EP1445758A2 - Lens system for a shock-wave generator - Google Patents

Abstract

Lens system comprises lens elements (2, 4) with one element rotating about an axis of rotation within the radiation path. The lens elements have non-rotational symmetrical bending and/or phase shifting characteristics with respect to the axis of rotation.

Description

The invention relates to a lens system for a shock wave generator with at least two lens elements.

Shock wetting generators are used, for example, in therapy facilities for treatment stone disorders (lithotripsy), tumor disorders and bone disorders (osteo-restoration) used. Shock wave sequences are used to smash kidney stones, for example generated by a shock wave source, which on the concrement in Body to be focused. With the devices available today, the geometric Shape and the time course of the shock waves through the structure and geometry of the Source and focus elements set.

An important concern when designing the shock sources is on one Side to improve the effectiveness of the smashing and on the other side reduce the side effects of acoustic energy not absorbed by the stone. Investigations on electrohydraulic shock sources (electrode sources) have shown that the shock waves generated in relation to the ratio of effect to side effect can be improved by having part of the shock wave front compared to the main shaft is so delayed that the focus and train components occurring in its surroundings by superimposing positive ones Proportions from the delayed wave are reduced, thereby reducing the side effects responsible cavitation tendency is reduced. Attempts by the applicant with delay lines in the shock wave path have shown that it is possible by delay from parts of the shock wave front to the peak pressures in the focus axis reduce. In doing so, significantly reduced throughputs of acoustic energy the therapy focus can be realized without regard to the effectiveness of the single pulse reduce its smashing effect.

The frequently used electrohydraulic process is generated by the extra-focal Spark jump a temporal stretch and a lateral smear of the focus profile. The electromagnetic source produces especially in large apparatus geometrically and temporally exact pulses, which - supported by nonlinear effects - lead to very sharp bundling. Sharp and out of focus lead to different crushing mechanisms which, depending on the stone size, Stone composition and smashing progress suitable in different ways can be used.

A shock wave generator is known from EP 0 254 104, which has a focusing device with multiple lenses. One or more lenses either introduced into or out of the beam path or the shock wave path taken out. By inserting and removing the lenses, the Focus width can be changed.

A first disadvantage of this prior art is that only the focus geometry, however, the pulse profile cannot be changed. Also requires this method of inserting and removing the lenses is a relatively voluminous one Shock wave generator.

EP 0 448 291 discloses an ultrasound probe in which, in addition to a piezoelectric Element arranged a shaft for rotating one or two diffraction parts is to introduce different sections of a diffraction part into the beam path.

It is therefore the object of the invention to provide a lens system which has a Changing the focus geometry and the pulse profile of shock waves enables and can also be produced in a compact design.

This object is achieved by a lens system according to claim 1. Accordingly According to the invention, a lens system for a shock wave generator with at least two lens elements are provided, at least one lens element is rotatable about an axis of rotation within the beam path and at least two lens elements with respect to the axis of rotation a non-rotationally symmetrical Have diffraction and / or phase shift characteristics.

Below and below a lens element is a radiatable element understood that is suitable to change an acoustic beam. The change can consist, for example, of focusing or a phase shift. The term diffraction characteristic does not necessarily imply that the corresponding lens element focuses the beam; also an expansion of the Beam is possible. A lens element can also only be a phase shift of part or all of the beam without focusing it. In this In this case, a further lens element can be provided, which is only for focusing serves. In addition to the at least two lens elements, a lens element with a rotationally symmetrical diffraction and / or phase shift characteristic be provided.

The non-rotationally symmetrical phase shift characteristic can be continuous or be non-continuous.

The at least two lens elements do not necessarily have to have the same diffraction and / or have phase shift characteristics. As detailed below it is often useful if they have different diffraction and / or Have phase shift characteristics.

The non-rotationally symmetrical diffraction and / or phase shift characteristic of the at least two lens elements allows changing and adjusting the Focus and the pulse profile by rotating the at least one lens element around the axis of rotation. This results in compact dimensions of the lens system ensures that the axis of rotation within the beam path or acoustic Waves lies. The lenses do not have to, as described in the above State of the art, are each introduced into the beam path.

It should be noted that the at least one lens element of the invention Lens system is not necessarily designed to be in an optical path the entire wave cross section (for example, a shock wave) recorded. The The lens element also does not have to completely surround and / or in the axis of rotation be formed symmetrically with respect to the axis of rotation.

According to an advantageous development, the at least two lens elements arranged coaxially and the common axis be the axis of rotation.

In a coaxial arrangement, each lens element has - at least what its circumferential shape in the plane perpendicular to the axis of rotation - symmetry with respect this axis of rotation. For example, a lens element could be one have circular circumference. The coaxial arrangement makes it easier and compact structure. It is also easy to set up or adjust of the lens positions possible.

To set a specific focus or pulse profile, the at least two Lens elements are brought into a predetermined relative position to each other. This can be achieved in that a lens element is fixed during the another is movable about the axis of rotation. But it can also all lens elements be rotatable. If there are more than two lens elements, some can alternatively be used the lens elements can be moved while others are fixed.

In an advantageous development, the diffraction and / or phase shift characteristics can which at least two lens elements are designed in such a way that the diffraction and / or phase shifting effect of the at least two lens elements in a first predetermined relative arrangement of the at least two Maximum lens elements and in a second predetermined relative arrangement is minimal.

In the first predetermined relative arrangement of the at least two lens elements So can the diffraction and / or phase shift effects of the lens elements intensify while they are in the second predetermined relative Compensate the arrangement at least partially.

In an advantageous development, at least one second lens element can be a have such diffraction and / or phase shift characteristics that the combination of the at least one and the second lens element in a predetermined relative arrangement of the lens elements a rotationally symmetrical Diffraction and / or phase shift characteristic has. In this way can the non-rotationally symmetrical diffraction and / or phase shift characteristic of the at least one lens element by a predetermined relative Position of at least a second lens element can be compensated so that the entire characteristic of the one and the second lens element rotationally symmetrical is.

According to an advantageous development, the second lens element can be the same Diffraction and / or phase shift characteristics like the at least one Have lens element. So that the diffraction and / or phase shift effect of the two lens elements, if these with respect to the axis of rotation in are in the same position, maximally reinforced. This further training also allows a simple one Production of the lens element.

According to an advantageous alternative, the second lens element can be one of the at least one lens element with inverse diffraction and / or phase shift characteristics exhibit. This way it can be in a predetermined relative Arrangement of the two lens elements compensates for the non-rotationally symmetrical Diffraction and / or phase shift effect of the at least a lens element can be achieved. If, for example, the at least one lens element The second lens element can have a convex curvature in one region have a concave curvature in a corresponding area. This can be achieved in a first relative arrangement of the lens elements maximizes the diffraction and / or phase shift effect becomes; in a different relative arrangement can compensate for the effect be achieved. These are preferably at least one and the second lens element formed such that the relative arrangement of the two lens elements with minimal effect through a relative rotation of 90 ° from the maximum position Effect arises.

In an advantageous development of the lens systems described above, this can at least one lens element has a non-rotationally symmetrical distribution of thickness. Preferably the thickness distribution can be non-continuous. this makes possible an exact setting of a defined focus and / or pulse profile.

As previously mentioned, a lens element does not have to have an entire wave cross section include. Preferably, the at least one lens element in Be ring-shaped. This leaves some of the beam unaffected.

In an advantageous development, at least one lens element can at least include two materials. By a suitable choice of materials with certain Velocity of sound can thus be lens elements with desired Characteristics are produced.

The at least one lens element can advantageously be a dimensionally stable material, especially polystyrene.

The invention also provides a shock wave generator with a lens system kind previously described. The use of such a shock wave generator allows the shock waves to be adapted to the respective patient during therapy while reducing side effects while maintaining effectiveness.

Figur 1

in schematischer Darstellung ein erstes Ausführungsbeispiel eines erfindungsgemäßen Linsensystems in einem Stoßwellengenerator;

Figur 2

in schematischer Darstellung ein zweites Ausführungsbeispiel eines erfindungsgemäßen Linsensystems in einem Stoßwellengenerator mit einer ersten relativen Anordnung der Linsenelemente;

Figur 3a

das Fokusprofil der Linsenanordnung von Figur 2;

Figur 3b

das Pulsprofil der Linsenanordnung von Figur 2;

Figur 4

das zweite Ausführungsbeispiel mit einer anderen Anordnung der beiden Linsenelemente;

Figur 5a

das Fokusprofil für die Anordnung der Linsenelemente von Figur 4; und

Figur 5b

das Pulsprofil für die Anordnung der Linsenelemente von Figur 4.

Further features and advantages in the invention are described in more detail with reference to the following drawings. It shows

Figure 1

a schematic representation of a first embodiment of a lens system according to the invention in a shock wave generator;

Figure 2

a schematic representation of a second embodiment of a lens system according to the invention in a shock wave generator with a first relative arrangement of the lens elements;

Figure 3a

the focus profile of the lens arrangement of Figure 2;

Figure 3b

the pulse profile of the lens arrangement of Figure 2;

Figure 4

the second embodiment with a different arrangement of the two lens elements;

Figure 5a

the focus profile for the arrangement of the lens elements of Figure 4; and

Figure 5b

the pulse profile for the arrangement of the lens elements of Figure 4.

Figure 1 shows an embodiment of a shock wave generator according to the invention. The shock wave generator comprises a shock source 1, which is, for example around a plane (as shown in the figure) or a cylindrical electromagnetic Source, a flat or dome-shaped piezoelectric source can act. A convex lens 2 is arranged in the beam path of the shock wave serves the shock wave. In the side of the lens 2 facing away from the shock source depressions 3 are arranged.

The lens 2 is made of a material with a speed of sound other than the surrounding medium (e.g. water). Because of the recesses 3 are parts of one Shock wave, which leave the lens 2 in the areas of the recesses 3 opposite other parts of the shock wave, which from the lens 2 in other areas of the Emerge surface, out of phase. The depressions 3 are in this embodiment formed in the form of steps; the lens element 2 thus has one non-continuous thickness distribution.

Another lens element comes after the lens element 2 in the radiation direction 4, which is used only for the phase shift; it is not used for focusing. Elevations 5 are arranged on the lens element 4. The amount of increases 5 corresponds to the depth of the depressions 3. Both lens elements 2 and 4 are arranged coaxially with respect to the axis 6, the lens element 4 about the axis 6 is rotatable, as indicated by the arrow.

In the relative position of the lens elements 2 and 4 to one another shown in FIG. 1, compensate for the phase shifts achieved by the depressions 3 and elevations 5. Due to the corresponding deceleration or acceleration distances in the lens elements 2 and 4, have the two lens elements mutually inverse phase shift characteristics. The resulting shock wave front is indicated by the line with the reference number 9.

If the lens element 4 is rotated about the axis 6, so that the steps 3 and 5 are not more on top of each other, a shock wave passes depending on the area of the lens elements 2 and 4 different distances in the lens material. Experience this Parts of the shock wave, depending on the material selected, an acceleration or a deceleration towards other parts of the shock wave.

Instead of the shape shown in FIG. 1, the depressions 3 and elevations 5 also extend to the center of the lens elements. In addition to the stages shown With a certain height or depth, other levels with different levels Height or depth exist. The levels shown can also be different Have dimensions; this applies to both levels within one of the Lens elements as well as for the steps in different lens elements.

The lens elements can be made of a material with a higher speed of sound (e.g. polistyrene) or with a lower sound speed (e.g. silicone rubber) than the surrounding medium (e.g. water) exist. Because of The lens elements can be dimensionally stable from a dimensionally stable material such as Be made of polistyrene.

The rotation of the lens element 4 can be done manually by a lever from the outside or with a servomotor. The other lens element 2 can also be moved his.

Figure 2 shows another embodiment of a shock wave generator according to the invention. In this example, one comes after the electromagnetic source 1 convex lens 2, which is used only for focusing. The lens 2 is followed by two lens elements 7 and 8, each having the same phase shift characteristic exhibit. In the arrangement shown, the thickness of the lens element increases to the left and right from the center.

In Figure 2, the lens elements 7 and 8 are arranged to each other such that the phase shift of both lens elements is intensified as the phase delays Areas (for a material with a lower speed of sound as the surrounding medium).

The resulting shock wave front is indicated by line 9. How to recognize the edge areas to the left and right of the wavefront are compared to one not delayed shock wave front 10 remained somewhat. The corresponding Pressure distribution in focus 11 results from the isobars shown.

The location dependence of the pressure p is shown again in FIG. 3a. You can see that spatial defocusing of the shock wave front. Figure 3b shows the pulse profile. Also the temporal defocusing of the shock wave front is therefore maximum.

In Figure 4, the embodiment of the lens system of Figure 2 is shown, wherein here the lens elements 7 and 8 relative to the arrangement shown in FIG. 2 by 90 ° are twisted against each other. The phase shifts are thus compensated for. Each part of the shock wave passes through the same material thickness with the surrounding medium deviating speed of sound, so the entire shock wave front experiences the same acceleration or deceleration. The resulting shock wave front 10 thus corresponds to that of a shock wave generator without lens elements 7 and 8.

The resulting pressure distribution or the resulting pulse profile are shown in FIG. 5a and 5b. It can be seen that the shock wave is both spatial (FIG. 5a) and is maximally focused in time (FIG. 5b).

The lens elements shown in the exemplary embodiments are merely illustrations of the lens system according to the invention. It is clear that, for example, the lens elements 7 and / or 8 can also be arranged in front of the convex lens 2. Also other combinations of lens elements are especially with others Thickness distributions or from different materials possible.

Flat electromagnetic shock sources are shown in the exemplary embodiments. Lens elements for other sources of shock (e.g. cylindrical or dome-shaped Sources) can be constructed in an analogous manner.

Claims (12)

Lens system for acoustic waves with at least two lens elements (2, 4; 7, 8), wherein at least one lens element about an axis of rotation within the Beam path is rotatable and the at least two lens elements with respect to the Rotation axis not rotationally symmetrical diffraction and / or phase shift characteristics exhibit. The lens system of claim 1, wherein the at least two lens elements are coaxial are arranged and the common axis is the axis of rotation (6). A lens system according to claim 1 or 2, wherein the diffraction and / or phase shift characteristics of the at least two lens elements formed in this way is that the diffraction and / or phase shift effect of the at least two lens elements in a first predetermined relative arrangement predetermine the at least two lens elements to a maximum and in a second relative arrangement is minimal. Lens system according to one of the preceding claims, wherein at least a second lens element has such a diffraction and / or phase shift characteristic has that the combination of at least one and second lens element in a predetermined relative arrangement of the lens elements a rotationally symmetrical diffraction and / or phase shift characteristic having. The lens system of claim 4, wherein the second lens element has the same diffraction and / or phase shift characteristics like the at least one lens element having. The lens system of claim 4, wherein the second lens element is one of the at least one lens element with inverse diffraction and / or phase shift characteristics having. Lens system according to one of the preceding claims, wherein the at least a lens element has a non-rotationally symmetrical thickness distribution. The lens system of claim 7, wherein the thickness distribution is non-continuous. Lens system according to one of the preceding claims, wherein the at least a lens element is formed in a ring shape. Lens system according to one of the preceding claims, wherein the at least a lens element comprises at least two materials. Lens system according to one of the preceding claims, wherein the at least a lens element comprises a dimensionally stable material, in particular polystyrene. Shock wave generator with a lens system according to one of the preceding Expectations.

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