"Important methods in imaging with C-arm X-ray machines are diagnostic imaging with cardangiography at medium X-ray doses, a native visualization of the coronary vessels with the aid of contrast agents, digital subtraction angiography (DSA) for visualizing vessels exhibiting little movement with the aid of contrast agents, a method in which a native image is subtracted as what is termed a 'mask' from a series of native images in which a vessel or vascular tree is filled with contrast agent, the anatomic background disappearing as a result of the subtraction and the vessel or vascular tree remaining visible on its own, and 3D imaging with or without contrast agent and interventional imaging with fluoroscopy or transillumination in which primarily the positioning of catheters, guide wires, balloon catheters, stents, etc. is effected using a small X-ray dose, this method also being used purely diagnostically in order to position a catheter for the application of contrast agent, and roadmapping, in which, similarly to DSA, initially a mask, a native image of a vascular tree filled with contrast agent, is produced. Next a series of native images is generated in which a wire, for example, is moved. For subtraction of the mask image all anatomical structures disappear. All that remain visible are the vascular tree and the wire moved 'therein'.
"In addition to the methods mentioned here there are more advanced methods such as 3D roadmapping, for example.
"In a known roadmap method, illustrated for example in FIG. 2, the following images are generated: a pure native image 10 (anatomy only) during the system dose regulation, a mask image 11, a native image from the fill phase in which the vascular tree 12 is filled with contrast agent, and a native image series 13 in which an object 14, a wire for example, is moved in the vascular tree 12 under fluoroscopy. From the fluoroscopy image series 13 in which the object 14 can be seen, the mask image 11 with vascular tree 12 filled with contrast agent is subtracted in a subtraction stage 15 and in an addition stage 16 a constant K for setting the mean grayscale value is added. Further image processing steps such as contrast adjustment, edge enhancement, etc. can follow until a current subtraction series 17 is obtained in which only the moving object 14 is still readily identifiable in the 'frozen' vascular tree 12."
As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventor's summary information for this patent: "The object of the invention is to embody a method of the type cited in the introduction in such a way that during the roadmapping the traditional drawbacks such as poor visibility of the wire, 'burnout' (disappearance of the wire, which is represented as dark, in the vascular tree, which is represented as light, due to excessively high contrast) etc. are reduced or avoided, and during an overlaying of a fluoroscopy image over a DSA image (overlay reference) in which the inverted DSA image is blended at a selectable percentage with a fluoroscopy image, the DSA image serving to visualize the vascular tree, the fluoroscopy serving to visualize the wire moved in the vascular tree, the visualization is improved.
"The object is achieved according to the invention for a method and for a device by the features recited in the independent claims. Advantageous embodiments are disclosed in the dependent claims.
"In the case of the above-mentioned method this is achieved by means of the following steps: a) acquiring at least one empty image (pure anatomy), at least one filling image with vascular tree filled with contrast agent, and at least one native image with introduced object by means of a detector having a matrix-shaped array of pixels, b) subtracting the empty and filling image in order to generate a first subtraction image, c) subtracting the empty image and the at least one native image in order to generate at least one second subtraction image, d) processing the first subtraction image in order to form a vessel image, e) processing the at least one second subtraction image in order to form at least one object image, f) processing the vessel image and the at least one object image in order to generate at least one roadmap image, and g) playing back the at least one roadmap image.
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