that:

[0029] • The vibrator is arranged to cause the probe housing to move along a predetermined axis, which is the axis of symmetry of the ultrasonic transducer;

[0030] • The ultrasonic transducer is fixed to the probe housing, so that the ultrasonic transducer does not move relative to the probe housing;

[0031] The signal generator is configured to generate a contact ready signal when the ultrasonic transducer of the probe contacts the viscoelastic medium to be measured, and the signal generator sets the contact ready signal when the force applied by the ultrasonic probe on the viscoelastic medium is greater than a minimum contact force threshold.

[0032] The probe housing is the enclosure of the VCTE probe, and the enclosure contains a vibrator or electric actuator. The probe housing may also contain other elements, such as position sensors, logic circuits, or connection devices, for storing data or exchanging data with a computer or other electronic device. An ultrasonic transducer is a device suitable for emitting and receiving ultrasonic waves. An ultrasonic transducer can be formed using a single transducer or an array of transducers, for example, to form a linear detector.

[0033] The axis of symmetry of an ultrasonic transducer is its geometric axis of symmetry. The axis of symmetry of the ultrasonic transducer is also the direction along which the transducer emits ultrasonic waves. The axis of symmetry of the transducer corresponds to the propagation direction of the short ultrasonic pulses emitted by the transducer.

[0034] According to the present invention, the ultrasonic transducer is kinetically fixed to the probe housing, which means that the ultrasonic transducer has no relative movement with respect to the probe housing.

[0035] One end of the ultrasonic transducer can be fixed to the end of the probe housing. The other end of the ultrasonic transducer can vibrate freely to send ultrasonic waves to the medium to be analyzed.

[0036] Alternatively, the ultrasonic transducer can be attached to the probe housing using a probe tip. When the probe tip is present, the probe tip may have one end fixed to one end of the probe housing and another end fixed to the ultrasonic transducer.

[0037] The following description of the invention supports two scenarios: when the ultrasonic transducer is directly fixed to the probe housing, and when the ultrasonic transducer is fixed to the probe housing via the probe tip. These two configurations are given only as exemplary embodiments; other configurations are also possible.

[0038] A vibrator is a device used to move objects inside the housing of a probe. For example, a vibrator can cause an object to oscillate at a frequency between 1 and 5000 Hz.

[0039] Since the movement of the probe itself is caused by the movement of objects inside the probe housing, the probe according to the present invention can be considered an inertial probe. The probe according to the present invention does not include any external mechanically movable parts.

[0040] The probe according to the invention is a transient elastography probe. This means it is suitable for applying transient shear waves to tissue for detection and for analyzing the propagation of the shear waves by transmitting ultrasound at a high repetition rate.

[0041] The movement of a probe generates shear waves within the tissue, which in turn causes an ultrasonic transducer to push against the tissue. Shear waves are generated by applying low-frequency pulses to the surface of the medium. For example, the pulses may have a sinusoidal shape with one cycle at a center frequency f between 1 Hz and 5000 Hz.

[0042] The duration of the low-frequency pulses applied to the tissue ranges from 1 / 2F to 20 / f.

[0043] From 100Hz to 100*10 3 The ultrasonic short pulses are emitted with a repetition rate between Hz.

[0044] Shear wave propagation is detected by transmitting ultrasonic pulses or beams at a high repetition rate within a medium and by detecting the backscattered ultrasonic signals. In reality, tissues contain inhomogeneities or particles capable of partially reflecting ultrasonic pulses.

[0045] By recording and analyzing subsequent backscattered signals, the displacement of tissue caused by the propagation of shear waves can be calculated. The properties of the shear waves can then be derived. For example, the propagation speed of shear waves is directly related to the hardness of the viscoelastic medium.

[0046] The advantage of the probe described in this invention lies in controlling the actual movement of the ultrasonic transducer. In practice, the ultrasonic transducer is fixed to the probe housing, and there is no mutual movement between the ultrasonic transducer and the probe housing. This allows monitoring of the movement of the probe housing, which corresponds to the actual movement of the ultrasonic transducer. Measuring the actual movement of the ultrasonic transducer is crucial for controlling the shape of the instantaneous shear waves generated within the tissue. For example, the movement of the probe can be measured using an accelerometer mounted on the probe itself.

[0047] In other words, unlike the conventional VCTE probe, this invention measures the motion of the ultrasonic transducer in a terrestrial frame of reference. In fact, in the prior art VCTE probe, the motion of the ultrasonic transducer is measured in a frame of reference of the probe housing, and only the relative motion of the ultrasonic transducer with respect to the probe housing is measured.

[0048] Specifically, by controlling the circuit and using the motion of the probe housing as a feedback signal, the motion of the object inside the probe housing caused by the vibrator can be determined. This allows for direct compensation for the operator's hand movements during the application of shear waves.

[0049] The operator does not need to apply precise force to compensate for the probe's recoil. As a result, measuring the hardness of viscoelastic media becomes simpler for the probe operator. Furthermore, hardness measurements are more reproducible.

[0050] According to existing techniques, only the relative motion of the ultrasound transducer relative to the probe housing is measured, which fails to take into account the probe's recoil force. As a result, even if the relative motion of the tip follows a sinusoidal trajectory, the effective low-frequency pulse applied to the patient's body may have a different shape due to the probe's recoil force.

[0051] According to the present invention, the ultrasonic transducer in contact with the patient's body moves together with the probe housing. Detecting the movement of the probe housing is equivalent to detecting the movement of the probe tip. The movement of the probe housing is used as feedback for the vibrator. In practice, the oscillation amplitude of the vibrator can be adjusted to obtain the desired movement of the probe tip in contact with the patient's body. Furthermore, the probe according to the present invention has no external moving parts, thus eliminating the need for frequent mechanical calibration.

[0052] Because the device of the present invention includes a signal generator that emits a contact-ready signal, the operator does not activate the ultrasound signal until the signal generator emits the contact-ready signal. Therefore, the device ensures that the power of the ultrasound signal emitted by the ultrasound transducer is used only when necessary and is as low as possible for the patient.

[0053] The signal generator generates the contact-ready signal based on the contact force between the ultrasound transducer and the patient's body. The contact force can be measured using a force sensor mounted on the probe. The contact-ready signal is generated only if the measured contact force meets predetermined conditions. For example, the measured contact force must be greater than a minimum contact force threshold. When these conditions are met, the probe is considered to be in contact with the viscoelastic medium being measured. Alternatively, the contact-ready signal can be generated only if the contact force is between a minimum contact force threshold and a maximum contact force threshold.

[0054] Furthermore, considering that the contact-ready signal is only set when the transducer of the ultrasound probe contacts the viscoelastic medium being measured, the measurements of this device are accurate and reproducible, independent of the operator. In contrast, with prior art devices, the operator can generate ultrasound signals even when the transducer attached to the tip of the ultrasound probe is not in contact with the medium being measured, leading to inaccurate or erroneous measurements. In reality, measurements achieved using prior art devices rely on the operator, and especially on the contact between the probe and the patient's body.

[0055] In addition to the contact-ready signal, the device according to the invention is also configured to transmit a measurement-ready signal. The measurement-ready signal is transmitted only when the contact force between the US transducer and the tissue is between a minimum and a maximum measurement force threshold. When this condition is met, the measurement-ready signal is emitted, and viscoelastic measurement is triggered automatically or manually. In other words, a low-frequency pulse is applied to the tissue only when the measurement-ready signal is emitted.

[0056] The device according to the first aspect of the invention may also have one or more of the following features, either individually or in combination of all technically possible features:

[0057] - A signal generator is constructed and configured to emit a measurement-ready signal;

[0058] - A force sensor is constructed and configured to measure the force applied by an ultrasonic probe to a viscoelastic medium to be measured. When the force applied by the ultrasonic probe to the viscoelastic medium is greater than a minimum contact force threshold, the signal generator sets the contact ready signal, and when the force applied by the ultrasonic probe is greater than a minimum measurement force threshold, the signal generator sets the measurement ready signal.

[0059] - The minimum contact force threshold is between 0.1N and 1.0N;

[0060] - The minimum measurement force threshold is between 1.0N and 6.0N;

[0061] - When the force applied by the ultrasonic probe on the viscoelastic medium is less than the maximum measurement force threshold, the signal generator sets the measurement ready signal;

[0062] - The maximum measurement force threshold is between 6.0N and 20.0N;

[0063] - The minimum contact force threshold is equal to 0.5N;

[0064] - The minimum measurable force threshold is equal to 4.0 N;

[0065] - The maximum measurable force threshold is equal to 8.0 N;

[0066] -When the force measured by the force sensor is between the minimum contact force threshold and the maximum contact force threshold,

[0067] Set the contact ready signal;

[0068] - An apparatus according to a first aspect of the invention, characterized in that the ultrasonic transducer is fixed to a probe housing by means of a probe tip, the probe tip having a first end fixed to the probe housing and a second end fixed to the ultrasonic transducer;

[0069] - The apparatus according to a first aspect of the invention is characterized in that the probe tip is replaceable; - the probe includes a position sensor and the probe includes a control loop configured to control a vibrator based on a signal received from the position sensor;

[0070] - The force sensor is a capacitive sensor or an applied force sensor;

[0071] - The apparatus includes means for triggering a measurement of the viscoelasticity of a viscoelastic medium only when a measurement ready signal is set; these means include an electronic microchip or electronic microprocessor that receives the contact ready signal and the measurement ready signal; if a signal is requested, the microchip or microprocessor triggers the measurement of viscoelasticity when the measurement ready signal is set;

[0072] - The vibrator or electric actuator is constructed and configured to generate a low-frequency pulse displacement of the ultrasonic probe only when the measurement ready signal is set;

[0073] - A force sensor included in the probe is configured to measure the force applied by the ultrasonic probe to the viscoelastic medium to be measured. The signal generator sets the contact-ready signal and / or the measurement-ready signal when the force measured by the force sensor satisfies the following conditions:

[0074] - For the contact ready signal, the force measured by the force sensor is greater than the minimum contact force threshold.

[0075] - For the measurement ready signal, the force measured by the force sensor is greater than a minimum measurement force threshold. Furthermore, in a non-limiting embodiment, the measurement ready signal is set when the force measured by the force detection module is less than a maximum measurement force threshold;

[0076] - The ultrasonic transducer is constructed and configured to activate the transmission of ultrasonic signals when the contact ready signal is set;

[0077] - The device includes a display unit for displaying an ultrasonic image, the display unit being configured and set to refresh the ultrasonic image only when the contact ready signal is set;

[0078] -The device includes a guide indicator configured and set to refresh only when the contact ready signal is set;

[0079] - The ultrasonic probe includes at least one light-emitting diode, and the ultrasonic probe is configured to illuminate the light-emitting diode only when the contact ready signal is set;

[0080] - The device includes device commands that can be accessed only when the contact ready signal is set;

[0081] -The device is constructed and configured to deactivate the combined treatment of the device when the contact ready signal is set;

[0082] - The device is constructed and configured to activate the combined treatment when the contact ready signal is set;

[0083] - The ultrasonic transducer is fixed to the probe housing by means of a probe tip, the probe tip having a first end fixed to the probe housing and a second end fixed to the ultrasonic transducer;

[0084] - The device is constructed and configured to trigger the application of a low-frequency pulse to the viscoelastic medium to be measured only when the measurement ready signal is set;

[0085] - The probe includes a position sensor, and the device includes a control loop configured to control the vibrator based on a signal received from the position sensor;

[0086] - The force sensor is a capacitive sensor or an applied force sensor;

[0087] A second aspect of the present invention relates to a method for measuring the viscoelasticity of a viscoelastic medium, the medium having an ultrasonic signal after being subjected to an ultrasonic pulse, the method comprising the following steps:

[0088] - Position the ultrasonic transducer of the ultrasonic probe to contact the viscoelastic medium to be measured.

[0089] - When the transducer of the ultrasonic probe contacts the viscoelastic medium to be measured, a contact ready signal is generated, and the contact ready signal is emitted using a signal generator constructed and configured to emit the contact ready signal.

[0090] The method according to one aspect of the invention may also have one or more of the following features, either individually or in combination of all technically possible features:

[0091] The method includes the step of measuring the force applied by the ultrasonic probe to the viscoelastic medium to be measured, wherein the force measurement result is determined by a force sensor configured to measure the force applied by the ultrasonic probe to the viscoelastic medium to be measured, wherein the signal generator sets the contact ready signal when the force applied by the ultrasonic probe is higher than a minimum contact force threshold, and sets the measurement ready signal when the force applied by the ultrasonic probe is higher than a minimum measurement force threshold or between the minimum and maximum measurement force thresholds.

[0092] The method includes the step of emitting an ultrasonic pulse only when the contact ready signal is emitted;

[0093] The method includes the step of displaying a positioning device only when the contact-ready signal is issued; the positioning device is a tool used by an operator to position the viscoelastic tissue to be tested; examples of the positioning device are images, guide tools, or other indicators;

[0094] The method includes the step of refreshing the image only when the contact ready signal is issued;

[0095] The method includes the step of refreshing the bootloader only when the contact ready signal is issued;

[0096] The method includes the step of accessing the device's memory only when the contact ready signal is issued;

[0097] The method includes the step of illuminating the LED only when the contact ready signal and the measurement ready signal are set;

[0098] The method includes the step of triggering a viscoelastic measurement only when the contact ready signal and the measurement ready signal are set;

[0099] The method includes the step of accessing a command only when the contact ready signal and the measurement ready signal are set;

[0100] The method includes the steps of deactivating other treatments only when the contact ready signal is issued, and activating other treatments when the contact ready signal is not issued. Attached Figure Description

[0101] The accompanying drawings are provided to further illustrate the invention and form part of this specification, to explain various aspects of the invention and, together with the textual description, to explain the principles of the invention:

[0102] - Figure 1a This demonstrates a transient elastic imaging device based on the prior art;

[0103] - Figure 1b This demonstrates a pressure-controlled ultrasonic probe based on existing technology;

[0104] - Figure 2 An example of an apparatus for measuring the viscoelasticity of a viscoelastic medium, according to one aspect of the present invention, is shown;

[0105] - Figure 3 Showing according to Figure 2 Implementation methods of the device;

[0106] - Figure 4 The steps of a method for measuring the viscoelasticity of a viscoelastic medium according to one aspect of the present invention are shown. Detailed Implementation

[0107] A first aspect of the present invention provides a device DEV for measuring the viscoelasticity of a viscoelastic medium, said medium having an ultrasonic signal after ultrasonic irradiation. Specifically, the device DEV of the present invention can quantify liver fibrosis in an instantaneous and non-invasive manner.

[0108] According to the aspect selected to illustrate the invention and as follows Figure 2 In the example shown, the device DEV includes an ultrasonic probe 1. Figure 2 A cross-sectional view of probe 1 is shown.

[0109] Ultrasonic probe 1 includes:

[0110] • A probe housing PC comprising at least one vibrator or electric actuator VIB; in a particular embodiment, the vibrator VIB includes a fixed portion FIX and a movable portion MOV;

[0111] • The first vertical bar F1, the second vertical bar F2, and the horizontal bar F are configured to fix the fixed part of the vibrator VIB to the probe housing PC by FIX;

[0112] • An ultrasonic transducer US with an axis of symmetry A;

[0113] • A position sensor POS, including an accelerometer ACC, is configured to measure the position or displacement of the probe housing PC as a function of time. The position sensor operates in conjunction with a control loop that analyzes the data provided by the position sensor POS and controls the vibrator VIB. The position sensor is used to control the vibration of the probe according to acceleration, velocity, or preferably displacement or position.

[0114] • The probe tip PT has a first end PTE1 fixed to the front end of the probe housing PC and a second end PTE2 fixed to the ultrasonic transducer US. The front end of the probe housing PC is the end of the probe housing placed near the tissue.

[0115] • Force sensor FS is disposed between the probe tip and the remainder of the probe, and is disposed on the probe tip PT and near the ultrasonic transducer US. Force sensor FS is connected to signal generator 9 by means of a connection device not shown in FIG1. ​​Force sensor FS is constructed and configured to measure the contact force applied by probe 1 on the viscoelastic tissue to be measured.

[0116] • Connection device for connecting the position sensor POS to the control loop and the vibrator VIB, and connection device for connecting the ultrasonic transducer US and the force sensor FS to other components of the device DEV.

[0117] • Display unit 7, constructed and configured to display ultrasound images

[0118] Button 8 is constructed and configured to activate ultrasonic probe 1.

[0119] • A signal generator 9 is constructed and configured to issue a contact ready signal, or a measurement ready signal, or both a contact ready signal and a measurement ready signal.

[0120] The device DEV further includes:

[0121] - The device controller 10 is constructed and configured to be controlled by the operator's device DEV.

[0122] - A cable 11 is constructed and configured to link the ultrasonic probe 1 to the device controller 10.

[0123] In the following description, we use the liver as an example of a viscoelastic medium for measuring its viscoelasticity.

[0124] Specifically, the signal generator 9 of the device DEV of the present invention is configured to emit a contact-ready signal when the transducer US of the ultrasonic probe 1 contacts the viscoelastic medium to be measured. Generating the contact-ready signal allows for accurate and reproducible viscoelastic measurements of the liver to be obtained without the operator's involvement.

[0125] According to one aspect of the invention, a force sensor FS is used to determine a contact ready signal. Specifically, a signal generator 9 generates a contact ready signal when the force applied by the ultrasonic probe 1 to the patient's skin exceeds a minimum contact force threshold. More specifically, the force sensor FS is adapted to measure the force applied by the probe 1 to the patient's skin.

[0126] According to one implementation, when the force measured by the force sensor FS is greater than the minimum contact force threshold, the signal generator 9 issues a contact ready signal.

[0127] According to one implementation, the minimum contact force threshold is between 0.1N and 1N.

[0128] According to one embodiment, the minimum threshold for the contact force is 0.5 N. This minimum force level is used to detect the contact between the tip of the probe and the viscoelastic tissue to be measured.

[0129] Preferably, the use of a minimum contact force threshold allows for control of the contact between the probe and the viscoelastic medium, for example, to prevent the emission of ultrasonic waves when the probe is not in use.

[0130] According to one implementation, when the force measured by the force sensor FS is less than the maximum contact force threshold, the signal generator 9 issues a contact ready signal.

[0131] Preferably, the contact ready signal prevents the operator from applying excessive force to the patient's body, thereby harming the patient.

[0132] Preferably, the contact ready signal prevents the probe 1 from being damaged by applying high force to the patient's body.

[0133] According to one implementation, when the force measured by the force sensor FS is greater than the minimum force threshold, the signal generator 9 issues a measurement ready signal.

[0134] Preferably, a minimum measurement force threshold is necessary in order to effectively transmit the shear wave into the viscoelastic medium and obtain reliable measurements of the viscoelasticity of the tissue.

[0135] According to one embodiment of the present invention, when the force measured by the force sensor FS is between the minimum and maximum force thresholds, the signal generator 9 issues a measurement ready signal.

[0136] According to one embodiment, the minimum measuring force threshold is between 1.0N and 6.0N, and the maximum measuring force threshold is between 6.0N and 20.0N.

[0137] Preferably, the range of the force threshold allows the measurement conditions to be adapted to the size of the ultrasound transducer and the patient's body size. For example, for obese patients, a larger ultrasound probe and a higher force threshold can be selected to accurately apply low-frequency pulses for elastography measurements.

[0138] According to one implementation, the minimum measuring force threshold is 4N and the maximum measuring force threshold is 8N.

[0139] The viscoelastic measurement is triggered only when the signal generator 9 issues a measurement ready signal. Preferably, when conditions related to the measurement force threshold are met and a measurement ready signal is issued, a low-frequency pulse is effectively applied to the viscoelastic tissue, and the shape of the low-frequency pulse is precisely controlled.

[0140] The device DEV includes a measuring device for triggering the measurement of viscoelasticity of the viscoelastic medium only when a measurement ready signal is set; these devices include an electronic microchip or electronic microprocessor that receives a contact ready signal and a measurement ready signal; if a signal is requested, the microchip or microprocessor triggers the measurement of viscoelasticity when the measurement ready signal is set. The device for triggering the measurement may be integrated into the device controller 10.

[0141] Preferably, when the conditions related to the measurement force threshold are met and a measurement ready signal is issued, assuming impedance matching between the subcutaneous tissue and the liver, the shear wave is effectively introduced into the patient's body.

[0142] According to one embodiment of the present invention, the force sensor FS is a capacitive sensor or an applied force sensor.

[0143] One advantage of this implementation is that it allows for precise measurement of the force exerted by probe 1 on the patient's body.

[0144] According to one embodiment of the invention, probe 1 includes a position sensor POS, and device DEV includes a control loop configured to control a vibrator (VIB) based on a signal received from said position sensor (POS).

[0145] The control loop can be built into probe 1 or device controller 10. In practice, the control loop sets the motion parameters of vibrator VIB to obtain the target low-frequency pulse. The position of probe 1 measured by position sensor POS is used as a feedback signal for the control loop.

[0146] One advantage of this implementation is the precise control over the shape of the low-frequency pulses applied to the patient's body. Furthermore, probe 1 has no external moving parts, thus eliminating the need for frequent mechanical calibration.

[0147] Figure 3 For a detailed cross-sectional view of probe 1, probe 1 further includes a first spring K1 extending from the first rod F1 to the moving part MOV and a second spring K2 extending from the second rod F2 to the moving part MOV;

[0148] According to one embodiment, the probe housing PC is cylindrical, with axis A being the axis of the cylinder. Alternatively, the probe housing may be a gyroscopic shape having axis A.

[0149] The size of the probe housing is chosen to obtain a handheld probe. According to this embodiment, the circumference of the cylinder is between 120 mm and 160 mm.

[0150] Axis A is the axis of symmetry of the ultrasonic transducer US. For example, in the case of a cylindrical ultrasonic transducer, axis A is the axis of the cylinder forming the transducer. Axis A also indicates the propagation direction of the short ultrasonic pulses emitted by the ultrasonic transducer US.

[0151] According to another embodiment, the probe housing PC can have any shape suitable for being held by an operator's hand during measurement. For example, the probe housing PC can have Figure 1b The shape of the standard elastography probe is shown.

[0152] The vibrator VIB is located inside the probe housing PC and is formed by two elements: a moving body MOV and a stationary element FIX. The vibrator VIB is configured to move the moving body MOV, thereby causing the entire probe 1 to move along axis A.

[0153] We define the direction perpendicular to axis A as the vertical direction, and the direction parallel to axis A as the horizontal direction.

[0154] According to one embodiment, the fixing part FIX is held in place by a retaining device formed by a first vertical rod F1, a horizontal support rod F, and a second vertical rod F2. The first and second vertical rods F1 and F2 are fixed to the probe housing. The horizontal support rod F extends from the first vertical rod F1 to the second vertical rod F2.

[0155] Alternatively, there may be only one vertical rod F1 or F2 to support the horizontal rod F and the vibrator VIB.

[0156] Retaining devices F1, F, and F2 block the fixing part FIX, which is then secured to the probe housing PC. Any other retaining device suitable for securing the fixing part FIX of the vibrator VIB to the probe housing PC may also be used.

[0157] The moving part MOV is separated from the first and second vertical rods F1 and F2 by two springs K1 and K2, respectively. The first spring K1 extends from the first vertical rod F1 to the moving part MOV, and the second spring extends from the second vertical rod F2 to the moving part MOV.

[0158] When the vibrator VIB is actuated, the moving part MOV slides along the horizontal rod F. The horizontal rod F supports both the fixed part FIX and the moving part MOV of the vibrator VIB.

[0159] Two springs, K1 and K2, support the moving part MOV and act as a restoring force when the moving part MOV is set to move.

[0160] It is worth noting that the moving part (MOV) oscillates inside the probe housing (PC). The vibrator (VIB) does not move any external parts of the inertial probe 1.

[0161] according to Figure 2 In the embodiment shown, the moving body MOV is a permanent magnet, and the fixed part FIX is a coil. When a potential is applied to the coil FIX, a force is applied between the coil FIX and the magnet MOV, causing the moving body MOV to oscillate along axis A.

[0162] Due to the combined effects of the electromagnetic force between the coil and the magnet, and the restoring force exerted by springs K1 and K2, the motion of the moving body MOV causes the motion of the probe housing PC. This motion can be described as a result of the law of conservation of momentum, and the motion of the moving body MOV determines the recoil force of the probe housing PC.

[0163] Therefore, the entire inertial probe 1 is set to move, and the ultrasonic transducer US pushes against the patient's body.

[0164] The advantage of this structure is that the motion of the ultrasonic transducer US relative to the tissue being analyzed is directly determined by the vibrator VIB and can be accurately controlled. In other words, assuming there is no relative motion between the ultrasonic transducer US and the probe housing PC, the displacement amplitude of the ultrasonic transducer US is consistent with the motion amplitude of the probe housing PC. Therefore, the shape of the low-frequency pulse applied to the tissue can be accurately controlled.

[0165] According to the present invention, there are several available methods for fixing the ultrasonic transducer US to the probe housing PC.

[0166] According to one embodiment, the ultrasonic transducer US can be directly mounted to the probe housing PC. Alternatively, the ultrasonic transducer US can be mounted to a force sensor FS, which is then attached to the probe housing PC.

[0167] The advantage of this implementation is that the structure is easy to implement. Furthermore, the force sensor FS is in direct contact with the ultrasonic transducer US, thus effectively controlling the deformation of the probe housing. The deformation of the probe housing PC is a micrometric deformation caused by the contact between the ultrasonic transducer US and the tissue to be analyzed.

[0168] according to Figure 2 In the illustrated embodiment, the ultrasonic transducer US is fixed to the probe tip PT, which includes a first end PTE1. The first end PTE1 is fixed to the front end of the probe housing PC. For example, the probe tip PT is distinctly cylindrical, as shown in Figure 1.

[0169] For example, such as Figure 2 As shown, by inserting the first end PTE1 of the probe tip into the housing HOU of the force sensor FS, the probe tip PT can be locked to the probe housing PC. The second end PTE2 of the probe tip is fixed to the ultrasonic transducer US.

[0170] The advantage of this implementation is that the probe tip PT is easy to replace. In other words, different probe tips PT with different ultrasound transducers US can be used to adapt the characteristics of the emitted ultrasound beam to the characteristics of the tissue or patient's body.

[0171] According to one implementation, the motion of the inertial probe 1 is measured using a position sensor POS.

[0172] The advantage of this implementation is that it directly measures the amplitude of motion of the probe housing PC, which is the same as the amplitude of motion of the ultrasonic transducer US. In fact, according to the present invention, it is possible for the ultrasonic transducer US to have no motion relative to the probe housing PC. That is, the ultrasonic transducer US remains stationary in the reference frame of the probe housing PC.

[0173] exist Figure 3 In the illustrated embodiment, the position sensor POS is formed by an accelerometer ACC and a circuit DI that performs double temporal integration. The double integrator DI determines the probe's position r based on the measured acceleration.

[0174] The present invention can also use any circuit that can calculate the position r based on the measured acceleration.

[0175] Preferably, the position sensor POS provides a direct measurement of the displacement of the ultrasonic transducer US. That is, the position sensor POS directly measures the shape of the low-frequency pulses applied to the tissue in order to generate transient shear waves within the tissue.

[0176] Probe 1 is then used to cooperate with a control loop that drives the vibrator VIB to obtain a predefined low-frequency pulse shape. For example, the control loop can be built into... In the device.

[0177] The position r measured by the position sensor POS is then used as a feedback signal for controlling the vibrator VIB. According to one embodiment, the position r is fed into a control loop that controls the amplitude and frequency of the oscillation of the moving body MOV.

[0178] Thanks to this setup, the movement of the ultrasound transducer US can be directly controlled, and well-defined low-frequency pulses can be applied to the patient's body.

[0179] according to Figure 3 In the illustrated embodiment, probe 1 further includes a connection device for transmitting electrical signals between the position sensor POS, the control loop, and the vibrator VIB. The connection device also includes a means for transmitting the required power to operate the vibrator VIB, the ultrasonic transducer US, and other built-in devices. The power transmission device... Figure 3 Not displayed.

[0180] according to Figure 3 In the embodiment shown, the force sensor FS is a tip holder TH equipped with at least one strain gauge SG or other stress sensor. Figure 3 The force sensor is also adapted to receive and lock the tip of the probe PT.

[0181] According to one embodiment, the device connecting the position sensor POS, the control loop, and the vibrator VIB can be wireless.

[0182] One advantage of this invention is the ability to define and finely control the low-frequency pulses applied to the tissue. A position sensor POS measures the actual movement of the ultrasound transducer US. A control loop adjusts the oscillation characteristics of the moving body MOV to apply a target low-frequency pulse shape to the patient's body.

[0183] In typical transient elastography applications, the low-frequency pulses applied to the patient's body are sinusoidal, with a center frequency between 1 Hz and 5000 Hz, a peak-to-peak amplitude between 10 μm and 20 mm, and a duration between 100 μs and 20 s. The repetition rate of the ultrasound pulses is between 100 Hz and 100,000 Hz.

[0184] According to one implementation, the peak-to-peak amplitude is between 50 μm and 5 mm.

[0185] By pressing the transducer against the tissue, the motion of the probe housing PC is transmitted to the tissue. Because probe 1 is also dynamically connected to the operator's hand, it is difficult to determine the actual motion of the US transducer relative to the tissue. The operator's hand movements inevitably alter the shape of the low-frequency pulses applied to the patient's body.

[0186] This invention solves the problem by eliminating the motion of the ultrasonic transducer US relative to the probe housing PC and by using a position sensor POS to measure the position of the probe housing PC itself. The measured position is used as feedback for the parameters of the vibrator VIB. The parameters of the vibrator VIB are then adjusted until a predefined low-frequency pulse shape is obtained.

[0187] In other words, probe 1 has no external mechanically movable parts. Therefore, probe 1 is an inertial probe, its motion determined by the motion of the object MOV located within the probe housing. Since there is no relative motion between the ultrasonic transducer US and the probe housing PC, measuring the displacement amplitude of the probe housing PC is equivalent to measuring the displacement of the ultrasonic transducer US. Thus, probe 1 can then directly measure the shape of the low-frequency pulse applied to the tissue, compensating for any possible movements of the operator's hand. The absence of external movable parts also eliminates the need for frequent mechanical calibration of the probe.

[0188] According to another embodiment of the present invention, the mass of the moving part MOV is equal to or greater than one-quarter of the total mass M of the inertial probe 1.

[0189] One advantage of this embodiment is that the overall motion of the inertial probe 1 can be effectively controlled by simply changing the motion of the moving part MOV. That is, if the mass of the moving part MOV is small, its influence on the motion of the entire inertial probe 1 is smaller due to the law of conservation of momentum. Therefore, control over the motion of the tip becomes less effective.

[0190] According to one implementation, the US transducer is a disc-shaped ultrasonic transducer.

[0191] One advantage of this shape is that it allows for the emission of ultrasonic beams with extremely high symmetry. This high symmetry simplifies the calculation of the propagation of both the ultrasonic beam and the shear wave.

[0192] According to one aspect of the invention, the force sensor FS includes a processor adapted to calculate and send the applied force to a signal generator 9.

[0193] According to one aspect of the invention, when a contact-ready signal is set, the ultrasonic probe 1 is configured to illuminate at least one light-emitting diode (LED) of the ultrasonic probe 1. In practice, illuminating the LED serves to notify the operator that the ultrasonic probe 1 has made proper contact with the patient's skin, thereby allowing the operator to stop increasing the force applied to the patient's skin.

[0194] According to another aspect of the invention, an acoustic indicator on the signal generator 9 is constructed and configured to indicate to the user that a contact ready signal has been set.

[0195] In addition, according to one aspect of the invention, when a contact ready signal is set, the transducer US is constructed and configured to emit an ultrasonic signal.

[0196] The device controller 10 is configured and set to control the frequency of the ultrasonic signal generated by the transducer US.

[0197] According to one embodiment, the device controller 10 is also configured and set to control the motion parameters of the vibrator VIB via a control loop and using the position measured by the position sensor POS as feedback.

[0198] The transmission and reception of ultrasonic signals by the ultrasonic transducer US of the ultrasonic probe 1 enable the acquisition of a continuous image of a portion of the medium to be analyzed. Therefore, the image generation is performed only when the transducer US is in contact with the viscoelastic medium to be measured. Furthermore, the image acquired by the ultrasonic transducer US is one-dimensional. According to one aspect of the invention not shown, the device DEV includes a plurality of ultrasonic transducers US that can be placed in any manner, for example, in a linear (similar to an echographic rod) or honeycomb pattern. In this manner, the device DEV can acquire three-dimensional images. Therefore, viscoelasticity can be measured in different regions of the medium to be analyzed.

[0199] Furthermore, according to one aspect of the invention, when a contact-ready signal is set, a display unit 7, also referred to as an "alphanumeric display screen," is configured and set to refresh the ultrasonic image. In fact, the alphanumeric display screen 7 of the ultrasonic probe 1 is configured and set to display the ultrasonic image. Displaying the image helps the operator locate the area where they want to perform viscoelasticity measurements.

[0200] Furthermore, according to one aspect of the invention, when the contact ready signal is set, the guide indicator is refreshed. The "guide indicator" refers to an indicator displayed to the operator to help them locate the optimal measurement position.

[0201] Furthermore, according to one aspect of the invention, when a contact ready signal is set, the device controller 10 is configured and set to restrict at least one command that accesses the device controller 10.

[0202] In addition, the signal generator 9 of the device DEV of the present invention is constructed and configured to transmit a measurement ready signal. In fact, excessive force applied to the body can cause deviations in viscoelastic measurement results.

[0203] According to one aspect of the invention, a measurement ready signal is determined using a force sensor FS. Specifically, the signal generator 9 generates the measurement ready signal when the force applied by the ultrasonic probe 1 to the patient's skin is greater than a minimum measurement force threshold but less than a maximum measurement force threshold.

[0204] According to one aspect of the invention, the force sensor FS includes a value adapted to calculate and transmit the measured contact force to the signal generator 9.

[0205] According to one aspect of the invention, when a measurement ready signal is set, the ultrasonic probe 1 illuminates at least one light-emitting diode (LED). In practice, illuminating the LED serves to notify the user that low-frequency pulses can be generated.

[0206] According to another aspect of the invention, an acoustic indicator on the signal generator 9 is constructed and configured to indicate to the operator a contact ready signal and / or a measurement ready signal distinguished by sound type.

[0207] According to one aspect of the invention, the vibrator VIB moves to apply low-frequency pulses only when the signal generator 9 issues a measurement-ready signal. According to one embodiment, the device controller 10 controls the vibrator VIB based on a feedback signal provided by the position sensor POS.

[0208] Specifically, according to one aspect of the invention, the device controller 10 is configured to control the power of the mechanical shear waves generated by the vibrator VIB on the patient's skin by controlling the electric actuator VIB. Furthermore, the device controller 10 is configured to monitor the number of shear waves generated in the medium.

[0209] In addition, according to one aspect of the invention, the electric actuator VIB, controlled by the device controller 10, is constructed and configured to generate instantaneous low-frequency pulses with a frequency range between about 1 Hz and about 5000 Hz. The term "instantaneous low-frequency pulse" refers to a mechanical stress of a predetermined duration with a frequency between about 1 Hz and about 5000 Hz and a peak-to-peak amplitude between about 10 μm and 20 mm, preferably between about 500 μm and about 5 mm. The duration of the stress is between about 100 μs and about 20 seconds, preferably between about 5 ms and about 40 ms.

[0210] Therefore, the electric actuator VIB, controlled by the device controller, can provide a device DEV that generates low-frequency vibrations or stresses with perfect control over time and amplitude. The waveform of the pulses is well controlled, resulting in more reliable measurements and improved system reproducibility. Furthermore, the size and weight of the device DEV are reduced by using the controlled electric actuator VIB.

[0211] Furthermore, specifically, the ultrasonic transducer US is constructed and configured to transmit and receive ultrasonic signals controlled by the device controller 10. Specifically, the device controller 10 is constructed and configured to control the range and frequency of the transmitted ultrasonic signals. While generating low-frequency pulses onto the patient's skin, the transducer US transmits and receives ultrasonic signals to track the propagation of the generated shear waves. Tracking the shear waves allows measurements to be performed by determining the viscoelasticity of the medium. In fact, shear waves have a special property: their velocity depends on the viscoelasticity of the medium they have traversed. The harder the liver (and therefore the higher the degree of fibrosis), the faster the shear waves propagate.

[0212] Furthermore, when the device DEV includes more than one transducer, the device controller 10 can control the frequency of the transducer.

[0213] Furthermore, according to one aspect of the invention, the ultrasonic transducer US is elongated, for example, elliptical, rectangular, cylindrical or ellipsoidal, with a length between about 2 and about 20 mm, preferably about 11 mm, and a width between about 1 and about 10 mm, preferably about 5 mm.

[0214] According to one aspect of the invention, the ultrasonic transducer US is preferably conical or tapered, with an angle between about 10 and about 80 degrees.

[0215] Furthermore, according to one embodiment of the invention, the device controller 10 includes a touchscreen, a keyboard, and an optional mouse. Additionally, by connecting the device controller 10 to the ultrasonic probe 1 via a flexible cable 11, an operator can read information provided by the ultrasonic probe 1 through a display screen (also referred to as an "operator interface").

[0216] In another embodiment of the invention, the device controller 10 may delete measurements, and / or change the detection type (elastography or ultrasound), and / or add comments or measurements, and / or change the ultrasound gain and / or...

[0217] The present invention also relates to a method for measuring the viscoelasticity of a viscoelastic medium (MET) using the apparatus described above (DEV), wherein the medium has an ultrasonic signal after ultrasonic irradiation.

[0218] Figure 4 An example of the steps of the MET method for measuring the viscoelasticity of viscoelastic media is shown.

[0219] like Figure 4 As shown, the method MET includes positioning an ultrasonic transducer US 100 in contact with the viscoelastic medium to be measured.

[0220] Then, the method MET involves an operator applying a first force 101 to the medium to be measured using an ultrasound probe 1. Generally, for assessing liver fibrosis, the ultrasound transducer US applies force at the site covering the ribs.

[0221] According to another aspect of the invention, the method MET includes measuring a first force applied by the ultrasonic probe 102 to the medium to be measured, and then comparing the measurement result of the first force with a minimum contact force threshold. According to one aspect of the invention, the minimum contact force threshold is equal to 0.5 N.

[0222] According to another aspect of the invention, the method MET includes step 103 of comparing the measured contact force with a maximum contact force threshold.

[0223] Then, the method MET includes generating a contact ready signal 104 by the signal generator 9 based on a comparison of the measured contact force with a predefined force threshold. To recap, the contact ready signal is set when the ultrasonic probe 1 contacts the medium to be analyzed. The contact ready signal is emitted when the contact force is higher than a minimum contact force threshold. According to one embodiment, the contact ready signal is emitted when the contact force is between the minimum and maximum contact force thresholds.

[0224] According to one aspect of the invention, the method MET includes step 105 of illuminating at least one light-emitting diode (LED) of the ultrasonic probe 1, wherein the LED is illuminated only when a contact ready signal is set.

[0225] According to one aspect of the invention, the method MET further includes a step 106 of activating ultrasonic signals. Thus, the ultrasonic transducer US transmits and receives ultrasonic signals to generate an image of the region of interest. We note that the ultrasonic transducer US activates the transmission and reception of ultrasonic signals only when a contact-ready signal is set.

[0226] According to one aspect of the invention, the method MET includes step 107a of displaying a positioning device only when a contact-ready signal is issued. The positioning device is a tool used by an operator to locate the viscoelastic tissue to be measured; examples of the positioning device are images, guide tools, or other indicators.

[0227] According to one aspect of the invention, the method MET includes a step 107 of refreshing an ultrasonic image, wherein the display unit displays the ultrasonic image only when a contact ready signal is set.

[0228] According to one aspect of the invention, the method MET includes a step 108 of subsequently guiding with a guide indicator, refreshing the guide indicator only when a contact ready signal is set.

[0229] According to one aspect of the invention, the method MET includes step 109 of restricting access to at least one command provided by the device controller 10 when a contact ready signal is set.

[0230] According to one aspect of the invention, the method MET includes step 110, which involves activating the writing of information into the probe memory by the ultrasonic probe 1 when a contact ready signal is set.

[0231] The method MET includes an operator applying a second force 111 to a medium using an ultrasonic probe 1, the second force 111 being greater than a first force 101. According to another aspect of the invention, the method MET includes measuring the second force applied by the ultrasonic probe 1. The measured result of the second force is then compared with a minimum measurement force threshold. The value of the second force can also be compared with a maximum measurement force threshold.

[0232] According to one aspect of the invention, the minimum measuring force threshold is equal to 4.0 N. According to another aspect of the invention, the maximum measuring force threshold is equal to 8.0 N.

[0233] According to one aspect of the invention, the method MET includes generating a measurement ready signal 111 using a signal generator 9 if the measured second force is greater than a minimum measured force threshold.

[0234] According to one embodiment of the present invention, when the measured second force is between the minimum and maximum measured force thresholds, the signal generator sets a measurement ready signal 111.

[0235] According to one aspect of the invention, the method includes step 112 of illuminating at least one light-emitting diode (LED) of the ultrasonic probe 1 when a measurement ready signal is set.

[0236] According to one aspect of the invention, the method MET includes step 113 of generating low-frequency pulses onto a patient's skin. The low-frequency pulses are generated by movement of the entire probe 1, the movement being produced by an electric actuator VIB. The electric actuator VIB is controlled by a device controller 10. The application of the low-frequency pulses according to step 113 is triggered only when a measurement-ready signal from a signal generator 9 is set.

[0237] According to one aspect of the invention, the method MET further includes step 114 of transmitting and receiving ultrasonic signals using an ultrasonic transducer US to track the propagation of a shear wave, said shear wave being generated by generating low-frequency pulses 113 onto the patient's skin. In practice, the propagation speed of the shear wave depends on the viscoelasticity of the propagation medium. The harder the liver, the faster the shear wave propagates. Displacement within the liver during shear wave propagation is measured using the ultrasonic transducer US and by employing cross-correlation techniques on the radio frequency ultrasonic signals.

[0238] In addition, according to one aspect of the invention, method MET includes step 115 of deactivating the combined treatment of device DEV when a contact ready signal is set. Here, "combined treatment" refers to another type of examination combined within the device. For example, combined treatment is an electrocardiogram (ECG) or ultrasound imaging. In a non-limiting embodiment of the invention, device DEV has two probes, each for a treatment: a first ultrasound probe for elastography and a second ultrasound probe for ultrasound imaging, also referred to as an imaging probe. In this case, the contact ready signal is used to activate or deactivate one of these probes. For safety reasons, it is important that the maximum acoustic output power allowed for a given application is not exceeded. Therefore, it is important that both probes of device DEV emit ultrasound signals simultaneously. Furthermore, using two probes simultaneously (the ultrasound probe for elastography and the imaging probe) will undoubtedly produce spurious data in the acquisition of both ultrasound signals, as the signals from each probe will interfere. In a non-limiting embodiment of the invention, when the contact ready signal is set, one treatment is deactivated while the other treatment is activated.

[0239] The method MET includes step 116, which measures the viscoelasticity of the medium to be analyzed, as described in U.S. Patent No. 2005 / 0203398.

[0240] Furthermore, according to one aspect of the invention, an elastic intermediate medium (not shown) transparent to ultrasound is placed between the device DEV and the patient's skin. According to one aspect of the invention, the intermediate medium is a polyacrylamide-type synthetic polymer. Additionally, an adhesive material or glue may be placed between the intermediate medium and the medium under study to obtain a sliding or linking interface. Moreover, the intermediate medium is innovative because it is transparent not only to ultrasound but also to low-frequency waves. The intermediate medium is selected to have an elasticity close to that of the medium under study to adjust impedance and thereby transmit maximum energy to the medium under study. The intermediate medium can also be compressed so that its elastic modulus, which varies non-linearly, becomes similar to that of the medium under study. This last suggestion is an original technique for measuring the elasticity of a medium: it involves altering the elasticity of the intermediate medium until maximum energy is transmitted. The elasticity obtained in this way is close to that of the medium.

[0241] According to one aspect of the invention, in standard echocardiography mode, an ultrasound probe 1 is used to acquire approximately 20 ultrasound signals per second of tissue or medium. The envelope of these ultrasound signals is displayed on an alphanumeric display screen 7. The current signal is encoded into grayscale and logarithmic scales to form an image called an A-mode image. The signals can be arranged side-by-side to form an image called an M-mode image, which contains ultrasound signals acquired within a given time period, such as 5 seconds. According to one aspect of the invention, the ultrasound probe 1 is equipped with a positioning system to know the position of the acquired signal as the operator moves the ultrasound probe 1 on the surface of the tissue or medium, thereby reconstructing an image of the medium to be measured. Furthermore, according to one aspect of the invention, the alphanumeric display screen 7 refreshes the ultrasound image only when a contact-ready signal is set. According to another aspect of the invention, the ultrasound image is displayed only on the screen of the device controller 10.

Claims

1. A method for measuring the viscoelasticity of a viscoelastic medium, the method comprising the following steps: The probe is positioned in contact with the viscoelastic medium, the probe extends along the longitudinal axis and is adapted to perform transient elastic imaging measurements, and the probe includes: shell, At least one ultrasonic transducer is disposed at the tip of the probe and adapted to generate ultrasonic waves, the at least one ultrasonic transducer being fixed to the housing such that the at least one ultrasonic transducer does not move relative to the housing. A force sensor, configured to measure the force applied by the tip of the probe, and A vibrator, arranged inside the housing and adapted to generate low-frequency waves, The contact force is measured by the force sensor, and the contact force represents the force exerted by the tip of the probe on the viscoelastic medium when the tip of the probe is positioned in contact with the viscoelastic medium. When the measured contact force is higher than the minimum measurement force threshold, the probe generates a measurement ready signal. When the measurement ready signal is generated, the transient elastography measurement is triggered by generating a shear wave in the viscoelastic medium by emitting the low-frequency wave through the vibrator. The low-frequency wave is transmitted to the viscoelastic medium via the at least one transducer, and the propagation of the shear wave in the viscoelastic medium is tracked by emitting multiple ultrasonic pulses using the at least one ultrasonic transducer.

2. The method according to claim 1, wherein the at least one ultrasonic transducer is fixed to the force sensor.

3. The method of claim 2, wherein the at least one ultrasonic transducer, the force sensor, and the vibrator are aligned along the longitudinal axis of the probe.

4. The method of claim 1, wherein the probe further comprises a component fixedly connected to the at least one ultrasonic transducer and the force sensor, such that the low-frequency wave generated by the vibrator is transmitted via the component to the at least one ultrasonic transducer to generate the shear wave transmitted by the at least one ultrasonic transducer to the viscoelastic medium.

5. The method of claim 4, wherein the component comprises the coil of the vibrator.

6. The method of claim 5, wherein the vibrator further comprises a permanent magnet surrounding the coil, and wherein the coil and the permanent magnet are movable relative to each other.

7. The method of claim 4, wherein the component is connected to the vibrator.

8. The method of claim 4, wherein the component comprises a rod.

9. The method of claim 4, wherein the at least one transducer is fixed to the force sensor such that the low-frequency wave generated by the vibrator is transmitted through the force sensor to the at least one ultrasonic transducer to generate a shear wave transmitted by the at least one ultrasonic transducer to the viscoelastic medium.

10. The method of claim 9, wherein the at least one transducer and the force sensor are fixed to the tip of the probe.

11. The method of claim 1, wherein the probe further comprises a component fixedly connected to the at least one ultrasonic transducer, the force sensor, and a portion of the vibrator, such that the low-frequency wave generated by the vibrator is transmitted via the component to the at least one ultrasonic transducer to generate the shear wave transmitted by the at least one ultrasonic transducer to the viscoelastic medium.

12. The method of claim 1, wherein the force sensor is a strain gauge.

13. The method of claim 1, further comprising the following steps: The measurement ready signal is displayed on the monitor.

14. The method of claim 13, wherein the display is an LED that displays the measurement ready signal.

15. The method according to claim 1, wherein, The measurement ready signal is generated when the measured contact force is between the minimum measurement force threshold and the maximum measurement force threshold, wherein the minimum measurement force threshold is between 1.0N and 6.0N, and the maximum measurement force threshold is between 6.0N and 20.0N.

16. The method of claim 1, wherein the transient elastography measurement is manually triggered after the measurement ready signal is generated.

17. An apparatus for measuring the viscoelasticity of a viscoelastic medium, said viscoelastic medium having an ultrasonic signal after being subjected to an ultrasonic pulse, said apparatus comprising: A probe extending along a longitudinal axis and adapted to perform transient elastography measurements, and the probe comprising: shell; At least one ultrasonic transducer is disposed at the tip of the probe and adapted to generate ultrasonic waves, the at least one ultrasonic transducer being fixed to the housing such that the at least one ultrasonic transducer does not move relative to the housing. A vibrator, the vibrator being arranged inside the housing and adapted to generate low-frequency waves; A force sensor configured to measure the force applied by the tip of the probe, the force representing the contact force applied by the tip of the probe to the viscoelastic medium when the tip of the probe is positioned in contact with the viscoelastic medium; Signal generator; in A component is provided that is fixedly connected to at least one ultrasonic transducer and the force sensor, such that the low-frequency wave generated by the vibrator is transmitted via the component to the at least one ultrasonic transducer to generate a shear wave transmitted by the at least one ultrasonic transducer to the viscoelastic medium. The signal generator is configured and arranged to generate a measurement-ready signal when the measured contact force is higher than a minimum measurement force threshold, informing the operator of the probe to perform a transient elastography measurement. The transient elastography measurement is performed by generating the shear wave in the viscoelastic medium by emitting the low-frequency wave using the vibrator, and the shear wave is transmitted to the viscoelastic medium via the at least one transducer, and the propagation of the shear wave in the viscoelastic medium is tracked by emitting a plurality of ultrasonic pulses using the at least one ultrasonic transducer.

18. The apparatus of claim 17, wherein the at least one ultrasonic transducer is fixed to the force sensor.

19. The apparatus of claim 17, wherein the at least one ultrasonic transducer, the force sensor, and the vibrator are aligned along the longitudinal axis of the probe.

20. The apparatus of claim 17, wherein the component comprises the coil of the vibrator.

21. The apparatus of claim 20, wherein the vibrator further comprises a permanent magnet surrounding the coil, and wherein the coil and the permanent magnet are movable relative to each other.

22. The apparatus of claim 17, wherein the component is fixedly connected to a portion of the vibrator.

23. The device of claim 17, wherein the component comprises a rod.

24. The apparatus of claim 23, wherein the rod is connected to the vibrator, the low-frequency wave is transmitted to the at least one ultrasonic transducer via the rod through the fixed relationship between the rod and the at least one ultrasonic transducer, the rod being included within the housing.

25. The apparatus of claim 17, wherein the at least one transducer is fixed to the force sensor such that the low-frequency wave generated by the vibrator is transmitted via the force sensor to the at least one ultrasonic transducer to generate the shear wave transmitted by the at least one ultrasonic transducer to the viscoelastic medium.

26. The apparatus of claim 17, wherein the at least one transducer and the force sensor are fixed to the tip of the probe.

27. The apparatus of claim 17, wherein the force sensor is a strain gauge.

28. The apparatus of claim 17, further comprising a display including LEDs for displaying the measurement ready signal.

29. The apparatus of claim 17, wherein the signal generator is configured to generate the measurement ready signal when the measured contact force is between a minimum measurement force threshold and a maximum measurement force threshold, wherein the minimum measurement force threshold is between 1.0 N and 6.0 N, and the maximum measurement force threshold is between 6.0 N and 20.0 N.

30. A method for measuring the viscoelasticity of a viscoelastic medium, the method comprising the following steps: The probe is positioned in contact with the viscoelastic medium, the probe extends along the longitudinal axis and is adapted to perform transient elastic imaging measurements, and the probe includes: shell, At least one ultrasonic transducer is disposed at the tip of the probe and is fixed to the housing such that the at least one ultrasonic transducer does not move relative to the housing. A force sensor, configured to measure the force applied by the probe to the viscoelastic medium, and The moving part and the first and second springs, The contact force is measured by the force sensor, and the contact force represents the force exerted by the tip of the probe on the viscoelastic medium when the tip of the probe is positioned in contact with the viscoelastic medium. A measurement ready signal is generated based on the measured contact force through a signal generator coupled to the force sensor. When the measured contact force is greater than a measurement force threshold, the signal generator sets the measurement ready signal. When the measurement ready signal is greater than the contact force threshold, the operator of the probe is notified that the probe has been correctly positioned on the viscoelastic medium, and the transient elastic imaging measurement is triggered in the following manner: Shear waves are generated in the viscoelastic medium by causing the at least one ultrasonic transducer to move relative to the viscoelastic medium. Multiple ultrasonic pulses are emitted by the at least one ultrasonic transducer to track the propagation of the shear wave in the viscoelastic medium, and the backscattered ultrasonic signal associated with the reflection of the emitted ultrasonic pulses in the viscoelastic medium is detected by the at least one ultrasonic transducer. The viscoelasticity of the viscoelastic medium is determined based on the propagation of the shear wave tracked using the detected backscattered signal. The movable portion is connected to a first end of each of the first and second springs, and the movable portion is movable within the probe along the longitudinal axis to resist the bias of the springs.

Images