SHOCK WAVE DEVICE HAVING A SOURCE SELF ALIGNING WITH AN X-RAY DEVICE

Abstract

A shock wave and/or ultrasound therapy system includes an ultra-sound and/or shockwave source suspended on a hexapod drive and an X-ray system. A system controller configured to generate control signals for the hexapod drive to align the ultrasound and/or shockwave source with the X-ray system based on the displacement of a known object between two images taken at different tilt angles of the X-ray system.

Claims

1. A shock wave and/or ultrasound device comprising an ultrasound and/or shockwave source and a base, wherein the ultrasound and/or shockwave source are suspended on a hexapod drive, the hexapod drive including six linear actuators, wherein the six linear actuators are attached in pairs to three positions at the base, crossing over to three mounting positions at the ultrasound and/or shockwave source.

2. The shock wave and/or ultrasound device according to claim 1, wherein each connection of one of the linear actuators to either the base or the ultrasound and/or shockwave source includes a universal joint or a ball joint and/or wherein the linear actuators include at least one of a hydraulic jack and a pneumatic jacks and electric linear actuators.

3. The shock wave and/or ultrasound device according to claim 1, wherein the hexapod drive is configured to provide a movement with at least five degrees of freedom including a displacement along three orthogonal axes and at least two degrees of tilt.

4. The shock wave and/or ultrasound device according to claim 1, wherein the shock wave and/or ultrasound device is arranged in a cartesian coordinate system with a y-axis being a longitudinal axis through a center of a patient table, an x-axis being orthogonal to the y-axis and in a plane of a surface of the patient table, and a z-axis being orthogonal to the plane of the surface of the patient table and orthogonal to the x-axis and the y-axis and in a direction upward from the patient table.

5. The shock wave and/or ultrasound device according to claim 1, wherein the ultrasound and/or shockwave source is configured to generate shock waves that propagate in a direction towards a patient table located above the ultrasound and/or shockwave source and that have a focal volume above the patient table.

6. The shock wave and/or ultrasound device according to claim 1, wherein the hexapod drive is coupled to a movement sensor and configured to effectuate a tilting movement as a function of a movement sensor signal from the movement sensor.

7. The shock wave and/or ultrasound device according to claim 6, wherein the movement sensor comprises at least one of a respiration sensor, a camera, and a heart pulse sensor.

8. The shock wave and/or ultrasound device according to claim 1, wherein the hexapod drive is configured to provide a first movement in a direction of a center axis of the ultrasound and/or shockwave source and concurrently a second movement laterally and/or rotationally to avoid and/or remove air bubbles at an exterior surface of a cushion covering the ultrasound and/or shockwave source.

9. The shock wave and/or ultrasound device according to claim 1, wherein the hexapod drive is configured to provide a spiral movement in a plane orthogonal to a center axis combined with a translation in a direction of the center axis.

10. A shock wave and/or ultrasound therapy system comprising an ultrasound and/or shockwave source and an X-ray system, wherein the ultrasound and/or shockwave source is suspended on a hexapod drive, and wherein a system controller is provided and configured to generate control signals for the hexapod drive to align the ultrasound and/or shockwave source with the X-ray system.

11. The shock wave and/or ultrasound therapy system according to claim 10, wherein the system controller is configured to generate control signals to align the ultrasound and/or shockwave source with the X-ray system based on a displacement of a known object between two images taken at different tilt angles of the X-ray system.

12. The shock wave and/or ultrasound therapy system according to claim 10, wherein the hexapod drive includes six linear actuators that are attached in pairs to three positions at a base, crossing over to three mounting positions at the ultrasound and/or shockwave source.

13. The shock wave and/or ultrasound therapy system according to claim 10, wherein the hexapod drive is configured to provide a movement with at least five degrees of freedom including a displacement along three orthogonal axes and at least two degrees of tilt.

14. The shock wave and/or ultrasound therapy system according to claim 10, wherein the system controller is configured to align: an axis of the ultrasound and/or shockwave source defined by extending from a center of the source to a center of a focal area with an axis of the X-ray system defined by a path of an X-ray beam between an X-ray source and a detector.

15. The shock wave and/or ultrasound therapy system according to claim 10, wherein the shock wave and/or ultrasound therapy system includes a focal phantom that further includes a first X-ray absorbing object and a second X-ray absorbing object distant from each other in a direction of a center axis of the ultrasound and/or shockwave source and arranged symmetrically with respect to the center axis of the ultrasound and/or shockwave source.

16. The shock wave and/or ultrasound therapy system according to claim 15, wherein the system controller is configured to control the X-ray system to take at least one X-ray image, and to calculate centers of and/or a distance between a first X-ray absorbing object and the second X-ray absorbing object, and to estimate a displacement of center axes between a center axis of the ultrasound and/or shockwave source and a center axis of the X-ray system by a system controller.

17. The shock wave and/or ultrasound therapy system according to claim 16, wherein the system controller is configured to calculate a displacement of the ultrasound and/or shockwave source required to align with the X-ray system based on the displacement of center axes.

18. The shock wave and/or ultrasound therapy system according to claim 15, wherein the focal phantom comprises X-ray absorbing objects having different sizes and a symmetrical structure.

19. The shock wave and/or ultrasound therapy system according to claim 18, wherein the X-ray absorbing objects are rings of different diameters.

20. The shock wave and/or ultrasound therapy system according to claim 10, wherein the shock wave and/or ultrasound therapy system is arranged in a cartesian coordinate system with a y-axis being a longitudinal axis through a center of a patient table, an x-axis being orthogonal to the y-axis and in a plane of a surface of the patient table, and a z-axis being orthogonal to a plane of the surface of the patient table and orthogonal to the x-axis and the y-axis and in a direction upward from the patient table.

21. The shock wave and/or ultrasound therapy system according to claim 10, wherein the ultrasound and/or shockwave source is configured to generate shock waves that propagate in a direction towards a patient table located above the ultrasound and/or shockwave source and that have a focal volume above the patient table.

22. The shock wave and/or ultrasound therapy system according to claim 10, wherein the hexapod drive is coupled to a movement sensor and configured to effectuate a tilting movement as a function of a movement sensor signal from the movement sensor.

23. The shock wave and/or ultrasound therapy system according to claim 22, wherein the movement sensor comprises at least one of a respiration sensor, a camera or a heart pulse sensor.

24. The shock wave and/or ultrasound therapy system according to claim 10, wherein the hexapod drive is configured to provide a first movement in a direction of a center axis of the ultrasound and/or shockwave source and concurrently a second movement laterally and or rotationally to avoid and/or remove air bubbles at an exterior surface of a cushion covering the ultrasound and/or shockwave source.

25. The shock wave and/or ultrasound therapy system according to claim 10, wherein the hexapod drive is configured to provide a spiral movement in a plane orthogonal to the center axis combined with a translation in a direction of a center axis.

26. A method of aligning an ultrasound and/or shockwave source with an X-ray system comprising steps of: a) procuring a first image with the X-ray system at a first position of the X-ray system relative to the ultrasound and/or shockwave source, the first image showing a first X-ray absorbing object and a second X-ray absorbing object arranged distantly from each other at an axis of the ultrasound and/or shockwave source, b) using the first image, calculating centers of and/or distances between the first X-ray absorbing object and the second X-ray absorbing object, and estimating an initial displacement of axes between a center axis of the ultrasound and/or shockwave source and a center axis of the X-ray system by a system controller, c) moving the ultrasound and/or shockwave source by means of a hexapod drive to compensate for the initial displacement of axes, d) procuring a second image with the X-ray system at a second position of the X-ray system, the second image showing a first X-ray absorbing object and a second X-ray absorbing object, e) using the second image, calculating the centers of and/or a distance between the first X-ray absorbing object and the second X-ray absorbing object, and estimating a displacement of axes between the center axis of the ultrasound and/or shockwave source and the center axis of the X-ray system by the system controller, and f) if the displacement of axes estimated at step e) is above a limit value, assigning a value of said displacement estimated at step e) to the initial displacement of axes and repeating a sequence from step c) through step e).

27. A method of operating an ultrasound and/or shockwave source that is suspended on a hexapod drive, comprising: moving the ultrasound and/or shockwave source by the hexapod drive towards a patient film or a patient while concurrently performing at least one lateral and/or rotational movement.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In the following, the invention will be described by way of example, without limitation of the general inventive concept, on examples of embodiments and with reference to the drawings, of which:

[0065] FIG. 1 shows an embodiment of a lithotripsy system.

[0066] FIG. 2 shows a perspective view of an ultrasound and/or shockwave source mounted to a hexapod drive.

[0067] FIG. 3 shows an embodiment of a therapy system.

[0068] FIG. 4 shows a flow diagram of a method.

[0069] FIG. 5 shows a sketch of a focal phantom.

[0070] FIGS. 6, 7, and 8 show X-ray images made with the procedure steps.

[0071] FIG. 9 shows an embodiment in two tilted positions.

[0072] FIG. 10 shows focal volume positions with tilting.

[0073] FIG. 11 shows a top view.

[0074] FIG. 12 shows a more detailed view of the coupling between ultrasound and/or shockwave source and patient.

[0075] FIG. 13 shows a spiral movement pattern of the ultrasound and/or shockwave source.

[0076] Generally, the drawings are not to scale. Like elements and components are referred to by like labels and numerals. For the simplicity of illustrations, not all elements and components depicted and labeled in one drawing are necessarily labels in another drawing even if these elements and components appear in such other drawing.

[0077] While various modifications and alternative forms, of implementation of the idea of the invention are within the scope of the invention, specific embodiments thereof are shown by way of example in the drawings and are described below in detail. It should be understood, however, that the drawings and related detailed description are not intended to limit the implementation of the idea of the invention to the particular form disclosed in this application, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION

[0078] In FIG. 1, a first embodiment of a lithotripsy system is shown. The embodiments may be implemented with any ultrasound and/or shockwave treatment system.

[0079] An extra-corporeal ultrasound and/or shockwave lithotripsy system for non-invasive treatment of stones 100 includes a patient table 110, an ultrasound and/or shockwave source 120. The ultrasound and/or shockwave source 120 is mounted to a hexapod drive 180. The hexapod drive 180 may further be held by a stand 220. The hexapod drive 180 allows fine positioning of the ultrasound and/or shockwave source 120 in multiple axes relative to the patient table 110 and therefore relative to the patient (not shown in this figure). The ultrasound and/or shockwave source 120 has a focal volume which moves together with the source. In an embodiment the distance of the focal volume to the source may be modified.

[0080] The patient table 110 is based on a stand 220 which may stand on a floor. The table 110 may be held by a positioning device 240 to move the table relative to the ultrasound and/or shockwave source 120 together with the hexapod drive 180. A movement of the patient table may be coarse positioning which may be limited to a displacement in 3 axes.

[0081] The table 110 may have a flat surface for accommodating a patient who is not shown here.

[0082] An X-ray device 290, acting as targeting device, may be provided. It may have an X-ray tube 296 opposing an X-ray detector 294, both mounted tiltable at a C-arm 292. There is a common center axis 150 on which the X-ray device and the ultrasound and/or shockwave source are aligned.

[0083] To describe the relative movement of the table 110, the X-ray device 290 and the ultrasound and/or shockwave source 120, a cartesian coordinate system 280 may be used. There is a y-axis 282, which may be a longitudinal axis through the center of the table. Furthermore, there is an x-axis 281 orthogonal to the y-axis and in the plane of the table surface. A z-axis 283 is orthogonal to the plane of the table surface and therefore orthogonal to the x-axis and the y-axis. There may also be a first rotation 284 around the x-axis, a second rotation 285 and a third rotation 286 around the z-axis. A positive rotation may be a clockwise rotation in a view along a positive axis.

[0084] A hexapod drive 180 may allow movement in all these 6 degrees of freedom. This allows for a precise adjustment of the position of the focal volume of the ultrasound and/or shockwave source 120. The patient table may be positioned for a slow and coarse adjustment in 3 degrees of translation for larger distances, but normally no rotation, whereas the hexapod drive provides a comparatively quick adjustment in 3 degrees of translation and 3 degrees of rotation. The movement distances of the table may be larger than the movement distances of the hexapod drive. The X-ray device may at least be tiltable to perform a second rotation 285 around an axis parallel to the y-axis 282. It may also be tiltable around an axis parallel to the Y axis. It may further be translated in a plane defined by the X and Y axis. This means, it may be moved on the floor which is also in the X-Y plane.

[0085] For control of the movement of the ultrasound and/or shockwave source 120 relative to the patient table 110, a control panel 400 may be provided.

[0086] FIG. 2 shows a more schematic perspective view of an ultrasound and/or shockwave source 120 mounted to a hexapod drive 180. A shock wave or ultrasound device, which may be a lithotripter 100 may include a patient table 110 and an ultrasound and/or shockwave source 120. The ultrasound and/or shockwave source 120 may be arranged below the patient table 110, such that a patient (not shown here) may be accommodated on top of the patient table. The patient table may have a longitudinal axis 112. There may be a hole or cutout in the patient table at the position of the ultrasound and/or shockwave source.

[0087] The ultrasound and/or shockwave source 120 is supported by and/or suspended on a hexapod drive 180. Basically, it is a type of parallel manipulator or parallel robot that has six linear actuators 181-186, which may be hydraulic or pneumatic jacks or electric linear actuators. These linear actuators are connected in pairs to three mounting positions 191, 192, 193 at a base 170, crossing over to three mounting positions 194, 195, 196 at the ultrasound and/or shockwave source 120. Each connection of a linear actuator to either the base or the ultrasound and/or shockwave source may include a universal joint, also called a cardan joint or a ball joint. By variation of the length of the linear actuators, the ultrasound and/or shockwave source can be moved in six degrees of freedom with respect to the base. There are three degrees of translation, parallel to at least one X-axis 281, Y-axis 282, Z-axis 283 and three degrees of tilt or rotation including a first tilt 284 around an axis parallel to X-axis 281, a second tilt 285 around an axis parallel to Y-axis 282, a third tilt 285 around an axis parallel to Z-axis 283.

[0088] Further, the ultrasound and/or shockwave source 120 may have a center axis 150.

[0089] FIG. 3 shows an embodiment in a side view. In this figure, a patient 800 is positioned on top of the patient table 110. The patient may have a kidney 810 with a kidney stone 820. An X-ray system includes an X-ray tube 294 shown below the patient and an X-ray detector 294 shown above the patient, both connected and held by a C-arm 292. Here, the X-ray system is aligned with the shock wave generator 130 such that both are on the axis 150. The X-ray system may further include a C-arm drive 293, which may be an electrical motor with a gear.

[0090] A system controller controls at least operation of the X-ray system 290, of the C-arm by means a C-arm control 430 and of the hexapod drive 180 by means of a hexapod control 420. The system controller may also control the X-ray tube 296 and may receive images from the X-ray detector 294.

[0091] Below the table 110, the ultrasound and/or shockwave source 120 is shown in a sectional view. It may have a shock wave generator 130 which may be a coil as shown herein and which is at least partially enclosed by a reflector 129. Further, the center axis 150 is marked as a dashed line. Normally, the interior of the reflector and the space between the source and the patient is filled with a liquid like water or another shockwave conducting medium. To contain the water within the volume, a coupling cushion 125 may be provided.

[0092] FIG. 4 shows a flow diagram of a method of aligning an ultrasound and/or shockwave source 120 with an X-ray system. The method utilizes a focal phantom including a first X-ray absorbing object 127 and a second X-ray absorbing object 128 arranged distant from each other at the axis of the ultrasound and/or shockwave source 120. The method including the steps of:

[0093] 510: Start

512: taking a first image with the X-ray system at a first position of the X-ray system 290 relative to the ultrasound and/or shockwave source 120, the image showing a first X-ray absorbing object 127 and a second X-ray absorbing object 128 arranged distant from each other at the axis of the ultrasound and/or shockwave source 120,

[0094] 514: processing of the first image, calculating the centers of and/or the distance between the first X-ray absorbing object 127 and the second X-ray absorbing object 128, and estimating the displacement of axes between a center axis of the ultrasound and/or shockwave source 120 and a center axis the axis of the X-ray system 290 by a system controller,

516: moving of the ultrasound and/or shockwave source 120 by means of a hexapod drive 180 to compensate (at least partially) for the displacement of axes and/or relative rotations,
518: taking a second image, the image showing the first X-ray absorbing object 127 and the second X-ray absorbing object 128,
520: processing of the second image, calculating the centers of and/or the distance between the first X-ray absorbing object 127 and the second X-ray absorbing object 128, and estimating the displacement (that may remain as a result of incomplete compensation at step 516, or that occurred anew) between the axis of the ultrasound and/or shockwave source 120 and the X-ray system 290 by a system controller,
522: checking whether the axes are aligned and there is no displacement or a displacement below a threshold between the images; If not aligned (N), go to 516, if yes (Y) go to 524

524: END

[0095] Steps 516 to 522 may be repeated multiple times until the offset between the images may be within a predefined limit or further iterations do not reduce the offset.

[0096] FIG. 5 shows a sketch of a focal phantom. An ultrasound and/or shockwave source 120 may have a first X-ray absorbing object 127 and a second X-ray absorbing object 128 distant in z-direction from each other. Both X-ray absorbing objects may be arranged symmetrical to the center axis of the source. Both X-ray absorbing objects may have different sizes and a symmetrical structure. They may be rings of different diameters. The first X-ray absorbing object 127 and a second X-ray absorbing object 128 may be removable from the ultrasound and/or shockwave source 120.

[0097] In this embodiment, a shock wave source having a centered cylindrical coil 122 within a reflector 129 is shown. The first X-ray absorbing object 127 may be at one end of the coil, where the second X-ray absorbing object 128 may be at the other side thereof. An X-ray beam 298 from X-ray tube 294 passes through the source 120 and produces images of the Y-ray absorbing objects at the detector. The axis of the ultrasound and/or shockwave source 120 may be moved by the hexapod drive 180 until the images of both X-ray absorbing objects are centered. In this case, the source 120 and the X-ray system 290 are on the same axis.

[0098] FIGS. 6 to 8 show X-ray images made with the procedure steps as explained in FIG. 4 with a focal phantom of FIG. 5. Here, FIG. 6 shows an X-ray image as made in step 512. It may show an X-ray image 551 of first X-ray absorbing object 127 and an X-ray image 552 of second X-ray absorbing object 128. If the axis of the X-ray system 290 is not aligned with the axis of the ultrasound and/or shockwave source

[0099] 120, the objects are not centered. In step 514 the center 554 of X-ray image of first X-ray absorbing object and the center 553 of X-ray image of second X-ray absorbing object are determined. FIG. 8 shows the image taken in step 518 with calculated centers from step 520, which overlap, as in this example the axis may be aligned. If the axes are still not aligned, then the centers would not be at the same position. In this case another iteration may be made.

[0100] FIG. 9 shows an embodiment in two tilted positions. At the left side, a shock wave and/or ultrasound therapy system is shown in vertical position. At the right side, the same system is shown in position tilted at an angle 840 around an axis 830 at the center of stone 820. Here the tilt axis is aligned with an axis of a stone. The image would look the same if the tilt axis is aligned with an axis of a known object or a phantom.

[0101] FIG. 10 shows focal volume positions with tilting in a side view. On the left side, a first focal volume 350 is shown around the center axis 150 in a first state. When tilting the ultrasound and/or shockwave source about an angle, this focal volume is displaced to second focal volume 360 around a tilted center axis 160. In this figure, a tilt angle of approximately 4° is shown. It can be seen that the first focal volume from a normal state and the second focal volume from a tilted state together cover roughly twice the volume at the center of the focal volumes. A kidney stone 820, which may be centered to the center axis 150 in a first state, may move by respiration movement in a direction 822 to a second position, which then may be close to the tilted center axis 160. As the tilt of the ultrasound and/or shockwave source is synchronized with the respiration movement and therefore with the movement of the kidney 810 and with the movement of the kidney stone 820, the kidney stone is always approximately at the center axis of the ultrasound and/or shockwave source and therefore within the focal volume. This ensures a high energy coupling into the stone at any time.

[0102] FIG. 11 shows a top view. As the kidneys not only move roughly parallel to the longitudinal axis 112 of the body and therefore of the patient table, but also move slightly sidewards, the ultrasound and/or shockwave source may be rotated around the center axis 150 in a first direction, such that the tilt results in movement in a first tilt direction 311 under an angle to the longitudinal axis 112. Alternatively, the ultrasound and/or shockwave source may be rotated into an opposing second position, resulting in a tilting movement in a second tilt direction 321. The focal volume covered during the tilt movement is indicated with reference number 310 for the first tilt direction 311 and with reference number 320 for the second tilt direction 321.

[0103] FIG. 12 shows a more detailed view of the coupling between ultrasound and/or shockwave source and patient. A cushion 125 covers the interior of an ultrasound and/or shockwave source filled with a liquid 126 which may include water.

[0104] The cushion 125 may include an at least partially flexible polymer material and may have an exit section 124 through which ultrasound and/or shockwaves pass to the exterior. This exit section 124 may be directly coupled to a patient 800 or indirectly via a patient film 115 to the patient. There may be a layer of coupling gel 128, also known as ultrasound gel or acoustic gel at the top of the exit section 124 to allow coupling of the ultrasound and/or shock-wave energy. There may be another layer of coupling gel 118 or another immersion media, e.g., an ultrasound gel, water between the patient film 115 and the patient 800. There may be a plurality of small air bubbles 127 enclosed in the coupling gel 128.

[0105] FIG. 13 shows a spiral movement pattern of the ultrasound and/or shockwave source. There may be a spiral movement 370 in an X-Y plane combined with a translation in Z direction towards the patient film. The movement may start at a start point 371 centered close to the center axis 150 making circles with continuously increasing radius and moving at the same time towards the patient film as indicated by arrow 372. This movement may squish air bubbles in a radial direction out of the space between the cushion and the patient film. There may also be a spiral movement in a plane orthogonal to the center axis of the ultrasound and/or shockwave source combined with a translation in a direction of the center axis. This translation may be in a direction to a patient film and/or a patient. This may be slightly different to the previous movement, as the center axis of the ultrasound and/or shockwave source must not be aligned with the Z-axis.

[0106] As understood in related art, the term “and/or”, as used in connection with a recitation involving an element A and an element B, covers embodiments having element A alone, element B alone, or elements A and B taken together.

[0107] It will be appreciated to those skilled in the art having the benefit of this disclosure that this invention is believed to provide a shock wave and/or ultrasound device. Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.

LIST OF REFERENCE NUMERALS

[0108] 100 shock wave and/or ultrasound therapy system [0109] 110 patient table [0110] 112 longitudinal axis [0111] 115 patient film [0112] 120 ultrasound and/or shockwave source [0113] 122 coil [0114] 124 exit section of cushion [0115] 125 coupling cushion [0116] 126 water [0117] 127 first X-ray absorbing object [0118] 128 second X-ray absorbing object [0119] 129 reflector [0120] 130 shock wave generator [0121] 137 air bubbles [0122] 138 coupling gel [0123] 150 center axis [0124] 160 tilted center axis [0125] 170 base [0126] 180 hexapod drive [0127] 181-186 linear actuators [0128] 191-193 mounting positions at base [0129] 194-196 mounting positions at ultrasound and/or shockwave source [0130] 220 stand [0131] 240 positioning device [0132] 280 cartesian coordinate system [0133] 281 x-axis [0134] 282 y-axis [0135] 283 z-axis [0136] 284 tilt around the x-axis [0137] 285 tilt around the y-axis [0138] 286 tilt around the z-axis [0139] 290 X-ray system [0140] 292 C-arm [0141] 293 C-arm drive [0142] 294 X-ray detector [0143] 296 X-ray tube [0144] 298 X-ray beam [0145] 310 first focal volume coverage [0146] 311 first tilt direction [0147] 320 second focal volume coverage [0148] 321 second tilt direction [0149] 350 first focal volume [0150] 360 second focal volume [0151] 370 spiral movement [0152] 371 spiral start point [0153] 372 direction of spiral movement [0154] 400 control panel [0155] 410 system controller [0156] 420 hexapod control [0157] 430 C-arm control [0158] 510-524 Method steps [0159] 551 X-ray image of first X-ray absorbing object [0160] 552 X-ray image of second X-ray absorbing object [0161] 553 center of X-ray image of second X-ray absorbing object [0162] 554 center of X-ray image of first X-ray absorbing object [0163] 800 patient [0164] 810 kidney [0165] 820 kidney stone [0166] 822 movement of kidney stone [0167] 830 tilt axis [0168] 840 tilt angle