EP0840571A1

EP0840571A1 - Device for the detection of concretions and cavitation bubbles

Info

Publication number: EP0840571A1
Application number: EP96927032A
Authority: EP
Inventors: Rainer Schmitt; Matthias Molitor
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 1995-07-21
Filing date: 1996-07-17
Publication date: 1998-05-13
Also published as: JPH10510456A; WO1997003610A1

Abstract

The invention concerns a device designed to detect concretions and/or cavitation bubbles which occur when, in particular, solid bodies are detached or disintegrated by the use of high-power ultrasonic radiation. The device includes a high-power ultrasound generator and a preferably ultrasonic imaging system. The aim of the invention is to further develop such a device so that it gives an improved image of concretions and/or cavitation bubbles. The invention proposes that an additional ultrasonic system with a Doppler converter (2) is provided, the Doppler converter being fitted in the region of the transmitter head (16) of the ultrasound generator system and/or the imaging system. The Doppler converter (2) is preferably disposed in a ring round the transmitter head (16).

Description

Device for the detection of calculus and cavitation bubbles

The invention relates to a device for the detection of concavities and / or cavitation bubbles, in particular for lithotripsy, according to the features specified in the preamble of claim 1.

From DE 40 12 760 AI an ultrasound Doppler method for determining the stone size from the rate of descent during biliary lithotripsy and also a device for performing this method is known. As is known, there is no shock wave apparatus or a power sound system, a transducer which has to be precisely aligned so that the concrement, in particular a gall stone, is in the focus of the shock wave apparatus. Depending on such an acoustic power system, an image system in the form of an ultrasound device is available according to DE 40 12 760 AI, and both systems are to be aligned with the area of the gallstone. Aiming with the power sound system in such a way that the normally largest stone is in focus requires a great deal of experience on the part of the surgeon, the alignment of the

ORIGINAL DOCUMENTS Imaging system represents an additional burden and requires a further not inconsiderable effort. The known ultrasound device of the image system can be designed to be Doppler-capable or, in another embodiment, there is an independent Doppler system with individual oscillators for the transmission and reception process for carrying out a Doppler measurement. Here, the particles or concretions whirled up in the body fluid as a result of a shock wave pulse are subjected to ultrasound of a certain frequency in their sinking phase. The particle speed is determined from the frequency shift of the reflected sound and the particle size is calculated. In the sinking phase, the particles are subjected to a sufficiently narrow frequency bandwidth by ultrasound, and the frequency shift of the reflected ultrasound resulting from the stone movement as a result of the Doppler effect is measured. The particle velocity is calculated from the frequency shift, the angle between the sound direction and the vertical also being taken into account where appropriate. Finally, the particle diameter is calculated on the condition that it is proportional to the square of the particle velocity under given conditions.

Furthermore, a device is known from US Pat. No. 4,932,414, which contains an acoustic power system for diagnosis and therapy combined with an image system. The image system must again be manually aligned to the focus of the performance sound system and the detected angular position is transferred to a computer by means of a position indicator. The outlay on equipment is not insignificant and the detection of the angular position requires additional computing and / or software effort.

During lithotripsy, the location of a stone within a kidney or gallbladder is of particular interest. Only a precise knowledge of this position allows the ultrasound focus of the power sound generator to be set more precisely, especially if it has only a narrow lobe within which the stone can be destroyed. The known devices and methods do not allow an overly precise localization. In the case of ultrasound and X-ray methods, it should also be noted that due to the non-linear sound propagation, the focus of the performance sound, the focus of the image and the imaging of an X-ray device to a distorted position tion can lead. For this reason, the success control plays an extremely important role in determining whether a stone has actually been hit by the performance sound.

Proceeding from this, the object of the invention is to further develop the device of the type mentioned in order to achieve an improved representation of concrements and / or cavitation bubbles. Reliable localization of the concretions or cavitation bubbles and a positioning of the acoustic power focus based thereon are to be achieved in a functionally reliable manner. Furthermore, it is to be ensured that there is a feedback between an operator and the device in such a way that incorrect positioning or misfires of the performance sound focus system are avoided.

This object is achieved in accordance with the characterizing features of patent claim 1.

The device according to the invention contains a further ultrasound system which has the same focus, in particular at least approximately as the performance sound system. This further ultrasound system is expediently arranged around the image sound migrator, which images the region of interest in a two-dimensional plane. The ultrasound waves are sent into the focus zone formed in this way, which lead to a Doppler signal shift when the stone is hit. According to the invention, this Doppler signal shift is resumed with the same arrangement and processed into yes / no hit information. This information is thus obtained via ultrasound Doppler and the transmission and reception electronics provided for Doppler signal processing consist of an SE arrangement which is implemented from several elements. Here, an element is used alternately as a transmitter and also as a receiver, so that CW ultrasound can be used. In a particularly expedient manner, the frequencies of the doubling system are selected such that they lie between the imaging frequencies of the imaging transducer system and the power sound frequencies of the therapeutic signal or the power sound system. The frequency becomes so that the localization, in particular of a stone, can be carried out simultaneously with the destruction, in particular of the stone, with the aid of the Doppler signals of the doubler in such a way that the lowest possible interference in the received Doppler signals occurs both through the power sound and through the ultrasound of the image system. If, for example, the power sound system is designed for a center frequency of 380 kHz and the image device, in particular B-image device, for an ultrasound with a center frequency of 3.5 MHz, the Doppler frequency, that is to say the transmit frequency of the Doppler converter, is in the range of 1 MHz specified. According to the invention, the Doppler frequency is specified in such a way that it lies in a range in which, on the one hand, the power sound field has a minimum and, on the other hand, separation from the image sound can take place. Furthermore, the Doppler converter is expediently focused in the working area of the high-performance sound system, in particular the lithotriptor. If the working range of the high-performance sound system, in particular the lithotriptor, is at a depth between 50 mm and 150 mm, the Doppler converter is focused in this range within the scope of the invention. In order to further enable exact location of the calculus, the focus width is also expediently specified to be as small as possible. Furthermore, the sample volume of the Doppler system is appropriately adapted to the hit volume of the power sound. Finally, the information mentioned is made audible to a user via a corresponding circuit unit, who thus not only sees that the stone has been hit, but also receives a corresponding acoustic signal.

The device proposed according to the invention is suitable for detecting the process of crushing solid bodies as well as cleaning surfaces, evaporation of capsules or bubbles in a water bath. The frequency range of the Doppler device is predetermined in such a way that there is only minimal impairment of the Doppler signal by the frequency of the power sound and the frequency of the imaging ultrasound system. The ultrasound transducer is expediently excited with a continuous sinusoidal signal which is generated by a quartz-stabilized, amplitude-controlled oscillator. The frequency of the transmission signal is in particular in the range of 1 MHz and the amplitude can be adapted to the requirements. Furthermore, interference in the imaging ultrasound system is avoided due to the selected Doppler frequency. The ultrasound transducer provided in the Doppler device expediently works in the CW Operation and it consists of interconnected individual elements. A ring-shaped arrangement of the elements with alternating interconnection for transmitting and receiving operation achieves a rotationally symmetrical sound field distribution in a particularly tick-like manner.

Furthermore, the transmission and reception aperture is selected such that the effective aperture forms a focus zone, which coincides with the focus of the power sound. It has proven to be particularly expedient to plug the double ring onto the image converter. Furthermore, the dimensions of the Doppler ring are dimensioned in such a way that the shading zone of the power sound provided by the image system is only slightly expanded; a restriction of the opening angle of the image system is advantageously avoided.

According to a special embodiment, the same transducer is used both for generating the power sound and for generating the ultrasound of the image system. The common transducer is therefore a component of both the performance sound system and the image system and also serves to receive the sound of the image system. In this combined system, the sound head is expediently used to direct both the power sound, in the form of pulsed ultrasound and, expediently immediately after the ultrasound power sound has ended, the sound of the imaging system, preferably as continuous sound, onto the concretion and / or the cavitation bubbles. The combined common transducer not only ensures a compact structure, but also an exact detection of the concretions and / or cavitation bubbles due to the matching focus of the image system and the power system.

It is also particularly favorable to align the focus of the Doppler converter with the focus of the power sound system and / or the detection area of the image system. The depth of field range is advantageously defined symmetrically to half the working stroke of the power transducer.

Due to the mechanical coupling of the power converter, image system and Doppler ring according to the invention, the focus on the focus area is functional guaranteed guaranteed. An existing system can be retrofitted without any problems, the Doppler unit being arranged, in particular, in a ring around the sector scanner or the image transducer. The Doppler signal is generated and evaluated by means of electronics, the analysis of the amplitude and the frequency spectrum being carried out in an analog or digital technique. The results of the evaluation can be presented optically and / or acoustically.

Furthermore, it has proven to be expedient to additionally generate the quadrature component of the Doppler signal for the digital signal processing. After digitization, the signals are forwarded to a digital signal processor, hereinafter abbreviated as DSP. The DSP makes it possible to use the in-phase and quadrature components of the Doppler signal to detect the direction of movement of a stone and its concretions, the destruction of solid bodies, the cleaning of surfaces or the like. The disintegration state of the stone or the like is determined from the amplitude behavior. The differentiation of the frequency components of the double signal provides the characteristic movement features of the stone or the like and also gives information about the nature of the stones, the bubbles or the like.

Particular refinements and developments of the invention are specified in the subclaims.

The invention is explained in more detail below on the basis of the exemplary embodiments illustrated in the drawing. Show it:

1 is a schematic representation of the Doppler converter,

2 shows a perspective illustration of the different functional areas of the components of the device,

Fig. 3 is a block diagram of the Doppler unit. 1 schematically shows a top view of the ring-shaped Doppler converter 2. This Doppler converter is arranged on a sound head of a power sound system, which is not further explained here, in such a way that both the sound head and the B-picture converter of the picture system are located in the inner free area 4. In a tested embodiment, the Doppler converter 2 has an inner diameter 6 of 33.4 mm and an outer diameter 8 of 43 mm. The ring area 10 available for the Doppler signal is divided into at least one transmitting surface 12 and one receiving surface 14. In the particular embodiment shown here, the total area of the ring area 10 is occupied by a total of sixteen circular transducers, of which eight transducers are connected as transmitters 12 and eight transducers as receivers 14, with transmitters 12 and receivers alternating evenly distributed over the circumference 14 are provided. This alternating arrangement of transmitter 10 and receiver 14 or the transmitting and receiving ceramics leads to symmetrical sound fields for the transmitter and receiver.

To adapt to the respective conditions of use and to achieve a high sensitivity, the transducers or their transmitting and receiving ceramics can be arranged inclined at a predetermined angle with respect to the plane of the ring region 10 and with respect to the axis running through the center of the annular Doppler transducer. With circular converters arranged flat or parallel to the surface of the ring region 10, a high sensitivity, namely an amplitude up to 6 dB, could be determined at a distance of 65 mm to 350 mm with a focus tube width of 4 mm diameter. By tilting the transducer outwards, corresponding to an inclination angle of -10 °, a near field with a non-uniform pressure distribution up to 130 mm was determined by the transducer. A favorable sensitivity was found at a distance of the order of 190 mm. The inclination of the transducers or the transmitting and receiving ceramics by an angle of the order of 10 ° inwards to the center produced particularly favorable results. A high sensitivity was found at a distance of 50 mm to 170 mm, the focus tube having a diameter of approx. 4 mm. The construction of the Doppler transducer with such an aperture ensures a focus tube which is long and which is narrow enough, with a diameter of 4 mm, to enable exact positioning of the Performance sound system to ensure the concretion or the like.

FIG. 2 schematically shows a sound head 16 of a power sound system, which has a focus 18. Lines 20 also indicate the detection range of the image system. The annular Doppler converter 2 is arranged around the transducer 16. The Doppler converter 2 forms a focus zone 22 or a focus tube with depth of field. According to the invention, the transmission and reception aperture is predetermined such that the effective aperture of the Doppler converter 2 forms this focus zone 22, which coincides with the focus 18 of the power sound system. The image converter of the image system is not shown here further, but this image converter is also coaxially surrounded by the Doppler converter 2. As can be seen, the focus tube or the focus zone 22 of the Doppler converter 2 is aligned with the focus or focus tube of the power sound system as well as with the detection area 20 of the image system.

Within the scope of the invention, the transducer 16 is a common component of both the performance sound system and the imaging system. The transducer is suitably focused on the area of interest, both for the power sound system and for the image system. The power sound is preferably directed in the form of pulsed ultrasound to the area of interest or the concretions and / or cavitation bubbles. For the imaging system, it is expedient to direct the concrements and / or cavitation bubbles to be examined immediately after the pulsed output sound, in particular continuous sound, has ended. The continuous sound for image acquisition has a significantly lower energy compared to the performance show. In addition, the transducer 16 is also designed as a receiver for the reflected sound for image generation by means of the image system.

3 shows the block diagram of the Doppler system, which contains a generator 30. Since in lithotripsy the stone localization is to be carried out simultaneously with the destruction of the stone with the aid of Doppler signals, the frequency of the doubler or its generator 30 is specified according to the invention in such a way that the lowest possible interference to the received Doppler signals is caused by the power sound on the one hand and by the ultrasound the B-imaging device on the other hand are to be expected. The Doppler frequency is expediently specified such that it lies in the range in which the power sound field has a minimum and can also be separated from the B-scan sound. In a special embodiment of the device, the high-performance sound system has a center frequency of 380 kHz and the image system has a center frequency of 3.5 MHz. In this constellation, a Doppler frequency, namely the transmission frequency of the Doppler converter, in the range of 1 MHz has proven to be particularly expedient. The amplitude can be adapted to the requirements.

The 1 MHz transmission signal 32 is fed to the transmitter (s) 12 of the Doppler converter 2 and transmitted by them. The echo signals received by means of the receiver (s) 14 are filtered by means of a 1 MHz bandpass 34 in order to filter out the frequency components of the power sound and the image system. The frequency of the bandpass 34 is matched to the frequency of the generator 30 and corresponds to this. The Doppler signal 38 is obtained from the filtered reception signal and the transmission signal 32 in a mixer 36 by multicative mixing. Furthermore, the mixer 36 is supplied with a signal which is 90 ° out of phase by the generator 30. The Doppler signal 38 is fed to an analog signal processing unit for the purpose of generating acoustic and optical perception signals for the movement of stone stones. Furthermore, the Doppler signal 38 is fed to a computer unit 40 in order to analyze the frequency- and amplitude-specific signal parameters and to present them as a digitally prepared audio signal on an output module 42.

In the analog signal processing mentioned, the high-frequency interference components in the Doppler signal 38 are first filtered by means of a 500 Hz low-pass filter 44, so that only the frequency range of the stone-relevant useful signal is subsequently processed. An adjustable threshold detector 46 generates a level window for the Doppler signal to suppress signals whose amplitude is either less than the minimum value set or greater than the maximum value set. The suppression of the signals with small amplitudes is effective in a range in which most of the Doppler signal is caused by slight movement of the water surface, breathing movement of the patient, vibrations of the apparatus or by other slight vibrations. The suppression of the signal components with too large Amplitudes are activated during the power pulse or when the vibrations are too great. Furthermore, a time blocking or release window 48 is generated for the Doppler signal. Immediately after the pulse of the power sound, the threshold detector 46 recognizes the high signal level of the power pulse and causes a time delay in the release window 48. The release window comprises the time period in which the largest portions of the Doppler signal originate from the Nie¬ renstein movement. The duration of the release window 48 and the delay are set according to the invention and adapted to the requirements. The signal from the blocking window 48, like that from the threshold detector 46, is fed to an analog switch 49.

The Doppler signal selected in this way is transformed into a higher frequency range by amplitude modulation by means of a modulator 50 for the purpose of better acoustic perceptibility. An oscillator 51 expediently supplies a modulation signal in the range from 0.3 to 3 kHz. The amplitude of the double signal corresponds to the intensity of the audio signal 52 and the frequency is represented in the length of the signal burst. The audio signal 52 is passed on the one hand to headphones or an optical display and on the other hand amplified by an output stage 54 for connecting a loudspeaker 56.

The quadrature component 58 of the Doppler signal 38 is additionally generated for the digital signal processing. After digitization, the signals are forwarded to a digital signal processor by means of the computer unit 40. This DSP calculates the direction of movement of the stone and the stone concrements from the in-phase components 60 and quadrature components 58 of the Doppler signal 38. Furthermore, the disintegration state of the stone is determined from the amplitude behavior. Finally, the differentiation of the frequency components of the Doppler signal 38 provides the characteristic movement characteristics of the stone, information about the nature of the stone concrements being output. Reference numerals

Doppler converter free area in 2

Inner diameter of 2

Outside diameter of 2

Ring area

Channel

receiver

Transducer

focus

Detection area of the image system

Focus zone

generator

Broadcast signal

Bandpass

mixer

Doppler signal

Computing unit

Output module

Low pass

Threshold detector

Lock window

Analog switch

modulator

oscillator

Modulation signal

Power amplifier

speaker

Quadrature component of 38

In-phase component of 38

Claims

claims

1. Device for the detection of concretions and / or cavitation bubbles, which occur during the detachment or comminution of preferably solid bodies when using ultrasound power sound, comprising a power sound system and an image system, which is preferably designed as an ultrasound system, characterized in that that a further ultrasound system with a double transducer (2) is provided, which is arranged in the area of the transducer (16) of the power sound system and / or the image system.

2. Device according to claim 1, characterized in that the Doppler¬ transducer (2) is annular and is arranged around the transducer (16) of the power sound system and / or the image system, which is within a free area (4) of the Doppler transducer (2) are arranged.

3. Apparatus according to claim 1 or 2, characterized in that the further ultrasound system has essentially the same focus as the power sound system, ultrasound waves being sent into said focus zone, which lead to a Doppler signal shift when hit.

4. Device according to one of claims 1 to 3, characterized in that the Doppler converter (2) has both at least one transmitter (12) and a receiver (14), the echo signals being picked up by means of the receiver (14) and by means of electronics processed into digital and / or yes-no hit information.

5. Device according to one of claims 1 to 4, characterized in that the transmitting and receiving electronics provided for Doppler signal processing contains an SE arrangement which consists of several elements, and / or that an element can be used alternately as a transmitter (12) or as a receiver (14) and / or that CW ultrasound can be used.

6. The device, in particular according to one of claims 1 to 5, characterized ge indicates that the Doppler frequencies are predetermined such that they lie between the imaging frequencies of the imaging transducer system and the power sound frequencies of the therapeutic sound and / or that the sample Volume of the Doppler system is adapted to the hit volume of the sound system.

7. Device according to one of claims 1 to 6, characterized in that a circuit unit (50, 51, 52, 54, 56) is provided, by means of which hit information is made acoustically audible.

8. Device according to one of claims 1 to 7, characterized in that the Doppler converter (2) is preferably distributed uniformly over the circumference and alternately has a number of transmitters (12) and receivers (14) and / or that the converter in an angular range are tilted between + 10 ° inwards to the center of the Doppler converter (2) and -10 ° outwards.

9. Device according to one of claims 1 to 8, characterized in that the individual transducers or transmitters (12) and receivers (14) are arranged inclined at a predetermined angle to the plane which is substantially orthogonal to the direction of propagation of the power sound is arranged.

10. Device according to one of claims 1 to 9, characterized in that the annular Doppler converter (2) with the power converter or the Schall¬ head and / or the image system is mechanically coupled and / or is aligned with the focus area of the power sound system .