Methods for creating a vascular image and methods for fluoroscopy of vessels, as well as a correspondingly designed imaging system

Abstract

Method for creating a vascular image within a volume section of an object under investigation using an imaging system (10), wherein the method comprises the following steps: Acquisition (S1, S2) of imaging data of the volume segment within a predetermined time interval, and Determining (S5) a contrast agent arrival time per pixel of a vascular image generated from the imaging data, Determining (S11) a maximum opacity within the time interval due to a contrast agent administered to the subject per pixel of the vascular image, and Segmentation (S6) of vessels by deciding, based on the maximum opacity of the pixel and the contrast agent arrival time of the pixel, whether the respective pixel belongs to a vessel, characterized by that the respective pixel belongs to a vessel if a corrected opacity of the pixel is greater than a predetermined opacity threshold, and that the corrected opacity of the pixel is greater the greater the maximum opacity of the pixel and the greater the contrast agent arrival time of the pixel, or characterized by that the respective pixel belongs to a vessel if a corrected opacity of the pixel is greater than a predetermined opacity threshold, and that the corrected opacity depends on a product of the maximum opacity of the pixel and a function value that depends on the contrast agent arrival time of the pixel, where the function for calculating the function value increases monotonically with the contrast agent arrival time.

Description

[0001] The present invention relates to methods for creating vascular images and to a method for fluoroscopic imaging or fluoroscopic overlay of vessels as well as correspondingly designed imaging systems.

[0002] WO 2014 / 162273 A1 describes a method for vascular segmentation using an X-ray system. Several two-dimensional angiographic images of a vascular structure are acquired within a time period following a contrast agent injection. Segmentation is performed based on a connectivity index of the pixels of the angiographic images, with the connectivity index being calculated based on a combination of a vessel confidence index and an arrival time index of the pixels, which relates to the injected contrast agent.

[0003] DE 10 2007 024 450 A1 describes the creation of an evaluation image using an X-ray system. A temporal sequence of X-ray images is created. A characteristic value is calculated for each pixel of the evaluation image that corresponds to a blood vessel. Based on the temporal progression of the characteristic values, a time point characteristic of the arrival time at the respective pixel is determined, on which the color property of the pixel depends.

[0004] During vascular interventions (e.g., stent placement), the current fluoroscopy image is overlaid with an overlay vascular image to assist with catheter navigation, for example. This procedure is also known as "roadmapping." The overlay vascular image is based on two-dimensional or three-dimensional vascular images.

[0005] However, state-of-the-art roadmapping methods do not differentiate between different vessel types, so the overlay vessel image encompasses all vessel types and sizes. However, for a specific vascular procedure, only specific vessels are usually required, and too much information can actually interfere with the physician's work.

[0006] In addition, when visualizing vessels using contrast agents, there is the problem that arterial vessels are displayed comparatively more strongly or larger than venous vessels, which is also a problem for the creation of overlay vascular images.

[0007] Therefore, the present invention aims to at least mitigate these problems known from the prior art, in particular by compensating for dilution effects of the contrast agent.

[0008] According to the invention, this object is achieved by a method for creating a vascular image according to claim 1, by a method for creating a selective vascular image according to claims 8 and 9, by a method for fluoroscopic imaging of vessels according to claim 11, by an imaging system according to claim 12 or 13, by a computer program product according to claim 15, and by an electronically readable data carrier according to claim 16. The dependent claims define preferred and advantageous embodiments of the present invention.

[0009] Within the scope of the present invention, a method for creating a vascular image within a volume section of an examination subject using an imaging system is provided. The method comprises the following steps: • Acquiring imaging data of the volume section within a predetermined time interval using the imaging system. • Determining a maximum opacity within the time interval, which is achieved by a contrast agent administered to the subject, for each pixel of the vascular image. In other words, the opacity is determined for each pixel in each image created from the imaging data, and then the maximum opacity within the predetermined time interval is determined from the determined opacities per pixel. In the three-dimensional case (e.g., 3D+t modality (so-called 4D digital subtraction angiography or 4D magnetic resonance angiography)), the pixel corresponds to a voxel. • Determining a contrast agent arrival time per pixel of the vascular image. The arrival time of the contrast agent at a pixel can be defined, for example, by the time at which the opacity for this pixel first increases by a predetermined threshold value, starting from an opacity without contrast agent, or reaches its maximum. • Segmentation of vessels by deciding whether the respective pixel belongs to a vessel or not depending on the maximum opacity of the respective pixel and the contrast agent arrival time of the respective pixel.

[0010] By segmenting the vessels not only based on maximum opacity but also depending on the contrast agent arrival time, it is advantageous to counteract the effect that, under otherwise equal conditions, the opacity of a pixel decreases the later the contrast agent reaches the respective pixel. This effect is due to the fact that the contrast agent becomes more diluted and thus has a lower concentration per unit volume the longer the distance from the injection site to the respective pixel.

[0011] The opacity can be determined based on a specific path of a beam (e.g., an X-ray beam) through the volume section using a pixel value. The pixel value corresponds to the value of the pixel on the detector located at the end of the beam path. For example, the opacity A can be determined using the Lambert-Beer law (see equation (1)). I=I0×exp(−A)

[0012] Here, I corresponds to the pixel value and I0 denotes the intensity of the incident beam (i.e., without attenuation). The opacity A can also be interpreted as a line integral of an absorption coefficient or attenuation coefficient along the beam path through the volume section.

[0013] The images used to determine the maximum opacity and contrast agent arrival time per pixel are created, in particular, by digital subtraction angiography. In this process, first images are created of the same volume section without prior contrast agent injection, and second images are created after a prior contrast agent injection. The images created according to the invention correspond, in particular, to a subtraction of corresponding first and second images.

[0014] The segmentation of vessels depending on the maximum opacity and the contrast agent arrival time is performed in particular using a corrected opacity, which is calculated per pixel. The higher the maximum opacity of the pixel and the higher the contrast agent arrival time of the respective pixel, the greater the corrected opacity of the respective pixel. For example, the corrected opacity can be calculated using a product of the maximum opacity of the respective pixel and a function value dependent on the contrast agent arrival time of the respective pixel. The function used to calculate the function value is a function that increases monotonically with the contrast agent arrival time. In other words, the corrected opacity kOp(x,y,z) can be calculated using the following equation (2). kOp(x,y,z) = MaxOp(x,y,z)* f(KAZ(x,y,z))

[0015] Here, MaxOp(x,y,z) corresponds to the maximum opacity of the respective pixel at the location given by the coordinates x,y,z, KAZ(x,y) is the contrast agent arrival time of the respective pixel, and f() is the monotonically increasing function, which depends on the contrast agent arrival time. While the coordinates x, y, and z are required for a three-dimensional vascular image, only the coordinates x and y are needed to create a two-dimensional vascular image, so that the z coordinate would be omitted, for example, in equation (1) above.

[0016] The respective pixel belongs to a vessel of the vessel image to be created in particular if the corrected opacity of the respective pixel is greater than a predetermined opacity threshold.

[0017] By using corrected opacity during segmentation, the previously described dilution effects of the contrast agent can be advantageously compensated.

[0018] According to an embodiment of the invention, even more pixels can be assigned to a vessel which would not belong to any vessel due to the segmentation described above. For this purpose, according to this embodiment, the maximum total opacity is determined for vessel pixels (i.e. pixels which, according to the segmentation, belong to a vessel) of the same vessel which are arranged on the same straight line perpendicular to the flow direction of this vessel. In other words, the maximum of the maximum opacities of these vessel pixels is determined for the vessel pixels lying on this straight line. A pixel which lies on the straight line adjacent to a vessel pixel is also classified as a vessel pixel according to the segmentation if the maximum opacity of this pixel is greater than a product of the previously calculated maximum total opacity and a predetermined percentage.

[0019] This procedure advantageously classifies pixels within the vessel edges of the respective vessel as vessel pixels, especially in the case of large vessels, so that the full extent of the vessel is captured.

[0020] According to a further embodiment of the invention, a segmented (smaller) vessel whose two vessel edges are also vessel edges of two different segmented vessels (in particular larger vessels) is eliminated from the vessel image to be created, so that the vessel pixels belonging to the (smaller) vessel are classified as no longer belonging to a vessel (i.e., no longer as vessel pixels). For example, a vessel can be classified as a smaller vessel if the distance between its two essentially parallel edges is below a predetermined distance threshold.

[0021] With this further embodiment, incorrect segmentation in image areas with several (larger) vessels can be subsequently corrected.

[0022] In the present invention, the imaging data is acquired in particular using time-resolved two-dimensional or time-resolved three-dimensional data acquisition. The vascular image can be two-dimensional or three-dimensional. Time-resolved two-dimensional data acquisition is understood in particular to mean 2D+t DSA (digital subtraction angiography), where "2D" stands for two-dimensional and "+t" for time-resolved. Time-resolved data acquisition means that pixel values ​​are available for each image pixel at different times. The temporal resolution depends on the imaging method and the spatial resolution. In addition to two-dimensional methods, three-dimensional methods, known as 3D+t DSA or 4D DSA, can also be used.

[0023] The implementation of so-called 4D DSA using a permanently installed C-arm is described, for example, in Davis, B. et al.: "4D Digital Subtraction Angiography: Implementation and Demonstration of Feasibility," in: American Journal of Neuroradiology AJNR, Vol. 34, 2013, Vol. 10, pages 1914-1921. Currently, approximately 30 images are acquired per second, and, for example, the C-arm completes approximately half a rotation within 5 seconds. However, other acquisition protocols using a C-arm are also possible, such as scanning a larger angular interval.

[0024] As can be seen in "Clinical Application of 3D / 4D MR Angiography in Cardiovascular Diseases," J. Barkhausen et al., MAGNETOM Flash 2 / 2007, a temporal resolution of 1 to 5 seconds can be achieved with a magnetic resonance system, for example, when using the TWIST ("Time-resolved With Stoachastic Trajectories") sequence, depending on the sequence parameters and spatial resolution. When using parallel measurement techniques, even a temporal resolution of less than 1 second is conceivable.

[0025] Other sequences that enable high temporal resolution in MR measurements are kt SENSE, UNFOLD-SENSE, Noquist, kt GRAPPA, 3D-TRICKS, TREAT, as described in Kiefer, C. et al.: “Theoretical and clinical aspects of TWIST based 4D time-resolved MR angiography”, In: International Federation for Medical & Biological Engineering IFMBE Proceedings, Vol. 25 / II, 2009, pages 466-469. - ISSN 9783642038785.

[0026] The imaging system may include an X-ray system, a magnetic resonance imaging system or a computer tomography system, although combinations of several of these devices are also conceivable.

[0027] While creating a normal two-dimensional X-ray image does not require reconstruction, image reconstruction from the imaging data is necessary if volumetric data (e.g., three-dimensional images) is to be generated. The imaging data for generating volumetric data can be acquired using a magnetic resonance imaging system, a computed tomography scanner, or an X-ray C-arm system.

[0028] The segmentation of the vessels can also be carried out depending on morphological information of the object under investigation, for example depending on prior knowledge about the structure of the vascular tree of the object under investigation.

[0029] The present invention also provides a method for creating a selective vascular image within a volume section of an examination subject using an imaging system. The method comprises the following steps: • Creating a vascular image of the volume section. Creating the vascular image includes the following substeps: ○ Acquiring imaging data of the volume section within a predetermined time interval using the imaging system. ○ Determining a maximum opacity within the time interval due to a contrast agent administered to the subject per pixel of the vascular image. ○ Segmentation of vessels by deciding whether the respective pixel belongs to a vessel or not depending on the maximum opacity of the respective pixel. • Determine a contrast agent arrival time per pixel of the vascular image. • Segmentation to determine whether the respective vessel in the vascular image also belongs to a vessel in the selective vascular image. For this purpose, a perfused area of ​​the respective vessel perpendicular to the flow direction within the respective vessel is estimated. If this perfused area is smaller than a predetermined maximum size threshold and larger than a predetermined minimum size threshold, and if, at the same time, the (mean) contrast agent arrival time of the pixels in the vessel is smaller than a predetermined maximum contrast agent arrival time threshold and larger than a predetermined minimum contrast agent arrival time threshold, then the respective vessel belongs to the vessels in the selective vascular image.

[0030] The inventive method for creating a selective vascular image therefore creates the selective vascular image based on the opacity caused by a contrast agent, on the one hand, and on the arrival time at which the contrast agent arrives in the respective vessel, on the other. For example, a physician can specify a window for the vessel size (defined by the minimum and maximum size threshold) and a window for the contrast agent arrival time (defined by the minimum and maximum contrast agent arrival time threshold). From the (preliminary) vascular image created purely from the maximum opacity, only those vessels that lie within the two defined windows are incorporated into the selective vascular image.

[0031] The selective vascular image according to the invention thus advantageously contains only the desired vascular information.

[0032] According to a preferred embodiment of the invention, the previously described method according to the invention for creating a vascular image is used to create the preliminary vascular image.

[0033] In this embodiment, the contrast agent arrival time is therefore also used to create the preliminary vascular image in order to correct (more precisely, to increase) the opacity of those pixels for which the contrast agent arrival time is comparatively longer.

[0034] In the two-dimensional case, the flow area of ​​the respective vessel can be determined based on the length of a line segment perpendicular to the flow direction of the respective vessel, the ends of which correspond to the opposite edges of the vessel. To do this, the flow direction of the respective vessel should lie essentially within the plane of the two-dimensional vessel image, which also contains the line segment to be measured to determine the flow area.

[0035] Within the scope of the present invention, a method for fluoroscopic imaging of vessels within a volume section of an examination subject using an imaging system is also provided, for example, for performing an intervention in a vascular system of the examination subject. A current image (a so-called live image) of the volume section is superimposed on a selective vascular image created according to the invention. This selective vascular image is created using one of the previously described inventive methods for creating a selective vascular image.

[0036] Due to the inventive creation of the selective vascular image, which is superimposed on the current image so that only those vessels are visible in the current image that correspond to the vessels in the selective vascular image, the physician viewing the current image is advantageously not distracted by irrelevant vascular information. In other words, by selecting the appropriate threshold values, the physician has the option of specifically or selectively specifying which vascular information they wish to see in the current image or live image. For example, it is possible for only those vessels to be visible in the live image whose contrast agent arrival time lies within a certain time period and whose thickness or dimensions also lie within a certain range defined by the corresponding threshold values.

[0037] Within the scope of the present invention, an imaging system is also provided which is designed to create a vascular image within a volume section of an examination object. The imaging system is also designed to acquire imaging data of the volume section within a predetermined time interval, to determine from images created from the imaging data a maximum opacity within the predetermined time interval depending on a contrast agent injected into the examination object per pixel of the vascular image, to determine the contrast agent arrival time per pixel of the vascular image, and to segment vessels of the vascular image by deciding whether the respective pixel belongs to a vessel of the vascular image or not depending on the maximum opacity of the pixel and the contrast agent arrival time of the pixel.

[0038] The advantages of the imaging system according to the invention essentially correspond to the advantages of the method according to the invention for creating a vascular image, which have been explained in detail above, so that a repetition is omitted here.

[0039] Within the scope of the present invention, a further imaging system is also provided, which is designed to create a selective vascular image within a volume section of an examination subject. The further imaging system is also designed to create a vascular image of the volume section by the imaging system ◯ imaging data of the volume section is acquired within a predetermined time interval, ◯ a maximum opacity within the time interval is determined depending on a contrast agent injected into the object under examination per pixel of the vascular image, and ◯ Vessels are segmented by the imaging system deciding, depending on the maximum opacity of the pixel, whether the respective pixel belongs to a vessel in the vascular image or not.

[0040] In addition, the imaging system is designed to determine a contrast agent arrival time per pixel of the vascular image, and to segment whether the respective vessel of the vessel image also belongs to a vessel of the selective vessel image by only deciding that the vessel also belongs to a vessel of the selective vessel image if a flow-through area of ​​the vessel perpendicular to the flow direction within the vessel is smaller than a predetermined maximum size threshold and larger than a predetermined minimum size threshold and if, at the same time, the (mean) contrast agent arrival time of the pixels of the vessel is smaller than a predetermined maximum contrast agent arrival time threshold and larger than a predetermined minimum contrast agent arrival time threshold.

[0041] In this case too, the advantages of the further imaging system according to the invention essentially correspond to the advantages of the method according to the invention for creating a selective vascular image, which have been explained in detail above, so that a repetition is omitted here.

[0042] Furthermore, the present invention describes a computer program product, in particular a computer program or software that can be loaded into a memory of a programmable controller or a computing unit of an imaging system. With this computer program product, all or various of the previously described embodiments of the methods according to the invention can be carried out when the computer program product is running in the controller or control device of the imaging system. In this case, the computer program product may require program means, e.g. libraries and auxiliary functions, in order to implement the corresponding embodiments of the methods. In other words, the claim directed to the computer program product is intended to protect, in particular, a computer program or software with which one of the above-described embodiments of the method according to the invention can be carried out.which executes this embodiment. The software can be source code (e.g., C++) that still needs to be compiled (translated) and linked, or that only needs to be interpreted, or it can be executable software code that only needs to be loaded into the corresponding processing unit or control device for execution.

[0043] Finally, the present invention discloses an electronically readable data storage medium, e.g., a DVD, a magnetic tape, or a USB stick, on which electronically readable control information, in particular software (see above), is stored. If this control information (software) is read from the data storage medium and stored in a control device or processing unit of an imaging system, all embodiments of the method described above can be implemented.

[0044] The present invention can be implemented with an X-ray system having a mobile C-arm, as well as with an X-ray system having a stationary C-arm. Furthermore, the present invention can be used for both two-dimensional and three-dimensional visualization.

[0045] While the prior art does not consider the arrival time of the contrast agent or contrast agent bolus when creating an overlay vascular image, the present invention uses this arrival time both to correct opacity and to select between different vessels to be displayed. While prior art roadmapping solutions do not distinguish between different vessel types or sizes, thus displaying all vessels, the present invention only depicts the vessels deemed important by the respective physician, thus advantageously avoiding the display of interfering information.

[0046] In the following, the present invention is described in detail using preferred embodiments of the invention with reference to the figures. Fig. 1 shows an imaging system according to the invention, in this case an X-ray system with a mobile C-arm. In Fig. 2 shows an inventive procedure for creating an overlay image. In Fig. 3 is an excerpt from Fig. 2 shown in detail. In Fig. Figure 4 shows a flow chart for creating a selective vascular image.

[0047] In Fig. 1 shows a mobile X-ray system 10 according to the invention, which comprises a control device 6, a C-arm 1, and a screen 4. The C-arm 1, in turn, comprises an X-ray source 2 and a detector 3. To acquire imaging data of an examination subject, the C-arm 1 generally remains stationary relative to the examination subject when generating two-dimensional information, while it rotates around the examination subject when generating three-dimensional information.

[0048] In Fig. 1 also shows a data carrier 5 according to the invention, which has stored a computer program product (ie software) according to the invention.

[0049] In Fig. Figure 2 shows an inventive procedure for creating a selective vascular image. At the beginning of this procedure, DSA images are available, which are created according to the invention. In step S12, the maximum opacity in these DSA images is determined. In parallel, the contrast agent arrival time is determined in step S5. Based on the maximum opacity and the contrast agent arrival time, the extent of the vessels present in the DSA images is determined in step S8.

[0050] In the form of an interactive selection, an operator (for example the attending physician) can set a marker 7. This marker defines a range of diameter size and a range of contrast agent arrival time. Based on this specification or definition, a selective vessel image or overlay image is created in step S11 depending on the contrast agent arrival time determined in step S5 and the size of the respective vessels determined in step S8. This selective vessel image only contains those vessels whose size or diameter lies within the specified diameter size range and whose contrast agent arrival time lies within the specified contrast agent arrival time range. Finally, in step S13, the previously created selective image is displayed as an overlay image together with a fluoroscopic live image.

[0051] In Fig. 3 is the Fig. 2, the area 8 shown is enlarged and annotated. It can be seen that area 8, which represents a square, is itself divided into four equal-sized squares or quadrants. If area 8 is divided into two halves: an area with early and a later contrast agent arrival time, and the other half into a region of large and small diameter vessels, then setting marker 7 means • in the upper left quadrant, so that only large arteries are shown in the selective vascular image, • in the upper right quadrant, so that only large veins are shown in the selective vascular image, • in the lower left quadrant, that only small arteries are shown in the selective vascular image, and • in the lower right quadrant, so that only small veins are shown in the selective vascular image.

[0052] Of course, it is also possible to set marker 7 so that it lies in two or more quadrants. Setting multiple markers is also conceivable, so that, for example, both large arteries and large veins are displayed in the overlay vascular image and thus on the masked live vascular image.

[0053] In Fig. Figure 4 shows a flow chart for creating a selective vascular image according to the invention.

[0054] In step S1, image data from a predetermined volume section of an examination object are acquired using an imaging system (for example, a magnetic resonance system or an X-ray system) without a contrast agent being injected into the examination object beforehand. In step S2, a contrast agent is injected into the examination object, and then, in step S3, time-resolved image data from the predetermined volume section are acquired again using the imaging system. While in step S1 it is sufficient to acquire image data in order to create or reconstruct a two-dimensional image or a three-dimensional image, in step S3 image data are acquired over a longer period of time (while the contrast agent spreads through the examination object) in order to be able to trace the spread of the contrast agent in the images, particularly based on the opacity.

[0055] In step S4, DSA images are reconstructed or created from the image data acquired in steps S1 and S3 by subtracting image information with contrast agent from image information without contrast agent for each time step. Based on these DSA images, the contrast agent arrival time per pixel is determined in step S5, and the maximum opacity of each pixel is determined in step S6.

[0056] Depending on the maximum opacity, which is corrected based on the contrast agent arrival time, vessels are segmented in step S7. For this purpose, a decision is made for each pixel based on the corrected maximum opacity of each pixel as to whether this pixel is a vessel pixel or not. The segmented vessels are then formed from vessel pixels.

[0057] In step S8, the size of the vessels segmented in step S7 is determined.

[0058] In step S9, a target size range and a target arrival time range are specified. The target size range is defined by a lower size threshold and an upper size threshold, and the target arrival time range is defined by a lower contrast agent arrival time threshold and an upper contrast agent arrival time threshold.

[0059] In step S10, those vessels are identified whose size lies within the target size range and whose contrast agent arrival time lies within the arrival time range. Only the vessels identified in step S10 constitute the vessels present in the selective vessel image. Finally, in step S11, the selective vessel image is displayed as an overlay vessel image.

Claims

[1] Method for creating a vascular image within a volume section of an examination object by means of an imaging system (10), the method comprising the following steps: Acquiring (S1, S2) imaging data of the volume section within a predetermined time interval, and Determining (S5) a contrast agent arrival time per pixel of a vascular image created from the imaging data, Determining (S11) a maximum opacity within the time interval due to a contrast agent administered to the examination object per pixel of the vascular image, and Segmentation (S6) of vessels by deciding whether the respective pixel belongs to a vessel depending on the maximum opacity of the pixel and the contrast agent arrival time of the pixel, characterized by , that the respective pixel belongs to a vessel if a corrected opacity of the pixel is greater than a predetermined opacity threshold, and that the corrected opacity of the pixel is greater, the greater the maximum opacity of the pixel and the greater the contrast agent arrival time of the pixel, or characterized by , that the respective pixel belongs to a vessel if a corrected opacity of the pixel is greater than a predetermined opacity threshold, and that the corrected opacity depends on a product of the maximum opacity of the pixel and a function value depending on the contrast agent arrival time of the pixel, where the function for calculating the function value increases monotonically with the contrast agent arrival time. [2] Method according to claim 1, characterized by , that the maximum total opacity is determined for vessel pixels of a vessel which are arranged on the same straight line perpendicular to the flow direction of the vessel, wherein a vessel pixel defines a pixel which belongs to a segmented vessel, and that a pixel lying on the straight line adjacent to a vessel pixel is also segmented as a vessel pixel if its maximum opacity is greater than a product of the maximum total opacity and a given percentage. [3] Method according to one of the preceding claims, characterized by that a segmented smaller vessel, both edges of which are also edges of two different segmented larger vessels, is eliminated from the vessel image to be created, so that the pixels of the smaller vessel no longer belong to one vessel. [4] Method according to one of the preceding claims, characterized by , that the imaging data are acquired by means of time-resolved two-dimensional or time-resolved three-dimensional data acquisition, and / or that the vascular image is two-dimensional or three-dimensional. [5] Method according to one of the preceding claims, characterized by that the method comprises reconstructing (S4) images (11) depending on the acquired imaging data. [6] Method according to one of the preceding claims, characterized by that the imaging system comprises an X-ray system (10) and / or a magnetic resonance system and / or a computer tomograph. [7] Method according to one of the preceding claims, characterized by that segmentation is carried out depending on morphological information of the object under investigation. [8] Method for creating a selective vascular image within a volume section of an examination object by means of an imaging system (10), wherein in the selective vessel image a vessel of the volume section is selectively displayed or suppressed depending on at least one predetermined criterion, the method comprising the following steps: Creating a vessel image of the volume section with the following substeps: • Acquiring imaging data of the volume section within a predetermined time interval by means of the imaging system (10), • Determining a maximum opacity within the time interval due to a contrast agent administered to the examination subject per pixel of a vascular image created from the imaging data, and • Segmentation of vessels by deciding whether the respective pixel belongs to a vessel depending on the maximum opacity of the pixel, Determining a contrast agent arrival time per pixel of the vascular image, and Segmenting whether the respective vessel of the vessel image belongs to a vessel of the selective vessel image if a flow-through area of ​​the vessel perpendicular to the flow direction is smaller than a predetermined maximum size threshold and larger than a predetermined minimum size threshold and if the contrast agent arrival time of the pixels of the vessel is less than a predefined maximum contrast agent arrival time threshold and greater than a predefined minimum contrast agent arrival time threshold. [9] Method for creating a selective vascular image within a volume section of an examination object by means of an imaging system (10), wherein in the selective vessel image a vessel of the volume section is selectively displayed or suppressed depending on at least one predetermined criterion, the method comprising the following steps: Creating a vessel image of the volume section using a method according to any one of claims 2-7, and Segmenting whether the respective vessel of the vessel image belongs to a vessel of the selective vessel image if a flow-through area of ​​the vessel perpendicular to the flow direction is smaller than a predetermined maximum size threshold and larger than a predetermined minimum size threshold and if the contrast agent arrival time of the pixels of the vessel is less than a predefined maximum contrast agent arrival time threshold and greater than a predefined minimum contrast agent arrival time threshold. [10] Method according to claim 8 or 9, characterized by , that the vascular image is two-dimensional, that the flow direction of the respective vessel lies within the plane of the vessel image, and that the area through which the fluid flows is determined by a length of a section which is perpendicular to a flow direction of the respective vessel and is limited by the opposite edges of the vessel. [11] Method for the fluoroscopic representation of vessels within a volume section of an examination object by means of an imaging system (10), wherein a current image of the volume section is superimposed by a selective vessel image which is created using the method according to one of claims 8 or 9. [12] Imaging system designed to create a vascular image within a volume section of an object under examination, wherein the imaging system (10) is further configured to acquire imaging data of the volume section within a predetermined time interval, and to determine a contrast agent arrival time per pixel of the vascular image created from the imaging data, wherein the imaging system (10) is further configured to determine a maximum opacity within the predetermined time interval based on a contrast agent administered to the examination subject per pixel of the vessel image, and to segment vessels by the imaging system (10) deciding whether the respective pixel belongs to a vessel depending on the maximum opacity of the pixel and the contrast agent arrival time of the pixel, characterized by , that the imaging system is designed to carry out the method according to one of claims 1-7 or 9. [13] Imaging system which is designed to create a selective vascular image within a volume section of an examination object, in which the imaging system (10) selectively displays or suppresses a vessel of the volume section in the selective vascular image depending on at least one predetermined criterion, wherein the imaging system (10) is further configured to create a vascular image of the volume section by the imaging system (10) acquiring imaging data of the volume section within a predetermined time interval, determining a maximum opacity within the time interval based on a contrast agent administered to the examination subject per pixel of the vascular image, and segmenting vessels by the imaging system (10) deciding, depending on the maximum opacity of the pixel, whether the respective pixel belongs to a vessel, wherein the imaging system (10) is further configured to determine a contrast agent arrival time per pixel of the vessel image and to segment whether the respective vessel of the vessel image belongs to a vessel of the selective vessel image if a perfused area of ​​the vessel perpendicular to the flow direction is smaller than a predetermined maximum size threshold and greater than a predetermined minimum size threshold and if the contrast agent arrival time of the pixels of the vessel is smaller than a predetermined maximum contrast agent arrival time threshold and greater than a predetermined minimum contrast agent arrival time threshold. [14] Imaging system according to claim 13, characterized by that the imaging system is designed to carry out the method according to claim 8 or 9. [15] Computer program product with program code which can be loaded directly into a memory of a programmable control device (6) of an imaging system (10), which is designed to carry out all steps of the method according to one of claims 1-9 when the program code is executed in the control device (6) of the imaging system (10). [16] Electronically readable data carrier on which the program code of a computer program executable by a control device (6) of an imaging system (10) is stored, with program code for carrying out all method steps according to one of claims 1-9 when the program code is executed in the control device (6) of the imaging system (10).

Images