Transient elastography probe with sealing membrane integrated into ultrasound transducer

Abstract

One aspect of the present invention relates to a transient elastic imaging probe (100), comprising: a probe body (101); an ultrasonic transducer (103), configured to generate an ultrasonic beam along an axis, the ultrasonic beam being generated from a surface (107) of the ultrasonic transducer (103); a vibrator (102), located inside the probe body (101) and arranged to cause the ultrasonic transducer (103) to move along a predetermined axis; the ultrasonic transducer (103) is mounted on the vibrator (102) so that the predetermined axis and the axis of the ultrasonic beam coincide with each other, characterized in that the transient elastic imaging probe comprises a sealing membrane (104) surrounding the outer contour of the ultrasonic transducer (103).

Description

Technical Field

[0001] The technical field of the present invention is a transient elastography probe, in particular, a transient elastography probe including an ultrasonic transducer integrated with a sealing membrane.

[0002] The present invention relates to a transient elastography probe which can be used to measure the viscoelasticity of human or animal tissues, and in particular to a transient elastography probe comprising an ultrasonic transducer provided with a sealing film. Background Art

[0003] Several liver diseases can be diagnosed by evaluating the viscoelastic properties of liver tissue. Chronic viral hepatitis, alcoholic and non-alcoholic steatohepatitis, autoimmune hepatitis, viral hepatitis, primary biliary cirrhosis are all causes of progressive changes in the liver called cirrhosis. In some cases, this increase in stiffness, also called fibrosis, can lead to cirrhosis and liver dysfunction, with serious consequences for the patient.

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

[0005] The applicant has developed and marketed a Devices of the type described herein (see, for example, patent documents EP1169636 and EP1531733) which use an elastography technique developed by the applicant called "Vibration Controlled Transient Elastography" (VCTE) to measure liver stiffness.

[0006] In VCTE applications, the measurement of liver stiffness is based on the measurement of the propagation velocity of the transient shear wave in the examined tissue. In order to perform this measurement, a specific probe has been developed. The probe includes at least one vibrator and at least one ultrasonic transducer.

[0007] For example, in In the probe, a vibrator displaces the ultrasound transducer and pushes it toward the patient's body. This pulsed motion generates a transient shear wave that propagates within the liver. The displacement caused by the propagation of the shear wave is then detected by sending high-frequency, short-duration ultrasound pulses into the medium under investigation.

[0008] During the examination, the ultrasound transducer is then in direct contact with the patient's body or with a water-based gel that facilitates ultrasound transmission. Therefore, the ultrasound transducer must be waterproof to prevent its degradation while enabling effective and painless examination of the patient. Summary of the invention

[0009] The present invention provides a solution to the above mentioned problems by making it possible to perform a transient elastography examination which is painless for the patient and without the risk of degradation of the probe used.

[0010] One aspect of the present invention relates to a transient elastography probe, comprising:

[0011] -Probe body;

[0012] - an ultrasonic transducer configured to generate an ultrasonic beam along an axis, the ultrasonic beam being generated from a face of the ultrasonic transducer;

[0013] - a vibrator located inside the probe body and arranged to cause movement of the ultrasound transducer along a predetermined axis;

[0014] The ultrasonic transducer is mounted on the vibrator so that the predetermined axis and the axis of the ultrasonic beam coincide with each other, and is characterized in that the transient elastography probe comprises a sealing film surrounding the outer contour of the ultrasonic transducer.

[0015] Thanks to the invention, the ultrasound transducer is surrounded by a membrane that makes the probe waterproof, thus avoiding damage to it during the examination. The membrane also makes it possible to cover the corners on the face of the ultrasound transducer in order to make the examination painless for the patient. Finally, the membrane simplifies obtaining sufficient dielectric insulation to ensure that the probe complies with the requirements of the relevant current regulations.

[0016] In addition to the features already mentioned in the preceding paragraphs, the probe according to one aspect of the invention may have one or more of the following complementary features, which may be considered individually or in all technically possible combinations thereof.

[0017] Advantageously, the ultrasonic transducer and the membrane assembly constitute a detachable end piece.

[0018] Therefore, the ultrasonic transducer used can be adapted to the patient, and the diameter of the probe portion that contacts the patient varies according to the morphology of the patient.

[0019] Advantageously, the ultrasound transducer has an axis of symmetry corresponding to the axis of the ultrasound beam.

[0020] Advantageously, the ultrasound transducer is connected to the probe body via a membrane.

[0021] Advantageously, the membrane is made of an elastomer.

[0022] Therefore, the membrane is flexible and deforms when the ultrasound transducer moves.

[0023] Advantageously, the membrane is made of a silicone-type elastomer.

[0024] Advantageously, the portion of the membrane in contact with the face of the ultrasound transducer forms an acoustic lens configured to focus the ultrasound beam.

[0025] The ultrasound beam is thus better focused, which makes it possible to obtain more precise measurements. In this case, the portion of the membrane in front of the face of the ultrasound transducer will be convex or concave, depending on whether the propagation speed of ultrasound in the lens is less or greater than the propagation speed of ultrasound in water.

[0026] Advantageously, the portion of the membrane that is in contact with the face of the ultrasound transducer is convex.

[0027] Advantageously, the portion of the membrane that is in contact with the face of the ultrasound transducer is concave.

[0028] Advantageously, the membrane is made of an electrically insulating material.

[0029] Thus, the membrane enables better dielectric insulation of the probe. In practice, in existing configurations, dielectric insulation is more difficult to achieve, since the ultrasound transducer is provided with a membrane that covers only the face of the ultrasound transducer. Moreover, dielectric leakage may occur on the periphery of the membrane.

[0030] Advantageously, the membrane is bonded to the ultrasound transducer.

[0031] Advantageously, the portion of the membrane between the ultrasound transducer and the probe body is deformable.

[0032] Thus, when the ultrasound transducer is displaced under the action of a vibrator located in the probe body, the membrane is deformed.

[0033] Advantageously, the outer diameter of the portion of the membrane in contact with the face of the ultrasound transducer is between 3 mm and 25 mm.

[0034] Advantageously, the thickness of the portion of the membrane in contact with the face of the ultrasound transducer is between 50 μm and 5 mm.

[0035] Advantageously, all or part of the ultrasound transducer has a frustoconical shape, the face of the ultrasound transducer corresponding to the base of the frustoconical portion of minimum area.

[0036] Thus, the surface in contact with the patient is not too wide, which makes it easier to accommodate the face of the ultrasound transducer in the intercostal space of the patient, while providing space at the level of the wider back face to accommodate the electronics.

[0037] The invention and its various applications will be better understood by reading the following description and by examining the drawings accompanying it. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings are presented for illustrative purposes and are not intended to limit the invention.

[0039] Figure 1A A schematic diagram of a transient elastography probe according to the first aspect of the present invention is shown.

[0040] Figure 1B A schematic diagram of a transient elastography probe according to the first aspect of the present invention is shown, from which an end piece consisting of an ultrasonic transducer covered with a sealing film is removed.

[0041] Figure 2A A schematic diagram showing a conical ultrasound transducer and a circular membrane is shown.

[0042] Figure 2B Shows Figure 2A Schematic diagram of an ultrasonic transducer shown in FIG. , the ultrasonic transducer is covered with a detachable end piece Figure 2A The membrane shown in .

[0043] Figure 3A A schematic diagram showing an ultrasonic wave emitted by an ultrasonic transducer in the absence of a membrane, and more specifically a schematic diagram showing an ultrasonic wave reflected at a point F located at a distance d from the ultrasonic transducer.

[0044] Figure 3B A schematic diagram showing an ultrasonic wave emitted by an ultrasonic transducer covered with a membrane constituting an acoustic lens, and more specifically a schematic diagram showing an ultrasonic wave reflected at a point F located at a distance d from the ultrasonic transducer and constituting a focus of the acoustic lens.

[0045] Figure 3C The ultrasonic transducer is shown in FIG. 1 and FIG. 2 when the ultrasonic transducer is not provided with a membrane and when the ultrasonic transducer is provided with a membrane. Figure 3A and 3B Diffraction pulse response at point F. DETAILED DESCRIPTION

[0046] Unless otherwise stated, identical elements appearing in different drawings have a single reference number.

[0047] A first aspect of the present invention relates to a transient elastography probe.

[0048] A "transient elastography probe" is a probe that implements the VCTE (Vibration Controlled Transient Elastography) technique, i.e., a probe that can estimate the propagation velocity of low-frequency shear waves in the medium under investigation by measuring the local displacement of the medium during the passage of the shear wave using ultra-high frequency ultrasound. The propagation velocity makes it possible to estimate the viscoelastic parameters of the medium.

[0049] In the remainder of the description, the terms "probe" and "transient elastography probe" will be used indiscriminately.

[0050] exist Figure 1A A probe 100 according to a first aspect of the present invention is shown in FIG.

[0051] The probe 100 comprises:

[0052] -Probe body 101;

[0053] - a vibrator 102;

[0054] - an ultrasonic transducer 103; and

[0055] -Membrane 104.

[0056] The ultrasonic transducer 103 is configured to generate an ultrasonic beam. The ultrasonic beam is generated at the level of a face 107 of the ultrasonic transducer 103 .

[0057] For example, the ultrasound transducer 103 has an axis of symmetry A. The propagation axis of the ultrasound beam is parallel to the axis of symmetry A.

[0058] For example, the ultrasonic transducer 103 has Figure 2A The truncated cone shape or cylindrical shape shown in , and the axis of the cone or the axis of the cylinder is the symmetry axis A.

[0059] The ultrasound transducer has a length of, for example, greater than 10 mm.

[0060] exist Figure 2A In FIG. 1 , face 107 corresponds to the small base or minimum area base of the conical ultrasonic transducer 103. In practice, a truncated cone has two bases located in parallel planes, called the small base and the large base, the area of ​​the small base being smaller than the area of ​​the large base.

[0061] exist Figure 1A , the surface 107 corresponds to the base of the cylindrical ultrasonic transducer 103 which is not in contact with the vibrator 102 .

[0062] The probe body 101 has a shape that enables the probe 100 to be held in the hand of an operator during transient elastography examination. For example, the probe body 101 has a shape of a rotational solid having the same axis as the symmetry axis A of the ultrasonic transducer 103. Specifically, the probe body 101 has a cylindrical shape, and the symmetry axis A of the ultrasonic transducer 103 is the axis of the cylinder. The probe body 101 includes a circular outer end 108.

[0063] The size of the probe body 101 is selected to enable an operator to hold the probe 100 in the hand. For example, in the case where the probe body 101 is cylindrical, the outer diameter of the probe body 101 is between 20 mm and 80 mm.

[0064] The vibrator 102 is located inside the probe body 101 , and the ultrasonic transducer 103 is mounted on the vibrator 102 .

[0065] The vibrator 102 is configured to cause a movement of the ultrasound transducer 103 along a predetermined axis coinciding with the symmetry axis A of the ultrasound transducer 103. This movement makes it possible to push the ultrasound transducer 103 against the patient's body during a transient elastography examination and thus generate low-frequency shear waves.

[0066] The ultrasound transducer 103 is in contact with the patient's body at its face 107 .

[0067] like Figure 2A As shown, the conical ultrasound transducer 103 contacts the patient at the small base of the truncated cone, which means that the face 107 has a smaller surface than the back side corresponding to the large base of the truncated cone, which facilitates positioning the probe 100 in the intercostal space of the patient while leaving enough room to accommodate electronic components at the back side.

[0068] The ultrasonic transducer 103 is covered with a membrane 104, which surrounds the outer contour of the ultrasonic transducer 103 and ensures sealing of the ultrasonic transducer 103. For example, the membrane 104 is bonded to the ultrasonic transducer 103. The membrane 104 can also be overmolded on the ultrasonic transducer 103.

[0069] The membrane 104 covers the entire ultrasonic transducer 103 so that dielectric leakage that occurs when the membrane 104 covers only the face 107 of the ultrasonic transducer 103 can be avoided.

[0070] A portion 105 of the membrane 104 covers a face 107 of the ultrasound transducer 103 .

[0071] The membrane 104 makes it possible to cover the corner points on the face 107 of the ultrasound transducer 103 in order to make the examination painless for the patient.

[0072] For example, the portion of the membrane 104 between the probe body 101 and the ultrasound transducer 103, and in particular the portion of the membrane 104 intended to be in contact with the patient, is deformable. Thus, when the ultrasound transducer 103 is displaced under the action of the vibrator 102 located in the probe body 101, the membrane 104 is deformed.

[0073] For example, the film 104 is made of an elastic material, thereby imparting elastic properties to the film 104. Specifically, the film 104 is made of silicone.

[0074] For example, the membrane 104 is made of an insulating material to ensure better dielectric insulation of the probe 100 .

[0075] according to Figure 1A In the embodiment shown in , the ultrasound transducer 103 is connected to the probe body 101 by means of a membrane 104 .

[0076] For example, the membrane 104 has a circular shape, and the contour of the membrane 104 is arranged on the periphery of the end 108 of the probe body 101. The end 108 of the probe body 101 includes, for example, a groove so that the contour of the membrane 104 can be inserted. The membrane 104 can be further bonded or clamped on the probe body 101, for example.

[0077] Therefore, the ultrasonic transducer 103 and the membrane 104 assembly can be easily replaced and constituted as follows Figure 1B or Figure 2B A removable end piece 106 is shown.

[0078] Then, end pieces 106 of different sizes may be used to adapt the characteristics of the emitted ultrasound waves to the morphology of the patient. For example, the end piece 106 may include an ultrasound transducer 103 selected from the following ultrasound transducers:

[0079] - an ultrasonic transducer 103 having a center frequency of 8 MHz and a diameter of 3 mm;

[0080] - an ultrasonic transducer 103 having a central frequency of 5 MHz and a diameter of 5 mm, the end piece 106 equipped with this type of ultrasonic transducer being suitable for measuring the elasticity of the liver of a child or an adult of small size;

[0081] - an ultrasonic transducer 103 having a central frequency of 3.5 MHz and a diameter of 7 mm, an end piece 106 equipped with this type of ultrasonic transducer being suitable for measuring the elasticity of the liver of an adult human;

[0082] - an ultrasonic transducer 103 having a central frequency of 2.5 MHz and a diameter of 10 mm, an end piece 106 equipped with an ultrasonic transducer of this type being suitable for measuring the elasticity of the liver of obese adults;

[0083] - Ultrasonic transducer 103 with 1.5 MHz center frequency and 12 mm diameter.

[0084] In fact, the smaller the diameter of the ultrasonic transducer 103, the smaller the distance traveled in the medium by the ultrasonic wave emitted by the ultrasonic transducer 103. Therefore, in the case of an obese patient, the fat tissue layer between the skin and the liver is larger than that of a non-obese patient, so the diameter of the ultrasonic transducer 103 must be larger in order to measure in the liver rather than in the fat tissue.

[0085] The end piece 106 may be screwed or clamped onto the probe body 101 , for example.

[0086] For example, the end piece 106 may include an LED-type diode.

[0087] The outer diameter of the portion 105 of the membrane 104 in contact with the face 107 of the ultrasonic transducer 103 is, for example, between 3 mm and 25 mm.

[0088] The portion 105 of the membrane 104 that is in contact with the face 107 of the ultrasound transducer 103 has a thickness of, for example, between 50 μm and 5 mm.

[0089] like Figure 3B As shown, portion 105 of membrane 104 may constitute an acoustic lens capable of focusing an ultrasound beam.

[0090] For clarity, in Figure 3B In FIG. 1 , the portion 105 of the membrane 104 is represented as being independent of the ultrasonic transducer 103 , but in reality, the portion 105 of the membrane 104 is in contact with the face 107 of the ultrasonic transducer 103 .

[0091] exist Figure 3A and 3B In the figure, the ultrasonic transducer 103 emits an ultrasonic beam, whose propagation direction is parallel to the symmetry axis A of the ultrasonic transducer 103 .

[0092] exist Figure 3B In , the ultrasound beam is focused by the acoustic lens at a point F located at a distance d from the portion 105 of the membrane 104, which point F constitutes the focus of the acoustic lens. All rays arrive at the focus F at the same time, which is advantageous in terms of the duration of the diffraction impulse response of the system.

[0093] exist Figure 3A In the absence of the portion 105 of the membrane 104, the path of the ultrasound beam is not deviated. The focus F is defined by the "natural" focusing of the piston-type ultrasonic transducer 103, with the disadvantage that the duration of the diffracted impulse response is greater than in the case of focusing using an acoustic lens.

[0094] exist Figure 3C] shows the diffraction pulse response at point F in the case where the ultrasound beam is not focused and in the case where the ultrasound beam is focused at point F by the portion 105 of the membrane 104 constituting the acoustic lens. V is the propagation velocity of ultrasound in the medium under consideration.

[0095] It can be noticed that in the case of focusing with a lens, the diffraction pulse response at a time close to the time equal to d / V is shorter, which is more beneficial for obtaining good axial and lateral resolution of the probe 100 .

[0096] In the presence of an acoustic lens, the intensity of the signal reflected by point F is also greater than in the absence of an acoustic lens, because the rays add coherently at focus F.

[0097] The diffracted pulse response at point F is more dispersed in time in the absence of an acoustic lens than in the presence of an acoustic lens because the ultrasound rays do not add perfectly coherently as they travel greater or lesser distances to reach focus F.

[0098] The acoustic lens can be concave or convex, depending on whether the speed of ultrasound propagation in the lens is slower or faster than the speed of ultrasound propagation in water.

Claims

1. A transient elastic imaging probe (100), comprising: Probe body (101); an ultrasonic transducer (103) configured to generate an ultrasonic beam along an axis, the ultrasonic beam being generated from a face (107) of the ultrasonic transducer (103) intended to be in contact with a patient's body; a vibrator (102) located inside the probe body (101) and arranged to cause the ultrasonic transducer (103) to move along a predetermined axis; The ultrasonic transducer (103) is mounted on the vibrator (102) so that the predetermined axis and the axis of the ultrasonic beam coincide with each other, characterized in that the ultrasonic transducer comprises a sealing film (104) surrounding the outer contour of the ultrasonic transducer (103) and covering the surface (107) of the ultrasonic transducer (103), wherein the portion (105) of the sealing membrane (104) in contact with the face (107) of the ultrasonic transducer (103) forms an acoustic lens configured to focus the ultrasonic beam to detect displacements caused by shear waves induced by the vibrator in the medium under investigation, The ultrasonic transducer (103) is connected to the probe body (101) via the sealing film (104), and a portion of the sealing film (104) between the ultrasonic transducer (103) and the probe body (101) is deformable, so that when the ultrasonic transducer (103) is displaced under the action of the vibrator (102), the sealing film (104) is deformed.

2. The probe (100) according to claim 1, characterized in that: The ultrasonic transducer (103) and the sealing membrane (104) form a detachable end piece (106).

3. The probe (100) according to claim 1 or 2, characterized in that: The ultrasonic transducer (103) has an axis of symmetry corresponding to the axis of the ultrasonic beam.

4. The probe (100) according to claim 1, characterized in that: The sealing film (104) is made of elastomer.

5. The probe (100) according to claim 4, characterized in that: The sealing film (104) is made of a silicone-type elastomer.

6. The probe (100) according to claim 5, characterized in that: The portion (105) of the sealing film (104) that contacts the surface (107) of the ultrasonic transducer (103) is convex.

7. The probe (100) according to claim 5, characterized in that: The portion (105) of the sealing film (104) that contacts the surface (107) of the ultrasonic transducer (103) is concave.

8. The probe (100) according to claim 1 or 2, characterized in that: The sealing film (104) is made of an electrically insulating material.

9. The probe (100) according to claim 1 or 2, characterized in that: The sealing film (104) is bonded to the ultrasonic transducer (103).

10. The probe (100) according to any one of claims 5 to 7, characterized in that: The outer diameter of the portion (105) of the sealing membrane (104) in contact with the surface (107) of the ultrasonic transducer (103) is between 3 mm and 25 mm.

11. The probe (100) according to any one of claims 5 to 7, characterized in that: The thickness of the portion (105) of the sealing film (104) in contact with the surface (107) of the ultrasonic transducer (103) is between 50 μm and 5 mm.

12. The probe (100) according to claim 1 or 2, characterized in that: All or part of the ultrasonic transducer (103) has a truncated cone shape, and the face (107) of the ultrasonic transducer (103) corresponds to the base of the truncated cone of minimum area.

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