DE102010007653A1 - Method for image assistance of medical intervention during treatment of patient, involves computing projection parameter valid for receiving position by look-up table determined in preceding calibration process - Google Patents

Abstract

The method involves mechanically coupling a reference body (42) i.e. bone screw, with a reference instrument (40) i.e. screw driver, during recording a two-dimensional (2D) calibration image. A set of 2D-X-ray images in receiving positions is captured according to a 2D-calibration image. Positions of an X-ray source (20) and an X-ray receiver (22) in the receiving position are detected relative to positions of the source and the receiver in an initial position. A projection parameter valid for the receiving position is computed by a look-up table determined in a preceding calibration process. An independent claim is also included for a device for image assistance of medical intervention using a medical instrument.

Description

The invention relates to a method and a device for image support of a medical intervention performed with a medical instrument.

When performing a medical procedure on a living being, it is known to assist the surgeon in guiding the medical instrument by means of optical image information. For this purpose, a virtual image of the instrument is displayed in the correct position in a 2D or 3D image of the treatment area of the living being obtained, for example, with an X-ray machine.

In order to enable such intraoperative navigation, also referred to as fluoronavigation, to be carried out, a 2D X-ray image may for example be continuously generated by the treatment area during the surgical procedure so that the instrument is imaged by the X-radiation together with the treatment area. However, this is disadvantageous due to the radiation exposure associated with such continuous X-irradiation for both the subject and the practitioner. To avoid such a high radiation exposure, it is therefore known to temporally decouple the X-ray imaging and the surgical procedure and to navigate the surgical instrument after the X-ray imaging camera assisted by an image of the instrument in real time in an existing, d. H. previously recorded X-ray image is displayed in the correct position. For this purpose, it is necessary to determine both the position of the instrument in a frame of reference and the position of this frame of reference relative to the image coordinates of the x-ray image.

In many cases, the X-ray apparatus used for intraoperative navigation is a so-called C-arm X-ray apparatus, in which the X-ray source and the X-ray receiver are mounted opposite one another on a C-arm pivotable about two mutually perpendicular axes in order to achieve this To be able to generate X-ray images from different projection directions.

In order to enable a precise insertion of an instrument into a 2D X-ray image or a 3D image calculated from 2D X-ray images, it is necessary to know its spatial position in a reference system related to the patient and the spatial position of the 2D X-ray images respectively belonging projection cone be known in this frame of reference. In this case, the cone of rays emanating from the origin of the X-radiation, for example the focus of an X-ray tube, within which the X-rays impinging on the receiving surface of the X-ray receiver propagate is referred to as the projection cone. Ideally, the position of this projection cone is already known when the spatial position of the image plane, i. H. the entry surface of the X-ray receiver is fixed, so that it should be sufficient to determine the position of the X-ray receiver in the reference system, in which the position of the instrument is detected. In practice, however, it has turned out that merely the determination of the position of the X-ray receiver is not sufficient to reliably fix the projection cone, since this is not always the same relative position to the X-ray receiver due to the unavoidable deflection of the C-arm, which depends on the position of the X-ray axis having.

In the DE 199 17 867 A1 Therefore, it is proposed to arrange a reference structure on the X-ray receiver which, in addition to optical position markers for navigation with a position detection device, also contains X-ray markers which lie in the beam path of the X-radiation and are imaged in the X-ray image. The position of the X-ray markers visible in the X-ray image can be used both to calculate the relative position of the projection cone and also to measure any distortions which occur, in particular, when X-ray image intensifiers are used. The measurement of the distortions must be carried out for each recorded 2D X-ray image in order to then be able to eliminate them.

However, the X-ray markers visible in the X-ray image have the disadvantage that they shade a part of the X-ray image and in this way inevitably go hand in hand with a loss of information. This loss of information can not be completely avoided even if these X-ray markers are eliminated from the X-ray image by methods of digital image processing. In addition, the space freely accessible between the X-ray receiver and the X-ray source is reduced by the attachment of X-ray markers arranged in front of the receiving surface.

Alternatively, it is from the DE 103 60 025 A1 in the case of 3D navigation with a C-arm X-ray apparatus, it is possible to determine the position of the X-ray receiver with a position detection device, each position of the X-ray receiver having a determination of the position of the projection cone and correctly taking into account the deflection of the C-arm in a previous calibration Projection matrix is assigned. As a result of this measure, the use of X-ray markers is no longer necessary and, accordingly, the workflow is improved. To enable a high accuracy of the navigation, however, a complex calibration for different scanning paths is required, which must be repeated at regular intervals.

The invention is based on the object of specifying a method for image support of a medical instrument performed with a medical instrument, which is simplified compared to the known methods. In addition, the invention has for its object to provide a working device according to this method.

With regard to the method, the object is achieved according to the invention by a method having the features of claim 1. According to these features, in a method with a positionable in different recording positions X-ray device in a basic position at least a 2D calibration image is taken from a treatment area, while within or in a vicinity of the treatment area, a reference body provided with position markers is introduced, which is mechanically coupled during recording of the 2D calibration image with a reference instrument in a spatially unique manner. The reference instrument is provided with X-ray markers whose positions in the 2D calibration image are used to relate a reference system associated with the reference body to a reference system of the X-ray apparatus. After the recording of the at least one 2D calibration image, a plurality of 2D X-ray images are recorded in recording positions which are different from the basic position, and it is the respective recording position of X-ray source and X-ray receiver of the X-ray relative to the position of Röntenquelle and X-ray receiver in the basic position is detected, and it is calculated for the respective recording position projection parameters using a determined in a previous calibration look-up table.

Since reference body and reference instrument in a spatially unique, d. H. With respect to all 6 degrees of freedom with sufficient accuracy defined manner are mechanically coupled, it is easily possible to use a reference frame and thus the patient associated reference system with a single 2D Kalbrierbild directly in spatial relation to the X-ray generated by the X-ray machine in the different recording positions X-ray images , without a complex position detection of X-ray source and X-ray receiver is required, since it is sufficient to detect the easily detectable with simple encoders relative position changes of X-ray source and X-ray receiver between the individual recording positions. For this purpose, only the projection parameters or projection matrices that are valid for the respective recording positions in a reference system of the X-ray apparatus need to be determined in a previous calibration and stored in a look-up table.

With regard to the device, the object is achieved according to the invention with a device having the features of claim 7. The advantages of this device correspond mutatis mutandis to the method according to claim 1 advantages.

Advantageous embodiments of the method and the device are given in the claims 2 to 6 and 8 to 12.

1 a device according to the invention with an X-ray device in a starting position,

2 a reference instrument particularly suitable for carrying out the method according to the invention with a reference body arranged thereon.

3 a situation in which the reference body arranged on the reference instrument is fixed to a body part of the patient,

4 the X-ray device according to 1 in a different recording position from the starting position.

According to 1 A device according to the invention comprises a mobile X-ray device 2 in which on a equipment cart 4 height adjustable a bearing part 8th for a C-arm 10 is arranged. The bearing part 8th is pivotable about an axis oriented parallel to the plane of the drawing 12 (Angulation axis) stored. In the warehouse part 8th is the C-arm 10 pivotable about an axis perpendicular to the plane of the drawing 14 (Orbital axis) out. The possible by this storage pivotal movements φ and θ are by the double arrows 15 respectively. 16 illustrated. The C-arm 10 is also in the direction x of the angulation axis 12 and height h adjustable on equipment cart 4 stored as indicated by the double arrows 17 respectively. 18 is illustrated. The displacement x, the height h, the angulation angle φ and the orbital angle θ, ie the stationary trolley 4 possible position changes of the C-arm 10 be with a schematically illustrated position encoder arrangement 19a detected relative to a basic or starting position. On the equipment cart 4 is also an optical position sensor 19b arranged with which a relative displacement of the equipment cart 4 can be detected.

At the C-bow 10 are opposite each other an X-ray source 20 , usually one X-ray tube, and an X-ray receiver 22 , preferably a distortion-free digital X-ray detector with a flat receiving surface arranged.

In the projection cone 24 that from the X-ray source 20 emitted X-rays, ie the cone of rays, whose tip through the approximately point-like X-ray source 20 - When using an X-ray tube whose focus - and its base by the receiving surface of the X-ray receiver 22 is formed on a patient table 25 a patient P to whom a picture-assisted procedure is to be performed.

In a previous calibration, when the equipment cart is stationary 4 for different recording positions of the C-arm 10 - Angulation angle φ and orbital angle θ and, if required due to possible mechanical deflection, displacement x, height h, - the respectively valid projection parameters in one on the X-ray machine 2 determined reference system and stored in a look-up table. With the help of the position encoder arrangement 19a Thus, when the x-ray images used for image-assisted surgery are acquired, the x, height h, angulation angle .phi., and orbital angle .theta. can be used for X-ray imaging in the respective current positions of the C-arm 10 valid projection parameters using the look-up table.

In the figure is the C-arm 10 exemplified in a customary in the 3D navigation starting position in the X-ray source 20 and X-ray receiver 22 facing each other in a horizontal plane. In a basic position, which in the example corresponds to this starting position, P is on or in the patient with a reference instrument 40 a reference body 42 brought into an end position in which he remains during the procedure. The reference instrument 40 engages to attach the reference body 42 on or in the patient P in this one such that between reference body 42 and reference instrument 40 there is a firm and unambiguous geometric relationship. In other words, the orientation and location of the reference instrument 40 sets the orientation and position of the reference body 42 clearly stated. In this basic position are the position of the projection cone 24 and the position of the patient P and thus the position of the reference body 42 or the reference instrument 40 set so that the reference instrument 40 at least partially within the projection cone associated with this home position 24 located. In this basic position, a fluoroscopic 2D calibration image is taken when the reference body 42 with this intervening reference instrument 40 in an end position in which it remains during a subsequent procedure.

According to 2 is the reference instrument 40 , in the example a screwdriver, with X-ray markers impermeable to X-ray radiation and reproduced in the 2D calibration image 44 provided on the reference instrument 40 non-planner, that is, not arranged in a single, common plane lying, and with their positions in the 2D calibration image due to the projection parameters known for the basic position, the position and position of the reference instrument 40 an X-ray machine 2 assigned reference system is determined. On the reference body 42 , in the example a bone screw, are also position markers 46 arranged, whose positions in the room with an in 1 schematically illustrated position detection system 50 can be determined. In the embodiment, an electromagnetic position detection system 50 with a transmitter comprising several transmitter coils 52 provided as a position marker 46 on the reference body 42 attached receiver coils are assigned. Because the spatial relationship between the x-ray markers 44 the reference instrument and the position markers 46 of the reference body is known, can in this way a the reference body 42 assigned and with the position detection system 50 correlated reference system in relation to the reference system of the x-ray apparatus 2 be set.

Instead of an electromagnetic position detection system, it is also possible in principle to use position detection devices which operate according to other methods, for example markerless optical tracking methods or tracking methods with active, light-emitting optical position markers, if direct visual contact between the position markers 46 of the reference body 42 and the position detection system is possible.

3 shows the body part located in or on a patient P and suitable as a reference to an object or treatment area G to be treated 60 , in the example a bone, in a final position fixed reference body 42 with reference instrument still in operation 40 , At least that with the x-ray markers 44 provided part of the reference instrument 40 is inside the projection cone 24 within which the X-ray propagates when taking the 2D calibration image, so that the on the reference instrument 40 attached x-ray marker 44 are visible in the 2D calibration image. When taking the 2D calibration image, that of the optical position sensor 19b detected position of the equipment cart 4 saved or reset to zero.

By registering the reference instrument in this way 40 in the reference system of the X-ray machine 2 is due to the clear spatial relationship between the reference instrument 40 and the reference body fixed to the patient P 42 also its location and position in this reference system known. By detecting the position and position of the reference body 42 with its assigned position detection system 50 is also a unique relationship between the reference system of the X-ray machine 2 and the reference system of the position detection system 50 and thus also produced with a patient reference system.

After taking the 2D calibration image, the reference instrument becomes 40 and further 2D x-ray images are taken from different recording positions, one of which is in 4 is shown, in which the X-ray source 20 below the patient table 25 located. The projection parameters valid in these recording positions and their assignment to the patient can then be determined by the position encoder arrangement 19a calculated from the look-up table determined in the previous calibration and in the event that the equipment cart 4 in addition, between the x-rays is shifted, on the basis of the optical position sensor 19b additionally be corrected.

For a subsequent intervention with a medical instrument 70 can then use the x-ray machine 2 are removed, since the spatial relationship between the patient reference system and the recorded 2D X-ray images and the resulting if calculated 3D images is known, so that only a registration of the medical instrument 70 is required. If this also with the position detection system 50 detectable position markers 46 , is provided in the example transmitting coils, whose position is known directly in the patient reference system.

The invention is illustrated by way of example with reference to a C-arm X-ray apparatus. In principle, the invention can also be used in other X-ray devices in which the position of X-ray source and X-ray receiver is spatially variable and whose relative position change between the individual recording positions is detected with corresponding position sensors. Accordingly, it is also possible in particular to use X-ray devices, in which X-ray receiver and X-ray source can be positioned independently of each other freely in space, d. H. are not mechanically positively coupled in a manner as is the case with a C-arm X-ray apparatus. Thus, for example, X-ray source and X-ray receiver can each be arranged on an articulated arm robot on independent and freely movable consoles.

LIST OF REFERENCE NUMBERS

1

shift

2

X-ray machine

4

trolley

8th

bearing part

10

C-arm

12

Angulation axis

14

orbital axis

15, 16, 17, 18

double arrow

19a

Position sensor device

19b

locator

20

X-ray source

22

X-ray receiver

24

projection cone

25

Patient table

40

reference tool

42

reference body

44

X-ray markers

46

position marker

50

Position detection system

52

transmitter

60

body part

70

instrument

H

height

x

shift

P

patient

G

area

φ

Angulation angle

θ

orbital angular

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19917867 A1 [0006]
• DE 10360025 A1 [0008]

Claims (13)

Method for image support of a medical instrument ( 70 ) carried out by a treatment area (G) with a positionable in different receiving positions X-ray device ( 2 ) is recorded in a basic position, a 2D calibration image, while within or in an environment of the treatment area (G) with a position markers ( 46 ) provided reference body ( 42 ), which during the acquisition of the 2D calibration image with a reference instrument ( 40 ) is mechanically coupled in a spatially unique manner, which with X-ray markers ( 44 ), with whose positions in the 2D calibration image a reference body ( 42 ) associated reference system in relation to a reference system of the X-ray device ( 2 ) is set, wherein after the recording of the at least one 2D calibration image, a plurality of 2D X-ray images are recorded in recording positions which are different from the basic position, and wherein each of the recording position belonging to X-ray source ( 20 ) and X-ray receiver ( 22 ) of the X-ray device ( 2 ) relative to the location of x-ray source ( 20 ) and X-ray receiver ( 22 ) is detected in the basic position and the projection parameters valid for the respective recording position are calculated with the aid of a look-up table determined in a preceding calibration. The method of claim 1, wherein a bone screw is used as the reference body. The method of claim 2, wherein the reference instrument is a screwdriver for screwing the bone screw in a bone located in the treatment area. Method according to one of the preceding claims, in which an electromagnetic position detection system is provided for detecting the position of the position marks and thus the position of the reference body. Method according to one of the preceding claims, in which the x-ray markers ( 44 ) on the reference instrument ( 40 ) are not arranged in a common plane. Method according to one of the preceding claims, in which a C-arm X-ray device is used for image support. Device for image support of a medical procedure performed with a medical instrument, with an X-ray device positionable in different receiving positions ( 2 ) for taking 2D X-ray images, one in a treatment area ( 6 ) fixable with position markers ( 46 ) provided reference body ( 42 ), one with x-ray markers ( 44 ) ( 40 ) is mechanically coupled in a spatially unique manner, a position detection system ( 50 ) for detecting the position of the reference body ( 42 ) in the room, as well as with an X-ray machine ( 2 ) arranged position encoder arrangement ( 19a ) for detecting the relative position changes of X-ray source ( 20 ) and X-ray receiver ( 22 ) between the different shooting positions. Device according to claim 7, wherein the reference body is a bone screw. Device according to claim 8, wherein the reference instrument is a screwdriver for screwing the bone screw in a bone located in the treatment area. Device according to one of claims 7 to 9, wherein for detecting the position of the position marker and thus the position of the reference body, an electromagnetic position detection system is provided. Device according to one of Claims 7 to 10, in which a C-arm X-ray device is used for image support. Device according to one of Claims 7 to 11, in which the x-ray markers ( 44 ) on the reference instrument ( 40 ) are not arranged in a common plane. Reference Instrument ( 40 ) with X-ray markers ( 44 ) and reference body ( 42 ) with position markers ( 46 ) for carrying out a method according to one of claims 1 to 6.

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