DE102008049569A1 - Method for image-based motion correction i.e. breathing motion correction, in two-dimensional radioscopy image during medical needle intervention of patients, involves visualizing fluoroscopy images such that images are corrected - Google Patents

Abstract

The method involves determining motion of patients in the form of translation and rotation from two-dimensional (2D) images in viewable fluoroscopy images (27) during medical intervention of patients. Virtual elongations of the fluoroscopy images are evaluated for searching processes in different fluoroscopy images or frames. A virtual rotation center (Z) is determined by sectioning of the elongations. The fluoroscopy images together with three-dimensional (3D) images are visualized such that the 3D-images and/or the fluoroscopy images of the evaluated shift are corrected accordingly.

Description

The The invention relates to a correction method for movement correction in a two-dimensional fluoroscopic image during imaging during a medical intervention of a patient.

While a medical intervention will be used to navigate the Instruments for example in the abdomen with the help of fluoroscopic Transillumination real-time images created. Compared with 3-D angiography images Although these two-dimensional fluoroscopic images do not show any spatial (3-D) details, but they are available more quickly and minimize the radiation exposure for patient and doctor. Ideally, the spatial information is now recovered that preoperatively recorded 3-D images of CT, angiographic or MR sequences with the two-dimensional ones Transmitted fluoroscopic images are registered and underlaid. The combination of co-registered 2-D and 3-D images allowed the doctor now a better orientation in the volume. This 2-D / 3-D registration consists of two steps.

In image registration, it must first be determined from which direction a 3-D volume must be projected so that it can be brought into line with the 2-D image. For this purpose, there are various known approaches that are irrelevant to the inventive design of the method. Examples of suitable registration techniques can be found in A. Oppelt (ed.): Imaging Systems for Medical Diagnostics, pages 65 to 82, Publicis Publishing, Nov. 2005 ,

The second problem is the visualization of the registered images, d. H. the common representation of 2-D and projected 3-D image. The standard method for this is the so-called "overlay", in which the two images are superimposed by various possible methods become.

A problem of 2-D / 3-D registration, especially in abdominal applications, such as liver punctures or navigation in the hepatic vasculature, is that the 3-D images are static, ie in a particular respiratory phase However, in the fluoroscopy or fluoroscopy images, the breathing movements are clearly visible, as will be described below with reference to 5 to 8th explained and illustrated. The registration must now be adapted to these breathing movements. They exist in the literature, for example in Rohlfing et al. [2], "Markerless real-time target region tracking: application to frameless stereotactic radiosurgery," in Proceedings of 9th Fall Workshop Vision, Modeling, and Visualization, November 16-18, 2004 described approaches to determine this respiratory movement based on information in the fluoroscopic images by means of the track of certain structures or instruments and compensate accordingly.

Becomes trying to determine the respiratory movement by tracking the needle, this creates certain inaccuracies.

The registration of 3-D images to 2-D X-ray images is for example from the Dissertation by Penney [1], "Registration of Tomographic Images to X-ray Projections for Use in Image Guided Intervention", King's College London, 2000, pp. 36-58 and 97-159 , known.

A Breath correction of 2-D / 3-D registered images as a translation is described for example in the aforementioned literature [2]. For other applications, such as In CT-guided interventions the breathing movement often using external sensors in example determined by the diaphragm.

In the WO 01/01845 A2 is a localization of instruments described for example with optical or electromagnetic sensors.

In the US 2008/0027316 A1 is about the adaptation between mask and contrast agent image by means of "pixel shift" in digital subtraction angiography.

The Invention is based on the object, a method of the aforementioned Form such a way that it is robust against possible Mistakes in the breathing movement specifically for abdominal punctures by tracing, for example, needles to determine and accordingly can compensate.

• a) Prä-interventionelle Aufzeichnung eines tomographischen 3-D-Bildes eines Zielbereiches der Intervention,
• b) Aufzeichnung eines 2-D-Bildes des Zielbereiches und Registrierung mit dem 3-D-Bild während der Intervention,
• c) Markierung im 2-D-Bild eines Bereichs mit sichtbaren Bildmerkmalen von sich bewegenden Strukturen,
• d) Bestimmung während der Intervention von in weiteren, aus der gleichen Projektion aufgenommenen 2-D-Bildern sichtbaren Bildmerkmalen der Bewegung des Patienten in Form sowohl einer Translation als auch einer Rotation,
• e) Berechnung einer virtuellen Verlängerung der sichtbaren Bildmerkmale für mehrere Suchvorgänge in verschiedenen 2-D-Bildern (27) oder Frames,
• f) Ermittlung eines virtuellen Rotationszentrums durch Schnitt der virtuellen Verlängerungen,
• g) Berechnung mit den in jedem neuen Suchvorgang ermittelten Größen und über das virtuelle Rotationszentrum als zusätzlichen ”Stützpunkt” einer Verschiebungskorrektur, und
• h) Visualisierung der 2-D-Bilder gemeinsam mit dem 3-D-Bild, wobei die 3-D-Bilder und/oder 2-D-Bilder der der errechneten Verschiebung entsprechend korrigiert werden.

The object is achieved by the following steps.

• a) pre-interventional recording of a tomographic 3-D image of a target area of the intervention,
• b) recording a 2-D image of the target area and registering with the 3-D image during the intervention,
• c) marking in the 2-D image of an area with visible image features of moving structures,
• d) determination during the intervention of image characteristics of the movement of the patient visible in further 2-D images recorded from the same projection in the form of both a translation and a rotation,
• e) calculation of a virtual extension of the visible image features for multiple searches in different 2-D images ( 27 ) or frames,
• f) determining a virtual center of rotation by cutting the virtual extensions,
• g) calculating with the magnitudes determined in each new search and the virtual rotation center as an additional "vertex" of a displacement correction, and
• h) visualization of the 2-D images together with the 3-D image, whereby the 3-D images and / or 2-D images are corrected according to the calculated displacement.

The Editing simplifies when the motion found on a Preferred direction is restricted.

In Advantageously, the marked areas in the recorded fluoroscopic images and sequences using methods of Region trackings are recovered.

It has proven to be advantageous when estimating the virtual rotation center through a "least squares Problem "is solved with increasing number always better.

When marked area according to step c) can be advantageous a part of the already visible in Fluoroskopiebild needle, a corresponding anatomical region and / or one for this purpose or applied special marker find use.

According to the invention the marking of the areas to be tracked according to step c) manually with the image characteristics moving with the respiration performed or automatically detected and tracked.

A Acceleration of the visualization can be achieved if the 3-D pictures and / or 2-D pictures of the calculated shift Corresponding to feature h) corrected in real time become.

Conveniently, the pre-interventional recording of a tomographic 3-D image takes place according to step a) from CT, angiography or MR sequences.

According to the invention the 3-D record registered to the two-dimensional fluoroscopic image created as a native or as a 3-D angiography record be.

The Invention is described below with reference to the drawing Embodiments explained in more detail. Show it:

1 an X-ray diagnostic device for carrying out the method,

2 a view of the path of a detector and a radiation source around an object to be examined in the axial direction,

3 a schematic representation of the ribcage to illustrate the respiratory movements,

4 a fluoroscopic image of the abdomen from the AP projection during a puncture with markings indicative of the movements of a needle,

5 the fluoroscopic image of the abdomen according to 4 with markings of the needle and the puncture target,

6 during an abdominal puncture the same projection in different stages of the respiratory cycle and

7 to 9 a schematic representation of the assumptions according to the invention on the respiratory correction.

In the 1 an X-ray diagnostic device is shown, the one on a stand in the form of a six-axis industrial robot or articulated robot 1 rotatably mounted C-arm 2 has at its ends an X-ray source, for example an X-ray source 3 , and an X-ray image detector 4 are mounted as an image recording unit.

By means of the example of the DE 10 2005 012 700 A1 known articulated robot 1 , which preferably has six axes of rotation and thus six degrees of freedom, the C-arm 2 be spatially adjusted, for example, by turning around a center of rotation between the X-ray source 3 and the X-ray detector 4 is turned. The X-ray system according to the invention 1 to 4 is in particular about centers of rotation and axes of rotation in the plane of the X-ray image detector 4 rotatable, preferably around the center of the X-ray image detector 4 and around the center of the X-ray image detector 4 cutting axes of rotation.

The well-known articulated robot 1 has a base frame, which is for example fixedly mounted on a floor. It is rotatably mounted about a first axis of rotation a carousel. On the carousel is pivotally mounted about a second axis of rotation a rocker arm, on which is rotatably mounted about a third axis of rotation, a robot arm. At the end of the robot arm, a robot hand is rotatably mounted about a fourth axis of rotation. The robot hand has a fastener for the C-arm 2 which are pivotable about a fifth axis of rotation and about a perpendicular to it de sixth rotation axis is rotatable.

The X-ray image detector 4 may be a rectangular or square semiconductor flat detector, preferably made of amorphous silicon (a-Si).

The X-ray source 3 emits a beam emanating from a beam focus of its X-ray source 10 pointing to the x-ray image detector 4 meets. The ray bundle 10 is in 2 indicated.

In the beam path of the X-ray source 3 is located on a patient table 5 for receiving, for example, a heart, a patient to be examined 6 , At the Röntgen gendiagnostikeinrichtung is a system control unit 7 with an image system 8th connected to the image signals of the X-ray image detector 4 receives and processes. The x-rays can then be viewed on a monitor 9 to be viewed as.

In radiography or fluoroscopy by means of such an X-ray diagnostic device, the medical 2-D data of the X-ray image detector 4 in the picture system 8th if necessary cached and then on the monitor 9 played.

If 3-D data sets are to be created according to the so-called DynaCT method, the rotatably mounted C-arm is used 2 with X-ray source 3 and X-ray image detector 4 turned so that, like the 2 schematically shows in plan view of the axis of rotation, the X-ray shown here pictorially by its beam focus 3 as well as the X-ray image detector 4 one in the beam path 10 of the X-ray source 3 located object to be examined 11 in an orbit 12 move. The orbit 12 can be completely or partially traversed to create a 3-D data set.

The C-arm 2 with X-ray source 3 and X-ray image detector 4 In this case, according to the DynaCT method, it preferably moves by at least one angle range of 180 °, for example 180 ° plus fan angle, and takes up projection images from different projections in rapid succession. The reconstruction can only take place from a subarea of this recorded data.

In the object to be examined 11 it may be, for example, an animal or human body but also a phantom body.

The X-ray source 3 and the X-ray image detector 4 each run around the object 5 around, that's the X-ray 3 and the X-ray image detector 4 on opposite sides of the object 11 are opposite.

The 3 shows a schematic representation of the assumptions about the respiratory correction. In the rib cage 13 squeeze the lungs 14 breathing the diaphragm 15 down, that's the movement to the abdomen 16 passes. The by the double arrow 17 characterized respiratory movement and thereby induced by double arrows 18 marked, to the abdomen 16 The respiratory movement that is passed on thus has a clear preferred direction, especially for all X-ray projections along the "diaphragmatic plane", the usual image plane in abdominal interventions. The actual movement visible in the X-ray projection is, of course, much more complex and generally also contains a rotational or distortion component, as will be described later. Simplified, however, it can be understood as translation in the image plane with a certain preferred direction.

In the 4 For example, a fluoroscopic image of the abdomen from the AP projection (perpendicular to the patient's abdomen) is shown during a puncture. In a puncture, the needle shown as a bar can 19 in the intercostal spaces only restricted with respiration according to double arrow 20 but in the abdomen itself according to the double arrow 21 largely unrestricted, so doing a rotation 22 results. The needle 19 moves between the dashed lines 23 and 23 ' , Therefore, the respiratory movement related to the instrument causes the needle 19 , a superposition of rotation and translation. This overall movement is to be found and compensated in particular for the potential puncture target.

The 5 and 6 during an abdominal puncture show the same projection at different stations of the respiratory cycle. In 5 are the needle and the puncture target by markers 24 and 25 characterized. These marks 24 and 25 are as references in 6 drawn to illustrate the error in the 2-D / 3-D overlay of the needle 19 and the puncture target 26 caused by the respiratory movement, and thus to show the respiratory-related deviation in an abdominal puncture. To determine and balance this breathing movement is the one object of the invention.

• 1. Die Atembewegung unterliegt einer gewissen Vorzugsrichtung. Aus physiologischen Gründen verläuft diese entlang der Körperachse (siehe Doppelpfeil 17 in 3). In den aus den üblichen Projektionsrichtungen, insbesondere der AP Projektion, aufgenommenen Fluoroskopiebildern entspricht dies einer Bewegung in ”Auf-Ab-Richtung”.
• 2. Bei einer Punktion kann sich die Nadel 19 in den Rippenzwischenräumen nur eingeschränkt mit der Atmung bewegen, im Abdomen selbst aber weitgehend uneingeschränkt (siehe Doppelpfeile 20, 21 in 4). Deshalb ist die Atembewegung bezogen auf das Instrument eine Überlagerung von Rotation 22 und Translation.

In summary, the following assumptions can be made for this procedure:

• 1. The respiratory movement is subject to a certain preferred direction. For physiological reasons, this runs along the body axis (see double arrow 17 in 3 ). In the from the usual Projection directions, in particular the AP projection, fluoroscopy images recorded this corresponds to a movement in "up-down direction".
• 2. In a puncture, the needle may 19 in the intercostal spaces only to a limited extent move with the respiration, in the abdomen itself however largely unrestricted (see double arrows 20 . 21 in 4 ). Therefore, the respiratory motion related to the instrument is a superposition of rotation 22 and translation.

aim It is this total movement, in particular for the potential To find and balance the puncture target.

• • Atmung als reine Translation in der Bildebene zu begreifen und
• • diese Bewegung anhand bestimmter, sich mit der Atmung bewegter Strukturen im Fluoroskopiebild zu bestimmen und auszugleichen. Diese Strukturen können entweder vom Anwender manuell gekennzeichnet oder automatisch ermittelt werden.

The method proposed in [2] is now to

• • to understand breathing as pure translation in the image plane and
• • To determine and balance this movement by means of certain structures moving with respiration in the fluoroscopic image. These structures can either be marked manually by the user or automatically determined.

If the thus determined translation according to the double arrows 20 and 21 interpreted as the sole respiratory movement, there is an error for needle intervention as the component of rotation 22 not enough is considered.

Also when the rotation of templates is calculated with and the overlay adjusted accordingly, this can lead to large inaccuracies to lead. A correct adaptation of the overlay depends strongly on the correct calculation of the rotation. However, this is generally in the low-dose (and therefore very noisy) fluoroscopic images difficult to calculate be. Also, the rotation i. A. only on in discrete angular steps rotated templates, resulting in inaccuracies due to the Discretization leads.

Based on 7 that a noisy fluoroscopic image 27 shall represent the given conditions for the calculation of the motion correction in more detail. In an initial registered state 28 from needle 19 and puncture target 26 becomes the area to be tracked 29 marked and in a search window 30 tracked. The deflection thus determined is interpreted as breathing movement. Becomes the overlaid puncture target 31 shifted accordingly, there is an error, since the rotation component of the templates 32 is not considered.

Even if the rotation of the template 32 is taken into account, as in 8th is displayed, and the overlay is adjusted accordingly, this can lead to large inaccuracies, since a correct adaptation depends strongly on the correct calculation of these values. However, this will generally be difficult in the low dose and therefore highly noisy fluoroscopic images.

The prerequisite for the method according to the invention with the extension of the respiratory correction for needle interventions is a 3-D data record registered for the two-dimensional fluoroscopy image, which has been created either as a native or as a 3-D angiography data set. The example in 9 illustrated respiratory correction then proceeds as follows:

• 1) The doctor marks on the (standing) fluoroscopic image or fluoroscopic image 27 an area 29 from which he knows from his physiological experience that he is in sync with breathing, eg. B. a. (preferred) a part of the already in Fluoroskopiebild 27 visible needle 19 or b. a corresponding anatomical region or c. a special marker or the like applied for this purpose or the like
• 2) The doctor continues with his procedure. In the subsequently recorded fluoroscopic images 27 and sequences become the marked areas 32 , for example, according to the methods of the region tracking described in [2], found again. The movement found may be in a known preferred direction (see double arrow 17 in 3 ).
• 3) For each search S (j) of a template 32 in the 2-D image or frame F (i) are compared to the initial state 28 both the translation T (i) described above and the rotation R (i) determined. With these two sizes can be a virtual extension L of the tracked needle 19 to calculate. If this is carried out for several search processes in different frames F (i), it is possible to estimate a virtual rotation center Z by cutting the virtual extensions L (i) (or as a solution of a "least squares problem"), which always increases with increasing i better determined.
• 4) Along with the ones found in each new search S (j) Sizes T (j) and R (j) can now be over the additional "base" Z relatively stable calculated an adjustment of the overlay even if the individual quantities T (j) and R (j) were determined only inaccurately.
• 5) The registration will be based on the in point 4 calculated shift in real time updated.

As an alternative to the manual marking of the areas to be tracked proposed in 1), the image features associated with respiration move (especially the needle), also be detected and tracked automatically.

By the embodiment of the invention receives a robust method of respiratory correction, especially for in the picture tracked structures, that of a combined translation / rotation are subject. The method may preferably be for the Determination of respiratory motion can be used by tracking a needle (initially manually marked or automatically detected) is appreciated.

Appendix: Literature

• [1] GP Penney. King's College London, London SE1 9RT England, 2000. "Registration of Tomographic Images to Xray Projections for Use in Image Guided Interventions", PhD thesis, University College London, CISG, Division of Radiological Sciences, Guy's Hospital, King's College London ,
• [2] T. Rohlfing, J. Denzler, DB Russakoff, C. Grässl, and CR Maurer, Jr., "Markerless real-time target region tracking: application to frameless stereotactic radiosurgery," in Proceedings of 9th Case Workshop Vision, Modeling, and Visualization , Nov. 16-18, 2004. Stanford, CA, B. Girod, M. Magnor, and H.-P. Seidel, Eds., Berlin, Germany, 2004, pp. 5-12, Infix, Akademische Verlagsgesellschaft Berlin ,

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 01/01845 A2 [0009]
• US 2008/0027316 A1 [0010]
• DE 102005012700 A1 [0030]

Cited non-patent literature

• - A. Oppelt (ed.): Imaging Systems for Medical Diagnostics, pages 65 to 82, Publicis Verlag, Nov. 2005 [0003]
• - Rohlfing et al. [2], "Markerless real-time target region tracking: application to frameless stereotactic radiosurgery", in Proceedings of 9th Case Workshop Vision, Modeling, and Visualization, November 16-18, 2004 [0005]
• - PhD thesis by Penney [1], "Registration of Tomographic Images to X-ray Projections for Use in Image Guided Intervention", King's College London, 2000, pp. 36 to 58 and 97 to 159 [0007]

Claims (12)

Correction method for motion correction in a two-dimensional fluoroscopic image during imaging during a medical intervention of a patient comprising the following steps: a) pre-interventional recording of a tomographic 3-D image of a target area of the intervention, b) recording of a 2-D image ( 27 ) of the target area and registration with the 3-D image during the intervention, c) marking in the 2-D image ( 27 ) of a region with visible image features of moving structures ( 19 . 27 . 31 ), d) determination during the intervention in further 2-D images (F (i)) taken from the same projection from these visible image features ( 19 . 27 . 31 ) of the movement of the patient in the form of both a translation (T (i)) and a rotation (R (i)), e) calculation of a virtual extension (L (i)) of the visible image features for several searches S (j) in FIG different 2-D images ( 27 ) or frames F (i), f) determination of a virtual center of rotation (Z) by intersection of the virtual extensions L (i), g) calculation with the variables T (j) and R (j) determined in each new search operation S (j) ) via the virtual rotation center (Z) as an additional "vertex" of a displacement correction and h) visualization of the 2-D images ( 27 ) together with the 3-D image, wherein the 3-D images and / or 2-D images ( 27 ) of the calculated displacement are corrected accordingly. Correction method according to claim 1, characterized that the movement found restricted to a preferred direction becomes. Correction method according to one of claims 1 or 2, characterized in that the marked areas in the recorded fluoroscopic images and sequences using methods be recovered from the region tracking. Correction method according to one of claims 1 to 3, characterized in that the estimate of the virtual Rotation center solved by a "least squares problem" becomes. Correction method according to one of claims 1 to 4, characterized in that as areas to be tracked in accordance with step c) a part of the needle already visible in the fluoroscopic image ( 19 ) is marked. Correction method according to one of claims 1 to 5, characterized in that as to be tracked areas according to step c) a corresponding anatomical Region is highlighted. Correction method according to one of claims 1 to 6, characterized in that as to be tracked areas according to step c) one for this purpose, or applied special marker is used. Correction method according to one of claims 1 to 7, characterized in that the marking of the pursued Areas according to step c) with the Breathing moving image features is performed manually. Correction method according to one of claims 1 to 8, characterized in that the marking to be followed Areas according to step c) with the Breathing moving image features automatically detected and tracked becomes. Correction method according to one of claims 1 to 9, characterized in that the 3-D images and / or 2-D images ( 27 ) of the calculated displacement corresponding to feature h) are corrected in real time. Correction method according to one of the claims 1 to 10, characterized in that the pre-interventional Recording a tomographic 3-D image according to step a) from CT, angiography or MR sequences. Correction method according to one of the claims 1 to 11, characterized in that the two-dimensional Fluoroscopy image registered 3-D dataset as native or has been created as a 3-D angiography record.