Contrast agent-based vascular imaging

Abstract

An X-ray contrast agent (K) is described. The X-ray contrast agent (K) has an X-ray absorption, a variation of the X-ray absorption between at least two different X-ray photon energies (E(1), E(2)) being significantly different from a variation of the X-ray absorption of calcium between at least two different X-ray photon energies (E(1), E(2)). An X-ray imaging method is also described. Furthermore, an image reconstruction apparatus (50) is described. An X-ray imaging system (60) is also described.

Description

Technical Field

[0001] This invention relates to an X-ray contrast agent. Furthermore, this invention relates to an X-ray imaging method using the aforementioned X-ray contrast agent. This invention also relates to an image reconstruction apparatus. This invention further relates to an X-ray imaging system. Background Technology

[0002] With the help of modern imaging methods, two-dimensional or three-dimensional image data is usually generated. This image data can be used to visualize the imaged object under inspection, and can also be used for other applications.

[0003] These imaging methods are typically based on the detection of X-ray radiation, in which so-called projection measurement data is generated. For example, projection measurement data can be acquired using a computed tomography (CT) system.

[0004] Contrast agents are frequently used during X-ray image recording. These agents are injected into the patient to improve the contrast of the recorded images, thereby facilitating diagnosis. One example of the use of contrast agents is in X-ray imaging of blood vessels. This X-ray imaging can be performed using conventional systems, C-arm systems, vascular contrast systems, or CT systems. Iodine is typically used as the X-ray contrast agent in this type of imaging.

[0005] However, a problem arises when using iodine for vascular contrast: bone and calcification within the vessels, as well as partially calcified plaques, have density values ​​similar to those of contrast-filled vessels, especially in complex anatomical structures such as the skull region. Iodine-filled vessels, bone, and calcification overlap within the vessels, making them no longer accurately distinguishable in the image. Therefore, particularly for vessels with smaller diameters, in cases of severe calcification, it is often no longer possible to determine the vessel width, also known as the lumen, using CT vascular contrast. This phenomenon represents a limitation in the use of CT vascular contrast in the coronary arteries and peripheral leg vessels.

[0006] Traditionally, attempts have been made to separate bone and calcifications or partially calcified plaques in blood vessels from areas visible with iodine contrast agents by subtracting previous recordings of the area to be recorded—a process performed without contrast agents. However, registration problems arise due to patient movement caused by time discrepancies between previous and primary recordings. Furthermore, the additional image recordings increase the patient's radiation dose.

[0007] Using software-based methods to separate image information related to blood vessels from image information related to bone is also prone to errors. These errors occur especially in complex imaging cases, such as those of the skull base. Furthermore, due to the flowering effect, it is impossible to remove (partially) calcified plaques from vascular imaging. This is because partially calcified plaques appear larger than they actually are due to the flowering effect. If the plaque is removed from the image, areas where no image information is available are left because the area previously covered by the plaque is too large.

[0008] One method for separating bone material and iodine-containing contrast agent pixels is to use dual-energy or multi-energy imaging. In this case, the same area is imaged using at least two different average X-ray energies. However, in a simple variation of assigning pixels to contrast agent or bone material by classification, similar problems arise as with software-based methods. Incorrect separation of iodine-containing and plaque-containing areas can occur, particularly in complex vascular structures. This also leads to an magnified representation of calcified areas. If these areas are subsequently extracted to make the vessels visible, it is unclear how the areas covered by the magnified representation will appear in the image.

[0009] In a relatively newer method, dual-energy imaging is used to calculate two distinct images based on the recording. One image shows the calcium-containing structure, while the other shows the area where a contrast agent has been applied. Therefore, neither bone nor vascular calcifications are visible in the contrast-treated image. While this avoids magnified representation of calcifications in the image and provides information about areas otherwise covered by magnified structures, a remaining problem is that previously used contrast agents, such as iodine, and bone or calcifications are very similar in their spectral absorption characteristics across the X-ray recording energy range (40 keV to 140 keV). This means that X-ray absorption increases dramatically with decreasing energy in both materials. Figure 1 The absorption for low-energy recordings (denoted by E(1)) and high-energy recordings (denoted by E(2)) is shown in the figure. Due to the similar properties of conventional contrast agents iodine and calcium, the resulting material images exhibit very high image noise and inaccurate material separation. Although the problems of high image noise and inaccurate material separation can be eliminated by significantly increasing the radiation dose, this practice increases the health burden on patients and is not feasible in certain types of examinations, such as coronary artery contrast, due to technical limitations.

[0010] Therefore, there is a problem in achieving good quality vascular visualization with low radiation dose. Summary of the Invention

[0011] This objective is achieved by an X-ray contrast agent, an X-ray imaging method, an image reconstruction device, and an X-ray imaging system.

[0012] The X-ray contrast agent according to the invention has X-ray absorption such that its variation between at least two different X-ray photon energies is significantly different from the variation of calcium's X-ray absorption between said at least two different X-ray photon energies.

[0013] Ideally, the absorption of the X-ray contrast agent according to the invention should remain nearly constant between at least two different X-ray photon energies. In this case, "significant" should be understood as the variation being less than half that of calcium under the selected different X-ray photon energies.

[0014] Advantageously, the spectral deviation characteristics of the contrast agent according to the invention can be used to separate the area infiltrated by the contrast agent from other image areas that are calcified or partially calcified. Particularly in vascular contrast imaging, it produces more precise values ​​for the opening width of the displayed vessels, resulting in improved accuracy compared to conventionally used contrast agents. Therefore, the X-ray contrast agent according to the invention can be advantageously used for imaging blood vessels because the inner diameter of the vessels can thus be displayed with particularly high precision.

[0015] In the X-ray imaging method according to the present invention, a contrast agent according to the present invention is first selected. Furthermore, raw X-ray data from the contrast-infiltrated area of ​​the subject being examined is detected using a multi-energy recording method. The X-ray imaging method according to the present invention can be executed as a computer-implemented method based on the detected data.

[0016] Based on the raw X-ray data, the material is broken down into data that can be allocated to the contrast agent according to the invention or to calcium.

[0017] In principle, known material decomposition is based on the consideration that X-ray attenuation values ​​measured using an X-ray image recording apparatus can be described as a linear combination of the X-ray attenuation values ​​of the so-called basic material relative to the X-ray quantum energy distribution or X-ray photon energy. For different X-ray quantum energy distributions, the measured X-ray attenuation values ​​are generated from at least two original datasets or image datasets reconstructed from them. In the application according to the invention, the material or basic material is, on the one hand, calcium, and on the other hand, the X-ray contrast agent according to the invention. The X-ray attenuation of the basic material relative to the X-ray radiation energy is known in principle, or can be determined by prior measurements on a phantom and stored in tabular form for retrieval during material decomposition. The result of material decomposition is the spatial density distribution of at least two materials—namely, the contrast agent according to the invention and calcium in the patient's body—from which the basic material portion or combination of basic materials can be determined for each volume element in the body region to be imaged in the patient.

[0018] Material decomposition can be performed directly using raw data or using reconstructed image data. In either case, within the scope of this method, at least two image datasets are generated based on the spectral decomposition data, whether raw data or image data: the at least two image datasets include a first image dataset and a second image dataset, the first image dataset representing a first image region to which the contrast agent according to the invention has been applied, and the second image dataset representing a second image region preferably complementary to the first image region, in which calcium-containing structures can be seen.

[0019] In cases where the first and second image datasets are to be represented complementaryly, the regions to which the contrast agent according to the invention has been applied and the calcium-containing structures can be shown together in one image, for example, by overlaying the two image datasets, wherein the relative positions of the different structures or materials and the spatial separation or boundaries between these different structures or materials are clearly visible.

[0020] If the different materials represented by the two image datasets are mixed, the first and second image datasets can also be displayed separately in two separate images to show the different materials separately.

[0021] The X-ray imaging method according to the invention enables the separate display of image regions containing calcium and image regions to which the contrast agent according to the invention has been applied. This, for example, enables a more precise display of the diameter of blood vessels, which facilitates more reliable diagnosis based on image data of vascular contrast. Furthermore, due to the different spectral absorption characteristics of the contrast agent according to the invention and other materials to be displayed, the X-ray dose can be selected to be lower than that in conventional imaging methods.

[0022] The image reconstruction apparatus according to the invention has a determining unit for determining at least two different X-ray photon energies, wherein the contrast agent according to the invention is significantly different from the variation of calcium X-ray absorption between the at least two different X-ray photon energies.

[0023] Within the scope of multi-energy recording methods, the selection of energy values ​​can be considered when choosing the energy or average energy value of the X-ray source used for imaging. If a counting detector is used to detect X-ray radiation, an energy threshold or interval can be selected to include the aforementioned energy values.

[0024] A portion of the image reconstruction apparatus according to the invention is also a raw data receiving unit for receiving raw X-ray data from an area of ​​the object being examined that is at least partially permeated by a contrast agent, using a multi-energy recording method.

[0025] The image reconstruction apparatus according to the invention further includes: a decomposition unit for performing material decomposition of the contrast agent and calcium based on raw X-ray data; and a reconstruction unit for reconstructing at least two image datasets based on the material decomposition. In principle, as already explained, such material decomposition is known when displaying images of several materials using dual-energy or multi-energy imaging.

[0026] At least two image datasets are included, comprising a first image dataset and a second image dataset, wherein the first image dataset represents a first image region to which a contrast agent has been applied, and the second image dataset preferably represents a second image region complementary to the first image region. The image reconstruction apparatus according to the invention shares the advantages of the X-ray imaging method according to the invention.

[0027] The X-ray imaging system according to the invention has an image reconstruction unit according to the invention. The X-ray imaging system according to the invention may preferably include a CT vascular contrast device. The X-ray contrast agent according to the invention is particularly advantageous for image display of blood vessels, because it allows for particularly precise display of the inner diameter of the vessels.

[0028] The main components of the image reconstruction apparatus according to the invention can mostly be formed as software components. This particularly relates to the decomposition unit and reconstruction unit of the image reconstruction apparatus according to the invention. However, in principle, especially when particularly fast computation is involved, these components can also be partially implemented in the form of software-supported hardware, such as FPGAs. Similarly, the required interfaces, for example when only data receiving from other software components is involved, can be designed as software interfaces. However, they can also be designed as hardware-constructed interfaces controlled by suitable software.

[0029] Designing to a large extent according to software has the following advantages: Imaging systems or image reconstruction devices using existing medical technologies can be easily modified via software updates to operate in accordance with the invention. In this regard, this objective is also achieved by a corresponding computer program product comprising: a computer program that can be directly loaded into the storage device of the X-ray imaging system; and program segments that, when executed in the X-ray imaging system, implement the software-implementable steps of the X-ray imaging method according to the invention. In addition to the computer program, this computer program product may, if desired, include additional components such as documentation and / or additional components, also called hardware components, such as hardware keys (dongles, etc.) for using the software.

[0030] For transmission to and / or storage on or within a subsystem, a computer-readable medium, such as a memory stick, hard disk, or other removable or permanently mounted data carrier, may be used, on which program segments of a computer program that can be read and executed by a computer unit are stored. The computer unit may, for example, have one or more microprocessors working together. For instance, the computer unit may be part of a terminal or control unit of an imaging system (e.g., a CT facility), but it may also be part of a remotely located server system within a data transmission network communicating with the imaging system.

[0031] The following description contains particularly advantageous designs and modifications of the invention. In particular, each claim of one class of claims may be modified in a manner similar to the dependent claims of another class of claims. Furthermore, within the scope of the invention, various different features of different embodiments and claims may be combined to form new embodiments.

[0032] In a variant of the X-ray contrast agent according to the invention, the X-ray absorption of the contrast agent does not differ significantly for at least two X-ray photon energies. Advantageously, the X-ray contrast agent according to the invention therefore differs from materials such as calcium, particularly those appearing in vascular contrast, in terms of its photon energy-dependent absorption characteristics.

[0033] Of particular advantage is that the X-ray absorption spectrum of the X-ray contrast agent according to the invention is similar to that of water or soft tissue. This is because water or soft tissue has properties independent of X-ray photon energy in the energy range associated with contrast with blood vessels, and therefore can be easily separated from other body materials such as calcium.

[0034] In a particularly advantageous embodiment of the invention, the X-ray contrast agent according to the invention comprises one of the following materials:

[0035] -Tungsten;

[0036] - Tantalum;

[0037] -hafnium;

[0038] -gold.

[0039] All of the materials mentioned have the advantage of water-like absorption properties, which allows them to be easily separated from or displayed separately from calcium-containing substances in the examination area.

[0040] In one design of the X-ray imaging method according to the invention, it features a multi-energy imaging method, preferably a dual-energy imaging method. In the case of the multi-energy imaging method, at least two different X-ray tube voltages are specified, wherein the X-ray absorption variation of the contrast agent according to the invention is significantly different from that of calcium. Furthermore, at least two X-ray image recordings are performed using at least two different X-ray tube voltages to acquire a first raw dataset and at least one second raw dataset. The material is then decomposed based on the at least two raw datasets. In this variation, X-rays with different X-ray spectra are generated using different X-ray tube voltages, and these X-rays are used to generate at least two raw datasets, which are used to separate different materials in the imaging.

[0041] In an alternative design of the X-ray imaging method according to the invention, raw X-ray data is detected, which is recorded in an energy-resolved manner using a photon-counting detector. An energy threshold for the photon-counting detector is defined such that, under different energy ranges defined by the energy threshold, the change in X-ray absorption of the contrast agent according to the invention is significantly different from the change in X-ray absorption of calcium. Furthermore, the material is decomposed based on the energy-resolved raw data. Advantageously, in this variation, only one X-ray tube is needed to irradiate one examination area. Attached Figure Description

[0042] The invention will now be explained in detail again with reference to the accompanying drawings and embodiments.

[0043] Figure 1 A view showing the relationship between the absorption characteristics of contrast agent iodine and bone material calcium and X-ray photon energy;

[0044] Figure 2 A view showing the relationship between the absorbance values ​​of the contrast agent iodine and the material tungsten and the tube voltage of the X-ray equipment;

[0045] Figure 3 A view showing the relationship between the absorption properties of contrast agents iodine and tungsten, as well as calcium and water, and X-ray photon energy;

[0046] Figure 4 A flowchart illustrating an X-ray imaging method according to an embodiment of the present invention is provided.

[0047] Figure 5 This is a schematic diagram of an image reconstruction apparatus according to an embodiment of the present invention;

[0048] Figure 6 This is a schematic diagram of a CT system according to an embodiment of the present invention. Detailed Implementation

[0049] Figure 1 View 10 shows the absorption characteristics of the contrast agent iodine I and bone material calcium Ca in relation to the energy E of X-ray photons. PH The relationship between the mass absorption coefficient K and the X-ray photon energy E is plotted to illustrate the absorption of the above materials. PH The relationship. Figure 1 The diagram also shows a typical average energy E(1) for low-energy image recording and an average energy E(2) for high-energy image recording using dual-energy image recording. (See also...) Figure 1 As can be seen, the two curves for the mass absorption coefficients of iodine (I) and calcium (Ca) show very similar trends. It is important to consider that iodine and calcium can exist at different densities and concentrations in the material. This leads to… Figure 1 The absorption curves shown are completely superimposed on each other in the worst case. Therefore, it becomes impossible to separate the two materials in the image.

[0050] Figure 2 View 20 is shown, which illustrates the absorbance values ​​of the contrast agent iodine I and the material tungsten W. s With the tube voltage V of the X-ray equipment T The relationship is as follows: Although the X-ray absorption of iodine decreases with increasing energy, the X-ray absorption of tungsten (W) does not change much with energy.

[0051] Especially in dual-energy imaging using tin filters at 80kV low energy and 140kV or 150kV high energy, the X-ray absorption of tungsten (W) is significantly higher than that of iodine (I). s In reality, there is no change. Therefore, by generating two separately recorded image points using different tube voltages, it is easy to correlate them with one of the two contrast agents. For example, points with identical absorption in both images can be clearly correlated with the material tungsten, while points with very different absorption in both images can be clearly correlated with the material iodine.

[0052] Figure 3 View 30 shows the absorption characteristics of contrast agents iodine I and tungsten W, as well as calcium Ca and water H2O, in relation to the energy E of X-ray photons. PH The relationship between the mass absorption coefficient K and the X-ray photon energy E was plotted for the aforementioned materials. PH The relationship. In Figure 3It can be clearly seen that, in the range of 40 to 80 keV, the absorption of contrast agent iodine I and bone material calcium Ca increases with photon energy E. PH The absorption decreases significantly with increasing concentration. It is important to note that the absorption is presented logarithmically. In contrast, tungsten (W) behaves more like water (H₂O). That is, for a first photon energy E(1) of approximately 45 keV, the absorption of tungsten (W) is equal to the absorption at a second photon energy E(2) of approximately 80 keV. Because the properties of tungsten (W) are very different from those of calcium (Ca), the image area where tungsten (W) is applied can therefore be easily separated from or displayed separately from areas dominated by calcium (Ca).

[0053] Figure 4 Flowchart 400 is shown, illustrating an X-ray imaging method according to an embodiment of the present invention. In step 4.I, a tungsten-based contrast agent is first selected for vascular contrast imaging of the patient's examination area, such as the patient's skull. Furthermore, in step 4.II, raw X-ray data RD is detected, which is recorded using a dual-energy recording method from the area of ​​the subject O infiltrated by the selected contrast agent. Figure 4 In the method shown, raw X-ray data recorded using X-ray radiation with two different energy values, E(1) and E(2), are detected. The energy values ​​are selected such that the absorption characteristics of the selected contrast agent (in this embodiment, a tungsten-based contrast agent) are identical for both energy values. This process can be achieved, for example, by using two detectors arranged spatially apart from each other, wherein a filter is introduced in front of one of the two detectors in the beam path, which filters out a portion of the spectrum of the X-ray radiation. Thus, two raw datasets assigned different X-ray energies E(1) and E(2) are detected.

[0054] In step 4.III, two image datasets BD1 and BD2 are reconstructed based on the two original datasets generated in step 4.II. Here, a first image dataset BD1 is generated, representing a first image region to which the contrast agent tungsten is applied; and a second image dataset BD2 is generated, representing a second image region complementary to the first image region, in which calcium-based structures are visible. The two image datasets BD1 and BD2 can be generated, for example, by means of material decomposition based on the original data obtained in step 4.II.

[0055] exist Figure 5The reconstruction apparatus 50 is shown. The reconstruction apparatus 50 has a determining unit 51. The determining unit 51 receives information about the contrast agent K to be used and determines two different X-ray photon energy values ​​E(1), E(2), at which the selected contrast agent K behaves like water, that is, the absorption is the same for both energy values. On the other hand, the image region to be separated from the contrast agent K and infiltrated with calcium has a significant spectral dependence on absorption within the energy range usable by the X-ray device, and therefore can be easily distinguished from the selected contrast agent K once the energy values ​​E(1), E(2) are determined. For example, the energy values ​​E(1), E(2) can be selected based on the energy-related absorption values ​​of the selected contrast agent K stored in a data memory.

[0056] The selection of energy values ​​E(1) and E(2) can be within the scope of multi-energy recording methods, taking into account when selecting the energy or average energy value of the X-ray source used for imaging. If a counting detector is used to detect X-ray radiation, an energy threshold or interval can be selected to include the aforementioned energy values.

[0057] The reconstruction apparatus 50 also includes a raw data receiving unit 52 for receiving raw X-ray data RD. The raw data RD is acquired using dual-energy CT methods from areas of the examined subject that have been at least partially penetrated by the contrast agent K.

[0058] The raw data RD is transmitted to the decomposition unit 53, which performs material decomposition of the contrast agent K and calcium based on the raw X-ray data RD. The material-specific components MA1 and MA2 of the absorption spectra assigned to different materials from the raw data are transmitted to the reconstruction unit 54, which reconstructs at least two image datasets BD1 and BD2 based on the material-specific components MA1 and MA2. The first image dataset BD1 shows a first image region to which the contrast agent has been applied, and the second image dataset BD2 shows a second image region complementary to the first image region, in which calcium-containing structures or structures contrasted with iodine are dominant. The resulting image datasets BD1 and BD2 are output via an output interface 55, for example, to a display unit, a data storage unit, or a control computer with an image display.

[0059] Figure 6 An X-ray imaging system according to an embodiment of the present invention is shown, in this case a CT system 60.

[0060] The CT system 60, designed as a dual-energy CT system, primarily consists of a common scanner 9. Within this scanner, a projection measurement data acquisition unit 5, mounted on a gantry 11, surrounds a measurement space 12. This projection measurement data acquisition unit has two detectors 16a and 16b and two X-ray sources 15a and 15b opposite to the detectors 16a and 16b. A patient support device or patient table 3 is located in front of the scanner 9. Its upper part 2, along with the patient O positioned on it, can be moved to the scanner 9 so that the patient O can move relative to the detector system 16a and 16b through the measurement chamber 12. The scanner 9 and patient table 3 are controlled by a control device 31, from which control signals AS are acquired via a standard control interface 34 to control the entire system in a conventional manner according to a prescribed measurement protocol. In the case of helical acquisition, a helical path is generated by the movement of the patient O along the z-direction—corresponding to the system axis z that longitudinally passes through the measurement space 12—while simultaneously the X-ray sources 15a and 15b rotate relative to the patient O during measurement. Here, detectors 16a and 16b always operate together in parallel with X-ray sources 15a and 15b to detect projection measurement data PMD1 and PMD2, which are then used to reconstruct stereo and / or slice image data. Similarly, a sequential measurement method can be performed, in which a fixed position is approximated in the z-direction, and then, during one, partial, or several rotations, the desired projection measurement data PMD1 and PMD2 are detected at the relevant z-position to reconstruct a cross-sectional image at that z-position, or to reconstruct image data from projection measurement data at several z-positions. In principle, the method according to the invention can also be used in other CT systems, such as those with only one X-ray source or with detectors forming a complete ring. For example, the method according to the invention can also be applied to systems with a stationary patient table and a gantry that moves in the z-direction (so-called a sliding gantry).

[0061] The projection measurement data PMD1 and PMD2 (hereinafter also referred to as raw data) acquired by detectors 16a and 16b are transmitted to the control device 31 via the raw data interface 33. Then, optionally after appropriate preprocessing, this raw data is further processed in a reconstruction device 50, which in this embodiment is implemented in software on a processor within the control device 31. The reconstruction device 50 reconstructs two image datasets BD1 and BD2 based on the raw data PMD1 and PMD2, wherein the first image dataset BD1 shows the vascular structure to which the contrast agent K according to the invention has been applied, and the second image dataset BD2 shows the bone structure within the blood vessel and areas of calcification or partial calcification.

[0062] The exact structure of this reconfiguration device 50 is as follows: Figure 5 This is shown in detail in the text.

[0063] The image data BD1 and BD2 generated by the reconstruction device 50 are then stored in the memory 32 of the control device 31 and / or output to the screen of the control device 31 in a normal manner. They can also be transmitted via... Figure 6 An interface, not shown, feeds into a network connected to the computed tomography system 60, for example, into a radiographic information system (RIS), and stores it in a large-capacity memory accessible there, or outputs it as an image to a printer or projection station connected there. This data can then be further processed in any way, and then stored or output.

[0064] Figure 6 The diagram also shows a contrast agent injection device 35, which is used to inject contrast agent K into the patient O in advance, i.e., before the start of the CT imaging method. The area penetrated by contrast agent K, as well as the bone structure and (partially) calcified areas, can then be detected in image form using a computed tomography system 60 and the X-ray imaging method according to the invention.

[0065] The components of the reconfiguration device 50 can be implemented primarily or entirely as software modules on a suitable processor. In particular, the interfaces between these components can also be designed purely in software. All that is required is access to suitable storage areas where data can be appropriately stored and retrieved and updated at any time.

[0066] Finally, it should be reiterated that the above-described methods and apparatus are merely preferred embodiments of the present invention, and those skilled in the art can modify the invention without departing from the scope defined by the claims. For completeness, it should also be noted that the use of the indefinite article "a" or "an" does not preclude the existence of multiple related features. Similarly, the term "unit" does not preclude it from being composed of several components, which may be spatially distributed if desired.

Claims

1. An X-ray contrast agent (K) for displaying blood vessels permeated by the X-ray contrast agent (K), comprising at least one material, wherein the variation of the mass absorption coefficient representing the X-ray absorption of the at least one material between at least two different X-ray photon energies (E(1), E(2)) is significantly different from the variation of the mass absorption coefficient representing the X-ray absorption of calcium between the at least two different X-ray photon energies (E(1), E(2)).

2. The X-ray contrast agent according to claim 1, wherein, For the at least two X-ray photon energies (E(1), E(2)), there is no significant difference in X-ray absorption.

3. The X-ray contrast agent according to claim 1 or 2, wherein, The X-ray absorption spectrum of the X-ray contrast agent (K) is similar to that of water or soft tissue.

4. The X-ray contrast agent according to claim 1 or 2, comprising one of the following materials: Tungsten; Tantalum; hafnium; gold.

5. An X-ray imaging method for displaying blood vessels permeated by an X-ray contrast agent (K), comprising the following steps: Choose one of the X-ray contrast agents (K) according to any one of claims 1 to 4. A multi-energy recording method is used to detect raw X-ray data (RD) from an area of ​​an object (O) that has been penetrated by the X-ray contrast agent (K). Material decomposition of the X-ray contrast agent (K) and calcium was performed based on the raw X-ray data (RD). At least two image datasets (BD1, BD2) are reconstructed based on the material decomposition, and the image datasets include: A first image dataset (BD1), the first image dataset representing a first image region to which the X-ray contrast agent (K) has been applied, A second image dataset (BD2) represents a second image region that is complementary to the first image region.

6. The X-ray imaging method according to claim 5, comprising a multi-energy imaging method, including the following steps: Specify at least two different X-ray tube voltages (V) T ),in, The changes in absorption of the X-ray contrast agent (K) were significantly different from those of calcium; The X-ray image recording is performed using at least two datasets to obtain a first raw dataset (PMD1) and at least one second raw dataset (PMD2), wherein the X-ray image recording is performed using at least two different X-ray tube voltages (V). T Recorded; The material decomposition is performed based on the first original dataset (PMD1) and the second original dataset (PMD2).

7. The X-ray imaging method according to claim 5, comprising the following steps: Energy-resolved detection of raw X-ray data (RD) is performed using a photon-counting detector, wherein an energy threshold is defined for the photon-counting detector such that, at the energy threshold, the change in X-ray absorption of the X-ray contrast agent (K) is significantly different from the change in X-ray absorption of calcium. The material is decomposed based on the energy-resolved raw X-ray data (RD).

8. The X-ray imaging method according to any one of claims 5 to 7, including a CT angiography method.

9. An image reconstruction apparatus (50), comprising: A determining unit (51) is used to determine at least two different X-ray photon energies (E(1), E(2)), wherein an X-ray contrast agent (K) according to any one of claims 1 to 4 is significantly different from the variation of calcium X-ray absorption between the at least two different X-ray photon energies (E(1), E(2)). A raw data receiving unit (52) is used to receive raw X-ray data (RD) from an area of ​​an object under examination (O) that is at least partially permeated by the X-ray contrast agent (K) by means of a multi-energy recording method. A decomposition unit (53) is used to decompose the X-ray contrast agent (K) and calcium based on the raw X-ray data (RD). A reconstruction unit (54) is used to reconstruct at least two image datasets (BD1, BD2) based on the material decomposition, the image datasets comprising: A first image dataset (BD1), the first image dataset representing a first image region to which the X-ray contrast agent (K) has been applied; A second image dataset (BD2) represents a second image region that is complementary to the first image region.

10. An X-ray imaging system (60) having an image reconstruction device (50) according to claim 9.

11. The X-ray imaging system according to claim 10, comprising a CT vascular contrast device.

12. A computer program product comprising: a computer program that can be directly loaded into a storage device of an X-ray imaging system (60); and a plurality of program segments for performing all steps of the method according to any one of claims 5 to 8 when the computer program in the X-ray imaging system (60) is executed.

13. A computer-readable medium having stored thereon a plurality of program segments that can be read and executed by a computer unit, so as to perform all the steps of the method according to any one of claims 5 to 8 when the program segments are executed by the computer unit.

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