SIMULTANEOUS IMAGE REPRESENTATION OF TWO DIFFERENT FUNCTIONAL AREAS

Abstract

An ensemble of at least two X-ray contrast agents includes X-ray contrast agent and a second X-ray contrast agent. The second X-ray contrast agent has an X-ray absorption whose change between at least two different X-ray photon energies differs significantly from the change of the X-ray absorption of the first X-ray contrast agent between the at least two different X-ray photon energies. An X-ray imaging method, an image reconstruction device, an X-ray imaging system are also disclosed.

Claims

1. An X-ray imaging system including an ensemble of at least two X-ray contrast agents, the ensemble comprising: a first X-ray contrast agent having a first X-ray absorption; and a second X-ray contrast agent having a second X-ray absorption, a change of the second X-ray absorption between at least two different X-ray photon energies differing significantly from a change in the first X-ray absorption between the at least two different X-ray photon energies.

2. The X-ray imaging system of claim 1, wherein the first X-ray absorption of the first X-ray contrast agent for the at least two different X-ray photon energies is significantly different, and the second X-ray absorption of the second X-ray contrast agent for the at least two different X-ray photon energies is not significantly different.

3. The X-ray imaging system of claim 2, wherein a spectrum of the second X-ray absorption of the second X-ray contrast agent is similar to a spectrum of an X-ray absorption of water or soft tissue.

4. The X-ray imaging system of claim 1, wherein the first X-ray contrast agent includes iodine, or gadolinium; and the second X-ray contrast agent includes tungsten, tantalum, hafnium, or gold.

5. An X-ray imaging method, comprising: selecting an ensemble of X-ray contrast agents, the ensemble including a first X-ray contrast agent having a first X-ray absorption, and a second X-ray contrast agent having a second X-ray absorption a change of the second X-ray absorption between at least two different X-ray photon energies differing significantly from a change in the first X-ray absorption between the at least two different X-ray photon energies, capturing, with the aid of a multi-energy recording method, X-ray raw data from a region of an examination object which is flooded by the first X-ray contrast agent and from a region of the examination object which is flooded by the second X-ray contrast agent, carrying out a material decomposition based on the X-ray raw data in relation to the first X-ray contrast agent and the second X-ray contrast agent, and reconstructing at least two image datasets based on the material decomposition, the at least two image datasets including a first image dataset representing first image region affected by the first X-ray contrast agent, and; a second image dataset representing a second image region affected by the second X-ray contrast agent.

6. The X-ray imaging method as claimed in claim 5, wherein the multi-energy recording method comprises: specifying at least two different X-ray tube voltages at which a change in the first X-ray absorption of the first X-ray contrast agent and the second X-ray absorption of the second X-ray contrast agent differs significantly, capturing at least two datasets of X-ray image recordings with the at least two different X-ray tube voltages for acquisition of a first raw dataset and at least one second raw dataset, and carrying out the material decomposition based on the first raw dataset and the at least one second raw dataset.

7. The X-ray imaging method as claimed in claim 5, wherein the capturing of the X-ray raw data takes place by way of an energy-resolved capture of X-ray raw data with the aid of a photon-counting detector, energy thresholds of the photon-counting detector being set such that the change in the first X-ray absorption of the first X-ray contrast agent differs significantly from the change in the second X-ray absorption of the second X-ray contrast agent, and the material decomposition is based on energy-resolved raw data.

8. The X-ray imaging method as claimed in claim 5, wherein the X-ray imaging method is one of the following CT imaging methods a simultaneous representation of an embolic agent and a local blood flow during a chemoembolization, a simultaneous representation of a venous or portal venous phase and an arterial phase of a liver, or a simultaneous representation of a local blood flow of a lung parenchyma and a lung ventilation.

9. An image reconstruction facility, comprising: an establishing unit to ascertain at least two different X-ray photon energies at which a first X-ray contrast agent differs significantly from a second X-ray contrast agent with regard to a change in an X-ray absorption between the at least two different X-ray photon energies, a raw data receiving unit to receive X-ray raw data from a region of an examination object which is flooded by the first X-ray contrast agent and from a region of the examination object which is flooded by the second X-ray contrast agent, with the aid of a multi-energy recording method, a decomposition unit to carry out a material decomposition based on the X-ray raw data in relation to the first X-ray contrast agent and the second X-ray contrast agent, a reconstruction unit to recontruct at least two image datasets based on the material decomposition, the at least two image datasets including a first image dataset to represeting a first image region affected by the first X-ray contrast agent, and a second image dataset representing a second image region affected by the second X-ray contrast agent.

10. An X-ray imaging system, having an image reconstruction facility as claimed in claim 9.

11. The X-ray imaging system as claimed in claim 10, having a CT imaging facility.

12. A non-transitory program product including a computer program directly loadable into a storage facility of an X-ray imaging system, the non-transitory computer program product having program portions configured to cause the X-ray imaging system to carry out the method of claim 5 when the computer program is executed in the X-ray imaging system.

13. A non-transitory computer-readable medium storing program portions that, when executed by a computer unit, cause the computer unit to carry out the method as claimed in claim 5.

14. The X-ray imaging method of claim 5, wherein the multi-energy recording method is a dual-energy recording method.

15. The X-ray imaging method of claim 6, wherein the multi-energy recording method is a dual-energy recording method.

16. The X-ray imaging system of claim 2, wherein the first X-ray contrast agent includes iodine, or gadolinium; and the second X-ray contrast agent includes tungsten, tantalum, hafnium, or gold.

17. The X-ray imaging system of claim 3, wherein the first X-ray contrast agent includes iodine, or gadolinium; and the second X-ray contrast agent includes tungsten, tantalum, hafnium, or gold.

18. The X-ray imaging method as claimed in claim 6, wherein the X-ray imaging method is one of the following CT imaging methods a simultaneous representation of an embolic agent and a local blood flow during a chemoembolization, a simultaneous representation of a venous or portal venous phase and an arterial phase of a liver, or a simultaneous representation of a local blood flow of a lung parenchyma and a lung ventilation.

19. The X-ray imaging method as claimed in claim 7, wherein the X-ray imaging method is one of the following CT imaging methods a simultaneous representation of an embolic agent and a local blood flow during a chemoembolization, a simultaneous representation of a venous or portal venous phase and an arterial phase of a liver, or a simultaneous representation of a local blood flow of a lung parenchyma and a lung ventilation.

20. The image reconstruction facility of claim 9, wherein the multi-energy recording method is a dual-energy recording method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The present invention will now be described again in greater detail using example embodiments, making reference to the accompanying figures, in which:

[0057] FIG. 1 shows a graphical representation that illustrates absorption values of the contrast agent iodine and the material tungsten dependent upon the tube voltage of an X-ray facility,

[0058] FIG. 2 shows a graphical representation that represents the absorption properties of the contrast agents iodine and tungsten and of calcium and water dependent upon the energy of the X-ray photons,

[0059] FIG. 3 shows a flow diagram that illustrates an X-ray imaging method according to a first example embodiment of the present invention,

[0060] FIG. 4 shows a schematic representation of an image reconstruction facility according to an example embodiment of the present invention,

[0061] FIG. 5 shows a schematic representation of a CT system according to an example embodiment of the present invention.

DETAILED DESCRIPTION

[0062] FIG. 1 shows a graphical representation 10 that illustrates absorption values Is of the contrast agent iodine I and the material tungsten W dependent upon the tube voltage VT of an X-ray facility. Whereas the X-ray absorption of iodine I decreases with increasing energy, the X-ray absorption of tungsten W decreases only slightly with increasing energy. Particularly in a dual-energy image recording at a low energy of 80 kV and a higher energy of 140 kV or 150 kV with a tin filter, the X-ray absorption Is of tungsten W changes practically not at all as compared with the X-ray absorption of iodine I. Therefore, image points at which the two individual recordings are generated with different tube voltages can easily be associated with one of the two contrast agents. For example, a point at which the absorption is the same in the two images is clearly attributable to the material tungsten W and a point at which the absorption in the two images is strongly different is clearly attributable to the material iodine I.

[0063] FIG. 2 shows a graphical representation 20 that illustrates absorption properties of the contrast agents iodine I and tungsten W as well as those of calcium Ca and water H2O, dependent upon the energy EPH of the X-ray photons. For each of the materials mentioned, the mass absorption coefficient K is shown dependent upon the energy EPH of the X-ray photons. It is clearly apparent in FIG. 2 that the absorption of the contrast agent iodine I and of the bone material calcium Ca decreases strongly in the region from 40 to 80 keV with increasing photon energy EPH. It should be noted that therein the absorption is shown logarithmically. In contrast thereto, tungsten W behaves more like water H2O. That is, the absorption for a first photon energy E(1), which is at approximately 45 keV, is equal to the absorption at a second photon energy E(2) which is at approximately 80 keV. Due to the strongly differing behavior of tungsten W as compared with calcium Ca, image regions which are laden with tungsten W can readily be separated or separately represented from regions in which calcium Ca prevails.

[0064] FIG. 3 shows a flow diagram 300 which illustrates an X-ray imaging method according to an example embodiment of the present invention. In the example embodiment according to FIG. 3, an imaging of a chemoembolization of a tumor in the liver is to be carried out.

[0065] For this purpose, an ensemble of two contrast agents is selected in step 3.I, specifically the iodine-based Lipiodol and an intravenous contrast agent based upon the element tungsten.

[0066] Furthermore, in the step 3.II, X-ray raw data RD is captured from a region affected by Lipiodol, i.e. the edge region of the tumor and a region flooded with the intravenous contrast agent, with the aid of a dual-energy recording method. In the method visualized in FIG. 3, X-ray raw data that has been recorded with X-ray radiation at two different energy values E(1) and E(2) is captured. The energy values are therein selected such that the absorption behavior of the intravenous contrast agent, based in this example embodiment upon the material tungsten, is the same for both the energy values.

[0067] The image recording process can be realized, for example, by way of the use of two detectors arranged spatially separated from one another, wherein a filter is introduced into the beam path in front of one of the two detectors, said filter filtering out part of the spectrum of the X-rays. Therefore, two raw datasets are captured with different X-ray photon spectra.

[0068] In step 3.III, a reconstruction of two image datasets BD1, BD2 takes place on the basis of the two raw datasets.

[0069] The reconstruction takes place on the basis of a material decomposition according to the two contrast agents used.

[0070] A first image dataset BD1 represents a first image region affected by the Lipiodol and a second image dataset BD2 represents a second image region affected by the tungsten-based contrast agent. The two image regions are easily distinguishable from one another in a common image representation due to the strongly different properties of the contrast agents used.

[0071] FIG. 4 shows a reconstruction facility 40. The reconstruction facility 40 has an establishing unit 41. The establishing unit 41 receives information regarding the contrast agents I, K2 to be used and establishes values E(1), E(2) of two different X-ray photon energies at which a selected contrast agent K2 behaves like water, i.e. the absorption is the same for both energy values. However, the image regions affected by iodine I that are to be separated from the contrast agent K2 have a dependence of the absorption on the X-ray photon energy and, due to the different absorption behavior, can therefore easily be differentiated at the established energy values E(1), E(2) from the selected contrast agent K2. The selection of the energy values can take place, for example, on the basis of stored energy-dependent absorption values of the selected contrast agent K2. The selection of the energy values E(1), E(2) can be taken into account, in the context of a multi-energy recording method, in the selection of the energy of the X-ray sources used for imaging. If counting detectors are used for capturing the X-ray radiation, then energy thresholds and/or intervals can be selected so that the energy values mentioned are included.

[0072] The reconstruction facility 40 also has a raw data receiving unit 42 for receiving X-ray raw data RD. The raw data RD has been acquired with the aid of a dual-energy CT method from a region of an examination object which is at least partially flooded by the contrast agents I, K2.

[0073] The raw data RD is passed on to a decomposition unit 43 which carries out a material decomposition on the basis of the X-ray raw data RD in relation to the contrast agents I, K2. The portions MA1, MA2 which are associated with the individual absorption spectra of the different materials are transferred to a reconstruction unit 44 which reconstructs at least two image datasets BD1, BD2 on the basis of the material-specific portions MA1, MA2. A first image dataset BD1 visualizes a first image region affected by the tungsten-based contrast agent K2 and a second image dataset BD2 visualizes a second image region which is complementary to the first image region, and in which structures contrasted with iodine prevail. The image data BD1, BD2 are finally output via an output interface 45.

[0074] FIG. 5 visualizes an X-ray imaging system, in this case a CT system 50, according to an example embodiment of the present invention.

[0075] The CT system 50 which is configured as a dual-energy CT system, substantially consists therein of a typical scanner 9 in which a projection measurement data acquisition unit 5 with two detectors 16a, 16b and two X-ray sources 15a, 15b arranged opposite the two detectors 16a, 16b circulates on a gantry 11 around a scanning space 12. Situated in front of the scanner 9 is a patient positioning apparatus 3 and/or a patient table 3, the upper part 2 of which can be displaced with a patient o situated thereon toward the scanner 9, in order to move the patient o through the scanning space 12 relative to the detector system 16a, 16b. The scanner 9 and the patient table 3 are controlled by way of a control facility 31 from which acquisition control signals AS come via a conventional control interface 34 in order to control the whole system according to predetermined scan protocols in the conventional manner. In the case of a spiral acquisition, by way of a movement of the patient o along the z-direction which corresponds to the system axis z through the scanning space 12 and the simultaneous circulation of the X-ray sources 15a, 15b, for the X-ray sources 15a, 15b relative to the patient o during the scan, a helical path results. The detectors 16a, 16b therein always move in parallel opposite to and with the X-ray sources 15a, 15b, in order to capture projection measurement data PMD1, PMD2 which is then used for the reconstruction of volume and/or slice image data. Similarly, a sequential scanning method can also be carried out in which a fixed position in the z-direction is moved to and then, during a circulation, a partial circulation or a plurality of circulations at the z-position in question, the required projection measurement data PMD1, PMD2 is captured, in order to reconstruct a slice image at this z-position or to reconstruct image data from the projection measurement data of a plurality of z-positions. The method according to embodiments of the present invention is also in principle usable with other CT systems, for example, with just one X-ray source or with a detector forming a complete ring. For example, the inventive method can also be used on a system with an unmoved patient table and a gantry moved in the z-direction (a so-called sliding gantry).

[0076] The projection measurement data PMD1, PMD2 (also referred to here as raw data) acquired from the detectors 16a, 16b is transferred via a raw data interface 33 to the control facility 31. This raw data is then further processed, possibly after a suitable pre-processing in a reconstruction facility 40 which, in this example embodiment, is realized in the control facility 31 in the form of software on a processor. This reconstruction facility 40 reconstructs, on the basis of the raw data PMD1, PMD2, two image datasets BD1, BD2, of which a first image dataset BD1 represents structures affected by a first X-ray contrast agent according to embodiments of the present invention, for example a tungsten-based contrast agent, and a second image dataset BD2 represents image regions affected by a second contrast agent according to embodiments of the present invention, for example iodine.

[0077] The precise construction of such a reconstruction facility 40 is illustrated in detail in FIG. 4.

[0078] The image data BD1, BD2 generated by the reconstruction facility 40 is then stored in a memory store 32 of the control facility 31 and/or is output in the usual manner on the screen of the control facility 31. Via an interface (not shown in FIG. 5), it can also be fed into a network connected to the computed tomography system 50, for example, a radiological information system (RIS), and stored in a mass memory store accessible there or output as images to printers or filming stations connected there. The data can thus be further processed in any desired manner and then stored or output.

[0079] In addition in FIG. 5, a contrast agent injection facility 35 is shown, with which the two contrast agents according to embodiments of the present invention are injected into the patient o in advance, that is, before the start of the CT imaging process. The regions which are flooded by the contrast agents can then be captured in image form with the aid of the computed tomography system 50 using the X-ray imaging method according to embodiments of the present invention.

[0080] The components of the reconstruction facility 40 can be realized mainly or entirely in the form of software elements on a suitable processor. In particular, the interfaces between these components can also be configured purely as software. It is required only that access possibilities exist in suitable memory storage regions in which the data can suitably be placed in intermediate storage and, at any time, called up again and updated.

[0081] Finally, it should again be noted that the methods and apparatuses described above are merely preferred example embodiments of the present invention and that the present invention can be modified by a person skilled in the art without departing from the field of embodiments of the present invention, to the extent that it is specified by the claims. For the sake of completeness, it should also be noted that the use of the indefinite article “a” or “an” does not preclude the relevant features from being present plurally. Similarly, the expression “unit” does not preclude this consisting of a plurality of components which can possibly also be spatially distributed.