X-ray imaging method, X-ray imaging system and computer program product

Abstract

In an X-ray imaging method, a first time duration (T1) and a second time duration (T2) are determined, the first time duration being a flow duration of a contrast agent from a predetermined contrast agent injection location to a predetermined location (8) of a hollow organ (7) close to the body median, the second duration is a duration of flow of the contrast agent from a position (8) of the hollow organ (7) close to the body median to a predetermined position (9) away from the body median. In a first recording phase (A1), a first sequence of X-ray projection images is generated, each projection image of the first sequence at least partially displaying the hollow organ (7) according to a different projection direction specified in each case. The first imaging phase (A1) is started after a first time length (T1) has elapsed after an injection start time at which the contrast agent is injected at the contrast agent injection position, and the duration of the first imaging phase (A1) is equal to a second time length (T2). A time-resolved three-dimensional reconstruction of the hollow organ (7) is generated from the first sequence of projection images.

Description

Technical Field

[0001] The present invention relates to an X-ray imaging method for time-resolved three-dimensional display of at least one hollow organ of a person and an X-ray imaging system for time-resolved three-dimensional display of at least one hollow organ of a person, wherein the X-ray imaging system has an X-ray light source, an X-ray detector, a drive device and at least one computing unit, wherein the drive device is used to position the X-ray light source and the X-ray detector relative to a recording area according to different projection directions. In addition, the present invention also relates to a corresponding computer program product. Background Art

[0002] In order to generate a three-dimensional reconstruction of the organ to be imaged by means of X-ray imaging, for example, a large number of X-ray projection images are recorded in different projection directions, and a three-dimensional reconstruction is obtained by re-projecting the corresponding projection images. In this way, for example, a three-dimensional reconstruction of a hollow organ, such as a vascular system in particular, can also be generated. In this case, this is referred to as three-dimensional angiography.

[0003] It is also possible to generate an X-ray projection image before contrast medium administration on the one hand and generate another X-ray projection image after or during contrast medium administration on the other hand, and to subtract the X-ray projection images imaged with or without contrast medium in the same projection direction, so that hollow organs and, if necessary, tools can be better identified in the generated subtraction image. The subtraction image can also be based on a three-dimensional reconstruction. In this case, it is 3D-DSA (three-dimensional digital subtraction angiography). Methods are also provided in which the subtraction is performed in the three-dimensional image from the beginning.

[0004] If multiple projection images are taken during the diffusion of the contrast agent in the hollow organ, multiple time-resolved three-dimensional reconstructions can be generated, which enables observation of the contrast agent bolus at multiple different times and different viewing angles. If this is combined with subtraction technology, it is called 4D-DSA. In the article "4D-DSA: Current Status of Development and Application of Neurovascular" published by KLRuedinger et al. in the American Journal of Neuroradiology, issue 42(2)214-220, 2021, the authors introduce the development, acquisition, reconstruction and current applications of 4D-DSA.

[0005] In order to generate a time-resolved 3D reconstruction (also called 4D reconstruction or time-resolved three-dimensional imaging or 4D image) of one or more hollow organs of a person by means of the method, a conventional 3D reconstruction is usually first generated from the 2D reconstruction images generated during the administration of the contrast agent. For this purpose, for example, projection images of the hollow organ completely filled with contrast agent are required in a sufficient number of projection directions. The 2D reconstruction images provide the contrast agent flow in the at least one hollow organ in the form of a cross section of the hollow organ partially filled with contrast agent, and the 2D reconstruction images are integrated into the previously generated 3D reconstruction by reprojection.

[0006] The prerequisites for this are, on the one hand, the presence of a sufficiently large number of two-dimensional projection images for producing a three-dimensional reconstruction with the hollow organ completely filled with contrast agent, and, on the other hand, the time-resolved administration of the contrast agent bolus in the entire region of interest. If this is not the case, artifacts or holes may result in the time-resolved images, wherein, for example, the propagation of the contrast agent bolus cannot be imaged in certain critical regions of the hollow organ. Summary of the invention

[0007] The object of the present invention is to at least partially overcome the disadvantages in X-ray imaging for the time-resolved three-dimensional display of at least one hollow organ of a person.

[0008] This object is achieved according to the invention by an X-ray imaging method for the time-resolved three-dimensional display of at least one hollow organ of a person, wherein:

[0009] - determining a first duration, which is a flow duration of contrast agent from a predetermined contrast agent injection site of a person to a predetermined location of at least one hollow organ near the midline of the body, which varies from person to person;

[0010] - determining a second duration, the second duration being a duration of flow of the contrast agent from a position of the at least one hollow organ close to the midline of the body to a predetermined position away from the midline of the body, which varies from person to person;

[0011] - generating a first sequence of projection images in a first recording phase, wherein each projection image of the first sequence at least partially shows the at least one hollow organ according to a respectively predefined different projection direction;

[0012] - the first recording phase starts after the first time period has passed since the injection start time of the contrast medium at the contrast medium injection site, and the duration of the first recording phase is equal to the second time period; and

[0013] - generating a time-resolved three-dimensional reconstruction of said at least one hollow organ from said first sequence of projection images.

[0014] The technical problem is also solved according to the present invention by an X-ray imaging system, which is used for time-resolved three-dimensional display of at least one hollow organ of a person, and which has an X-ray light source, an X-ray detector, a drive device and at least one computing unit, wherein the drive device is used to position the X-ray light source and the X-ray detector relative to a shooting area according to different projection directions, and the computing unit is configured to

[0015] - determining a first duration, which is a flow duration of contrast agent from a predetermined contrast agent injection site of a person to a predetermined location of at least one hollow organ near the midline of the body, which varies from person to person;

[0016] - determining a second duration, the second duration being a duration of flow of the contrast agent from a position of the at least one hollow organ close to the midline of the body to a predetermined position away from the midline of the body, which varies from person to person;

[0017] - controlling the drive device, the X-ray source and the X-ray detector so as to generate a first sequence of projection images in a first imaging phase, wherein each projection image of the first sequence at least partially displays the at least one hollow organ according to a respectively preset different projection direction, wherein the first imaging phase starts after the first time period has elapsed after the injection start time of the contrast agent at the contrast agent injection position, and the duration of the first imaging phase is equal to the second time period; and

[0018] - generating a time-resolved three-dimensional reconstruction of said at least one hollow organ from said first sequence of projection images.

[0019] According to the invention, this object is also achieved by a computer program product having instructions which, when run by an x-ray imaging system of the type mentioned above, carry out an x-ray imaging method of the type mentioned above.

[0020] The idea on which the present invention is based is that a shooting phase for generating a series of projection images is delayed for a first time period after the start time of injection of a contrast agent, wherein the series of projection images at least partially images at least one hollow organ from different projection directions, wherein the first time period is a contrast agent flow time period from a preset contrast agent injection position to a preset position of at least one hollow organ close to the midline of the body (or the inner side), which varies from person to person, wherein the duration of the shooting phase is equal to a second time period, wherein the second time period is a contrast agent flow time period from a preset position close to the midline of the body to a preset position of at least one hollow organ away from the midline of the body (or the outer side), which varies from person to person.

[0021] According to one aspect of the present invention, an X-ray imaging method for time-resolved three-dimensional display of at least one hollow organ of a person is provided. A first duration is obtained, in particular by at least one computing unit of an X-ray imaging system, wherein the first duration is a contrast agent flow duration that varies from person to person, in particular, a contrast agent flow duration that varies from a preset contrast agent injection position to a preset position of at least one hollow organ close to the body midline. A second duration is obtained, in particular by at least one computing unit, wherein the second duration is a contrast agent flow duration that varies from a position of at least one hollow organ close to the body midline to a position away from the body midline.

[0022] In a first recording phase, a first sequence of X-ray projection images is generated, wherein each projection image of the first sequence at least partially displays the hollow organ according to a respectively preset different projection direction. The first recording phase starts after a first time period has passed after an injection start time for injecting a contrast agent at a contrast agent injection site, i.e., the first recording phase starts when the first time period has passed after the injection start time, and the duration of the first recording phase is equal to the second time period, i.e., the first recording phase ends after the injection start time has passed after the sum of the first time period and the second time period. A time-resolved three-dimensional reconstruction of at least one hollow organ is generated based on the projection images of the first sequence, in particular by means of at least one computing unit.

[0023] The first duration and the second duration can be obtained in particular by storing the first duration and the second duration in a storage medium of the at least one computing unit and reading them out by the at least one computing unit. The at least one computing unit also obtains in particular the injection start time, i.e. the time at which the injection of the contrast agent at the contrast agent injection site begins. For this purpose, an information signal is generated at the start of the injection, for example by means of a user input or automatically, and is transmitted to the at least one computing unit. However, the injection of the contrast agent itself is not part of the X-ray imaging method.

[0024] The first and second durations are in particular precisely the durations that are specific to a person at least one hollow organ is displayed by the X-ray imaging method. According to the invention, the first and second durations can be determined before the X-ray imaging method or in some embodiments also before the recording phase as part of the X-ray imaging method.

[0025] “The first shooting phase starts after the first time period has passed after the injection start time”, which can be understood in particular as that the shooting of the initial projection image of the first sequence starts after the first time period has passed after the injection start time. “The duration of the first shooting phase is equal to the second shooting duration”, which can be understood in particular as that the last projection image of the first sequence is generated after the second time period has passed after the start of the first shooting phase. In this regard, tolerances in terms of the time range required to generate the projection image, the time range required to set the respective projection directions, the time range required for data detection, etc. are particularly taken into account. The first sequence of projection images is then composed in particular of the initial projection image and the last projection image, as well as a large number of other projection images shot between the initial and last projection images.

[0026] The first sequence is in particular a temporal sequence or a temporally ordered sequence of projection images, wherein the total number of projection images of the first sequence is predefined. The projection images of the first sequence at least partially display at least one hollow organ according to different, respectively predefined projection directions, which can be understood in particular in that the individual projection directions are predefined for all projection images of the first sequence and are respectively different from one another for all projection images of the first sequence. Thus, the projection directions of two different projection images of the first sequence are always different from one another.

[0027] The description of the first sequence can also be transferred analogously to other sequences of projected images.

[0028] The contrast agent injection location is in particular a location in the human vascular system, in particular in the blood vessel system, at which the contrast agent is injected, in particular in a human vein. The contrast agent injection location is not necessarily shown by the projection images of the first sequence and is usually not shown in the first sequence. Therefore, the first duration is usually greater than zero and is in the order of magnitude of a few tenths of a second to a few seconds.

[0029] The first sequence of projection images is used to particularly illustrate a predetermined region of interest, wherein at least one hollow organ is at least partially located in the predetermined region. The contrast agent injection position is not necessarily located in the region of interest, and is typically located outside the region of interest. The position close to the midline of the body may be understood as the portion of the region of interest that the contrast agent bolus first reaches after injection at the contrast agent injection position. That is, in this case, the position close to the midline of the body may be understood as the portion closest to the contrast agent injection position. Correspondingly, the position far from the midline of the body may be a portion inside the region of interest, where the contrast agent bolus last reaches or where the contrast agent bolus leaves the region of interest. That is, in this case, the position far from the midline of the body may be understood as the portion farthest from the contrast agent injection position.

[0030] Generating a time-resolved three-dimensional reconstruction of at least one hollow organ based on a first sequence of projection images can be understood in particular as using at least a first sequence of projection images for generating a time-resolved three-dimensional reconstruction. Usually, for this purpose, for example, further projection images are also used, which are not generated during the recording phase, but after the first recording phase. Since the first recording phase starts at a time T1, wherein the contrast agent injection time is set equal to zero, and T1 represents a first duration, and the first recording duration ends at a time T1+T2, and T2 represents a second duration, the first recording phase covers the entire relevant time range, during which the contrast agent bolus moves from a position close to the body midline to a position away from the body midline.

[0031] In a second recording phase following the first recording phase, while the at least one hollow organ is filled with contrast medium in the entire region of interest, further projection images can be generated, for example, which image the at least one hollow organ. The projection images of the second recording phase are then likewise used to generate a time-resolved three-dimensional reconstruction.

[0032] The projection images of the second acquisition phase can be used, for example, to generate a static 3D reconstruction of the at least one hollow organ, and the projection images of the first sequence from the first acquisition phase can be reprojected into the static 3D reconstruction in order to achieve time resolution.

[0033] As already mentioned, according to the invention, the process of contrast agent injection itself is usually not part of the X-ray imaging method. However, it should be noted that contrast agent injection, for example in known methods for time-resolved three-dimensional imaging, is performed within a time range that allows a sufficient number of projection images to be achieved, in which at least one hollow organ is completely filled with contrast agent in the region of interest. In particular, contrast agent administration can be performed throughout the first recording phase and, if necessary, throughout the second recording phase.

[0034] In some embodiments, the method according to the present invention can also be implemented as a 4D-DSA method. In this case, the projection images of the first sequence and, if necessary, the projection images of the second shooting phase and the corresponding second sequence of projection images correspond to so-called object images or vascular images or full images (English: fill images). Other mask images required for DSA are generated, in particular, before or after the first shooting time range when the contrast agent is no longer in the at least one hollow organ, and these mask images show at least one hollow organ without contrast agent.

[0035] The duration of contrast agent flow from the contrast agent injection position to a position close to the body midline may vary depending on the blood flow velocity or anatomical condition of the specific person. The same also applies to the duration of contrast agent flow from a position close to the body midline to a position away from the body midline. Since the first duration and the second duration are obtained or determined for a specific person according to the present invention, and the first shooting phase is controlled so that the first shooting phase starts at time T1 and ends at time T1+T2, it is ensured that on the one hand, undesired projection images in a specific projection direction will not be captured before the contrast agent group substantially reaches the area of ​​interest, or the first shooting phase will not end when the contrast agent group reaches a position away from the body midline, resulting in incomplete time-resolved information.

[0036] In particular, it is achieved that the time-resolved reconstruction can completely show the time-resolved flow of the contrast agent bolus in the entire region of interest from a position close to the body midline to a position remote from the body midline. This cannot be done reliably, for example, if the start and end times of the first recording phase are determined based on assumed delay times or empirical values ​​or the like.

[0037] According to at least one embodiment, a preparatory sequence of projection images is generated in a preparatory phase before the injection start time, wherein each projection image of the preparatory sequence shows a position close to the body midline and a position away from the body midline. Here, the preparatory sequence is started simultaneously with a further injection start time for injecting contrast agent at the contrast agent injection position. The first duration and the second duration are determined based on the projection images of the preparatory sequence.

[0038] Accordingly, at other injection start times before the injection start time, contrast agent is injected in advance to determine the first duration and the second duration. That is, the test contrast agent bolus can be observed to determine the first duration and the second duration. At the injection start time, there is no contrast agent of the preparation sequence, especially in at least one hollow organ.

[0039] The projection images of the preparation sequence are not necessarily taken from different projection directions. However, it is also feasible that the projection images of the preparation sequence are taken from two or more different projection directions, so that the preparation sequence contains two or more different subsequences with constant projection directions respectively. In this way, the first duration or the second duration can be determined more reliably, especially when the position far from the midline of the body and the position close to the midline of the body are not in the same plane. However, the number of different projection directions in the preparation sequence does not necessarily have to be similar or equal to the number of different projection directions in the first shooting stage. In particular, the projection images of the preparation sequence do not necessarily have to be suitable for three-dimensional reconstruction. The number of projection images in the preparation stage can be less than, especially significantly less than, the number of projection images in the first shooting stage. Alternatively or additionally, the X-ray intensity and / or frame rate in the preparation sequence can also be lower than the X-ray intensity and / or frame rate used to generate the first sequence during the first shooting stage. This reduces the radiation burden on personnel in the preparation stage.

[0040] Since the projection images of the preparation sequence are generated in a time-defined manner, each projection image of the preparation sequence can correspond to a moment after the injection moment. In this way, it is possible to determine when the test contrast agent bolus reaches a position close to the body midline and a position away from the body midline, and the first time period and the second time period can be determined accordingly.

[0041] In order to determine the first duration and the second duration in the preparatory sequence phase based on the projection images of the preparatory sequence, known methods in terms of image intensity can be applied to the projection images of the preparatory sequence (intensity threshold, English: intensity thresholding). That is to say, for example, a predetermined area around the midline position of the body can be evaluated to determine those projection images of the preparatory sequence in which the image intensity in the area around the midline position of the body is greater than or equal to a predetermined limit value for the first time. The shooting time of the projection image thus identified is then, for example, equivalent to the first duration.

[0042] In addition, for example, a predetermined area away from the body midline position can also be evaluated in order to determine those projection images of the preparation sequence in which the image intensity in the area away from the body midline position is greater than or equal to a limit value of another predetermined limit value for the first time. The recording time of the projection image thus identified then corresponds, for example, to the sum of the first duration and the second duration.

[0043] It is also possible to use other image evaluation algorithms, for example, based on machine learning training algorithms, in order to identify the corresponding projection images in which the test contrast agent bolus first arrived at a position close to the body midline or at a position far from the body midline. In particular, it is also possible that the position close to the body midline or at a position far from the body midline does not need to be specifically selected by the user in the corresponding X-ray image. Instead, for example, the user can name a characteristic vascular structure or a characteristic point in the vascular structure of at least one hollow organ and apply the correspondingly trained algorithm to the projection images of the preparation sequence in order to automatically identify the relevant projection images corresponding to the first or second time length.

[0044] Here, the position close to the midline of the body and the position far from the midline of the body can be distinguished according to the specific application or according to the specific hollow organ to be imaged or shown. For example, the position close to the midline of the body can correspond to the bifurcation of the internal carotid artery, etc. For example, the distal position can be a point on the sigmoid sinus, or it can also be a point at a certain distance from a venous malformation, an aneurysm, or an arteriovenous fistula, etc.

[0045] According to at least one embodiment, each projection image of the preparation sequence displays a position close to the midline of the body and a position away from the midline of the body according to the same predetermined projection direction. Alternatively, the preparation sequence is composed of two or more subsequences, each subsequence includes two or more projection images, wherein each projection image of the preparation sequence displays a position close to the midline of the body and a position away from the midline of the body, and the projection directions in each subsequence are the same, and the projection directions for different subsequences are different from each other.

[0046] In this way, a preparation sequence can be carried out simply and quickly, wherein T1 and T2 can still be reliably determined.

[0047] In various embodiments, corresponding subtraction images can also be generated in a known manner based on the projection images of the preparation sequence, and the first and second durations can then be determined accordingly based on these subtraction images.

[0048] According to at least one embodiment, a first preparatory sequence of projection images is generated in a preparatory phase before the injection start time, wherein each projection image of the first preparatory sequence is shown close to the midline of the body. A second preparatory sequence of projection images is generated in the preparatory phase, wherein each projection image of the second preparatory sequence is shown away from the midline of the body. The first preparatory sequence is started simultaneously with a first other injection start time for injecting a contrast agent at a contrast agent injection site. The second preparatory sequence is started simultaneously with the first other injection time or simultaneously with a second other injection start time for injecting a contrast agent at a contrast agent injection site. The first duration is determined based on the projection images of the first preparatory sequence, and the second duration is determined based on the projection images of the second preparatory sequence.

[0049] The projection images of the first preparation sequence in particular do not show positions far from the body midline, while the projection images of the second preparation sequence do not show positions close to the body midline. In other words, the first and second durations are determined based on different preparation sequences. This enables more accurate determination of the corresponding durations by more accurately determining positions close to the body midline or away from the body midline, especially when they are relatively far away from each other in space.

[0050] For example, the projection direction for all projection images of the first preliminary sequence is constant, and the projection direction for the projection images of the second preliminary sequence can also be constant. The projection direction of the first preliminary sequence can be the same as or different from the projection direction of the second preliminary sequence. It is also feasible that the first preliminary sequence and / or the second preliminary sequence has two or more subsequences, which are distinguished from each other by constant projection directions within each subsequence.

[0051] According to at least one embodiment, the X-ray imaging method is a method for 4D-DSA.

[0052] According to at least one embodiment, a first mask sequence of projection images is generated in a first mask acquisition phase, wherein each projection image of the first mask sequence at least partially displays the at least one hollow organ according to a respective different projection direction. Each projection image of the first mask sequence corresponds to exactly one projection image of the first sequence, so that the projection direction of the projection images of the first mask sequence is identical to the projection direction of the respectively corresponding projection images of the first sequence. For each projection image of the first mask sequence, a first subtraction image is generated, in particular by means of at least one computing unit, by subtracting the projection image of the first mask sequence from the respectively corresponding projection image of the first sequence. A time-resolved three-dimensional reconstruction is generated based on the first subtraction images, in particular all generated first subtraction images.

[0053] The projection images of the first mask sequence are here in particular recorded when the contrast agent is not yet or is no longer in the at least one hollow organ. This means that this embodiment relates in particular to an X-ray imaging method for 4D-DSA. The precise assignment of the projection images of the first mask sequence to a projection image of the first sequence means that the number of projection images of the first mask sequence is equal to the number of projection images of the first sequence.

[0054] It should be noted that the duration of the first mask acquisition phase can be equal to the duration of the first acquisition phase, but this is not necessarily the case. It should also be noted that the subtraction of the individual projection images of the first mask sequence from the associated projection images of the first sequence can be performed according to known DSA methods, in particular, can also include a preprocessing or processing step of the individual projection images before the actual subtraction, and / or a reprocessing step of the resulting subtracted images.

[0055] In this way, a time-resolved display of the at least one hollow organ can be displayed more in detail, more accurately and, according to the invention, completely and reliably.

[0056] According to at least one embodiment, a second sequence of projection images is generated in the second recording phase, wherein each projection image of the second sequence at least partially displays the at least one hollow organ according to different projection directions that are respectively preset. The second recording phase starts at the end of the first recording phase or starts at the end of the first recording phase. A time-resolved three-dimensional reconstruction is generated based on the projection images of the first sequence and based on the projection images of the second sequence.

[0057] For example, in a corresponding embodiment, a time-resolved three-dimensional reconstruction is generated based on the first subtraction image and a corresponding second subtraction image generated based on the projection images of the second sequence.

[0058] The duration of the second recording phase is usually dependent on the X-ray imaging system used, the frame rate, the required image quality, etc. It is selected in particular such that all projection directions required for generating a static 3D reconstruction can be recorded.

[0059] The projection directions of the individual projection images of the second sequence are respectively different, just as described for the projection directions of the projection images of the first sequence. In addition, the projection directions of the projection images of the second sequence can also be different from all projection directions of the projection images of the first sequence. However, the latter situation is not necessary. In particular, the projection directions of each or all projection images of the second sequence can be consistent with the corresponding projection directions of the projection images of the first sequence.

[0060] As mentioned above, the injection duration at the injection moment covers not only the duration of the first recording phase but also the duration of the second recording phase. The injection duration can, for example, be equal to the sum of the durations of the first and second recording phases. In this embodiment, for example, a static three-dimensional reconstruction of at least one hollow organ can be generated based on the projection images of the second sequence and, if necessary, based on the corresponding second subtraction images. The projection images of the first sequence or the first subtraction images can be re-projected respectively, and the synthesized re-projections can be inserted into the static three-dimensional reconstruction respectively.

[0061] That is, in this way, a sequence of three-dimensional reconstructions can be generated, wherein each reconstruction of the sequence corresponds to a combination of a static three-dimensional reconstruction and a reconstruction of a corresponding projection image of the first sequence or a corresponding first subtraction image. The three-dimensional reconstruction of the sequence can then be considered as a time-resolved three-dimensional reconstruction or four-dimensional reconstruction of at least one hollow organ.

[0062] According to at least one embodiment, a stop signal for automatically ending the contrast agent injection is generated at a time prior to the end time of the second recording phase by a first time period. In particular, the contrast agent injection is automatically ended based on the stop signal.

[0063] The stop signal may be sent, for example, to a contrast medium pump for injecting contrast medium, and the contrast medium pump may automatically end the contrast medium injection according to the stop signal.

[0064] In this embodiment, the injection duration covers the duration of the first recording phase, but does not completely cover the duration of the second recording phase. The injection duration is in particular equal to the sum of the durations of the first and second recording phases minus the first duration. This has the advantage that even after the contrast agent injection is completed, at least one hollow organ in the entire region of interest is still filled with contrast agent within the first time. Thus, a static three-dimensional reconstruction can be generated. Thus, contrast agent is saved and the physical burden on the patient is reduced in this way.

[0065] According to at least one embodiment, a second mask sequence of projection images is generated in a second mask acquisition phase, wherein each projection image of the second mask sequence at least partially displays the at least one hollow organ according to a respective different projection direction. Each projection image of the second mask sequence corresponds to exactly one projection image of the second sequence, so that the projection direction of the projection images of the second mask sequence is identical to the projection direction of the respectively corresponding projection images of the second sequence. For each projection image of the second mask sequence, a second subtraction image is generated, in particular by means of at least one computing unit, by subtracting the projection image of the second mask sequence from the respectively corresponding projection image of the second sequence. A time-resolved three-dimensional reconstruction is generated based on the second subtraction image and based on the first subtraction image.

[0066] The description and explanations for the first mask sequence may be transferred analogously to the second mask sequence.

[0067] According to at least one embodiment, the projection directions of the projection images of the first and second sequences are characterized by angles within a predetermined, in particular consecutive, angular range in a predetermined plane. In a first recording phase for recording the first sequence, a first sub-region, in particular a consecutive sub-region, of the angular range is passed through, and in a second recording phase for recording the second sequence, a second sub-region, in particular a consecutive sub-region, of the angular range adjacent to the first sub-region is passed through.

[0068] In other words, the second subregion follows, in particular, the first subregion and does not overlap with the first subregion.

[0069] For example, the angle characterizing each projection direction can be given by the angle between a straight line connecting the X-ray source and the X-ray detector, which is, for example, perpendicular to the detector surface of the X-ray detector, and a predetermined reference direction in the plane. Here, the X-ray source and the X-ray detector are arranged and supported relative to each other so that they can rotate around a common rotation axis, which is perpendicular to the plane. This can be achieved, for example, by arranging the X-ray source and the X-ray detector on a so-called C-arm. In this way, each projection direction can be defined by a corresponding angle from 0° to 360°.

[0070] It should be noted that only rotations around the rotation axis are considered here. However, in a corresponding X-ray imaging system, it is also possible that the X-ray light source and the X-ray detector can be rotated in different planes. This leads to a corresponding improvement of the X-ray imaging method according to the invention.

[0071] Without limiting the generality, it can be assumed that, for example, the angle corresponding to the projection direction of the initial projection image of the first sequence is 0°. The angle range can be described as [0°, α max ], where α is applicable max <360°. The first sub-area is defined by [0°,α1], and the second sub-area is defined by [α1,α2], where 0°<α1<α2<α max .

[0072] The multiple angles of the projection images of the first sequence are distributed, for example, evenly or approximately evenly, in the first sub-area. The multiple angles of the projection images of the second sequence are distributed, for example, evenly or approximately evenly, in the second sub-area.

[0073] The first subregion and the second subregion extend immediately one behind the other and, for example, in the same direction.

[0074] In this way, it is possible to realize the first recording phase and the second recording phase using only one angular travel of the angular range.

[0075] According to at least one embodiment, the projection directions of the projection images of the first mask sequence and the second mask sequence are characterized by respective angles within the angle range in the plane, passing through a first sub-region in a first mask recording phase for recording the first mask sequence, and passing through a second sub-region in a second mask recording phase for recording the second mask sequence.

[0076] In this case, the first and the second partial region extend in particular in the same direction.

[0077] In this way, it is also possible to detect the first mask sequence and the second mask sequence over a single angular path over the entire angular range.

[0078] According to at least one embodiment, the entire angular range is traversed, in particular completely traversed, in a first recording phase for recording the first sequence, and in a second recording phase for recording the second sequence, this angular range is traversed, in particular retraversed, for example completely traversed.

[0079] In this way, the total angular range may be smaller than in the above described embodiment, in which two sub-areas of the angular range extend in the same direction for detecting the first and second sequences of projection images.

[0080] For example, in the above embodiment, the angle range is completely passed through in the first and second shooting phases, and the angle range can be passed through in a first direction in the first shooting phase, and passed through in a second direction opposite to the first direction in the second shooting phase. In this way, the time delay between the first shooting phase and the second shooting phase is reduced.

[0081] According to at least one embodiment, the angle range is completely passed through in both the first photographing phase and the second photographing phase, and the duration of the second photographing phase is equal to the second duration.

[0082] In this way, the same rotation speed or frame rate can be used when generating the second acquisition sequence as when generating the first acquisition sequence. However, in an alternative embodiment, it is also possible to use a duration different from the second duration for the second acquisition phase. In this case, the requirements for generating a static 3D reconstruction and time-resolved information can be considered independently of each other.

[0083] According to at least one embodiment, the first mask sequence is generated in the first mask acquisition phase and the second mask sequence is generated in the second mask acquisition phase, wherein the angular range is completely traversed both in the first acquisition phase and in the second acquisition phase. According to at least one such embodiment, in the first mask acquisition phase for acquiring the first mask sequence, the angular range is traversed, in particular completely traversed, and in the second mask acquisition phase for acquiring the second mask sequence, the angular range is traversed, in particular again, for example completely traversed.

[0084] According to at least one embodiment, the angular range is traversed in a first direction in a first mask recording phase, and in a second mask recording phase the angular range is traversed in a second direction or vice versa.

[0085] According to at least one embodiment, the duration of the first mask shooting phase and / or the duration of the second mask shooting phase is equal to the second duration. That is, for example, the duration of the first mask shooting phase, the second mask shooting phase, the first shooting phase and the second shooting phase are respectively equal to the second duration.

[0086] According to at least one embodiment, the projection direction of the first sequence of projection images is characterized by various angles within a preset angle range in a preset plane. The angle range is passed through in a first capture phase, wherein parameters for generating the first sequence of projection images are adjusted according to the second duration and the angle range, in particular the size of the angle range.

[0087] In other words, the parameters are determined according to the second time period and according to the angular range, and the projection images of the first sequence are generated according to the parameters determined thereby.

[0088] For example, the parameter may be a frame rate, the number of projection images of the first sequence, an X-ray dose of each projection image, etc. For example, the parameter may also be calculated based on one or more of the above variables. When setting the parameter, it is particularly important to ensure that the corresponding 3D reconstruction quality within the angle range is sufficiently high.

[0089] According to another aspect of the present invention, an X-ray imaging system is provided, which is used to display at least one hollow organ of a person in a time-resolved three-dimensional manner. The X-ray imaging system has an X-ray light source, an X-ray detector, and a drive device, and the drive device is used to position the X-ray light source and the X-ray detector relative to the shooting area according to different projection directions. The X-ray imaging system also has at least one calculation unit, which is configured to determine a first duration, especially to read the first duration through a storage medium, wherein the first duration is a contrast agent flow duration from a contrast agent injection position of a person to a predetermined position close to the body midline of at least one hollow organ, which varies from person to person. At least one calculation unit is designed to determine a second duration, especially to read the second duration through at least one storage medium, wherein the second duration is a contrast agent flow duration from a position close to the body midline of at least one hollow organ to a predetermined position away from the body midline, which varies from person to person.

[0090] The at least one computing unit is configured to control the drive device, the X-ray source, and the X-ray detector so as to generate a first sequence of projection images in a first recording phase, wherein each projection image of the first sequence at least partially displays the at least one hollow organ according to different projection directions that are respectively preset. Here, the first recording phase begins after the first time period has elapsed after the injection start time of the contrast agent at the contrast agent injection position, and the duration of the first recording phase is equal to the second time period. The at least one computing unit is configured to generate a time-resolved three-dimensional reconstruction of the at least one hollow organ based on the projection images of the first sequence.

[0091] A computing unit can be understood in particular as a data processing device containing a processing circuit. A computing unit can in particular process data for performing computing operations. The computing operations may also include operations for performing search accesses to data structures, such as a lookup table LUT (English: "look-up table").

[0092] The computing unit may include, in particular, 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”) and / or one or more field-programmable gate arrays FPGA and / or one or more single-chip systems SoC (English: “system on a chip”). The computing unit may also include one or more processors, for example, one or more microprocessors, one or more central processing units CPU (English: “central processing unit”), one or more graphics processing units GPU (English: “graphics processing unit”) and / or one or more signal processors, in particular one or more digital signal processors DSP. The computing unit may also include a physical or virtual complex of a computer or other of the units mentioned.

[0093] In various embodiments, the computing unit includes one or more hardware and / or software interfaces and / or one or more storage units.

[0094] The memory cell 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 EEPROM, 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).

[0095] The X-ray source and the X-ray detector are always positioned and / or oriented identically, regardless of the respective projection direction. The X-ray source and the X-ray detector can be rigidly connected to one another, for example, by a C-arm or the like. The drive device can include, for example, one or more motors or transmissions for moving, in particular simultaneously moving, the X-ray source and the X-ray detector in order to set the individual projection directions.

[0096] Further embodiments of the X-ray imaging system according to the invention are derived directly from different embodiments of the X-ray imaging method according to the invention, and vice versa. The individual features and the corresponding explanations and advantages associated with the various embodiments of the X-ray imaging method according to the invention can in particular be transferred analogously to the corresponding embodiments of the X-ray imaging system according to the invention. The X-ray imaging system according to the invention is in particular designed or programmed to implement the X-ray imaging method according to the invention. The X-ray imaging system according to the invention in particular implements the X-ray imaging method according to the invention.

[0097] According to another aspect of the present invention, a computer program is provided having instructions which, when executed by an X-ray imaging system according to the present invention, in particular by at least one computing unit of the X-ray imaging system, cause the X-ray imaging system to implement the X-ray imaging method according to the present invention.

[0098] The instructions may be present as program code, for example. The program code may be provided in the form of binary code or assembler and / or programming language, such as source code of C language and / or program script, such as Python, for example.

[0099] According to another aspect of the present invention, there is provided a computer-readable storage medium storing a computer program according to the present invention.

[0100] According to the invention, a computer program and a computer-readable storage medium may be understood to be a computer program product having instructions.

[0101] Further features of the invention emerge from the description, the drawings and the figure description.

[0102] The features and feature combinations mentioned above in the specification and the features and feature combinations mentioned below in the description of the figures and / or shown in the figures may be included by the present invention not only in the respectively given combination, but also in other different combinations. In particular, embodiments and feature combinations that do not have all the features originally described may also be included by the present invention. In addition, embodiments and feature combinations that exceed or deviate from the described feature combinations may also be included by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0103] The present invention will be explained in more detail below with the aid of specific embodiments and the associated schematic diagrams. In the accompanying drawings, identical or functionally identical elements may be provided with identical reference numerals. It is not necessary to repeatedly describe identical or functionally identical elements with reference to different drawings, if possible.

[0104] In the attached picture:

[0105] Figure 1 A schematic diagram showing an exemplary embodiment of an X-ray imaging system according to the present invention;

[0106] Figure 2 A schematic flow chart showing an exemplary embodiment of an X-ray imaging method according to the present invention;

[0107] Figure 3 A schematic diagram showing at least one hollow organ of a person and a position close to the midline of the body and a position away from the midline of the body;

[0108] Figure 4 schematically showing image intensity variation curves at positions close to and away from the midline of the body of at least one hollow organ;

[0109] Figure 5 A schematic flow chart showing another exemplary embodiment of the X-ray imaging method according to the present invention; and

[0110] Figure 6 A schematic flow chart shows a further exemplary embodiment of the X-ray imaging method according to the present invention. DETAILED DESCRIPTION

[0111] exist Figure 1 Schematically shows an exemplary embodiment of an X-ray imaging system 1 according to the present invention, which is used to show at least one hollow organ 7 of a person 6 (see Figure 3 ). The X-ray imaging system 1 has an X-ray light source 2, an X-ray detector 3, and a drive device, which is used to position the X-ray light source 2 and the X-ray detector 3 relative to a recording region, so as to position a person 6 or a hollow organ 7 according to different projection directions. The recording region can correspond to, for example, a region on a patient couch 5, which can be recorded by means of the X-ray light source 2 and the X-ray detector 3.

[0112] Here, the projection direction is characterized, for example, by the angle α enclosed by the line between the X-ray light source 2 and the X-ray detector 3 and the x-axis of the coordinate axis system, which spans a plane in which the X-ray light source 2 and the X-ray detector 3 can be rotated around an axis of rotation by means of a drive device, and the axis of rotation is in particular parallel to one of the x-axis and the y-axis and perpendicular to the z-axis.

[0113] In addition, the X-ray imaging system 1 has at least one computing unit 4, which can control the X-ray source 2 to emit X-rays on the one hand, and on the other hand enable the X-ray detector 3 to receive corresponding detector data, which corresponds to the projection image according to the current projection direction. The at least one computing unit 4 can also control the drive device to set different projection directions.

[0114] The x-ray imaging method according to the invention can be carried out with the aid of the x-ray imaging system 1 . Figure 2 A schematic flow chart showing an exemplary embodiment of such an X-ray imaging method is shown.

[0115] In the preparation phase V, a first time period T1 and a second time period T2 are determined for the person 6. The first time period T1 is the time period for the contrast agent to be injected from the predetermined contrast agent injection position of the person 6 to the predetermined position 8 close to the midline of the body of the at least one hollow organ 7 (see Figure 3 The second time duration T2 is the time duration of the contrast agent from the position 8 close to the body midline of at least one hollow organ 7 to the predetermined position 9 far from the body midline (see Figure 3 ) and the duration of flow varies from person to person. Figure 3 Schematically, two X-ray recordings, in particular subtraction images, of a vascular tree in the venous phase and in the arterial phase after contrast agent administration can be shown, as well as an exemplary position close to the body midline 8 and an exemplary position far from the body midline 9. In a corresponding embodiment of the X-ray imaging method, the vascular tree corresponds to at least one hollow organ 7.

[0116] In the first recording phase A1, a first sequence of X-ray projection images is generated, wherein each projection image of the first sequence at least partially represents the hollow organ 7 according to different projection directions that are respectively preset. In this case, the first recording phase A1 starts after a first time period T1 after the injection start time, at which the injection of contrast agent begins at the contrast agent injection site. The duration of the first recording phase A1 is equal to the second time period T2.

[0117] For example, a second sequence of projection images is generated in a second recording phase A2 after the first recording phase A1, wherein each projection image of the second sequence at least partially shows at least one hollow organ 7 according to a correspondingly different projection direction. The second recording phase A2 starts at the end of the first recording phase A1.

[0118] Based on the first sequence of projection images and, if necessary, also based on the second sequence of projection images, a time-resolved three-dimensional reconstruction of the at least one hollow organ 7 is generated by means of at least one computing unit 4. For example, a static three-dimensional reconstruction of the at least one hollow organ 7 can be generated based on the second sequence of projection images, and the first sequence of projection images can be respectively reprojected into this static three-dimensional reconstruction in order to generate a time-resolved three-dimensional reconstruction as a whole.

[0119] For example, in some embodiments, the X-ray imaging method is also implemented as a 4D-DSA method. In this case, a first mask sequence of projection images is generated in the first mask recording phase M1, wherein each projection image of the first mask sequence at least partially shows at least one hollow organ 7 according to different projection directions that are respectively preset. Each projection image of the first mask sequence corresponds to exactly one projection image of the first sequence, so that the projection direction of the projection image of the first mask sequence is the same as the projection direction of the respectively corresponding projection image of the first sequence. For each projection image of the first mask sequence, a first subtraction image is generated by subtracting the projection image of the first mask sequence from the respectively corresponding projection image of the first sequence.

[0120] For example, in the second mask recording phase M2, a second mask sequence of projection images is generated, wherein each projection image of the second mask sequence at least partially shows at least one hollow organ 7 according to a correspondingly different projection direction. In this case, each projection image of the second mask sequence corresponds to exactly one projection image of the second sequence, so that the projection direction of the projection image of the second mask sequence is the same as the projection direction of the respectively corresponding projection image of the second sequence. For each projection image of the second mask sequence, a second subtraction image is generated by subtracting the projection image of the second mask sequence from the respectively corresponding projection image of the second sequence.

[0121] Subsequently, a time-resolved 3D reconstruction is generated from the first subtracted image and, for example, all generated second subtracted images. A static 3D reconstruction of at least one hollow organ 7 can be generated from the second subtracted images, and the first subtracted images can be reprojected into the static 3D reconstruction in each case in order to generate a time-resolved 3D reconstruction.

[0122] In the preparation phase V, for example, a preparation sequence of projection images can be generated, wherein each projection image of the preparation sequence shows a position close to the body midline 8 and a position far from the body midline 9. At the same time as another injection start time for injecting a contrast agent at a contrast agent injection site, the preparation phase is started, and the first time length T1 and the second time length T2 are determined based on the projection images of the preparation sequence.

[0123] Figure 4For this purpose, a time-dependent variation curve 10 of the image intensity of the projection images of the preparation sequence at a position close to the body midline 8 is schematically shown, and a time-dependent variation curve 11 of the image intensity at a position away from the body midline 9 is correspondingly shown. The first time duration T1 and the second time duration T2 can be determined, for example, in the following manner, that is, the intersection points of the respective rising edges of the time-dependent variation curves 10, 11 with the horizontal line are determined, and the horizontal line is formed by the predetermined limit intensity I t The first duration T1 is equivalent to the time-varying curve 10 at the position 8 near the midline of the body reaching the ultimate strength I for the first time. t The second time duration T2 corresponds to the time-varying curve 10 and the ultimate strength I t The intersection of the curve 11 and the time-dependent variation curve 11 first reaches the ultimate strength I t In other embodiments, different limit intensities can also be used for the two time-dependent variation curves 10, 11. However, T1 and T2 do not necessarily have to be determined based on the same preparation sequence. Different preparation phases can be used for T1 and T2.

[0124] The respective number of projected images in the first and second recording phase A1 , A2 and thus the angular distance between directly successive projected images of the first recording phase A1 and (if the duration is set) the second recording phase A2 is determined in particular by the desired image quality.

[0125] exist Figure 5 Schematically illustrating a process of another exemplary embodiment of the X-ray imaging method according to the present invention.

[0126] After the injection start time, after an X-ray delay time equal to the first duration T1, the first sub-area 12a of the angle range 12 passes through the angle α in the first recording phase A1. The first sub-area 12a is passed during the second duration T2. ​​Subsequently, the second sub-area 12b of the angle range 12 is passed during another duration ΔT in the second recording phase A2. The first sub-area 12a and the second sub-area 12b together form the angle range 12, and the first sub-area and the second sub-area are passed in sequence in the same direction. Including the X-ray delay time, that is, for example, it takes time T1+T2+ΔT to generate the first sequence and the second sequence.

[0127] The second sub-area 12b can, for example, correspond to an overall angular range of 200°, and the first sub-area of ​​the angular range can correspond to, for example, 60°. That is to say, in the angular range 12, the angle α is more than 260° as a whole. An angular range different from this can be selected. As shown in the figure, for an angular range of 200°, a reliable static three-dimensional reconstruction can be achieved. The additional 60° of the first sub-area 12a is used to detect time-resolved information.

[0128] If the X-ray imaging method is implemented as a 4D-DSA method, the entire angle range 12 is also traversed in the mask phases M1, M2 as a whole, for example (but not necessarily) within the same overall time T2+ΔT. In this case, for example, the first sub-area 12a is traversed in the first retina recording phase M1, and then the second sub-area 12b is traversed in the second mask recording phase M2. In an optional step M' between the second mask recording phase M2 and the first recording phase A1, the angle α can be reset by corresponding positioning of the X-ray source 2 and the X-ray detector 3.

[0129] Figure 6 Another schematic flow chart of an exemplary embodiment of such an X-ray imaging method is shown. Here, a first recording phase A1 begins after a first time period T1 has elapsed after the injection start time. In the first recording phase A1, the angle α passes through the angle range 13 in a first direction within a second time period T2. In the subsequent second recording phase A2, the angle α passes through the angle range 13 again, for example, in a second direction opposite to the first direction. This also takes place within the second time period T2, but this is not necessarily the case.

[0130] Since the angular range 13 is completely traversed both in the first recording phase A1 and in the second recording phase A2, the angular range can be selected to be smaller than Figure 5 The angle range 12 is shown in FIG. 13 . For example, the angle range 13 may be 200°. If the second recording phase A2 also has a duration of T2, the time period from the injection start time to the end of the second recording phase A2 is T1+2*T2.

[0131] In the case of 4D-DSA, the angle range 13 is also completely passed through twice before the injection start time, once in the first mask recording phase M1 in the first direction and once in the second eye mask recording phase M2 in the second direction. The mask recording phases M1, M2 can also each have a second duration T2. ​​In this case, the entire recording time is given by T+4*T2. However, this is not mandatory.

[0132] Regardless of the grammatical gender of a particular term, persons include males and females.

Claims

1. An X-ray imaging method for the time-resolved three-dimensional display of at least one hollow organ (7) of a person (6), wherein: - determining a first duration (T), which is a flow duration of a contrast medium from a predetermined contrast medium injection site of a person (6) to a predetermined location (8) close to the midline of the body of at least one hollow organ (7), which varies from person to person; - determining a second time duration (T2), which is a flow time duration of the contrast agent from a position (8) close to the body midline of the at least one hollow organ (7) to a predetermined position (9) away from the body midline, which varies from person to person; - generating a first sequence of projection images in a first recording phase (A1), wherein each projection image of the first sequence at least partially shows the at least one hollow organ (7) according to a respectively predefined different projection direction; - the first recording phase (A1) starts after the first time period (T1) has passed since the start of injection of the contrast medium at the contrast medium injection site, and the duration of the first recording phase (A1) is equal to the second time period (T2); and - generating a time-resolved three-dimensional reconstruction of the at least one hollow organ (7) from the first sequence of projection images.

2. The X-ray imaging method according to claim 1, wherein: - generating a preparation sequence of projection images in a preparation phase (V) before the injection start time, wherein each projection image of the preparation sequence shows a position close to the midline of the body (8) and a position far from the midline of the body (9); - the preparation sequence is started simultaneously with a further injection start time for injecting contrast agent at the contrast agent injection site; and - The first duration (T1) and the second duration (T2) are determined based on the projection images of the preparation sequence.

3. The X-ray imaging method according to claim 2, wherein: - each projection image of the preparation sequence is displayed in the same predetermined projection direction, close to the body midline position (8) and away from the body midline position (9); or -The preparation sequence is composed of two or more subsequences, each subsequence includes two or more projection images, wherein each projection image of the preparation sequence shows a position close to the midline of the body (8) and a position away from the midline of the body (9), and the projection directions in each subsequence are the same, and the projection directions for different subsequences are different from each other.

4. The X-ray imaging method according to claim 1, wherein: - generating a first preparation sequence of projection images in a preparation phase (V) before the injection start time, wherein each projection image of the first preparation sequence is shown close to the midline of the body (8); - generating a second preliminary sequence of projection images in the preliminary phase (V), wherein each projection image of the second preliminary sequence is shown at a position (9) remote from the midline of the body; - said first preparation sequence is started simultaneously with a first further injection start time for injecting contrast agent at a contrast agent injection site; - the second preparation sequence is started simultaneously with the first further injection time or simultaneously with a second further injection start time for injecting contrast agent at the contrast agent injection site; - the first duration (T1) is determined based on the projection images of the first preliminary sequence, and the second duration (T2) is determined based on the projection images of the second preliminary sequence.

5. A method according to any one of the preceding claims, wherein: - generating a first mask sequence of projection images in a first mask recording phase (M1), wherein each projection image of the first mask sequence at least partially displays the at least one hollow organ (7) according to a respective different projection direction; - each projection image of the first mask sequence corresponds to exactly one projection image of the first sequence, so that the projection direction of the projection images of the first mask sequence is the same as the projection direction of the respectively corresponding projection images of the first sequence; - for each projection image of the first mask sequence, generating a first subtracted image by subtracting the projection image of the first mask sequence from the respectively corresponding projection image of the first sequence; and - generating a time-resolved three-dimensional reconstruction from said first subtracted image.

6. A method according to any one of the preceding claims, wherein: - generating a second sequence of projection images in the second recording phase (A2), wherein each projection image of the second sequence at least partially displays the at least one hollow organ (7) according to a respectively predefined different projection direction; - the second recording phase (A2) starts at the end time of the first recording phase (A1); and - generating a time-resolved three-dimensional reconstruction from said second sequence of projection images.

7. The X-ray imaging method according to claim 6, wherein: - generating a second mask sequence of projection images in a second mask recording phase (M2), wherein each projection image of the second mask sequence at least partially displays the at least one hollow organ (7) according to a respective different projection direction; - each projection image of the second mask sequence corresponds to exactly one projection image of the second sequence, so that the projection direction of the projection images of the second mask sequence is identical to the projection direction of the respectively corresponding projection images of the second sequence; - for each projection image of the second mask sequence, generating a second subtracted image by subtracting the projection image of the second mask sequence from the respectively corresponding projection image of the second sequence; and - generating a time-resolved three-dimensional reconstruction from said second subtracted image.

8. The X-ray imaging method according to claim 6 or 7, wherein: - the projection directions of the projection images of the first and second sequences are characterized by respective angles (α) within a predetermined angular range (12, 13) in a predetermined plane; and - in the first recording phase (A1), a first sub-region (12a) of the angular range (12, 13) is passed through, and in the second recording phase (A2), a second sub-region (12b) of the angular range (12, 13) which is adjacent to the first sub-region (12a) is passed through.

9. The X-ray imaging method according to claim 5, claim 7 and claim 8, wherein: - the projection directions of the projection images of the first mask sequence and the second mask sequence are characterized by respective angles (α) within the angle range (12, 13) in the plane; - in the first mask recording phase (M1), the first sub-region (12a) is passed through, and in the second mask recording phase (M2), the second sub-region (12b) is passed through.

10. The X-ray imaging method according to claim 6 or 7, wherein: - the projection direction of the first sequence of projection images is characterized by various angles (α) within a predetermined angular range (12, 13) in a predetermined plane; and The angular range (12, 13) is passed through in the first recording phase (A1) and the angular range (12, 13) is passed through in the second recording phase (A2).

11. The X-ray imaging method according to claim 10, wherein: In the first recording phase (A1), the angular range (12, 13) is traversed in a first direction, and in the second recording phase (A2), the angular range is traversed in a second direction opposite to the first direction.

12. The X-ray imaging method according to any one of claims 5, 7 and 10 or 11, wherein: - the projection direction of the projection images of the first mask sequence is characterized by angles within the angle range (12, 13) in the plane; and The angle range (12, 13) is passed through in the first mask recording phase (M1) and the angle range (12, 13) is passed through in the second mask recording phase (M2).

13. The X-ray imaging method according to any one of claims 6 to 12, wherein: At a time which is a first time period (T1) before the end time of the second recording phase (A2), a stop signal for automatically ending the contrast agent injection is generated.

14. The X-ray imaging method according to any one of claims 1 to 7, wherein: - the projection direction of the first sequence of projection images is characterized by various angles (α) within a predetermined angular range (12, 13) in a predetermined plane; and - in the first recording phase (A1) the angular range is passed through, wherein parameters for generating a first sequence of projection images are adjusted as a function of the second time period (T2) and the angular range.

15. An X-ray imaging system (1) for time-resolved three-dimensional display of at least one hollow organ (7) of a person (6), the X-ray imaging system (1) comprising an X-ray light source (2), an X-ray detector (3), a drive device and at least one computing unit (4), the drive device being used to position the X-ray light source (2) and the X-ray detector (3) relative to a photographing area according to different projection directions, the computing unit being configured to - determining a first duration (T), which is a flow duration of a contrast medium from a predetermined contrast medium injection site of a person (6) to a predetermined location (8) close to the midline of the body of at least one hollow organ (7), which varies from person to person; - determining a second time duration (T2), which is a flow time duration of the contrast agent from a position (8) close to the body midline of the at least one hollow organ (7) to a predetermined position (9) away from the body midline, which varies from person to person; - controlling the drive device, the X-ray source (2) and the X-ray detector (3) in order to generate a first sequence of projection images in a first recording phase (A1), wherein: Each projection image of the first sequence at least partially displays the at least one hollow organ (7) according to different respectively preset projection directions, wherein the first shooting phase (A1) starts after the first time period (T1) has passed after the injection start time of the contrast agent at the contrast agent injection position, and the duration of the first shooting phase (A1) is equal to the second time period (T2); and - generating a time-resolved three-dimensional reconstruction of the at least one hollow organ (7) from the first sequence of projection images. 16 . A computer program product having instructions which, when run by an X-ray imaging system according to claim 15 , implement the X-ray imaging method according to claim 1 .

Images