WO1982004157A1 - Installation for transmiting and receiving focused ultrasonic waves - Google Patents

Abstract

In the installation for transmitting and receiving focused ultrasonic waves a plane oscillator (3) in the form of a disc is coupled to a liquid chamber (1). In the liquid chamber (1) there is a liquid lens (2) which contains a second liquid. The focal length of the liquid lens (2) can be changed by acting on the volume of liquid it contains. In addition, the focal point can be moved in the focal plane, for example by adjusting the angle of the plane oscillator (3) relative to the optical axis of the liquid lens (2) or by eccentric rotation of the liquid lens (2 ) with the planar oscillator (3).

Description

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Device for emitting and receiving focused ultrasound waves

The invention relates to a device for emitting and receiving focused ultrasonic waves, in particular for local heating of biological tissues, e.g. Tumors with a piezoelectric ultrasonic transducer system and a lens.

25

Ultrasonic waves can be focused just like any other type of wave. At operating frequencies between 0.5 and 5 MHz, the corresponding wavelengths are e.g. in liquids (water) between 3 and 0.3 mm and

30 in solids (steel) between lo and 1 mm. Focal spot diameters in the millimeter range are thus achieved. The advantage of focused radiation is typical applications. fertilize in diagnostics and defectoscopy with better resolution and increased sensitivity

35 and when used in therapy, in the possibility Treat deep-lying diseased areas locally while protecting the entire environment.

In addition to spherical and cylindrical concave mirrors, hollow oscillators of various geometries as well as liquid and solid lenses are known for focusing ultrasonic waves. In addition, there are converters with a synthetic aperture, in which the focusing takes place using corresponding electronic means. All known devices have the disadvantage that a targeted focal point variation in the lateral as well as in the axial direction is not possible or is relatively complex. Such a measure is, however, very important in the relevant fields of application with regard to the targeted area coverage.

The present invention is therefore based on the object of developing a focusing ultrasound transducer system with which the area to be examined or treated can be scanned in a targeted manner without great technical effort. Such a device should be usable in all relevant areas of medicine and biology as well as material testing and should be constructed as possible so that the transducer system is interchangeable.

It has now been shown that this object can be achieved with a device of the type mentioned in the introduction, in which the ultrasonic transducer system has a disk-shaped plane oscillator, in front of which a liquid chamber with a first liquid is arranged, in which one is filled with a second liquid Liquid lens is located, the focal length of the liquid lens being variable by changing the volume of the second liquid and / or the focal point in the focal plane is mechanically displaceable. Further designs of the device according to the invention are explained in subclaims 2 to 14. r

, _f . 5 The device according to the invention can be used both in medical diagnosis, for example for locating tumors, kidney stones or the like, and in therapy, for example. be used for local hyperthermia treatment. The main advantage in these areas compared to the previously known devices of this type is that the focusing converter can be easily adapted to commercially available therapy or diagnostic devices or material testing devices. As a result, a relatively large volume area can be scanned automatically with considerable gain for the useful level-noise level ratio, or any volume area can be treated as gently and specifically as possible.

The invention is explained in more detail with reference to the accompanying drawings, which only show one embodiment. It shows a schematic simplification

1 shows an embodiment of the device according to the invention, in which the focal point in the focal plane 25 can be shifted linearly or azimuthally and the focal length can be varied;

FIG. 2 shows a top view of the mounting of the ultrasound transducer system in order to achieve a linear or azimuthal displacement of the focal point in the focal plane;

FIG. 3 shows the formation of a plano-convex liquid lens *, - k -

FIG. 4 shift of the focal point in the focal plane by rotation;

FIG. 5 shows a transducer composed of diagnostic and therapeutic parts and proposed according to the invention

FIG. 6 shows the effective range of the sound during therapy operation with an axial sound-free zone

In the embodiment shown in Figure 1, the device according to the invention essentially consists of a liquid chamber 1, which contains a liquid lens 2 and a, comprising the ultrasonic transducer system 3, with the liquid chamber 1 e.g. outer housing 5 detachably connected by a threaded closure 4

The liquid lens 2 is formed from two, more or less spherically curved, elastic and hydraulically deformable membranes 6, between which a liquid, e.g. Frigen, glycerin or the like at the speed of sound c. is included. The liquid in the liquid chamber 1 has a different speed of sound c ~ and is preferably water.

The liquid volume of the lens 2 can be varied via a line 7, a cylinder 8 with a piston, which is operated by a gearwheel with a transmission 9 and a motor 10. Depending on the volume of the lens liquid, membranes 6 are more or less curved. From the radius of curvature r. , r_ of the two membranes 6 and from the sound velocities c,, c_ the focal length f of the liquid lens 2 thus formed can be calculated, according to the formula The rear half of the liquid chamber 1 does not need to be closed off by a membrane or film if the ultrasound transducer 3 is permanently installed and directly coupled. In the case of interchangeable transducers, the film 12 to which the transducer must in turn be acoustically coupled by means of a suitable coupling medium ensures unimpeded passage of energy.

A flexible bearing 15 is provided towards the liquid chamber 1 so that the planar oscillator 3 lies taut on the film 12 even when its angle of inclination with respect to the optical axis of the liquid lens 2 changes. The storage 15 is e.g. made of a metal bellows and forms part of the lateral wall of the liquid chamber 1.

In the embodiment shown in Figure 1, the faceplate 3 is placed in a housing 16 on its nλ 2-thick base plate 17, e.g. made of metal, fastened. The housing of the planar transducer 3 in such a housing 16 facilitates the interchangeability of the ultrasonic transducer system. This is expedient for a versatile applicability of the device according to the invention. For pulse-echo applications such as those used in diagnostics and defectoscopy, damped pulses can be obtained to achieve short pulses and e.g. undamped circular disk-shaped piezoelectrically arranged face-plates are used in therapy.

To replace the transducers 3, the outer housing 5 is either uncoupled from the liquid chamber 1 or provided with a window 18 through which manipulation is made possible. So that the contact with the film 12 is not lost when the angle of inclination of the planar transducer 3 or the base plate 17 changes, the housing 16 or the planar transducer is on the side opposite the liquid chamber 1 via a spring-loaded, central, in the direction of the surface normal rod 19 ge ge. This rod 19 moves. in the hollow cylinder 2o in the axial direction and the suspension 21 ensures in the zu¬

10 cooperate with the elasticity of the bearing element 15 for a tight tension of the plane vibrator 3 or the base plate 17 on the film 12. The rod 19 is on a disc 22 arranged perpendicular to the optical axis of the liquid lens 2 in a radial groove 23

15 eccentrically displaceable. This storage is illustrated in Figure 2 in plan view. The adjustment of the rod 19 or its point of contact 24 (see FIG. 2) in the groove 23 is carried out by means of an actuating device which is guided in the groove 23

20 links, e.g. achieved a screw 25. A suspension 26 from the opposite side ensures that the support point 24 of the rod 19 moves in the opposite direction in the groove 23 when the actuator 25 is retracted. This back and forth movement of the support point

__ 24 in the groove 23 _a, modification enables the angle of inclination of the plane transducer with respect to the optical axis of the liquid lens 2, and thus a linear Ver¬ shift of the focal point in the focal plane. The adjustment of the actuator 24 can be done manually as well as m x. motorized.

For effective scanning, for example in the case of defectoscopy, an azimuthal movement is superimposed on the linear displacement of the focal point described above. ₃ c For this purpose, the disk 22 is designed as a turntable, which is driven by a motor 27 with a gear ratio 28 in Rotation can be offset. When the support point 24 of the rod 19 is fixed, a circular movement of the support point on the turntable, while at the same time changing the support point 24, is achieved. According to the invention, for example, only a linear or only a circular displacement can also be brought about.

The liquid lens with the second liquid 29 can also be formed by the plane oscillator 3 on the one hand and a film 3o on the other hand, as shown in FIG. 3. In this case, a liquid chamber is only between the lens system and the area to be treated. However, this is also unnecessary if the therapy is carried out in a water bath.

A further, simpler focus shift is shown schematically in FIG. Here, the unit containing the plane vibrator 3 and the liquid lens 2 is arranged eccentrically to the axis of rotation. As usual, the rotation can be brought about by a motor. The focal length can be done manually or periodically by means of a pump by changing the lens volume.

In the embodiment shown in FIG. 5, the plane oscillator consists of two parts, namely an outer ring 31, which is undamped and is used for line radiation, and a central part 32, which is damped with a damping substance 33, for pulse echo - Business. Both parts are fastened concentrically on the base plate 34 of the housing (not shown here). The plate 34 has a ^* thickness of n λ / 2 at n = 1, 2.3. For the annular part 31 and for the central damped part 32, n can be the same or different. The proposed combination enables diagnosis and treatment to be carried out simultaneously. In certain therapeutic applications, for example hyperthermia, the temperature rise in the focal point of the therapy head is registered with a thermocouple and must be kept constant within predetermined temperature limits. With the diagnostic insert 32, the focal point can be adjusted precisely to the target area, ie the thermocouple located in the center of the target area, before the therap is carried out via the same, now adjustable lens system.

FIG. 6 shows that tissue overheating in the region of the focal point of the lens 35 is made possible when the transducer part 31, which is only intended for therapy, is used. At the same time, the sound-free leading section 36 is protected.

Due to the embodiment shown in FIGS. 5 and 6, the target area can be diagnostically explored and monitored immediately before and during therapy without the treatment head having to be replaced. If only the converter head with a lens system is adapted, simultaneous diagnosis and therapy can be carried out with commercially available generators or diagnostic devices. The low-performance use of diagnostics in the center of the therapy head reduces the transmission power only slightly in proportion to the area with the same intensity, but has a favorable influence on the axial temperature profile in the distance between the lens and the focal point. In the case of local hyperthermia of deeper tissue areas, the transducer construction according to the invention enables tissue overheating in the area of the acoustic focal point of the lens while protecting the leading section at the same time. - o _

By replacing the diagnostic part 31 with a radiation source, e.g. ^* 'Lr for rays, the inventive device for hyperthermia in combination with radiation therapy of tumors can be einge¬ sets.

Claims

Claims 1.Device for radiating and receiving focused ultrasonic waves, in particular for locally heating biological tissues, e.g. Tumors, with a piezoelectric ultrasonic transducer system and a lens. characterized . that the ultrasonic transducer system has a disc-shaped plane oscillator (3) in front of which a liquid chamber (1) with a first liquid is arranged, in which there is a liquid lens (2) filled with a second liquid, and that the The focal length of the liquid lens (2) can be varied by changing the volume of the second liquid and / or the focal point can be shifted in the focal plane. 2. Device according to claim 1, characterized in that the liquid lens (2) is formed by two elastic, sound-permeable membranes (6). OM Yλ / _ WΠ 3. Apparatus according to claim 1, characterized in that the second liquid (29) ^' be¬ between the plane vibrator (3) and an elastic, sound-permeable membrane (3o) connected to it, so that a plano-convex liquid lens is formed . 4. Device according to one of claims 1 to 3. da¬ characterized. that the focal point in the focal plane is displaceable by rotation of the unit having the plane oscillator (3), the liquid chamber (1) and the liquid lens (2). this unit being arranged eccentrically to the axis of rotation. 5. Device according to one of claims 1 to 3, characterized. that by adjusting any angle of inclination of the plane vibrator (3) with respect to the optical axis of the liquid lens (2), the focal point is displaceable in the focal plane. 6- Device according to claim 5, characterized in that the planar oscillator (3) via a central bearing rod (19) running in the direction of its surface normal on a disc ⁽ 22) arranged perpendicular to the optical axis of the liquid lens (2) in one radial groove (23) is mounted. the bearing point (24) of the bearing rod (19) being displaceable within this groove (23). so that there is a variable angle of inclination between the optical axis of the liquid lens (2) and the direction of radiation of the plane vibrator (3). 7. The device according to claim 5 or 6. characterized. that the planar oscillator (3) is mounted on a turntable (22) arranged perpendicular to the optical axis of the liquid lens (2) via a central bearing rod (19) running in the direction of its surface normal. the point of contact (24) of the bearing rods (9) on the turntable (22) describes an azimuthal movement when rotating. 8. Device according to one of claims 1 to 7. da¬ characterized in that the facing oscillator (3) with the liquid chamber (1) via an elastic bearing element (15) preferably. is detachably coupled, the bearing element (15) forming at least part of the side wall of the liquid chamber (1), and that the bearing rod (19) is sprung to achieve a firm coupling between the plane oscillator (3) and the liquid chamber (1) (21) is. 9. Device according to one of claims 1 to 8, da¬ characterized in that the liquid chamber (1 at the coupling point to the plane oscillator (3) and to the radiation side is each closed by a sound-permeable film (11. 12) and that an acoustic passage between the swinger (3) and the film (12) is made possible. 10. The device according to one of claims 1 to 9, characterized in that the plane oscillator (3) in a removable housing (16) on the n / 2- thick 3odenplatte (17) of the housing (15) is attached. 11. The device according to one of claims 1 to lo, da¬ characterized in that in the liquid chamber (1) an air-filled, elastically sealed compensation chamber (14) for volume compensation with volume change or focal length change of the liquid lens (2) is provided is. 12. The device according to one of claims 1 to 11, characterized in that the plane oscillator is composed of two concentrically arranged parts (31, 32), an outer annular undamped part (31) for power radiation and a central, steamed Part (32) are provided for pulse-echo operation. 13. The apparatus according to claim 1, characterized in that the plane oscillator (1,2) is mounted on a plate (34) having a thickness of n ^' λ / 2, at n = l, 2.3. has, the integer n for the central part (32) being able to differ from that of the corresponding ring-shaped part (31). 1 . Device according to claim 12 or 13, characterized in that the damped part (32) is replaced by a radiation source for the combined hyperthermia and radiation treatment. ; R O?