Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-04-27
2001-11-13
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S426000, C600S427000, C378S062000
Reexamination Certificate
active
06317621
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a method and apparatus for catheter navigation in three-dimensional vascular tree exposures, in particular for intracranial application, of the type wherein the position of the catheter is detected and mixed into the 3D image of the preoperatively exposed vascular tree reconstructed in a navigation computer, and wherein imaging (registering) of 3D patient coordinate information ensues with a 3D image coordination system prior to the intervention using a number of markers placed on the patient's body, the position of these markers being registered by the catheter.
2. Description of the Prior Art
The treatment of vascular pathologies, in particular intracranial vascular pathologies, frequently ensues with the aid of a catheter that is inserted into the femoral artery and is guided through the blood vessels to the location of the treatment site. This procedure is implemented using continuously pulsed 2D-radioscopy (frequently with biplanar systems) and a contrast medium. It is often difficult for the neuro-radiologist to bring the 2D radioscopic images into coincidence with the complex three-dimensional shape of the real vascular tree. Another disadvantage of this known method is that the necessity of continuously implementing the radioscopy during the intervention entails radiation exposure for the physician and patient, and requires that the injected contrast medium be present during the entire catheter treatment, so that contrast agent must be constantly re-injected, which can have a toxic effect.
Three-dimensional images of the vascular tree can be produced by different imaging modalities, such as e.g. magnetic resonance angiography (MRA), computed tomography angiography (CTA) and 3D angiography. In 3D angiography, a 3D volume of the vascular tree is reconstructed and visualized from several, approximately 50, preoperative or intraoperative 2D x-ray projection images taken from different angles, these images generally being acquired using a C-arm x-ray device. The neuro-radiologist obtains a 3D image of the vascular tree by means of 3D exposure techniques, but has no direct knowledge about the current position of the catheter in this 3D vascular tree during the intervention. The physician must mentally image the intraoperative 2D radioscopy images, in which the catheter is depicted, onto the preoperatively scanned and reconstructed 3D vascular tree in which the catheter is not depicted, which can be laborious and time-consuming given complex vascular tree structures.
Detecting the position of the catheter using a position detection system and mixing a representation thereof into the reconstructed, three-dimensional vascular tree exposures is known, although the imaging of the 3D patient coordinate system data onto the 3D image coordinate system poses significant difficulties.
A method is disclosed in U.S. Pat. No. 5,851,183, in which the tip of a probe is detected by a position detection system and is represented in an image together with an x-ray exposure taken at the same time. In this procedure, however, only that slice is depicted from the acquired tomograms (of course, using the tip of the probe) in which the probe tip is currently located. This is, however, not comparable to the mixing a representation of a catheter tip into a three-dimensional image, to allow the catheter to be guided on the basis of this mixing so that a physician can reach the desired locations of branches of blood vessels or such. In addition, in the method according to U.S. Pat. No. 5,851,183, it is necessary to produce x-ray images with virtually no interruptions during the examination, which represents a very significant radiation exposure for the patient that one would optimally like to avoid.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and a device of the type initially described with which the radiation exposure for the physician and patient during the intervention is reduced as is the amount of injected contrast medium during the intervention, and wherein the current catheter position is represented in a three-dimensional view of the vascular tree.
To achieve this object in a method of the type initially described, according to the present invention, given the use of a C-arm x-ray device for 3D-angiography, markers are detected in at least two 2D-projection images, from which the 3D-angiogram is calculated, and are projected back onto the imaged subject in the navigation computer and are brought into relation to the marker coordinates in the patient coordinate system using the projection matrices applied to the respective 2D-projection images, these matrices having been determined for the reconstruction of the 3D-volume set of the vascular tree, i.e. an angiographic 3D-image of the vascular tree.
The invention thereby avoids the problems hitherto existing in conventional methods of the type initially described associated with registering the catheter position in the 3D-angiography, namely when the markers still depicted in the 2D exposures do not appear as well in the 3D-image due to the size of the head and the new section that can be generated. As focal points of the respective section volume of the projection cones of the 2D-projection images used in the inventive method, the focal points of the markers can be respectively detected as 3D coordinates, most easily prior to the back-projection of a marker identified in the 2D-image, so that the focal point thereof is detected and only this point is projected back.
The inventive method enables navigating the catheter in the 3D-vascular tree during the intervention completely without intraoperative radioscopic exposures and without administering an intraoperative contrast medium.
For the registration, the marker position in the 3D image can be approached—when the markers are visible in the 3D image—for example, with the aid of a mouse, and brought into relation to the positions in the patient coordinate system, detected by touching the same markers with the catheter tip. This is possible without problem given CTA and MRA, wherein, for example, the entire head can be produced as a 3D image without problem using the markers attached to the exterior thereof. Magnetic resonance angiography (MRA) has the additional advantage that absolutely no radiation exposure occurs, not even for acquiring the pre-operative image data set for the vascular tree for the patient.
The identification of the markers can ensue interactively or even automatically, with the markers each being fashioned differently for the automatic identification, so that they can be easily and automatically differentiated by their varying form and/or size in the images. In an interactive identification, care must be taken that the markers in the patient coordinate system as well as the image coordinate system, and in turn, in each of the n projection images, are identified in the same sequence.
The visualization of the vascular tree with the mixed in catheter tip at to current position detected via the position detection system and its conversion into the image coordinate system can ensue in the 3D-surface representation, whereby the catheter tip is mixed into the three-dimensional image of the vascular tree generated by segmenting and subsequent surface rendering or volume rendering.
The 3D-visualization of the vascular tree alternately can ensue using MIP (maximum intensity projection), in which the current position of the catheter tip is imaged on the next pixel, so that the catheter tip can be mixed into the MIP display.
A “fly-through” visualization of the vascular tree from the perspective of the of the catheter tip is particularly favorable and helpful for the neuro-radiologist when navigating the catheter, this “fly-through” making a particularly simple manipulation of the catheter possible at the vascular branches.
During the intervention, it is constantly monitored whether the catheter mixed into the vascular tree is located within the imaged v
Graumann Rainer
Rahn Norbert
Lateef Marvin M.
Mantis Mercader Eleni
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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