JP2021049423A - Ultrasound catheter for kidney nerve - Google Patents

Abstract

To provide an ultrasound catheter for kidney nerves, the catheter that can efficiently heat and cauterize only a target portion where the kidney nerves are present, and also has no water-cooled system, has a simple structure and is miniaturized in comparison with conventional products, and thereby can be made to arrive at the inside of a thinner blood vessel.SOLUTION: An ultrasound catheter for kidney nerves of the present invention includes a catheter unit 2 comprising a catheter body 21 and an operation part 22, an ultrasonic vibration unit 1 arranged at the tip end of the distal side of the catheter unit 2, and control means (ultrasound control system 3) for controlling the ultrasonic vibration unit 1. The ultrasonic vibration unit 1 comprises a capacitive micromachined ultrasonic transducer (CMUT) array capable of applying a high intensity focused ultrasound (HIFU) for heating the kidney nerves and having a micromachine form.SELECTED DRAWING: Figure 2

Description

The present invention relates to an ultrasonic catheter for renal nerves that cauterizes and inactivates the cellular activity of renal nerves existing around the renal arteries of a living body by heating.

As a treatment and treatment method that does not impose a burden on the living body such as the human body (less load), catheter treatment is known in which a specific biological target site (treatment target site) is treated via a catheter inserted into a blood vessel from the lower limbs. (See Patent Document 1).

For example, when intractable hypertension develops due to a specific hormone (renin) secreted by the kidney, the sympathetic renal nerve is deactivated as a curative treatment. As a method of deactivating the nerve, in addition to a method of directly cutting or removing the sympathetic renal nerve by surgery, a high frequency (electromagnetic wave) is applied to the sympathetic renal nerve by using a catheter inserted into the blood vessel to the vicinity of the kidney. ) Or ultrasonic waves are used to ablate and inactivate active nerves (see Patent Documents 2 to 5).

Special Table 2015-526177 U.S. Pat. No. 7,617,005 Japanese Patent Application Laid-Open No. 2008-515544 Special Table 2013-509266 Special Table 2016-515014

By the way, in the method of irradiating a high frequency (Radio Frequency: RF) to ablate a part (target part) of a living body as described in Patent Documents 2 and 3, an electrode for transmitting high frequency is attached to the tip of the catheter. A plurality of electrodes are provided, and each electrode is brought into contact with the inner wall of the blood vessel of the renal artery to pass a high-frequency current or a pulse current to ablate nerves and the like. Therefore, after high-frequency irradiation, damage to the inner wall of the blood vessel (burns, etc.) may cause stenosis of the blood vessel. Further, since the ablation electrodes are scattered, there is a possibility that a portion that cannot be cauterized remains.

On the other hand, in the method of ablating the target part of the living body using ultrasonic vibration as described in Patent Documents 4 and 5, ultrasonic waves are irradiated to nerves and the like from the tip (distal part) of the catheter and heated. , Cauterize this. However, the piezoelectric element (piezo element) represented by PZT (lead zirconate titantate) used for irradiation has a large heat generation of the element itself at the time of irradiation, and the part other than the target renal nerve is also included. Since it is heated, it is necessary to circulate cooling water around the piezoelectric element to protect the inner wall of the blood vessel in contact with the element (keep it at 65 ° C. or lower). Therefore, there is a problem that it is difficult to miniaturize the area around the ultrasonic wave irradiation portion (piezoelectric element portion) at the tip of the catheter. In addition, since unfocused ultrasonic waves (Unfocused Ultrasound) are irradiated over a wide range, cells may be heated over a wide range and damage other nerves and cells.

The present invention is intended to overcome the above-mentioned drawbacks of the conventional method, and an object of the present invention is to provide an ultrasonic catheter for renal nerves capable of efficiently heating and cauterizing only a target portion in which a renal nerve is present. To provide. Another object of the present invention is to provide an ultrasonic catheter for renal nerves, which does not have a water cooling system, has a simple structure, is smaller than a conventional product, and can reach even a smaller blood vessel. To do.

The ultrasonic catheter for renal nerves of the present invention is a medical catheter inserted into a living body to inactivate renal nerve transmission in mammals.
A catheter unit consisting of a tubular catheter body and an operation unit arranged at a root portion on the proximal side of the catheter body, and an ultrasonic vibration unit arranged at the distal end portion on the distal side of the catheter body. A control means for controlling the ultrasonic vibration unit is provided.
The ultrasonic vibration unit is a capacitive ultrasonic transducer array (Capacitive) composed of a plurality of micromechanical ultrasonic vibration elements capable of irradiating high-intensity focused ultrasonic waves (High Intensity Focused Ultrasound) that heats the renal nerve. It is characterized by including a Micromachined Ultrasonic Transducer Array).

Further, the ultrasonic catheter for renal nerves of the present invention has a core sheath structure in which the catheter body is composed of a sheath serving as an outer cylinder and a shaft rotatably inserted inside the sheath.
The operation unit includes an ultrasonic vibration unit rotating means for rotating the ultrasonic vibration unit located at the tip of the catheter body with the longitudinal axis of the catheter body as a rotation axis.

Further, in the ultrasonic catheter for renal nerves of the present invention, the capacitance type ultrasonic transducer array is fractionated into a plurality of blocks called channels for each region in which a plurality of adjacent ultrasonic vibration elements operate in synchronization with each other. These blocks have a two-dimensional array in which the vibrating elements of the vibrating surface are arranged along two axes orthogonal to each other.
The control means includes a convergence point variable mechanism that adjusts the oscillation timing of each of the vibrating elements to adjust the focusing point of ultrasonic waves.

Furthermore, in the ultrasonic catheter for renal nerves of the present invention, the control means has an ablation mode in which ultrasonic waves are oscillated from the capacitance type ultrasonic transducer array, and a vascular cross section in the capacitance type ultrasonic transducer array. It is characterized by including an echo mode in which transmission and reception of ultrasonic waves are alternately repeated in order to compose an ultrasonic image of the above.

Further, the ultrasonic catheter for renal nerves of the present invention is a catheter characterized in that the control means includes a display device for displaying information obtained by the echo mode as an image image.

Further, the ultrasonic catheter for renal nerves of the present invention is characterized in that the ultrasonic vibration unit is housed in a cylindrical storage container, and the inside of the storage container is filled with a liquid for acoustic impedance matching. And.

In the ultrasonic catheter for renal nerves of the present invention, a plurality of deploying wires extending in the axial direction of the catheter body are arranged around the ultrasonic vibration unit at the tip of the catheter body, and each wire is attached to the catheter body. With these wires deployed in the radial direction and in contact with the inner wall of the renal artery, each of the wires rotates the ultrasonic vibration unit at the center of the renal artery with the axis of the catheter body as the axis of rotation. A balloon that can be freely held or that can be deployed in the radial direction of the catheter body is arranged around the ultrasonic vibration unit at the tip of the catheter body, and the balloon is deployed so that the outer circumference of the balloon is a renal artery. The balloon is characterized in that the ultrasonic vibration unit is rotatably held in the central portion of the renal artery with the axis of the catheter body as the axis of rotation in a state of being in contact with the inner wall of the catheter.

On the other hand, the ultrasonic catheter for renal nerves of the present invention is characterized by not having a water cooling system for the ultrasonic vibration unit.

According to the ultrasonic catheter for renal nerves of the present invention, since the ultrasonic vibration unit located at the tip of the catheter body is small, it is possible to reach the inside of a blood vessel smaller than the conventional product, and it is possible to reach a part other than the heating target site. It is possible to heat and cauterize only the target site such as the renal nerve more efficiently than the conventional product without giving extra heat that causes blood vessel stenosis or the like.

Further, among the ultrasonic catheters for renal nerves of the present invention, the ultrasonic vibration unit rotation in which the ultrasonic vibration unit located at the tip of the catheter body is rotated about the longitudinal axis of the catheter body as a rotation axis. In those including means, the ultrasonic irradiation surface of the ultrasonic vibration unit can be freely set in a certain direction of the irradiation target, so that the target nerve around the renal artery is distributed with respect to the portion. It becomes possible to irradiate ultrasonic waves in a concentrated manner.

Further, among the ultrasonic catheters for renal nerves of the present invention, in particular, the capacitance type ultrasonic transducer array has a two-dimensional array in which the vibrating elements of the vibrating surface are arranged along two axes orthogonal to each other. A catheter having a convergence point variable mechanism in which the control means adjusts the oscillation timing of each vibrating element to adjust the focusing point of ultrasonic waves is relatively easy to irradiate without using an acoustic lens or the like. While the convergence point of the sound wave can be adjusted, the focusing distance can be adjusted in a narrow range by emitting a highly directional ultrasonic beam by electronically focusing the ultrasonic wave having a high frequency. Further, the array configuration shortens the depth of field of the ultrasonic beam, so that ultrasonic focusing in a narrower range can be performed with respect to the portion where the renal nerves around the renal artery are distributed. It will be possible.

Further, among the ultrasonic catheters for renal nerves of the present invention, the control means has an ablation mode in which ultrasonic waves are oscillated from the capacitance type ultrasonic transducer array and a blood vessel in the capacitance type ultrasonic transducer array. Those equipped with an echo mode that alternately repeats transmission and reception of ultrasonic waves for constructing an ultrasonic image of a cross section can be used by alternately switching between these echo modes and ablation modes. It is possible to effectively irradiate the target site with ultrasonic waves while recognizing the position of the irradiation target such as a nerve.

Among the ultrasonic catheters for renal nerves, those in which the control means includes a display device for displaying the information obtained by the echo mode as an image image can determine the distribution of the renal nerves and the distance to the renal nerves. , It will be easier to grasp visually.

Further, among the ultrasonic catheters for renal nerves of the present invention, the ultrasonic vibration unit is housed in an ultrasonic permeable cylindrical storage container, and a liquid for acoustic impedance matching is contained inside the storage container. In the filled one, the oscillated ultrasonic waves do not return due to reflection or the like, and the vibration (heat) of the ultrasonic waves can be efficiently transmitted to the renal nerve.

Further, among the ultrasonic catheters for renal nerves of the present invention, a plurality of deployment wires extending in the axial direction of the catheter body are arranged around the ultrasonic vibration unit at the tip of the catheter body, and each wire is catheterized. In a state where these wires are deployed in the radial direction of the main body and these wires are in contact with the inner wall of the renal artery, each of the wires has the ultrasonic vibration unit and the axis of the catheter main body at the center of the renal artery as a rotation axis. Those having a rotatably holding structure can position the ultrasonic vibration unit at an appropriate position in the blood vessel without stopping the blood flow in the renal artery. Therefore, efficient ultrasonic irradiation to the renal nerve becomes possible.

Further, a state in which a balloon that can be deployed in the radial direction of the catheter body is arranged around the ultrasonic vibration unit at the tip of the catheter body, the balloon is deployed, and the outer periphery of the balloon is in contact with the inner wall of the renal artery. The balloon also includes the ultrasonic catheter for renal nerves of the present invention, which holds the ultrasonic vibration unit rotatably in the central portion of the renal artery with the axis of the catheter body as the rotation axis. The ultrasonic vibration unit can be positioned in an appropriate position. Therefore, similar to a catheter having a wire, efficient ultrasonic irradiation to the renal nerve becomes possible.

On the other hand, among the ultrasonic catheters for renal nerves of the present invention, in particular, the catheter without the water cooling system for the ultrasonic vibration unit has a structure as compared with the conventional product having a cooling unit for cooling the cauterizing means at the tip. It is simple and can be miniaturized, so that the ultrasonic vibration unit can reach into a small blood vessel and perform more efficient cauterization in the immediate vicinity of the renal nerve.

It is a schematic block diagram of the ultrasonic catheter for renal nerves of embodiment of this invention. (A) is an enlarged view of the tip portion of the ultrasonic catheter for renal nerve of the present embodiment, (b) is a perspective view of the ultrasonic vibration unit, and (c) is an end view of the ultrasonic vibration unit. (A) is a cross-sectional view of a single cell of the ultrasonic vibrator, and (b) is a plan view of a channel which is an aggregate of these cells. It is (a) perspective view and (b) sectional view explaining the structure of an ultrasonic transducer array. It is a schematic block diagram of the tip part of the ultrasonic catheter for renal nerves provided with a wire. It is a schematic block diagram of the tip part of the ultrasonic catheter for renal nerves provided with a balloon. It is a figure explaining the operation of (a) ablation mode and (b) echo mode in the ultrasonic catheter for renal nerve of this embodiment, and (c) is a figure explaining switching between ablation mode and echo mode. It is a principle diagram which shows the outline of the ultrasonic beam oscillated from the ultrasonic oscillator (CMUT).

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a schematic configuration diagram of an ultrasonic catheter for renal nerves according to the present embodiment, and FIG. 2 is an enlarged view of the tip (distal side) of the ultrasonic catheter for renal nerves.

The ultrasonic catheter 10 for renal nerve shown in this example exists from the inside of a blood vessel (renal artery RA or abdominal aortic artery AA) connected to the kidney and around the blood vessel (outside the blood vessel wall) as a treatment for specific hypertension. It is a catheter for renal nerve ablation that irradiates focused ultrasonic waves to heat and cauterizes the renal nerve (sympathetic renal nerve) RN, and is a catheter unit 2 composed of a catheter body 21 and an operation unit 22, and a catheter body. It is composed of an ultrasonic vibration unit 1 arranged at the distal end of 21 and a control means (ultrasonic control system 3) for controlling the ultrasonic vibration unit 1.

The catheter body 21 has a core-sheath structure including an elongated tubular outer cylinder (sheath 23) and a wire shaft (shaft 24) inserted inside (inner diameter) thereof. The sheath 23 is made of, for example, a resin tube of polyolefin-based, polyurethane-based, polyacetal-based, polyimide-based, fluorine-based, etc., a metal tube of stainless steel, a superelastic metal tube of NiTi-based alloy, or resin and stainless steel. A composite tube or the like in which a wire is coil-wound or blade-wound is used. Polyolefin-based, polyurethane-based, and fluorine-based resins having excellent ultrasonic wave permeability are preferably used for the tip portion (distal portion) that transmits and receives ultrasonic waves.

A cylindrical transducer housing 25 as shown in FIG. 2A was formed at the distal end of the sheath 23, and was connected to the tip of the shaft 24 in the transducer housing 25. , An ultrasonic vibration unit 1 [FIG. 2 (b)] including a micromechanical capacitive ultrasonic transducer array (hereinafter referred to as a CMUT array) is provided.

The transducer housing 25 has a hollow cylindrical shape made of a resin having excellent ultrasonic permeability, such as polyolefin-based, polyurethane-based, and fluorine-based, and as shown in FIG. 2C, its inner diameter is also cylindrical. The diameter is slightly larger than the outer diameter of the ultrasonic vibration unit 1. Therefore, the ultrasonic vibration unit 1 can freely rotate in the transducer housing 25 coaxially with the housing.

The operation unit 22 of the catheter unit 2 includes means (ultrasonic vibration unit rotating means) for controlling the rotation of the ultrasonic vibration unit 1 attached to the tip thereof and the deployment / contraction of the wire described later. .. The ultrasonic vibration unit rotating means may include a mechanism for adjusting the rotation direction and the rotation angle (phase angle).

Further, in the slight gap (circumferential gap) formed between the inner diameter of the transducer housing 25 and the outer diameter of the ultrasonic vibration unit 1, a "liquid" (liquid) for matching the acoustic impedance between them is formed. Hereinafter, a liquid for acoustic impedance matching) is enclosed.

Further, in the final form of the ultrasonic catheter for renal nerve, the position of the ultrasonic vibration unit 1 as shown in FIGS. 5 and 6 described later is held in the blood vessel on the outer diameter side of the transducer housing 25. A wire 26, a balloon 27, and the like for fixing are arranged. A description of these wires, balloons, etc. will be described later.

The ultrasonic vibration unit 1 fixed to the tip of the shaft 24 will be described in detail. As shown in the top view of FIG. 2 (b) and the end view of FIG. 2 (c), the ultrasonic vibration unit 1 has an outer diameter. Is a cylindrical shape approximately equal to the shaft 24, and by cutting off approximately two-thirds of the arc in the axial direction, the fixed portion 1a (notch) of the ultrasonic transducer (CMUT array 11) having a flat upper surface is formed. ) Is formed.

As shown in FIG. 3, the CMUT array 11 has tens to hundreds of individual cells [FIG. 3 (a)] arranged together as shown in an enlarged view of the array surface of FIG. 3 (b). Then, one fraction [block unit, hereinafter referred to as “channel”] of the array surface is formed as shown in FIG. 2 (b) or FIG. 4 (a).

Each cell forming a channel is a so-called micromechanical electromechanical device (Micro Electro Mechanical System: hereinafter referred to as MEMS), and vibrates opposite to the substrate 12 with a recess 12a (cavity) provided in the substrate 12 interposed therebetween. The film 14, the first electrode (film side electrode 15) arranged on the vibrating membrane 14, and the second electrode (board side) provided on the bottom surface of the recess 12a of the substrate 12 and facing the film side electrode 15. The electrode 13) and the like are the basic configurations. The cavity between the substrate 12 and the vibrating membrane 14 is evacuated, and a voltage is applied between the electrodes 13 and 15 so that the vibrating membrane 14 vibrates up and down.

The cavity (recessed portion 12a) of the substrate 12 is formed by patterning on one surface side of the substrate, and has a substantially circular opening shape. The recess 12a has a depth of about 0.1 to 5.0 μm with respect to the outer edge of the recess.

The substrate-side electrode 13 formed on the bottom surface of the recess 12a is formed in a circular shape having the same shape as the membrane-side electrode 15 [see FIG. 3 (b)] on the vibrating membrane 14, and is formed as shown in FIG. 3 (a). , Is connected to one pole side of the DC power supply DC and the AC power supply AC via the controller 16.

The vibrating film 14 is a film-like body laminated by vapor deposition, has a thickness of about 0.1 to 100 μm, and has flexibility. Further, as shown in FIG. 3A, the vibrating film 14 has a peripheral portion that is detached from the cavity fixed to the outer edge portion (upper surface of the substrate) of the recess 12a, and a central portion that is not fixed is the bottom surface of the recess 12a. It is a vibrating region that vibrates in the direction of approaching and separating from each other.

The membrane-side electrode 15 on the vibrating membrane 14 is provided in a similar circular shape at a position facing (facing) the substrate-side electrode 13 formed on the bottom surface of the recess 12a, and is provided on the substrate-side electrode 13. Correspondingly, it is connected to the other electrode side of the DC power supply DC and the AC power supply AC via the controller 16.

It should be noted that each ultrasonic oscillator cell is not formed individually, but is processed (formed) collectively in units of one channel [see FIG. 2 (b) or FIG. 4 (a)]. As shown in FIG. 3B, adjacent cells in the channel are in the same phase state in which the electrodes are electrically connected in parallel. Therefore, all the ultrasonic oscillator cells in the one channel operate in the same phase by one control signal at the time of transmission and reception.

Next, the CMUT as an array (ultrasonic array oscillator) in the present embodiment has the ultrasonic vibration described above as shown in the perspective view of FIG. 4 (a) and the cross-sectional view of FIG. 4 (b). The channel, which is an aggregate of child cells, has a two-dimensional array, and each ultrasonic oscillator has two axes orthogonal to each other [the shaft 24 and the X-axis in the longitudinal direction of the array, and the Y-axis in the lateral (width) direction of the array. ] It is characterized in that it is arranged along the line.

That is, the three-dimensional structure of the ultrasonic vibration unit 1 (CMUT array) shown in FIG. 2B is, for example, as shown in FIG. 4, the above-mentioned CMUT array 11 and an integrated circuit (base) laminated on the lower side thereof. It is composed of 17 and a unit substrate 18 that supports them. As shown in FIG. 4B, through electrodes (via electrodes) 19 that penetrate the substrate (base) in the thickness direction are provided at the edges of each substrate (base), and between the through electrodes 19 , Connected (laminated) by flip-chip bonding via the conductive bump 19A.

The integrated circuit 17 on the lower side (the back side of the element surface) of the CMUT array 11 is provided with circuits such as an amplifier, a driver, and a switch for transmitting and receiving ultrasonic waves. In the case of reception (echo mode), this integrated circuit is provided. Electrical signals and data from each channel of the array are transmitted to the unit substrate 18 via 17, and an ultrasonic wave including a display device is transmitted through a circuit 18a of the unit substrate 18 and wiring in the catheter unit 2 (sheath 23). It is transmitted to the control system 3 (see FIG. 1). On the contrary, in the case of transmission (ablation mode), the signal or the like transmitted from the ultrasonic control system 3 is transmitted to the unit substrate 18 through the wiring or the like in the catheter unit 2 (sheath 23), and has the amplifier, the driver, or the like. Ultrasonic vibration is oscillated through the integrated circuit 17.

Since the CMUT has a thin vibrating film 14 and vibrates softly, the original acoustic impedance is close to the liquid (blood, body fluid, etc.) around the transducer housing 25, and the ultrasonic vibration unit 1 is on the outside. A liquid for acoustic impedance matching is sealed between the transducer housing 25 and the transducer housing 25. Therefore, the ultrasonic vibration unit 1 of the present embodiment transmits ultrasonic waves to the outside with high efficiency without disposing an impedance matching layer or the like around the ultrasonic vibration unit 1 as in the case of a transducer using a piezoelectric element. can do.

In addition, since the ultrasonic waves oscillated from the CMUT are highly directional focused ultrasonic waves (Focused Ultrasound), they emit unfocused Ultrasound in combination with the high efficiency of the above-mentioned transmission. Focusing points can be formed in a narrow range with a smaller array volume than a transducer using a piezoelectric element. Moreover, since the ultrasonic vibration unit 1 (CMUT) of the present embodiment generates less heat from the element itself, it is used to cool the blood vessel wall contact portion like a conventional ablation catheter using an RF element or a piezoelectric element. No mechanism or piping is required.

With the above configuration, the ultrasonic catheter 10 for renal nerves of the present embodiment can make the ablation unit (ultrasonic vibration unit 1) at the tip of the catheter smaller than that of the conventional ablation catheter. Incidentally, in the case of the ultrasonic vibration unit 1 [FIG. 2 (a)] in the present embodiment, the unit size of the shaft 24 and the array longitudinal direction (X-axis direction) is about 3 mm or less, and the array short (width) direction (Y). The unit width (in the axial direction) is about 0.5 to 2.0 mm, and the diameter of the cylindrical unit is within about 1.5 mmφ. Due to this miniaturization, the ablation catheter 10 of the present embodiment can reach into a smaller blood vessel (renal artery RA) than the conventional ablation catheter.

As the acoustic impedance matching liquid enclosed between the ultrasonic vibration unit 1 and the transducer housing 25, a physiological saline solution, a mixed solution of physiological saline solution and a contrast medium, or the like is used.

Further, the renal nerve catheter 10 of the present embodiment is shown in FIGS. 5 and 6 so that its position does not shift when it reaches the target treatment site (inside a small blood vessel) and irradiates ultrasonic waves. A wire 26, a balloon 27, and the like for holding the position of the ultrasonic vibration unit 1 in the blood vessel are arranged.

As the material constituting the wire 26, metals such as titanium alloys, pure titanium, stainless steel (SUS) and CoCr alloys, and resins such as polyimide, polyamide, polyether ether ketone and PDMS (Polydimethylsiloxane) can be used. However, a wire made of a titanium alloy is preferably used because it does not relatively affect the irradiation of ultrasonic waves and has an appropriate flexibility to withstand repeated unfolding and folding.

The materials constituting the balloon 27 include resin-based materials having biocompatibility and appropriate elasticity, for example, resins such as polyethylene, polypropylene, polyurethane, polyester, polytetrafluoroethylene, polyamide, polydimethylsiloxane, and latex, and A combination of these materials can be used. Among them, a balloon made of polyurethane (polyurethane elastomer) is preferably used because it does not affect the irradiation of ultrasonic waves and has an appropriate flexibility to withstand repeated unfolding and folding.

Then, when irradiating (causing) ultrasonic waves, as shown in FIGS. 5 (wire) and 6 (balloon), a wire or the like is developed around the transducer housing 25 (ultrasonic vibration unit 1), and the CMUT array is used. Ultrasound irradiation is performed while maintaining the distance from the surface of No. 11 to the inner wall of the renal artery and the renal nerve existing on the outside thereof as constant as possible.

For the deployment (expansion) of the balloon 27, a liquid equivalent to the acoustic impedance matching liquid (usually, a mixed solution of physiological saline and a contrast medium) is used. The liquid in the balloon 27 may or may not circulate for cooling the inner wall of the blood vessel. Further, the outer peripheral surface of the balloon 27 is formed with irregularities for creating a gap between the balloon 27 and the blood vessel wall so as not to stop the blood flow of the renal artery.

Further, the surface (outer peripheral surface) of the sheath 23 of the catheter unit 2 can be made substantially lubricable and hydrophilic by the resin as it is or by surface modification treatment or the like. Further, the sheath 23 may be configured such that not only the shaft 24 but also a plurality of wire shafts (guide lumens, drive lumens, etc.) called lumens are inserted inside the shaft 24.

Further, the shaft 24 of the catheter unit 2 is made of a highly elastic metal such as a Ni—Ti alloy or a synthetic resin. When a balloon is arranged at the tip of the catheter, an infusion path for supplying a liquid to the balloon 27 is formed between the shaft 24 and the sheath 23. Further, a plurality of signal lines (signal wires) for controlling the ultrasonic vibration unit 1 at the tip portion may be inserted inside the sheath 23.

The outer diameter of the catheter body 21 (outer diameter of the sheath 23) is usually 0.3 from the viewpoint of flexibility, torque transmission, flexibility, and reduction in diameter. It is set to ~ 3 mm, preferably 0.5 to 2.0 mm.

Next, the operation (cauterization) of the ultrasonic catheter 10 for renal nerves having the above configuration will be described.
FIG. 7 (a) is a diagram illustrating a transmission operation of the ultrasonic catheter for renal nerve in the ablation mode of the present embodiment, and FIG. 7 (b) is a diagram showing reception in the echo (imaging) mode of the ultrasonic catheter for renal nerve. It is a figure explaining operation, and FIG. 7C is a figure explaining switching between an ablation mode and an echo mode. In the embodiment described later, ultrasonic vibration at the tip of the ultrasonic catheter 10 for renal nerves is performed by using an X-ray fluoroscopy method or another echo device that can obtain images of organs, blood vessels, etc. from outside the abdominal cavity. The state after the unit 1 reaches the vicinity of the renal artery (RA) to be ablated (the state shown in FIG. 1) will be described.

The ultrasonic catheter 10 for renal nerves to be used includes an ultrasonic control system 3 for controlling an ultrasonic vibration unit 1 located at the tip of the catheter body 21 and an ultrasonic vibration unit 1 on the longitudinal axis of the catheter body 21. The ultrasonic control system 3 has an ablation mode in which ultrasonic waves are transmitted from an ultrasonic vibrator (channel of a CMUT array). It is characterized by including an echo mode in which ultrasonic waves are alternately transmitted and received by an ultrasonic vibrator.

In the operation of the ultrasonic catheter 10 for renal nerves using these, it is first confirmed that one site of the ultrasonic vibration unit at the tip of the catheter has reached the vicinity of the renal artery RA, and then the echo shown in FIG. 7 (b). Using the mode, the vascular cross section of the surrounding renal artery RA is imaged to confirm the distribution of renal nerve RN. This is done not to recognize each renal nerve RN and adjust the focusing point to the renal nerve RN, but to grasp the distribution region of the renal nerve RN mainly distributed around the outer membrane of the blood vessel.

Then, the ultrasonic vibration unit 1 is advanced to the vicinity of the renal nerve RN whose distribution has been confirmed, the wire 26 and the like shown in FIG. 5 are expanded, and the position of the ultrasonic vibration unit 1 is temporarily fixed. At that position, the convergence point (focusing distance) of the ultrasonic wave at the time of subsequent irradiation can be adjusted by performing imaging using the same echo mode as described above.

The focusing distance of ultrasonic waves during ablation can be adjusted in the ablation mode described above. That is, in the ablation mode shown in FIG. 7 (a), the transmission (oscillation) timing of the ultrasonic vibrator on the ultrasonic vibration unit 1 (CMUT array) is controlled for each channel as shown in FIG. 4 (a). By doing so, the focusing distance and direction of ultrasonic waves are adjusted.

More specifically, the CMUT array uses each channel when focusing ultrasonic waves in one direction (X-axis direction or Y-axis direction) toward the center of the element (channel) row, as shown in FIG. 7A, for example. As shown in the figure, oscillate sequentially from the channels at both ends with a slight time difference. When the drive frequency of the element (channel) is controlled in this way, the ultrasonic waves oscillated earlier from the channels near both ends gather toward the center oscillated with a delay, and the ultrasonic vibration wave is generated at the focal point F shown in the figure. Since they overlap, the amplitude at the focal point F (that is, the heat generated by ultrasonic waves) becomes maximum. Thereby, the point (focus) of heat generation due to ultrasonic vibration can be freely controlled.

Since the CMUT array 11 of the present embodiment is arranged in the biaxial (two-dimensional) directions in the X-axis direction and the Y-axis direction as shown in FIG. 4A, the heat generated by the ultrasonic vibration described above is generated. The position of the point (focus F) can be controlled on a plane in both axial directions. Of course, the distance (Z-axis direction (not shown)) of the heat generation point (focus F) from the array can also be adjusted.

Since the conventional piezoelectric element cannot have a high frequency array configuration, the focusing range is wide and the focusing range cannot be adjusted for a short distance. On the other hand, in the CMUT array of the present embodiment, since the element arrangement is two-dimensional and a high frequency array element configuration is possible, it is possible to form a focusing point in a narrow range using sharp directivity, and the focusing distance can be increased. It can be adjusted freely. Moreover, the ultrasonic array having a two-dimensional array can detect the distribution position of the renal nerve and electronically adjust the focusing range. As a result, the CMUT array of the present embodiment enables ablation treatment in a narrow range.

To explain this in more detail, the ultrasonic beam oscillated from the CMUT array (channel sequence) of the ultrasonic vibration unit 1 can be represented as shown in the principle diagram of FIG. In this figure, "D" indicates the length (diameter) of the array (channel), "Fgeo" indicates the focusing distance, and "DOF" indicates the depth of field.

In a small ultrasonic oscillator as in the present embodiment, the focusing of the ultrasonic beam is performed at a frequency having a depth of field (DOF) of several MHz, as represented by FIG. 8 and the following equation (1). , It becomes as long as several mm with respect to the focusing distance of several mm, and it is difficult to adjust the focusing distance and the depth of field in that band.

上記式（１）において、λは超音波の波長である。

In the above equation (1), λ is the wavelength of ultrasonic waves.

That is, in order to maintain a depth of field of about 2 to 3 mm at a focusing distance of about several mm, an array element having a high frequency of 15 MHz or more is required. However, in the conventional piezoelectric ceramics (PZT), the oscillation frequency is limited to about 10 MHz.

On the other hand, in the CMUT array of the present embodiment, it has become possible to fabricate a high frequency array element having an oscillation frequency of 15 MHz or more by using an ultra-small electromechanical device (MEMS) technology. Further, the ultrasonic vibration unit 1 of the present embodiment equipped with this can secure a depth of field of 2 to 3 mm or less while having a focusing distance of about several mm.

Next, in the operation of the ultrasonic catheter 10 for the renal nerve of the present embodiment, the distribution range of the renal nerve RN is obtained by repeating the ultrasonic ablation (ablation mode) and the imaging (echo mode) at a fixed timing. The focus F can be adjusted while always grasping. Usually, the ultrasonic control system 3 is configured so that the ablation mode and the imaging (echo mode) can be alternately switched once or more per second.

Specifically, the ablation mode [FIG. 7 (a)] and the echo mode [FIG. 7 (b)] are repeated at the following timings to adjust the ultrasonic focusing position (focus F).

For example, in the embodiment of FIG. 7 (c), the renal nerve ultrasonic catheter 10 performs an ablation mode (ultrasonic transmission) for 0.02 seconds and an echo mode (ultrasonic transmission / reception) for 0.01 seconds. This is set as one cycle (one turn), and this is repeated multiple times. That is, in the ablation mode (ultrasonic transmission), for example, an ultrasonic pulse (Ping) having a frequency of 20 MHz is oscillated for 0.02 seconds.

Further, in the echo mode (ultrasonic transmission / reception), for example, transmission of an ultrasonic pulse (Ping) for 0.001 seconds and reception of an echo for 0.001 seconds are set as one cycle, and this is repeated for about 5 cycles to repeat the renal artery. Imaging the cross section of the RA blood vessel wall and its vicinity.

In this way, in the operation of the ablation mode, only the focused ultrasonic waves are transmitted, and in the operation of the echo mode, the transmission / reception operation for imaging is performed, so that the focus of cauterization is always grasped while grasping the distribution of the renal nerve RN. F can be adjusted. The ultrasonic catheter 10 for renal nerves of the present embodiment can also perform only ablation without imaging.

In addition, the ultrasonic catheter 10 for renal nerves can also see changes in temperature at a target site (around the renal nerve RN) and changes in cell (nerve) hardness by echo mode (imaging). Specifically, when the hardness of cells is changed by ultrasonic irradiation, the hardness of cells can be known by observing that the speed of sound of ultrasonic waves passing therethrough changes linearly. Further, by measuring the change in the sound velocity of the ultrasonic wave in the echo mode, the change in the hardness and the temperature of the cell can be evaluated. As a result, the ultrasonic catheter 10 for renal nerves of the present embodiment can be operated while confirming the completion (end point) of cauterization.

As a result of the above configuration and operation, the ultrasonic catheter 10 for the renal nerve of the present embodiment switches to the ablation mode at that position while recognizing the distribution of the irradiation target such as the renal nerve by the echo mode, and is effective for the target site. It can irradiate ultrasonic waves. In addition, this makes it possible to suppress the occurrence of damage (burns, etc.) on the inner wall of the blood vessel, which causes stenosis of the blood vessel.

1 Ultrasonic vibration unit 2 Catheter unit 3 Control means 10 Catheter 11 CMUT array 12 Substrate 13 Substrate side electrode 14 Vibrating membrane 15 Membrane side electrode 16 Controller 17 Integrated circuit 18 Unit substrate 19 Penetration electrode 19A Conductive bump 21 Catheter body 22 Operation unit 23 Sheath 24 Shaft 25 Transducer Housing 26 Wire 27 Balloon AA Abdominal Aorta RA Renal Artery RN Renal Nerve

Claims (13)

Catheter body and
An ultrasonic vibration unit arranged at the tip of the catheter body is provided.
The ultrasonic vibration unit includes a unit base arranged on the catheter body, an integrated circuit stacked in the thickness direction of the unit base, and an ultrasonic transducer array stacked in the thickness direction of the integrated circuit. ,
The ultrasonic transducer array and the integrated circuit each have a through electrode penetrating in the thickness direction.
An ultrasonic catheter in which the ultrasonic transducer array, the integrated circuit, and the unit base are electrically connected via the through electrode. A control means for controlling the ultrasonic vibration unit is provided.
The ultrasonic catheter according to claim 1, wherein the ultrasonic transducer array is a capacitance type ultrasonic transducer array including a plurality of micromechanical ultrasonic transducer cells. The capacitive ultrasonic transducer array has a two-dimensional array in which each vibrating element on the vibrating surface is arranged along two axes orthogonal to each other.
The ultrasonic catheter according to claim 2, wherein the control means includes a convergence point variable mechanism that adjusts the oscillation timing of each vibrating element to adjust the focusing point of ultrasonic waves. The integrated circuit has a switch circuit that controls the frequency emitted by the capacitive ultrasonic transducer array.
The control means constitutes an ablation mode in which ultrasonic waves are oscillated from the capacitance type ultrasonic transducer array via the switch circuit, and an ultrasonic image of a blood vessel cross section by the capacitance type ultrasonic transducer array. The ultrasonic catheter according to claim 2 or 3, wherein the echo mode for alternately repeating transmission and reception of ultrasonic waves is switched. The ultrasonic catheter according to claim 4, wherein the control means includes a display device that displays information obtained by the echo mode as an image. The ultrasonic catheter according to claim 4 or 5, wherein the capacitance type ultrasonic transducer array has a plurality of channels in which a plurality of adjacent ultrasonic transducer cells are connected in parallel. The ultrasonic catheter according to claim 6, wherein the convergence point variable mechanism adjusts the oscillation timing of the channel to adjust the focusing point of the ultrasonic wave. The ultrasonic catheter according to claim 6 or 7, wherein the control means switches between the ablation mode and the echo mode in each of the channels. An operation unit provided at the base portion on the proximal side of the catheter body is provided.
The catheter body has a core sheath structure including a sheath serving as an outer cylinder and a shaft rotatably inserted inside the sheath.
The operation unit includes an ultrasonic vibration unit rotating means for rotating the ultrasonic vibration unit located at the tip of the catheter body with the longitudinal axis of the catheter body as a rotation axis. Item 8. The ultrasonic catheter according to Item 1. A plurality of deploying wires extending in the axial direction of the catheter body are arranged around the ultrasonic vibration unit.
With each wire deployed in the radial direction of the catheter body and these wires abutting on the inner wall of the renal artery, each wire places the ultrasonic vibration unit at the center of the renal artery and the axis of the catheter body. The ultrasonic catheter according to claim 1 to 9, wherein the ultrasonic catheter is rotatably held around the axis of rotation. A balloon that can be deployed in the radial direction of the catheter body is arranged around the ultrasonic vibration unit.
In a state where the balloon is deployed and the outer circumference of the balloon is in contact with the inner wall of the renal artery, the balloon rotates the ultrasonic vibration unit at the center of the renal artery with the axis of the catheter body as the rotation axis. The ultrasonic catheter according to any one of claims 1 to 9, wherein the ultrasonic catheter is freely held. The ultrasonic wave according to claims 1 to 11, wherein the ultrasonic vibration unit is housed in a cylindrical storage container, and the inside of the storage container is filled with a liquid for acoustic impedance matching. catheter. The ultrasonic catheter according to claim 1, wherein the ultrasonic catheter does not have a water cooling system for the ultrasonic vibration unit.

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