Device fittable to the therapy head of an x-ray guided lithotripsy system to allow adjustment of the focus thereof

A device to adjust the focus position of the therapy head of a lithotripsy system having an x-ray system, has a cross-hair disc that can be attached to an image intensifier of the x-ray system, such that extending away from the edge of the cross-hair disc are variable-length connection elements whose outer end facing away from the cross-hair disc can be indirectly or directly affixed to the image intensifier.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns a device for adjustment of the focus position of the therapy head of a lithotripsy system.

2. Description of the Prior Art

Adjustment of the position of the focus of the therapy head of a lithotripsy system can be accomplished using an x-ray system, usually in the form of a C-arm x-ray system. The x-ray system, having an x-ray source and an image intensifier, serves for imaging during a kidney stone treatment. For adjustment of (setting) the shockwave focus onto a central point detectable by the x-ray system from different angles, a target marking on the image intensifier of the x-ray system is necessary in the case of such a C-arm. This is the isocenter. A device serving for this purpose is a cross-hair disc that is affixed on the image intensifier with a fastening device. The target marking furthermore serves for positioning the shockwave focus in a stone to be treated. Such a cross-hair disc is formed of a material permeable to x-rays. A target or cross-hair made from a material that can be imaged in the image intensifier is disposed in its center. In the case of lithotripsy systems with an integrated x-ray system, the image intensifier is already provided at the factory with a cross-hair disc that is attached on the image intensifier such that cross-hair disc cannot be adjusted. To accommodate users undertaking only a small number of stone treatments, in more recent times the fixed mechanical coupling between the x-ray systems and the lithotripsy systems has been abandoned, particularly for cost reasons. Mobile lithotripsy systems are used that can be assigned to an arbitrary x-ray system via a mechanical interface. This allows the use of existing x-ray systems, used for other purposes, for lithotripsy as well. A problem, however, is the cross-hair disc is missing on the image intensifier, because the x-ray system is used otherwise.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a device of the above-described type with which differently-configured image intensifiers can be retrofitted.

This object is achieved by a device according to the invention to the invention having, extending from the edge of the cross-hair disc, variable-length connection elements whose outer ends point away from the cross-hair disc, and that can be indirectly or directly affixed to the image intensifier. By means of the variable-length connection elements, an adaptation to image intensifiers with different diameters is possible, and thus retrofitting of practically any x-ray system can be achieved.

Given the attachment of a cross-hair disc, due to tolerance variations it may be necessary that a centering of the disc must be undertaken. In such a centering, the cross-hair center is caused to overlap the center point of the entrance surface of the image intensifier. The center point of the entrance surface often does not coincide with the geometric center point of the image intensifier housing. In a preferred embodiment, three connection elements are provided, preferably uniformly distributed around the circumference of the cross-hair disc. These allow a simple adjustment of the cross-hair disc in arbitrary directions, such that centering of the cross-hair can be effected in a simple manner dependent on the existing relationships.

In an embodiment, the outer end of the connection element is affixed on a mounting device attached to the outer circumference of the image intensifier. In another embodiment that involves little technical outlay a mounting element that can be affixed on the outer circumference of the image intensifier is associated with each connection element. The mounting elements are in turn affixed in a manner that can likewise be realized simply by a tightening strap (tensioning band) placed around the outer circumference of the image intensifier and clamping the mounting elements to the image intensifier. The mounting elements preferably are affixed to the image intensifier such that they can be detached. Even given a fixed connection between the cross-hair disc, the mounting elements and the connection elements, it is possible to remove the cross-hair disc from the image intensifier as needed. This is achieved in a particularly simple manner, without tools, when the tightening belt made from elastic material. It is naturally also be possible to affix the cross-hair disc to the connection elements such that it can be detached.

In a preferred exemplary embodiment, the length variability of a connection element is achieved by dividing it into a number of length sections demarcated from one another by predetermined breaking points. Each length section has a fixing element with which the connection element can be affixed on the edge of the cross-hair disc. Depending on the diameter of the image intensifier to be retrofitted, the connection elements are shortened by breaking off one or more length sections. Forming the fixing elements as a bore penetrating a length section ensures a simple attachment of the connection element on the edge of the cross-hair disc, which has bores at corresponding locations. The mechanical connection between these parts can ensue simply using screws or rivets. A snap connection between the outer end of a connection element and a mounting element ensures that the cross-hair disc can be removed from the image intensifier together with the connection elements affixed to the cross-hair disc. The entrance surface of the image intensifier, which faces an x-ray source, is then completely free of foreign elements. At most, mounting elements remain on the outer circumference of the image intensifier.

The aforementioned connection elements with predetermined breaking points allow a step-by-step adaptation to image intensifiers of different diameters. In this embodiment, however, a stepless (continuous) adaptation is possible by disposing an adjustment part between the outer end of a connection element and a mounting element. With this adjustment part, the distance between the connection element and the mounting element can be varied to an extent corresponding to the length of a length section that can be broken off.

In a further preferred exemplary embodiment, length variability of the connection element is achieved by forming the connection element of elastic material, so it is extensible in its longitudinal direction. The connection element is preferably affixed to the mounting element such that it can be detached. The elastic force and the gripping length of the connection element can be adapted to respective diameter ratios.

In a further embodiment, it is unnecessary to attach a mounting device on the outer circumference of an image intensifier. Rather, the affixing of the cross-hair disc ensues by fashioning the outer ends of the connection elements as hooks. The hook-shaped ends can be attached on the outer circumference of the image intensifier. The retention force necessary for a secure attachment is achieved by at least one hook-shaped end is that pre-stressed in the direction of the outer circumference surface of the image intensifier. Such a pre-stress is achieved by coupling a spring-loaded leg of flange, interacting with the outer circumference surface of the image intensifier, to the outer end of a connection element. By such a spring leg, in addition to a secure fastening a certain adaptation to differently-dimensioned image intensifiers is possible. This is achieved to an even greater degree in a preferred embodiment wherein a connection element has a first section affixed to the cross-hair disc and a second section formed by a hook-shaped end, and both sections can be affixed to one another in different longitudinal positions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a lithotripsy system as is appropriate for a user with low demand for stone treatments. It has a mobile patient table 1, a mobile x-ray C-arm apparatus2that can also be used for other purposes, and a likewise mobile lithotripter3. These assemblies are affixed to one another by a common mechanical interface4. The x-ray C-arm apparatus2has a C-arm5with an x-ray source6mounted at one end thereof and an image intensifier7mounted at the opposite end. Before the implementation of a stone treatment, the focus point8of the therapy head9of the lithotripter3has to be adjusted such that it is intersected by a central beam10of the x-ray source6, and so it is additionally arranged in the isocenter of the x-ray C-arm apparatus2or at least in the proximity thereof. To show the focus point, a folding (hinged) bracket or clip12, that carries a metal ball visible in the x-ray image, is disposed at the therapy head9. To adjust the focus point, a cross-hair disc14(not shown inFIG. 1) is necessary that is applied on the entrance surface13of the image intensifier7. For systems used exclusively for lithotripsy, the image intensifier is already equipped at the factory with a removable cross-hair disc. For an x-ray C-arm apparatus2or another x-ray system that is used for other medical purposes, however, retrofitting with a cross-hair disc is necessary. Such a disc as well as a device with fastening elements is described in the following.

FIGS. 2 through 4show two exemplary embodiments of a first device variant which involves a mounting device16that can be affixed to the outer circumference surface15of the image intensifier7. In the mounted state (which is always referred to in the following) wherein the adjusted cross-hair disc14lies on the entrance surface13such that the cross-hair17that is present on it marks the entrance point of the central beam10or the x-ray-optical center of the entrance surface13. The cross-hair disc14is connected with the mounting device16by connection elements18uniformly distributed around the circumference of the image intensifier7. The mounting device16includes three mounting elements19clamped to the outer circumference surface15with a tightening strap20, with which mounting elements19the radially outlying ends22of the connection elements18are mechanically coupled. The connection elements18are fashioned in strips and are produced from a solid material, such as aluminum plate. The connection elements18are divided into a number of length sections24separated from one another by predetermined breaking points23formed by notches proceeding transversely. By breaking one or more length sections24, an adaptation to the respective diameter of the image intensifier7can ensue. Each length section24is penetrated by a bore25that serves to affix the connection element18to the cross-hair disc. This has a reinforced edge27, for example likewise made from an aluminum material, in which a bore26is present. The fastening of the connection element17ensues, for example, by a screw (not shown) engaging through both bores22,26. In the region of the connection element18, the edge27has a projection28directed radially inwardly, penetrated by a bore31and serving for affixing the cross-hair disc14.

The outer end22of a connection element18is bent into a hook shape. The angle α between the curved section29and the remaining connection element is smaller than 90°. A central groove30proceeding in the longitudinal direction of the connection element18is present on the side of the section29, pointing radially outwardly. A pressure (thrust) piece32affixed on the respective mounting element19, engages in this groove with a catch element (not shown) spring-loaded in the engaging direction. The engagement point on the section29is positioned such that the end22of the connection element18is loaded (stressed) with a force directed toward the entrance surface13, resulting from the oblique position of the section29. To remove the cross-hair disc14, the connection elements are removed from the image intensifier in the direction of the arrow33. The application ensues in the opposite direction. The pressure piece32and the section29cooperate in the sense of a snap connection. With an adjustment screw33, the spring-loaded catch piece engaging in the groove30in the radial direction can be adjusted by a range that approximately corresponds to the length34of a length section24.

The mounting elements are plate pieces, designed as an angle section, with one leg35abutting the outer circumference surface15and with the other leg36abutting on the entrance surface13of the image intensifier7. A clip37that carries the pressure piece33and extends the leg35over the entrance surface13projects from the leg35. The leg35nearly abuts (with extended contact) the outer circumference surface15with curved side edges41.

FIG. 4shows an exemplary embodiment in which the connection elements18aare produced from elastic material in the form of a band. Affixing to the cross-hair disc14can ensue by means of a slot38through which the radial inner end of the connection element18ais guided to form a tab. The outlying end22is clamped to the mounting element19asuch that it can be detached. The clamping ensues via a web39extending away across the connection element18a, the overhanging ends of which web39are screwed to the mounting element19a. A certain margin in the adaptation to differently-dimensioned image intensifiers7exists solely via the elasticity of the connection elements18a. The degree of the radial adaptation capability can still be increased by clamping the connection elements18ato different longitudinal positions. By variation of the tension state or of the clamp position of individual connection elements18a, centering of the cross-hair17on the center point of the entrance surface13is also possible in a simple manner. The mounting elements19aare clamped via an elastic tightening strap20ato the outer circumference surface13of the image intensifier7. The tightening strap is clamped with its two ends to the outside of a mounting element19′ with the aid of two webs39′. The remaining mounting elements19aare affixed on the tightening strap20ain the same manner, namely with a web39′. In order to achieve a defined axial position for the mounting elements19a, these exhibit a plate-shaped stop (catch)40extending radially inwards on their side facing the entrance surface13. The plate-shaped stop40abuts the entrance surface13of the image intensifier7.

A variant is shown inFIG. 5 through 7in which the fastening to an image intensifier7ensues with the connection elements18bthemselves. The connection elements18bare formed by a first section42and a second section43. The first section42is an essentially plate-shaped part with a rectangular contour shape. A recess44extending across its entire length is introduced onto its side facing the entrance surface13in the mounted state. The width of the recess44is less than the width of the first section42, such that the recess44is flanked by two lateral edge strips. The first section42is furthermore penetrated by a centrally-arranged oblong hole46proceeding parallel to the lengthwise extent of the recess44. A recess47that accommodates the edge27of the cross-hair disc14is present in the back side (facing the cross-hair disc14) of the first section42. In the region of the recesses47, the edge strips45each have a bore51with which the section42can be affixed (screwed) to the edge27.

The second section43is an elbow formed by two flat legs. With lateral guiding by the edge strips45, the first leg48inserts into the recess44(lengthwise shifting), and the second leg49forms an angle β (which is smaller than 90°) with the first leg48. In the mounted state, the second leg49abuts on the outer circumference surface15of an image intensifier7. Because the angle β included by both legs is smaller than 90°, the second leg49abuts the image intensifier with only its free end. In the region of the groove (connecting both legs48,49) of the second section42, in this manner a space is achieved that, for example, can accept an edge of the image intensifier, expanded like a bulge, that includes the entrance surface. The first leg48has a centrally-arranged series of threaded holes52. A screw (not shown) engaging the oblong hole46is screwed with its thread end into at least one of the threaded holes52. In this manner, the second section43can be affixed to the first section42in different longitudinal positions, and the device thus can be adapted to differently-dimensioned image intensifiers. One of the three connection elements19b, namely that provided inFIG. 8with the reference character18′b, is designed such that it exerts a force on the outer circumference surface15of the image intensifier7, and thus the remaining two connection elements18bpress on the circumference surface15of the image intensifier7with their two legs49. Both legs48′ and49′ of the connection element18′bare essentially designed the same, like the corresponding leg of the connection element19b. However, the second leg49′ can pivot on the first leg48′ on an axis proceeding parallel to the planning level of the legs48′,49′. Both legs48′,49′ are connected via two coaxial coil springs arranged next to one another. The respective outer spring ends54are connected with the leg48′ and the respective inner spring ends55are connected with the second leg55. An axial separation into which protrudes an extension56formed on the back side of the leg49′, is present between the two leg springs53. The extension56is shaped to a web57extending inwardly on both sides in the coil springs53within the leg springs53. The web57serves for position fixing or as a pivot axle given a pivoting of the leg49′.

A device or an add-on kit of the specified type can include a number of cross-hair discs14with different diameters so that, in addition to the length variability of the connection elements18, a further adaptation to image intensifiers7of different sizes is achieved.