Selection of a radiation shape filter from a plurality of radiation shape filters

Abstract

Method for selecting a radiation shape filter (200 a , 200 b , 200 c ), which modifies the spatial distribution of the intensity and / or the spectrum of X-ray radiation (R) of an X-ray source (100) of an imaging system (10), consisting of at least one, preferably a plurality of radiation shape filters, wherein - at least one radiation absorption profile, preferably a plurality of radiation absorption profiles of an object under investigation (O), from which image data are to be generated in a later step using the imaging system (10), is recorded parallel to the axis of the object under investigation (z) from different directions, - an effective radiation absorption profile is calculated by averaging the at least one recorded radiation absorption profile. - and the selection of the radiation shape filter (200 a , 200 b , 200 c) based on the effective radiation absorption profile of the object under investigation (O) from a plurality of radiation shape filters (200 a , 200 b , 200 c ).

Description

[0001] The invention relates to a method for selecting a radiation shape filter from a plurality of radiation shape filters and to an X-ray imaging system with a selection unit for selecting a radiation shape filter from a plurality of radiation shape filters.

[0002] In X-ray imaging systems, particularly computed tomography systems, a diaphragm is usually positioned between the X-ray source and the object being examined. This diaphragm initially determines the opening angle of the X-ray beam and the shape of the area illuminated by the X-rays. A radiation shape filter is often placed downstream of this diaphragm in the X-ray path. This filter can further modify the intensity of the X-rays spatially or spectrally. These filters are essentially planar filters through which the entire X-ray beam (typically limited by the diaphragm) passes, without the need for openings through which the X-rays could pass unchanged. These filters are typically made of aluminum or Teflon.

[0003] To manipulate and further modify the spectral or spatial intensity distribution of X-rays, various types of radiation shape filters can be used, such as bowtie filters (i.e., filters that additionally focus or spread the X-rays with convex or concave surfaces, typically similar to the shape of a bow tie) or wedge-shaped filters. These filters can be inserted into the X-ray beam path between an X-ray source of the imaging system and an object under investigation, either individually or in combination. For example, a bowtie filter can be used to define at least local extrema of the X-ray intensity within the X-ray beam.The intensity of X-rays can be reduced by a continuous attenuation value, for example, using a wedge filter positioned perpendicular to the direction of X-ray propagation. The intensity minimum is usually located at the edge of the X-ray beam used (which is limited by the aperture).

[0004] In particular, it is possible to define the size or extent of the irradiated area or areas of one or more radiation extrema. This means that, in addition to different types of radiation shape filters, it is also possible to select between different radiation shape filters of the same type. For example, with filters of the same type, one can choose between "narrow filters," which spatially reduce the irradiated area, or "wide filters" and "very wide" filters, which may expand the irradiated area or the area of ​​an intensity extremum.

[0005] Furthermore, it is also conceivable that the radiation shape filters influence the spectrum of the X-rays used, particularly spatially (i.e., when the X-rays pass through the filter, the spectral intensity distribution changes). For example, in a spatial region defined by the filter, the spectrum of the X-rays can be hardened, meaning that an intensity maximum of the X-rays is shifted towards shorter wavelengths. Likewise, the spectrum of the X-rays can potentially be softened with the help of the filter in the given spatial region (i.e., an intensity maximum is shifted towards longer wavelengths).

[0006] The operator of an X-ray imaging system has a wide selection of filters to choose from to optimize the image. This optimization can consist of ensuring the image quality of the intended exposure and minimizing the radiation dose to the patient during the imaging process. Such optimization relies largely on the operator's experience.

[0007] Ideally, a suitable scan or examination protocol (i.e., a sequence of control steps) is defined for each application of the imaging system, based on these optimization goals. This protocol controls image acquisition within the imaging system and may specify the radiation shape filter to be used. If no scan protocol is available for a particular application, it must first be created based on the operator's expertise. Optimal selection of radiation shape filters may not always be guaranteed in this case. Furthermore, assigning radiation shape filters to specific protocols is cumbersome and hinders the simplification of operating an X-ray imaging system.

[0008] A radiation shape filter is typically used in examination protocols for children. However, depending on the patient's constitution and the scan area, a radiation shape filter could also be used in adults to reduce the X-ray dose. Conversely, in certain cases, it might be beneficial to omit the radiation shape filter in children to achieve better image quality.

[0009] Currently, radiation shape filters are only used in protocols for children. Typically, particularly narrow radiation shape filters are used for children. In contrast, radiation shape filters are not usually used for adults. However, if, for example, a tall child has the dimensions of an adult, it may be advisable to omit the radiation shape filter or to use a wider radiation shape filter, i.e., one with a broader irradiation area, for which no specific protocol for children exists. However, with the conventional method, in which specific protocols, such as those for children, are assigned to individual filters, the parameters specific to these protocols are also lost.For example, if, instead, a radiation filter were omitted for a child and an adult protocol, which allows a higher radiation dose, were used, the child could be exposed to an excessive dose of radiation. Conversely, it might be advisable to use a radiation shape filter for a small adult. However, adult protocols are not compatible with radiation shape filters. If a special protocol for children, corresponding to the radiation shape filter used, is simply applied to the adult, the result is not optimal. For example, the contrast is not as good as it could be if an adult-acceptable dose were used, due to an insufficient X-ray dose. The problem, therefore, is that the protocols associated with the filters are not always compatible.The protocols assigned to unfiltered recordings are specified for certain age groups. However, if one wants to use the filters or no filter at all for people of other age groups, the problem arises that the protocols cannot simply be transferred to other age groups.

[0010] US Patent 2014 / 0005533A1 describes a method for generating an X-ray image of a patient using a contrast agent. During image acquisition preparation, the selection of the X-ray energy spectrum and the contrast agent dose is determined based on the patient's thickness. In this context, an average patient thickness is determined and used as the basis for adjusting the energy spectrum and contrast agent dose.

[0011] The object of the present invention is therefore to improve the quality of X-ray images or the radiation exposure of an object of examination through X-ray imaging, particularly when examining different age groups, or to enable a more flexible application of radiation absorption filters.

[0012] This problem is solved using a method for selecting a radiation shape filter according to claim 1 and an X-ray imaging system according to claim 14.

[0013] According to the invention, an improved method for selecting a radiation shape filter from at least one, preferably a plurality of radiation shape filters is proposed.

[0014] The radiation shape filter, which can be configured as described in the introduction, modifies, for example, the spatial distribution of intensity and / or the spectrum of X-rays from an X-ray source of an imaging system. The spectral modification is preferably also spatial with respect to the wavelengths emitted by the X-ray source. The selection of a radiation shape filter can also refer to the absence of a radiation shape filter, for example, omitting a radiation shape filter in a specific spatial region between the X-ray source and the object under investigation. In the following, a radiation shape filter can also be understood as an arrangement of radiation shape filters comprising multiple radiation shape filters.

[0015] According to the invention, at least one, preferably a plurality of, radiation absorption profiles of an object under investigation, from which image data are to be generated in a later step using the imaging system, are recorded parallel to the axis of the object under investigation from different directions.

[0016] According to the invention, for example, anatomical data of a patient, in particular from images, topograms or other representations of the patient, can be used to determine a radiation absorption profile.

[0017] In general terms, absorption profiles capture anatomical measurement data of a subject, which is then used to create an image using the imaging system. Anatomical measurement data refers to data based on anatomical parameters such as the shape, position, or structure of body parts, organs, tissues, or cells. This means, in particular, that the anatomical measurement data directly or indirectly represent these anatomical parameters.

[0018] An effective radiation absorption profile is calculated from the recorded radiation absorption profiles by averaging the recorded radiation absorption profiles.

[0019] For example, the absorption values ​​of the effective radiation absorption profile can be calculated in the simplest case using the following formula: aeff(xi,yi)=a¯(xi,yi)=∑k=1Kak(xi,yi)K

[0020] Here, K represents the number of recorded radiation absorption profiles; a k (x i ,y i ) is the absorption value of the k-th recorded radiation absorption profile at the location (x i , y i ) ; a eff (x i , y i ) is the absorption value of the determined effective radiation absorption profile at the location (x i ,y i ).

[0021] In particular, the method according to the invention can be used to determine, based on the effective radiation absorption profile and further anatomical measurement data, which of the available radiation shape filters should be selected most advantageously for a planned X-ray imaging.

[0022] According to one embodiment, an automatic determination or selection of a radiation pattern filter arrangement eliminates the need for manual determination of a filter arrangement. Only after the automatic determination can a final confirmation step for selecting the filter arrangement be required.

[0023] In particular, the selection according to the invention can be independent of a measurement protocol mentioned at the outset for controlling the imaging system.

[0024] Alternatively, imaging can also be controlled based on a standardized scan or examination protocol with regard to filter selection, for example, a protocol for a specific age group, so that the selection of an unsuitable radiation shape filter can be largely eliminated. This standardized measurement protocol might then, for example, include only one step in which the determination or selection of a radiation shape filter or a radiation shape filter arrangement according to the invention is performed automatically. That is, the imaging system is controlled based on a measurement protocol that includes the step of automatically selecting a radiation shape filter or determining a radiation shape filter arrangement using the method according to the invention. The standardized measurement protocol itself can, for example, be generated using the method according to the invention.

[0025] In this case, for example, the data obtained for the selection can also be used to determine whether the person to be examined is a child or an adult, and whether, for example, due to the dimensions of the person to be examined, it may still be useful to use a radiation shape filter in the case of an adult.

[0026] In the inventive method, according to one embodiment, the selected radiation shape filter arrangement can then be automatically introduced into the beam path of the X-ray source of the imaging system in a further step.

[0027] Preferably, as mentioned at the outset, the radiation shape filter arrangement is positioned downstream of the X-ray imaging system's aperture in the X-ray beam path. As mentioned, the radiation shape filter arrangement is inserted between the X-ray source and the object being imaged, or, if necessary, radiation shape filters are removed from the beam path. This can be accomplished, for example, using suitable robotics, thus rendering operator control instructions obsolete in this respect as well. The corresponding control steps can, in turn, be part of a suitable measurement protocol, which is then dynamically modified based on the determined selection in order to execute the necessary control steps.Alternatively, the insertion of the determined radiation shape filter arrangement into the X-ray beam path can also be part of the automatic selection procedure, so that it is sufficient if the measurement protocol includes the step of automatic selection of the radiation shape filter as mentioned above.

[0028] In particular, the method according to the invention can be used in an X-ray imaging system which has a detection unit for detecting a plurality of radiation absorption profiles of an object under investigation, from which image data are to be generated in a later step using the imaging system, parallel to the patient axis from different directions.

[0029] The acquisition unit can also be designed as an interface through which, for example, an anatomical parameter can be directly acquired if it exists as a directly measured parameter value or a directly identifiable parameter. Furthermore, it is also conceivable that the acquisition unit functions as a parameter determination unit, designed to generate or determine anatomical parameters or parameter values ​​indirectly represented by the anatomical measurement data.

[0030] Furthermore, the X-ray imaging system according to the invention has a computing unit which is set up to calculate an effective radiation absorption profile by averaging recorded radiation absorption profiles.

[0031] Therefore, to determine the appropriate radiation absorption filter, at least one, and preferably several, radiation absorption profiles should be recorded, which can then be used to calculate the effective absorption profile. On the one hand, averaging even a small number of radiation absorption profiles allows for very precise information regarding the optimal radiation absorption filter. On the other hand, using a small number of radiation absorption profiles keeps the patient's radiation exposure low during the acquisition of the information for filter selection.

[0032] Furthermore, the X-ray imaging system according to the invention includes a selection unit for selecting a radiation shape filter. The selection unit is configured to select a radiation shape filter from a plurality of radiation shape filters based on the effective radiation absorption profile of the object under investigation.

[0033] The selection can also be made automatically based on anatomical measurement data (or anatomical parameters determined from it).

[0034] Instead of a single radiation shape filter, a radiation shape filter arrangement can also be selected or determined.

[0035] In particular, the selection unit can be combined with a filter determination unit. The filter determination unit first automatically generates one or more suggestions for selecting a radiation shape filter arrangement based on the effective radiation absorption profile and, for example, anatomical measurement data. The selection of the radiation shape filters is then carried out by the selection unit based on the suggestions generated by the filter determination unit. As mentioned, the selection unit can, for example, be configured to capture confirmation from the user of the X-ray system in order to perform a final selection of a radiation shape filter or radiation shape filter arrangement for a planned X-ray measurement. For example, it is conceivable that the filter determination unit is integrated into the selection unit or is built separately from the selection unit.

[0036] Further, particularly advantageous embodiments and developments of the invention result from the dependent claims and the following description, whereby the independent claims of one claim category may also be further developed analogously to the dependent claims of another claim category.

[0037] According to a simple implementation of the method, the majority of radiation absorption profiles can be recorded from the anterior-posterior direction and the lateral direction.

[0038] Specifically, two radiation absorption profiles can be recorded, one in the anterior-posterior direction and one in the lateral direction. This can be particularly useful if the object under investigation is aligned parallel or perpendicular to these directions, as the maximum and minimum dimensions are then included in the calculation of the effective absorption profile.

[0039] In a particularly preferred embodiment of the method, a patient-specific control protocol is selected independently of the radiation shape filter, taking into account the radiation absorption profile and / or other measurement data. This advanced training therefore not only separates the filter selection from the use of a specific control protocol, but also additionally performs the selection of the control protocol based on the acquired measurement data or the radiation absorption profile. For example, the acquired measurement data can be used to determine whether a protocol specific to children or an adult-specific protocol should be applied. This allows for even greater automation of the imaging process, enabling less qualified personnel to perform the imaging procedures.

[0040] In order to obtain the most realistic data possible for the radiation absorption profile, it may be useful to record at least one radiation absorption profile using X-rays.

[0041] If the radiation exposure of the patient is to be minimized, it may be useful to obtain the data for the radiation absorption profiles by determining the patient contours without using X-rays.

[0042] For example, patient contours can be measured using a camera.

[0043] As mentioned previously, recording radiation absorption profiles can also be carried out by considering additional information about the object under investigation. More specifically, this means, for example, weighting the recorded absorption profiles or, in the case of indirect recording of absorption profiles, such as via camera, incorporating additional data about the person, body part, or organ being examined into the determination of the radiation absorption profiles or the calculation of the effective radiation absorption profile. This additional information could include, for example, the age, weight, height, body mass index, and the specific body region being examined.

[0044] If a specific area of ​​the body is of particular interest, it can be useful to weight a particular body region of the subject when averaging the recorded radiation absorption profiles. For example, if a specific organ is to be clearly visible in the images when applying the method, the area occupied by that organ in the radiation absorption profiles will be given particular weight during the averaging process and the calculation of an effective radiation absorption profile.

[0045] With different weighting of individual recording areas of the radiation absorption profiles, the effective radiation absorption profile can result, for example, as follows: aeff(xi,yi)=a¯(xi,yi)=∑k=1Kgk(xi,yi)⋅ak(xi,yi)K

[0046] Here, K represents the number of recorded radiation absorption profiles; g k (x i ,y i ) is the weighting factor of the k-th recorded radiation absorption profile at the location (x i , y i ), where ∑k=1Kgk(xi,yi)K=1 is standardized; a k (x i ,y i ) is the absorption value of the k-th recorded radiation absorption profile at the location (x i , y i ) ; a eff (x i , y i ) is the absorption value of the determined effective radiation absorption profile at the location (x i , y i ).

[0047] If, for example, a specific area, such as a particular organ, is to be recorded, this area can simply be weighted more heavily when determining the effective radiation absorption profile.

[0048] On the other hand, if, for example, the lowest possible radiation exposure is required, a kind of worst-case scenario can be assumed, whereby determining the effective radiation absorption profile includes recording the broadest profile over the sampling range as the effective radiation absorption profile.

[0049] Selecting the radiation shape filter based on the effective radiation absorption profile of the object under investigation can be implemented by choosing from the N available radiation shape filters based on their individual radiation absorption profiles. The radiation shape filters already available for selection can therefore be assigned pre-determined radiation absorption profiles. When selecting the optimal radiation shape filter based on the pre-assigned individual radiation absorption profiles of the respective filters, only the individual radiation absorption profiles of the N radiation shape filters need to be compared with the determined effective radiation absorption profile.Subsequently, the radiation shape filter of the N radiation shape filters with the radiation absorption profile that best matches the determined effective radiation absorption profile of the object under investigation can be selected.

[0050] Determining the radiation shape filter from the N radiation shape filters with the radiation absorption profile that best matches the effective radiation absorption profile can, in particular, involve applying a differential measurement method. For example, the method of least squares can be used as the differential measurement method.

[0051] If the method of least squares is applied, the procedure can be carried out according to the following formula: nopt=min(F(n))=min(∑xi,yi(aeff(xi,yi)+an(xi,yi)−bn¯)2)

[0052] Here, 1 <= n <= N; N indicates the number of available radiation shape filters; n optis assigned to the optimal radiation shape filter; the coordinates x i and y i are coordinates of the absorption values ​​of the effective radiation absorption profile at the location (x i , y i ) ; a eff (x i , y i ) is the absorption value of the determined effective radiation absorption profile at the location (x i ,y i ); a n (x i ,y i ) in this case is the absorption value of the radiation absorption profile of the nth radiation shape filter of the N available radiation shape filters themselves; bn¯=∑i=IIaeff(xi,yi)+an(xi,yi)I is the mean value of the added radiation absorption profiles of the patient and the nth radiation shape filter; I is the total number of pixels (x i ,y i An additional weighting factor may also be included in the calculation of the mean.

[0053] As mentioned, in the method according to the invention, for example, a selected radiation shape filter arrangement, i.e., in particular also a single radiation shape filter, can be automatically inserted into or removed from the beam path of the X-ray source. This can be done, for example, with a radiation shape filter device which has a control unit or is connected to a control unit. The radiation shape filter device is then configured to automatically insert or remove a selected radiation shape filter into or from the beam path of the X-ray source during operation. For this purpose, the radiation shape filter device includes, for example, robotics, i.e., in particular an automatic drive, which can be based, for example, on spring force, electrical energy, pneumatic or hydraulic energy. The robotics orThe radiation shape filter device can receive corresponding filter control signals from the aforementioned control unit, which control the movement of the radiation shape filters in or out of the beam path of the X-ray source.

[0054] The filter control signals are generated by the control unit based on the determined or selected shape filter arrangement. For example, the control unit can be integrated into the selection unit. This provides, in particular, a means of automatically modifying a radiation shape filter arrangement.

[0055] The collected measurement data can be used in a further development of the procedure to determine a person's age group. For example, bone density can be used to determine age, and a corresponding protocol appropriate to the respective age group can be automatically generated.

[0056] Furthermore, the type of area under investigation, such as a heart or an arm, can also serve as a basis for the selection or determination of the radiation shape filters or the radiation shape filter arrangement according to the invention. In particular, the spatial location or structural parameters, such as the type of tissue, can contribute to this basis.

[0057] Preferably, the area under investigation or the dimensions of the object under investigation can be determined automatically, thus eliminating the need for manual input of this data.

[0058] Furthermore, the selection or determination of the radiation shape filter or radiation shape filter arrangement can be performed automatically based on the expected attenuation of the X-ray radiation by the object being imaged. For example, the patient's weight could be measured and their geometric dimensions determined to ascertain the expected attenuation.

[0059] In particular, the expected attenuation of the X-ray radiation can be determined automatically. This is achieved by automatically weighing and measuring the patient's size to derive the expected attenuation of the X-ray radiation, and vice versa.

[0060] In addition to the direct measurement of the expected attenuation of the X-ray radiation, for example by means of a topogram or radiation absorption profile, it is therefore possible to use the aforementioned anatomical parameters such as the weight or size of the patient or other structural information to determine the effective absorption profile.

[0061] The described anatomical measurement data, such as weight, size and examination area, can be taken into account differently in determining the radiation shape filter arrangement.

[0062] The selection of radiation shape filters, for example for a heart or skull X-ray, can be essentially determined by the examination area. In this case, the examination area largely determines the expected attenuation of the X-ray radiation and also the X-ray spectrum to be used. For skull X-rays, for example, a softer X-ray spectrum may be used; that is, the radiation shape filter then modifies the X-ray spectrum compared to the spectrum produced by the radiation source, resulting in a softer spectrum. The spatial distribution can be chosen, for example, so that the object being examined, or a specific area of ​​the object being examined, receives a high dose, while the rest of the patient receives a lower dose.

[0063] This can mean, for example, in the step of averaging the radiation absorption spectra, that certain areas which are to be irradiated with a high dose are given particular weight.

[0064] To determine radiation absorption profiles, ultrasound images, MRI images or other prior information can be used, for example.

[0065] In particular, this allows for low-radiation acquisition of radiation absorption profiles, which can be used to minimize a patient's overall radiation exposure for a planned X-ray examination. This can be achieved, for example, by eliminating the need to generate a topogram based on an X-ray image for selecting the optimal filter or controlling the X-ray imaging system.

[0066] It is still possible to integrate one or more of the described components, units or devices into each other in order to achieve an optimized design of the X-ray imaging system and to simplify the consideration of the aforementioned interactions.

[0067] The invention is explained in more detail below with reference to the accompanying figures and exemplary embodiments. The different figures show identical components with identical reference numerals. They show: Fig. 1 a first embodiment of an imaging system comprising an X-ray source and an X-ray detector, wherein a radiation shape filter is automatically selected from a plurality of radiation shape filters and is placed in the beam path of the X-ray source, Fig. 2 the recording of several radiation absorption profiles in the anterior-posterior direction and in the lateral direction according to an embodiment of the invention, Fig. 3 a flowchart illustrating the method according to an embodiment of the invention.

[0068] Fig. Figure 1 schematically shows a cross-sectional view perpendicular to a system axis of an X-ray imaging system, here a CT system 10, for generating two-, three-, or more-dimensional computed tomography image data. The CT system 10 essentially consists of a conventional scanner in which an X-ray detector 150, mounted on a gantry, rotates around a measuring chamber with an X-ray source 100 opposite the detector 150. This is schematically indicated by dotted lines with an end arrow. In front of the scanner is a patient positioning device or patient table 20, the upper part of which, with a specimen O or patient O placed on it, can be moved relative to the scanner in the direction of the system axis z in order to move the patient O relative to the detector 150 through the measuring chamber. The system axis z simultaneously forms a common axis of rotation for the detector 150 and the X-ray source 100.The scanner and the patient table 20 are controlled by a control unit 30, from which control data is sent via a standard interface to control the CT system 10 according to predefined measurement protocols P.

[0069] It should be emphasized that the methods described below can, in principle, also be used on other CT systems, e.g., with a detector forming a complete ring. Furthermore, the methods can also be used, for example, with other X-ray imaging systems.

[0070] The raw data (i.e., X-ray projection data) acquired by detector 150 are transferred to a measurement data interface of the control unit 30. This raw data is then further processed in an image reconstruction unit implemented as software on a processor within the control unit 30, which, for example, reconstructs image data from the raw data.

[0071] The finished computed tomography image data, or volumetric image data, generated and reconstructed from the raw data, are then transferred to an image data interface. This interface then stores the generated image data, for example, in a memory of the control unit 30, displays it on a screen of the control unit 30 in the usual manner, or feeds the data into a network connected to the computed tomography system, such as a PACS (Postal Archive and Communication System) or RIS (Radiology Information System), or stores it in mass storage devices or prints the corresponding images on connected printers. The data can also be further processed and then stored or output in any other way.

[0072] The raw data recorded may also include, in particular, so-called topogram data T, which in this specific case represent the data of the recorded radiation absorption profiles.

[0073] In Fig. Figure 2 shows how topogram images or radiation absorption profiles T are recorded in the posterior-anterior direction, i.e., in the vertical and lateral directions. The patient O, lying on a couch 20, is irradiated once in the perpendicular direction and once in the lateral direction by the X-ray source 100. The detector 150 is positioned at the point opposite the X-ray source 100 in each case. Two-dimensional projections are recorded as radiation absorption profiles.

[0074] The recorded radiation absorption profiles can be used, as explained in more detail below, within the scope of the invention to select a radiation shape filter or a radiation shape filter arrangement from a plurality of radiation shape filters.

[0075] As explained above, various anatomical parameters can be derived directly and indirectly from the topogram data T. This is done using a data acquisition unit 65, which receives the topogram data T and determines the anatomical parameters from it. For example, topogram data T directly contains the expected attenuation of X-rays due to the nature of the object under investigation O. The attenuation expected locally at a specific detector position depends in particular on anatomical parameters such as the dimensions of the subject O, i.e., especially its size, weight, and the location and structure of organs, body parts, or tissues, so that these anatomical parameters can be directly determined or generated from the topogram data T.

[0076] For example, anatomical parameter values ​​for the position, size or structure of the head of the object under investigation can be obtained or generated from the topogram data T.

[0077] For example, the location of an examination area can also be determined based on the topogram data T, in order to enable, for example, the targeted recording of the head, the heart or the lungs.

[0078] Alternatively or additionally to the topogram data T, anatomical measurement data, from which anatomical parameters or parameter values ​​can be determined, can also be obtained in the form of image data B, generated, for example, by a camera 300. The camera 300 shown generates anatomical measurement data B in the form of images or image data B of the patient O based on light in the visible wavelength range, while the patient O is lying on the patient table 20. This image can also be sufficient to generate parameters for the position, size, or structure of the head of the subject.

[0079] To determine the location of organs or other tissues, for example, the image data B can be combined with prior information, such as ultrasound scans or previous MRI / CT scans. It is also conceivable that the ultrasound scans are acquired during or after the acquisition of the image data B and subsequently combined with, for example, the image data B or topogram data T. The radiation exposure caused by the planned X-ray examination is not increased in this way, since this prior information is already available and could be provided as anatomical measurement data, for example, via the aforementioned PACS system.

[0080] Furthermore, the weight of patient O could, for example, be determined in advance or, for example, with the help of a weighing device (i.e., based on a mass comparison) or weighing device (i.e., based on the weight force) of the patient bed 20, or estimated from the image data B.

[0081] The radiation absorption profiles T and other anatomical measurement data B provided in this way, i.e. in particular the image data B, are then taken over by the acquisition unit 65, evaluated if necessary and transmitted to a filter determination unit 60.

[0082] Based on the recorded radiation absorption profiles and other determined anatomical measurement data (or the associated anatomical parameters and / or parameter values), the optimal geometry of the X-ray radiation R emitted by the X-ray source 100 can be determined or selected. This data also defines the optimal wavelength spectrum of the X-ray radiation R. The filter determination unit 60 has a processing unit 40. This calculates the effective radiation absorption profile of the respective patient based on the measured radiation absorption profiles. From this, and based on the other anatomical parameters, the filter determination unit 60 determines an optimal shape with regard to the spatial distribution of the X-ray radiation and the spectrum used. This additional information is incorporated into the calculation of the effective radiation absorption profile by weighting the radiation absorption profiles.

[0083] For example, it can be advantageous to use a radiation shape filter for a CT scan of the heart, which—as explained earlier—is "narrower" than for abdominal or thoracic scans, in order to focus the full X-ray intensity on the area being examined, such as the heart, and reduce the dose in the periphery. In this case, the area being examined largely determines the geometric shape and spectral distribution of the optimal X-ray radiation R for the planned scan.

[0084] Furthermore, the patient's size and thickness (or weight) can significantly influence both the spectral distribution of the X-rays and the geometric shape of the optimal X-ray distribution. For example, for obese patients, a different radiation pattern filter may be used compared to the standard filter intended for patients of normal weight, such as for chest X-rays. Simultaneously, a hardened X-ray spectrum would be used, meaning that the optimal X-ray spectrum is also influenced by the patient's size or weight.

[0085] Conversely, for children, for example, the parameters "size" or "thickness" may dictate the use of "narrower radiation shape filters" for a "softer" spectrum of X-rays than for an adult patient.

[0086] An advantage of the method according to the invention is that the aforementioned special features result directly from the recorded absorption profiles. For example, a person's thickness can generally be determined from the contours visible on the absorption profile. On the other hand, these specific features can also be taken into account during the recording of the radiation absorption profiles. For example, only a limited area of ​​the body can be irradiated during the recording of the radiation absorption profiles. Finally, the data acquired in addition to the radiation absorption profiles can be used to weight the radiation absorption profiles when calculating an effective radiation absorption profile.

[0087] According to one embodiment of the invention, the filter determination unit 60 is used to determine the radiation shape based on the existing radiation shape filters 200. a , 200 b , 200 can optimal radiation shape filter arrangement was determined.

[0088] In the exemplary embodiment, a selection unit 50 comprises, in addition to the aforementioned detection unit 65, the filter determination unit 60, the processing unit 40, and a control unit 70, which transmits filter control signals S to a radiation shape filter device 220 based on the radiation shape filter arrangement determined with the aid of the filter determination unit 60. The selection unit 50 selects the determined radiation shape filter 200. c for a subsequently planned CT scan.

[0089] The radiation shape filter device 220 features robotics that, based on the filter control signals S, selects the filter 200. c introduces the X-ray beam path to a location determined with the aid of the filter determination unit 60.

[0090] As indicated by the dashed line, the selection unit 50 can also be part of the radiation shape filter device 220. Furthermore, the selection unit 50 can be implemented in another way, for example, at least partially in the form of software on a processor of the imaging system 10 and, in particular, on a processor of the control unit 30.

[0091] In the Fig. In the embodiment shown in 1, a bowtie filter 200 is used. c In the path of the X-ray radiation R, a aperture 105 is subsequently inserted between the X-ray source 100 and the patient O.

[0092] With the aid of aperture 105, a beam of X-ray radiation R is initially defined, which then passes through the patient O. For example, a fan or cone beam is limited in the usual way using aperture 105. The Bowtie filter 200 is arranged downstream. cThe spatial intensity of the X-ray radiation R is determined such that the maximum radiation intensity R reaches the area of ​​the heart of the subject O. The intensity distribution is adjusted along an axis that runs perpendicular to the system axis z.

[0093] In Fig. Figure 3 illustrates the procedure for selecting a radiation shape filter. In step 3.I, a plurality of radiation absorption profiles of an object O, from which image data will be generated in a later step using the imaging system 10, are acquired parallel to the object axis z from various directions. In step 3.II, an effective X-ray absorption profile is calculated by averaging the acquired radiation absorption profiles, and in step 3.III, the radiation shape filter 200 is selected. cbased on the effective X-ray absorption profile of the object under investigation O from a plurality of radiation shape filters 200 a , 200 b , 200 c . The selection from among N radiation shape filters can be made based on the individual radiation absorption profiles of the radiation shape filters by comparing the pre-assigned, individual radiation absorption profiles of the N radiation shape filters with the effective radiation absorption profile of the object under investigation O and selecting the radiation shape filter 200. c the N radiation shape filter 200 a , 200 b , 200 cThe selection should be made using the radiation absorption profile that best matches the determined effective radiation absorption profile. For example, a radiation shape filter is a particularly good match for the effective radiation absorption profile of a test object if the total absorption of the radiation shape filter and the object under investigation is constant or uniform across the irradiation area or radiation cross-section.

[0094] Selecting the radiation shape filter from the N radiation shape filters 200 a , 200 b , 200 cThis can include, in particular, a differential measurement method. For example, the method of least squares is used to determine which combination of the respective radiation shape filter or the radiation absorption profile of the respective radiation shape filter and the recorded or calculated effective radiation absorption profile of a patient results in the most uniform radiation absorption profile.

[0095] The described procedure can preferably be performed automatically. This procedure prevents the incorrect application of scan protocols, as individual filters are not necessarily assigned a specific protocol, for example, one suitable only for a particular age group. Instead, the appropriate filter can be selected regardless of the age group. The preferably automated selection of the optimal shape filter allows for optimal dose distribution and improved image quality. In contrast to the conventional method, it allows for individual adaptation to the patient. Furthermore, the process steps can be completed easily and quickly. Finally, particularly in the case of automatic selection of the radiation absorption filter, no specialized knowledge is required from the operator.the physician's expertise in creating admission protocols is not required, as the automatic selection of the appropriate form filter does not require expert intervention or decision-making processes based on detailed specialist knowledge of the operating staff.

[0096] Finally, it should be noted that the previously described X-ray imaging system and the method for selecting a radiation shape filter are merely exemplary embodiments which can be modified in various ways by those skilled in the art without departing from the scope of the invention. Furthermore, the use of the indefinite articles "a" or "an" does not preclude the possibility that the features in question may be present multiple times. Likewise, the term "unit" does not preclude the possibility that the components in question consist of several interacting sub-components, which may also be spatially distributed.

Claims

[1] Method for selecting a radiation shape filter (200 a , 200 b , 200 c ), which modifies the spatial distribution of the intensity and / or the spectrum of X-ray radiation (R) of an X-ray source (100) of an imaging system (10), consisting of at least one, preferably a plurality of radiation shape filters, wherein - at least one radiation absorption profile, preferably a plurality of radiation absorption profiles of an object under investigation (O), from which image data are to be generated in a later step using the imaging system (10), is recorded parallel to the axis of the object under investigation (z) from different directions, - an effective radiation absorption profile is calculated by averaging the at least one recorded radiation absorption profile. - and the selection of the radiation shape filter (200 a , 200 b , 200 c) based on the effective radiation absorption profile of the object under investigation (O) from a plurality of radiation shape filters (200 a , 200 b , 200 c ). [2] Method according to claim 1, wherein the majority of the radiation absorption profiles are recorded from the anterior-posterior direction and the lateral direction. [3] Method according to claim 1 or 2, wherein, irrespective of the selection of the radiation shape filter, a patient-specific measurement protocol is selected taking into account the effective radiation absorption profile and / or other measurement data. [4] Method according to any one of claims 1 to 3, wherein the at least one radiation absorption profile is recorded using X-rays. [5] Method according to any one of claims 1 to 3, wherein the at least one radiation absorption profile is determined by measuring the patient contours. [6] Method according to claim 5, wherein the measurement of the patient contours is carried out using a camera. [7] Method according to any one of claims 1 to 6, wherein the recording of the at least one radiation absorption profile is carried out by taking into account additional information about the object (O) to be investigated. [8] Method according to claim 7, wherein the additional information includes the age and / or weight and / or height and / or body mass index and / or the body area to be examined of the object (O). [9] Method according to any one of claims 1 to 8, wherein the averaging of the at least one recorded radiation absorption profile comprises weighting a specific body area of ​​the object (O) to be examined. [10] Method according to any one of claims 1 to 9, wherein the selection of the radiation shape filter (200 c) based on the effective radiation absorption profile of the object under investigation (O) the selection from a plurality of radiation shape filters (200 a , 200 b , 200 c ) based on the individual radiation absorption profiles of the radiation shape filters. [11] Method according to claim 10, wherein the selection of the radiation shape filter (200 c ) from a plurality of radiation shape filters (200 a , 200 b , 200 c ) selecting the radiation shape filter (200 c ) from the majority of radiation shape filters (200 a , 200 b , 200 c ) with the individual radiation absorption profile that best matches the effective radiation absorption profile of the object under investigation (O). [12] Method according to claim 11, wherein the selection of the appropriate radiation shape filter (200 c ) from the majority of radiation shape filters (200 a , 200b , 200 c ) includes the application of a differential measurement method. [13] Method according to claim 12, wherein the least squares method is used as the differential measurement method. [14] X-ray imaging system (10), with - an X-ray source (100), - a detection unit (65) for detecting at least one, preferably a plurality of, radiation absorption profiles of an object under investigation (O), from which image data are to be generated in a later step using the imaging system (10), parallel to the patient axis from different directions, - a computing unit (40) which is configured to calculate an effective radiation absorption profile by averaging the at least one, preferably the majority of recorded radiation absorption profiles of the object under investigation (O), and - a selection unit (50) designed to select a radiation shape filter (200) based on the effective radiation absorption profile of the object under investigation (O). c ) from a plurality of radiation shape filters (200 a , 200 b , 200 c to select. [15] X-ray imaging system (10) according to claim 14, with a radiation shape filter device (220) which has a control unit (70) to automatically select a radiation shape filter (200) during operation a , 200 b , 200 c ) into the beam path of the X-ray source (100).

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