DE102011114333B4 - A method of registering an X-ray volume with a position sensing system using a registration phantom - Google Patents

Abstract

A method for registering a C-arm X-ray device (1) with a position detection system (5) using a Registrierungsphantoms (2), which in a defined spatial relationship to each other an arrangement (10) of at least three X-ray marks (11, 12, 13) and a Arrangement (20) of navigation marks (21, 22, 23), by means of which the positions of the X-ray marks (11, 12, 13) in a coordinate system of the position detection system (5) can be detected, wherein the C-arm X-ray device (1) a X-ray source (4), an X-ray receiver (3) and a computing unit (32) and is equipped to take a projection scans of a scan and reconstruct an X-ray volume and is equipped to the position of the X-ray receiver (3) with respect to the position detection system (5) in at least one registration position of the C-arm X-ray apparatus (1), wherein the registration phantom (2) is located in two different spatial locations ientierungen the Registrationsphantoms (2) for a first and one of this different second registration position of the C-arm X-ray device (1) each have an X-ray projection of the X-ray marks (11, 12, 13) with the C-arm X-ray device (1) and a position determination the arrangement (20) of the navigation marks (21, 22, 23) of the registration phantom (2) by means of the position detection system (5) is made and in at least one of the two registration positions of the C-arm X-ray device (1) the position of the X-ray receiver (3) determined in a coordinate system of the position detection system (5) and stored in a computer memory of the computing unit (32) as NaviTReg1, characterized by the method steps 1) the position of the projections of the arrangement (10) of X-ray marks (11, 12, 13) in the projection photographs is automatically determined and stored in a computer memory of the arithmetic unit (32), 2) in an identification process step is in each Projection image of an array (10) of X-ray marks (11, 12, 13) each image of a single X-ray mark (11, 12, 13) that X-ray mark (11, 12, 13) associated with the respective image of the X-ray mark (11, 12, 13 3) for each of the two projection images, the projection matrices P1Navi and P2Navi are determined by means of the point correspondence method from the coordinates of the X-ray marks (11, 12, 13) in the coordinate system of the position detection system and buffered in a computer memory of the arithmetic unit (32), 4) in the scan volume of the C-arm X-ray apparatus (1), at least three spatial points in the coordinate system of the C-arm X-ray apparatus (1) are arbitrarily selected, at which virtual dot-shaped X-ray marks are assumed; with the aid of the known projection matrices P1Vol and P2Vol assigned to the C-arm X-ray apparatus (1), the image coordinates of the virtual X-ray marks are calculated for the first and the second registration position of the C-arm X-ray apparatus (1).

Description

A method of registering an X-ray volume with a position sensing system using a registration phantom.

Medical interventions on living objects are increasingly carried out by means of navigation support. This is understood as meaning the guidance of an instrument supported by a position detection system relative to a tissue area of the object being treated. Of particular interest is the navigation in areas that elude a visual control of the surgeon, for example, because the instrument has been introduced into the interior of the object. For this purpose, the guidance of the instrument, for example a drilling tool, is made in a virtual X-ray volume recorded, for example, by a C-arm X-ray apparatus, which was determined by means of an imaging method before or during the operation. In order to ensure navigation with high accuracy, the coordinate system of the X-ray volume is registered in a registration process with that of the position detection system, d. H. brought to cover.

During registration, for example, a Registrierungsphantom is used, the x-ray-positive marks, hereinafter referred to as "X-ray marks" and detectable by the position detection system marks, hereinafter referred to as "navigation marks" in a fixed spatial relationship to each other. From the German patent application DE 10 2006 051 782 A1 The applicant is aware of a method for calibrating an X-ray diagnostic device, in which the deviations of the projection geometry during scanning of a punctiform X-ray mark arranged in a virtual scan center are determined by the projection geometry determined according to the kinematic model of the X-ray diagnostic device. The deviations are characterized by a shift vector in the plane of the input window of the X-ray receiver for different orientations and stored in a computing unit. With a second phantom having x-ray positive structures detectable by a position detection system, an x-ray volume of 2D projections is reconstructed taking into account the displacement vectors and the x-ray volume is shifted by another displacement vector for which the x-ray volume of the phantom optimally matches that determined by the position detection system Volume matches.

From the publication US 2011/0071389 A1 is a method of registering an object volume with an x-ray volume of the object using a phantom releasably connected to the object having in a known spatial relationship x-ray positive marks and marks detectable by a position detection system. The X-ray volume is reconstructed from a number of 2D X-ray projections, wherein in at least one of the 2D projections a part of the X-ray-positive marks is imaged, determines their position in the 2D projection and the position of the detectable by the position detection system marks in the coordinate system of the position detection system is determined ,

From the DE 102 02 091 A1 For example, an apparatus and method for determining a coordinate transformation using a phantom is known in which x-ray positive marks and marks detectable by a position detection system are arranged in a fixed spatial relationship with each other. In a scan to produce 2D X-ray projection images, the coordinates of the X-ray positive marks in the reconstructed 3D volume are determined and transmitted to the position detection and navigation system for comparison.

The US Pat. No. 5,835,563 A relates to an X-ray phantom that remains firmly attached to the patient during an X-ray examination and improves the accuracy of digital subtraction angiography (DAS) imaging.

The object of the invention is to provide a method for registering the coordinate system of the X-ray volume of a C-arm X-ray device with the coordinate system of the position detection system, which is kostenGüstig feasible, the registration after a spatial displacement of the C-arm X-ray device produced again is.

The object of the invention is achieved in that the registration takes place using a Registrierungsphantoms, as is commonly used in the registration of X-ray 2D navigation and which preferably point-like or spherical X-ray and detectable by a position detection system navigation marks in a defined spatial relationship to each other having. An X-ray projection with the C-arm X-ray apparatus with different acquisition geometries is recorded in each case from the registration phantom positioned in two different spatial orientations and a position determination of the registration phantom is carried out by means of the position detection system. The position of the projections of the X-ray marks in the projection photographs is automatically determined and assigned to the respective X-ray marks of the registration phantom in an identification step. The location of the X-ray receiver is determined and stored at least in a registration position of the C-arm X-ray machine.

For each of the two projection images, a camera calibration procedure based on point correspondences, such as, for example, RY Tsai, "A Versatile Camera Calibration Technique for High-Accuracy 3D Machine Vision Metrology Using Off-theshelf TV Cameras and Lenses", IEEE Journal of Robotics and automation, Vol. RA-3, NO. 4, August 1987, or according to the calculation rules given in Chapter 1.6 "Camera Calibration" from the publication of Mubarak Shah: "Fundamentals of Coputer Vision", University of Central Florida, Orlando, December 7, 1997, reference http: // /www.cs.ucf.edu/courses/cap6411/book.pdf from the coordinates of the X-ray marks in the coordinate system of the position detection system determines the projection matrix, so that after the camera calibration the two projection _matrices P _1Navi and P _2Navi are present, which are _{temporarily stored} in a _{computer memory} ,

In the scan volume of the C-arm X-ray apparatus, which represents a volume arranged around a scan center in the coordinate system of the C-arm X-ray apparatus and for which a volume reconstruction can be performed after a scan, at least three spatial points in the coordinate system of the C-arm X-ray apparatus become arbitrary chosen where virtual point-like X-ray marks are assumed. Using the known projection matrices P1Vol and P2Vol for the first and second registration positions of the C-arm X-ray apparatus, the image coordinates of the virtual X-ray marks in the coordinate system of the C-arm X-ray apparatus are calculated.

In a further method step, the associated families of the projection straight lines in the coordinate system of the position detection system are determined by means of backprojections using the projection matrices P1Navi and P2Navi from the projection images of the virtual X-ray marks. For each virtual X-ray mark, a projection straight line containing the virtual X-ray mark is obtained for each projection image. The intersection of the projection line for a virtual X-ray mark coincides with the location of the respective virtual X-ray mark in the coordinate system of the position detection system. Thus, the coordinates of the virtual X-ray marks are determined both in the coordinate system of the C-arm X-ray machine and in the coordinate system of the position detection system.

As a result of the registration process, a coordinate transformation VolTNavi between the coordinate system "Vol" of the C-arm X-ray machine and the coordinate system "Navi" of the position detection system is determined. For this purpose, a known calculation method is used, for example the matching method according to Umeyama (Umeyama, S .: "Least-squares estimation of transformation parameters between two point patterns" in IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. 13 Issue 4, April 1991). pages 376-380).

For the coordinate transformation VolTNavi, at least in the first registration position "Reg1" of the C-arm X-ray device, the position of the X-ray receiver in the coordinate system of the position detection system is determined, namely NaviTReg1 and instead of VolTNavi the shift-invariant matrix VolTReg1 = VolTNavi · NaviTReg1 is stored.

In a later use of the C-arm X-ray apparatus, after this has been relocated in the meantime, the position of the X-ray receiver in the first registration position Reg1 in the displaced coordinate system Navi 'of the position detection system is determined, namely Reg1TNavi' and a coordinate transformation VolTNavi '= VolTReg1 * Reg1TNavi' determined and used for navigation.

The method according to the invention and in particular the method steps for recording projection images and for determining the position using a registration phantom are explained in more detail with reference to the figures.

The pictures 1 to 4 each have three schematic illustrations of a C-arm X-ray machine ( 1 ) with an X-ray receiver ( 3 ) and an X-ray source ( 4 ) on. In all illustrations is a registration phantom ( 2 ) with an arrangement ( 10 ) of X-ray marks ( 11 . 12 . 13 ) and an arrangement ( 20 ) of navigation marks ( 21 . 22 . 23 ). The X-ray marks, of which only 3 X-ray marks ( 11 . 12 . 13 ) are in known spatial relationship to the three navigation marks shown schematically ( 21 . 22 , m 23 ), whose position with respect to a coordinate system of the position detection system (hereinafter referred to as "Navi") ( 5 ) is detectable. The C-arm X-ray apparatus has multiple adjustment possibilities, wherein for a number of C-arm positions the projection matrices are known in a C-arm-fixed coordinate system. This series of C-arm positions or a portion thereof forms the positions of a scan that can be used to reconstruct a 3D reconstruction of an X-ray volume. The C-arm fixed coordinate system is hereinafter referred to as "Vol".

• – für eine in den mit a) bezeichneten Figuren erste Registrierstellung des C-Bogen-Röntgengeräts (1) wird eine erste Projektionsaufnahme der Anordnung (10) der Röntgenmarken des Registrierphantoms aufgenommen,
• – für eine in den mit b) bezeichneten Figuren zweite Registrierstellung des C-Bogen-Röntgengeräts (1) wird eine zweite Projektionsaufnahme der gegenüber der Anordnung aus den mit a) bezeichneten Figuren verlagerte Anordnung (10) der Röntgenmarken des Registrierphantoms (2) aufgenommen,
• – für die beiden Anordnungen der den mit a) und b) bezeichneten Figuren wird jeweils die Lage der Anordnung (20) der schematisch dargestellten drei Navigationsmarken (21, 22, 23) mit dem Lageerfassungssystem (5) erfaßt und zusätzlich für eine der beiden Registrierstellungen des C-Bogen-Röntgengeräts (1) die Lage des Röntgenstrahlenempfängers (3) mittels des Lageerfassungssystems (5) bestimmt.
• – Nach Abschluß der Messungen zur Registrierung wird wenigstens die Anordnung (10) der Röntgenmarken (11, 12, 13) vom C-Bogen-Röntgengerät (1) entfernt. Die Konfiguration des C-Bogen-Röntgengeräts (1) nach Entfernung der Röntgenmarken (11, 12, 13) ist in den mit c) bezeichneten Figuren dargestellt. Diese Konfiguration wird zur nachfolgenden Anfertigung eines Scans eines nicht gezeigten Untersuchungsobjekts verwendet.

The pictures 1 to 4 schematically indicate four variants of C-arm X-ray device and Registrierungsphantom with which

• For a first registration position of the C-arm X-ray apparatus in the figures marked with a) ( 1 ) is a first projection image of the arrangement ( 10 ) of the X-ray marks of the registration phantom,
• For a second registration position of the C-arm X-ray apparatus in the figures designated b) 1 ) is a second projection image of the arrangement relative to the arrangement of the figures designated with a) ( 10 ) of the X-ray marks of the registration phantom ( 2 ),
• For the two arrangements of the figures denoted by a) and b), the position of the arrangement ( 20 ) of the schematically illustrated three navigation marks ( 21 . 22 . 23 ) with the position detection system ( 5 ) and additionally for one of the two registration positions of the C-arm X-ray apparatus ( 1 ) the position of the X-ray receiver ( 3 ) by means of the position detection system ( 5 ) certainly.
• - After completion of the measurements for registration at least the arrangement ( 10 ) of X-ray marks ( 11 . 12 . 13 ) from the C-arm X-ray machine ( 1 ) away. The configuration of the C-arm X-ray unit ( 1 ) after removal of the X-ray marks ( 11 . 12 . 13 ) is shown in the figures denoted by c). This configuration is used to subsequently make a scan of an examination subject, not shown.

In 1 is the use of a registration phantom ( 2 ), in which the arrangement ( 10 ) of X-ray marks ( 11 . 12 . 13 ) of the arrangement ( 20 ) of the navigation marks is designed detachable. Which the arrangements ( 10 ) and ( 20 ) carrying parts of the Registrierungsphantoms are by means of coupling parts ( 40 . 41 ) can be coupled reproducibly. After completion of the measurements for registration remains in 1c the order ( 20 ) of the navigation marks on the X-ray receiver ( 3 ). Is the C-arm X-ray machine ( 1 ) in the room, the registration is made by measuring the position of the displaced X-ray receiver ( 3 ), for example, in the registration position of 1a and restored by a coordinate transformation in the position detection system.

In 2 is the use of a registration phantom ( 2 ) with an arrangement ( 10 ) of X-ray marks ( 11 . 12 . 13 ) and an arrangement ( 20 ) provided by navigation marks which are not in contact with the C-arm X-ray machine ( 1 For example, held by hand in different positions in 2a and 2 B be positioned. In addition, the X-ray receiver ( 3 ) with an arrangement ( 20 ' ) equipped by navigation marks, which are either integrated in the X-ray receiver or held at this reproducible and detachable. After completion of the measurements for registration remains in 2c the order ( 20 ' ) of the navigation marks on the X-ray receiver ( 3 ).

Is the C-arm X-ray machine ( 1 ) in the room, the registration is made by measuring the position of the displaced X-ray receiver ( 3 ), for example, in the registration position of 2a and restored by a coordinate transformation in the position detection system.

In 3 is the use of a registration phantom ( 2 ) with an arrangement ( 10 ) of X-ray marks ( 11 . 12 . 13 ) and an arrangement ( 20 ) provided by navigation marks on the C-arm X-ray machine ( 1 ) is attached in any orientation, wherein in the attached state, the arrangement ( 10 ) of X-ray marks ( 11 . 12 . 13 ) on the X-ray receiver ( 3 ) are mapped. In addition, the X-ray receiver ( 3 ) with an arrangement ( 20 ' ) equipped by navigation marks, which are either integrated in the X-ray receiver or held at this reproducible and detachable. After completion of the measurements for registration remains in 3c the order ( 20 ' ) of the navigation marks on the X-ray receiver ( 3 ). Is the C-arm X-ray machine ( 1 ) in the room, the registration is made by measuring the position of the displaced X-ray receiver ( 3 ), for example, in the registration position of 3a and restored by a coordinate transformation in the position detection system.

In 4 is the use of a registration phantom ( 2 ) with an arrangement ( 10 ) of X-ray marks ( 11 . 12 . 13 ) and an arrangement ( 20 ) provided by navigation marks, which at the X-ray receiver ( 3 ) of the C-arm X-ray apparatus ( 1 ) is releasably secured in a defined orientation. For this purpose, at the X-ray receiver ( 3 ) and on the registration phantom ( 2 ) Coupling parts ( 40 . 451 ) intended. Upon completion of the measurements for registration will be in 4c the registration phantom ( 2 ) from the X-ray receiver ( 3 ) away. Is the C-arm X-ray machine ( 1 ) is displaced in space, the registration phantom ( 2 ) to the C-arm X-ray machine ( 1 ) in the registration position 4a to the X-ray receiver ( 3 ) by means of the coupling parts ( 40 . 41 ) grown. Registration is done by measuring the position of navigation marks ( 21 . 22 . 23 ) at the displaced X-ray receiver ( 3 ) in the registration position of 4a and by a coordinate transformation in the position detection system ( 5 ), without the use of X-radiation.

• 1) Von dem Registrierphantom (2) wird in zwei unterschiedlichen räumlichen Orientierungen des Registrierphantoms (2) für zwei unterschiedliche Registrierstellungen des C-Bogen-Röntgengeräts (1) jeweils eine Röntgenprojektion der Röntgenmarken (11, 12, 13) mit dem C-Bogen-Röntgengerät (1) und eine Lagebestimmung der Anordnung (20) der Navigationsmarken (21, 22, 23) des Registrierphantoms (2) mittels des Lageerfassungssystems (5) angefertigt.
• 2) In wenigstens einer der beiden Registrierstellungen des C-Bogen-Röntgengeräts (1) wird die Lage des Röntgenstrahlenempfängers (3) in einem Koordinatensystem des Lageerfassungssystems (5) ermittelt und in einem Rechenspeicher der Recheneinheit (32) als NaviTReg1 abgespeichert.
• 3) Die Lage der Projektionen der Anordnung (10) von Röntgenmarken (11, 12, 13) in den Projektionsaufnahmen wird automatisch ermittelt und in einem Rechenspeicher der Recheneinheit (32) abgespeichert.
• 4) In einem Identifizierungsverfahrensschritt wird in jedem Projektionsbild einer Anordnung (10) von Röntgenmarken (11, 12, 13) jedes Bild einer einzelnen Röntgenmarke (11, 12, 13) derjenigen Röntgenmarke (11, 12, 13) zugeordnet, die das jeweilige Bild der Röntgenmarke (11, 12, 13) verursacht hat.
• 5) Für jede der beiden Projektionsaufnahmen werden mittels des Punktekorrespondenzverfahrens aus den Koordinaten der Röntgenmarken (11, 12, 13) im Koordinatensystem des Lageerfassungssystems die Projektionsmatrizen P1Navi und P2Navi bestimmt und in einem Rechenspeicher der Recheneinheit (32) zwischengespeichert.
• 6) Im Scanvolumen des C-Bogen-Röntgengeräts (1), das sich dadurch auszeichnet, daß es in allen Röntgenprojektionsaufnahmen eines Scans vollständig abgebildet wird, werden wenigstens drei Raumpunkte im Koordinatensystem des C-Bogen-Röntgengeräts (1) beliebig gewählt, an denen virtuelle punktförmige Röntgenmarken angenommen werden. Mit Hilfe der dem C-Bogen-Röntgengerät (1) zugeordneten, bekannten Projektionsmatrizen P1Vol und P2Vol werden für die beiden Registrierstellungen des C-Bogen-Röntgengeräts (1) die Bildkoordinaten der virtuellen Röntgenmarken berechnet.
• 7) Mittels einer Rückprojektion unter Verwendung der Projektionsmatrizen P1Navi und P2Navi werden aus den Projektionsbildern der virtuellen Röntgenmarken die Koordinaten der jeweiligen virtuellen Röntgenmarken im Koordinatensystem des Lageerfassungssystem (1) ermittelt.
• 8) Aus den Koordinaten der virtuellen Röntgenmarken im Koordinatensystem Navi des Lageerfassungssystems (2) und im Koordinatensystem Vol des C-Bogen-Röntgengeräts (1) wird die Koordinatentransformation VolTNavi ermittelt.
• 9) Mit der in Verfahrensschritt 2) ermittelten und abgespeicherten Koordinatentransformation NaviTReg1 wird die verschiebeinvariante Matrix VolTReg1 = VolTNavi·NaviTReg1 errechnet und in einem Rechenspeicher der Recheneinheit (32) abgespeichert.
• 10) Bei einer späteren Verwendung des C-Bogen-Röntgengeräts (1), nachdem dieses zwischenzeitlich verlagert worden war, wird die Position des Röntgenstrahlenempfängers (3) in der Registrierstellung Reg1 in dem verlagerten Koordinatensystem Navi' des Lageerfassungssystem (5) ermittelt, nämlich Reg1TNavi' und eine Koordinatentransformation VolTVavi' = VolTReg1·Reg1TNavi' ermittelt und für die Navigation mit dem verlagerten C-Bogen-Röntgengerät (1) verwendet.

The method for registering a C-arm X-ray apparatus suitable for 3D reconstruction of an X-ray volume ( 1 ) with a position detection system ( 5 ) using a Registrierungsphantoms ( 2 ), which in a defined spatial relationship to each other an arrangement ( 10 ) of at least 3 x-ray marks ( 11 . 12 . 13 ) and an arrangement ( 20 ) of navigation marks ( 21 . 22 . 23 ), by means of which the positions of the X-ray marks ( 11 . 12 . 13 ) in a coordinate system of the position detection system ( 5 ) are detectable, wherein the C-arm X-ray device ( 1 ) an X-ray source ( 4 ) and an X-ray receiver ( 3 ) and is equipped to detect the position of the X-ray receiver ( 3 ) with regard to the position-finding system ( 5 ) in at least one registration position of the C-arm X-ray device ( 1 ) is determined by the sequence of the following process steps:

• 1) From the registration phantom ( 2 ) is displayed in two different spatial orientations of the registration phantom ( 2 ) for two different registration positions of the C-arm X-ray device ( 1 ) an X-ray projection of the X-ray marks ( 11 . 12 . 13 ) with the C-arm X-ray device ( 1 ) and an orientation of the arrangement ( 20 ) of navigation marks ( 21 . 22 . 23 ) of the registration phantom ( 2 ) by means of the position detection system ( 5 ) prepared.
• 2) In at least one of the two registration positions of the C-arm X-ray apparatus ( 1 ) the position of the X-ray receiver ( 3 ) in a coordinate system of the position detection system ( 5 ) and stored in a computer memory of the arithmetic unit ( 32 ) saved as NaviTReg1.
• 3) The location of the projections of the arrangement ( 10 ) of X-ray marks ( 11 . 12 . 13 ) in the projection images is determined automatically and stored in a computer memory of the computing unit ( 32 ) stored.
• 4) In an identification process step, in each projection image of an arrangement ( 10 ) of X-ray marks ( 11 . 12 . 13 ) each image of a single X-ray mark ( 11 . 12 . 13 ) of the X-ray mark ( 11 . 12 . 13 ) associated with the respective image of the X-ray mark ( 11 . 12 . 13 ).
• 5) For each of the two projection photographs, the coordinates of the X-ray marks are determined by means of the point correspondence method ( 11 . 12 . 13 ) in the coordinate system of the position detection system, the projection matrices P1Navi and P2Navi determined and in a computing memory of the arithmetic unit ( 32 ) are cached.
• 6) In the scan volume of the C-arm X-ray device ( 1 ), which is characterized in that it is completely imaged in all the x-ray projection images of a scan, at least three spatial points in the coordinate system of the C-arm x-ray apparatus ( 1 ) are chosen arbitrarily, where virtual point-like X-ray marks are assumed. With the help of the C-arm X-ray machine ( 1 ), known projection matrices P1Vol and P2Vol are used for the two registration positions of the C-arm X-ray apparatus ( 1 ) calculates the image coordinates of the virtual X-ray marks.
• 7) By means of a back projection using the projection matrices P1Navi and P2Navi, the coordinates of the respective virtual X-ray marks in the coordinate system of the position detection system (FIG. 1 ).
• 8) From the coordinates of the virtual X-ray marks in the coordinate system Navi of the position detection system ( 2 ) and in the coordinate system Vol of the C-arm X-ray machine ( 1 ), the coordinate transformation VolTNavi is determined.
• 9) With the in process step 2 ) and stored coordinate transformation NaviTReg1 the shift-invariant matrix VolTReg1 = VolTNavi · NaviTReg1 is calculated and stored in a computing memory of the computing unit ( 32 ) stored.
• 10) For later use of the C-arm X-ray unit ( 1 ), after this has been relocated in the meantime, the position of the X-ray receiver ( 3 ) in the registration position Reg1 in the displaced coordinate system Navi 'of the position detection system ( 5 ), namely Reg1TNavi 'and a coordinate transformation VolTVavi' = VolTReg1 * Reg1TNavi 'and for the navigation with the displaced C-arm X-ray device ( 1 ) used.

It is provided in the invention that after a spatial displacement of the C-arm X-ray device ( 1 ) the coordinates of the X-ray receiver ( 3 ) in the first registration position of the C-arm X-ray apparatus ( 1 ) by means of the position detection system ( 5 ) and a coordinate transformation in the coordinate system of the position detection system ( 5 ) with which the coordinate transformation VolTNavi of claim 1 is multiplied.

It is further provided in the context of the invention that the determination of the coordinate transformation VolTNavi takes place according to a matching method, preferably according to the matching method of Umeyama.

In 5 the circuit of the C-arm X-ray apparatus used for the method and the position detection system is shown schematically. A control computer ( 31 ) controls all movement and X-ray processes of the C-arm X-ray machine and is connected to a computing unit ( 32 ) in connection. The arithmetic unit ( 32 ) contains all facilities for processing and storing the kinematic model of the X-ray diagnostic device, the recorded 2D projections and the coordinate transformations obtained during the registration as well as devices for the reconstruction of a 3D volume from 2D X-ray projections. To the arithmetic unit ( 32 ) is a position detection computer ( 30 ) and in turn the camera system of the position detection system. A data interface ( 33 ) allows data exchange between the processing unit ( 32 ) and an unspecified navigation device ( 34 ).

LIST OF REFERENCE NUMBERS

1

C-arm X-ray device

2

Registration Phantom

3

X-ray receiver

4

X-ray source

5

Position detection system

10

Arrangement of X-ray marks

11

First X-ray mark

12

Second X-ray mark

13

Third X-ray mark

20, 20 '

Arrangement of navigation tags

21

First navigation mark

22

Second navigation mark

23

Third navigation mark

30

Location data acquisition computer

31

tax calculator

32

computer unit

33

Data Interface

34

navigation device

40

coupling part

41

coupling part

Claims (4)

Method for registering a C-arm X-ray device ( 1 ) with a position detection system ( 5 ) using a Registrierungsphantoms ( 2 ), which in a defined spatial relationship to each other an arrangement ( 10 ) of at least 3 x-ray marks ( 11 . 12 . 13 ) and an arrangement ( 20 ) of navigation marks ( 21 . 22 . 23 ), by means of which the positions of the X-ray marks ( 11 . 12 . 13 ) in a coordinate system of the position detection system ( 5 ) are detectable, wherein the C-arm X-ray device ( 1 ) an X-ray source ( 4 ), an X-ray receiver ( 3 ) and a computing unit ( 32 ) and is equipped to record projection images of a scan and to reconstruct an X-ray volume therefrom and to be equipped to detect the position of the X-ray receiver ( 3 ) with regard to the position-finding system ( 5 ) in at least one registration position of the C-arm X-ray device ( 1 ), wherefrom the registration phantom ( 2 ) in two different spatial orientations of the registration phantom ( 2 ) for a first and a different second registration position of the C-arm X-ray device ( 1 ) an X-ray projection of the X-ray marks ( 11 . 12 . 13 ) with the C-arm X-ray device ( 1 ) and an orientation of the arrangement ( 20 ) of navigation marks ( 21 . 22 . 23 ) of the registration phantom ( 2 ) by means of the position detection system ( 5 ) and in at least one of the two registration positions of the C-arm X-ray apparatus ( 1 ) the position of the X-ray receiver ( 3 ) in a coordinate system of the position detection system ( 5 ) and stored in a computer memory of the arithmetic unit ( 32 ) is stored as NaviTReg1, characterized by the method steps 1) the position of the projections of the arrangement ( 10 ) of X-ray marks ( 11 . 12 . 13 ) in the projection images is determined automatically and stored in a computer memory of the computing unit ( 32 2) in an identification process step, in each projection image of an arrangement ( 10 ) of X-ray marks ( 11 . 12 . 13 ) each image of a single X-ray mark ( 11 . 12 . 13 ) of the X-ray mark ( 11 . 12 . 13 ) associated with the respective image of the X-ray mark ( 11 . 12 . 13 3) for each of the two projection photographs, the point correspondence method is used to obtain from the coordinates of the X-ray marks ( 11 . 12 . 13 ) in the coordinate system of the position detection system, the projection matrices P1Navi and P2Navi determined and in a computing memory of the arithmetic unit ( 32 4) in the scan volume of the C-arm X-ray apparatus (FIG. 1 ) at least three spatial points in the coordinate system of the C-arm X-ray apparatus ( 1 ) arbitrarily chosen, at which virtual dot-shaped X-ray marks are assumed; with the help of the C-arm X-ray machine ( 1 ), known projection matrices P1Vol and P2Vol are used for the first and the second registration position of the C-arm x-ray apparatus ( 1 5) the coordinates of the virtual X-ray marks in the coordinate system of the position detection system (FIG. 1 6) from the coordinates of the virtual X-ray marks in the coordinate system Navi of the position detection system (FIG. 2 ) and in the coordinate system Vol of the C-arm X-ray machine ( 1 ), the coordinate transformation VolTNavi is determined, 7) with the under process step 2 ) and stored coordinate transformation NaviTReg1 the shift-invariant matrix VolTReg1 = VolTNavi · NaviTReg1 is calculated and stored in a computing memory of the computing unit ( 32 ), 8) and it will be in later use of the C-arm X-ray machine ( 1 ), after it had been relocated in the meantime, the position Reg1TNavi 'of the X-ray receiver ( 3 ) in the registration position Reg1 in the displaced coordinate system Navi 'of the position detection system ( 5 ) and determines a coordinate transformation VolTNavi '= VolTReg1 * Reg1TNavi' and for the navigation with the displaced C-arm X-ray device ( 1 ) used. Registration method according to claim 1, characterized in that after a spatial displacement of the C-arm X-ray apparatus ( 1 ) the coordinates of the X-ray receiver ( 3 ) in the first registration position of the C-arm X-ray apparatus ( 1 ) by means of the position detection system ( 5 ) and a coordinate transformation in the coordinate system of the position detection system ( 5 ) is determined, with which the coordinate transformation VolTNavi of claim 1 is folded. Method for registration according to one of Claims 1 to 2, characterized in that the determination of the coordinate transformation VolTNavi takes place according to a matching method. Registration method according to claim 3, characterized in that the determination of the coordinate transformation VolTNavi is carried out according to the matching method of Umeyama.

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