Arrangement of x-ray markers in the form of a pyramid
12 claims: 5 independent, 7 dependent
- 1Röntgenmarkervorrichtung (550) mit einer Anordnung von Röntgenmarkern (571, ..., 576;591, ..., 596), wobei die Anordnung Geraden definiert, die als Vorrichtungs-Geraden bezeichnet werden, dadurch gekennzeichnet, dass zumindest ein Teil der Vorrichtungs-Geraden, die als Pyramiden-Geraden bezeichnet werden, Abschnitte aufweisen, die die Kanten von Pyramiden definieren, wobei mindestens eine Spitze jeder der Pyramiden außerhalb eines durch die Röntgenmarker (571, ..., 576;591, ..., 596) begrenzten Bereichs liegt.
- 2Röntgenmarkervorrichtung (550) nach Anspruch 1, bei welcher auf mindestens drei der Pyramiden-Geraden, die sich in der Spitze der mindestens einen Pyramide schneiden, insgesamt mindestens 5 der Röntgenmarker (571, ..., 576;591, ..., 596) liegen.
- 3Röntgenmarkervorrichtung (550) nach einem der vorhergehenden Ansprüche, wobei entlang mindestens drei der Pyramiden-Geraden jeweils mindestens zwei der Röntgenmarker (571, ..., 576;591, ..., 596) angeordnet sind.
- 4Röntgenmarkervorrichtung (550) nach einem der vorhergehenden Ansprüche, die eine Navigations-Markervorrichtung (581, ..., 584) zur Detektion der Lage der Röntgenmarkervorrichtung (550) durch ein Navigationssystem umfasst, wobei die Navigations-Markervorrichtung (581, ..., 584) außerhalb eines durch die Röntgenmarker (571, ..., 576;591, ..., 596) begrenzten Bereichs liegt.
- 5Verfahren zum Bestimmen einer Zuordnung zwischen Röntgenmarkern (571, ..., 576; 591, ..., 596) einer Röntgenmarkervorrichtung (550) nach einem der vorhergehenden Ansprüche und Markerbildern eines Röntgenbildes, das sich bei einer gegebenen Abbildungsgeometrie durch eine Röntgen-Abbildung der Röntgenmarkervorrichtung (550) ergibt, wobei die Markerbilder die Röntgenmarker (571, ..., 576; 591, ..., 596) in dem Röntgenbild darstellen, und wobei neben Röntgenbilddaten, die Informationen über die relative Lage der Markerbilder im Röntgenbild umfassen, Vorrichtungsdaten bereitgestellt werden, die die relative Lage der Röntgenmarker (571, ..., 576; 591, ..., 596) beschreiben, und wobei die relative Lage der Röntgenmarker (571, ..., 576; 591, ..., 596) eine Anordnung beschreibt, die invariante Eigenschaften aufweist, die bei der Röntgen-Abbildung erhalten bleiben und die invariante Geraden umfassen, wobei die Anordnung Geraden definiert, die die invariante Eigenschaft haben und als Vorrichtungs-Geraden (V1, ..., V 12) bezeichnet werden, wobei das Verfahren folgende Schritte umfasst:a) basierend auf den Röntgenbilddaten und den Vorrichtungsdaten werden Markerbilder und Röntgenmarker (571, ..., 576;591, ..., 596) jeweils unter Berücksichtigung der invarianten Eigenschaften der Anordnung gruppiert, wobei Markerbilder, die auf einer gemeinsamen, als Bild-Gerade bezeichneten Geraden liegen, jeweils zu einer Bild-Geraden-Gruppe zusammengefasst werden und Röntgenmarker (571, ..., 576;591, ..., 596), die auf einer der Vorrichtungs-Geraden (V1, ..., V12) liegen, jeweils zu einer Vorrichtungs-Geraden-Gruppe zusammengefasst werden;b) gruppenweise werden die Zuordnungsmöglichkeiten zwischen Markerbildern und Röntgenmarkern bestimmt, wobei zur Bestimmung der Zuordnungsmöglichkeiten zwischen den Röntgenmarkern (571, ..., 576;591, ..., 596) und Bildmarkern (A, ..., H) bestimmt wird, welche Zuordnungen zwischen den Bild-Geraden-Gruppen und den Vorrichtungs-Geraden-Gruppen möglich sind;c) falls für die Zuordnungsmöglichkeiten Abbildungsgeometrie-Daten für die Röntgen-Abbildung, die die Geometrie der Röntgen-Abbildung beschreiben, unter Berücksichtigung der invarianten Eigenschaften berechenbar sind, werden basierend auf den berechneten Abbildungsgeometrie-Daten virtuelle Röntgenbilder der Röntgenmarker bestimmt und die virtuellen Röntgenbilder werden mit einem realen Röntgenbild der Röntgenmarker verglichen;d) wird eine Übereinstimmung zwischen einem bestimmten virtuellen und einem realen Röntgenbild zumindest in einem vorbestimmten Umfang festgestellt, so wird die dem bestimmten virtuellen Röntgenbild zu Grunde liegende Zuordnungsmöglichkeit als korrekt erkannt.
- 6Verfahren nach Anspruch 5, bei welchem der Schritt der Gruppierung umfasst, dass Vorrichtungs-Geraden-Gruppen, die auf Vorrichtungs-Geraden basieren, die sich in einem gemeinsamen Vorrichtungs-Schnittpunkt schneiden, zu Vorrichtungs-Schnittpunkt-Gruppen zusammengefasst werden und Bild-Geraden-Gruppen, die auf Bild-Geraden basieren, die sich in einem gemeinsamen Bild-Schnittpunkt schneiden, zu Bild-Schnittpunkt-Gruppen zusammengefasst werden,
- 7Verfahren nach Anspruch 6, bei welchem der Schritt der gruppenweisen Bestimmung der Zuordnungsmöglichkeiten umfasst, dass jeweils für eine der Zuordnungsmöglichkeiten zwischen den Vorrichtungs-Schnittpunkten und den Bild-Schnittpunkten, die Zuordnung von den Röntgenmarkern (571, ..., 576;591, ..., 596), die Mitglieder einer der Vorrichtungs-Geraden-Gruppen sind, zu den Bildmarkern (A, ..., H), die Mitglieder einer der Bild-Geraden-Gruppe sind, so erfolgt, dass die Röntgenmarker (571, ..., 576;591, ..., 596) und die Bildmarker (A, ..., H) einander zugeordnet werden, die jeweilig in einer Richtung entlang der Vorrichtungs-Gerade (V1, ..., V12) ausgehend vom Vorrichtungs-Schnittpunkt, im Falle der Röntgenmarker (571, ..., 576;591, ..., 596), und in einer Richtung entlang der Bild-Gerade ausgehend vom Bild-Schnittpunkt, im Falle der Bildmarker (A, ..., H) denselben Rang in der Abfolge einnehmen, wobei die Anzahl der Bildmarker (A, ..., H) der Abfolge und die Anzahl der Röntgenmarker (571, ..., 576;591, ..., 596) der Abfolge gleich sind und wobei die Anzahl der Röntgenmarker (571, ..., 576;591, ..., 596) auf der Vorrichtungs-Geraden (V1, ..., V12), wenn man ausgehend vom Vorrichtungs-Schnittpunkt in die entgegengesetzte Richtung geht, anders ist.
- 8Verfahren nach einem der Ansprüche 5 bis 7, bei welchem bei dem Schritt der gruppenweisen Bestimmung der Zuordnungsmöglichkeiten invariante Eigenschaften so berücksichtigt werden, dass durch Ausschluss von Zuordnungsmöglichkeiten die Anzahl der durch Permutation möglichen Zuordnungen reduziert werden.
- 9Verfahren nach einem der Ansprüche 5 bis 8, bei welchem basierend auf mindestens einer der invarianten Eigenschaften der Anordnung, die aus den Vorrichtungsdaten bestimmt wird, Bildbereiche im Röntgenbild, die möglicherweise Bildmarker (A, ..., H) darstellen, als Bildmarker (A, ..., H) bestimmt werden, und/oder bestimmt wird, dass in einem Bildbereich die Darstellung eines Bildmarkers (A, ..., H) fehlt.
- 10Navigationsverfahren, umfassend das Verfahren nach einem der Ansprüche 5 bis 9, bei welchem Gegenstandlagedaten, die die Lage eines Gegenstandes (400) beschreiben, und Röntgenmarkervorrichtung-Lagedaten, die die Lage der Röntgenmarkervorrichtung (550) beschreiben, bereitgestellt werden;und bei welchem basierend auf den Abbildungsgeometrie-Daten, die der als korrekt erkannten Zuordnungsmöglichkeit entsprechen, den Röntgenmarkervorrichtungs-Lagedaten und den Gegenstandslagedaten, die den Abbildungsgeometrie-Daten entsprechende, projektive Abbildung des Gegenstands (400) im Röntgenbild berechnet wird.
- 11Programm, das, wenn es auf einem Computer (300) läuft, den Computer (300) veranlasst, die Schritte nach einem der Verfahren 5 bis 10 durchzuführen.
- 12Navigationssystem mit einem Computer (300), auf dem das Programm nach Anspruch 11 geladen ist oder läuft, wobei der Computer (300) eine Dateneingabeeinrichtung aufweist, um die Röntgenbilddaten und die Vorrichtungsdaten einzugeben, mit einer Detektionsvorrichtung (600), um Navigations-Markervorrichtungen (210, 410, 510) zu detektieren, um die Lage der Röntgenmarkervorrichtung (571, ..., 576;591, ..., 596) und eines Gegenstandes (400) zu bestimmen;mit einer Anzeigevorrichtung (320), wobei das Programm ausgebildet ist, basierend auf der detektierten Lage der Röntgenmarkervorrichtung (571, ..., 576;591, ..., 596) und des Gegenstandes (400) zu berechnen, wie der Gegenstand (400) im Röntgenbild dargestellt werden würde, wenn es gemäß denjenigen Abbildungsgeometrie-Daten von Röntgenstrahlen durchstrahlt werden würde, die der als korrekt bestimmten Zuordnung entspricht.
Independent claims12
126 paragraphs in 2 sections, as filed
p0001The present invention relates to x-ray marker and the assignment of x-ray markers to images of these X-ray markers. The images of X-ray markers are referred to herein as image markers.
p0002Known examples of X-ray marker devices are registration body, called Registrierungskits (Engl .: "fluoro registration kits"). These are fixed to the image intensifier of a C-arm. In some rotation is possible relative to the image intensifier. At the registration bodies optical markers (navigation markers) are further mounted, which allow a determination of the location registration body by means of a navigation system. The navigation systems (Image Guided Surgery) used for the so-called image-guided navigation. For example, using cameras that are part of the navigation system are detected the optical marker. The evaluation of X-ray image and the X-ray marker is shown as well as the known location of Registrierkkörpers relative to the x-ray machine allow the registration of an instrument in a desired reference system that can be specified by the navigation system, and the virtual representation of the instrument on the radiograph without a radiograph made becomes.
p0003The following documents relate to such methods or devices:<ul><li><patcit id="pcit0001" dnum="US61054487B"><text>US 61 / 054,487</text></patcit></li><li><patcit id="pcit0002" dnum="DE19917867A1"><text>DE 199 17 867 A1</text></patcit></li></ul>
p0004Can you turn the registration body, so there is in the evaluation of the X-ray image to obtain a mapping between the image markers and the x-ray markers, only the possibility of rotation and the possibility of mirroring. The latter is given, since the X-ray image can be output mirrored or non-mirrored by the X-ray machine. Because of this low variation possibilities (rotation and mirroring) an assignment is obvious. Thus, an association between the x-ray markers and image markers is easily and quickly done by an algorithm.
p0005then as (pinhole camera) is determined information on the X-ray imaging geometry for the assignment according to the principles of the pinhole camera. This information allows in particular to calculate relative to the registration body the position of an X-ray source. The X-ray imaging geometry can eg define a spatial transformation into projection center (6 external imaging parameters: 3 rotary, 3 translational) and 4 internal imaging parameters: 2 scaling, which convert from world coordinates [mm] in pixels of the electronic image and the coordinates of ( notional) principal point ( "principal point").
p0006The above-described principle also applies in principle for the Scout-View (see below). Respect to the main point, the two coordinates (u, v) are preferably understood as the calculated center of the image.
p0007The data, containing the above information on the X-ray imaging geometry are referred to herein as imaging geometry data. In particular, the imaging geometry data includes the calculated projection matrix. The imaging geometry data, and in particular the projection matrix represent a general law of imagery for the given x-ray imaging geometry. They thus allow to calculate how an arbitrary point in space in the (undistorted) represents radiograph, if we start from the same X-ray imaging geometry, as it was given in the preparation of X-ray image that represents an image of the X-ray marker device. It thus represents a generalization of the imaging process, the proceeds from the special case of the Figure of the x-ray marker device on the X-ray image for a given X-ray Abbbildungsgeometrie.
p0008The calculation of the imaging geometry data takes place, for example by using a camera model which as well as possible reflects the actual imaging properties. The usual camera model is the pinhole camera model. That is, the imaging geometry data is calculated as based on the principles of the pinhole camera. Reference is made to the following publications, which are hereby incorporated by reference into the disclosure with:<ol><li>1. "<nplcit id="ncit0001" npl-type="s"><text>An Efficient and Accurate Camera Calibration Technique for 3D Machine Vision ", Roger Y. Tsai, Proceedings of IEEE Conference on Computer Vision and Pattern Recognition, Miami Beach, FL, 1986, pages 364-374</text></nplcit>,</li><li>2. "<nplcit id="ncit0002" npl-type="s" url="http://www.cs.emu.edu/~rgw/TsaiDesc.html"><text>A versatile CameraCalibration Technique for High-Accuracy 3D Machine Vision Metrology Using Off-the-Shelf TV Cameras and Lenses ", Roger Y. Tsai, IEEE Journal of Robotics and Automation, Vol. RA-3, No. 4, August 1987, pages 323-344, see also http://www.cs.emu.edu/~rgw/TsaiDesc.html</text></nplcit></li><li>3. Publication of <nplcit id="ncit0003" npl-type="s"><text>Ziv Yaniv, "Fluoroscopic X-ray Image Processing and Registration for Computer-Aided Orthopedic Surgery</text></nplcit>".</li></ol>
p0009As can be seen from the above given quote no. 2 and the local Internet address, five internal imaging parameters are mentioned in the described therein "Tsai's camera model", which are referred to therein as "internal parameters". Above, only four internal imaging parameters were noted. This is because that it is assumed in a given case of an undistorted image and therefore, the parameter "kappa1" is not required. If the image should be distorted, an equalization would advance preferably be done (see also discussion below). General describing the internal imaging parameters, such as the camera, ie in the given case, the X-ray apparatus forms an image while the external parameters in the world coordinate system to describe the position of the X-ray machine (position and orientation). According to the Tsai camera model is adapted to the specific conditions of the x-ray imaging, as in particular in the publication by Ziv Yaniv (see above) is described. In particular can be used 1 / f sx and f or the two scales.
p0010If the imaging geometry data determined may be reviewed by a virtual x-ray imaging of the registration body, whether the assignment is correct. The virtual x-ray imaging is determined by the imaging geometry data.
p0011If the relative position between the image intensifier and registration body but unknown, so there is a greater number of possible associations between the x-ray markers and image markers, which can lead to a considerable computing time of several minutes or hours (depending on the number of markers). However, such a calculation period is unacceptable in daily practice. Because of this long computation time registration body are currently being mounted relative to the image intensifier in practice.
p0012Another example of X-ray marker devices are "Röntgenkalibrierphantome" (see FIG. <patcit id="pcit0003" dnum="DE10215808"><text>DE 102 15 808</text></patcit>) Or "X-grid" (see. <patcit id="pcit0004" dnum="EP08156293A"><text>EP 08156293</text></patcit> or <patcit id="pcit0005" dnum="US61054487B"><text>US 61 / 054,487</text></patcit>), Which can be used for the determination of calibration information for calibrating a 3D X-ray CT device, in particular for determining the position of a 3D X-ray measurement volume relative to a predetermined by the navigation system using the system. The X-ray marker devices, in particular the carrier (eg, side walls) for the x-ray markers and the x-ray markers may be optically opaque.
p0013<patcit id="pcit0006" dnum="US20050113682A1"><text>US 2005/0113682 A1</text></patcit> discloses a system for designing of slice images through a selection object, identifiable reference markers are arranged in a fixed position relative to the selection object, comprising at least two identifiable marker. In this case, a radiation source is provided to irradiate the object selection to the reference marker. A recording medium or detector will then to a series of images produced.
p0014<patcit id="pcit0007" dnum="US20050109855A1"><text>US 2005/0109855 A1</text></patcit> discloses a navigation system for computer-assisted surgery, which employs a plurality of marker devices, wherein a non-segmenting common point connecting at least some of these markers together.
p0015<patcit id="pcit0008" dnum="EP0853920A2"><text>EP 0853920 A2</text></patcit> discloses an algorithm for calculating a biopsy system, the use of a phantom with a number of markers that can be arranged symmetrically or asymmetrically around in the Phantom.
p0016<nplcit id="ncit0004" npl-type="s"><text>Sorensen et al., Image-guided radiotherapy using a mobile kilovoltage x-ray device, Medical Dosimetry, Vol. 31, No. 1, pp. 40 to 50</text></nplcit> discloses the use of a calibration phantom with pyramidal arranged markers.
p0017<patcit id="pcit0009" dnum="DE19703556A1"><text>DE 197 03 556 A1</text></patcit> discloses the use of a calibration phantom with a first, X-ray absorbing marker array and a second marker array for the cameras, for example, infrared light-emitting diodes with the use of infrared cameras.
p0018<nplcit id="ncit0005" npl-type="s"><text>Schoenherr et al, a new algorithmic method for fluoroscopy-based neuronavigation, computer science News -. Image Processing for Medicine, Volume 116, 2004, pages 229-233</text></nplcit> discloses an algorithm for determining the position of instruments in previously recorded fluoroscopy images, which processes a dot pattern of ten steel balls, with three balls on three mutually orthogonal axes and are another at the intersection of these axes.
p0019<patcit id="pcit0010" dnum="US20070122020A1"><text>US 2007/0122020 A1</text></patcit> discloses an array of X-ray markers lie on straight lines that define the edges of a pyramid, with a radiation source in the top of the pyramid is.
p0020Object of the invention is to facilitate the assignment of x-ray markers to screen markers even when no information about the location of the x-ray marker device relative to the X-ray apparatus, in particular relative to the x-ray source and the image intensifier.
p0021The above object is achieved by the subjects of the independent claims. The dependent claims are directed to advantageous developments.
p0022An x-ray marker device according to the invention comprises an array of x-ray markers wherein the assembly defines straight lines that are referred to as device line, and at least a part of the device straight lines which are referred to as pyramids straight, having portions which define the edges of the pyramids, wherein at least one tip of each of the pyramids is outside a range limited by the X-ray marker area.
p0023In the straights and pyramids may especially be virtual (geometric) structures which are defined by the physical (real and material) X-ray marker.
p0024Device straight lines having portions defining edges of a pyramid, are referred to herein as a "pyramid straight lines".
p0025Since it is straight both in the device as a straight line even when the pyramids straight, they are invariant under a linear mapping. Examples of linear mappings are projective transformations, perspective projection, parallel projection and the so-called "Scout View" (mixture of parallel and perspective projections. With ordinary x-rays are usually to perspective projections. With modern CT scanners, the aforementioned Scout View is often predominantly . Finally, the present invention also a parallel projection is possible, if a point X-ray source and the detector driving parallel on the patient. particular uses linear imaging properties of the X-form. when in the following of a projective figure is mentioned, this is merely exemplary. the invention X-ray marker device thus has an arrangement which has an invariant property. Because the inventive arrangement defined pyramids straight, this invariant property in the radiograph is easier to find and the association between x-ray markers and image markers is facilitated, as will be explained later.
p0026The aforementioned pyramid straight lines are defined by straight education credits, which in turn result from the arrangement of the X-ray marker. According to the laws of geometry you need at least two points, ie Straight Education points to a defining line. The Straight Education points are particularly the position of the x-ray markers, ie for example by the respective geometric center of the X-ray marker (eg the center of a sphere, if the x-ray markers are spherical) determined. Straight Education points can be intersections that result from device lines, which are in turn defined by Straight Education points at which it is X-ray marker. Lying for example at least two radiopaque markers at the edges of a pyramid, then the pyramid lines intersect in a device intersection. This device intersection also provides a straight line formation point is that another pyramid straight can form together with another X-ray marker, which is for example at a corner of the pyramid, which naturally also goes by the same pyramid tip, although not mentioned with the other before both pyramids-line is identical.
p0027The X-ray marker not only lie on one side of the pyramid tip on the other. This is true for all pyramids straight. In this manner can later be facilitated the association between x-ray markers and image markers, since the neighborhood relationships, so the order starting from the device intersection (pyramid tip) can be used. This will be explained in more detail.
p0028X-ray markers are in particular body from a material that does not transmit the X-rays or at least substantially attenuates. The body may be of any shape and in particular take basic geometric shapes, such as sphere or cube. The bodies are in particular spaced apart. The distance is preferably greater than the body diameter of the X-ray marker. Body diameter are preferably greater than 1 mm and / or less than 3cm.
p0029On the pyramid straight lines are at least two X-ray markers to identify artifacts later radiograph better. The pyramid tip is outside the range in which there are the X-ray marker. In this case, no X-ray marker is on top of the pyramid.
p0030The above lines, in particular the device straight and pyramid lines are invariant under a projective mapping. The inventive arrangement of the X-ray marker thus describes an invariant property.
p0031Invariant properties are properties which are retained in a projective mapping. In particular, these properties are invariants of each projective mapping. In particular, they provide a characterizing feature of projective geometry represents. Invariant properties of projective geometry are, for example, straight lines which are defined by the arrangement of the X-ray marker, such as the device lines, and are also known as "invariant line" herein. Another example is the so-called cross-ratio or the English "cross ratio". This double relationship also provides an invariant property is, therefore represents an invariant of the projective image. The cross ratio is in the geometry of a number that identifies the relative position of four lying on a straight points. Two of these points determine thereby a distance which is shared by the other two points. The cross ratio is defined as the ratio of the two ratios.
p0032The x-ray marker device defined in particular at least 6 Straight Education points. This at least 6 Straight Education points are preferably determined from x-ray markers. In particular, one of at least 6 points Straight Education can also be a device intersection, in particular a pyramid point at which or in which no X-ray marker is. The least 6 Straight Education points are preferably not all in one plane.
p0033In particular, the total number of X-ray marker is less than 30 or 20 or 10. In particular, the maximum distance between any two x-ray markers of the X-ray marker device is smaller than the diameter of a detection range of an X-ray apparatus, in particular smaller than 50 cm or 30 cm or 20 cm or 10 cm ..
p0034Preferably, at least 6 of the x-ray markers lie on invariant straight. They are also referred to herein as a invariant x-ray markers, since they define an invariant property.
p0035Preferably, at least three of the pyramid lines each containing a a portion of each side edge, and pyramid corresponds to the same. Preferably at least three of the pyramid straight portions, each corresponding to either a side edge of a pyramid and the base edge of at least one other pyramid, in particular the bottom edges of two other pyramids. Preferably, all X-ray markers lie on pyramids straight.
p0036As mentioned, it may also be in the Straight Education points to device intersections. Device intersections satisfy at least the condition that intersect in them at least two device lines. A device intersection may coincide with the position of an X-ray marker, or it can also arise at a point in space at which no X-ray marker is on which but intersect at least two device lines. Preferably, an intersection is only a device intersection when in him a certain predetermined number of device straight cuts and / or the number is greater than or equal to a predetermined minimum number (eg 3, 4 or 5) and / or less than or equal a predetermined maximum number (eg, total number of X-ray markers of the x-ray marker device minus 1 or minus 2). The predetermined number is preferably at least three. The predetermined number may be the same for all device intersections or they may be different. By the predetermined number, minimum number or maximum number to artifacts easier to identify.
p0037Preferably, at least 6 of the x-ray markers lie on device straight, so are particularly Straight Education points. Preferably at least three Straight Education points are on the line device, in particular pyramid straight.
p0038Specifically therefore agrees the situation of each of the straight education credits either with the position of the X-ray marker (especially the position of the geometric center of the X-ray marker) or the location of the device intersections.
p0039The defined by the arrangement device lines, especially the pyramid straight lines are preferably not all the in a plane, but in particular in at least two planes.
p0040The inventive arrangement an association between the x-ray markers and image markers is greatly facilitated in a radiograph. Because the x-ray markers lie on device straight lines that are invariant under the mapping, can be searched in the radiograph by respective straight lines (for example by means of an algorithm), by image marker candidates (ie possible image markers) are formed. Because preferably at least 6 Straight Education points, in particular at least 6 X-ray markers lie on device straight, this can for an algorithm that uses the pinhole principles (see above), and the imaging geometry data, in particular the geometry of the projective image will describe calculated used. Characterized in that the X-ray marker located on the apparatus line, the correct assignment can easily be found for them.
p0041The assignment is further facilitated by the fact that, preferably, a minimum number of <u>three</u> Straight Education points as greater <u>zwe</u>i (for example, 3 or 4 or 5), lie on at least part of the device lines, especially the pyramids straight. This means that also in the X-ray image with a flawless figure also the minimum number of points Straight Education radiograph should be identifiable. This reduces the influence of artifacts on the evaluation of the X-ray image in order to detect images of the x-ray markers (so-called image marker). If an image marker candidate radiograph and will be connected via a line with a picture marker or another image marker candidates, so would they run straight through another line forming point if the minimum number of straight line forming points is greater than two, to confirm that it is in the image marker candidates an actual image marker is. If this is not the case, the image marker candidate can be excluded as likely artifact of the mapping algorithm. then Letzteresinsbesondere if all X-ray markers lie on device straight lines, defined by a minimum number of points Straight Education, which is greater than two.
p0042According to one embodiment are all X-ray markers on pyramids straight. The pyramid lines intersect in at least one pyramid tip, where the number of intersecting pyramids-line is known. Combining the image marker candidates in an X-ray image, thus can identify the image marker by selecting only those image marker candidates that are on-screen lines that intersect in an image-intersection with a predetermined property. The predetermined characteristic is that in the image-intersection a number of picture-line cuts, corresponding to the number of pyramid straight lines which intersect in at least one pyramid top. By x-ray marker device, the number of intersecting in a pyramid tip pyramid line is predetermined. Thereby, the condition is known to be met by an image-intersection through which run the screen straights where are the image marker.
p0043The number of straight line forming points, in particular X-ray markers may be the same for all device lines. This can facilitate the detection of artifacts. But it can also be for certain lines differently and, in particular, two or more precisely education credits (in particular X-ray marker) differ from the other device straight to facilitate the identification and thus allocation of the line. On the other hand the risk of mutual coverage is higher, the closer the X-ray markers lie on the device line.
p0044Since lines are invariant under projection, is preferably assumed that the number of straight line forming points is invariant. Preferably, the X-ray marker device is designed to be on the device line, and in particular the Pyramids straight a minimum number of points Straight Education and / or a minimum number of x-ray markers. Walking image straight from a picture of device lines, in particular pyramid straight out, so they have to fulfill the corresponding condition. So there must be a minimum number of Straight Education point candidate or a minimum number of image marker candidates on the screen straight. Straight Education points in an X-ray image are markers or intersections, the device intersections, especially correspond pyramid tips. Due to the aforementioned known minimum number is therefore possible to exclude artifacts with a high probability.
p0045This reduces the number of possible mappings in practice considerably and hence the computation time. In short, the larger the minimum number of straight line forming points and / or X-ray markers with a device line, in particular pyramid straight lines, the safer apparent image markers (artifacts) can be identified.
p0046The computation time can further be reduced so that the X-ray marker to device lines, in particular pyramid lines are grouped and also straight lines are identified in the X-ray image having characteristics corresponding to the characteristics of the device-line, in particular pyramid straight line. These lines are referred to herein as a screen line. The image lines include at least one image marker and preferably also defined by a minimum number of points Straight Education, which is greater than two (for example, 3, 4 or 5). Straight Education points for screen lines have the features such as Straight Education points for device straight. "Corresponding" means herein that image markers correspond to the x-ray markers and "picture-intersections" the device intersections, in particular meeting the pyramid tips. Are in the case of a device straight line at least two of the Straight Education points x-ray markers, so accordingly in the case of picture-line at least two of the straight education credits image markers. Further, image-intersections represent Straight Education points for screen lines. Image intersections have here the same properties as the device intersections, wherein the image-line corresponding to the device line. Fulfill example device intersections, in particular pyramid tips the condition that intersect at them a certain number of device lines, in particular pyramid straight lines, the corresponding image points of intersection satisfy the condition that in them intersects the same number of screen lines if no artifacts interfere. If a minimum number and / or maximum number for the number of device lines (in particular pyramid straight lines) located in the device intersections (in particular pyramid tips) given cut, so the image intersection points fulfill the corresponding condition, if no artifacts interfere. In the image-intersections, the number of intersecting image straight greater than or equal to the minimum number and / or less than or equal to the maximum number should therefore be. If deviations are found, then this can be taken as an indication that it is at an intersection in the picture to no picture-intersection (or that artifacts this deviation cause).
p0047In one embodiment, those lines are selected in the picture as a screen line that meet the characteristics of pyramid straight. Are the pyramid tips a minimum number and / or a maximum number specified for the number of intersecting in the pyramid tip pyramid lines, the intersections are checked in the image whether to cut into them the known minimum and / or maximum number of lines. Only when they meet this condition, they are selected as the picture line corresponding pyramid lines, for further process steps. According to the intersection points may only be selected as a picture-intersections for further steps, if they comply with pyramid tips.
p0048The aforementioned minimum and maximum number may be determined by the x-ray marker device. Thus the minimum number of minimum number of pyramid straight lines may correspond to that intersect in one of the pyramid tips and the maximum number is the maximum number of pyramid straight match that intersect in one of the pyramid tips. The number of intersecting respectively in the pyramid tips line may be the same for all, in particular pyramid tips. In this case there are for example, only a single predetermined number. In the present process, however, the aforementioned minimum or maximum number are also used to eliminate artifacts as possible. In an X-ray image resulting from connection of the image markers or image marker candidates a variety of random intersections where typically cut but only two lines. Substituting the minimum number for selecting the screen intersections greater than two (preferably greater than three), one can thus avoid incorrect selection of an image intersection point with a high probability. To screen intersections corresponding pyramid tips, not to be confused with image markers that do not lie on a pyramid tip, but in which intersect more lines, you can also set a maximum number. This maximum number is preferably less than the number of x-ray marker minus 1 and for example the maximum number of pyramid straight lines which intersect in a pyramid tip or between this maximum number and the number of X-ray marker minus 1. The reason for the maximum number, the is used in the identification, lies in the fact that, the pyramid tips correspond in picture-intersections, typically cut less straight, as in picture-intersections that match screen markers that x-ray markers match, do not lie on a pyramid top.
p0049In the method according to the invention the minimum number and / or maximum number can therefore be used by an intersection is only selected as an image-intersection, if it satisfies the following condition: Number of intersecting image straight greater than or equal (minimum number - X) and / or less than or equal (maximum number + Y), the minimum number the least number which corresponds in a pyramid tip intersecting pyramids straight and corresponds to the maximum number of the largest number of intersecting in a pyramid tip line and where X and Y are integers greater than or are zero. X> 0 and Y> 0 thus allow artifacts to a certain extent to tolerate and thus still evaluating the image when randomly generate artifacts another picture straight line passing through an image-intersection, or when image marker is missing in the image, so that an image -Straight on-screen intersection missing.
p0050Cutting itself, if the minimum number is greater than 2, at an intersection in the image more than two picture lines, so this is already an indication that it is a picture-intersection, since typically at intersections, where no image markers are cut only two lines. In one embodiment, one can thus screen intersections in particular impose the condition that intersect in them a minimum number of screen lines, the minimum number is at least three.
p0051The image markers can be grouped by image-line, in particular, as described above, were selected in the image corresponding to so-apparatus line and in particular pyramids straight. The determination of the allocation options can then in groups, take place between the X-ray markers lie on device straight (in particular pyramid straight) and image markers that are on-screen line. This reduces the required computing power significantly. This is explained further below in connection with the description of the method of the invention further.
p0052The arrangement of the X-ray marker is such that they define at least six device lines which intersect at two device intersections. For three or more device line so there is a common device intersection so intersect as three-apparatus line or four-line device in the common device intersection.
p0053Preferably, at least a part of the X-ray marker, preferably at least 6 at the corners of at least one truncated pyramid. The truncated pyramid has preferably at least three side surfaces, preferably 4 or 5 sides, or more. For example, the number of side faces of the truncated pyramid between three and ten, for example, between three and six. For example, the number of side faces 4. The latter means that the truncated pyramid of the geometry of a cube is similar, but is not equal. Preferably, at least a part of the X-ray marker is located at the corners of the truncated pyramid and so on pyramids straight.
p0054According to the present invention, the X-ray marker thus define arrangements that a pyramid structure, for example comprise a truncated pyramid. The top of the pyramid is a straight formation point on which there is no X-ray marker is.
p0055Preferably, the device lines intersect in Device intersection at an angle equal to 90 ° in order to reduce the risk of overlaps in the radiograph. The angle may be obtuse, but is preferably pointed to, regardless of the direction of looking at the x-ray marker device varying the distance between the nearest and the farthest past X-ray marker, which lie in a predetermined volume to be irradiated by X-rays, as low as possible to keep. The acute angle is less than 90 ° and preferably less than 80 °, 70 °, 60 °, 50 °, 40 ° or 30 °. The x-ray marker may, in particular, and preferably at the corners and / or edges of the truncated pyramid, but also on the side and / or bottom surfaces of the pyramid.
p0056The pyramid peaks are outside a range which is limited by x-ray marker. This applies preferably at least for a large part of the device points of intersection, in particular pyramid tips. This has the advantage that for the determination of the allocation options also points outside the x-ray marker area may be utilized. X-ray markers are preferably present within the radiation range of the X-ray apparatus, which is mapped to the X-ray image, to assist in the determination of the assignments can. However, the device intersections do not necessarily lie within this radiation range, if they are virtual. Thus, by the arrangement of the device intersections outside the x-ray marker range, the number of points for a mapping option can be found, be increased without pack closer to x-ray marker. A denser packing of the x-ray markers would increase the risk of mutual overlap, which makes the evaluation of the radiograph. On the other hand facilitates a higher number of points Straight Education excluding and recognizing artifacts.
p0057The X-ray marker device can be used for registering and for calibration. According to a preferred embodiment, the X-ray marker device is part of a recording body that allows the registration of an object in a reference system of a navigation system. Registration takes place in particular in a reference system in which rests the radiograph and / or in the one depicted in the radiograph body structure of a patient rests.
p0058According to another embodiment the X-ray marker device may also be used to determine the calibration information for an X-ray device. In particular, the X-ray marker device according to the invention can be used in the invention to determine said calibration information. This calibration information comprises information about the positional relationship and / or spatial relationship between a reference system in which the X-ray machine is at rest and, in the case of a three-dimensional X-ray scans, a 3D scan reference system in which a determined from the 3D X-ray scan data model of a body rests (see<patcit id="pcit0011" dnum="EP08156293A"><text>EP 08 156 293.6</text></patcit>).
p0059Preferably, the X-ray marker device according to the invention comprises a navigation marker device and is in particular formed as a registration body. A navigation marker device comprises an array of navigational markers. Navigation markers are markers that can be detected by the detection device of a navigation system. It may be in navigational markers for active or passive markers, which emit radiation and / or waves or reflect. The rays or waves can be electromagnetic radiation or waves, such as light or infrared light. It may, for example, sound waves act as ultrasonic waves. By the detection of the navigation marker, the navigation system can determine the location of the navigation markers. Since the relative position between navigation markers is preferably known, the navigation marker device can identify. Also, preferably the relative position between the navigation markers and the x-ray markers known so that it can be concluded from the detected position of the navigation marker to the position of the X-ray marker. By daserfindungsgemäße method the relative position of the X-ray imaging geometry can be determined relative to the x-ray markers. Thus, the navigation system is the position of the X-ray imaging geometry known when the navigation marker to be detected. Will now be an object such as instrument or implant used in the navigation markers are also mounted, the position of which are known relative to the object, the navigation system can calculate the position of the object relative to the X-ray imaging geometry. In particular, the system can calculate (using the imaging geometry data), which position the object (eg the instrument) would take the radiograph if he would be irradiated by X-rays which follow the predetermined by the X-ray imaging geometry conditions. It can thus be calculated virtually no operating or use of X-ray apparatus, which occupies position of the object in the radiograph. The navigation markers are preferably arranged spaced apart from the X-ray markers. Preferably, the minimum distance between an (arbitrary) of the navigation markers and one (any) of the X-ray marker is greater than the minimum distance between the x-ray markers with one another, in particular greater than the maximum distance between the x-ray markers.
p0060In one embodiment, the navigation system is told where lies at least approximately to the image intensifier, so the image plane of the X-ray machine. This can cause, for example by mounting of navigation markers on X-ray apparatus, in particular at the image intensifier and / or on the X-ray source. You can also specify recognizable to an operator for the navigation system by means of a pointer, the direction of x-ray source to the image intensifier. The detection of the navigation markers of X-ray marker device may then be utilized to at least roughly determine the position of the X-ray marker device relative to the source and image amplifier. This gross specific location can then be used to use a smart choice for an initial allocation at the beginning of the allocation method. In particular, as to determine which screen intersections correspond to which pyramid tips are the most likely. With such a specific, probable association between screen intersections and pyramid tips can then be started the assignment procedure. Thus, the probability may be increased that the allocation method more quickly finds the correct assignment.
p0061The x-ray marker device of the invention is preferably freely moving (in all directions) relative to the X-ray apparatus, ie in particular not stationary relative to the X-ray machine or fixed, without limitation, of degrees of freedom. In particular, they should preferably not be mounted or fixed to the X-ray machine. This facilitates handling. In particular thereby the cost is reduced compared to conventional Registrierungskits. In addition, the X-ray marker device according to the invention can, since it is preferably not free to move and is fixed sterilize easier. Also, the mechanism of the X-ray apparatus is not loaded by the X-ray markers according to the invention device, which is preferably not fixed to the X-ray apparatus. Advantageously, no sterile covers to X-ray marker, the inventive device must be placed, since complete sterilization due to the free movability is possible. In particular, the quality of the X-ray image thus is not affected by a sterile cover.
p0062The present invention helps particularly advantageous with the following challenges: the First image as many markers as possible are preferably identified on the radiograph. In this case, in particular assumed that the markers of a Entzerrgitters, if any, have already been removed. Secondly preferably artifacts are detected, ie it should preferably be correctly recognized that an image marker candidate is an artifact or an image marker. Thirdly, preferably the identified image markers are so placed in a correct correlation (mapping) to the physical markers to x-ray markers. The use according to the invention of the invariant properties helps solve all three aforementioned challenges. In particular, the second and the third point can be interwoven.
p0063The present invention further relates to a method for determining a mapping between the X-ray markers of the X-ray marker device and marker image a radiographic image. The invention relates to the use of the X-ray marker device according to the invention in the inventive method.
p0064If the correct association found, including the assignment of corresponding X-ray imaging geometry is defined, which is the mapping of the x-ray marker device for generating the X-ray image based and which is described by imaging geometry data. It is in the X-ray imaging on the assumption that this is a projective transformation, in particular follows the laws that underlie the principles of the pinhole camera.
p0065Based on a known X-ray imaging geometry, it is particularly possible to calculate the position of an X-ray source relative to the X-ray marker device. The calculated position of the X-ray source clearly corresponds to the intersection in the backward running X-rays that produce the X-ray image, would intersect. If the projection matrix is known, then, on this basis, if for example the position of an object is known relative to the calculated position are calculated, what image this object would result in an image produced by the X-ray source X-ray image. The projection matrix is an example of a mapping matrix (in a world coordinate system, for example) depicts a three-dimensional point in the space on a two-dimensional point which lies in a plane for the detection of the ray is adopted. The imaging matrix therefore describes the mapping of the X-ray markers on the radiograph. Generally, the imaging array has 11 degrees of freedom. Taking as simplified camera model for the description of the image on a pinhole camera model, so can the degrees of freedom on 10 reduce. Both matrices (with 10 or 11 parameters) are projection matrices. The difference in the 10-parameter version is that in particular enters into the condition that the axes of the image sensor are orthogonal to each other. The more general case with 11 parameters allows shear between these two axes.
p0066In the method according to the invention the arrangement of X-ray markers in space is known. This may be the arrangement of all the X-ray markers of the X-ray marker device or a part of the X-ray marker. Preferably, at least the arrangement of those X-ray marker known define the invariant properties that are maintained at a projective mapping. Preferably, the known arrangement, at least 5, preferably at least 6 of the X-ray marker, which are in particular at least two planes and define at least two straight. The x-ray marker device meets the characteristics of the already above-mentioned X-ray marker device according to the invention.
p0067The aim of the process of the invention is to determine the correspondence between the X-ray markers and image markers, so as to obtain a prerequisite for the determination of the X-ray imaging geometry. Thus, in carrying out the process, the X-ray imaging geometry is unknown or not completely known. With respect to the imaging geometry is well known that it satisfies the conditions of the linear imaging, particularly of the projective image. (It is especially provided that the image has no distortion by the image intensifier. This is the case for C-arms with flat-panel detectors. In the case of conventional image intensifiers is preferably also a processing step of image rectification upstream.) The information is, however, not sufficient relative to determine the relative position of the X-ray source (especially the calculated X-ray source) X-ray marker to the device, in particular relative to the arrangement of the X-ray marker.
p0068The invariant properties, which are formed by the arrangement, include in particular the invariant straight lines, which are formed by the already above-mentioned straight line education credits. Here, the straight line formation include points that form a straight line of the invariant, as mentioned, is preferably at least one X-ray marker, preferably at least two X-ray markers.
p0069Invariant properties are herein particularly the aforementioned invariant straight lines, so device straights and in particular pyramid straight. In this regard also applies that if no aberrations occur, the number of lines that intersect at an intersection point, remains constant. In particular, a group of Straight Education points, in particular the X-ray marker by invariant line is thus possible. However, a grouping is also possible to intersections where intersect the straight line, ie, in particular the device-intersections and pyramid tips. It can thus be grouped according to the straight line intersection points, wherein the line in turn include image markers and x-ray marker. Another invariant characteristic is the preservation of neighborhood relations. That is, X-ray markers are adjacent to a device line, in particular pyramid straight lines, so this also applies to the corresponding X-ray markers picture markers on the device line corresponding image lines. This also means that a sequence of straight line forming points along a straight line, is obtained from an intersection of lines, for example. This means in particular that a Straight Education point which is close to an intersection, and another line forming point on the same device line that is farther away from the intersection, these conditions both with respect to the arrangement of the X-ray marker met in three-dimensional space, as well as in two-dimensional space with respect to the arrangement of the image marker on the device line meets appropriate screen line. a device marker 1 and a device marker 2 is positioned on a straight line and between the markers a device intersection, but no further X-ray marker, it can be seen in X-ray image, an image marker A and an image marker B which both sides are a screen intersection. Here, it is unclear whether the X-ray marker 1 is assigned to the image marker A or B. but distinguishing the number of X-ray marker along a device straight to two silks device intersection (especially the top of the pyramid), as an association of the device markers on the image markers is possible. Preferably, the number does not differ only by a X-ray marker, but to two or more X-ray markers, in order to ensure stability against artifacts. In the embodiment described below, the number of X-ray marker is on a side of the device intersection point zero, while it is on the other side of the device intersection second
p0070Another invariant characteristic is the above-mentioned cross-ratio, In particular, a group of Straight Education points, in particular X-ray markers and image markers after belonging to a cross ratio is possible.
p0071Generally speaking, therefore, the X-ray markers are grouped by at least one invariant property and the image markers are grouped according to the respective at least one invariant property. More particularly, this grouping according to the invention also includes the array of groups which emerge from an array of X-ray markers and / or marker image by the invariant properties. For example, X-ray marker, which lie on the same device lines, combined into one device line group and image markers which lie on a (selected) image-lines are combined into one image-line group. An example of this are the straight-line groups, which may be grouped into point of intersection groups. This inventive group, the number of possible permutations is reduced drastically. For it is then inventively a group-wise correspondence between the image markers and the x-ray markers. In particular, this group-wise assignment also includes the assignment between groups (eg device line groups), the X-ray markers (or groups derived therefrom) are inventively (invariant ie taking into account properties) derived, and groups (such as picture-line groups) the image of markers (or groups derived therefrom) are derived according to the invention. For example, the x-ray marker of a device lines are associated with the image markers of screen lines. This will in particular be excluded the possibility that the X-ray markers, which lie on a (single) straight, image markers which are located on different (or more) lines, can be assigned. As mentioned above, the number of possible permutations is drastically reduced by the grouping. The grouping according to the invention thus allows the calculation (or the attempt to calculate) the imaging geometry data is preferably carried out on assignment possibilities that arise after the grouping according to the invention. In particular, the grouping process according to the invention is designed so that groups that emerge from critical parts, ie each of the x-ray markers or image markers are grouped into higher-ranking groups. These higher-ranked groups can be combined into even higher-ranked group in turn. In the given example, the x-ray markers are grouped into device line groups and summarized the device straight line groups to device intersection groups. Ultimately, then preferably takes the assignment between the x-ray markers and image markers such that only those X-ray markers and image markers are associated with each other, the part of the same group, ie, the lowest-ranking group and all higher-ranked groups each comprising lower-ranking group. Preferably therefore possible assignments are sorted by the rank of the group. It is assumed that the number of groups with the highest rank is the lowest. In particular, the number of the highest ranking groups, based on x-ray markers, equal to the number of the highest ranking group based on image markers. In the example, thus the number of device groups intersection is in particular equal to the number of image-intersection groups. If the number is not equal to this as an indication of artifacts is preferably counted. This invariant property of the same number of groups of the same rank, which are each derived from the x-ray markers and image markers, especially for the lower-groups. Deviations from this invariant property of the same number of peer groups are preferably taken as evidence for artifacts. In particular, as well as artifacts can be identified.
p0072Preferably according to the invention all the lowest-device groups and image groups, in the example, the device straight line groups and the image-line groups are determined. In groups, are then preferably intended for the lowest-group mapping options. In determining the allocation possibilities preferably the aforementioned division into groups in higher-ranking and low-ranking groups are considered. It singles out one of the highest-ranking device groups, in the example of a device intersection groups and assigns them to one of the highest-image groups, in the example of the image-intersection groups. The singled out highest-device group includes low-ranking groups in the example device straight groups. Also thereof are accessed again out one of the low order apparatus group, in the example, so one of the device straight line groups and assigns them to one of the lower-image groups, in the example of the image-line groups. This assignment is permutatively for all members of the lower-group (all device line-groups) of the singled out higher-ranking group (device intersection group) to the respective lower-picture group (image-line group) of the singled out higher-ranking figure group (image-intersection group) performed permutatively. Here, particular attention all possible Pennutationen to determine all possible assignments. However, under certain circumstances, one may reduce the number of possible permutations here. For example, consider the assignment opportunities between members of a device straight line group and the members of an image-line group, so you can here in determining the allocation possibilities all possible permutations of the correspondence between the x-ray markers of the device straight line group and the image markers of the associated image-line group determined. As will be explained hereinafter, but it is possible with the aid of the light of the invariant properties, to reduce the number of mapping possibilities, so that it is smaller than the number of possible permutations. Contains for example, a device straight line groups of three members, three X-ray marker and an associated image-line group also has three members, three image markers, so there are three faculty possible permutations, ie 6 assignment options. Preferably, the groups determine the allocation options, taking into account the membership of an elementary group to a higher level group and taking into account the resulting invariant properties occurs. Among the considered invariant properties include in particular the already above-mentioned neighborhood relations and / or the cross-ratio. Assuming that a device straight line group includes, for example, four X-ray marker and this device line group is assigned to an image-line group to determine the allocation options, preferably the same number of image markers, that includes four image marker, result basically four faculty, ie 24 possibilities of assignment. Through the arrangement of the elementary group, so the device straight line group in upper-level groups, ie the intersection line group, is, as indicated above, it is possible by considering invariant properties, a drastic reduction of these mapping options between elementary groups. Preferably, only those selected by the given possible permutations as assignment options that satisfy these invariant properties. Since the device straight line group is a member of a device intersection group, taking into account the invariant neighborhood relationships can be determined that the intersection closest to the four markers, is second closest, located on the third and is located on the fourth succeeding (ie furthest is removed). Accordingly one can proceed for the image-line group. Also there is a sort of group members, so the image marker, made by its proximity to the image-intersection. This then means that is selected from the 24 permutations of only one. In this of the device intersection closest X-ray markers of the image intersection nearest image marker is associated with the next closest radiopaque markers associated with the next closest image markers, associated with the third-closest X-ray marker is the third nearest image marker and assigned the fourth-closest ray marker the fourth nearest image markers. For more x-ray markers would be continued accordingly. Thus, by using the invariant property of neighborhood relations in connection with the affiliation of the basic group to a higher group (here the intersection of sets) the number of predetermined by the permutations mapping options are drastically reduced. If, as selected in the given example, only one mapping option from the given permutations, so can optionally further be calculated for these remaining allocation possibility the double ratio when at least four Straight Education points are given. Is the cross-ratio for the selected routing facility agreed at least to a predetermined extent, the assignment option is fed to the next process step. For the next step of routing facility can also be directly transferred without calculating the cross-ratio after selection. In this next step imaging geometry data, if possible, for the selected mapping option calculated. But not that true cross-ratio conforming, the selected mapping option can be ruled out for the further method according to an embodiment. By excluding from allocation options thus the calculation amount can be further reduced. Because the amount of computation is considerably, in particular for the calculation of the imaging geometry data, and determining a correspondence between a real and virtual X-ray image.
p0073For the remaining, in particular selected assignment options imaging geometry data is calculated, the information about the X-ray imaging geometry, which allow in particular to calculate the position of the X-ray source relative to the X-ray marker device.
p0074In an attempt to calculate the imaging geometry data, based on the present invention certain assignment possibilities preferably an algorithm is used which already based on the above-mentioned principles of the pinhole camera. Reference is made in this respect again to the quotes above.
p0075Can imaging geometry data is calculated, so virtual x-ray images using the imaging geometry data and calculated based on the known configuration of the X-ray marker and the virtual x-ray images are preferably compared with the real X-ray image.
p0076If the result of the comparison is a match, at least to a predetermined extent, so it is assumed that the imaging geometry data is correct and thus the corresponding allocation option is correct. A match to a predetermined extent may be determined similar example for a least-squares fit method or. For example, a virtual x-ray image and a real X-ray image (same size) are superimposed and are determined the squared pixel distances between a virtual image marker and the associated real image marker for each image marker and are added up. If the sum is below a predetermined limit, it shall be deemed of sufficient compliance, it is about, then no sufficient match is given. Also can thus assess the different possible assignments carried out and that allocation option be chosen for the best match is given. This review may be supplemented and refined by comparison of other key figures.
p0077When evaluating a radiographic image, the image markers are identified. Preferably, they are recognized because of their shape and / or size and / or density. Nevertheless, it can happen that the image areas, which may constitute image markers and are hereinafter referred to as image marker candidates, no image markers. On the other hand, it may happen that this is not or not clearly visible in areas of the image, in which an image marker would be on display. Preferably, the method is designed based on the known arrangement and in particular their invariant properties to determine whether an image marker candidate is a figure marker or not. In particular, the information includes more than the known arrangement information on the number of X-ray marker along the device straight. This number also represents an invariant property because it is the number on a straight line and represent straight an invariant of projective mapping. The invariant properties allow it so inventively to identify image marker candidates as image markers or discard. In particular, it is also possible to detect when at a certain point, an image marker candidate should be seen in the picture, because there an image marker is expected but such image marker candidate does not exist. Generally, we can thus, based on the invariant properties detect artifacts in the image that are particularly missing image marker candidates or to be discarded image marker candidates. Preferably particular image marker candidates are determined as image markers, if they are located on a screen line, on which there is a minimum number of image marker candidates. This minimum is dictated by the device data. The minimum number is equal to the minimum number of X-ray markers to device lines. Preferably, it is considered according to the method assumes that a corresponding minimum number of image marker applies to the screen lines. Lying example, at least three X-ray marker on a screen line, it applies to the image marker. Lying example four straight form dots on a screen line, the (recognizable by the invariant number of intersecting lines) consists for example of an intersection, which corresponds to a pyramid tip and three image marker candidates, so can also be checked with the help of the cross-ratio, if it in itself the four image marker candidates are image markers. Even the cross-ratio represents an invariant property that can serve to distinguish correct and discardable image marker candidates.
p0078If you have a possible image-even identified on the radiograph, such as can be checked whether on these possible image-line the same number or minimum number of image marker is, as there are on the corresponding device straight X-ray marker. According to a preferred embodiment, the number of the X-ray markers on the Vornchtungs straight two or more than two, for example three or four or five. The number of straight line forming points is preferably three or more. If one recognizes now a straight line in the X-ray image, which is formed from an intersection of lines and an image marker candidates, so you can in a preferred embodiment then set this image marker candidates as image markers, if there is another image marker candidate on this line, if so, at least one selected from the device data derived invariant properties, so for example, the minimum number of straight line forming points to device lines and is thus also meets on-screen line. Preferably therefore image marker candidates are recognized as image markers, when they are located on a straight line, on which there is a total of a minimum number of image markers and / or image marker candidates. The minimum number is preferably 2, 3, 4 or more. The minimum number corresponds in particular the minimum number of X-ray markers to device lines.
p0079Preferably image marker candidates are determined as image markers, if they are located on a screen line, which intersects with a predetermined minimum number of different screen lines. Even this minimum number is determinable from the device data invariant property. In this example, such an image-line at least a Straight Education point, which is an image-intersection in which a predetermined minimum number of screen lines intersecting. Preferably, this minimum number of screen lines, which intersect in the image intersection, greater than 2 or 3, ie, for example 3, 4 or 5. In particular, the line formation is not identical with an image marker. In particular, the number of intersecting image straight is less than the minimum number of device lines that intersect at the location of any X-ray marker. In the example shown, the<figref idrefs="f0003">figure 3</figref> This is the number of x-ray marker minus 1. Also, such minimal number is an invariant property and can be used as the upper limit for the identification of image-points of intersection correspond to the pyramid tips. So is the number of intersecting in an image intersection lines greater than or equal to the given minimum number and less than this upper limit, the image-intersection can be determined as a pyramid tip accordingly.
p0080Preferably, the invention further relates to a navigation method, which comprises one of the aforementioned methods of the invention for determining a mapping between the X-ray markers and marker images. According to the navigation process of the invention by the determination of the invention that one of the allocation options is correct, the use of the correct allocation option corresponding imaging geometry data in order to determine the position of an object in the X-ray image. When determining the position of the object in the (two-dimensional) X-ray image, the three-dimensional position of the object is used. For this purpose, the navigation methods are provided preferably subject location information (three-dimensional position data) are available, which describe the position of the object in space. This location data can be detected for example by means of a detection device, which is a component of a navigation system. For example, the article comprising a navigation marker device, which is detectable by the detection device. Is the three dimensional position of the object are known, and the imaging geometry data is known, then there is sufficient information to calculate the position of the X-ray source relative to the object can. This information thus allows the calculation of the figure of the object in the radiograph. It can therefore be calculated virtually and using data that describe the X-ray image as the object would represent the radiograph, if he had taken in the X-ray machine, the position represented by the three-dimensional location data (subject position data) are given. In other words, a virtual x-ray imaging of the object is virtually carried out under the same conditions, as was the case in the real x-ray imaging. The location of the subject in this virtual x-ray imaging is determined by the subject location data. According to another embodiment of the navigation method, the virtual x-ray imaging can be displayed correctly when the X-ray machine has moved relative to the patient since the production of real X-ray image. In this further embodiment, a navigation marker device on the patient is positioned so that it is preferably fixed relative to at least part of the body structures shown in the X-ray imaging. The imaging geometry can thus be determined relative to a reference system in which lie the body structures. In particular, the imaging geometry data for this reference system can be determined as they were given at the time of the actual X-ray image. Can thus be calculated relative to the patient and after a movement of the X-ray apparatus, such as the subject in the case of a virtual x-ray imaging would constitute (for a virtual non-moving X-ray apparatus). In particular, the virtual shape and / or size and / or position of the object can be determined and displayed in the virtual x-ray image.
p0081Also navigation marker devices may be attached to the X-ray apparatus according to a further embodiment, particularly of the unit which includes the X-ray source and the unit which includes the X-ray detector. Thus, by evaluation of the X-ray image by the inventive process, so the imaging geometry data and the X-ray marker device layer data, the imaging geometry are calculated based in a reference system of the navigation system. In particular, the position of the X-ray source and the position of an image plane in the reference system and in particular can be calculated relative to the mounted on the X-ray unit navigation marker device. In this way can be prepared by the invention determine the imaging geometry data without the x-ray marker device of the invention, for example, in the investigation of another body structure by means of X-ray machine, virtual x-ray images are calculated, in which the article appears virtually.
p0082The present invention further relates to a program that, when run on a computer, causes the computer the steps of the inventive method to carry out in particular a method and the navigation method described above. in particular, the computer includes a processor and a memory. In particular, interfaces are further provided to supply the data as necessary for the implementation of the process information to the computer. These are in particular data on the arrangement of the X-ray marker in the X-ray marker device (device data) and data which describe the X-ray image (radiographic image data). If the program performs the navigation process, the subject location data and in particular patient data is more preferably (see below) fed to the computer. The data describing the arrangement of the X-ray marker in the X-ray marker device are herein also referred to as device data. in particular the device data include information about the relative position of the X-ray marker device wherein the relative position is predetermined by the arrangement of the X-ray marker in the X-ray marker device.
p0083The X-ray image data describing the x-ray image at least partially. In particular, they describe the position of the marker images and / or of possible marker images (marker image candidate) in the radiograph. The device data thus include information about the relative position of the X-ray marker while the X-ray image data information on the relative position of the image markers include. The relative position of the X-ray marker describes invariant properties that are maintained at a projective X-ray imaging and which are reflected in the relative position of the image marker.
p0084Additional data that can be fed to the computer, the patient data, which describe the position of the body structure shown in the radiograph. Patient data are obtained in particular by means of the navigation system which detects a navigation marker device, which is fixedly connected to the body structure.
p0085The program may be stored in a program memory (for example, CD or ROM) or in the form of a signal wave, which is transferable in particular on the Internet, and contains the information that represents the program to be shown. The invention is also applicable to these memory or form of presentation, each of which contains the program that directed.
p0086The invention is further directed to a navigation system. This particular comprises a computer to which the program is loaded or running. In particular, the computer includes a processor to perform the method steps and a memory for loading the program. As an interface, a data input means is provided to enter the X-ray image data and the device data in the computer. The navigation system further preferably includes a detection device to detect navigation marker devices. Preferably, one attached to the x-ray marker device navigation marker device is detected. also in (at least) is preferably detected an object mounted navigation marker device. In particular, a affixed to a body structure of a patient navigation marker device is detected. The program running on the computer of the navigation system is designed based on calculated on the detected position of the x-ray marker device and the detected position of the object, as the object would represent the radiograph if he would be irradiated in accordance with the imaging geometry data of X-rays wherein the imaging geometry data of the specific assignment to be correct match. Preferably navigation marker device data is stored in a memory, containing the relative position of the various navigation markers detected devices to the object on which the navigation marker devices are mounted. This can be determined by detecting the position of the navigation marker device the location of the object. For example, therefore, the relative position between the navigation device, the marker is attached to the article, and the article is stored. Further, the relative position between the navigation marker device, which is attached to the X-ray marker device, and the X-ray marker device is stored. Such data may be as described, stored, or may be supplied to the navigation system, for example via a data interface.
BRIEF DESCRIPTION OF THE FIGURES
p0087<dl id="dl0001" compact="compact"><dt>figure 1</dt><dd>shows schematically the construction of a navigation system according to the invention;</dd><dt>figure 2</dt><dd>schematically shows the mapping of an X-ray marker device by means of an X-ray apparatus;</dd><dt>figure 3</dt><dd>schematically shows the three-dimensional array of x-ray markers of X-ray marker device; </dd><dt>figure 4</dt><dd>showing the relative position of image markers in an X-ray image of the X-ray marker device of <figref idrefs="f0003">figure 3</figref>;</dd><dt>figure 5</dt><dd>shows the determination of image-intersections in the X-ray image corresponding to the pyramid tips;</dd><dt>figure 6</dt><dd>shows in perspective an X-ray marker device;</dd><dt>figure 7</dt><dd>shows the device intersections of the x-ray marker device of <figref idrefs="f0006">figure 6</figref>, The pyramid tips are.</dd></dl>
DETAILED DESCRIPTION OF THE FIGURES
p0088<figref idrefs="f0001">figure 1</figref> schematically shows an inventive navigation system with an X-ray device 100 (a C-arm) having an x-ray source unit 110 and an X-ray detector unit 120 comprises (for example, image intensifier). The X-ray light from the x-ray source unit 110 radiates through from top to bottom an object 400 (for example instrument, in particular scalpel), the X-ray marker inventive device 500 and the patient 200 on the object 400, a navigation marker device 410 is mounted. At the X-ray marker device 500 a navigation marker device 510 is mounted. At the patient 200 a navigation marker device 210 is mounted. The X-rays are detected in the X-ray detector unit 120 and generated by the X-ray detector unit radiograph 120 is supplied to the computer 300th A display device 320, which is connected to the computer 300, can image data, in particular for the image-based navigation or x-rays, in particular also view the virtual x-ray image. The computer 300 can be further supplied to the detection signals from the detection device 600th The detection device 600 detects signals from the navigation marker devices 410, 510 and 210, in particular by means of two separate cameras. The detection signals of the detection device 600 are the computer 300 is supplied, so that it can with a navigation program determine the location of the object 400, the X-ray marker device 500 and the patient's 200th In particular, a database contained in the computer is used, in which the relative position between the navigation marker devices and the objects, eg parts, in particular surfaces or tips or ends of the object 400 and the relative position between the X-ray markers and the navigation marker device stored 510th In particular, unknown is the positional relationship between the navigation marker device 210 and the body structures of the patient 200, which can be seen on the radiograph. The navigation system according to the invention allows, in particular illustrate how the object 400 would represent in the X-ray image (particularly its top), even when the X-ray unit is 100 away from the patient and the x-ray marker device 500 is also removed. If the patient moves 200 after the generation of the radiograph not, the representation of the object 400 in a virtual x-ray image would be possible without the navigation marker device 210th Through the use of the navigation marker device 210, which is preferably fixedly connected with the body structures that are mapped in the x-ray image, it is possible to determine the relative location between the subject and the patient, even after movement of the patient after generation of the X-ray image.
p0089<figref idrefs="f0002">figure 2</figref> schematically shows an X-ray imaging. In this X-ray imaging an X-ray image generated by X-rays from a point x-ray source 112 (the position by the inventive process can be calculated) out of the X-ray source unit 110 and impinge on an X-ray image plane 122 of the X-ray detection unit 120th Towards the X-ray image plane 122, the X-rays radiate through 114, 115 the object 400, the X-ray marker device 500, the x-ray marker 501, 502 circular illustrated and further not provided with reference numerals circular X-ray marker comprises. Thereafter, the X-rays irradiate a body structure 200 of the patient. This body structure a navigational marker structure 210 is fixedly connected. The x-ray marker 501 generated in an X-ray image that is in the X-ray image plane 122, an image marker 500A. Another x-ray marker 503 generated in the X-ray image a marker 500C. The dashed line 114 and 115 denotes schematically an example of the X-rays.
p0090More particularly, the invention relates to the association between image markers, such as 500A and 500C and X-ray markers, such as 501 and 503. Do we know what Röntgennarker attributable which image marker, it can be from this the position of the point x-ray source 112 determine. If the image marker 500A associated with the x-ray marker 501 and the marker image 500C of the x-ray marker 503, so you can put a line through each of the x-ray marker 501 and the marker image 500A and the x-ray marker 503 and the marker image 500C. The position of the x-ray markers 501 and 503 is determined by detecting the navigation marker device 510th The intersection of this line still coincides with the position of the point x-ray source.
p0091This is only a general description of the mathematical details (algorithms) that take into account the principle unknown location of the X-ray image plane 122, in particular image marker 500A and 500C relative to the x-ray marker device 500 and the knowledge of this position to calculate a virtual x-ray image that is would result in a known position of the X-ray source 112 and the image plane 122, not require, the pinhole camera principle regarding described in the citations above. The application of this mathematical details, particularly algorithms, allows the determination of the imaging geometry data comprising ausrechend information to calculate the virtual x-ray image. In this context, particular reference is made to the above-mentioned publications of Tsai. It describes a special way to win the calibration of the pinhole camera, which is often regarded as the standard. The thesis of Yaniv is an example of the application of such a calibration on a fluoroscopy system.
p0092Assuming that the position of the X-ray source is known, can be calculated, for example, which pixels of the object would generate 400 the radiograph. In particular, can thus be calculated, where and with what form and / or size of the object would be displayed 400 in the radiograph. This can be set in particular in relation to an image of the body structure 200 in the X-ray image and are shown in the virtual x-ray image is superimposed on the body structure with the virtual x-ray image of the object.
p0093As schematically above with reference to the <figref idrefs="f0002">figure 2</figref> explained, thus a correct correlation of x-ray markers and image markers is essential. According to the finding of a correct allocation is easier. As this is facilitated according to the invention, is in reference to the<figref idrefs="f0003">figure 3</figref> explained. <figref idrefs="f0003">figure 3</figref> represents a possible and preferred arrangement of the X-ray markers of the X-ray marker device.
p0094<figref idrefs="f0003">figure 3</figref> schematically shows the three-dimensional arrangement of physical x-ray markers 1 to 8. The X-ray marker 1 to 8 are an integral part of the registration body and have a fixed position to one another. The X-ray markers lie on the side edges of three pyramids, which have the peaks P1, P2 and P3. The peaks P1, P2 and P3 are located in the three-dimensional space and are preferably virtually. The X-ray marker 2, 3, 6 and 7 define the base of the pyramid with the peak P1. The X-ray markers 1, 2, 3 and 4 define the base of the pyramid with the point P2 and the x-ray markers 1, 2, 5 and 6 define the base of the pyramid with the point P3.
p0095The positions of the X-ray markers are characterized by a plurality of geometric properties. In particular, the X-ray markers lie on side edges and base edges of the pyramids. Is herein some talk that an X-ray marker or image markers (or its location) is located on a straight line or edge or point or a point, it is hereby in particular, that the geometric center of the X-ray marker or image marker fulfills this condition. The Pyramids preferably have at least three sides. In the example shown, there are four side surfaces. The geometric characteristics facilitate the mapping between the physical x-ray markers 1 to 8 in three-dimensional space and the images of the X-ray marker (hereinafter referred to as "image marker") in the two-dimensional X-ray image. In particular, artifacts can be detected and it can be determined that the physical x-ray markers corresponding image marker is missing. For in the<figref idrefs="f0003">figure 3</figref> shown device lines V1 to V 12 is continuous around pyramids straight. The sections form the pyramid straight lines pyramid edges, in particular side edges and / or base edge, bounded by X-ray markers in the illustrated embodiment. This is preferred but not mandatory.
p0096The aforementioned geometrical properties are, for example, when the X-ray marker 1 the following: the X-ray marker 1 is part of the base edge (exactly at a corner of the base) of the pyramid with the point P3. The X-ray marker 1 is located on the pyramid straight lines V1, ie on the pyramid side edge with endpoints x-ray marker 2 and peak P1 and the X-ray marker 1 defines a corner of the base of the pyramid with the point P2. Corresponding geometric properties, namely corner of the base of two pyramids and a component of a pyramid side edge has the X-ray marker. 3
p0097The X-ray marker 2 is at a corner of the base of all three pyramids (with peaks P1, P2 and P3). The X-ray marker 4 is at a corner of one of the three pyramids (pyramid peak P2) and is part of two side edges of two pyramids, namely the side edge of 1 to P3 and from 3 to P1.
p0098For instance, the X-ray marker 8 on any single area of a base area of the three pyramids, but is part of three side edges, namely side edges of 7 to P1, and from 4 to P2, as well as of 5 to P3.
p0099In the example shown, the position of each X-ray marker, preferably a component of a pyramid straight lines of each of the three pyramids in the example shown even the edges of the pyramids (side edge and / or base edge). The geometric characteristics, accurate pyramid lines containing edges of the pyramids, define abbildungsinvariante properties, namely straight lines in the perspective images (X-ray imaging) remain invariant, that are mapped back on line.
p0100Overall, the position of all X-ray markers therefore have multiple geometric and in particular invariant properties. In the example shown, they each lie on three invariant lines that allow for the later calculation algorithm in a mapping between the (physical, three-dimensional) X-ray markers and the (two-dimensional) image markers. Another invariant property, the neighborhood relations of the X-ray marker, the marker 1 of the pyramid tip P1 is closer than the marker 2 and the marker 5 of the pyramid point P2 closer than the marker 1. Such features which sort the X-ray marker according to their proximity to the pyramid tips, also retained, ie the image is the same sort results according to the proximity of the image-intersections that match the pyramid tips.
p0101In particular, by the use of invariant properties, it is possible to customize the algorithm efficiently to shorten the computation time dramatically.
p0102As already stated above, the subject X-ray marker in the generation of X-ray image geometrically considered a projection, as a result, the two-dimensional image is generated with the image markers. Radiographs may be distorted, if earlier conventional image intensifiers were used with a curved detection surface, or be free of distortion, if newer flat-panel image amplifiers are used. Herein, it is assumed that distorted radiographs are equalized by a conventional process. Which derive from the radiographs and processed radiographic image data are thus preferably without distortion. As was also mentioned, is an essential aspect of the invention is that geometrical properties of the marker assembly can be exploited that are invariant under a geometric projection. Among the above enumerated properties include, in particular, that lines are mapped to straight lines, which are also referred to herein as a invariant straight. As mention above, each of the X-ray marker is preferably located on a pyramid corner or on one side edge between a base surface area and the top of the pyramid and thus part of a pyramid is precisely defined by three points or the X-ray marker is positioned at a corner of a pyramid and thus also part a pyramid straight line which is defined by the top of the pyramid and a further X-ray marker between the top of the pyramid and the base surface area. Overall, therefore, go through an x-ray marker in the example shown three pyramid straight lines which are defined by some other X-ray markers and a top of the pyramid. Since, as mentioned, be represented by a projection straight on straight lines, is the finding of image markers in the two-dimensional image, which physical x-ray markers can be assigned, easier and faster.
p0103The X-ray marker 1 to 8 may show up in an X-ray image by image markers A, B, C, D, E, F, G and H. These are by black circular areas in<figref idrefs="f0004">figure 4</figref> shown. According to the inventive method will now be clarified which of the X-ray marker 1 to 8 wherein the image marker A is assigned to H. In particular, these are according to the two-dimensional X-ray image<figref idrefs="f0004">figure 4</figref> preferably all image markers A to H interconnected by screen lines. In each image marker thus cut seven lines (number of image marker minus 1). In addition to these image-intersections there are more image-intersections, where usually only two lines intersect at a point (see<figref idrefs="f0004">figure 4</figref>). Apart from these picture-intersections, however, there intersections S1, S2 and S3, in which more than two lines intersect precisely, four lines. This picture-line B1 to B12 correspond to the pyramid straight lines V1 to V12.
p0104As mapped at a geometric projection straight on straight lines, hence intersections of lines are mapped to intersections of lines. As also cut into the pyramid tips P1, P2 and P3 each four lines, one can assume that they are images of the pyramid tips P1, P2 and P3 in the image intersection points S1, S2 and S3. Here, however, is not yet clear which Pyramidenspitze P1, P2, P3 which intersection S1, S2, S3 is assigned. The number of intersecting in the picture-intersections straight ie lies between the minimum number, which in an image markers intersecting straight (number of x-ray marker minus 1) and a maximum of chance in an intersection intersecting straight (number typically two, perhaps, and very rarely three, depending on the accuracy of the image resolution). The x-ray marker device is therefore preferably designed so that the number of intersecting in a pyramid tip pyramid lines meet these conditions.
p0105The intersections S1, S2 and S3 corresponding to pyramid tips, allow an orderly search for an association between the image markers A to H and the physical x-ray markers 1 to 8. The number of allocation can be reduced considerably by the knowledge that the points of intersection S1 representing S2 and S3 images of the pyramid tips P1, P2 and P3. Without such a child looking for the correct correspondence, based on the geometrical characteristics of the physical arrangement of the X-ray marker, in particular taking into account the projective geometric characteristics of the arrangement finding the correct assignment would be considerably more time-consuming. For 8 marker spheres, there are eight different ways of faculty assignments for which a candidate projection image may have to be calculated and then this would have to be compared with the actual X-ray image. In the case of 8 marker spheres ie 8 Faculty and thus 40,320 candidates projection images to be calculated and compared with the actual image. In the presence of artifacts in the image, which can not be distinguished from the marker images, the combinatorial complexity continues to increase, as well as combinations must be considered, which contain one or more artifacts. This computation can be shortened considerably by the following described with an example mapping method.
p0106This one uses the invariance of for perspective pictures that line are mapped to line. For example, if a pyramid point at the intersection of n lines, n has a side edge, we obtain the radiograph an intersection of exactly n lines, if all image markers have been found and no artifacts are to be considered. If not all image marker found that form the lines that intersect at the intersection, which corresponds to the top of the pyramid, so can cut less n lines at the intersection. By mapping of lines on straights and the neighborhood relationships between points remain on line. Thus, for example, in<figref idrefs="f0003">figure 3</figref> the X-ray marker 5 between the point P1 and the X-ray marker 6. In order for the image from the X-ray marker 5 is also within the X-ray image (ie image marker 5) between the found by the intersection of picture of point P1 and the image from the X-ray marker 6 (ie image marker 6) on the by the image of the point P1 and the image X-ray marker 6 defined precisely. In the described embodiment, the pyramid tips exist only structurally but not physically. Also is the X-ray marker 4 between the X-ray marker 1 and the point P3. Thus, the image from the X-ray marker 4 between the image from the X-ray marker 1 and the image of the point P3 on the line defined by the image of the X-ray marker 1 and the image of the point P3 is located. If you use from this, one can proceed as follows:
p0107If you use the invariant properties, so you can exclude those picture-line that match no pyramids straight, so that from the in <figref idrefs="f0004">figure 4</figref> shown situation the clearer, in <figref idrefs="f0005">figure 5</figref> Situation shown results, with reference to the further procedure is explained.
p0108It is assumed first that the intersection of S1 in the two-dimensional image on the pyramid tip P1 matches.
p0109S1 ast the intersection of straight lines which are defined by the following image marker pairs (A, B); (E, F); (H, G); (D, C). To use the aforementioned obtained neighbor relationship, the one image marker was up in the parentheses is listed first, which is the intersection S1 closest and then the more distant.
p0110Comparing the situation in <figref idrefs="f0004">figure 4</figref> with the <figref idrefs="f0003">figure 3</figref> and one follows the assumption made above, that the intersection S1 corresponds to the pyramid tip P1, as defined by the physical marker lines were as follows: (1, 2); (5, 6); (8, 7); (4, 3).
p0111Even with the newly listed name the line each one physical X-ray marker was called first, which is the point P1 closest.
p0112In the example above, there is a maximum of 4 !, ie 24 ways to make the four image marker pairs (A, B); (E, F); (H, G); (D, C) one image pair of markers from the physical x-ray marker pairs (1, 2); (5, 6); (8, 7); (4, 3) to assign. One can also speak of 24 possible bijective maps between the amount of image marker pairs and the quantity of X-ray marker pairs here. For example, the image marker pair (A, B) associated with the physical marker pair (5, 6), this means that the picture marker A is assigned to the physical X-ray marker 5 and the image marker, B the physical x-ray marker 6. An assignment of marker image A to the physical x-ray marker 6 and the image B to the physical marker 5 X-ray marker is not possible since, as indicated above, remain the neighborhood relationships. each of the first image of an image marker marker pair of first physical x-ray marker of a physical marker pair is thus allocated and assigned to the second image marker of an image marker pair the second physical x-ray marker of a physical marker pair. This limits the number of ways a strong.
p0113The above permutations of bijective maps between the physical x-ray marker pairs and the image marker pairs each provide possible solutions. For each possible solution (bijection) known principle of the pinhole camera is using an algorithm mentioned in the above, is based, according to a mathematical solution to the problem sought. That is, it is checked whether the given solution possibility imaging geometry data, the information on imaging parameters of the camera model, ie the external imaging parameters that describe in particular the position and orientation of the radiation source in the world coordinate system (in particular relative to the x-ray markers), as well as the internal include imaging parameters, can be calculated using algorithms. It may arise that no data can be calculated using the algorithm. This means then that the solution might be wrong. It can however also calculate data. Whether this data represents a correct solution can then be checked. The data contain information on the position of the radiation source relative to the three-dimensional arrangement of the X-ray markers as well as other internal imaging parameters, according to the selected camera model. They thus allow a virtual radiographic dimensional arrangement of markers, so as virtually to generate a two-dimensional image with image markers. Does the relative position of the virtual image markers in this virtual two-dimensional image, at least within a predetermined error frame with the relative position of the real image marker in the real two-dimensional X-ray image coincide, an acceptable solution might be found. If this is not the case, the possible solution should be discarded.
p0114The above method to check whether a possible solution (permutation) is correct, is, at least if there is no right (correct) solution option was found, carried out for all possible solutions or terminated if a right (correct) way was found. Preferably all other possible combinations are examined to possibly find an even better solution possibility. The best possible solution is then regarded as the correct assignment. It is possible to extend the assessment of a possible solution found by other typical characteristics of the calculated figure to be considered, as certain values or ratios of the internal imaging parameters.
p0115Could the possible permutations concerning any possibility right solution be found a point of intersection (in the given example, the intersection of S1), so the inventive method to the next assumption proceeds. According to the next assumption corresponds to the intersection of S1 Pyramidenspitze P2.
p0116For this constellation there are the following possible physical marker pairs: (5, 1), (6, 2), (7, 3), (8, 4).
p0117This physical marker pairs can then be assigned as solutions the above image marker pairs in the manner described above. There are thus in turn 4 !, ie 24 possibilities.
p0118If this in turn leads to no solution, then it is assumed in the next step, that the intersection S1 corresponds to the pyramid tip P3 and again wanted analogue for 4 !, ie 24 possible permutations for the solution.
p0119Preferably, one starts with that intersection, which is located farthest away from the image marker in the image plane. In the in<figref idrefs="f0004">figure 4</figref> the example shown would S3 this. Performs mapping of S3 to P1, P2 and P3 are not successful, it would then go to the nearest intersection S1. For this case, the above permutations were explained. Thus, it was successively assumed that the intersection point S1 the pyramid point P1, P2 and P3 corresponds to the end, as has been described above by way of example. As a final would then be searched by means of S2 after a possible solution by assuming that the point of intersection S2 sequentially to the pyramid point P1, P2 or P3 corresponds.
p0120<figref idrefs="f0006">figure 6</figref> shows an embodiment 550 of an x-ray marker device. This embodiment is oblong shaped with a from an in<figref idrefs="f0006">figure 6</figref> shown left end 552 to a right end 554 widening U-shaped cross section. In the direction of broadening is the right side wall 560, which represents one arm of the U's. In the center is a medium in which<figref idrefs="f0006">figure 6</figref> overhead sidewall 562 and left is a side wall 564. The left and right side wall ever further apart the farther they are from the middle side wall. The X-ray marker device preferably comprises an X-ray comparatively permeable material, such as carbon, which serves as a carrier for the x-ray marker 571, 572, 573, 574, 575 and 576 and for the navigation markers 581, 582, 583 and 584th In particular, the side walls of this material are formed. In particular, thin side walls (wall thickness smaller than the diameter of the X-ray marker) the x-ray markers are preferably embedded. The side walls and / or the X-ray markers are in particular optically opaque. The navigation markers 581-584 together form a navigation marker device. The navigation markers are arranged in the embodiment shown on the central side wall 562nd In the longitudinal direction of the x-ray marker device they are at the other end as the X-ray marker. Preferably, they are arranged in this or in other embodiments, in particular outside a range which is limited by the X-ray marker. To the previously mentioned x-ray markers 571 and 576, which are supported by the right side wall 560, there is another corresponding 6 X-ray markers 591 to 596, in the<figref idrefs="f0006">Fig. 6</figref> are indicated as dotted circles. These corresponding 6 are X-ray marker, when the central side wall 562 by a vertical plane (not shown) divides the mirror image of that plane in the side wall 564 arranged. The arrangement of a total of 12 X-ray marker forms a truncated pyramid arrangement similar in the<figref idrefs="f0003">figure 3</figref> arrangement shown. The respective outer markers of three arranged in a row markers, lying on the side edge of each three pyramids. Like the pyramids are formed, is in<figref idrefs="f0007">figure 7</figref> to see. The tips of the three pyramids are denoted by P4, P5 and P6. For example, pyramid straight lines passing through the X-ray marker pairs (573, 576), (572.575), (571, 574) meet; (591, 596), (592, 595), and (593, 594) are formed in the top of the pyramid P4.
p0121Preferably, the side wall (left, middle or right side panel) is in particular in the area where there are the X-ray marker, at least partially interrupted, so as to maintain an attenuation of x-rays to a minimum.
p0122The invention described above referring by way of example to the case of forming an image (X-ray image) of a marker device (X-ray marker device) by means of an imaging device (X-ray machine) which generates an image (X-ray imaging) under the laws of the linear mapping. General shall define the case of generating a radiation image of a radiation marker arrangement by means of a radiation imaging device that produces a ray imaging according to the laws of the linear mapping. The radiation imaging apparatus includes a radiation source (eg, x-ray source or light source) and a radiation detector (eg Röntgendetekor or light detector) which detects the radiation image of the radiation marker device. The present invention thus relates generally to the use of any electromagnetic radiation, in particular infrared rays, visible light rays and ultraviolet rays. Thus, generally, the present invention relates to a radiation marker device with radiation markers (eg X-ray marker device or light marker device), the electromagnetic radiation of a determined type (eg, X-rays or light rays) can not, or at least greatly attenuate. Subject radiation marker device visible light, so, for example, light markers, ie opaque markers (eg spherical) are carried by a support of this type of electromagnetic radiation transparent material (eg glass) and can be arranged according to the invention. focus Thus, generally, the present description, the following device:
p0123Rays marker device having an array of beams markers, wherein the assembly defines straight lines that are referred to as device lines, wherein at least a part of the device straight lines which are referred to as pyramids straight, portions that define at least the edges of a pyramid.
p0124Accordingly, the description relates generally to the following procedure:<ul><li>A method for determining an association between radiation markers of radiation marker device and marker images of a radiation image, which results in a given imaging geometry by a beam imaging the radiation marker device, wherein the marker images representing the radiation markers in the radiation image,</li><li>and wherein in addition to radiation image data including information on the relative position of the marker images in the optical image, device data are provided that describe the relative position of the radiation marker, and the relative position of the radiation marker describes an arrangement having the invariant properties that during the radiation preserved picture and include the invariant straight lines,</li><li>the method comprising the steps of:<ol><li>a) based on the radiation image data and the device data marker images and radiation markers are grouped in each case taking into account the invariant properties of the assembly;</li><li>b) groups the assignment possibilities of the marker images and radiation markers are determined;</li><li>c) if imaging geometry data for radiation imaging can be calculated for the allocation options, virtual ray images are determined based on the calculated imaging geometry data and the virtual ray images are compared with the real-ray image;</li><li>d) is at least one match between a particular virtual and a real ray image to a predetermined extent, the possibility of assignment to certain rays underlying image is recognized as correct.</li></ol></li></ul>
p0125General concerns the description of course, a program that, when run on a computer, causes the computer to perform the steps of the above method.
p0126In general, the disclosure described herein should be construed that the term "X" is replaced by "radiation". Here, the term "radiation" some form of electromagnetic radiation. The radiation image is the image that is generated by this radiation. An example of the radiation image is the X-ray image or an image produced by photo.
Contents2
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Every citation, both ways
| Document | Relation | Office | Cited during |
|---|---|---|---|
| WO2018127501A1 | Cited by | World Intellectual Property Organization (WIPO) | Applicant |
| WO2018127501A1 | Cited by | World Intellectual Property Organization (WIPO) | Applicant |
| EP0853920A | Cites | European Patent Office (EPO) | – |
| DE19703556A1 | Cites | Germany | – |
| US6044132A | Cites | United States of America | – |
| US2005109855A1 | Cites | United States of America | – |
| US2005113682A1 | Cites | United States of America | – |
| US2007122020A1 | Cites | United States of America | – |
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| SORENSEN ET AL: "Image-guided radiotherapy using a mobile kilovoltage x-ray device" MEDICAL DOSIMETRY, ELSEVIER, US, Bd. 31, Nr. 1, 18. März 2006 (2006-03-18), Seiten 40-50, XP005864688 ISSN: 0958-3947 | Non-patent | – | – |
| YANIV ET AL: "Fluoroscopic image processing for computer aided orthopaedic surgery" MICCAI'98 LNCS, Bd. 1496, 1998, Seiten 325-334, XP002520019 | Non-patent | – | – |
6 members in 2 offices
Priority claims1
| Document | Office | Kind | Date |
|---|---|---|---|
| 08162808 | European Patent Office (EPO) | A |
Members6
| Document | Office | Kind | |
|---|---|---|---|
| EP2156790A1 | European Patent Office (EPO) | A1 | |
| US2010046718A1 | United States of America | A1 | |
| EP2245986A1 | European Patent Office (EPO) | A1 | |
| US8104958B2 | United States of America | B2 | |
| EP2156790B1 | European Patent Office (EPO) | B1 | |
| EP2245986B1This record | European Patent Office (EPO) | B1 |
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Numbers
- Publication
- 2245986
- Application
- 101702751
Titles3
- German
- Pyramidenförmige Röntgenmarkervorrichtung
- English
- Arrangement of x-ray markers in the form of a pyramid
- French
- Arrangement de marqueurs de radiographie en forme de pyramide
Classification
- CPC, 13
- A61B90/39
- A61B5/1127
- A61B6/12
- A61B6/583
- G06T2207/10116
- G06T2207/30208
- A61B2090/3983
- A61B2034/2055
- A61B2090/3995
- A61B34/20
- A61B2090/376
- A61B2090/3966
- G06T7/73
- IPC, 1
- A61B6 00
Designated states34
- Contracting states, 34
- Austria
- Belgium
- Bulgaria
- Switzerland
- Cyprus
- Czechia
- Germany
- Denmark
- Estonia
- Spain
- Finland
- France
- United Kingdom
- Greece
- Croatia
- Hungary
- Ireland
- Iceland
- Italy
- Liechtenstein
- Lithuania
- Luxembourg
- Latvia
- Monaco
and 10 moreShow fewer
- Malta
- Netherlands (Kingdom of the)
- Norway
- Poland
- Portugal
- Romania
- Sweden
- Slovenia
- Slovakia
- Türkiye
