Photon counting X-ray detector and method of operating a photon counting X-ray detector

Abstract

Embodiments of the present disclosure relate to photon counting X-ray detectors and methods for operating photon counting X-ray detectors. The present invention relates to an X-ray detector having a converter element for converting X-rays into electrical signals and a plurality of pixel elements, wherein each of the plurality of pixel elements has a first signal processing stage for processing the electrical signal, the first signal processing stage respectively having at least one signal amplifier and at least one comparator; the signal output of the first signal processing stage of at least one group of pixel elements in the plurality of pixel elements is coupled to a common second signal processing stage for transmitting the signal; the common second signal processing stage has a configurable switching matrix; so that after configuring the switching matrix for each signal output of the first signal processing stage of a group of pixel elements in the plurality of pixel elements, a processing chain for digitally processing the provided digital pixel signal can be provided.

Description

Technical Field

[0001] The invention relates to a photon counting X-ray detector for recording an X-ray image data set, a medical imaging device having a photon counting X-ray detector, and a method for operating the photon counting X-ray detector. Background Art

[0002] Photon counting X-ray detectors are used in many imaging applications. Thus, these X-ray detectors are used, for example, in computed tomography scanners in medical imaging to generate tomographic X-ray images of an examination region of a patient.

[0003] As a photon counting X-ray detector, in particular, a photon counting direct conversion X-ray detector can be used. In such an X-ray detector, incident X-ray radiation or photons can be converted into electrical pulses by a suitable converter material. The electrical pulses are evaluated by an evaluation electronic device, for example by an integrated circuit (application-specific integrated circuit, ASIC). Then, in the counting X-ray detector, the incident X-ray radiation is measured by counting the electrical pulses triggered by the absorption of X-ray photons in the converter material. The height or length of the generated electrical pulse is usually proportional to the energy of the absorbed X-ray photons. Therefore, spectral information can be extracted by comparing the height or length of the electrical pulse with an energy threshold. Photon counting X-ray detectors usually have multiple settable energy thresholds for comparison, so that energy-resolved measurements can be performed according to multiple energy ranges defined by the energy thresholds. The use of photon counting detectors in X-ray imaging has many advantages over energy integrating detectors. Therefore, the use of photon counting detectors in X-ray imaging makes it possible to achieve high spatial resolution and inherent energy-resolved measurements.

[0004] Typically, the electrical signal generated in the converter element is first processed by electrical signal amplification and electrical signal shaping. In addition, according to different design schemes, the signals of multiple adjacent pixels are combined (called "charge summing" in Chinese). Then, the level of the generated signal is usually compared with one or more thresholds by means of one or more comparators. The digitized signal can be further processed in different ways as follows: for example, the number of times the comparator exceeds the threshold can be counted, for example, the rising edge of the clock can be counted by means of so-called "rising edge counters"; for example, the comparator signals of multiple adjacent pixels can be calculated by means of gating or coincidence logic; for example, the count values ​​of adjacent counters can be calculated by means of fusion (Fusing), summing (Summing); the time point ("time-of-arrival") and / or duration ("time-over-threshold") of the comparator signal can be determined; and so on.

[0005] However, usually only one or two of these methods are actually implemented in the ASIC, and the order is determined in the scope of the design. In addition, the pixel-by-pixel circuit is usually implemented identically for each pixel and, if necessary, an inter-pixel communication logic is additionally embedded, with which the obtained information can be read from the ASIC. Summary of the invention

[0006] The object of the present invention is to provide an improved X-ray detector for flexible use.

[0007] This object is achieved by the features according to the invention. Further advantageous and partly inventive embodiments and developments of the invention are set forth in the dependent claims and in the following description.

[0008] The invention relates to a photon counting X-ray detector having a converter element for converting X-ray radiation into electrical signals and a plurality of pixel elements, wherein:

[0009] a. each pixel element of the plurality of pixel elements has a first signal processing stage for processing the electrical signal, the first signal processing stage respectively having at least one signal amplifier and at least one comparator for providing a digital pixel signal at a respective signal output of the first signal processing stage of a pixel element of the plurality of pixel elements,

[0010] b. a signal output terminal of the first signal processing stage of at least one group of pixel elements among the plurality of pixel elements is coupled to a common second signal processing stage for transmitting a signal, wherein the common second signal processing stage has a plurality of digital logic elements for digitally processing the provided digital pixel signal,

[0011] c. the common second signal processing stage has a configurable switching matrix for interconnecting at least a portion of the plurality of digital logic elements with the signal output terminals of the first signal processing stage of a group of pixel elements in the plurality of pixel elements to transmit signals,

[0012] d. so that after configuring the switching matrix for each signal output terminal of the first signal processing stage of a group of pixel elements among the plurality of pixel elements, a processing chain for digitally processing the provided digital pixel signal can be provided.

[0013] In the context of the present invention, the photon counting X-ray detectors used can also be referred to as direct conversion X-ray detectors. Direct conversion X-ray detectors are usually implemented in a stacked structure, in which an assigned evaluation unit is connected on the bottom side to a layer of converter material (i.e., on the converter element). The bottom side of the converter element usually has a plurality of electrodes in the form of metallized contact elements in a matrix shape, also referred to as sensor pixel electrodes in the following. The evaluation unit contacts these electrodes (for example, welds) to transmit signals. In this case, the contact elements on the converter side are usually arranged opposite to the matching contact elements (also referred to as pixel electrodes in the following) implemented in the form of pixels on the side of the evaluation unit. The evaluation unit then usually provides a pixel-by-pixel pixel electronics device for processing the signals input via the pixel electrodes pixel by pixel. In the converter material of the converter element, the incident X-ray radiation is converted into charge carriers according to the local deposition energy of the X-ray photons, based on which signals (usually electrical pulses) are generated in the pixel-by-pixel pixel electronics device and further processed. The pixel electronics can be assigned a respective detection volume in the converter element pixel by pixel, which detection volume is essentially formed by the electric field between the respective sensor pixel electrode and a top electrode arranged on the opposite side of the converter element and forms the sensitive detection volume of the pixel element.

[0014] According to the invention, each of the plurality of pixel elements of the photon counting X-ray detector has, according to the invention, a first signal processing stage pixel by pixel, which essentially provides analog processing of a signal input via a pixel electrode of the pixel element. In particular, the input signal is amplified by means of a signal amplifier according to the invention of the first signal processing stage, and the amplified signal is compared with at least one threshold representing an energy threshold by means of at least one comparator. In the event that the signal exceeds the threshold, an output signal is output at the comparator. Therefore, the conversion to a digital signal (or multiple digital signals) is essentially carried out in this step, so that a digital pixel signal is provided at the corresponding signal output of the first signal processing stage for further processing in the second signal processing stage.

[0015] The first signal processing stage of one of the plurality of pixel elements may also have more than one comparator, each of which has a threshold value, so as to provide a plurality of digital pixel signals at a plurality of signal output terminals of the first signal processing stage of one of the plurality of pixel elements depending on the threshold value.

[0016] According to the present invention, at least one group of pixel elements among the plurality of pixel elements of the photon counting X-ray detector has a common second signal processing stage. A selected portion of the plurality of pixel elements is combined into a group. Therefore, a common second signal processing stage is provided at least for the pixel elements in the group. All pixel elements in the plurality of pixel elements can be connected to a common processing stage. That is, the at least one group can include all of the plurality of pixel elements. However, the plurality of pixel elements can also be divided into a plurality of groups, each of which is respectively connected to a common second processing stage.

[0017] The multiple digital logic elements provided in the second signal processing stage can be understood as a common resource for digital signal processing of digital pixel signals, which can be commonly used for signal processing of digital pixel signals of pixel elements in a group of multiple pixel elements. Here, the digital logic element can be understood in particular as an electronic circuit that obtains one or more output variables from a set of one or more digitally represented input signals and configuration signals or control signals. Here, the circuit can also have an internal storage element that affects the processing of the input signal (or the value of the storage element). Here, the circuit can work in a clocked, combined or event-driven manner.

[0018] The second signal processing stage includes a configurable switching matrix, which can be configured to interconnect the signal output terminals assigned to the second signal processing stage, so that a processing chain of digital pixel signals output by means of the signal output terminals can be provided for each assigned signal output terminal based on the selection of the provided digital logic elements. In particular, the processing chain represents the interconnection and series connection of the digital logic elements and the corresponding signal output terminals, so that the processing of the signal output at the signal output terminals is realized by connection. At the end of the processing chain, one or more processed digital signals can be provided according to the interconnection. Therefore, the configurable switching matrix can realize the configurable interconnection of the signal output terminals with at least one selection of the provided logic elements. The switching matrix can also interconnect the logic elements in a configurable manner.

[0019] The selection of digital logic elements includes selecting at least a portion of the number of digital logic elements provided.

[0020] The logic element can be interconnected to one or more signal outputs of the first signal processing stage and / or can be interconnected to one or more digital logic elements.

[0021] One or more processed digital pixel signals can - but not necessarily have to - be assignable to a specific pixel element. One or more processed pixel signals can also be based on a plurality of digital pixel signals of different signal output terminals, respectively, and further on different pixel elements in a group. For example, digital pixel signals of different signal output terminals can be calculated together, for example, by means of coincidence logic or summation logic.

[0022] Here, the switching matrix can be designed similar to an FPGA ("field-programmable gate array"). That is, the switching matrix can be designed as an integrated circuit in which logic circuits can be loaded, wherein the desired circuit structure can be defined or adjusted by programming or configuring the switching matrix. Therefore, different circuits and functions can be implemented and especially reconfigured repeatedly by configuring the digital logic elements present inside. In particular, after delivery of the X-ray detector, during operation and for different measurements and applications, the switching matrix can be reconfigured. Therefore, a signal processing chain of digital pixel signals can be provided in an adjustable and configurable manner, thereby providing the functions of the X-ray detector.

[0023] Here, at least one processing chain can be provided for each signal output interconnected with a common second signal processing stage. However, there can also be a configuration of the switching matrix in which no processing of selected signal outputs is provided, i.e. in which no processing chain is provided accordingly after the configuration of the switching matrix. This is in particular the case in which, for example, certain pixel signals are omitted in order to facilitate lower data rates, lower power consumption, etc. That is, after the configuration of the switching matrix, a digital processing chain can be provided for at least some or all signal outputs of the first signal processing stage of at least one group of pixel elements, respectively.

[0024] Preferably, a processing chain can be configured at the digital logic element for each signal output associated with the common second signal processing stage. However, there can also be a variant implementation of the photon counting X-ray detector, in which the signal processing chain can only be configured commonly for the signal outputs of the pixel elements in a group of pixel elements, so that the same processing chain is provided for each pixel element for the provided digital pixel signal of the pixel element. However, this can still include providing different signal processing chains for different pixel signals of the pixel elements at the logic element.

[0025] In this sense, the first signal processing stage can therefore be understood as being formed by pixel electronics pixel by pixel. Then, a pixel element according to the invention in a plurality of pixel elements can be respectively assigned a first signal processing stage, a corresponding pixel electrode or sensor pixel electrode, and a detection volume in a converter element. In contrast, the second signal processing stage, although it can respectively provide a digital processing chain of pixel signals pixel by pixel, is not assigned as a whole to a single specific pixel element, but only to a group of pixel elements.

[0026] The implementation of the X-ray detector according to the invention advantageously allows analog signal processing and digital signal processing to be decoupled to a greater extent. The analog signal processing (amplification and comparator) can advantageously be performed as close to the sensor as possible, and the digital further processing can be clearly extracted and applied jointly to the pixel group.

[0027] The extraction of digital signal processing allows for a high flexibility and reusability of the evaluation unit. The merging of groups of pixels by means of a configurable matrix readout (i.e. a second signal processing stage with a configurable switching matrix) advantageously allows for a processing of the pixel signals adapted to the measurement. The interconnection of the provided logic elements can advantageously be configured and adjusted by the user.

[0028] By connecting the corresponding sensitive detection volume of the pixel element to the analog part of the signal preprocessing, an analog signal preprocessing with minimal impedance, low noise and low power consumption can be achieved. Here, the amplified analog output signal of the signal amplifier is preferably directly connected to at least one or more comparators. This can achieve high switching frequencies and precise timing and generate digital pixel signals, which are robust for transmission to digital logic elements, which are connected via a switching matrix to transmit the signals.

[0029] The architecture according to the invention thus makes it possible to combine particularly advantageous analog performance of signal processing and digitization close to the sensor with the flexibility of a highly configurable digital processing chain.

[0030] Furthermore, embodiments of the X-ray detector according to the invention allow for resource-efficient use of the evaluation unit even at large pixel pitches, for example, where an electrically conductive connection is provided between the evaluation unit and the converter element only for every two pixel electrodes. Specifically, pixel electrodes which are not connected to sensor pixel electrodes via an electrically conductive connection, and the corresponding first signal processing stages coupled to these pixel electrodes, can simply be deactivated or remain unused in the switching matrix. Already used pixels can, for example, still be connected to their actual neighbors in a coincidence logic.

[0031] To this end, it can be advantageously provided that the X-ray detector or at least one switching matrix according to the invention can be configured via settable register parameters, so that different digital processing chains can be provided for the digital pixel signals depending on the set register parameters.

[0032] The register parameters can be adjusted, ie, essentially programmable, for example, via a control interface of the X-ray detector. In this way, the logic of the switching matrix can be re-parameterized and thus adjusted by adjusting the register parameter values ​​for different measurements and / or applications.

[0033] Therefore, automatic parameterization can also be advantageously realized in a simple manner.For example, a plurality of sets of register parameter values ​​can be pre-stored externally in a storage unit or also in a plurality of registers of the switching matrix.

[0034] The set of register parameter values ​​may be present in each case depending on the X-ray application. The selection of a specific X-ray application (e.g. with respect to the object to be examined, a specific recording area, an application process or a specific recording modality) can largely lead to inferences about the recording conditions during the recording of the X-ray image data set, the desired image quality and / or the image information to be obtained, thereby advantageously enabling an adjustment of the X-ray detector as required.

[0035] The set of register parameter values ​​may also be associated with one or more application parameters, for example. The application parameters may be parameters of an X-ray application and / or parameters of a medical imaging device to which the X-ray detector according to the invention is assigned and / or parameters of a medical imaging device structurally connected to the X-ray detector according to the invention.

[0036] This means that the application parameters can be directly associated with the X-ray application or can also be derived from the X-ray application. For example, the application parameters can be based on the X-ray flux, the time point or duration, the control parameters of the medical X-ray device (e.g. X-ray tube current or X-ray tube voltage), the image parameters of the X-ray image data set to be recorded (e.g. spectral resolution or spatial resolution).

[0037] Furthermore, the application parameters can also be based, for example, on boundary conditions which are predefined by the medical imaging device to which the X-ray detector according to the invention is assigned, such as, for example, available cooling power or power supply.

[0038] Advantageously, the X-ray detector can be configured simply and possibly automatically, so that a configuration of the X-ray detector which is most advantageous for the X-ray application, the given boundary conditions of the medical X-ray system and / or the measurement can always be provided.

[0039] In another embodiment of the photon counting X-ray detector, a first processing chain may be provided for a first number of signal outputs of the pixel element group, and a second processing chain different from the first processing chain may be provided for a second number of signal outputs.

[0040] Advantageously, the signal processing can be flexibly configured and adjusted as required.

[0041] In this context, different processing chains can be provided for different signal outputs of the pixel elements. For example, interconnections with coincidence logic or summing circuits can be provided for a portion of the signal outputs of the pixel elements as required. For example, an independent configuration of spatial resolution and spectral resolution can thus be achieved by partially transmitting the digital pixel signals of the pixel elements with full spatial resolution, while another portion of the digital pixel signals of the pixel elements can be calculated using the pixel signals of other pixel elements.

[0042] Likewise, different signal processing chains can be configured for the digital pixel signals of pixel elements that are subject to different boundary conditions. For example, a pixel element that is arranged at the edge within a matrix arrangement of pixel elements and thus has fewer directly adjacent pixel elements can be configured differently from a pixel element that is arranged in the middle.

[0043] According to an advantageous design variant of the photon counting X-ray detector, the plurality of digital logic elements includes at least one counting element and one reading element.

[0044] Thus, a simple photon counting X-ray detector may be provided in the simplest configuration of an X-ray detector.

[0045] The counting element can in particular comprise a counter which is designed to increase the count reading of the counter by one count unit based on the input signal. Here, the counting element can in particular comprise a plurality of counters. Thus, the counting element can be a resource block with a plurality of counters, so that the number of generated digital pixel signals can be counted based on a plurality of signal outputs and stored at least temporarily.

[0046] Instead of, for example, 4 counters per pixel element, a configurable resource block, ie counting elements, with 48 counters may for example be provided, which resource block may be used by a group of, for example, 16, pixel elements in a commonly configurable manner.

[0047] The count readings of the counting element can then be read out by means of a reading element, so that an X-ray image data set can be generated based thereon.

[0048] According to another preferred embodiment of the photon counting X-ray detector, the plurality of digital logic elements further comprises at least one element from the following list:

[0049] – coincidence logic,

[0050] – signal delay elements,

[0051] – cushioning elements,

[0052] – a switching element to prevent paralysis of the counting element,

[0053] – Combinational logic gates,

[0054] – Multiplexer,

[0055] – register elements,

[0056] – a component that, when triggered, generates a pulse of fixed or configurable length, or

[0057] – A component that measures the timing or duration of a trigger.

[0058] Advantageously, a preferred interconnection mode of the X-ray detector can be achieved. The plurality of digital logic elements particularly comprises a combination of elements in the list. In addition, other types of digital logic elements can also be provided.

[0059] Furthermore, it can be provided that a digital logic element from a plurality of digital logic elements is provided multiple times in the second signal processing stage.

[0060] Depending on the intended use and in accordance with the available space and available power, corresponding digital logic elements may be present in different selections and quantities. A suitable signal processing chain may advantageously be provided for the signal output.

[0061] In another embodiment of the photon counting X-ray detector according to the present invention, after configuration of the configurable switching matrix, non-interconnected digital logic elements of the plurality of digital logic elements are disconnected from the power supply.

[0062] Advantageously, unused logic elements can be switched off. For example, this can be preset and configured by means of settable register parameters. Advantageously, energy-efficient X-ray detectors adapted to the application and boundary conditions can be provided. In addition, the same evaluation unit can also be used for applications / products in which the available power / cooling budget is less by targeted energy-saving use of resources. Alternatively, the available performance and functional scope of the evaluation unit can be increased in a simple manner and afterwards by optimizing the cooling budget. Therefore, the present invention advantageously enables the same evaluation unit to be used in different products and / or applications, thereby enabling flexible use.

[0063] According to another design variant of the photon counting X-ray detector, the plurality of pixel elements are divided into a plurality of groups of pixel elements, wherein a configurable switching matrix is ​​respectively assigned to each group.

[0064] For example, a group can be assigned to an ASIC respectively. However, multiple pixel groups can be assigned to an ASIC. A group can also include different selections of pixel elements, for example, a group can be defined by the arrangement relative to an anti-scatter grid (ASG, "Anti-Scatter-Grid"). For example, a group includes ASG pixel groups that are respectively assigned to the through channels of the ASG. Other grouping methods are also possible. For example, the corresponding groups can each include a fixed number of pixel elements, which have a similar relationship with each other. For example, the relationship is given by their arrangement relative to each other. For example, a group of pixel elements respectively includes a union (Verbund) of 8×8 or 16×16 pixel elements. This union can also be called a macropixel, wherein the signals of the united pixel elements are preferably calculated together when necessary.

[0065] By dividing the plurality of pixel elements into a plurality of groups of pixel elements which are respectively assigned to one switching matrix, the complexity of the corresponding switching matrix or the complexity of the configuration of the switching matrix can advantageously be kept at a low level.

[0066] Furthermore, the configuration of the switching matrix can advantageously be transferred to a plurality of switching matrices in a simple manner.

[0067] According to an alternative design variant of the photon counting X-ray detector, the plurality of pixel elements is divided into a plurality of groups of pixel elements, wherein the plurality of groups are assigned a common configurable switching matrix.

[0068] Interconnection and signal exchange can advantageously be achieved between groups of pixel elements in a simplified manner. For example, coincidence considerations across groups of pixels can be achieved in a simplified manner. The groups can be defined, for example, by common external parameters. For example, the groups can include ASG pixel groups or macro pixels, respectively.

[0069] In this context, in one advantageous variant it may again be provided that the configurable switching matrix can be configured on a group basis.

[0070] For example, in the switching matrix, the same number and selection of digital logic elements are similarly arranged for each pixel group. For example, the configuration of a sub-matrix of the switching matrix can be transferred to the rest of the switching matrix on a group basis, that is, the configuration can be copied and applied on a group basis.

[0071] In another embodiment of the photon counting X-ray detector according to the present invention, the evaluation unit provides at least one first area for a first processing stage and a second area for a second processing stage, wherein at least one first area is arranged in the form of an island within the second area or along the second area on the edge side.

[0072] By decoupling the first, essentially analog, signal processing stage and the second, digital signal processing stage, a more flexible arrangement of the digital and analog parts of the signal processing and a more flexible floorplanning (planning the arrangement of partial circuits in the evaluation unit) can be achieved. Thus, it is advantageously possible to achieve a pixel-specific circuit (i.e., the corresponding first signal processing stage) that is designed to be smaller in area, and furthermore, a smaller pixel element pitch can be achieved.

[0073] Specifically, the decoupling of the first signal processing stage and the second signal processing stage advantageously makes it possible, for example, to embed the evaluation unit area provided for the first signal processing stage of the corresponding pixel element in the form of an island in the area providing the digital signal processing stage for at least one group of pixel elements. It can also be provided that the surface areas of the first signal processing stage of a group of pixel elements are combined to form a strip, a center or a ring. For example, the first signal processing stage can be respectively combined and arranged to be arranged along the second area provided for the second signal processing stage on the edge side. For example, the first signal processing stage can be respectively combined and arranged to be in the middle of the second area, which is provided for the second signal processing stage.

[0074] According to another embodiment variant of the photon counting x-ray detector, the evaluation unit is designed in layers, wherein a first processing stage is provided in a first layer and a second processing stage is provided in a second layer located downstream of the first layer in the radiation incidence direction.

[0075] Thus, for example, a first pixel-specific signal processing stage, which can be designed to be smaller in terms of area, can advantageously enable a smaller pixel element pitch.

[0076] In its improved solution, the division of analog circuits and digital circuits, i.e., the division of the corresponding first processing stage and second processing stage, is arranged in independent wafer dies (independent sub-areas of one or different semiconductor wafers). By dividing into independent dies in this way, it is possible to combine them into an evaluation unit in a die stacking process (Die-Stacking Process). When the first signal processing stage and the second signal processing stage are provided in independent dies, the analog circuits and the digital circuits are no longer bound to the same technology, so that, for example, different structural sizes can be used when providing, so that they can also be optimized independently of each other. In this way, for example, different pixel sizes can also be realized while the realization of the second signal processing stage remains the same.

[0077] According to one embodiment variant, the photon counting X-ray detector according to the invention can have a redistribution wiring layer between the converter element and the evaluation unit along the X-ray incidence direction.

[0078] The rewiring layer in particular comprises an electrically conductive connection which converts a first spatial distribution of the input contact elements into a second spatial distribution of the output contact elements. By providing the rewiring layer, the positions of the sensor pixel electrodes and the pixel electrodes of the evaluation side can advantageously be decoupled, thereby enabling a flexible arrangement of the areas allocated to the circuit parts (i.e. the first signal processing stage and the second signal processing stage of the respective pixel element group).

[0079] Furthermore, the present invention also relates to a medical imaging device having a photon counting X-ray detector according to the present invention.

[0080] Here, the features and advantages of photon counting X-ray detectors can be directly transferred to medical imaging equipment.

[0081] The medical imaging device can be designed in particular as a medical X-ray device. The medical imaging device can in particular comprise an X-ray source to which a photon counting X-ray detector is assigned for exposing the X-ray detector. The medical imaging device generally comprises at least one photon counting X-ray detector according to the invention and at least one X-ray source, such as an X-ray tube, arranged opposite thereto. In order to record an X-ray image data set, the object to be imaged can be placed in particular between the X-ray source and the photon counting X-ray detector and transmitted by means of the X-ray source.

[0082] The medical imaging device can in particular be designed as a computed tomography system. However, the medical imaging device can also be designed, for example, as a C-arm X-ray device and / or a Dyna-CT or other type.

[0083] The invention further relates to a method for operating a photon counting X-ray detector, which is designed according to one of the above-mentioned variants for generating an X-ray image data set, wherein at least one switching matrix can be configured via settable register parameters, the method comprising the following steps:

[0084] a. adjusting the configurable register parameters based on the first combination of register parameter values,

[0085] b. configuring at least one configurable switching matrix based on the adjusted register parameters, thereby providing a digital processing chain for at least a portion of the signal output ends of the first signal processing stage of at least one group of pixel elements, respectively, the at least a portion of the signal output ends being coupled to the at least one switching matrix for transmitting signals,

[0086] c. receiving X-ray radiation by means of an X-ray detector, generating an electrical signal in a converter element based on the X-ray radiation,

[0087] d. processing the generated electrical signals by means of a first processing stage and a second processing stage of the photon counting X-ray detector, wherein a digital pixel signal is provided at a respective signal output of the first signal processing stage of one pixel element of at least one group of pixel elements of the plurality of pixel elements, the digital pixel signal being further processed in the second signal processing stage by means of a digital processing chain provided for the respective signal output,

[0088] e. Output the processed digital pixel signal, and obtain the X-ray image data set based on the processed digital pixel signal.

[0089] In this case, an X-ray detector is assigned to an X-ray source for emitting X-ray radiation.

[0090] By virtue of the possibility of adjusting the register parameter values ​​of the register parameters, the logic of the switching matrix can advantageously be parameterized and thus adjusted in a simple and reproducible manner for different measurements and / or applications.

[0091] In one embodiment variant of the method according to the invention, in a second adjustment step, the settable register parameters are adjusted based on a second set of register parameter values, wherein in a second configuration step of at least one configurable switching matrix, a second digital processing chain is provided for at least a part of the signal output ends of a first signal processing stage of at least one group of pixel elements with the aid of the second set of register parameter values, the second digital processing chain being different from the first digital processing chain.

[0092] According to an advantageous method variant, the first set of register parameter values ​​and / or the second set of register parameter values ​​are determined as a function of the X-ray application.

[0093] The choice of the X-ray application (e.g. with regard to the object to be examined, a specific recording area, an application procedure, or a specific recording modality) largely determines the recording conditions during the recording of the X-ray image data set, as well as the desired image quality and / or the image information to be acquired.

[0094] Thus, determining register parameter values ​​according to the X-ray application may advantageously allow the X-ray detector to be advantageously adjusted as required.

[0095] In the scope of the present invention, the features described in different embodiments of the present invention and / or different claim categories (methods, uses, devices, systems, components, etc.) can be combined into other embodiments of the present invention. For example, claims related to devices can also be improved by combining the features described or claimed in the method, and vice versa. The functional features of the method can be implemented by specific components of the corresponding structure. In addition to the embodiments of the present invention clearly described in this application, various other embodiments of the present invention that can be implemented by those skilled in the art can be imagined without departing from the scope of the present invention given in advance by the claims.

[0096] The use of the indefinite article "a" or "an" does not exclude that the feature in question may also exist in multiple forms. The use of the expression "having" does not exclude that the terms linked by the expression "having" may be identical. For example, a medical imaging device has a medical imaging device. The use of the expression "unit" does not exclude that the object to which the expression "unit" relates may have a plurality of components that are spatially separated from one another.

[0097] In the context of the present application, the expression “based on” can be understood in particular in the sense of the expression “by using”. In particular, the expression “generating (alternatively, seeking, determining, etc.) a first feature based on a second feature” does not exclude generating (alternatively, seeking, determining, etc.) the first feature based on a third feature. BRIEF DESCRIPTION OF THE DRAWINGS

[0098] The invention is described below with reference to the accompanying drawings by means of exemplary embodiments. The illustrations in the drawings are schematic, greatly simplified and not necessarily drawn to scale. In particular:

[0099] Figure 1 An exemplary embodiment of an X-ray detector 1 is schematically shown,

[0100] Figure 2 A schematic diagram for explaining the interconnection of a group of pixel elements 5 with a first signal processing stage and a second signal processing stage for transmitting signals is shown,

[0101] Figure 3 A schematic diagram for explaining the interconnection of a plurality of groups of pixel elements 5 with a first signal processing stage and a second signal processing stage for transmitting signals is shown,

[0102] Figure 4 shows a schematic diagram for illustrating the interconnection of a group of pixel elements 5 with an exemplary processing chain according to a first configuration variant for transmitting signals,

[0103] Figure 5 shows a schematic diagram for illustrating the interconnection of a group of pixel elements 5 with an exemplary processing chain according to a second configuration variant for transmitting signals,

[0104] Figure 6 shows a schematic diagram for illustrating a group of pixel elements 5 interconnected with an exemplary processing chain according to a third configuration variant for transmitting signals,

[0105] Figures 7 to 10 An exemplary relative arrangement of evaluation unit areas provided for a first processing stage and a second processing stage, respectively, is shown,

[0106] Fig.11 An exemplary medical imaging device is shown, and

[0107] Fig.12 A schematic method flow of a method for operating a photon counting X-ray detector to generate an X-ray image dataset is shown. DETAILED DESCRIPTION

[0108] Figure 1 An exemplary embodiment of an X-ray detector 1 is schematically shown.

[0109] In this example, the X-ray detector 1 according to the invention is part of a detector module having a plurality of X-ray detectors 1 according to the invention. In a preferred embodiment, the detector module has a two-dimensional matrix or arrangement of a plurality of X-ray detectors 1. The respective X-ray detector 1 in turn has a plurality of pixel elements 5 arranged in a matrix.

[0110] In the example shown, the corresponding X-ray detector 1 has a converter element 3. The converter element 3 can be designed as a planar direct converter, for example with CdTe, CZT, CdZnTeSe, CdTeSe, CdMnTe, InP, TlBr2, HgI2, GaAs, Si or other materials as converter materials. The upper side of the converter element 3 has a first electrode 18 (top electrode). The lower side of the converter element 3 has a sensor pixel electrode 16. The sensor pixel electrode 16 is connected to an evaluation unit 59 via a conductive connection 69 and a pixel electrode 57. The evaluation unit 59 can include, for example, an ASIC ("Application Specific Integrated Circuit". The conductive connection 69 can be designed, for example, as a solder ball ("bump bonds") or a solder material connected to a copper pillar ("copper pillars"), or it can also be designed in other ways. The total number of sensor pixel electrodes 16, the number of conductive connections 69, the number of pixel electrodes 57 and the number of pixel elements 5 are usually the same. The electric field between the first electrode 18 and the respective sensor pixel electrode 16 determines a sensitive detection volume in the converter element 3 which is respectively assigned to one pixel element 5 of the plurality of pixel elements 5 .

[0111] In the example shown, according to an advantageous embodiment, a redistribution wiring layer 65 , also referred to as an intermediate layer, is also arranged between the converter element 3 of the respective x-ray detector 1 and the evaluation unit 59 .

[0112] The rewiring layer 65 comprises, in particular, electrically conductive connections which convert a first spatial distribution of the input contact elements into a second spatial distribution of the output contact elements. The input contact elements of the rewiring layer 65 are arranged, in particular, on the side of the rewiring layer 65 facing the sensor pixel electrodes 16 and are coupled to the sensor pixel electrodes 16 for signal transmission. The output contact elements are arranged, in particular, on the side of the rewiring layer 65 facing the pixel electrodes 57 of the evaluation unit 59 and are coupled to the pixel electrodes 57 for signal transmission. In this case, the spatial distribution of the input contact elements corresponds substantially to the spatial distribution of the sensor pixel electrodes 16. The spatial distribution of the output contact elements then corresponds substantially to the pixel electrodes 57 of the evaluation unit 59. The rewiring layer 65 can also be applied in direct contact to the converter element 3 or in direct contact to the evaluation unit 59.

[0113] In the example shown, the redistribution layer 65 extends over a plurality of evaluation units 59 and the converter element 3. This can be particularly advantageous for the stability of the X-ray detector. However, other embodiments are also possible. Likewise, a variant embodiment is conceivable in which a plurality of evaluation units 59 are assigned to a common converter element 3 designed as a plane.

[0114] Furthermore, the X-ray detector 1 or the X-ray detector module may also include other components not shown here, such as a substrate or peripheral electronic devices.

[0115] The evaluation unit 59 is designed for processing electrical signals caused by the X-ray radiation incident on the converter element 3. According to the invention, each pixel element 5 of the plurality of pixel elements 5 of the X-ray detector 1 has a first signal processing stage for processing the electrical signals, in particular a pixel-by-pixel first signal processing stage, wherein a digital pixel signal is provided at a respective signal output 7 of the first signal processing stage of a respective pixel element 5 of the plurality of pixel elements.

[0116] According to the invention, the signal output 7 of the first signal processing stage of at least one group of 20 pixel elements 5 of the plurality of pixel elements 5 is further coupled to a common second signal processing stage for signal transmission. The second signal processing stage is then used in particular for further digital processing of the provided digital pixel signals of the group of 20 pixel elements 5.

[0117] Figure 2 A schematic diagram is shown in a highly abstract form to illustrate that a group of 20 pixel elements 5 of a plurality of pixel elements 5 are interconnected with a first signal processing stage and a second signal processing stage for transmitting signals.

[0118] The number of pixel elements 5 in the group 20 is hereby merely exemplary and is selected for illustration purposes only. A group 20 may also be assigned more or fewer pixel elements 5 .

[0119] The sensor pixel electrodes 16 assigned to the respective pixel elements 5 in the group 20 are coupled for signal transmission to a first signal processing stage provided in the evaluation unit 59. Each pixel element 7 has in particular a pixel-by-pixel first signal processing stage.

[0120] The first signal processing stage of the pixel elements 5 for processing the signal fed by the converter element 3 each has at least one signal amplifier 17 and at least one comparator 19. The comparator has at least one settable threshold value THR.

[0121] The signal input via the pixel electrode is amplified in the first signal processing stage of the pixel element 5 by means of a signal amplifier 17, and the amplified signal is compared with at least a threshold value THR representing an energy threshold by means of at least one comparator 19. In the case where the signal exceeds the threshold value THR, the output signal is output at the signal output terminal 7. In particular, a digital pixel signal is provided at the signal output terminal 7 of the first signal processing stage.

[0122] The first signal processing stage of one pixel element 5 among the multiple pixel elements 5 may also have more than one comparator 19, and these comparators 19 respectively have a threshold THR, so that multiple digital pixel signals can be provided at multiple signal output terminals 7 of one pixel element 5 among the multiple pixel elements 5 according to multiple thresholds THR.

[0123] The signal output terminal 7 of the first signal processing stage of at least one group 20 of the plurality of pixel elements 5 is further coupled to a common second signal processing stage for transmitting a signal.

[0124] The common second signal processing stage has a plurality of digital logic elements 9 for digital processing of the digital pixel signals provided at the signal output terminal 7. The plurality of digital logic elements 9 provided in the second signal processing stage can be understood as common resource elements provided for digital signal processing of digital pixel signals, which can be used together for signal processing of digital pixel signals of the pixel elements 5 of the group of the plurality of pixel elements.

[0125] In addition, the common second signal processing stage includes a configurable switching matrix 11 for interconnecting at least a portion of the plurality of digital logic elements 9 with corresponding signal output terminals 7 of the first signal processing stage of a group 16 of pixel elements 5 among the plurality of pixel elements 5 for signal transmission.

[0126] After configuration of the switching matrix 11 , a processing chain for digital processing of the provided digital pixel signals can then be provided for each signal output 7 of the first signal processing stage of a group 16 of pixel elements 5 of the plurality of pixel elements 5 .

[0127] Hence, the processing chain may in particular represent a selected interconnection and series connection of digital logic elements 9 and of corresponding signal outputs 7 , whereby digital processing of the digital pixel signals output at the signal outputs 7 is achieved by the interconnection.

[0128] The switch matrix 11 can be designed to be similar to an FPGA (field-programmable gate array). That is, the switch matrix 11 can be designed as an integrated circuit in which a logic circuit can be loaded, wherein the desired circuit structure (the timing and the regulation) can be defined or adjusted by programming or configuring the switch matrix 11.

[0129] The selection of digital logic elements 9 here includes at least a portion of the provided digital logic elements 9. The logic elements can be interconnected to one or more signal outputs 7 of the first signal processing stage and / or to one or more digital logic elements 9 respectively.

[0130] Here, according to one configuration, a first processing chain may be provided for a first number of signal outputs 7 of the group of 16 pixel elements 5 , and a second processing chain different from the first processing chain may be provided for a second number of signal outputs 7 .

[0131] Furthermore, according to a further advantageous embodiment variant, the configurable switching matrix 11 can also be configured, in particular by means of settable register parameters, so that different digital processing chains can be provided for the signal output 7 depending on the set register parameters.

[0132] According to a preferred design variant, the plurality of digital logic elements 9 here comprises at least one counting element 13 and one reading element 14 .

[0133] Therefore, in the simplest configuration of the X-ray detector 1, a simple photon counting X-ray detector can be provided, which counts the number of signals directly input into the pixel element 5 according to the provided threshold THR of the corresponding pixel element 5, based on which an X-ray image data set can be created.

[0134] The counting element 13 may include a counter. The counter may be designed in particular to increase the count reading of the counter by one count unit when a signal is input. The counter may include, for example, a so-called "rising edge counter" or a "falling edge counter" (a counter based on the rising edge of a signal or a counter based on the falling edge of a signal). Here, the counting element 13 may preferably include a plurality of counters. Therefore, the counting element 13 may correspond to a resource block having a plurality of counters, so that, for example, based on a plurality of signal output terminals 7 coupled to the counting element 13, the number of generated digital pixel signals may be counted respectively and stored at least temporarily.

[0135] The count reading of the counting element 14 can then be read out by means of the reading element 14. The reading element 14 can comprise, for example, a shift register or a so-called readout tree.

[0136] In addition, according to a favorable embodiment variant, the plurality of digital logic elements 9 may also include at least one element from the following list: coincidence logic, signal delay elements, buffer elements, switch elements for preventing paralysis of counting elements, combinational logic gates, multiplexers, register elements, elements that generate pulses of fixed length or configurable length when triggered, and elements that measure the time point or duration of a trigger.

[0137] By providing at least one or more of the mentioned elements, an advantageous interconnection for the use of a photon counting X-ray detector may be achieved in an advantageous manner.

[0138] The coincidence logic enables, for example, the registration of coincidences between two or more pixel elements 5 of the plurality of pixel elements. The collection of coincidence information and the input of the coincidence information into the X-ray image data set may enable an improvement in spatial resolution and / or spectral resolution.

[0139] The signal delay element can be used in particular advantageously to compensate for signal differences between two digital pixel signals which are caused, for example, by different line lengths.

[0140] Switching elements for preventing paralysis can advantageously be used to improve the high-throughput performance of X-ray detectors.Such switching elements can cause a further signal if a comparator threshold is exceeded for a long time. Such a switching element can, for example, be designed as a pile-up trigger (see, for example, Kraft et al., “Experimental evaluation of the pile-uptrigger method in a revised quantum-counting CT detector”, Proc. SPIE 8313, Medical Imaging 2012: Physics of Medical Imaging, 83134A (2012); https: / / doi.org / 10.1117 / 12.911231) or as a so-called “instant retrigger” (Loeliger et al., “The new PILATUS3 ASIC with instant retrigger capability”, 2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS / MIC) (2012); https: / / doi.org / 610-615.10.1109 / NSSMIC.2012.6551180).

[0141] Combinatorial logic gates may include AND gates, NAND gates, OR gates, NOR gates, XOR gates or NOT gates. Based on this, different arithmetic functions or logic functions can be advantageously implemented, such as addition or subtraction of signals. In addition, components for data transmission, such as multiplexers, demultiplexers, encoders, decoders can be implemented.

[0142] The multiplexer can, for example, advantageously route a signal selected from a plurality of input signals to an output of the multiplexer.

[0143] The use of an element that generates a pulse of fixed or configurable length upon triggering allows for a so-called "time-out threshold" measurement (duration exceeding a threshold) well known in the field of photon counting detectors. An element that measures the time point or duration of a trigger can, for example, allow for a so-called "time-to-arrival" measurement (time of arrival of a signal) well known in the field of photon counting detectors. This can, for example, be advantageously used to collect coincidence information.

[0144] The register element can advantageously be configured by means of register parameters stored in the register element and can be synchronized and / or read out.

[0145] The buffer element can advantageously be provided for driving nodes with higher loads.

[0146] In addition, other types of logic elements may be provided. For example, a logic element may be provided that is triggered when a (specific or configurable) pattern appears on its input. Likewise, a connection element may be provided for one or more clock signals, or a monitoring element may be provided (e.g., a digital buffer for external observation of a signal).

[0147] Preferably, in the second signal processing stage, in particular, corresponding logic elements 9 of the plurality of logic elements 9 can also be provided multiple times. Then, depending on the intended use and the available space and available power, the corresponding digital logic elements 9 can be present in a suitable selection and number in order to advantageously provide a signal processing chain for a plurality of signal outputs 7.

[0148] Furthermore, in the planning and synthesis of the digital logic, it can also be advantageously ensured by appropriate layout or appropriate synthesis boundary conditions that typical connection paths and node impedances are optimized, especially in the fast switching region. For example, it can be advantageous to place the coincidence logic in a distributed manner between adjacent pixel elements 5, respectively.

[0149] For a resource-saving and energy-efficient X-ray detector 1 , it can advantageously be provided that, after configuration of the configurable switching matrix 11 , logic elements 9 of the plurality of logic elements 9 which are not interconnected are disconnected from the power supply.

[0150] According to another design variant of the photon counting X-ray detector 1, the plurality of pixel elements 5 are divided into a plurality of groups 20 of pixel elements 5, wherein each group 20 is respectively assigned a configurable switching matrix 11. For example, the groups can be respectively assigned to ASICs. A group can also have different selections of pixel elements 5, for example, ASG pixels or macro pixels.

[0151] Signal connections can also be provided between the groups 20 (ie between the switching matrices), so that, for example, signal exchanges across the groups can also be carried out to take overlaps into account.

[0152] like Figure 3 As schematically shown in FIG. 1 , multiple groups 20 of pixel elements 5 can also be assigned to one switching matrix 11 . That is, multiple pixel elements 5 are divided into multiple groups 20 of pixel elements 5 , wherein multiple groups 20 are jointly assigned one configurable switching matrix 11 .

[0153] However, it can preferably be provided here that the configurable switching matrix 11 can be configured in a group-based manner, so that the configuration of a submatrix of the switching matrix can be copied in a group-based manner to the remaining switching matrices.

[0154] In this case, provision can be made for each group to be repeatedly provided with the same number and selection of digital logic elements (defined by Figure 3 ), so that for each group 20 of pixel elements the same signal processing chain can be configured for the digital pixel signal by means of the switching matrix 11.

[0155] Multiple feasible schemes for signal processing are obtained by the configurability of the switching matrix 11 and the configurability of the signal processing chain. Therefore, the selection and interconnection of the logic elements can be adapted to the X-ray application: when the X-ray flux is very low, such as in the case of screening applications, for example, a configuration with weighted pixel fusion (merging of digital pixel signals of multiple pixel elements) or a configuration with maximum spatial resolution and / or spectral resolution can be advantageous. In high-throughput applications, the use of coincidence logic can be activated, for example, to reduce or measure the negative effects of charge sharing / pulse pile-up. In the case of examinations requiring high spatial resolution (for example, in the case of auditory examinations or osteoporosis), the following configuration can be advantageous, which uses counter resources to maximize spatial resolution and measures the signal according to a smaller number of spectral thresholds for this purpose. In the case of examinations that tend to require high soft tissue contrast or precise material identification, the opposite configuration (reducing noise by smaller spatial resolution, weighted pixel fusion, a high number of spectral thresholds or spectral weighting) can be advantageous. In the case of time-critical examinations (for example, in cardiology or the emergency room), measurements with a maximum image frequency may be required in order to minimize scan duration and motion artifacts. This can be achieved by a configuration with a minimum amount of data. For example, the amount of raw data can be reduced by reducing the spectral and spatial resolution (by combining adjacent pixels). This can be achieved, for example, by summing the comparator signals of adjacent pixels or by adding adjacent counter readings directly on the chip. In addition to making it possible to make the read intervals shorter, this has the advantage in particular that the power consumption during the readout is also reduced. In the case of examinations with unclear or multi-morbid questions (patients with multiple diseases), a configuration that offers a slower speed but can provide the maximum amount of information in a single scan can be advantageous.

[0156] Furthermore, the spatial resolution and the spectral resolution may also be configured independently of each other. A specific example may generally include measuring the first and second thresholds at full spatial resolution, but measuring the third threshold at only half the spatial resolution, but setting the idle counter resource for the coincidence counter in conjunction with the first threshold.

[0157] In addition, the flexibility and performance of the coincidence circuit can be advantageously provided in an improved manner. Through flexible interconnection, higher-order coincidences can also be obtained, depending on the application, such as the coincidence of a second higher energy threshold THR in a pixel element with a signal with a first lower energy threshold of an adjacent pixel.

[0158] Figure 4 A schematic diagram for illustrating the interconnection of a group of 20 pixel elements 5 for transmitting signals is shown, wherein an exemplary processing chain according to a first configuration variant is shown.

[0159] In this illustration, in particular by means of blocks, only the digital logic elements 9 which are interconnected in this simplified variant are shown. Furthermore, further logic elements 9 which are not shown here can be provided in the second signal processing stage.

[0160] In this variant, the pixel-by-pixel first signal processing stage of the respective pixel element 5 has three comparators 19 and respectively three signal outputs 7. Each signal output 7 of the pixel elements of the group 20 is coupled to a common second signal processing stage having a configurable switching matrix 11 and a plurality of logic elements 9.

[0161] The signal output terminals 7 of the corresponding first comparators and second comparators 19 of each pixel element 5 are interconnected with a counting element 13 having a plurality of counters, so that the number of digital pixel signals can be counted respectively according to the threshold THR based on the output signals of the corresponding first comparators and second comparators 19 .

[0162] In addition, the signal output terminal 7 of the corresponding third comparator 19 of the pixel element 5 is interconnected with the counting element 13 together with the corresponding signal output terminal 7 of the adjacent pixel element 5 via the summing element 18, so that the total number of pixel signals of every two adjacent pixel elements 5 is counted according to the threshold THR of the corresponding third comparator 19.

[0163] As a result, in this configuration variant, based on the first comparator threshold and the second comparator threshold THR, the digital pixel signal is counted with a complete spatial resolution, while the third comparator threshold THR is measured only with half the spatial resolution. Here, it is assumed that the threshold of the pixel signal is set identically. That is, on all pixel elements 5, the corresponding first comparator 19 has the same energy threshold, and the corresponding second comparator 19 and the corresponding third comparator 19 are also the same.

[0164] Additionally, in this example, each signal output terminal 7 is interconnected with an element for preventing the corresponding coupled counter from being paralyzed, so as to improve high-throughput performance.

[0165] Figure 4A schematic diagram for illustrating the interconnection of a group of 20 pixel elements 5 for transmitting signals is shown, wherein an exemplary processing chain according to a second configuration variant is shown.

[0166] In this variant, the pixel-by-pixel first signal processing stage of the corresponding pixel element 5 again has three comparators 19 and correspondingly three signal outputs 7. However, only the digital pixel signals provided based on the signal outputs 7 of the first two comparators 19 are further processed. For this purpose, the signal outputs 7 of the corresponding first comparators 19 of each two adjacent pixel elements 5 are additionally coupled to the coincidence logic 12.

[0167] Therefore, in this variant, the signal of each pixel element 5 based on the first two threshold values ​​is counted again by means of the counting element 13, and the signals that coincide between each two adjacent pixel elements 5 are also counted. In this example, the spectral resolution is omitted in order to collect the coincidence information between each two adjacent pixel elements 5 in return.

[0168] Figure 6 A schematic diagram for illustrating the interconnection of a group of 20 pixel elements 5 for transmitting signals is shown, wherein an exemplary processing chain according to a third configuration variant is shown.

[0169] In this case, the digital pixel signals of the corresponding comparators 19 of every two adjacent pixel elements 5 are combined by the summing logic 18 and counted by means of the counting element 13, so that although the spatial resolution is low, the data volume can be reduced, thereby achieving a fast recording frequency.

[0170] The above configuration variants show simple interconnections for exemplary purposes. In addition, more complex configuration variants can be implemented and derived from the variants in a simple manner.

[0171] Figures 7 to 9 A diagram showing an exemplary relative arrangement of regions of an evaluation unit 59 provided for a first processing stage and a second processing stage, respectively, is shown, the evaluation unit 59 providing the first processing stage and the second processing stage for at least one group 20 of pixel elements 5 of the plurality of pixel elements.

[0172] A region may be understood to be a planar region of the evaluation unit 59. A respective planar region 59 may be designed in particular in a plane perpendicular to the radiation incidence direction or perpendicular to the stacking direction of the stacked arrangement of converter elements 3 and evaluation unit 59.

[0173] According to an embodiment variant of the X-ray detector 1, the evaluation unit 59 can be provided with at least one first region 61 for a first processing stage and a second region 63 for a second processing stage, wherein the at least one first region 61 is arranged in the form of an island within the second region 63, as exemplarily shown in Figure 7 and Figure 8 As shown in .

[0174] However, according to an embodiment variant of the X-ray detector 1, the evaluation unit 59 can also provide at least one first region 61 for a first processing stage and a second region 63 for a second processing stage, wherein the at least one first region 61 is arranged along the second region 63 at the edge, as exemplarily shown in Fig. 9 As shown in .

[0175] like Figure 7 As shown, the region 61 of the evaluation unit 59 provided for the first signal processing stage of the corresponding pixel element 5 can be embedded in the form of an island in the region 63, which provides a digital signal processing stage for a group of 20 pixel elements. In this case, the region 63 of the digital signal processing stage can, for example, occupy the planar extension of the entire pixel group.

[0176] Likewise, it may be provided that the regions of the first signal processing stages of a group of pixel elements are also arranged in combination to form a strip, a center or a ring. For example, the first signal processing stages may be arranged in combination to be centered and island-shaped, such as Figure 8 For example, the first signal processing stages can be arranged in combination along the second region 63 at the edge side, as shown in FIG. Fig. 9 shown.

[0177] Fig.10 A diagram shows another exemplary relative arrangement of a first processing stage and a second processing stage, wherein the evaluation unit 59 is constructed in layers and wherein the first processing stage is provided in a first layer 62 and the second processing stage is provided in a second layer 64 which is located behind the first layer 62 in the radiation incidence direction 65.

[0178] In a development thereof, the division of analog and digital circuits, ie the respective first and second processing stages, is provided in separate wafer dies (separate sub-areas of one or different semiconductor wafers), which can then be combined to form an evaluation unit 59 .

[0179] Fig.11An exemplary embodiment of a medical imaging device according to the invention is shown in the form of a computed tomography system 32. The computed tomography system 32 has a gantry 33 with a rotor 35. The rotor 35 comprises a detector arrangement 2 and a radiation source 37, for example an X-ray tube, for exposing the detector arrangement 2. The detector arrangement 2 has at least one photon counting X-ray detector 1 according to the invention. The detector arrangement 2 can have a detector module comprising a plurality of X-ray detectors 1.

[0180] An object 39, here a patient, is supported on a patient couch 41 and can be moved through the gantry 33 along an axis of rotation z 43. In general, the object 39 can include, for example, an animal patient and / or a human patient.

[0181] In the case of a computed tomography system 32, (raw) X-ray image datasets of the object are usually recorded from multiple angular directions by means of an X-ray detector. The (raw) X-ray image dataset is essentially based on the processed digital pixel signals output. Then, based on the (raw) X-ray image dataset, a final X-ray image dataset, a volume image dataset, or a layer image dataset can be reconstructed by means of mathematical methods (for example, including filtered back projection or iterative reconstruction methods).

[0182] In order to control the medical imaging device and / or to create an X-ray image data set based on the measurement data recorded by the photon counting X-ray detector 1 , ie the processed digital pixel signals, a system controller in the form of a computing unit 45 is provided.

[0183] The operation unit 45 may include a control unit 53, which may be designed to adapt the register parameter values ​​of the register parameters to the configuration of the configurable switching matrix of the photon counting X-ray detector 1. To this end, the control unit 53 may be coupled to at least one X-ray detector via a control interface to transmit control instructions and / or register parameter values. In addition, the control unit may also be designed to determine a set of register parameter values ​​according to the X-ray application, or to query and / or obtain application parameters for determining a suitable set of register parameter values.

[0184] The control unit 53 and / or the computing unit 45 can be implemented in the form of a computer, a microcontroller or an integrated circuit. The control unit 53 and / or the computing unit 45 can have hardware elements or software elements, such as a microprocessor or a so-called FPGA (English abbreviation for "Field Programmable Gate Array"). The control unit 53 and / or the computing unit 45 can also be a real or virtual combination of computers (the term for real combination is "cluster" and the term for virtual combination is "cloud").

[0185] In addition, an input device 47 and an output device 49 are connected to the computing unit 45. The input device 47 and the output device 49 can, for example, enable interaction, such as manually adjusting register parameter values, inputting parameters based on which register parameter values ​​can be determined, and confirming or triggering method steps by the user. In addition, the medical imaging device can also include a storage unit 55.

[0186] Fig.12 A schematic method flow is shown for a method for operating a photon counting X-ray detector 1 which is designed according to one of the above-described variants and is used for recording X-ray image data sets, wherein at least one switching matrix 11 can be configured via settable register parameters.

[0187] The method comprises the following steps: adjusting S1 a settable register parameter based on a first set of register parameter values.

[0188] The method further comprises step S2: configuring at least one configurable switching matrix 11 based on the adjusted register parameters, so as to provide digital processing chains for at least a part of the signal output terminals 7 of the first signal processing stage of at least one group of 20 pixel elements 5, respectively, and these signal output terminals 7 are coupled to at least one switching matrix 11 for transmitting signals. This also includes providing digital processing chains for all signal output terminals 7 of the first signal processing stage of at least one group of 20 pixel elements 5, respectively, and these signal output terminals 7 are coupled to at least one switching matrix 11 for transmitting signals.

[0189] The method also includes the step of receiving X-ray radiation using the X-ray detector 1, based on which electrical signals are generated in the converter element 3, and in the step of processing S4, these electrical signals are processed with the aid of the first processing stage and the second processing stage of the X-ray detector 1, wherein digital pixel signals are provided at the corresponding signal output terminal 7 of the first signal processing stage of a pixel element 5 of at least one group of 20 pixel elements 5 among the plurality of pixel elements 5, and these digital pixel signals are further processed in the second signal processing stage with the aid of the digital processing chain provided for the corresponding signal output terminal 7.

[0190] The method further comprises the step of outputting the digital pixel signal processed in S5, and obtaining an X-ray image data set based on the digital pixel signal.

[0191] According to an improvement of the method according to an implementation variant of the method of the present invention, in a second adjustment step S6, the settable register parameters can be adjusted based on a second set of register parameters, and wherein in a second configuration step S7 of at least one configurable switching matrix 11, a second digital processing chain different from the first digital processing chain is provided for at least a part of the signal output terminals 7 of the first signal processing stage of at least one group 20 pixel elements 5 of the plurality of pixel elements 5 with the aid of the second set of register parameter values.

[0192] According to an advantageous method variant, the first set and the second set of register parameters can be determined according to the X-ray application. The X-ray detector 1 can advantageously be optimally adapted to the current boundary conditions of the recording of the X-ray image data set and the requirements of the X-ray application. In this case, the X-ray detector can be adjusted very flexibly.

[0193] For example, multiple sets of register parameter values ​​may be pre-stored externally in the storage unit 55 or also in multiple register elements of the switching matrix 11 itself. Then, one set may be determined and used from the multiple sets of register parameter values ​​according to the X-ray application.

[0194] Here, the set of register parameter values ​​can be associated with one or more application parameters related to the X-ray application, for example. For example, the application parameters can be based on the X-ray flux, the time point or duration, the control parameters of the medical imaging device (e.g., the X-ray tube current or the X-ray tube voltage), the image parameters of the X-ray image data set to be recorded (e.g., the spectral resolution or the spatial resolution). Then, a favorable set of register parameter values ​​can be determined with the help of the application parameters.

[0195] The application parameters can be queried, for example, by an external storage unit 55, an external sensor unit or a control unit 53 with the aid of the X-ray detector 1. The application parameters can be measured or determined, for example, by the X-ray detector 1 itself, such as the X-ray flux or the X-ray radiation energy. Then, based on the queried and / or determined application parameters, a set of register parameter values ​​can be determined and selected for the configuration of the switching matrix 11. The application parameters can also be queried and / or determined by the control unit 53 coupled to the X-ray detector 1, and then the control instructions and / or new register parameter values ​​can be transmitted to the X-ray detector 1 via the control interface.

[0196] In addition to application parameters related to the X-ray application, there may be other application parameters, for example, they may also be based on boundary conditions preset by a medical imaging device to which the X-ray detector 1 according to the invention is assigned, such as available cooling power or power supply.

[0197] Advantageously, the X-ray detector 1 can be configured simply and, if appropriate, automatically, so that the X-ray detector 1 configuration which is most advantageous for the X-ray application, the given boundary conditions of the medical imaging device and / or the measurement can always be provided.

Claims

1. A photon counting X-ray detector (1) comprising a converter element (3) and a plurality of pixel elements (5), wherein the converter element is used to convert X-ray radiation into electrical signals, wherein: a. each pixel element (5) of the plurality of pixel elements (5) has a first signal processing stage for processing the electrical signal, the first signal processing stage respectively having at least one signal amplifier (17) and at least one comparator (19) for providing a digital pixel signal at a corresponding signal output terminal (7) of the first signal processing stage of a pixel element (5) of the plurality of pixel elements (5), b. the signal output terminal (7) of the first signal processing stage of at least one group (20) of the plurality of pixel elements (5) is coupled to a common second signal processing stage for signal transmission, the common second signal processing stage having a plurality of digital logic elements (9) for digitally processing the provided digital pixel signals, c. the common second signal processing stage has a configurable switching matrix (11) for interconnecting at least a portion of the plurality of digital logic elements (9) with corresponding signal output terminals (7) of the first signal processing stage of the group (20) of pixel elements (5) of the plurality of pixel elements (5) for signal transmission, d. enabling, after configuring the switching matrix (11) for each signal output terminal (7) of the first signal processing stage of the group (20) of pixel elements (5) of the plurality of pixel elements (5), a processing chain for digitally processing the provided digital pixel signal to be provided, The first signal processing stage is formed by a pixel-by-pixel electronic device, so that the first signal processing stage, the corresponding pixel electrode and sensor pixel electrode and the detection volume in the converter element (3) can be assigned to one pixel element (5) of the multiple pixel elements (5) respectively, while the second signal processing stage as a whole can be assigned only to the group (20) of pixel elements (5), and the detection volume is formed by the electric field between the corresponding sensor pixel electrode and the top electrode mounted on the opposite side of the converter element.

2. A photon counting X-ray detector (1) according to claim 1, wherein a first processing chain can be provided for a first number of signal output ends (7) of the group (20) of pixel elements (5), and wherein a second processing chain can be provided for a second number of signal output ends (7), the second processing chain being different from the first processing chain.

3. The photon counting X-ray detector (1) according to claim 1 or 2, wherein the plurality of digital logic elements (9) comprises at least one counting element (13) and one reading element (14).

4. The photon counting X-ray detector (1) according to claim 3, wherein: The plurality of digital logic elements (9) further comprises at least one element selected from the following list: – coincidence logic, – signal delay elements, – cushioning elements, – a switching element to prevent paralysis of the counting element, – Combinational logic gates, – Multiplexer, – Register elements, – components that, when triggered, generate pulses of fixed or configurable length, – A component that measures the timing or duration of a trigger.

5. The photon counting X-ray detector (1) according to claim 1 or 2, wherein in the second signal processing stage, one digital logic element (9) of the plurality of digital logic elements (9) is provided a plurality of times.

6. The photon counting X-ray detector (1) according to claim 1 or 2, wherein after configuration of the configurable switching matrix (11), non-interconnected digital logic elements (9) among the plurality of digital logic elements (9) are disconnected from a power supply.

7. The photon counting X-ray detector (1) according to claim 1 or 2, wherein the plurality of pixel elements (5) are divided into a plurality of groups (20) of pixel elements (5), wherein each group (20) is respectively assigned a configurable switching matrix (11).

8. The photon counting X-ray detector (1) according to claim 1 or 2, wherein the plurality of pixel elements (5) are divided into a plurality of groups (20) of pixel elements, wherein the plurality of groups (20) are assigned a common configurable switching matrix (11).

9. The photon counting X-ray detector (1) according to claim 8, wherein the one configurable switching matrix (11) can be configured in groups.

10. The photon counting X-ray detector (1) according to claim 1 or 2, comprising an evaluation unit (59), which provides the first signal processing stage and the second signal processing stage for at least one group (20) of pixel elements (5), and wherein the evaluation unit (59) provides at least one first area (61) for the first signal processing stage and one second area (63) for the second signal processing stage, wherein the at least one first area (61) is arranged in the form of an island within the second area (63) or is arranged along the second area (63) on the edge side.

11. The photon counting X-ray detector (1) according to claim 1 or 2, comprising an evaluation unit (59), which provides the first signal processing stage and the second signal processing stage for at least one group (20) of pixel elements (5), and wherein the evaluation unit (59) is constructed in layers, and wherein the first signal processing stage is provided in a first layer (62) and the second signal processing stage is provided in a second layer (64) located after the first layer (62) in the direction of incidence of the rays.

12. A medical imaging device having at least one photon counting X-ray detector (1) according to any one of the preceding claims.

13. A method for operating a photon counting X-ray detector (1), which is implemented according to any one of claims 1 to 11 for generating an X-ray image data set, wherein the at least one switching matrix (11) of the X-ray detector (1) can be configured by means of settable register parameters, the method comprising the following steps: a. adjusting (S1) the configurable register parameter based on a first set of register parameter values, b. configuring (S2) the at least one configurable switching matrix (11) based on the adjusted register parameters, thereby providing a first digital processing chain for at least a portion of the signal output terminals (7) of the first signal processing stage of the at least one group (20) of pixel elements (5), the at least a portion of the signal output terminals (7) being coupled to the at least one switching matrix (11) for transmitting signals, c. receiving (S3) X-ray radiation using the photon counting X-ray detector (1), generating an electrical signal in the converter element (3) based on the X-ray radiation, d. processing (S4) the generated electrical signal by means of the first signal processing stage and the second signal processing stage of the photon counting X-ray detector (1), wherein a digital pixel signal is provided at a corresponding signal output (7) of the first signal processing stage of a pixel element (5) in at least one group (20) of pixel elements (5) of the plurality of pixel elements (5), and the digital pixel signal is further processed in the second signal processing stage by means of the first digital processing chain provided for the corresponding signal output (7), e. Output (S5) the processed digital pixel signal, and generate an X-ray image data set based on the processed digital pixel signal.

14. A method according to claim 13, wherein in the second adjustment step (S6), the settable register parameters are adjusted based on a second set of register parameter values, and wherein in the second configuration step (S7) of the at least one configurable switching matrix (11), with the aid of the second set of register parameter values, a second digital processing chain is provided for at least a part of the signal output ends (7) of the first signal processing stage of the at least one group (20) of pixel elements (5), the second digital processing chain being different from the first digital processing chain.

15. The method of claim 14, wherein the first set of register parameter values ​​and / or the second set of register parameter values ​​are determined according to an X-ray application.

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