Radiation compensation for medical imaging equipment

Abstract

The present invention relates to a method for operating a medical imaging device (1), comprising: generating primary X-ray radiation (6) through a first radiation source (2) of the medical device (1); irradiating an object (9) with the primary X-ray radiation; first acquiring the intensity distribution (17) of the X-ray radiation through a first X-ray detector (3); second acquiring the scattered radiation distribution (14) of the scattered radiation (11) generated on the object through a second X-ray detector (5); estimating the spatial distribution (15) of a portion of the scattered radiation acquired by the first X-ray detector based on the acquired scattered radiation distribution by a computing device (13); and determining the intensity distribution (18) of a portion (10) of the transmitted primary X-ray radiation acquired by the first X-ray detector from the intensity distribution acquired by the first X-ray detector based on the estimated spatial distribution, so as to improve the quality of the image or image data of the medical imaging device (1).

Description

Technical Field

[0001] This invention relates to a method for operating a medical imaging apparatus, comprising: generating primary X-ray radiation through a first radiation source of the medical apparatus; irradiating a subject with the primary X-ray radiation; and first acquiring an intensity distribution of the X-ray radiation through a first X-ray detector associated with the first radiation source of the medical apparatus, wherein the acquired intensity distribution is determined by a portion of the primary X-ray radiation transmitted through the subject and scattered radiation resulting from scattering of the primary X-ray radiation on the subject. The invention also relates to a medical imaging apparatus suitable for performing said method. Background Technology

[0002] In X-ray imaging, scattered radiation has a significant impact on image quality. During the process of creating an X-ray record of an object, when the object is irradiated, the primary X-ray radiation emitted from the radiation source and confined within the object, for example by a collimator in a spatially limited sense, is not only partially absorbed but also scattered, forming scattered radiation. This is explained in detail, for example, in H. Barrett and W. Swindell's *Biological Imaging: The Theory of Image Formation, Detection and Processing – Volume 1*, Academic Press, 1996. In medical imaging, particularly X-ray diagnostics, two interactions occur with the object, i.e., for example, a patient's organ, which lead to the formation of scattered radiation. One is typical elastic Rayleigh scattering, and the other is inelastic Compton scattering. In principle, each type of scattered radiation degrades the quality of the X-ray record due to reduced contrast and increased image noise, thereby also degrading the quality of the image reconstructed from the X-ray record. Here, in particular, the introduction of large-area X-ray detectors and the associated increase in the corresponding cone beam angle for primary radiation, which can be set by the corresponding collimator, have led to a significant amplification of stray beam problems in radiographic imaging, C-arm imaging, and computed tomography, because the scattered radiation portion increases significantly with the size of the irradiated object, such as the pelvis, and with the detector spatial angle, i.e., the size of the spatial angle at which the X-ray detector detects X-ray radiation.

[0003] The contrast reduction mentioned here plays a particularly important role in 3D imaging, such as in the reconstruction of three-dimensional images of an irradiated object in computed tomography (CT) or C-arm CT. In 3D imaging, projected images are recorded from different directions, the so-called projection directions, and 3D image data sets are obtained from them to reconstruct the 3D image. In addition to contrast reduction, scattered radiation here also causes other artifacts, such as amplified noise, strong low-frequency gray-level distortion, the so-called cupping or capping artifacts, and linear or shadow artifacts in the reconstructed 3D image. J. Siewerdsen and D. Jaffray’s 2001 article “Cone-beam computedtomography with a flat-panel imager: Magnitude and effects of x-ray scatter” in Medical Physics 28(2) pp. 220-231 provides a detailed study of scattered radiation in C-arm CT systems and its effects on image quality.

[0004] Correspondingly, within the scope of medical imaging, it is desirable to reduce or correct or compensate for the impact of scattered radiation on 2D or 3D images. Here, we distinguish between hardware-based and software-based solutions.

[0005] For example, a so-called anti-scattering grid installed in front of an X-ray detector, that is, in front of the detector unit of the X-ray detector, is a hardware-based solution. Here, the walls of the anti-scattering grid are aligned with the associated radiation source. Increasing the distance between the irradiated object and the X-ray detector (if feasible) can also contribute to reducing scattered radiation. The purpose of a hardware-based solution is generally to physically suppress scattered radiation before it reaches the X-ray detector.

[0006] Conversely, software-based approaches are generally used to reduce residual scattered radiation, that is, to reduce the portion of scattered radiation that was not eliminated by hardware-based methods. This residual or remaining portion of scattered radiation, as acquired by an X-ray detector, may still be greater than the transmitted portion of the primary radiation in the signal generated by the X-ray detector. Correspondingly, the purpose of software-based approaches is to post-process the X-ray radiation acquired by the X-ray detector, which includes not only the primary radiation portion but also the scattered radiation or the X-ray radiation formed therefrom, or its distribution.

[0007] Here, the software-based approach typically includes two components: a method for estimating the spatial distribution of scattered radiation on the X-ray detector and thus in the measured projection image, and, in the simplest case, a correction or compensation algorithm for subtracting the estimated scattered radiation distribution from the measured X-ray radiation distribution on the X-ray detector or the measured projection data.

[0008] In the articles “A general framework and review of scatter correction methods in x-ray cone-beam computerized tomography, Part 1: Scatter compensation approaches” by E.-Peter Rührnschopf and K. Klingenbeck in Medical Physics 38(7), 2011, pp. 4296-4311 and “A general framework and review of scatter correction methods in cone-beam computerized tomography, Part 2: Scatter estimation approaches” in Medical Physics 38(9), 2011, pp. 5186-5199, an overview of methods for measuring or estimating and correcting or compensating for scattered radiation is given. It is noteworthy that only a relatively small number of these methods are based on actual measurements of scattered radiation. Instead, most of these schemes are based on estimations of scattered radiation using mathematical models. This is because the measurement of scattered radiation is highly complex and affects the acquisition of X-ray radiation by the X-ray detector and thus the actual image recording.

[0009] To measure scattered radiation, one approach involves introducing additional hardware or objects between the radiation source or X-ray source and the irradiated or measured object. For example, the additional object could be a radiation absorption grid and / or a modulation grid and / or the like. This approach has the following disadvantages: it necessitates additional recording, thereby increasing the corresponding radiation dose to the patient; it introduces artifacts in the acquired X-ray radiation, and thus in the acquired two-dimensional or reconstructed three-dimensional images; and it requires additional mechanical overhead for practical implementation, namely, the introduction and removal of a corresponding reference object.

[0010] On the other hand, there is a scheme using a collimator integrated into the medical device. Here, the collimator shields a pre-defined area of ​​the X-ray detector from primary radiation so that scattered radiation can be measured there, i.e., in the collimator's shadow, and the scattered radiation can be estimated for the rest of the X-ray detector. The estimation or assessment of the scattered radiation distribution in the field of view, i.e., the area of ​​the X-ray detector not shielded by the collimator, is then performed, for example, by model estimation, based on image data measured at the edges of the X-ray detector obtained in the collimator's shadow. This is described, for example, in J. Siewerdsen et al.'s article "A simple, direct method for x-ray scatter estimation and correction in digital radiography and cone-beam computerized tomography" in Medical Physics 33(1), 2006, pp. 187-197.

[0011] The drawback is that multiple detector rows and / or columns at the detector edges are occupied by scattered radiation measurements, which reduces the maximum possible field of view size. Furthermore, it is problematic how robust a model-based estimate of the scattered radiation distribution in the field of view—that is, the region of the primary radiation portion of the X-ray detector's collected X-ray radiation—can be when only a few detector rows or columns, i.e., a very small area compared to the size of the scattered radiation region to be estimated, are provided as the data basis for the estimation. Summary of the Invention

[0012] The technical problem to be solved by the present invention is to improve the quality of images or image data of medical imaging equipment, especially to provide improved scattered radiation compensation for medical imaging equipment.

[0013] The aforementioned technical problems are solved by the subject matter of this invention. Advantageous embodiments are obtained from the specification and drawings.

[0014] This invention relates to a method for operating a medical imaging device, such as an X-ray device or a computed tomography (CT) device, comprising a series of method steps. In particular, the device may be a C-arm device. Here, the first method step is to generate primary X-ray radiation through a first radiation source of the medical device. Here, the primary X-ray radiation can be spatially confined or constrained by a collimator according to the pinhole principle, thereby matching the size of a first X-ray detector associated with the first radiation source in its spatial extension. Another method step is to irradiate an object, particularly a patient and / or a part of the patient's body, with the primary X-ray radiation. A subsequent method step is to first acquire the (first) intensity distribution of the X-ray radiation using the first X-ray detector associated with the first radiation source of the medical device. Here, the first X-ray detector may have a matrix of detector units arranged in multiple columns and rows. The acquired X-ray radiation here includes a portion of primary X-ray radiation transmitted through the object, i.e., not absorbed by the object, and a portion of scattered radiation generated by the scattering of the primary X-ray radiation on the object, thereby being specifically determined by the primary radiation portion and the scattered radiation portion. Thus, the first X-ray detector acquires a total of the scattered radiation and additionally the transmitted portion of the primary X-ray radiation.

[0015] Importantly, as another methodological step, a second acquisition is performed using a second X-ray detector of the medical device to obtain the distribution of scattered radiation generated on the object, as a second intensity distribution. This can be achieved using a collimator, allowing the second X-ray detector to acquire only the scattered radiation, excluding the portion of the primary X-ray radiation from the first radiation source. The second X-ray detector can also have a matrix of detector units arranged in multiple columns and rows. Thus, the first X-ray detector acquires both the primary X-ray radiation portion and the scattered radiation portion, while the second detector acquires only the scattered radiation portion. Acquiring the scattered radiation distribution using the second X-ray detector specifically includes acquiring the spatial distribution of the scattered radiation on the second X-ray detector. This can be configured such that the second X-ray detector is positioned in multiple different locations relative to a predetermined position, i.e., a predetermined location and / or a predetermined orientation, of the first X-ray detector. The first and second acquisitions are not necessarily performed sequentially, but can also be performed simultaneously.

[0016] Subsequently, as a methodological step, the spatial distribution of a portion of the scattered radiation acquired by the first X-ray detector is estimated using the computing device of the medical device, based on the scattered radiation distribution acquired by the second X-ray detector. This can be estimated, for example, using a suitable mathematical model, such as a square model or a polygonal model, i.e., a so-called spline model. In the mathematical model, for example, the geometric positions of the two X-ray detectors relative to each other, i.e., their relative positions and / or relative orientations, can also be considered.

[0017] Then, another method step is to determine, using a computing device, the (second) intensity distribution of the portion of the transmitted primary X-ray radiation acquired by the first X-ray detector, from the (first) intensity distribution acquired in total by the first X-ray detector, based on the spatial distribution estimated for the scattered radiation on the first X-ray detector. This can be done, for example, by subtracting the estimated or assumed scattered radiation distribution from the total acquired (first) intensity distribution, or by compensating for the scattered radiation in the total acquired (first) intensity distribution using other known methods. Here, the relative spatial position and orientation of the two X-ray detectors relative to each other are predetermined and known. In particular, 2D image preprocessing (which can also be referred to as 2D image reconstruction within the scope of this document) or 3D image reconstruction of the object can also be performed based on the determined second intensity distribution of the transmitted primary X-ray radiation. In the case of a 2D image, the (first) intensity distribution of the total acquired X-ray radiation already corresponds to a 2D record, which can then be compensated for for scattered radiation during reconstruction.

[0018] In other words, the described method provides a scheme for scattered radiation correction based on actual measurements of scattered radiation using a second X-ray detector, different from the first X-ray detector. Therefore, the method is primarily geared towards, for example, C-arm systems with two image planes, i.e., so-called dual-plane systems with two detector planes. Here, a second X-ray detector, for example, already present in a dual-plane system, is used to measure the scattered radiation distribution. Based on this measured scattered radiation distribution, improved scattered radiation compensation can be performed on the (first) intensity distribution acquired by the first X-ray detector compared to conventional methods. This method can be used not only in 2D imaging but also in 3D imaging. Here, the entire detector region of the first X-ray detector, i.e., all detector elements of the first X-ray detector, can be used to generate 2D or 3D images. Additionally, large-area measurements of scattered radiation in the second X-ray detector, for example, the entire detector region of the second X-ray detector, enable a more robust and accurate estimation of the scattered radiation distribution on the first X-ray detector, i.e., the spatial distribution of scattered radiation acquired by the first X-ray detector.

[0019] In an advantageous embodiment, the matrix of detector elements of the first X-ray detector is arranged substantially, particularly entirely, within the beam cone of the X-ray radiation from the first radiation source, while the matrix of detector elements of the second X-ray detector is arranged entirely outside the beam cone of the X-ray radiation from the first radiation source. The corresponding matrix here specifically includes all detector elements of the respective X-ray detector. The beam cone can be predetermined between the first radiation source and the first X-ray detector using the collimator already mentioned.

[0020] This has the following advantages: by detecting only scattered radiation with the second X-ray detector and acquiring X-ray radiation in a particularly large area with the first X-ray detector, the reconstructed image has a correspondingly high quality. Thus, the advantages already mentioned are achieved particularly well and reliably.

[0021] In another advantageous embodiment, the medical device includes or has a dual-plane C-arm system having a first radiation source and an associated first X-ray detector, and a second radiation source associated with a second X-ray detector. In particular, in this method, the second radiation source may be inactive or deactivated.

[0022] This has the following advantages: for example, in 3D imaging that typically uses only one radiation source and one X-ray detector, a second X-ray detector already present in the aforementioned equipment can be used to improve image quality and perform scattered radiation compensation. In 2D imaging, two radiation sources are often not used in dual-plane C-arm systems, so the advantages of improved image quality described can also be achieved here in a simple manner without additional hardware overhead.

[0023] In another advantageous embodiment, two X-ray detectors are arranged rotatably about a common axis of rotation, and in particular, the corresponding normals, extending through the center of the matrix of detector units and relative to the respective main extension planes of the respective X-ray detectors, extend through the axis of rotation. Thus, the X-ray detectors are arranged such that their respective main extension planes are tangent to the cylinders surrounding the axis of rotation. Here, the two X-ray detectors are arranged side-by-side adjacent to each other in the axial direction parallel to the axis of rotation, i.e., along the patient axis, and / or in the azimuth direction, i.e., in the tangential direction perpendicular to the axis of rotation, i.e., on a circular trajectory around the axis of rotation. The tangential direction perpendicular to the axis of rotation can thus be understood as the direction extending tangentially to the circle perpendicular to the axis of rotation (A). In particular, the two X-ray detectors can be arranged adjacent to each other. For example, the X-ray detectors or their housings can be respectively adjacent to each other or have a distance of less than 10 or 5 cm relative to each other.

[0024] This has the following advantages: Firstly, the two X-ray detectors can be arranged relative to each other with different relationships. Therefore, in an arrangement parallel to the axis of rotation, the estimation of the spatial distribution of the scattered radiation from the first X-ray detector based on the scattered radiation collected by the second X-ray detector is mathematically simpler, since the two main extending planes of the X-ray detector preferably extend parallel to each other. In an arrangement perpendicular to the axis of rotation, the following advantages are obtained: especially due to the possible arrangement of an anti-scattering grid on the second X-ray detector, more scattered radiation can be detected by the second X-ray detector. Thus, the statistical information is better, and correspondingly, the estimation of the spatial distribution of the scattered radiation from the first X-ray detector is also better. Because the X-ray detectors are rotatably arranged, the method is also suitable for 3D imaging. Here, the relative geometric positions and orientations of the two X-ray detectors relative to each other are known.

[0025] In a particularly preferred embodiment, the two X-ray detectors are configured to rotate about a rotation axis during the first and second acquisitions, more specifically, by more than 180°. This first and second acquisitions are particularly suitable for the reconstruction of 3D images.

[0026] This has the advantage of being able to produce high-quality 3D images.

[0027] In another advantageous embodiment, when determining the portion of the transmitted primary X-ray radiation acquired by the first X-ray detector, the estimated spatial distribution of the scattered radiation portion in the first X-ray detector is used as a boundary condition for a known scattered radiation correction method. In particular, the estimated spatial distribution can be used as a boundary condition for a known iterative scattered radiation correction method. Preferably, this spatial distribution is used as a boundary condition for initializing and / or adjusting a known scattered radiation correction method.

[0028] This has the following advantages: it can further improve the known, already extensively developed and highly optimized scattered radiation correction methods, because the scattered radiation can be acquired particularly well and the corresponding scattered radiation distribution can be determined particularly accurately via a second X-ray detector with a large detector area.

[0029] In a particularly preferred embodiment, the size and / or location and / or shape and / or material of the irradiated object are estimated based on the distribution of scattered radiation. Thus, for example, it can be estimated whether less scattered radiation is generated on the object, such as the head, or more scattered radiation is generated on the object, such as the abdomen. The size of the object can also be deduced from the amount of scattered radiation.

[0030] This has the advantage that the additional information obtained about the size and / or location and / or shape or material of the object can be used to produce a qualitatively improved image. Therefore, the obtained information can also be used, for example, as boundary conditions for known scattered radiation correction methods, or as boundary conditions for other image processing steps.

[0031] Here, in a particularly preferred embodiment, the image of the object, generated based on the determined portion of the transmitted primary X-ray radiation (i.e., reconstructed or recorded), is truncated based on the estimated size and / or position and / or shape of the object. In particular, in this embodiment of the method, 3D image reconstruction can also be performed based on the truncated correction.

[0032] This has the advantage of reducing truncation artifacts that often occur in 3D reconstruction when introducing objects, such as those that are only partially illuminated or irradiated due to their size. This is particularly advantageous in devices with relatively small X-ray detectors. In particular, this is beneficial for dual-plane devices, which generally have fewer large detectors than other imaging devices in order to improve detector mobility.

[0033] In another advantageous embodiment, a first X-ray detector is configured to have a first anti-scattering grid for reducing the collected scattered radiation, and the estimation of the spatial distribution of the scattered radiation collected by the first X-ray detector, i.e., the portion of the scattered radiation collected by the first X-ray detector, is performed based on the scattered radiation distribution collected by a second X-ray detector, according to a first weighting function, the first weighting function representing the influence of the first anti-scattering grid on the (first) intensity distribution collected in total by the first X-ray detector. In particular, a second X-ray detector without an anti-scattering grid can be implemented here.

[0034] This has the following advantages: on the one hand, the scattered radiation collected by the first X-ray detector is reduced due to the anti-scattering grid; on the other hand, the nonlinear reduction of scattered radiation through the anti-scattering grid on the first X-ray detector can be specifically considered, thereby achieving improved scattered radiation compensation overall.

[0035] In another advantageous embodiment, the estimation of the spatial distribution of scattered radiation acquired by the first X-ray detector is performed based on the scattered radiation distribution acquired by the second X-ray detector according to a second weighting function, which relates to the angle between the main extension planes of the two X-ray detectors and / or the material of the object. In particular, a second X-ray detector with a second anti-scattering grid for reducing the acquired scattered radiation can be implemented, and the second weighting function can also represent the influence of the second anti-scattering grid on the scattered radiation distribution acquired by the second X-ray detector. The second weighting function can here, in particular, relate to the orientation of the anti-scattering grid toward a second radiation source associated with the second X-ray detector.

[0036] This has the advantage of further improving the image quality of the imaging equipment. Therefore, the second weighting function can take into account not only the precise position of the X-ray detectors relative to each other, but also, for example, the correspondingly different scattered radiation distribution and intensity caused by bone or soft tissue. In particular, the orientation towards the second radiation source or an optimized anti-scattering grid further enhances the dependence of the scattered radiation distribution acquired by the second X-ray detector on the relative position of the two X-ray detectors, thus making this consideration particularly advantageous for scattered radiation compensation.

[0037] The present invention also relates to a medical imaging apparatus, particularly an X-ray apparatus and / or a computed tomography apparatus, comprising: a first radiation source for generating primary X-ray radiation and for irradiating an object with the primary X-ray radiation; and a first X-ray detector associated with the first radiation source for (first) acquiring or for first acquiring a (first) intensity distribution of the X-ray radiation, the intensity distribution of the X-ray radiation including a portion of the primary X-ray radiation transmitted through the object and scattered radiation generated by the scattering of the primary X-ray radiation on the object.

[0038] Importantly, the medical device also includes: a second X-ray detector for (second) acquiring or for second acquiring the scattered radiation distribution generated on the object; and a computing device configured to estimate the spatial distribution of a portion of the scattered radiation acquired by the first X-ray detector based on the scattered radiation distribution acquired by the second X-ray detector, and to determine, based on the spatial distribution estimated for the scattered radiation on the first X-ray detector, a portion of the primary X-ray radiation transmitted through the first X-ray detector from the (first) intensity distribution acquired in total by the first X-ray detector.

[0039] This can be configured such that the first X-ray detector has a first housing, and the second X-ray detector has a second housing that is different from the first housing.

[0040] The present invention also relates to a medical imaging device configured to perform the method according to the invention or an advantageous embodiment of the method according to the invention.

[0041] Here, the advantages and advantageous implementations of the medical imaging equipment correspond to the advantages and advantageous implementations of the described method.

[0042] The features and combinations of features mentioned above in the description, as well as those mentioned below in the description of the drawings and / or shown separately in the drawings, can be used not only in the correspondingly given combinations, but also in other combinations, without departing from the scope of the invention. Therefore, it should also be considered that embodiments of the invention not explicitly shown and described in the drawings, but which can be learned from the illustrated embodiments by separate combinations of features, are included and disclosed. It should also be considered that embodiments and combinations of features that do not thus possess all the features of the originally defined invention are disclosed. Attached Figure Description

[0043] Embodiments of the present invention will now be described in detail with reference to the schematic accompanying drawings. Herein:

[0044] Figure 1 An exemplary implementation of a medical imaging device is shown; and

[0045] Figure 2 An exemplary intensity distribution of X-ray radiation acquired by a first X-ray detector and an exemplary distribution of scattered radiation acquired by a second X-ray detector, along with an exemplary estimated spatial distribution of scattered radiation, are shown. Detailed Implementation

[0046] exist Figure 1 A cross-sectional view illustrates an exemplary medical imaging apparatus, here a dual-plane C-arm system. The medical device 1 includes a first radiation source 2, a first X-ray detector 3, and a second radiation source 4 with an associated second X-ray detector 5. The first radiation source 2 generates primary X-ray radiation 6, which is confined by a collimator 7. Another collimator 12 is arranged between the second radiation source 4 and the second X-ray detector 5. The primary radiation propagates through the collimator 7 in a beam cone 8. Here, between the radiation source 2 and the X-ray detector 3, a sub-region of an object 9 is introduced into the beam cone 8, and this sub-region of the object 9 is irradiated by the primary X-ray radiation 6. Here, the portion of the primary X-ray radiation 10 that has passed through the object 9, such as a patient, is collected by the first X-ray detector 3. Furthermore, the primary X-ray radiation 6 also generates scattered radiation 11 in the object 9, a portion of which is also collected by the first X-ray detector 3. Thus, the X-ray detector 3 collects, in total, the transmitted portion of the primary X-ray radiation 10 and a portion of the X-ray radiation 11.

[0047] Scattered radiation 11 is also collected proportionally by a second X-ray detector 5. The second X-ray detector 5 collects only a portion of the scattered radiation 11 here because the second radiation source 4 is deactivated in this method, and the second X-ray detector 5 is arranged outside the beam cone 8.

[0048] Here, the two X-ray detectors 3 and 5, along with their associated radiation sources 2 and 4 and collimators 7 and 12, are arranged to be rotatable about a common axis of rotation A. Here, axis of rotation A also extends perpendicular to the drawing plane. In the example shown, the first and second radiation sources and the first and second X-ray detectors are arranged radially opposite each other about axis of rotation A. The corresponding normals of the principal extension planes of the two X-ray detectors extend correspondingly through axis of rotation A.

[0049] Furthermore, the medical device 1 also includes a computing device 13, which is configured to calculate based on the scattered radiation distribution 14 acquired by the second X-ray detector 5. Figure 2 ) for the first intensity distribution 17 acquired by the first X-ray detector 3 ( Figure 2 Estimate the spatial distribution 15 ( Figure 2 ), and to determine, from the total intensity distribution 17 acquired by the first X-ray detector 3, the portions of the primary X-ray radiation 10 transmitted by the first X-ray detector 3 based on the spatial distribution 15 estimated for the scattered radiation on the first X-ray detector 3.

[0050] exist Figure 2 The diagram illustrates an exemplary, one-dimensional distribution of two X-ray detectors 3 and 5. Here, the distribution of the first and second X-ray detectors 3 and 5 is depicted respectively. Figure 1 The intensity I1 and I2 of the collected X-ray radiation are shown. Here, the left side depicts the intensity I2 of the collected X-ray radiation from the second X-ray detector 5 with respect to the width B2, and the right side depicts the intensity I1 of the X-ray radiation collected by the first X-ray detector 3 with respect to the width B1. In the example shown, for clarity, the intensity I2 is different from that in... Figure 1In the example shown, the corresponding principal extension planes of X-ray detectors 3 and 5 are arranged parallel to each other. Here, the spatial distribution 15 of the scattered radiation 11 collected by the first X-ray detector 3 is estimated mathematically, for example, by using the scattered radiation distribution 14 collected by the second X-ray detector 5. Furthermore, here, a curve 16 having the least square deviation from the collected scattered radiation distribution 14 is placed through the scattered radiation distribution 14 by means of a mathematical model. Here, because the two X-ray detectors 3 and 5 are arranged adjacent to each other, they can be extrapolated with respect to the first detector 3 in a common coordinate model, and the spatial distribution 15 is described there. Thus, by subtracting the spatial distribution 15 from the total intensity distribution 17 collected by the first X-ray detector 3, a portion of the transmitted first primary X-ray radiation 6 collected by the first X-ray detector 3 is determined in the form of a second intensity distribution 18. Thus, the scattered radiation 11 in X-ray imaging is compensated in a particularly effective and accurate manner.

Claims

1. A method for operating a medical imaging device (1), comprising the following steps: - Primary X-ray radiation (6) is generated by the first radiation source (2) of the medical imaging device (1); - Irradiate the object (9) using primary X-ray radiation (6); - The intensity distribution (17) of X-ray radiation is first acquired by the first X-ray detector (3) associated with the first radiation source (2) of the medical imaging device (1), wherein, The intensity distribution (17) collected is determined by a portion (10) of the primary X-ray radiation (6) transmitted through the object and the scattered radiation (11) generated by the scattering of the primary X-ray radiation (6) on the object (9); - A second acquisition is performed on the scattered radiation distribution (14) of the scattered radiation (11) generated on the object (9) by a second X-ray detector (5) different from the first X-ray detector (3) of the medical imaging device (1), the scattered radiation distribution representing the intensity of the scattered radiation acquired over a predetermined width of the second X-ray detector, wherein the second X-ray detector (5) can be positioned in multiple different locations given a predetermined position of the first X-ray detector (3). Its features are, - The computing device (13) of the medical imaging device (1) estimates, based on the scattered radiation distribution (14) acquired by the second X-ray detector (5), a partial spatial distribution (15) of the scattered radiation (11) acquired by the first X-ray detector (3) according to a second weighting function, wherein the second weighting function is related to the angle between the principal extension planes of the first X-ray detector (3) and the second X-ray detector (5), and the partial spatial distribution of the scattered radiation represents the intensity of the scattered radiation acquired over a predetermined width of the first X-ray detector; and - The computing device (13) determines the intensity distribution (18) of a portion (10) of the primary X-ray radiation (6) transmitted by the first X-ray detector (3) from the intensity distribution (17) acquired by the first X-ray detector (3) based on the estimated spatial distribution (15).

2. The method according to claim 1, characterized in that, The matrix of detector units of the first X-ray detector (3) is mostly arranged inside the beam cone (8) of X-ray radiation, and the matrix of detector units of the second X-ray detector (5) is completely arranged outside the beam cone (8) of X-ray radiation.

3. The method according to claim 1, characterized in that, The detector unit matrix of the first X-ray detector (3) is completely arranged inside the beam cone (8) of X-ray radiation, and the detector unit matrix of the second X-ray detector (5) is completely arranged outside the beam cone (8) of X-ray radiation.

4. The method according to claim 1, characterized in that, The medical imaging device (1) includes a dual-plane C-arm system having a first radiation source (2) and an associated first X-ray detector (3) and a second radiation source (4) associated with a second X-ray detector (5).

5. The method according to claim 1, characterized in that, The first X-ray detector (3) and the second X-ray detector (5) are rotatably arranged about a common rotation axis (A), and the corresponding normals of the corresponding main extension planes of the respective X-ray detectors extend through the rotation axis (A), wherein the first X-ray detector (3) and the second X-ray detector (5) are arranged adjacent to each other in a direction parallel to the rotation axis (A) or in a direction extending tangentially to a circle perpendicular to the rotation axis (A).

6. The method according to claim 5, characterized in that, The first X-ray detector (3) and the second X-ray detector (5) rotate around the rotation axis (A) in the first and second acquisitions.

7. The method according to claim 5, characterized in that, The first X-ray detector (3) and the second X-ray detector (5) rotate more than 180° around the rotation axis (A) in the first and second acquisitions.

8. The method according to claim 1, characterized in that, When determining a portion (10) of the primary X-ray radiation (6) transmitted by the first X-ray detector (3), the estimated spatial distribution (15) is used as a boundary condition for a known scattered radiation correction method.

9. The method according to claim 1, characterized in that, When determining a portion (10) of the primary X-ray radiation (6) transmitted by the first X-ray detector (3), the estimated spatial distribution (15) is used as a boundary condition for a known iterative scattered radiation correction method.

10. The method according to claim 1, characterized in that, When determining a portion (10) of the primary X-ray radiation (6) transmitted by the first X-ray detector (3), the estimated spatial distribution (15) is used as a boundary condition for initializing and / or adjusting known scattered radiation correction methods.

11. The method according to claim 1, characterized in that, When determining a portion (10) of the primary X-ray radiation (6) transmitted by the first X-ray detector (3), the estimated spatial distribution (15) is used as a boundary condition for initializing and / or adjusting a known iterative scattered radiation correction method.

12. The method according to claim 1, characterized in that, Estimate the size and / or location and / or shape and / or material of the irradiated object (9) based on the scattered radiation distribution (14).

13. The method according to claim 12, characterized in that, Based on the estimated size and / or position and / or shape of the object, the image of the object (9) generated from the portion (10) of the determined primary X-ray radiation (6) is truncated and corrected.

14. The method according to any one of claims 1 to 13, characterized in that, The first X-ray detector (3) has a first anti-scattering grid, and the estimation of the spatial distribution (15) of the scattered radiation (11) collected by the first X-ray detector (3) is based on the collected scattered radiation distribution (14) according to a first weighting function, which represents the influence of the first anti-scattering grid on the intensity distribution (17) collected by the first X-ray detector (3).

15. The method according to any one of claims 1 to 13, characterized in that, The second weighting function is also related to the material of the object (9), wherein the second X-ray detector (5) has a second anti-scattering grid, and the second weighting function also represents the influence of the second anti-scattering grid on the scattered radiation distribution (14) collected by the second X-ray detector (5).

16. A medical imaging device (1), comprising: - First radiation source (2), used to generate primary X-ray radiation (6) and to irradiate the object (9) with primary X-ray radiation (6); - A first X-ray detector (3) associated with the first radiation source (2) is used to acquire the intensity distribution (17) of the X-ray radiation, which is determined by a portion (10) of the primary X-ray radiation (6) transmitted through the object and the scattered radiation (11) generated by the scattering of the primary X-ray radiation (6) on the object (9). - A second X-ray detector (5), different from the first X-ray detector (3), is used to collect the scattered radiation distribution (14) of the scattered radiation (11) generated on the object (9), the scattered radiation distribution representing the intensity of the scattered radiation collected over a predetermined width of the second X-ray detector, wherein, Given a pre-defined position for the first X-ray detector (3), the second X-ray detector (5) can be positioned in multiple different locations. Its features are, - A computing device (13) configured to estimate, based on a second weighting function, a portion (15) of the scattered radiation (11) collected by the first X-ray detector (3) based on the scattered radiation distribution (14) collected by the second X-ray detector (5), and to determine, based on the spatial distribution (15) estimated for the scattered radiation (11) on the first X-ray detector (3), a portion (10) of the transmitted primary X-ray radiation (6) collected by the first X-ray detector (3) from the intensity distribution (17) collected by the first X-ray detector (3), wherein the second weighting function relates to the angle between the main extension planes of the first X-ray detector (3) and the second X-ray detector (5), wherein the spatial distribution of the portion of the scattered radiation (11) represents the intensity of the scattered radiation collected over a predetermined width of the first X-ray detector.

17. The medical imaging device (1) according to claim 16, characterized in that, The first X-ray detector (3) has a first housing, and the second X-ray detector (5) has a second housing that is different from the first housing.

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