Stitchless panorama in medical image acquisition

Abstract

According to the present invention, at least one image pair, consisting of a fluoroscopic image and an angiographic image taken from the same viewing position of the imaging device relative to the patient at the time of capturing the respective image, is acquired. This is referred to as the acquisition phase. This is followed by a live phase, in which a live fluoroscopic image is registered individually with the fluoroscopic image of at least one image pair, such that the spatial relationship between the live fluoroscopic image and the fluoroscopic image, and thus with the angiographic image and the image pair in general, becomes known. Angiographic information representing the vascular structure can then be taken from the part(s) of the angiographic image(s) within the image pair(s) which overlap with the live fluoroscopic image and be overlayed over the live fluoroscopic image. The present invention focusses on the acquisition phase, in which the fluoroscopic image and / or the angiographic image of at least one of the at least one image pair is displayed after acquisition of said fluoroscopic or angiographic image, respectively. The position at which the image is displayed depends on the viewing position of the imaging device relative to the patient when capturing the respective image.

Description

[0001] STITCHLESS PANORAMA IN MEDICAL IMAGE ACQUISITION

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a computer-implemented method for overlaying angiographic information over a fluoroscopic image of a patient, a corresponding computer program, a computer-readable storage medium storing such a program and a computer executing the program, as well as a medical system comprising the aforementioned computer.

[0004] TECHNICAL BACKGROUND

[0005] Angiographic images representing at least a part of the vascular structure of a patient are helpful tools in medical applications, for example for supporting a medical intervention. But capturing angiographic images involves the administration of a contrast agent, which can be toxic to the patient, such that capturing a sequence of live angiographic images is disadvantageous. This document relates to an alternative in which angiographic imaging is performed only once and the vascular structure comprised in the angiographic images is overlayed over live fluoroscopic images of the patient.

[0006] The present invention can be used for example for PAD (Peripheral Artery Disease) procedures or endovascular revascularizations of vascular occlusions, e.g. in connection with a medical navigation system of Brainlab AG.

[0007] Aspects of the present invention, examples and exemplary steps and their embodiments are disclosed in the following. Different exemplary features of the invention can be combined in accordance with the invention wherever technically expedient and feasible. EXEMPLARY SHORT DESCRIPTION OF THE INVENTION

[0008] In the following, a short description of the specific features of the present invention is given which shall not be understood to limit the invention only to the features or a combination of the features described in this section.

[0009] According to the present invention, at least one image pair, consisting of a fluoroscopic image and an angiographic image taken from the same viewing position of the imaging device relative to the patient at the time of capturing the respective image, is acquired. This is referred to as the acquisition phase. This is followed by a live phase, in which a live fluoroscopic image is registered individually with the fluoroscopic image of at least one image pair, such that the spatial relationship between the live fluoroscopic image and the fluoroscopic image, and thus with the angiographic image and the image pair in general, becomes known. Angiographic information representing the vascular structure can then be taken from the part(s) of the angiographic image(s) within the image pair(s) which overlap with the live fluoroscopic image and be overlayed over the live fluoroscopic image.

[0010] The present invention focusses on the acquisition phase, in which the fluoroscopic image and / or the angiographic image of at least one of the at least one image pair is displayed after acquisition of said fluoroscopic or angiographic image, respectively. The position at which the image is displayed depends on the viewing position of the imaging device relative to the patient when capturing the respective image. It is thus not necessary that the image pairs overlap in order to find a spatial orientation between the image pairs. The images can thus be displayed with a spatial arrangement corresponding to the spatial arrangement of the areas of the patient depicted by the images without the need to overlap for finding the spatial relationship between the images.

[0011] The images taken during the acquisition phase and the live phase are captured using an imaging device having a certain viewing position onto the patient. The viewing position comprises the orientation and the location of the imaging device relative to the patient. Capturing an image means the process of taking the image by the imaging device, while acquiring image data means reading the image data representing the image into the data processing. This might happen basically at the same time, but could also happen with a time offset, for example by storing the image data.

[0012] GENERAL DESCRIPTION OF THE INVENTION

[0013] In this section, a description of the general features of the present invention is given for example by referring to possible embodiments of the invention.

[0014] In general, the invention reaches the aforementioned object by providing, in a first aspect, a computer-implemented medical method of overlaying angiographic information over a fluoroscopic image of a patient. The method comprises executing, on at least one processor of at least one computer (for example at least one computer being part of a navigation system), the following exemplary steps which are executed by the at least one processor.

[0015] In a (for example first) exemplary step, at least one image pair data is acquired, each image pair data representing an image pair and comprising fluoroscopic image data and angiographic image data representing a fluoroscopic image and an angiographic image, respectively, of a part of the patient. The fluoroscopic image and the angiographic image of an image pair are taken using the same viewing position, the viewing position being the position of the imaging device relative to the patient when capturing an image.

[0016] An image pair comprises a fluoroscopic image and an angiographic image captured using a medical imaging system such as an X-ray imaging system. The angiographic image is taken under administration of a contrast agent, while the fluoroscopic image is taken without the administration of a contrast agent. It shall be pointed out that the present invention does not relate to capturing the fluoroscopic image or the angiographic image, and in particular not to administering a contrast agent, but rather to image processing in order to combine angiographic information with a live fluoroscopic image and to display the images in a particular arrangement. The fluoroscopic image and the angiographic image of an image pair are preferably taken with the same position of the medical imaging device relative to the patient, and thus, from the same viewing position onto the patient. This means that the fluoroscopic image and the angiographic image of an image pair are spatially aligned and thus congruent. They thus show the same part of the patient. However, small differences between the viewing position of the fluoroscopic image and the viewing position of the angiographic image of an image pair might be tolerable and / or can be compensated.

[0017] An unprocessed angiographic image basically shows the same content as a fluoroscopic image, but also the vascular structure due to the contrast agent. In one embodiment, the angiographic image represented by the angiographic image data is generated by subtracting the corresponding fluoroscopic image from the unprocessed angiographic image as captured, such that only the difference, which is caused by the contrast agent in the vascular structure of the patient, remains in the angiographic image. Rather than using the fluoroscopic image of an image pair, a fluoroscopic image captured during the process of acquiring the angiographic image can be used.

[0018] Typically, the images of an image pair are captured by positioning the imaging device relative to the patient, capturing a fluoroscopic image, administering a contrast agent and capturing an unprocessed angiographic image. The contrast agent disappears while the imaging system is positioned relative to the patient again for capturing another image pair. The angiographic image is calculated from the fluoroscopic image and the unprocessed angiographic image as described above. In an alternative, the fluoroscopic image can be captured after capturing the unprocessed angiographic image.

[0019] In a (for example second) exemplary step, display image data are generated from the at least one image pair data, wherein the image pair data are spatially arranged in the display image data based on the corresponding viewing position of the image pair. The position of the image pair data in the display image data thus represents the corresponding viewing position relative to the patient. Spatially arranging the image pair data in the display image data means that the fluoroscopic image data and / or the angiographic image data of the image pair is added to the display image data, in particular at a position / positions depending on the viewing position. The fluoroscopic and / or angiographic image data might be processed before being added to the display image data, for example in terms of scaling, rotating or warping or other processing, such as noise reduction, contrast modification or edge enhancement.

[0020] The display image data may optionally comprise a representation of the patient, or of a part of the patient, for example in terms of a pictogram, an image or a generic visualization. The position of the image pair data in the display image data is set such that the image pair data is overlaid over the corresponding anatomic position of the representation of the patient. The area of the representation over which the image pair data is overlaid is the same area as the area of the patient depicted by the image pair data.

[0021] Preferably, the representation of the patient has the same viewing position relative to the patient as the image pair. In one example, the image pair represents a frontal view of a part of a leg of the patient. The representation of the patient is thus a representation of a human leg (or a part thereof) in a frontal view.

[0022] In a (for example third) exemplary step, the display image data are displayed. Since the position of the image pair data in the display image data corresponds to the viewing position of the image pair, the acquisition of the image pair can be monitored. It is for example possible to recognize whether the correct or desired part of the patient has been imaged.

[0023] In a (for example fourth) exemplary step, live fluoroscopic image data representing a live fluoroscopic image of the patient are acquired. The live fluoroscopic image data are captured using an imaging device, for example the same imaging device or type of imaging device used in the acquisition phase.

[0024] While the image pairs are taken during the acquisition phase at a first point in time, the live fluoroscopic image is taken during the live phase at a second point in time which is later than the first point in time. The live fluoroscopic image is used to monitor the patient, for example for visualizing an object in the patient, such as a medical instrument. Since the live fluoroscopic image is taken without the administration of a contrast agent, the vascular structure of the patient is not visible in the live fluoroscopic image.

[0025] In this document, the word "live" means that the second point in time is later than the first in time, and that the live fluoroscopic image is captured shortly before the data processing of the present invention is performed, preferably only a second or a fraction of a second before. The word "live" thus means that the current situation of the patient can be seen. It can further mean that a sequence of live fluoroscopic images can be captured and the data processing of the present invention is performed in real time, which for example means with a delay of for example one second or preferably less, such as a fraction of a second.

[0026] In a (for example fifth) exemplary step, the live fluoroscopic image data are registered with the fluoroscopic image data of at least one of the at least one image pair, thus obtaining the spatial orientation between the live fluoroscopic image and the image pair. In this context, this does not imply a particular registration direction, but can also mean that the fluoroscopic image data of an image pair is registered with the live fluoroscopic image data. It is only necessary to calculate the spatial orientation between them.

[0027] The spatial orientation means a relative position between two images such that areas of the two images which show the same part of the patient overlap each other.

[0028] The result of this fifth step is that it is known which parts of the live fluoroscopic image overlap with which areas of the fluoroscopic image in the image pair. It is thus known which parts of the angiographic image of the image pair overlap with parts of the live fluoroscopic image.

[0029] The registration in the fifth step can optionally involve an elastic fusion of the image pairs with the live fluoroscopic image. In this case, the fluoroscopic image is deformed to match the live fluoroscopic image as good as possible. The same deformation is applied to the corresponding angiographic image. In a (for example sixth) exemplary step, angiographic overlay image data are determined from the angiographic image data based on the spatial orientation between the live fluoroscopic image and the at least one of the at least one image pair.

[0030] For example, the angiographic image overlay data is determined from the overlapping area of the angiographic image which overlaps with the live fluoroscopic image.

[0031] The spatial orientation between the live fluoroscopic image and the image pair defines whether there is an overlap between the live fluoroscopic image and the fluoroscopic image in the image pair. This overlap means areas of the live fluoroscopic image and the fluoroscopic image of the image pair which show the same part of the patient. Due to the same viewing positions of the angiographic image and the fluoroscopic image in the image pair, an area in the angiographic image corresponding to the area of the fluoroscopic image in the image pair shows vascular information of said part of the patient. This area of the angiographic image is included in the angiographic overlay image data.

[0032] In a (for example seventh) exemplary step, the angiographic overlay image data are overlayed over the live fluoroscopic image. The result is an augmented live fluoroscopic image which represents the overlay of the angiographic overlay image data and the live fluoroscopic image. This step optionally comprises displaying the live fluoroscopic image with the overlaid angiographic overlay image data.

[0033] In this step, the vascular structure as represented by the angiographic overlay image data becomes visible in the augmented live fluoroscopic image. It is thus possible to observe, for example, objects which are visible in the live fluoroscopic image with respect to the vascular structure of the patient.

[0034] Since the field of view of medical imaging systems is limited, in particular if a particular image resolution is desired, a plurality of image pairs is captured, for example while moving the medical imaging device along the patient between capturing the image pairs. The imaging device is, for example, a C-arm on a cart that can be rolled on the floor, thus moving relative to a patient lying on a table or couch. The viewing positions are thus for example offset in a plane parallel to the ground. If multiple image pairs are captured and acquired, the multiple image pairs can be spatially arranged in the display image data according to the respective viewing directions. The display image data thus visualizes the spatial relationship between the viewing positions of the image pairs and thus represents which part or parts of the patient has / have already been imaged. The operator can then decide whether or not to capture additional image pairs to cover more of the patient. In addition or alternatively, the method may determine automatically whether or not additional image pairs have to be captured, and may inform the operator to position the imaging device appropriately or may even position the imaging device if it comprises suitable positioning means.

[0035] In the case of multiple image pairs, the live fluoroscopic image data can be registered with the fluoroscopic image data of two or more, and even all, image pairs. The angiographic overlay image data can be obtained from two or more image pairs.

[0036] It shall be emphasized that the display image data is only used for visualization in the acquisition phase. The live fluoroscopic image data is not registered with the display image data during the live phase. This document cannot be understood as encompassing registration of the live fluoroscopic image with a panoramic image comprising two or more of the fluoroscopic images acquired during the acquisition phase.

[0037] The steps of acquiring image pair data, generating display image data and displaying the display image data may executed in this order. This means that all image pairs are acquired before the display image data are generated and displayed. However, those steps can also be interweaved.

[0038] In one implementation, the steps of generating display image data and displaying the display image data are performed each time a fluoroscopic image or an angiographic image is acquired. So each newly acquired image is displayed at a position within the display image data corresponding to the imaging position and can thus be evaluated by an operator. In addition, the operator can derive the imaging position for the next image. Instead of each newly acquired image, each newly acquired image pair can be displayed in analogy. The display image data can comprise the image pair data of the current image pair and of one, some or all image pairs acquired before the current image pair. The display image data can comprise the fluoroscopic image of the current image pair and the angiographic image of the current image pair and of one or more image pairs acquired before the current image pair. In this case, the display image data comprises one fluoroscopic image only.

[0039] In one implementation, a fluoroscopic image is captured and acquired, display image data comprising this fluoroscopic image is generated and the display image data is displayed. This is repeated until user input is received. In this implementation, a sequence of fluoroscopic images is captured and displayed, resulting in a video of fluoroscopic images. The imaging position can be adjusted between the times at which two consecutive fluoroscopic images are captured. In this implementation, an operator is provided with live feedback on the viewing position of the imaging device and can adjust it as desired.

[0040] Upon reception of the user input, the latest fluoroscopic image is used for an image pair and the corresponding angiographic image for the image pair is captured and acquired.

[0041] In one embodiment, the steps of acquiring a live fluoroscopic image, registering the live fluoroscopic image data with the fluoroscopic image data, determining angiographic overlay image data and overlaying the angiographic overlay image data (V) over the live fluoroscopic image are repeated. This means that a sequence of live fluoroscopic images is acquired and supplemented with the angiographic information. The result is a video of supplemented live fluoroscopic images. One advantage of this embodiment is that a position of medical instrument in the vascular system of the patient can be visualized.

[0042] In one embodiment, a viewing position of an image pair includes a fluoroscopic viewing position and an angiographic viewing position. Each image pair thus has two viewing positions, which might be different if the imaging system moves relative to the patient between capturing the fluoroscopic image and the angiographic image. In this case, the angiographic image data and / or the fluoroscopic image data can be arranged separately in the display image data. The offset between the fluoroscopic viewing position and the angiographic viewing position can be determined and compensated when determining the angiographic overlay image data, for example by adapting the spatial orientation between the live fluoroscopic image according to the offset or by shifting and / or scaling the area taken from the angiographic image data selected for inclusion in the angiographic overlay image data depending on the offset.

[0043] In one embodiment, the fluoroscopic viewing position of an image pair is calculated by registering the fluoroscopic image data of the image pair with a patient model and the angiographic viewing position of an image pair is calculated by registering the angiographic image data of the image pair with the patient model. The patient model is for example a 3D patient model, but could also be a 2D patient model.

[0044] Various methods for performing registration are known. A typical approach for registering a 3D patient model showing the bone structure with a two-dimensional fluoroscopic image involves DRRs (digitally reconstructed radiographs). In this approach, synthetical fluoroscopic images are calculated from the 3D patient model and compared to the 2D fluoroscopic image to find a viewing position of a virtual imaging system which would lead to a synthetical fluoroscopic image that matches the 2D fluoroscopic image best. Similar approaches can be used to register the 3D patient model showing the vascular structure with the two-dimensional angiographic image.

[0045] It is assumed that the angiographic viewing position and the fluoroscopic viewing position are identical or almost identical. So if one of the viewing positions has been calculated, the result can be used as a starting position and / or a restraint when calculating the other viewing position. This reduces the computational load and speeds up the calculation for the second image of the image pair.

[0046] In one implementation, the patient model is a generic patient model representing the generic bony and vascular structure of at least a part of a generic patient. The generic patient model for example be compiled from scans of a plurality of persons. The generic patient model may be adapted to the patient, for example by scaling. The amount of the scaling may be determined from a fluoroscopic image of an image pair. In one implementation, the patient model represents a scan of the bony structure and a scan of the vascular structure of at least a part of the patient. The patient model is thus a patient-specific model. The bony structure can for example be scanned using CT (computed tomography), while the vascular structure can for example be scanned using CTA (computed tomography angiography).

[0047] In one implementation, registering the angiographic image data with the patient model uses information on the bony structure of the patient in the angiographic image data.

[0048] As described above, an angiographic image is a fluoroscopic image captured under the administration of a contrast agent. The typical angiographic image is a differential image in which the bony part is removed by subtracting a “pure” fluoroscopic image from an unprocessed angiographic image. However, this subtraction is typically not perfect such that the differential angiographic image still contains some image information on the bony structure.

[0049] Bones cause a high contrast in the fluoroscopic image and are thus particularly suitable for finding an accurate registration. The remainder of the bony image information in the angiographic image can thus increase the registration accuracy of the angiographic image with the patient model since the registration can utilize both the bony structure and the vascular structure. This effect might even increase if the imaging system can supply an unprocessed angiographic image in addition to or instead of the typical differential angiographic image.

[0050] In one embodiment, the method further comprises the step of outputting indication information if the calculated fluoroscopic viewing position differs from the calculated angiographic viewing position by more than a predetermined threshold.

[0051] As explained above, the fluoroscopic viewing position should ideally coincide with the angiographic viewing position such that the area identified in the fluoroscopic image as corresponding to an area of the live fluoroscopic image can be used as the area of the angiographic image from which the image data is used for the angiographic overlay image data. If the angiographic overlay image data is determined in this way, but the two viewing positions differ from each other, the angiographic overlay is incorrect. This is indicated by the indication information.

[0052] In one embodiment, generating display image data includes adding a representation of the patient model to the display image data. This is similar to the addition of the representation of the patient described above, but adds the patient model to which the angiographic image and / or the fluoroscopic image of an image pair are registered to the display image data. Preferably, the angiographic image data and / or the fluoroscopic image data is overlaid over the representation of the patient model. This allows a visual evaluation whether or not the registration of the fluoroscopic image data and / or the angiographic image data with the patient model is correct.

[0053] In one implementation, the overlaid angiographic image data and / or fluoroscopic image data is transparent, either fully or in parts. This allows to see the patient model through the overlaid image data. The whole overlaid image data may have a constant transparency. In another case, the part of the angiographic image data showing a vessel and / or the part of the fluoroscopic image data showing a bone is opaque or only slightly transparent, while the rest is fully or strongly transparent.

[0054] In one embodiment, a viewing position of an image is determined from the position of the imaging device and the position of the patient when capturing the image. The image is the fluoroscopic image or the angiographic image in the image pair, but can mean the image pair if the viewing positions of the fluoroscopic image and the angiographic image are identical.

[0055] The position of the imaging device and the position of the patient are for example determined using a medical tracking system. The medical tracking system tracks markers attached to the imaging device and the patient, or to a table on which the patient lies, such the viewing position can be calculated from the positions of the markers and a known relative position between the marker and the object it is attached to. The tracking system typically determines the position of a marker in a reference system of the tracking system. In another embodiment, a viewing position of an image is determined from the relative position of the patient to the imaging device when capturing the image. The imaging device is for example used to track the position of the patient. The imaging device may track radiopaque markers attached to the patient or use an additional optical camera for image-based tracking, for example using structured light. The optical camera can be a 2D or a 3D camera.

[0056] In one implementation, the imaging device further comprises a tracking unit for tracking markers attached to the patient. The markers can be of any kind, such as optical markers or electromagnetic markers. This directly tracks the position of the patient relative to the imaging device in a reference system of the imaging device.

[0057] In one embodiment, the imaging device is attached to a robotic arm. A viewing position of an image is determined from the pose of the robotic arm. The position of the patient relative to a reference of the robotic arm is known, for example by positioning the patient in a known position or positioning the patient on a table and determining the position of the table. The position of the table can be tracked. If the table is robotic, the position of the table can be determined from the pose of the table.

[0058] In one embodiment, the step of acquiring at least one image pair data comprises acquiring two or more image pair data and a gap in the display image data between two image pair data is filled with image data taken from a patient model.

[0059] In this embodiment, two adjacent areas with image pair data in the display image data to not touch or overlap each other. There is thus a gap in the display image data between two adjacent areas. This means that information is missing in this gap. This gap is filled from the patient model.

[0060] In one embodiment, at least one of the fluoroscopic image data and the angiographic image data of an image pair is supplemented from a patient model if the fluoroscopic viewing position differs from the angiographic viewing position for this image pair.

[0061] In this embodiment, the fluoroscopic image and / or the angiographic image of an image pair is supplemented, thus obtaining a supplemented image pair. The supplemented image pair is then used in the live phase for registration with the live fluoroscopic image and for determining the angiographic overlay image data. The supplemented image pair might be used when generating the display image data instead of the image pair before supplementing. An operator can then see in the display image data whether or not the supplementing is proper or plausible. If it is not, the operator can instruct to undo the supplementing and for example restore the original image pair.

[0062] In one embodiment, the step of acquiring at least one image pair data comprises acquiring two or more image pair data. The method then comprises a step of calculating a set of image pair registration data, each image pair registration data representing the spatial orientation between two overlapping image pairs and of calculating angiographic panoramic image data from the angiographic image data of the image pairs based on the set of image pair registration data. Determining the angiographic overlay image data then involves selecting a part of the angiographic panoramic image data.

[0063] In this embodiment, an angiographic panorama is stitched from the angiographic images and a section of the angiographic panorama which corresponds to the imaged part of the patient in the live fluoroscopic image is extracted and overlayed over the live fluoroscopic image. This section of the angiographic panorama does for example have the same size as the live fluoroscopic image.

[0064] In one embodiment, when the live fluoroscopic image overlaps more than one fluoroscopic image of the image pairs, the method further comprises the step of determining overlapped area data representing overlapped areas of the angiographic images corresponding to those areas of the fluoroscopic images which are overlapped by the live fluoroscopic image. The step of determining the angiographic overlay image data uses the angiographic image data in the overlapped areas.

[0065] In one implementation, the step of determining the angiographic overlay image data involves using the angiographic image data only of the one angiographic image which has the largest overlapped area. In this case, no distortions or artefacts caused by parallax due to different propagation paths of the x-ray radiation through the patient occur since only the angiographic image of one image pair is used for determining the angiographic overlay image data. In this case, not all of the vascular structure in the field of view of the live fluoroscopic image is overlayed, but this might not be necessary, in particular if the vascular structure in a region of interest, such as a region in which a medical instrument is present, is overlayed.

[0066] In another implementation, the step of determining the angiographic overlay image data involves copying, from the angiographic image which has the largest overlapped area, all of the angiographic image data in its overlapped area and copying those parts of the angiographic image data of the overlapped areas of other angiographic images which do not overlap with said largest overlapped area. The image data copied from the overlapped areas of different angiographic images then form the angiographic overlay image data.

[0067] There is thus a hard cut in the angiographic overlay image data between the angiographic image data taken from the angiographic image which has the largest overlapped area and the other parts which are taken from other angiographic images. This might result in offsets of the vascular structures as shown in the augmented fluoroscopic image at the borders between overlapped areas, in particular in a direction orthogonal to the borders, but avoids distortions or artefacts which might result from blending image data of overlapped areas.

[0068] In one implementation, the step of determining the angiographic overlay image data involves copying the angiographic image data corresponding to those areas within overlapped areas of angiographic images which do not overlap with an overlapped area of another angiographic image and merging angiographic image data of areas where overlapped areas of different angiographic images overlap to form the angiographic overly image data.

[0069] In other words, in areas of the live fluoroscopic image which overlap with one image pair only, the angiographic overlay image data is copied from the angiographic image data of the corresponding image pair, and in areas of the live fluoroscopic image which overlap with more than one image pair, the angiographic image data of said image pairs are merged or blended. This avoids distortions or artefacts in areas in which the live fluoroscopic image overlaps one image pair only and achieves a smooth transition in areas in which it overlaps with multiple image pairs.

[0070] In a second aspect, the invention is directed to a computer program comprising instructions which, when the program is executed by at least one computer, causes the at least one computer to carry out method according to the first aspect. The invention may alternatively or additionally relate to a (physical, for example electrical, for example technically generated) signal wave, for example a digital signal wave, such as an electromagnetic carrier wave carrying information which represents the program, for example the aforementioned program, which for example comprises code means which are adapted to perform any or all of the steps of the method according to the first aspect. The signal wave is in one example a data carrier signal carrying the aforementioned computer program. A computer program stored on a disc is a data file, and when the file is read out and transmitted it becomes a data stream for example in the form of a (physical, for example electrical, for example technically generated) signal. The signal can be implemented as the signal wave, for example as the electromagnetic carrier wave which is described herein. For example, the signal, for example the signal wave is constituted to be transmitted via a computer network, for example LAN, WLAN, WAN, mobile network, for example the internet. For example, the signal, for example the signal wave, is constituted to be transmitted by optic or acoustic data transmission. The invention according to the second aspect therefore may alternatively or additionally relate to a data stream representative of the aforementioned program, i.e. comprising the program.

[0071] In a third aspect, the invention is directed to a computer-readable storage medium on which the program according to the second aspect is stored. The program storage medium is for example non-transitory.

[0072] In a fourth aspect, the invention is directed to at least one computer (for example, a computer), comprising at least one processor (for example, a processor), wherein the program according to the second aspect is executed by the processor, or wherein the at least one computer comprises the computer-readable storage medium according to the third aspect. In a fifth aspect, the invention is directed to a medical system, comprising the at least one computer according to the fourth aspect and a medical imaging system.

[0073] Alternatively or additionally, the invention according to the fifth aspect is directed to a for example non-transitory computer-readable program storage medium storing a program for causing the computer according to the fourth aspect to execute the data processing steps of the method according to the first aspect.

[0074] In a sixth aspect, the invention is directed to use of the system according to the fifth aspect for conducting a medical procedure, wherein the use comprises execution of the steps of the method according to the first aspect for overlaying angiographic information over a fluoroscopic image of a patient.

[0075] For example, the invention does not involve or in particular comprise or encompass an invasive step which would represent a substantial physical interference with the body requiring professional medical expertise to be carried out and entailing a substantial health risk even when carried out with the required professional care and expertise.

[0076] For example, the invention does not comprise a step of administering a contrast agent to the patient. More particularly, the invention does not involve or in particular comprise or encompass any surgical or therapeutic activity. The invention is instead directed as applicable to combining images of two different imaging modalities taken at two different points in time. For this reason alone, no surgical or therapeutic activity and in particular no surgical or therapeutic step is necessitated or implied by carrying out the invention.

[0077] The present invention also relates to the use of the device / system or any embodiment thereof for overlaying angiographic information over a fluoroscopic image of a patient.

[0078] DEFINITIONS

[0079] In this section, definitions for specific terminology used in this disclosure are offered which also form part of the present disclosure. Computer implemented method

[0080] The method in accordance with the invention is for example a computer implemented method. For example, all the steps or merely some of the steps (i.e. less than the total number of steps) of the method in accordance with the invention can be executed by a computer (for example, at least one computer). An embodiment of the computer implemented method is a use of the computer for performing a data processing method. An embodiment of the computer implemented method is a method concerning the operation of the computer such that the computer is operated to perform one, more or all steps of the method.

[0081] The computer for example comprises at least one processor and for example at least one memory in order to (technically) process the data, for example electronically and / or optically. The processor being for example made of a substance or composition which is a semiconductor, for example at least partly n- and / or p-doped semiconductor, for example at least one of II-, III-, IV-, V-, Vl-sem iconductor material, for example (doped) silicon and / or gallium arsenide. The calculating or determining steps described are for example performed by a computer. Determining steps or calculating steps are for example steps of determining data within the framework of the technical method, for example within the framework of a program. A computer is for example any kind of data processing device, for example electronic data processing device. A computer can be a device which is generally thought of as such, for example desktop PCs, notebooks, netbooks, etc., but can also be any programmable apparatus, such as for example a mobile phone or an embedded processor. A computer can for example comprise a system (network) of "sub-computers", wherein each sub-computer represents a computer in its own right. The term "computer" includes a cloud computer, for example a cloud server. The term computer includes a server resource. The term "cloud computer" includes a cloud computer system which for example comprises a system of at least one cloud computer and for example a plurality of operatively interconnected cloud computers such as a server farm. Such a cloud computer is preferably connected to a wide area network such as the world wide web (WWW) and located in a so-called cloud of computers which are all connected to the world wide web. Such an infrastructure is used for "cloud computing", which describes computation, software, data access and storage services which do not require the end user to know the physical location and / or configuration of the computer delivering a specific service. For example, the term "cloud" is used in this respect as a metaphor for the Internet (world wide web). For example, the cloud provides computing infrastructure as a service (laaS). The cloud computer can function as a virtual host for an operating system and / or data processing application which is used to execute the method of the invention. The cloud computer is for example an elastic compute cloud (EC2) as provided by Amazon Web Services™. A computer for example comprises interfaces in order to receive or output data and / or perform an analogue-to-digital conversion. The data are for example data which represent physical properties and / or which are generated from technical signals. The technical signals are for example generated by means of (technical) detection devices (such as for example devices for detecting marker devices) and / or (technical) analytical devices (such as for example devices for performing (medical) imaging methods), wherein the technical signals are for example electrical or optical signals. The technical signals for example represent the data received or outputted by the computer. The computer is preferably operatively coupled to a display device which allows information outputted by the computer to be displayed, for example to a user. One example of a display device is a virtual reality device or an augmented reality device (also referred to as virtual reality glasses or augmented reality glasses) which can be used as "goggles" for navigating. A specific example of such augmented reality glasses is Google Glass (a trademark of Google, Inc.). An augmented reality device or a virtual reality device can be used both to input information into the computer by user interaction and to display information outputted by the computer. Another example of a display device would be a standard computer monitor comprising for example a liquid crystal display operatively coupled to the computer for receiving display control data from the computer for generating signals used to display image information content on the display device. A specific embodiment of such a computer monitor is a digital lightbox. An example of such a digital lightbox is Buzz®, a product of Brainlab AG. The monitor may also be the monitor of a portable, for example handheld, device such as a smart phone or personal digital assistant or digital media player.

[0082] The invention also relates to a computer program comprising instructions which, when on the program is executed by a computer, cause the computer to carry out the method or methods, for example, the steps of the method or methods, described herein and / or to a computer-readable storage medium (for example, a non-transitory computer- readable storage medium) on which the program is stored and / or to a computer comprising said program storage medium and / or to a (physical, for example electrical, for example technically generated) signal wave, for example a digital signal wave, such as an electromagnetic carrier wave carrying information which represents the program, for example the aforementioned program, which for example comprises code means which are adapted to perform any or all of the method steps described herein. The signal wave is in one example a data carrier signal carrying the aforementioned computer program. The invention also relates to a computer comprising at least one processor and / or the aforementioned computer-readable storage medium and for example a memory, wherein the program is executed by the processor.

[0083] Within the framework of the invention, computer program elements can be embodied by hardware and / or software (this includes firmware, resident software, micro-code, etc.). Within the framework of the invention, computer program elements can take the form of a computer program product which can be embodied by a computer-usable, for example computer-readable data storage medium comprising computer-usable, for example computer-readable program instructions, "code" or a "computer program" embodied in said data storage medium for use on or in connection with the instructionexecuting system. Such a system can be a computer; a computer can be a data processing device comprising means for executing the computer program elements and / or the program in accordance with the invention, for example a data processing device comprising a digital processor (central processing unit or CPU) which executes the computer program elements, and optionally a volatile memory (for example a random access memory or RAM) for storing data used for and / or produced by executing the computer program elements. Within the framework of the present invention, a computer-usable, for example computer-readable data storage medium can be any data storage medium which can include, store, communicate, propagate or transport the program for use on or in connection with the instruction-executing system, apparatus or device. The computer-usable, for example computer-readable data storage medium can for example be, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, apparatus or device or a medium of propagation such as for example the Internet. The computer-usable or computer-readable data storage medium could even for example be paper or another suitable medium onto which the program is printed, since the program could be electronically captured, for example by optically scanning the paper or other suitable medium, and then compiled, interpreted or otherwise processed in a suitable manner. The data storage medium is preferably a non-volatile data storage medium. The computer program product and any software and / or hardware described here form the various means for performing the functions of the invention in the example embodiments. The computer and / or data processing device can for example include a guidance information device which includes means for outputting guidance information. The guidance information can be outputted, for example to a user, visually by a visual indicating means (for example, a monitor and / or a lamp) and / or acoustically by an acoustic indicating means (for example, a loudspeaker and / or a digital speech output device) and / or tactilely by a tactile indicating means (for example, a vibrating element or a vibration element incorporated into an instrument). For the purpose of this document, a computer is a technical computer which for example comprises technical, for example tangible components, for example mechanical and / or electronic components. Any device mentioned as such in this document is a technical and for example tangible device.

[0084] Acquiring data

[0085] The expression "acquiring data" for example encompasses (within the framework of a computer implemented method) the scenario in which the data are determined by the computer implemented method or program. Determining data for example encompasses measuring physical quantities and transforming the measured values into data, for example digital data, and / or computing (and e.g. outputting) the data by means of a computer and for example within the framework of the method in accordance with the invention. A step of “determining” as described herein for example comprises or consists of issuing a command to perform the determination described herein. For example, the step comprises or consists of issuing a command to cause a computer, for example a remote computer, for example a remote server, for example in the cloud, to perform the determination. Alternatively or additionally, a step of “determination” as described herein for example comprises or consists of receiving the data resulting from the determination described herein, for example receiving the resulting data from the remote computer, for example from that remote computer which has been caused to perform the determination. The meaning of "acquiring data" also for example encompasses the scenario in which the data are received or retrieved by (e.g. input to) the computer implemented method or program, for example from another program, a previous method step or a data storage medium, for example for further processing by the computer implemented method or program. Generation of the data to be acquired may but need not be part of the method in accordance with the invention. The expression "acquiring data" can therefore also for example mean waiting to receive data and / or receiving the data. The received data can for example be inputted via an interface. The expression "acquiring data" can also mean that the computer implemented method or program performs steps in order to (actively) receive or retrieve the data from a data source, for instance a data storage medium (such as for example a ROM, RAM, database, hard drive, etc.), or via the interface (for instance, from another computer or a network). The data acquired by the disclosed method or device, respectively, may be acquired from a database located in a data storage device which is operably to a computer for data transfer between the database and the computer, for example from the database to the computer. The computer acquires the data for use as an input for steps of determining data. The determined data can be output again to the same or another database to be stored for later use. The database or database used for implementing the disclosed method can be located on network data storage device or a network server (for example, a cloud data storage device or a cloud server) or a local data storage device (such as a mass storage device operably connected to at least one computer executing the disclosed method). The data can be made "ready for use" by performing an additional step before the acquiring step. In accordance with this additional step, the data are generated in order to be acquired. The data are for example detected or captured (for example by an analytical device). Alternatively or additionally, the data are inputted in accordance with the additional step, for instance via interfaces. The data generated can for example be inputted (for instance into the computer). In accordance with the additional step (which precedes the acquiring step), the data can also be provided by performing the additional step of storing the data in a data storage medium (such as for example a ROM, RAM, CD and / or hard drive), such that they are ready for use within the framework of the method or program in accordance with the invention. The step of "acquiring data" can therefore also involve commanding a device to obtain and / or provide the data to be acquired. In particular, the acquiring step does not involve an invasive step which would represent a substantial physical interference with the body, requiring professional medical expertise to be carried out and entailing a substantial health risk even when carried out with the required professional care and expertise. In particular, the step of acquiring data, for example determining data, does not involve a surgical step and in particular does not involve a step of treating a human or animal body using surgery or therapy. In order to distinguish the different data used by the present method, the data are denoted (i.e. referred to) as "XY data" and the like and are defined in terms of the information which they describe, which is then preferably referred to as "XY information" and the like.

[0086] Image registration

[0087] Image registration is the process of transforming different sets of data into one coordinate system. The data can be multiple photographs and / or data from different sensors, different times or different viewpoints. It is used in computer vision, medical imaging and in compiling and analyzing images and data from satellites. Registration is necessary in order to be able to compare or integrate the data obtained from these different measurements.

[0088] Marker

[0089] It is the function of a marker to be detected by a marker detection device (for example, a camera or an ultrasound receiver or analytical devices such as CT or MRI devices) in such a way that its spatial position (i.e. its spatial location and / or alignment) can be ascertained. The detection device is for example part of a navigation system. The markers can be active markers. An active marker can for example emit electromagnetic radiation and / or waves which can be in the infrared, visible and / or ultraviolet spectral range. A marker can also however be passive, i.e. can for example reflect electromagnetic radiation in the infrared, visible and / or ultraviolet spectral range or can block x-ray radiation. To this end, the marker can be provided with a surface which has corresponding reflective properties or can be made of metal in order to block the x-ray radiation. It is also possible for a marker to reflect and / or emit electromagnetic radiation and / or waves in the radio frequency range or at ultrasound wavelengths. A marker preferably has a spherical and / or spheroid shape and can therefore be referred to as a marker sphere; markers can however also exhibit a cornered, for example cubic, shape.

[0090] Marker device

[0091] A marker device can for example be a reference star or a pointer or a single marker or a plurality of (individual) markers which are then preferably in a predetermined spatial relationship. A marker device comprises one, two, three or more markers, wherein two or more such markers are in a predetermined spatial relationship. This predetermined spatial relationship is for example known to a navigation system and is for example stored in a computer of the navigation system.

[0092] In another embodiment, a marker device comprises an optical pattern, for example on a two-dimensional surface. The optical pattern might comprise a plurality of geometric shapes like circles, rectangles and / or triangles. The optical pattern can be identified in an image captured by a camera, and the position of the marker device relative to the camera can be determined from the size of the pattern in the image, the orientation of the pattern in the image and the distortion of the pattern in the image. This allows determining the relative position in up to three rotational dimensions and up to three translational dimensions from a single two-dimensional image.

[0093] The position of a marker device can be ascertained, for example by a medical navigation system. If the marker device is attached to an object, such as a bone or a medical instrument, the position of the object can be determined from the position of the marker device and the relative position between the marker device and the object. Determining this relative position is also referred to as registering the marker device and the object. The marker device or the object can be tracked, which means that the position of the marker device or the object is ascertained twice or more over time.

[0094] Reference star

[0095] A "reference star" refers to a device with a number of markers, advantageously three markers, attached to it, wherein the markers are (for example detachably) attached to the reference star such that they are stationary, thus providing a known (and advantageously fixed) position of the markers relative to each other. The position of the markers relative to each other can be individually different for each reference star used within the framework of a surgical navigation method, in order to enable a surgical navigation system to identify the corresponding reference star on the basis of the position of its markers relative to each other. It is therefore also then possible for the objects (for example, instruments and / or parts of a body) to which the reference star is attached to be identified and / or differentiated accordingly. In a surgical navigation method, the reference star serves to attach a plurality of markers to an object (for example, a bone or a medical instrument) in order to be able to detect the position of the object (i.e. its spatial location and / or alignment). Such a reference star for example features a way of being attached to the object (for example, a clamp and / or a thread) and / or a holding element which ensures a distance between the markers and the object (for example in order to assist the visibility of the markers to a marker detection device) and / or marker holders which are mechanically connected to the holding element and which the markers can be attached to.

[0096] Surgical navigation system

[0097] A navigation system, such as a surgical navigation system, is understood to mean a system which can comprise: at least one marker device; a transmitter which emits electromagnetic waves and / or radiation and / or ultrasound waves; a receiver which receives electromagnetic waves and / or radiation and / or ultrasound waves; and an electronic data processing device which is connected to the receiver and / or the transmitter, wherein the data processing device (for example, a computer) for example comprises a processor (CPU) and a working memory and advantageously an indicating device for issuing an indication signal (for example, a visual indicating device such as a monitor and / or an audio indicating device such as a loudspeaker and / or a tactile indicating device such as a vibrator) and a permanent data memory, wherein the data processing device processes navigation data forwarded to it by the receiver and can advantageously output guidance information to a user via the indicating device. The navigation data can be stored in the permanent data memory and for example compared with data stored in said memory beforehand. Imaging methods

[0098] In the field of medicine, imaging methods (also called imaging modalities and / or medical imaging modalities) are used to generate image data (for example, two- dimensional or three-dimensional image data) of anatomical structures (such as soft tissues, bones, organs, etc.) of the human body. The term "medical imaging methods" is understood to mean (advantageously apparatus-based) imaging methods (for example so-called medical imaging modalities and / or radiological imaging methods) such as for instance computed tomography (CT) and cone beam computed tomography (CBCT, such as volumetric CBCT), x-ray tomography, magnetic resonance tomography (MRT or MRI), conventional x-ray, sonography and / or ultrasound examinations, and positron emission tomography. For example, the medical imaging methods are performed by the analytical devices. Examples for medical imaging modalities applied by medical imaging methods are: X-ray Radiography (https: / / en.wikipedia.org / wiki / Radiography), magnetic resonance imaging, medical ultrasonography or ultrasound, endoscopy, elastography, tactile imaging, thermography, medical photography and nuclear medicine functional imaging techniques as positron emission tomography (PET) and Single-photon emission computed tomography (SPECT), as mentioned by Wikipedia.

[0099] The image data thus generated is also termed “medical imaging data”. Analytical devices for example are used to generate the image data in apparatus-based imaging methods. The imaging methods are for example used for medical diagnostics, to analyse the anatomical body in order to generate images which are described by the image data. The imaging methods are also for example used to detect pathological changes in the human body. However, some of the changes in the anatomical structure, such as the pathological changes in the structures (tissue), may not be detectable and for example may not be visible in the images generated by the imaging methods. A tumour represents an example of a change in an anatomical structure. If the tumour grows, it may then be said to represent an expanded anatomical structure. This expanded anatomical structure may not be detectable; for example, only a part of the expanded anatomical structure may be detectable. Primary / high-grade brain tumours are for example usually visible on MRI scans when contrast agents are used to infiltrate the tumour. MRI scans represent an example of an imaging method. In the case of MRI scans of such brain tumours, the signal enhancement in the MRI images (due to the contrast agents infiltrating the tumour) is considered to represent the solid tumour mass. Thus, the tumour is detectable and for example discernible in the image generated by the imaging method. In addition to these tumours, referred to as "enhancing" tumours, it is thought that approximately 10% of brain tumours are not discernible on a scan and are for example not visible to a user looking at the images generated by the imaging method.

[0100] Elastic fusion, image fusion / morphing, rigid

[0101] Image fusion can be elastic image fusion or rigid image fusion. In the case of rigid image fusion, the relative position between the pixels of a 2D image and / or voxels of a 3D image is fixed, while in the case of elastic image fusion, the relative positions are allowed to change.

[0102] In this application, the term "image morphing" is also used as an alternative to the term "elastic image fusion", but with the same meaning.

[0103] Elastic fusion transformations (for example, elastic image fusion transformations) are for example designed to enable a seamless transition from one dataset (for example a first dataset such as for example a first image) to another dataset (for example a second dataset such as for example a second image). The transformation is for example designed such that one of the first and second datasets (images) is deformed, for example in such a way that corresponding structures (for example, corresponding image elements) are arranged at the same position as in the other of the first and second images. The deformed (transformed) image which is transformed from one of the first and second images is for example as similar as possible to the other of the first and second images. Preferably, (numerical) optimisation algorithms are applied in order to find the transformation which results in an optimum degree of similarity. The degree of similarity is preferably measured by way of a measure of similarity (also referred to in the following as a "similarity measure"). The parameters of the optimisation algorithm are for example vectors of a deformation field. These vectors are determined by the optimisation algorithm in such a way as to result in an optimum degree of similarity. Thus, the optimum degree of similarity represents a condition, for example a constraint, for the optimisation algorithm. The bases of the vectors lie for example at voxel positions of one of the first and second images which is to be transformed, and the tips of the vectors lie at the corresponding voxel positions in the transformed image. A plurality of these vectors is preferably provided, for instance more than twenty or a hundred or a thousand or ten thousand, etc. Preferably, there are (other) constraints on the transformation (deformation), for example in order to avoid pathological deformations (for instance, all the voxels being shifted to the same position by the transformation). These constraints include for example the constraint that the transformation is regular, which for example means that a Jacobian determinant calculated from a matrix of the deformation field (for example, the vector field) is larger than zero, and also the constraint that the transformed (deformed) image is not self-intersecting and for example that the transformed (deformed) image does not comprise faults and / or ruptures. The constraints include for example the constraint that if a regular grid is transformed simultaneously with the image and in a corresponding manner, the grid is not allowed to interfold at any of its locations. The optimising problem is for example solved iteratively, for example by means of an optimisation algorithm which is for example a first-order optimisation algorithm, such as a gradient descent algorithm. Other examples of optimisation algorithms include optimisation algorithms which do not use derivations, such as the downhill simplex algorithm, or algorithms which use higher-order derivatives such as Newton-like algorithms. The optimisation algorithm preferably performs a local optimisation. If there is a plurality of local optima, global algorithms such as simulated annealing or generic algorithms can be used. In the case of linear optimisation problems, the simplex method can for instance be used.

[0104] In the steps of the optimisation algorithms, the voxels are for example shifted by a magnitude in a direction such that the degree of similarity is increased. This magnitude is preferably less than a predefined limit, for instance less than one tenth or one hundredth or one thousandth of the diameter of the image, and for example about equal to or less than the distance between neighbouring voxels. Large deformations can be implemented, for example due to a high number of (iteration) steps.

[0105] The determined elastic fusion transformation can for example be used to determine a degree of similarity (or similarity measure, see above) between the first and second datasets (first and second images). To this end, the deviation between the elastic fusion transformation and an identity transformation is determined. The degree of deviation can for instance be calculated by determining the difference between the determinant of the elastic fusion transformation and the identity transformation. The higher the deviation, the lower the similarity, hence the degree of deviation can be used to determine a measure of similarity.

[0106] A measure of similarity can for example be determined on the basis of a determined correlation between the first and second datasets.

[0107] BRIEF DESCRIPTION OF THE DRAWINGS

[0108] In the following, the invention is described with reference to the appended figures which give background explanations and represent specific embodiments of the invention. The scope of the invention is however not limited to the specific features disclosed in the context of the figures, wherein

[0109] Figure 1 shows a medical system for implementing the invention;

[0110] Figure 2 shows registering a first fluoroscopic image with a patient model and generating display image data;

[0111] Figure 3 shows registering a first angiographic image with the patient model and updating the display image data;

[0112] Figure 4 shows registering a second fluoroscopic image with the patient model and updating the display image data;

[0113] Figure 5 shows registering a second angiographic image with the patient model and updating the display image data;

[0114] Figure 6 shows registering a third fluoroscopic image with the patient model and updating the display image data;

[0115] Figure 7 shows registering a third angiographic image with the patient model and updating the display image data;

[0116] Figure 8 shows the display image data with a filled gap;

[0117] Figure 9 shows a live fluoroscopic image registered with the fluoroscopic images;

[0118] Figure 10 shows overlapped areas of angiographic images; and

[0119] Figure 11 shows a flow diagram of the invention. DESCRIPTION OF EMBODIMENTS

[0120] Figure 1 is a schematic illustration of a medical system 1 according to the fifth aspect. The system is in its entirety identified by reference sign 1 and comprises a computer 2 comprising a processing unit 4, an electronic data storage device (such as a hard disc) 5, also referred to as memory, for storing different kinds of image data and an interface 6 for connecting the computer 2 to other devices of the system 1 , such as a medical imaging device 3, an input device 7, such as a mouse, a keyboard, a touch sensitive surface, and an output device 8, such as a monitor. The medical imaging device 3, the input device 7 and the output device 8 are also components of the medical system 1 . The components of the medical system 1 have the functionalities and properties explained above with regard to the fifth aspect of this disclosure.

[0121] The medical imaging device 3 is an x-ray imaging device emitting a conical x-ray beam which propagates through a target and hits a detector which converts the incident x- ray radiation into a medical image. The x-ray source and the x-ray detector are for example attached to the same carrier structure, such as a C-arm.

[0122] Figure 2 shows an exemplary application of the system 1 of Figure 1 . In this example, a leg of a patient is imaged.

[0123] First, the medical imaging device 3 is brought into a first viewing position relative to the leg and captures a first fluoroscopic image F1. The first fluoroscopic image F1 is captured without the administration of a contrast agent. The first fluoroscopic image 1 is shown in the upper part of Figure 2.

[0124] The computer 2 registers the first fluoroscopic image F1 with a patient model M, which in the present example is a three-dimensional model of the bones and the vessels of the legs of a patient. The registration determines a first fluoroscopic viewing position as the viewing position from which a virtual imaging device would have captured the first fluoroscopic image F1 when imaging the leg. This in turn defines the area of the leg that is depicted by the first fluoroscopic image F1 . The computer 2 then generates display image data. The display image data is image data to be displayed by a display device like the output device 8. The display image data comprises a pictogram PR being a generic representation of a leg. The display image data further comprises the first fluoroscopic image F1 spatially arranged at a position corresponding to the first fluoroscopic viewing position calculated by the registration described above. The first fluoroscopic image F1 is in particular arranged at a position relative to the pictogram PR such that the area of the pictogram PR overlaid with the first fluoroscopic image F1 coincides with the area of the leg that is actually depicted by the first fluoroscopic image F1 .

[0125] Then, a contrast image, or unprocessed angiographic image, is captured after the administration of a contrast agent and the first angiographic image A1 is calculated as the difference between the contrast image and the fluoroscopic image F1 or a fluoroscopic image captured during the process of capturing the angiographic image. The angiographic image A1 therefore shows a part of the vascular structure of the leg, which is shown in the contrast image, but not in the fluoroscopic image F1 .

[0126] The first angiographic image A1 is shown in the upper part of Figure 3. The computer 2 acquires the first angiographic image A1 and registers it with the patient model M. The registration determines the first angiographic viewing position as the viewing position from which a virtual imaging device would have captured the first angiographic image A1 when imaging the leg. This in turn defines the area of the leg that is depicted by the first angiographic image A1 .

[0127] The computer 2 then updates the display image data. The computer 2 adds the first angiographic image A1 to the display image data, spatially arranged at a position corresponding to the first angiographic viewing position calculated by the registration described above. The first angiographic image A1 is in particular arranged at a position relative to the pictogram PR such that the area of the pictogram PR overlaid with the first angiographic image A1 coincides with the area of the leg that is actually depicted by the first angiographic image A1 . This is shown in the lower part of Figure 3.

[0128] If the medical imaging device 3 has not moved relative to the leg between capturing the first fluoroscopic image F1 and the first angiographic image A1 , then the first fluoroscopic viewing position equals the first angiographic viewing position. If the two first viewing positions differ by more than a predetermined threshold, the computer 2 optionally outputs a corresponding information, for example using the output device 8.

[0129] The computer stores the first fluoroscopic image F1 and the first angiographic image A1 as a first image pair in the memory 5.

[0130] The medical imaging device 3 is then brought into a second position relative to the leg for capturing a second image pair. Figure 4 shows a second fluoroscopic image F2 registered with the patient model M and added to the display image data in the same way as the first fluoroscopic image F1. Figure 5 shows a second angiographic image A2 registered with the patient model M and added to the display image data in the same way as the first angiographic image A1. The computer stores the second fluoroscopic image F2 and the second angiographic image A2 as a second image pair in the memory 5.

[0131] The medical imaging device 3 is then brought into a third position relative to the leg for capturing a third image pair. Figure 6 shows a third fluoroscopic image F3 registered with the patient model M and added to the display image data in the same way as the first fluoroscopic image F1. Figure 7 shows a third angiographic image A2 registered with the patient model M and added to the display image data in the same way as the first angiographic image A1 . The computer stores the third fluoroscopic image F3 and the third angiographic image A3 as a third image pair in the memory 5.

[0132] Instead of the pictogram PR, the display image data may contain a representation of the patient model M, for example a two-dimensional projection of the patient model M. In this case, the fluoroscopic and angiographic images are arranged in the display image data relative to the representation of the patient model M in analogy to the approach described above.

[0133] The display image data can comprise neither the pictogram PR nor the projection of the patient model M. In this case, the angiographic and fluoroscopic images are still arranged in the display image data such that the spatial relations between those images corresponds to the spatial relations between the areas of the patient depicted by the respective images.

[0134] It shall be noted that the display image data may only comprise the current fluoroscopic image as well as some or all of the angiographic images acquired so far, but not the other fluoroscopic image captured before the current fluoroscopic image. As an example, the display image in the lower part of figure 4 would only show the second fluoroscopic image F2, but not the first fluoroscopic image F1 and the display image in the lower part of figure 6 would only show the second fluoroscopic image F3, but not the first fluoroscopic image F1 and the second fluoroscopic image F2.

[0135] As can be seen from Figure 8, there is a gap G between the second image pair and the third image pair. The computer 2 optionally adds image data representing the bony and vascular structures in this gap G to the display image data. The added image data is derived from the patient model M. Since the fluoroscopic and angiographic images of the three image pairs are registered with the patient model M, the computer knows which areas of the patient model M are represented by the image pairs. The computer 2 can thus calculate the area of the patient model M from which data has to be taken for calculating the image data to add.

[0136] The computer 2 can optionally use information from the patient model M to supplement an image pair. The image data added to the display image data can alternatively or additionally be added to an image pair to extend the field of view covered by this image pair. The supplemented image pair can then be used in the subsequent steps rather than the original image pair.

[0137] The computer 2 then acquires a live fluoroscopic image FL from the medical imaging system 3. Figure 9 shows the live fluoroscopic image FL relative to the fluoroscopic images F1 to F3 of the three image pairs. In the present example, the live fluoroscopic image FL overlaps with the first fluoroscopic image F1 and the second fluoroscopic image F2.

[0138] More details of the overlap are shown in Figure 10. The live fluoroscopic image overlaps the first image pair and thus the fluoroscopic image F1 and the angiographic image A1 in the overlapped area 01 . Similarly, the live fluoroscopic image FL overlaps the second image pair, and thus the fluoroscopic image F2 and the angiographic image A2, in the overlapped area 02. The hatched areas shown in Figure 10 are those areas in which the overlapped areas 01 and 02 themselves overlap each other. In the area in which the two overlapped areas 01 and 02 overlap, the angiographic information to be overlayed over the live fluoroscopic image FL can be derived from the angiographic image A1 , the angiographic image A2 or a combination thereof.

[0139] In the example shown in Figure 10, the overlapped area 02 is larger than the overlapped area 01. In fact, there is only a small area of the live fluoroscopic image FL which does not overlap the angiographic image A2. In this case, the angiographic image data of the overlapped area 02 of the angiographic image A2 is determined as the angiographic overlay image data and overlayed over the live fluoroscopic image FL. Depending on for example the fraction of the live fluoroscopic image FL which does not overlap with the angiographic image A2, the angiographic overlay image data may or may not be supplemented by angiographic image data of the angiographic image A1 in the overlapped area 01 .

[0140] If the angiographic overlay image data is supplemented with angiographic image data of the angiographic image A1 , there can be a hard transition between the angiographic image data taken from the angiographic image A2 and the angiographic image data taken from the angiographic image A1. However, there can also be a smooth or blended transition in the area or part of the area in which the overlapped areas 01 and 02 overlap.

[0141] Figure 1 1 shows a flow diagram of an exemplary embodiment of the present invention. Steps S01 to S06 form the acquisition phase, while steps S07 to S10 form the live phase.

[0142] At step S01 , an image is acquired. The image is a fluoroscopic image or an angiographic image. At step S02, the image acquired at step S01 is registered with a patient model M. This establishes a spatial relationship between the acquired image and the patient model M. The result of step S02 is for example a viewing position of the imaging device 3 relative to the patient model M, and thus relative to the patient, at the time of capturing the image.

[0143] At step 03, display image data is generated. The display image data comprises a representation of the patient model M in terms of a two-dimensional projection of the patient model M. The image acquired at step S01 is added to the display image data at a position corresponding to the viewing position determined in step S02. The image is overlaid over the representation of the patient model M. In particular, the position of the image in the display image data over the representation of the patient model M corresponds to the spatial relationship between the image and the patient model M.

[0144] At step S04, the display image data is displayed. At step S05, the image acquired at step S01 is stored, for example in the memory 5.

[0145] At step S06, it is determined whether or not the acquisition is complete. This is for example determined based on an input of an operator.

[0146] If the acquisition is not complete, the method returns to step S01 to acquire a new image. The new image can also be a fluoroscopic image or an angiographic image.

[0147] Typically, the imaging device 3 is positioned relative to the patient, a fluoroscopic image and an angiographic image are captured (in this or reverse order) to form an image pair, the imaging device 3 is repositioned and a new image pair is captured. However, this sequence is not mandatory since the method can find a pair of a fluoroscopic image and an angiographic image captured from the same viewing position irrespective of the order in which the images are captured.

[0148] If a fluoroscopic image and an angiographic image have been captured with the same viewing position, step S05 stores those images as an image pair. The two images are thus associated with each other.

[0149] In a second or higher iteration of steps S01 to S06, the display image data generated in step S03 can comprise only the representation of the patient model M and the latest acquired image. However, it is preferable that the display image data also comprises images acquired in some or all of the previous iterations to show which areas of the patient have already been imaged. The display image data for example comprises some or all angiographic images of the previous iterations, but only the fluoroscopic image of the current iteration.

[0150] If it is determined at step S06 that the acquisition is complete, the method proceeds to step S07 at which a live fluoroscopic image is captured and acquired. At step S08, the live fluoroscopic image is registered with the fluoroscopic image of at least one image pair. It is thus determined in how far the live fluoroscopic image overlaps with the fluoroscopic images in the image pairs.

[0151] At step S09, angiographic overlay image data is generated. The angiographic overlay image data comprises image information taken from image pairs whose fluoroscopic image overlaps with the live fluoroscopic image. Since the viewing positions of the fluoroscopic image and the angiographic image of an image pair are the same, the overlap of the live fluoroscopic image with the fluoroscopic image of an image pair is the same as the overlap of the live fluoroscopic image with the angiographic image of said image pair.

[0152] At step S10, the angiographic overlay image data is overlaid over the live fluoroscopic image and the result is displayed. The live fluoroscopic image is thus enriched with the vascular structure of the patient without the need to acquire a live angiographic image.

Claims

CLAIMS1. A data processing method of overlaying angiographic information over a fluoroscopic image of a patient, the method comprising the steps of:- acquiring at least one image pair data, each image pair data representing an image pair and comprising fluoroscopic image data and angiographic image data representing a fluoroscopic image (F1 , F2, F3) and an angiographic image (A1 , A2, A3), respectively, of a part of the patient, the fluoroscopic image and the angiographic image of an image pair being taken using the same viewing position, the viewing position being the position of the imaging device relative to the patient when capturing an image,- generating display image data from the at least one image pair data, wherein the image pair data are spatially arranged in the display image data based on the corresponding viewing position of the image pair,- displaying the display image data,- acquiring live fluoroscopic image data representing a live fluoroscopic image (FL) of the patient,- registering the live fluoroscopic image data with the fluoroscopic image data of at least one of the at least one image pair, thus obtaining the spatial orientation between the live fluoroscopic image (FL) and the image pair,- determining angiographic overlay image data (V) from the angiographic image data based on the spatial orientation between the live fluoroscopic image (FL) and the at least one of the at least one image pair, and- overlaying the angiographic overlay image data (V) over the live fluoroscopic image (FL).

2. The method of claim 1 , wherein a viewing position of an image pair includes a fluoroscopic viewing position and an angiographic viewing position.

3. The method of claim 2, wherein the fluoroscopic viewing position of an image pair is calculated by registering the fluoroscopic image data of the image pair with apatient model and the angiographic viewing position of an image pair is calculated by registering the angiographic image data of the image pair with the patient model.

4. The method of claim 3, wherein the patient model is a generic patient model representing the generic bony and vascular structure of at least a part of a generic patient.

5. The method of claim 3, wherein the patient model represents a scan of the bony structure and a scan of the vascular structure of at least a part of the patient.

6. The method of any one of claims 3 to 5, wherein registering the angiographic image data with the patient model uses information on the bony structure of the patient in the angiographic image data.

7. The method of any one of claims 3 to 6, further comprising the step of outputting indication information if the calculated fluoroscopic viewing position differs from the calculated angiographic viewing position by more than a predetermined threshold.

8. The method of any one of claims 3 to 7, wherein generating display image data includes adding a representation of the patient model to the display image data.

9. The method of claim 1 or 2, wherein a viewing position of an image is determined from the position of the imaging device and the position of the patient when capturing the image.

10. The method of claim 1 or 2, wherein a viewing position of an image is determined from the relative position of the patient to the imaging device when capturing the image.11 . The method of any one of claims 1 to 10, wherein the step of acquiring at least one image pair data comprises acquiring two or more image pair data and a gap in the display image data between two image pair data is filled with image data taken from a patient model.

12. The method of any one of claims 9 to 11 in combination with claim 2 or any one of claims 3 to 8, wherein if the fluoroscopic viewing position differs from the angiographic viewing position for an image pair, at least one of the fluoroscopic image data and the angiographic image data of this image pair is supplemented from a patient model.

13. The method of any one of claims 1 to 12, wherein the step of acquiring at least one image pair data comprises acquiring two or more image pair data, further comprising the steps of:- calculating a set of image pair registration data, each image pair registration data representing the spatial orientation between two overlapping image pairs; and- calculating angiographic panoramic image data from the angiographic image data of the image pairs based on the set of image pair registration data, wherein determining the angiographic overlay image data involves selecting a part of the angiographic panoramic image data.

14. A computer program comprising instructions which, when the program is executed by a computer (2), cause the computer (2) to carry out the method according to any one of the preceding claims; and / or a computer-readable storage medium on which the program is stored; and / or a computer (2) comprising at least one processor (4) and / or the program storage medium, wherein the program is executed by the processor (4); and / or a data carrier signal carrying the program; and / or a data stream comprising the program.

15. A medical system (1 ), comprising: the at least one computer (2) according to the preceding claim 14; and a medical imaging system (3).

16. Use of the system according to the preceding claim for conducting a medical procedure, wherein the use comprises execution of the steps of the method according to any one of the preceding method claims for overlaying angiographic information over a fluoroscopic image of a patient.

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