X-ray or gamma ray systems or devices – Accessory – Alignment
Reexamination Certificate
2002-12-10
2004-11-16
Bruce, David V. (Department: 2882)
X-ray or gamma ray systems or devices
Accessory
Alignment
C600S425000, C600S427000
Reexamination Certificate
active
06817762
ABSTRACT:
BACKGROUND
The present invention relates to a fluoroscopy method for obtaining an image of an object together with radiopaque intervention means, the method using a rotating X-ray source and a corresponding detector with the object and the intervention means positioned between the X-ray source and the detector, the method further using processing means, said method comprising subjecting the object to the X-rays originating from the X-ray source; positioning the intervention means within the object, such that they intercept at least a part of said X-rays; using the processing means to present a spatial position of the intervention means with respect to the object.
The present invention relates also to a system for carrying out the fluoroscopy method according to the invention.
According to a general practice of conventional fluoroscopic intervention, the intervention means are guided within the patient by means of, for example a CT-apparatus. In this case the operator inserts, for example, a needle into the patient, while the intervention means are located within the primary X-ray beam, exposing an interesting volume of the patient, so that it can be localized on a transmission image of the patient. The width of the primary beam is comparable with a cross-section of the intervention means, because the dimensions of the beam correlate with a slice thickness of the CT image. It is important to have the tip of the intervention means together with the surrounding anatomy of the patient within the image. Therefore, the beam width must not be too small and the angle between the needle and the image plane must be small. Given these constrains the operator hand can hardly be protected from a direct X-ray exposure.
The problem of the X-ray dose to the operator's hand is addressed in U.S. Pat. No. 4,485,815. This document discloses a fluoroscopy method for performing percutaneous puncture treatment, wherein the intervention means are supplied with an adjustment comprising an elongated radiolucent handle, so that the operator's hands are substantially removed from the area of primary X-ray beam. The intervention means are positioned substantially parallel to the primary X-ray beam. The movement of the intervention means is continuously monitored on a fluoroscope monitor, the intervention means being viewed in cross-section. The problem of the known method lies in the construction of the provided handle, increasing the working lever experienced by the operator to maneuver the intervention means. The accuracy of the such a positioning of the intervention means is a critical issue, especially when working within a critical area, such as a brain. Another problem of the known fluoroscopic method is the fact that the needle is presented only as a transversal cross-section, providing a limited information about the position of the needle tip within the patient.
SUMMARY
It is an object of the invention to provide a fluoroscopic method, wherein the dose to the operator is decreased, whereas the intervention means can be easily positioned within the patient. The fluoroscopic method according to the invention is characterized by a cone beam being used as the X-ray source, a two-dimensional detector being used as the detector. According to this technical measure, the generated X-ray beam will propagate substantially in three dimensions, illuminating a two-dimensional X-ray detector, thus providing three-dimensional volume data of the patient and the intervention means, based on the acquisition of two-dimensional projections from, for example, one rotation. Due to a cone-beam acquisition the intervention means can have a substantial angulation with respect to the image slices, providing the operator's hand being outside the primary X-ray fluence. This reduces the X-ray dose to the operator's hand substantially.
A preferred embodiment of the fluoroscopic method according to the invention is characterized in that the spatial position of the intervention means within the object is presented within one image reconstruction slice by means of an image reconstruction algorithm. Since the operator can hardly inspect a set of two-dimensional slices during the intervention, a single reconstructed image provides all important information about the spatial position of the intervention means with respect to the local anatomy of the patient. The extended image volume covered by a set of two-dimensional slices can be used to obtain the important image information around the tip of the intervention means, for example a needle. Since the individual slices in the cone beam geometry are thinner than the complete illuminated volume limited by the cone beam geometry, the inherent resolution of the image information can be high and is mainly defined by the resolution of the X-ray detector in a longitudinal direction. An example of a suitable image reconstruction algorithm is a known method of volume rendering or a known method of multi-planar reformatting, both being an interpolation technique to generate a virtual image oblique to the set of image planes. An example and application of such image reconstruction algorithms is given in an “Easy Vision” Product Manual, Philips Medical Systems. The oblique image should be positioned within the imaged volume such that, for example, the biopsy needle is located within the virtual slice. This particular embodiment ensures reduced radiation to the operator and a high resolution of the resulting reconstructed image that covers the tip of the needle and the surrounding anatomy of the patient.
Another embodiment of the fluoroscopy method according to the invention is characterized in that the position and the orientation of said reconstruction slice is a-priori calculated. In case the optimal trajectory of the needle path is pre-planned based on a static image acquisition, it is possible to use the coordinates of the pre-planned path to orient the image reconstruction plane. In this case the image reconstruction plane is fixed during the procedure and the operator is maneuvering the intervention means so that they stay in the pre-determined plane during the procedure. An application of this technique is known from Proksa et al ‘Navigation Support for CT-guided interventional radiology’, ECR99, Vienna 1999.
Another embodiment of the fluoroscopy method according to the invention is characterized in that the position and the orientation of said reconstruction slice is determined with respect to the on-line reconstructed image of the intervention means. Since the biopsy needle is made of a radiopaque material, it will be imaged with a high contrast with respect to the surrounding patient anatomy. Therefore, it is possible to perform an on-line detection of pixel values, above a certain threshold for the X-ray absorption, in order to reconstruct the needle in three-dimensions. For this purpose one can use a variety of known image registration techniques. A plane cutting the line corresponding with the coordinates of the needle in three-dimensions will be the image reconstruction plane. An advantage of this approach is the possibility to guide the reconstruction plane in a dynamic mode, according to the movement of the needle within the patient anatomy.
Another embodiment of the fluoroscopy method according to the invention is characterized in that the intervention means are provided with position detection means, the processing means comprising further means for determining the position of the intervention means relative to the object. The biopsy needle could be combined with means to register the position and orientation of the needle relative to the CT-scanner. The measurement could be similar to the technique presented by Proksa et al ‘Navigation Support for CT-guided interventional radiology’, ECR99, Vienna 199. During the examination the physician introduces a surgical or interventional instrument, such as a biopsy needle, into the body of the patient. The surgical instrument is provided with transmission elements such as diodes emitting light or infrared radiati
Bruce David V.
Kiknadze Irakli
Koninklijke Philips Electronics , N.V.
Lundin Thomas M.
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