DE20022925U1 - Body stone removal device using an intracorporeal lithotripter - Google Patents

Description

European Patent Attorneys European Trademark Attorneys

MÜLLER, SCHUPFNER & GAUGER

PATENT ATTORNEYS Mandataires en brevets europeens Conseils europeens en marques

MÜLLER, SCHUPFNER & GAUGER · PO Box 10 11 61 ■ D-80085 Munich

Attorney file: EMS-4527 A

Dr.-Ing. Robert Poschenrieder (1931 -1972)

Dipl.-Ing. Hans-Jürgen Müller Dipl.-Chem. Dr. Gerhard Schupfner* Dipl.-Ing. Hans-Peter Gauger Dipl.-Chem. Dr. Georg Schupfner* Dipl.-Ing. F. Peter Müller

Dr.-Ing. Franz-Josef Fuchs

PO Box 10 11 61 Maximilianstrasse 6 D-80085 MUNICH

Telephone: +49-89-21 99 12-0 Fax: +49-89-21 99 12-21

5 April 2002

FERTON HOLDING S.A., CH-2800 DELEMONT (CH) Device for removing body stones using a

intracorporeal lithotripter

Office Buchholz: PO Box 17 53 0-21236BUdIhOlZLd. N.

Stadtsparkasse München: 29-167 350 (bank code 701 500 00) Postbank München: 276 688-808 (bank code 700 100 80) VAT: DE 130 316 103

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The invention relates to a device for removing body stones using an intracorporeal lithotripter according to the preamble of claim 1.

In order to remove body stones from body cavities, if the stone size is larger than that which is still sufficient for natural passage, it is usually necessary to first crush the body stones. The crushing is carried out into small particles that can be passed spontaneously or flushed out of the body directly. The crushing of the body stones is carried out by mechanical compressive and tensile stresses which are exerted on the body stones during intracorporeal lithotripsy using the distal end of a metal probe that serves as a waveguide. Such stresses lead to fragments being broken off from the surface of a stone and ultimately cause it to shatter. For this type of stone crushing, there is generally the problem of suitable energy transfer with particular attention to avoiding side effects on the biological tissue, which should therefore not serve as an abutment for the stone crushing.

For carrying out intracorporeal lithotripsy, a device is known from EP 0 421 285 B1, in which a metal probe is excited to longitudinal vibrations by an electrically controlled ultrasonic transducer, so that the distal end of the probe inserted into the working channel of an endoscope can cause the fragmentation of a body stone. The ultrasonic transducer is designed with two piezoceramic disks that are clamped between a reflector and a horn. The two disks are controlled for periodic vibration excitation of the metal probe by a circuit arrangement that consists of a voltage-controlled oscillator, the output signal of which is fed via an output amplifier and a

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Output transformer to the two piezoceramic disks. The circuit arrangement also includes a phase comparator, which compares the phases of the output voltage and the output current of the output transformer and generates a control voltage to control the oscillator. With a device of this design, the body stones can usually be broken up into very fine fragments, whereby the fine fragments have a particle size that allows them to be sucked out without any problems through an axial cavity of the probe up to its proximal end, where a suction connection is brought into effect through the ultrasound transducer. The stone breaking up using such ultrasound lithotripters
However, it is relatively time-consuming, since the distal end of the tubular metal probe can only be used to process the stone in a way that protects the tissue very slowly at the usual ultrasonic frequencies of around 20 to 25 kHz and probe tip amplitudes of up to around 50 pm. Difficulties also arise with some harder body stones, which cannot be scraped off spontaneously at these ultrasonic frequencies and probe tip amplitudes, so that their processing either takes a very long time or is not possible at all.

EP 0 317 507 B1 discloses a lithotripter in which the proximal end of a metal probe is subjected to a pneumatically driven impact part in order to obtain a shock or pressure wave that runs through the metal probe to its distal end using the impact energy provided by this, which can then also have a mechanical effect on a body stone. Such shock wave lithotripters, which in other designs can also have an electrical drive for the impact part, generally result in a relatively simple device structure with very good fragmentation performance even on harder body stones. However, with these lithotripters,

The stone fragmentation process down to a particle size that can be extracted is still relatively time-consuming.

The invention is based on the object of designing a device of the type mentioned at the outset in such a way that a more flexible stone fragmentation can be carried out, taking into account the advantages and disadvantages of these known methods.

This object is achieved according to the invention with a device of the design specified by claim 1, which has an advantageous design option with the features of the further claims.

The device according to the invention, in which the ultrasonic transducer can expediently have the known design of a piezoelectric transducer with at least two piezoceramic disks with an arrangement between a reflector and a horn, is thus set up for optional operation in a first application mode with a periodic vibration excitation of the metal probe and in a second application mode with a pulse-shaped vibration excitation of the metal probe. In the case of periodic vibration excitation, the metal probe is caused by the connected circuit arrangement to form a standing wave essentially as in the previously known ultrasonic lithotripters, which results in a sinusoidal movement of the probe tip in the axial direction, so that the stone surface can be mechanically influenced with the probe tip to break up the stone. In the case of pulse-shaped vibration excitation of the metal probe, to whose preferably provided separate circuit arrangement it can be switched with a simple switch, the ultrasonic transducer is, on the other hand, controlled with a single voltage pulse to provide an output power.

which causes the two piezoceramic disks to suddenly expand, so that a pressure wave is generated in the metal probe connected to the horn, which generates a pressure pulse at the probe tip that is introduced into the body stone. Since such a pressure pulse results in a single load on the metal probe in a relatively small time window, a much higher power can be delivered with the pulse-shaped vibration excitation of the metal probe via the connection to the piezoelectric transducer than with the periodic vibration excitation, so that with this application mode of the device according to the invention for stone fragmentation, results can be achieved that are comparable to those with the known shock wave lithotripters.

An embodiment of the device according to the invention is shown schematically in the drawing and is described in more detail below.

The device according to the invention consists of an ultrasonic transducer which is designed as a piezoelectric transducer with two piezoceramic disks 1 and 2 with an arrangement between a reflector 3 and a horn 4. The arrangement of the ultrasonic transducer consisting of these components is held together by a hollow clamping screw 5 which axially passes through the two ceramic disks 1, 2 and the reflector 3 and is screwed to the horn 4 via a screw thread 6. On the other hand, a tubular metal probe 7 is screwed to the horn 4 at a screw attachment 8, so that the cavity of the clamping screw 5 continues axially in the cavity of the metal probe 7.

The arrangement of the individual components of the ultrasonic transducer, held together and clamped against each other by the clamping screw 5, is within a

Housing 9 is housed. Due to a two-part design of this housing with a dividing plane in the area of the horn 4, the clamping screw 5 also achieves an elastic tension against the housing 9, which is supported by elastic support means in the form of O-rings 10 and a sealing sleeve 11. An external suction connection 12 is connected to the hollow clamping screw 5, so that the stone fragments that accrue at the distal end of the metal probe 7 during stone fragmentation carried out with this device can be spontaneously sucked out via the hollow space of the metal probe 7 and the axially aligned hollow space of the clamping screw 5.

The two piezoceramic disks 1, 2 are connected to an electrical control system for generating vibrations that are transmitted to the metal probe 7. The electrical control system is designed with a first circuit arrangement 13 and a separate second circuit arrangement 14. The circuit arrangement 13 is intended for periodic vibration excitation of the metal probe and is essentially designed for this purpose with a voltage-controlled oscillator 15 that is connected to an impedance transformer 18 via a U/F converter 16 and a downstream amplifier 17. The impedance transformer 18 is fed back to the U/F converter 16 via a phase comparator 19, which compares the phases of the output voltage and the output current of the impedance transformer 18 and generates a control voltage for controlling the oscillator 15, so that an output signal suitable for the periodic oscillation excitation of the metal probe 7 is supplied to the two piezoceramic disks 1, 2 via the connection 20.

The piezoceramic disks 1, 2 are on the other hand connected to the second circuit arrangement 14, through which a pulse-shaped vibration excitation of the metal probe 7 is obtained. The circuit arrangement 14 consists of

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a voltage source 22 and a capacitor 23, which is charged by the voltage source 22 in a first switching position of a changeover switch 21. The capacitor 23 is, on the other hand, discharged when the changeover switch 21 is switched to a second switching position for a pulse-shaped vibration excitation of the metal probe, so that it is then the capacitor charge that is passed on once via the connection 20 to the two piezoceramic disks 1, 2. Because a significantly higher power can be delivered to the piezoelectric transducer for the pulse-shaped vibration excitation by the output signal of the circuit arrangement 14 than with the output signal of the circuit arrangement 13 which is decisive for the periodic vibration excitation, this higher power results in a sudden expansion of the two piezoceramic disks 1, 2, which leads to a one-time pressure wave generation in the metal probe 7 and thus to the emission of a pressure pulse at the distal end of the probe, which is then introduced directly into a body stone intended for fragmentation.

In order to obtain optimum results for the pulse-shaped vibration excitation of the metal probe, the horn 4 of the ultrasonic transducer and the metal probe 7 screwed to it should be made of a material with essentially the same acoustic impedance. Stainless steel and titanium are preferred materials. Furthermore, the horn 4 should be provided with an envelope surface that tapers in the axial direction to approximately the cross section of the screw attachment 8 of the metal probe 7 in the form of an exponential curve, although other geometries can also be considered for the envelope surface. The support of the ultrasonic transducer on the surrounding housing, achieved by the elastic means 10, 11, should be designed in such a way that optimum working results are obtained for both the periodic and the pulse-shaped vibration excitation of the metal probe. For the

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In order to switch between the periodic and the pulsed vibration excitation of the metal probe, a switching device additional to the changeover switch 21 can also be provided, which can be switched between separate connection connections of the ultrasonic transducer.

Claims (8)

1. Device for removing body stones with an intracorporeal lithotripter, consisting of: - a metal probe ( 7 ) serving as a waveguide which is inserted into the working channel of an endoscope for stone fragmentation by its distal end; - an electrically controlled ultrasonic transducer which excites the metal probe ( 7 ) to longitudinal vibrations, wherein - the ultrasonic transducer is formed with at least one piezoceramic disc ( 1 , 2 ) which are clamped against one another by an arrangement between a reflector ( 3 ) and a horn ( 4 ) carrying the metal probe ( 7 ) by a clamping screw ( 5 ) axially penetrating the arrangement, and - the electrical control of the ultrasonic transducer can be switched between a periodic vibration excitation and a pulse-shaped vibration excitation of the metal probe ( 7 ) for generating a pressure wave which leads to the emission of a single pressure pulse at the distal end of the metal probe. 2. Device according to claim 1, characterized in that two separate circuit arrangements ( 13 , 14 ) are provided for the pulse-shaped and the periodic vibration excitation of the metal probe ( 7 ), wherein - a first circuit arrangement ( 13 ) for controlling the periodic oscillation excitation of the metal probe ( 7 ) is formed with a voltage-controlled oscillator ( 15 ) which is connected to an impedance transformer ( 18 ) via a U/F converter ( 16 ) and a downstream amplifier ( 17 ), and with a phase comparator ( 19 ) which compares the phases of the output voltage and the output current of the impedance transformer ( 18 ) to generate a control voltage for controlling the oscillator ( 15 ), - a second circuit arrangement ( 14 ) for controlling the pulse-shaped vibration excitation of the metal probe ( 7 ) is formed with a voltage source ( 22 ) and with a capacitor ( 23 ) and can be switched via a changeover switch ( 21 ) into a connection ( 20 ) with the ultrasonic transducer. 3. Device according to claim 2, characterized in that the capacitor ( 23 ) of the second circuit arrangement ( 14 ) is charged by the voltage source ( 22 ) in a first switching position of the changeover switch ( 21 ) and can be switched to a second switching position for the connection ( 20 ) to the ultrasonic transducer. 4. Device according to one of claims 1 to 3, characterized in that the arrangement of the reflector ( 3 ), the at least one piezoceramic disk ( 1 , 2 ) and the horn ( 4 ) of the ultrasonic transducer carrying the metal probe ( 7 ), which arrangement is mutually clamped by the clamping screw ( 5 ), is supported against a surrounding housing by elastic support means ( 10 , 11 ). 5. Device according to one of claims 1 to 4, characterized in that the horn ( 4 ) of the ultrasonic transducer is provided with an envelope surface tapering in the axial direction approximately on the cross section of a screw attachment ( 8 ) of the metal probe ( 7 ) in the formation of an exponential curve. 6. Device according to one of claims 1 to 5, characterized in that the clamping screw 5 is hollow for the connection of an external suction connection ( 12 ) to a tubular metal probe ( 7 ) screwed to the horn ( 4 ) of the ultrasonic transducer and axially aligned with the cavity of the clamping screw ( 5 ). 7. Device according to one of claims 1 to 6, characterized in that the metal probe ( 7 ) and the horn ( 4 ) of the ultrasonic transducer consist of a material with a substantially equal acoustic impedance. 8. Device according to one of claims 1 to 7, characterized in that for switching between the periodic and the pulsed vibration excitation of the metal probe ( 7 ) a separate switching device is provided between separate connection connections ( 20 ) to the ultrasonic transducer.