IMPLANTABLE ULTRASONIC TRANSDUCER

Abstract

The present invention relates to an implantable ultrasonic transducer comprising a first device for generating ultrasound, a second device for receiving ultrasound, and a circuit board, wherein the device for generating ultrasound is formed from a piezoelectric polymer, which is integrated in the circuit board. The invention also relates to a medical device which can be introduced into the body and comprises an ultrasonic transducer of this type.

Claims

1. An implantable ultrasonic transducer comprising a first device for generating ultrasound, a second device for receiving ultrasound, and a circuit board, wherein the second device for receiving ultrasound is formed from a piezoelectric polymer, which is integrated in the circuit board.

2. The implantable ultrasonic transducer according to claim 1, wherein the second device for receiving ultrasound is formed from a plurality of piezoelectric elements formed from the piezoelectric polymer, wherein the plurality of piezoelectric elements are integrated in the circuit board.

3. The implantable ultrasonic transducer according to claim 1, wherein the first device for generating ultrasound is formed from a piezoelectric material, in particular a ceramic or a crystal.

4. The implantable ultrasonic transducer according to claim 1, wherein the first device for generating ultrasound is arranged at the circuit board.

5. The implantable ultrasonic transducer according to claim 1, wherein the first device for generating ultrasound and the second device for receiving ultrasound are electrically contactable independently of one another.

6. The implantable ultrasonic transducer according to claim 1, wherein the circuit board comprises at least one electrical conductor track, which electrically contacts the second device for receiving ultrasound.

7. The implantable ultrasonic transducer according to claim 1, wherein the first device for generating ultrasound has a metal layer on each of the upper side and the bottom side.

8. The implantable ultrasonic transducer according to claim 7, wherein the first device for generating ultrasound is arranged with the upper side on the circuit board, wherein the metal layer on the upper side electrically contacts the second device for receiving ultrasound.

9. The implantable ultrasonic transducer according to claim 1, wherein the first device for generating ultrasound has a metal layer on each of two mutually opposed side faces.

10. The implantable ultrasonic transducer according to claim 1, wherein the circuit board is flexible.

11. The implantable ultrasonic transducer according to claim 3, wherein the piezoelectric material is designed substantially in the form of a hollow cylinder, wherein the outer side of the hollow cylinder comprises a metal layer, the surface delimiting the aperture through the hollow cylinder is coated with metal or the aperture through the hollow cylinder is filled with metal, and wherein the circuit board substantially fully surrounds the metal layer on the outer side.

12. The implantable ultrasonic transducer according to claim 1, wherein the piezoelectric polymer comprises or consists of polyvinylidene fluoride or a copolymer thereof.

13. The implantable ultrasonic transducer according to claim 1, wherein the implantable ultrasonic transducer is coated at least in part with a biocompatible coating or polymer comprising a polydimethylsiloxane or a polyurethane.

14. A medical device that can be introduced, in particular implanted, in the body, comprising an implantable ultrasonic transducer according to claim 1.

15. The medical device according to claim 14 that can be introduced in the body, wherein the medical device is formed as an active implant, a sensor, a loop recorder or a catheter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Further features and advantages of the present invention will be explained hereinafter with reference to the figure description of exemplary embodiments. The figures show:

[0046] FIGS. 1-6 show various embodiments of the implantable ultrasonic transducer according to the present invention.

DETAILED DESCRIPTION

[0047] A significant concept of the present invention is the separation of the detection of the sound generation in ultrasonic transducers. Only a thin layer is used for the detection and is fixedly connected on a sound generator.

[0048] A further inventive concept is the integration of the piezoelectric elements that are used for the detection in a flexible circuit board. The detectors are thus directly electrically attached and may be directly connected to electric components without additional mounting and connection technology.

[0049] The present invention allows a further miniaturization and simplification in the structure with much lower costs, and therefore further applications are possible. A further advantage is the use of biocompatible materials.

[0050] In particular, as a result of the present invention, the construction of ultrasonic transducers for catheters and implants is considerably simplified and may be further miniaturized. The costs of the connection technology can be considerably reduced.

[0051] FIG. 1 shows an embodiment of the implantable ultrasonic transducer according to the present invention. A thin polymer film 4 is applied to a sound generator formed from a piezoelectric material 2, which is coated on the upper side 3 and the bottom side 1 with a metal layer. In the simplest case, this polymer film is formed from PVDF (polyvinylidene difluoride) or P(VDF-TrFE) (poly(vinylidene fluoride-co-trifluoroethylene), which is made piezoelectric by suitable polarisation. This polymer film, however, is preferably a flexible circuit board which for example is formed from polyimide or LCP (liquid crystal polymer) or another base material for flexible circuit boards. This has the advantage that the flexible circuit board already has electrical conductor tracks which are connected in a suitable way to the metal layers 1, 3 and 6. Due to these conductor tracks, the piezoelectric materials 2 and 5 are electrically connected to a suitable electrical circuit for generating pulses for sound generation and for signal processing in the detection of reflected sound signals from the bodily tissue. In this case, for example, the polymer P(VDF-TrFE) 5 is introduced into suitable indentations 5 in the flexible circuit board 4. This can be achieved either by way of a heating process (P(VDF-TrFE) is thermoplastic and melts at approximately 150° C.) or by applying a highly viscous solution of P(VDF-TrFE) in a suitable solvent by way of screen printing or using a doctor blade. Before applying the metallization 6, the P(VDF-TrFE) is polarised by means of corona discharge in order to make it piezoelectric. The metal structure for deriving the signals is then applied and structured. This can be achieved by means of sputtering and lift-off. Lastly, the entire transducer is coated with a thin (biocompatible) coating 7 or with silicone (PDMS) 7 so that the conductor tracks 6 are not short-circuited by the bodily tissue.

[0052] In this case, the components of the ultrasonic transducer according to the present invention preferably have the following dimensions: [0053] thickness of the sound generator 2: 0.1 mm to 2 mm [0054] thickness of the polymer film/flexible circuit board 4: 0.01 mm to 0.1 mm [0055] dimensions of the piezoelectric elements 5: 0.01 mm to 5 mm

[0056] In the embodiment of the ultrasonic transducer according to the present invention shown in FIG. 2, the flexible circuit board consisting of the base material 4, the piezoelectric elements 5, and the conductor tracks 6 and 8 are first produced. This can be implemented in a production format typical for circuit boards (for example 300×450 mm or also even larger). The sound generator 2 is then glued to the rear face of the circuit board. The adhesive layer 9 may be electrically conductive all over or only at specific points, and therefore electrical contact for connecting the sound generator 2 to one of the conductor tracks 8 of the flexible circuit board is created.

[0057] This structure has advantages in particular if the circuit board also has other functions and the sound generator and the detector form only part of the circuit board.

[0058] If the sound generator 2 has electrical contacts at the end faces, as shown in FIG. 3, a higher component of transverse waves can be coupled into the bodily tissue. Such an arrangement is only possible if the detector and the sound generator are separate.

[0059] The full structure is shown schematically in FIG. 4. The piezoelectric elements 5 are integrated in the circuit board 4 and connected via the conductor tracks 8. The conductor tracks 6 running on the upper side are only indicated schematically. The sound generator 2 is adhesively bonded onto the circuit board. The order of the illustration is reversed here as compared to the cross sections.

[0060] This arrangement may be integrated directly in a device. The circuit board can also be applied directly to the skin or can be mounted on the tip or the balloon of a catheter. Sound-absorbent materials can be mounted on the upper side of the sound generator 2 in order to achieve a higher energy transfer in the other direction towards the bodily tissue. Suitable sound-absorbent materials are polymers in general and elastomers in particular.

[0061] In another embodiment of the ultrasonic transducer according to the present invention shown in FIG. 5, the circuit board 4 with the integrated detectors or piezoelectric elements 5 is glued over a cylindrical sound generator 2.

[0062] A cylindrical transducer is used in the case of this concept. A metal face 1 is in this case formed as a wire in the centre of the piezoelectric material 2. The outer face of the cylinder 2 is metallized 3. In the simplest case, the metallization 3 is provided on the bottom side of the detector film or circuit board 4.

[0063] With the embodiment shown in FIG. 5, a cylindrical wave may advantageously be produced, which allows improved reflection behaviour in the vessel and thus a more accurate measurement. This arrangement is therefore of interest in particular for use in catheters.

[0064] A catheter designed in such a way is shown schematically in FIG. 6. The catheter in this case comprises, at its distal end, the ultrasonic transducer according to the present invention comprising a flexible circuit or circuit board 4 with integrated piezoelectric elements 5 as ultrasound receiver and a coaxial cylindrical ultrasound generator 2. The catheter furthermore comprises a tip 9 (as mechanical termination without further function), a catheter tube 10, electronic components 11, one or more guide wires 12 (guide wire), and an insulated wire 13 for electrically contacting the ultrasound generator 2 (preferably with high voltage). The wire 13 can be connected here to the flexible circuit board 1 or can be guided separately by the catheter tube 10. The electronic components 11 are designed here in particular for the signal processing of the ultrasound receiver 4, 5 and can preferably be mounted on the flexible circuit board 4. Such a catheter preferably has a diameter in the range of from 1.5 mm to 4 mm.

[0065] It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teachings of the disclosure. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention, which is to be given the full breadth thereof. Additionally, the disclosure of a range of values is a disclosure of every numerical value within that range, including the end points.