Imaging method and imaging apparatus

Abstract

In the imaging method, a first image (B1) representing a portion of an object to be mapped is generated at a first recording time by means of an imaging apparatus (1), and a second image (B2) representing the portion of the object to be mapped is generated at a second recording time which is subsequent to the first recording time. A further first image (B1') is generated on the basis of the first image (B1) using a preset model which is related to a temporal evolution of a contrast agent present in the object to be mapped at the time of generating the first image (B1), the further first image taking into account the temporal evolution of the contrast agent from the first recording time to the second recording time. A further second image (B2') is generated from the second image (B2) and the further first image (B1'), in which further second image the influence of the contrast agent on the second image (B2) is at least partially compensated.

Description

TECHNICAL FIELD

[0001] The invention relates to an imaging method, wherein a first image representing a portion of an object to be mapped is generated by means of an imaging apparatus at a first recording time and a second image representing the portion of the object to be mapped is generated at a second recording time following the first recording time. The invention also relates to a corresponding imaging apparatus and computer program product. BACKGROUND

[0002] In imaging methods, in particular medical imaging methods, for example imaging methods using X-rays or other ionizing radiation, contrast agents can be used in order to highlight structures, for example tube structures, in the object to be mapped (abbilden, or imaged) which are not visible or cannot be clearly seen in the corresponding image. It is possible here to use contrast agents at different points in time, wherein different types of contrast agents or the same contrast agent can be involved. It can thus happen that when an image is generated after the use (Gabe) of a defined contrast agent, there is still contrast agent from an earlier use remaining, which can undesirably lead to other structures being highlighted in the image.

[0003] In subtraction angiography, two different images of the object to be mapped are required to be recorded (or taken) in succession, wherein an image is first generated which nominally uses no contrast agent and an image is then generated which uses contrast agent. The two images are registered with one another and subtracted. In the ideal case, in the resulting subtraction image only those structures, in particular tube structures, can be seen which are highlighted due to the use of contrast agent. Here, for example, contrast agent residues can undesirably be present in the first image which is also referred to as a mask image, which can ultimately lead to artifacts in the subtraction image.

[0004] It is furthermore known to segment images generated by means of a corresponding imaging apparatus, i.e. to identify different regions in the image which correspond to different types of structures, for example tissue types, etc. For this purpose high-performance image processing algorithms or image analysis algorithms can be used. These algorithms are in particular also able to identify tube structures and bone structures and regions highlighted by contrast agent.

[0005] The publication by D. Lesage et al.: "A review of 3D vessel lumen segmentation techniques: Models, features and extraction schemes", medical image analysis 13(6), 2009, 819-845, for example, summarizes the corresponding state of the art of the literature for vessel segmentation, in particular in the context of contrast-enhanced 3D imaging modules. SUMMARY

[0006] The technical problem addressed by the present application is to reduce the influence of undesired contrast agent residues in images of an imaging method.

[0007] The technical problem is solved by an imaging method, an imaging apparatus and a computer program product having instructions.

[0008] The idea underlying the present application is to modify the first image taking into account the temporal evolution of a contrast agent intentionally or unintentionally present in the object to be mapped here and to at least partially compensate for the influence of the contrast agent in the second image recorded after the first image taking into account the modified first image.

[0009] According to one aspect of the present application, an imaging method is specified in which a first image representing an object to be mapped is generated by means of an imaging apparatus at a first recording time. A second image representing the object to be mapped is generated at a second recording time after the first recording time. On the basis of the first image, in particular by means of at least one computing unit of the imaging apparatus, a further first image is generated using a preset model relating to the temporal evolution of a contrast agent present in the object to be mapped at the time of generating the first image. The further first image, which can also be referred to as a modified first image, takes into account the temporal evolution of the contrast agent from the first recording time to the second recording time. From the second image and from the further first image, in particular by means of the at least one computing unit, a further second image is generated. In the further second image, the influence of the contrast agent on the second image is at least partially compensated for.

[0010] The imaging method, also referred to as the method of imaging or simply as imaging, can be understood to be a method by means of which image data or image-like views, in particular two- and / or three-dimensional image data or views, of an object to be mapped can be generated. If reference is made to medical imaging, the object is a human or animal patient or one or more body parts, organs or other anatomical structures. However, the imaging method can also be used for non-living objects, for example for material analysis. The imaging module can be understood to be a device which is set up to carry out the main part or the entire imaging method. For this purpose, the imaging module has at least one sensor apparatus for detecting the respective physical quantities used to generate the image data, wherein the design of the sensor apparatus varies depending on the type of imaging. Different types of imaging are based on the use of X-rays, radionuclides, ultrasound waves or magnetic fields. The sensor apparatus accordingly comprises one or more suitable sensors and, if necessary, one or more corresponding sources.

[0011] In the imaging method according to the application, the object to be mapped is for example a part of a patient's body, in particular one or more organs or parts of one or more organs, wherein the term "organ" also includes hollow organs, i.e. in particular tubes, for example blood vessels or lymph vessels, in particular.

[0012] Depending on the design form of the specific imaging method, the data acquisition required for generating the image takes a certain period of time. In other design forms of the imaging method, the image can be generated substantially by instantaneous photography. The first and second recording times can accordingly be a respective point in time or a respective period of time. In the case of a period of time, the first recording time can be referred to as a first recording period and the second recording time can be referred to as a second recording period. In this case, the first and second recording periods are for example separated from one another, i.e. the recording periods do not overlap. Accordingly, the first recording period begins at a first start point in time and ends at a first end point in time, and the second recording period begins at a second start point in time and ends at a second end point in time. The second start point in time is here in particular after the first end point in time.

[0013] The reason why the contrast agent is present in the object to be mapped at the time of generating the first image can be that the contrast agent has been intentionally administered for generating the first image, i.e. for the case of a human or animal patient, the contrast agent has been introduced into the object, for example by injection or orally or the like, before or during the generation of the first image, in order to deliberately highlight certain regions of the object to be mapped in the first image. However, the contrast agent can also be present as an undesired contrast agent residue from an earlier imaging at the time of generating the first image. However, the step of administering the contrast agent is not part of the imaging method according to the application. In other words, it is taken as a starting point when the imaging method is carried out that the contrast agent has been administered accordingly or is being administered, or that the contrast agent is present in the object to be mapped for other reasons.

[0014] Depending on the type of contrast agent used, the contrast agent can undergo different dynamic changes over time after it has been administered in the object. The spatial distribution of the contrast agent in the object can change in particular as a function of time. Contrast agents injected into a tube structure or contrast agents taken orally can for example be flushed out of the tube structure over time, for example by a corresponding fluid flow in the tube structure, for example a blood flow or a lymph flow. For some contrast agents, for example small gas bubbles or micro-particles such as embolisation pellets, these particles can also decompose over time, so that not only the local concentration of the contrast agent changes over time, but also the absolute amount of the contrast agent changes over time. Metabolic processes or fluorescence fading can also contribute to the decomposition or degradation of the contrast agent.

[0015] The model relating to the evolution of the contrast agent over time reflects properties of the contrast agent used respectively as a function of time (or vice versa). The model may, for example, characterize a spatial distribution and / or a concentration of the contrast agent depending on time. Thus, depending on the time interval between the second recording time and the first recording time, the model can provide information about the apparent degree of the contrast agent in the imaging. For this purpose, for example, the original spatial distribution of the contrast agent according to the first image and / or the original concentration of the contrast agent and / or the respective intensity values in the first image can be preset as input information to the model, and at least one computing unit can predict or estimate the evolution of the distribution and / or the concentration of the contrast agent or other properties over time using the model. The further first image then corresponds to the first image, however, wherein it is assumed that the contrast agent has evolved over the time interval between the first and the second recording time period.

[0016] In addition to the properties of the contrast agent, the model can also include properties of the object, for example, regarding the tube type or the material composition or structure of the object, and can take these into account when generating the further first image.

[0017] If the first recording time and the second recording time are respective time periods, the time interval can be, for example, the time interval between the first end time point and the second start time point here. Other reference time points can alternatively be used, for example, the time interval between the first start time point and the second start time point, etc.

[0018] In other words, assuming that the object has not changed at all between the first recording time and the second recording time and that the model is completely accurate, it can be expected that the second image is identical to the further first image. However, this is generally not the case. In addition to the model usually being based on assumptions that do not necessarily apply exactly, the first image and the second image can also differ from one another in other respects, for example. For example, individual components of the object, for example soft tissue, can move, and / or a tool, for example a catheter or a biopsy needle, etc., can be introduced into the object, and / or further contrast agent can be administered to generate the second image, etc. Thus, even if the model is assumed to reflect the true evolution of the contrast agent over time exactly, the further first image is generally different from the second image.

[0019] The first and / or the second image can also be preprocessed images, for example, a segmentation algorithm can be performed based on the respective raw image to generate the first and / or the second image. For example, if the first image is a segmented image, the further first image is also generated, for example, as a segmented image.

[0020] In the imaging method according to the application, the contrast agent present when the first image is generated appears as an undesired residue when the second image is generated. This contrast agent is not used, in particular, purposefully for generating the second image. Thus, in the further second image, the influence of the contrast agent is at least partially compensated. This, however, does not necessarily involve, preferably does not involve, a further contrast agent which can be used for generating the second image. In the following, the contrast agent present when the first image is generated is referred to as contrast agent and the contrast agent used, if necessary purposefully, for generating the second image is referred to as further contrast agent, unless stated otherwise. This, however, does not exclude the possibility that the contrast agent and the further contrast agent are the same substance.

[0021] The compensation of the influence of the contrast agent can be realized in different ways. For example, the regions formed in the further first image due to the presence of the contrast agent can be marked in the further second image, so that the user can take this into account when analyzing the further second image. In this case, the compensation is realized by providing additional information, for example, which image regions in the further second image can be contrast agent residues of the contrast agent used for generating the first image. However, the compensation can also be realized in such a way that the regions in the second image which are formed due to the presence of the contrast agent are removed from the second image to generate the further second image. These regions can be adapted to their respective surroundings in the further second image, for example, or can also be replaced by image regions known from the reference record.

[0022] However, the compensation can also be realized in such a way that the second image is subtracted from the further first image or, conversely, the further first image is subtracted from the second image, so that the regions formed due to the presence of the contrast agent are removed from the second image, while other differences between the first image and the second image or between the further first image and the second image, for example, changes due to the introduction of a tool or the use of a further contrast agent, remain in the further second image. In other words, the further first image can be used, for example, instead of the first image as a mask image in a subtraction imaging method, in particular a subtraction angiography method.

[0023] Thus, by means of the imaging method according to the application, the undesired influence of the contrast agent used for generating the first image in the second image or the further second image can be reduced. Thus, in particular, it is achieved by the application that images of an object are generated successively at short intervals, wherein the influence of the respective contrast agent can be avoided, in particular, when settling accounts, for example, subtracting, with the following image.

[0024] The imaging method is, for example, an X-ray-based imaging method, in particular an angiography method.

[0025] In different designs of the imaging method, a second image mapping is used for an additional contrast agent to generate the second image. As mentioned above regarding the contrast agent, the step of applying this additional contrast agent is not part of the imaging method.

[0026] Therefore, the second image maps both the additional contrast agent and any undesirable residues of that contrast agent. By at least partially compensating for the effects of the contrast agent, the influence of the additional contrast agent, particularly its impact on the desired outcome of the second image, can be analyzed more reliably.

[0027] According to at least one embodiment, the model involves the spatial distribution and / or concentration of the contrast agent as a function of time.

[0028] Therefore, the evolution of contrast agents over time corresponds to the changes in their spatial distribution and / or concentration over time.

[0029] According to at least one embodiment of the imaging method, a difference image is generated by subtracting another first image from a second image or by subtracting a second image from another first image. The other second image is generated based on or corresponds to the difference image.

[0030] Therefore, in these embodiments, the imaging method can also be referred to as a subtraction imaging method. Here, the aforementioned use or application of the additional contrast agent is specifically for generating a second image. If the tubular structures in the second image are highlighted due to the use of the second contrast agent, then this imaging method is particularly a subtraction angiography method.

[0031] It has been proven that the present invention is particularly advantageous in this respect because the principle of subtraction imaging is based on the assumption that anatomical structures are not highlighted by contrast agents in the corresponding mask image, but only in the object image recorded later, also known as the fill-bild image.

[0032] Relatedly, the contrast agent is undesirable in both the first and second images. If the first image is used as a mask image, the contrast agent in the resulting difference image is only insufficiently compensated because the evolution over time is not taken into account.

[0033] In other designs of the imaging method, between the generation of the first image and the generation of the second image, an additional image of the object can be generated by means of an imaging device or other imaging device.

[0034] According to at least one embodiment, the imaging apparatus is designed for a method of subtraction imaging, in particular for a method of subtraction angiography. The further first image here corresponds to a mask image of the subtraction imaging, in particular the further first image is used as a mask image. The second image corresponds to an object image of the subtraction imaging, i.e. in particular is used as an object image, wherein the object image is also referred to as a vessel image in the case of subtraction angiography.

[0035] Thus, in these embodiments, in particular a further contrast agent is used to generate the second image.

[0036] Thus, the mask image shows static structures or background structures, for example bone structures or the like, and shows undesired residues of the contrast agent in consideration of the evolution over time of the contrast agent, whereas it does not show the further contrast agent. In contrast, the tube image shows both the static structures of the mask image and the further contrast agent, i.e. for example the highlighted tube structure, and the changed residues of the contrast agent over time.

[0037] By using the further first image as a mask image, instead of for example using the first image as a mask image, the changed, undesired residues of the contrast agent in the second image can be compensated for.

[0038] According to at least one embodiment, the first image is segmented, in particular by means of at least one computing unit. The further first image and / or the further second image are generated on the basis of the segmented first image.

[0039] By segmentation, in particular different regions in the first image are identified, which can be assigned to different types of structures, tissues, etc.

[0040] Thus, in order to generate the further first image, the region of the segmented first image which corresponds to the contrast agent according to the segmentation can for example be subjected to an evolution over time according to a model. In order to generate the further second image, for example image registration can be carried out with the static structures identified according to the segmentation of the segmented first image.

[0041] According to at least one embodiment, the generation of the further first image comprises changing, or rather modifying, the first region of the segmented first image which represents the contrast agent, in accordance with the model of the evolution over time of the contrast agent from the first recording time to the second recording time.

[0042] The further first image then contains, in particular, the first region which has changed in correspondence with the model, but not the first region which represents the contrast agent. The model can thus be applied specifically to the region of the contrast agent, thereby making the temporal development of the contrast agent in the further first image more accurate. The other regions of the segmented first image which do not represent the contrast agent can be changed in accordance with other models, or not at all, in order to produce the further first image.

[0043] According to at least one embodiment, the second image is segmented and a second region in the segmented second image is determined which corresponds to the changed first region of the first image. In order to produce a further second image, the second region is removed or partially removed from the segmented second image.

[0044] According to at least one embodiment, a further first region of the segmented first image is determined which corresponds to fixed anatomical structures, also referred to as static anatomy. The second image is segmented and a further second region of the segmented second image is determined which corresponds to the fixed anatomical structures. From the further first region and the further second region, in particular by means of at least one computing unit, a transformation for image registration is determined. The further second image is produced in accordance with the transformation.

[0045] For application scenarios or application cases which can be given in the method and are not explicitly described here, it can be provided that an error report is output and / or a request for inputting user feedback is output and / or a standard setting and / or a predetermined original state is adjusted in accordance with the method.

[0046] An imaging apparatus is given according to another aspect of the present application. The imaging apparatus has an imaging module which is provided for producing a first image which represents an object to be mapped at a first recording time and for producing a second image which represents the object to be mapped at a second recording time which is subsequent to the first recording time. The imaging apparatus has at least one computing unit which is provided for producing a further first image on the basis of the first image using a preset model which is related to a temporal development of a contrast agent which was present in the object to be mapped at the time of producing the first image, the further first image taking into account the temporal development of the contrast agent from the first recording time to the second recording time. The at least one computing unit is provided for producing a further second image from the second image and the further first image in which the influence of the contrast agent on the second image is at least partially compensated.

[0047] The imaging module can have one or more control units, wherein the at least one computing unit can comprise or partially comprise the at least one control unit, or vice versa, the at least one control unit can comprise or partially comprise the at least one computing unit.

[0048] According to at least one embodiment of the imaging apparatus, the imaging module is designed as an X-ray-based imaging module.

[0049] In other words, the imaging module comprises an X-ray source and an X-ray sensitive sensor unit.

[0050] Further embodiments of the imaging apparatus according to the application directly result from the different design options of the method according to the application and vice versa. Individual features and the respective explanations and advantages with regard to the different embodiments of the method according to the application can be transferred analogously to the corresponding embodiments of the imaging apparatus according to the application. The imaging apparatus according to the application is in particular designed or programmed for carrying out the method according to the application. The imaging apparatus according to the application carries out in particular the method according to the application.

[0051] The computing unit can in particular be understood as a data processing device comprising a processing circuit. That is, the computing unit can in particular process data for carrying out a computing run. This also includes operations or runs for carrying out index accesses to data structures, for example, Umsetzungstabelle, LUT (English: "look-up table"), as necessary.

[0052] The computing unit can in particular comprise one or more computers, one or more microcontrollers and / or one or more integrated circuits, for example, one or more application-specific integrated circuits, ASIC (English: "application-specific integrated circuit"), one or more field-programmable gate arrays, FPGA, and / or one or more system on a chip, SoC (English: "system on a chip"). The computing unit can also comprise one or more processors, for example, one or more microprocessors, one or more central processing unit, CPU (English: "central processing unit"), one or more graphics processing unit, GPU (English: "graphics processing unit"), and / or one or more signal processors, in particular one or more digital signal processors, DSP. The computing unit can also comprise a physical or virtual complex of computers or other mentioned units.

[0053] In different embodiments, the computing unit comprises one or more hardware interfaces and / or software interfaces and / or one or more memory units.

[0054] The memory unit can be designed as a volatile data memory, for example a dynamic random access memory, DRAM (English: "dynamic random access memory"), or a static random access memory, SRAM (English: "static random access memory"), or as a non-volatile data memory, for example a read-only memory, ROM (English: "read-only memory"), a programmable read-only memory, PROM (English: "programmable read-only memory"), an erasable programmable read-only memory, EPROM (English: "erasable programmable read-only memory"), an electrically erasable programmable read-only memory, EEPROM (English: "electrically erasable programmable read-only memory"), a flash memory or a flash electrically erasable programmable read-only memory, a ferroelectric random access memory, FRAM (English: "ferroelectric random access memory"), a magnetoresistive random access memory, MRAM (English: "magnetoresistive random access memory"), or a phase-change random access memory, PCRAM (English: "phase-change random access memory").

[0055] A computer program having instructions is given according to another aspect of the application. The instructions cause the imaging apparatus to perform the imaging method according to the application when the computer program is executed by the imaging apparatus according to the application, in particular by the at least one computing unit.

[0056] A computer-readable storage medium having stored the computer program according to the application is given according to another aspect of the application.

[0057] The computer program and the computer-readable storage medium can be understood as corresponding computer program products having instructions.

[0058] Further features of the application result from the figures and the description of the figures. The features and feature combinations mentioned above in the description and those mentioned below in the description of the figures and / or shown in the figures can be present individually or in any combination with each other. Design solutions and feature combinations that do not have all the features of the claims as originally worded can in particular also be included in the application. Furthermore, design solutions and feature combinations that go beyond or differ from the feature combinations set out in the claims in terms of their wording can also be included in the application. Attached Figure Description

[0059] The present invention will now be described in detail with reference to specific embodiments and corresponding schematic views. In the accompanying drawings, elements that are identical or functionally identical may be provided with the same reference numerals. Elements that are identical or functionally identical may not necessarily be described repeatedly in different figures.

[0060] In the attached diagram:

[0061] Figure 1 A schematic diagram of an exemplary embodiment of the imaging apparatus according to the present invention is shown;

[0062] Figure 2 A schematic flowchart illustrating an exemplary embodiment of the imaging method according to the present invention is shown; and

[0063] Figure 3 A flowchart of another exemplary embodiment of the imaging method according to the present invention is shown. Detailed Implementation

[0064] Figure 1 An exemplary embodiment of the imaging device 1 according to the invention is illustrated schematically. The imaging device has an imaging module 3, which may be designed, for example, as an X-ray-based imaging module having an X-ray source 4 and an X-ray sensor 5. The imaging device may optionally have a patient bed 2. The imaging device 1 has a computing unit 6, which may represent two or more computing units in different embodiments.

[0065] Imaging apparatus 1 is particularly configured to perform the imaging method according to the invention. Figure 2 In an exemplary embodiment, a flowchart of such an imaging method is shown.

[0066] Here, in step 201, a first image B1 is generated using the imaging module 3 at a first recording time. This first image represents the object to be mapped, such as an organ. In step 202, a second image B2 is generated using the imaging module 3 at a second recording time following the first recording time. This second image also represents the object to be mapped.

[0067] exist Figure 2In the example, the first image B1 maps to contrast agent residue 8. The contrast agent may have been specifically used to generate the first image B1, or it may be unwanted contrast agent residue from previous image generation. Between the first and second recording periods, the contrast agent undergoes a change over time, resulting in a change in its spatial distribution and / or concentration within the object. Therefore, the second image B2 maps to the altered contrast agent residue 10. The difference between contrast agent residue 8 and altered residue 10 lies here in the change in the spatial distribution and / or concentration of the contrast agent over time.

[0068] In addition, Figure 2 In the current example, an additional contrast agent was used to produce a second image B2, which shows the tube structure 11 highlighted by the additional contrast agent.

[0069] In step 203, the calculation unit 3 generates another first image B1' based on the first image B1 using a preset model that takes into account the evolution of the contrast agent causing residues 8 and 10 over time from the first recording time to the second recording time. Therefore, the other first image B1' also shows the altered residue 9 of the contrast agent. If the preset model accurately reflects the evolution of the contrast agent over time, then the altered residue 9 in the other first image B1' is the same as the altered residue 10 in the second image B2. In any case, the altered residue 9 corresponds at least approximately to the altered residue 10 in the second image B2.

[0070] In step 204, the calculation unit 3 generates an additional second image B2' based on the additional first image B1' and the second image B2, in which the effect of the contrast agent causing the residues 8 and 10 is at least partially compensated. For this purpose, the calculation unit 3 may, for example, use the additional first image B1' as a mask image and subtract it from the second image B2. Therefore, in the resulting additional second image B2', the tube structure 11 is still displayed, but the contrast agent residue 10 is eliminated or partially eliminated.

[0071] Figure 3 A flowchart of another exemplary embodiment of the imaging method according to the present invention is shown.

[0072] In steps 301 and 302, as regarding Figure 2 As described, the first image B1 and the second image B2 are generated. Figure 3 In the implementation of the method, in step 303, the first image B1 is segmented to obtain the segmented first image B1”, and in step 304, the second image B2 is segmented to obtain the segmented second image B2”.

[0073] In the segmented first image B1" different image regions, also referred to as segments, have been identified, which also include a region corresponding to a residue 8 of contrast agent. In the segmented second image B2" corresponding regions or segments have also been identified analogously. The segmented second image B2" can thereby for example contain a region corresponding to a residue 10 of contrast agent, a region corresponding to a tube structure 11, in particular further contrast agent, etc. The first and second segmented images B1", B2" can for example both include regions or segments corresponding to static structures, for example bone structures. The respective positions of these static structures can be checked by the computing unit 3 in step 305 to produce a transformation 7 for image registration.

[0074] Furthermore, the computing unit 3 produces a further first image B1' on the basis of the segmented first image B1" in step 306. To this end, the computing unit 3 can in particular apply a model to the region or segment illustrating the residue 8 of contrast agent.

[0075] The computing unit 3 produces a further second image B2' on the basis of the further first image B1' and the segmented second image B2" in step 307, for example by subtraction as described above with respect to step 306, in which the residue 10 of contrast agent is partially or completely removed or compensated. Figure 2

[0076] As described in particular according to the figures, the application achieves a reduction in the influence of undesired residues of contrast agent in the imaging method.

[0077] In some embodiments, the application can also be used to extract the distribution of contrast-enhanced material, which can also be referred to as contrast agent, for example injected X-ray non-transparent embolization spheres, for example from X-ray recordings with separate radiation energy or from spectral computed tomography recordings or from cone beam computed tomography recordings.​

Claims

1. An X-ray-based imaging method, wherein, Using an imaging device (1), a first image (B1) representing the object to be imaged is generated at a first recording time, and a second image (B2) representing the object to be imaged is generated at a second recording time after the first recording time. Its features are, - Based on the first image (B1), another first image (B1') is generated using a preset model, wherein the preset model is related to the evolution of the characteristics of the contrast agent present in the object to be imaged at the time of generating the first image (B1) over time, so that the other first image takes into account the evolution of the contrast agent present in the object to be imaged at the time of generating the first image from the first recording time to the second recording time, wherein the model reflects the functional relationship between the characteristics of the contrast agent and time; - A second image (B2') is generated based on the second image (B2) and the additional first image (B1'), in which the effect of the contrast agent present in the object to be imaged when the first image (B1) was generated on the second image (B2) is at least partially compensated. The characteristics of the contrast agent present in the object to be imaged when the first image (B1) is generated are preset into the model as input information, and the evolution of the characteristics of the contrast agent over time is predicted or estimated by at least one computing unit when using the model.

2. The imaging method according to claim 1, wherein, The model involves the spatial distribution and / or concentration of contrast agents as a function of time.

3. The imaging method according to any one of the preceding claims, wherein, - A difference image is generated by subtracting the additional first image (B1') from the second image (B2) or by subtracting the second image (B2) from the additional first image (B1'); and - The additional second image (B2') is generated based on or corresponds to the difference image.

4. The imaging method according to claim 3, wherein, The imaging method is designed for subtraction angiography, wherein the additional first image (B1') corresponds to a mask image of subtraction angiography and the second image (B2) corresponds to a vascular image of subtraction angiography.

5. The imaging method according to claim 1 or 2, wherein, The first image (B1) is segmented and the additional first image (B1') and / or the additional second image (B2') are generated based on the segmented first image (B1").

6. The imaging method according to claim 5, wherein, The generation of the additional first image (B1') involves changing the first region representing the contrast agent in the segmented first image (B1') according to the model of the evolution of the contrast agent over time from the first recording time to the second recording time.

7. The imaging method according to claim 6, wherein, - The second image (B2) is segmented, and a second region is determined in the segmented second image (B2"), the second region corresponding to the changed first region of the segmented first image (B1"); and - Remove or partially remove the second region from the segmented second image (B2") to generate the additional second image (B2').

8. The imaging method according to claim 5, wherein, - Determine another first region of the segmented first image (B1), the other first region corresponding to a fixed anatomical structure; - Segment the second image (B2) and determine another second region of the segmented second image (B2"), the other second region corresponding to the fixed anatomical structure; - Determine the transformation (7) for image registration based on the additional first region and the additional second region; and - The additional second image (B2') is generated according to the transformation (7).

9. The imaging method according to claim 1 or 2, wherein, The imaging method is designed for use in angiography.

10. An imaging apparatus (1) having an X-ray-based imaging module (3) configured to generate a first image (B1) representing an object to be imaged at a first recording time and to generate a second image (B2) representing the object to be imaged at a second recording time after the first recording time. Its features are, The imaging device (1) has at least one computing unit (6), the computing unit being configured for... - Based on the first image (B1), another first image (B1') is generated using a preset model, wherein the preset model is related to the evolution of the characteristics of the contrast agent present in the object to be imaged at the time of generating the first image (B1) over time, so that the other first image takes into account the evolution of the contrast agent present in the object to be imaged at the time of generating the first image from the first recording time to the second recording time, wherein the model reflects the functional relationship between the characteristics of the contrast agent and time; - A second image (B2') is generated based on the second image (B2) and the additional first image (B1'), in which the effect of the contrast agent present in the object to be imaged when the first image (B1) was generated on the second image (B2) is at least partially compensated. The characteristics of the contrast agent present in the object to be imaged when the first image (B1) is generated are preset as input information to the model, and the computing unit predicts or estimates the evolution of the characteristics of the contrast agent over time when using the model.

11. A computer program product having instructions that, when executed by an imaging apparatus (1) according to claim 10, cause the imaging apparatus (1) to perform an imaging method according to any one of claims 1 to 9.

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