Evaluation unit for an X-ray detector, X-ray detector, medical imaging device and method for operating an X-ray detector

Abstract

Evaluation unit (1) for an X-ray detector (2) for signal-technical coupling to a converter unit (3) which is designed to convert incoming X-ray radiation into electrical signals, comprising a plurality of pixel electronics units (5), wherein a respective pixel electronics unit (5) is designed to process the electrical signals fed by the converter unit (3) into a respective pixel electronics unit (5) into a digital pixel measurement signal, and wherein each of the pixel electronics units (5) has at least one controllable, digital signal processing unit (7) which is designed to adapt a processed, digital pixel measurement signal in a respective pixel electronics unit (5), wherein the digital signal processing unit (7) of a respective pixel electronics unit (5) comprises a measured value memory (11) into which the digital pixel measurement signal can be transmitted, and the digital signal processing unit (7) is designed,to adapt the pixel measurement signal transferred to the measured value memory (11).

Description

[0001] The invention relates to an evaluation unit for an X-ray detector comprising a plurality of pixel electronics, wherein each of the pixel electronics has a controllable, digital signal processing unit which is designed to adapt a processed, digital pixel measurement signal in a respective pixel electronics, as well as an X-ray detector comprising an evaluation unit, a medical imaging device comprising an X-ray detector and a method for operating an X-ray detector.

[0002] X-ray detectors are used in many imaging applications. For example, X-ray detectors are used in computed tomography scanners in medical imaging to generate a tomographic X-ray image of a patient's examination area.

[0003] In X-ray imaging, for example in computed tomography, angiography or radiography, counting, direct-converting X-ray detector devices or integrating, indirect-converting X-ray detector devices can be used.

[0004] The X-rays or photons can be converted into electrical pulses in direct-conversion X-ray detector devices using a suitable converter material. Examples of converter materials include CdTe, CZT, CdZnTeSe, CdTeSe, CdMnTe, InP, TlBr2, HgI2, GaAs, or others. The electrical pulses can be evaluated by electronic circuits in an evaluation unit, for example, in the form of an integrated circuit (Application Specific Integrated Circuit, ASIC). In counting X-ray detector devices, the incident X-rays can be measured by counting the electrical pulses triggered by the absorption of X-ray photons in the converter material. The height of the electrical pulse is also usually proportional to the energy of the absorbed X-ray photon. This allows spectral information to be extracted by comparing the height of the electrical pulse with a threshold value.

[0005] The X-rays or photons can be converted into light by a suitable converter material in indirect-conversion X-ray detector devices, and then into electrical pulses using optically coupled photodiodes. Scintillators, such as GOS (Gd2O2S), CsJ, YGO, or LuTAG, are often used as converter materials. The generated electrical signals are further processed by an evaluation unit containing electronic circuits. Scintillators are used particularly in medical X-ray imaging in the energy range up to 1 MeV.

[0006] The electronic circuits of an X-ray detector device can, for example, be used for signal amplification, digitization (A / D converter, analog-to-digital converter), or other further processing of the electrical signals before forwarding them to a readout electronics unit, from which the processed data can be forwarded to a computing unit. The computing unit can then be configured to generate an X-ray image data set based on the forwarded processed signals.

[0007] X-ray detector devices, and in particular the converter units themselves, whether direct-converting or indirect-converting, can be subject to time-, radiation-, and / or temperature-dependent drift effects, which can impair the image quality of an image data set acquired using an X-ray detector device. Such drift effects can be reduced through complex material treatment and stabilization of the operating conditions. Furthermore, however, the possibility of correcting the digital measurement data output by the X-ray detector is desirable in order to further improve the measurement data sets generated with an X-ray detector, thus ensuring high-quality imaging.

[0008] US 8 772 730 82 discloses a photon counting detector having readout circuits configured to count photons of a multi-energy radiation with respect to a plurality of energy bands, the readout circuits each corresponding to pixels of an area onto which the multi-energy radiation is irradiated.

[0009] US 4 593 198 A discloses a pulse pile-up discrimination system for distinguishing between single and multiple emission detections for a multi-cell detector of a radionuclide emission scintillation camera.

[0010] The document US 2012 / 0 228 486 A1 discloses a radiation detector arrangement comprising a detector array configured to convert radiation particles into electrical detection pulses, and an application-specific integrated circuit (ASIC) operatively connected to the detector array and configured to digitize the electrical detection pulses.

[0011] The document US 2007 / 023 669 A1 discloses a method and apparatus for acquiring radiation data with a multimodality detector, wherein radiation events are counted for each pixel by means of an electronic module which is coupled to a respective pixel.

[0012] The object of the invention is to provide a possibility for an efficient adaptation of pixel measurement signals.

[0013] The problem is solved by the features of the independent patent claims. Further advantageous and partly inventive embodiments and developments of the invention are set forth in the subclaims and the following description.

[0014] The invention relates to an evaluation unit for an X-ray detector for signal-technical coupling to a converter unit, which is designed to convert incoming X-ray radiation into electrical signals. The evaluation unit comprises a plurality of pixel electronics units, wherein a respective pixel electronics unit of the plurality of pixel electronics units is designed to process the electrical signals fed into a pixel electronics unit by the converter unit into a digital pixel measurement signal. Each of the pixel electronics units of the plurality also comprises at least one controllable, digital signal processing unit, which is designed to adapt a processed, digital pixel measurement signal in a respective pixel electronics unit of the plurality of pixel electronics units.

[0015] The evaluation unit can be designed as an integrated circuit. The evaluation unit can, in particular, be designed as an application-specific integrated circuit (ASIC). Implementing a possibility for adapting the pixel measurement signals in the evaluation unit itself, in particular in an ASIC, can contribute to particularly efficient adaptation.

[0016] A converter unit coupled to the evaluation unit can be designed as a direct-converting converter unit comprising a direct-converting converter material. The converter unit can also be designed as an indirect-converting converter unit. In this case, the converter unit can, for example, comprise a scintillator material and a number of photodiodes coupled thereto.

[0017] The evaluation unit can be coupled to the converter unit via electrically conductive connections. For example, each of the plurality of pixel electronics of the evaluation unit can have one or more signal inputs configured to feed electrical signals from the converter unit into a pixel electronics unit if the evaluation unit is signal-coupled to the converter unit via electrically conductive connections.

[0018] A respective pixel electronics unit of the plurality of pixel electronics units of the evaluation unit can comprise analog and digital circuit elements. A pixel electronics unit according to the invention of the plurality of pixel electronics units can at least be configured to receive an electrical signal from a converter unit via at least one signal input when the signal input is coupled to a converter unit, to digitize an input electrical signal, for example, using an A / D converter (analog-to-digital converter), so that a digital pixel measurement signal can be provided in a pixel electronics unit based on the processing of a signal fed in by a coupled converter unit, and to adapt the digital pixel measurement signal using the signal processing unit according to the invention.A pixel electronics unit can then also comprise a signal output at which an adapted digital pixel measurement signal can be output after adaptation by means of the digital signal processing unit comprised by the pixel electronics unit.

[0019] A respective pixel electronics unit can have only one signal input that can be directly coupled to the converter unit. However, there can also be embodiments in which, in one pixel electronics unit of the plurality of pixel electronics units, signals from several signal inputs that can be coupled to a converter unit are combined, and wherein, based on the combined signals from several signal inputs, a pixel electronics unit provides a digital pixel measurement signal that can be adapted by the digital signal processing unit of the pixel electronics unit. The combination can be performed before or after digitizing the signals fed into the pixel electronics unit via the signal inputs.

[0020] In addition to digitization, pixel electronics can be designed to amplify or shape a signal fed in from a converter unit. Pixel electronics can also comprise at least one comparator designed to compare a signal fed in via a signal input and possibly amplified with an adjustable threshold value and, based thereon, to output a counting signal. Pixel electronics can furthermore have a counting element designed to count a number of counting signals, i.e. essentially threshold value exceedances in the comparator. The counting element can be designed, for example, as an incremental counter. The digital pixel measurement signal can then be based, for example, on the number counted by the counting element. The digital pixel measurement signal can correspond to a counter reading of the counting element.Based on such a counter reading, the intensity of incoming X-rays can be determined. Such a pixel electronics design is typically combined with a direct-conversion X-ray detector.

[0021] In this case, a respective pixel electronics unit can also comprise a plurality of comparators with adjustable threshold values ​​and counting elements. This can enable energy-resolved measurement of the incoming X-ray radiation. If the pixel electronics unit comprises a plurality of comparators and counting elements coupled thereto, thus providing a plurality of digital pixel measurement signals, for example in the form of counter readings of the plurality of counting elements, a signal processing unit of a pixel electronics unit of the plurality can be configured to adapt each or only a portion of the digital pixel measurement signals.

[0022] In an indirect-conversion X-ray detector, on the other hand, integrating pixel electronics are often used, whereby the energy deposition of photons arriving during a readout time window is integrated in the respective pixel electronics. The digital pixel measurement signal of a respective pixel electronics can then, for example, be based on the digitized, integrated value.

[0023] The digital signal processing unit according to the invention of a pixel electronics unit of the plurality of pixel electronics units can comprise one or more digital circuit elements which are designed to carry out an operation adapting the digital pixel measurement signal (hereinafter also referred to as adaptation operation) based on a digital pixel measurement signal, so that an adapted digital pixel measurement signal can subsequently be provided.

[0024] An adjustment operation may, for example, comprise an arithmetic operation or a combination of arithmetic operations. This may, for example, be addition, subtraction, division, multiplication, the application of an exponential function, or similar operations, particularly weighted operations. The adjustment operation may also comprise a logical operation, such as a comparison, a conjunction, a negation, or similar operations.

[0025] In addition to the digital pixel measurement signal to be adjusted, at least one further adjustment parameter can be included in an adjustment operation of the signal processing unit. An adjustment parameter can include, for example, a weighting factor, a decay time constant of an exponential function, a summand, a comparison parameter, or the like. An adjustment parameter that can be included in an adjustment operation of the signal processing unit can also be based on a measured value measured by the X-ray detector or a sensor linked to it. This can include, for example, one or more previously measured pixel measurement signals from the pixel electronics, one or more pixel measurement signals from one or more neighboring pixel electronics, or another measured value, such as a temperature measurement value or a time measurement value.

[0026] A digital signal processing unit according to the invention is designed to be controllable. The controllability of the digital signal processing unit can include the signal processing unit of a pixel electronics unit or the adaptation operation performed by the signal processing unit being adjustable, i.e., adaptable, by a user even after implementation in the pixel electronics unit. This can include the signal processing unit being parameterizable, configurable, and / or programmable.

[0027] For example, this includes defining variables or transfer values ​​for an adaptation operation, which are processed by the signal processing unit to execute the adaptation operation. This can also include specifying which variables or transfer values ​​should be included in an adaptation operation of the signal processing unit. For example, this can include whether an adaptation operation is based on a previously measured pixel measurement value or a temperature measurement value. This can include, for example, storing customizable default values ​​for adaptation parameters (hereinafter also referred to as adaptation coefficients), with which the adaptation operation is to be carried out by default. This can also include storing multiple sets of default values ​​or one default value, which can then be selected for the adaptation operation by means of the signal processing unit.The controllability of the digital signal processing unit can then include the selection of such a set. The provision of predefined sets of adaptation parameters can enable quick and easy adaptation of the signal processing unit to existing operating conditions.

[0028] For this purpose, transfer values ​​can be stored in a controllable memory element for adjustment parameters in the evaluation unit in a step of setting the evaluation unit or can be stored in a memory element at the latest time for retrieval, for example when using a measured value measured in close temporal proximity to an adjustment.

[0029] The controllability can also include adapting the circuitry of one or more circuit elements of the digital signal processing unit. For example, one circuit element can be selected from a plurality of circuit elements of the signal processing unit for adapting a digital pixel measurement signal. This can be enabled by adapting configuration parameters of the signal processing unit, which defines the circuitry of a plurality of circuit elements of the signal processing unit. Here, too, it can be provided that several sets of configuration parameters or one configuration parameter can be stored in a memory element in the evaluation unit, and the controllability comprises a selection of a configuration parameter set.

[0030] Programming can involve defining a sequence of operations, for example in the form of program code, which can then be implemented by the signal processing unit according to the defined sequence. For example, a program code comprising instructions for performing an operation or a sequence of operations can be stored in a program memory of the evaluation unit. This program code can then be executed based on the instructions by an executing switching element, for example, a dedicated arithmetic unit in the pixel electronics.

[0031] The selection of the adaptation parameters and / or the operations to be performed for adapting a digital pixel measurement signal in the pixel electronics of the plurality of pixel electronics can be based on prior experimental knowledge or calibration measurements. The prior experimental knowledge can include which adaptation of the digital pixel measurement signals is necessary to obtain an improved adapted digital pixel measurement signal and thus generate a higher-quality measurement data set.

[0032] The digital signal processing units of the plurality of pixel electronics can be configured to be individually controllable, so that each digital signal processing unit can be set individually and, if necessary, differently from another pixel electronics unit in the plurality. The digital signal processing units of the plurality of pixel electronics can also be controlled across a group comprising a plurality of pixel electronics units, so that the signal processing units can be set jointly and in the same way, at least within this group. The group can comprise the entire plurality of pixel electronics units. However, the plurality of pixel electronics units can be divided into several groups.

[0033] For control purposes, the evaluation unit can include a control data input, by means of which the digital signal processing units of the pixel electronics of the plurality of pixel electronics or associated memory elements can be controlled and adjusted individually or across groups. For example, the signal processing units can be controlled by means of an external processing unit, which is coupled to the control data input of a respective evaluation unit via a control data line and enables the transmission, adjustment, or selection of parameters or program code.

[0034] Using the digital signal processing unit provided in the pixel electronics, the pixel measurement signals can advantageously be adapted in the pixel electronics before being read out by the evaluation unit. This can be advantageously used to correct the pixel measurement signals. For example, time-, temperature-, or radiation-dependent drift effects can be corrected or at least reduced in the pixel electronics. Near-pixel adaptation, especially when implemented in an ASIC, can enable a particularly efficient way of correcting the digital pixel measurement signals. In particular, correction in an ASIC can be significantly more efficient than downstream corrections based on processing using FPGAs or similar processing units.The adaptation can advantageously be adapted based on the current operating conditions or on a selected application sequence for an application of an X-ray detector comprising the evaluation unit.

[0035] According to the invention, the digital signal processing unit of a respective pixel electronics comprises a measured value memory into which the digital pixel measurement signal can be transferred. The digital signal processing unit is then configured to adapt the digital pixel measurement signal transferred to the measured value memory.

[0036] Advantageously, the adaptation and generation of the digital pixel measurement signals can be decoupled, so that a new pixel measurement signal can be generated while a digital pixel measurement signal is being adapted. This advantageously avoids dead time in the respective pixel electronics for the acquisition of electrical signals from the converter unit.

[0037] A memory element designed as a measured value memory can also be designed to store more than one digital pixel measurement signal.

[0038] Furthermore, in one embodiment of the evaluation unit, the digital signal processing unit can be designed to adapt a current digital pixel measurement signal based on at least one previously processed digital pixel measurement signal.

[0039] For this purpose, the digital signal processing unit can have a memory element for at least one digital pixel measurement signal previously processed by the pixel electronics, and the digital signal processing unit can be configured to adapt the current digital pixel measurement signal based on the at least one previously processed digital pixel measurement signal. For example, a time dependence of the pixel measurement signals can be derived from previous pixel measurement signals.

[0040] Furthermore, in one embodiment of the evaluation unit, the digital signal processing unit can be designed to adapt a current digital pixel measurement signal based on at least one digital pixel measurement signal of an adjacent pixel electronics.

[0041] For this purpose, the digital signal processing unit can have a storage element for at least one digital pixel measurement signal from an adjacent pixel electronics unit, and the digital signal processing unit can be configured to adapt the currently processed pixel measurement signal based on the at least one digital pixel measurement signal from the adjacent pixel electronics unit. The pixel electronics units are then configured such that a pixel measurement signal from an adjacent pixel electronics unit can be transferred to the storage element. Based on adjacent pixel measurement signals, a correlated adaptation can be enabled.

[0042] The signal processing unit can also be configured to adapt a current digital pixel measurement signal based on more than one previously processed digital pixel measurement signal or based on more than one digital pixel measurement signal from an adjacent or a plurality of adjacent pixel electronics. A previously described memory element can accordingly be configured to store more than one of these pixel measurement signals.

[0043] According to a further embodiment of the evaluation unit, the digital signal processing unit comprises a digital circuit element from the following list • an adding element, • a multiplier element, • a division element, • a calculation element for an exponential function, • a multiplexer.

[0044] Advantageously, adjustments can be performed based on addition, multiplication, division, or based on an exponential function. A multiplexer can advantageously enable a simple interconnection of circuit elements of the signal processing unit.

[0045] The digital signal processing unit can comprise several circuit elements. The interconnection of the circuit elements can then be configured in a particularly configurable manner. This allows the signal processing unit and the resulting adaptation to operating conditions or an application sequence to be tuned.

[0046] The digital signal processing unit can also include a memory element for at least one adaptation parameter or at least one configuration parameter for setting the signal processing unit. For example, transfer values ​​and adaptation coefficients for adaptation operations can be stored in the memory element. A configuration parameter can include a parameter relating to a connection of the signal processing unit. The memory element can, in particular, be controllable and thus adaptable, allowing a user to change and adapt the adaptation parameter or configuration parameter and to set the digital signal processing unit.

[0047] Furthermore, a memory element for at least one adaptation parameter or configuration parameter can be formed in the evaluation unit for setting the digital signal processing units of a plurality of pixel electronics.

[0048] In this way, the digital signal processing units within a group of pixel electronics comprising a plurality of pixel electronics can be designed to be controllable across multiple pixel electronics, so that the signal processing units can be adjusted jointly and in the same way, at least within this group. The group can comprise the entire plurality or only a portion of the plurality of pixel electronics. In this case, easier adjustment of the plurality of pixel electronics can advantageously be enabled.

[0049] A memory element can be implemented as a memory block or as a register, for example as a so-called D flip-flop.

[0050] According to a variant of the evaluation unit, the digital signal processing unit of a respective pixel electronics can comprise a processor core with an arithmetic logic unit (ALU).

[0051] An ALU is an electronic arithmetic unit. An ALU is designed to calculate arithmetic and logical functions. It can generally perform at least minimal operations such as addition, negation, or conjunction. It can also perform operations such as subtraction, multiplication, division, comparison, disjunction, contravalence, and others.

[0052] Advantageously, more complex adaptation operations can also be carried out, in particular based on a sequence of several commands.

[0053] The evaluation unit can comprise a program memory containing program code for controlling the ALU. The program memory can be implemented in each of the plurality of pixel electronics. The program memory can also be implemented across the digital signal processing units of a plurality of pixel electronics. A program memory can be programmable or configurable, in particular, via a control data input of the evaluation unit, so that the operations performed by the digital signal processing units can be easily adapted.

[0054] In particular, a comprehensive program memory can be designed to interact with a comprehensive memory element for at least one adaptation parameter.

[0055] The control of the processor cores in the pixel electronics of the multiple pixel electronics can be implemented according to the Single Instruction Multiple Data (SIMD) principle. This allows the same operation to be performed simultaneously on multiple data items, in this case the pixel measurement signal(s) of the pixel electronics.

[0056] Advantageously, time-efficient programming and parallel execution of the adjustment operations on all pixel electronics can be easily implemented.

[0057] Furthermore, the invention relates to an X-ray detector comprising an evaluation unit according to the invention and a converter unit, wherein each pixel electronics of the plurality of pixel electronics is electrically conductively coupled to the converter unit for feeding electrical signals into the pixel electronics.

[0058] The X-ray detector can also comprise a plurality of evaluation units. The plurality of evaluation units can be coupled to a converter unit or to a plurality of converter units. The use of small-area evaluation units can be more cost-effective. By using a plurality of evaluation units and / or a plurality of converter units, larger-area X-ray detectors can be achieved than with a single unit alone.

[0059] All design variants previously described in connection with the evaluation unit according to the invention can also be implemented correspondingly in the X-ray detector. The description given with regard to the evaluation unit and the advantages of the evaluation unit described above can also be applied to the X-ray detector.

[0060] Furthermore, the invention relates to a medical imaging device comprising at least one X-ray detector comprising an evaluation unit and, in contrast thereto, an X-ray source designed to expose the X-ray detector with X-ray radiation.

[0061] To record the X-ray image data set, the object to be imaged can be placed between the X-ray source and the X-ray detector and irradiated using the X-ray source.

[0062] In particular, the medical imaging device can be designed as a computed tomography device. The medical imaging device can also be designed as a SPECT or PET system. However, it can also be designed, for example, as a C-arm X-ray device and / or Dyna-CT, or in another way.

[0063] All design variants previously described in connection with the evaluation unit according to the invention can also be implemented correspondingly in the medical imaging device comprising an X-ray detector with an evaluation unit according to the invention. The description given with regard to the evaluation unit and the advantages described above can also be applied accordingly to the medical imaging device according to the invention.

[0064] The invention further relates to a method for operating an X-ray detector according to one of the variants described above.

[0065] The process includes the steps of exposure, processing and adjustment.

[0066] In the exposure step, the converter unit of the X-ray detector is exposed to X-ray radiation by means of an X-ray source, whereby electrical signals are generated in the converter unit, which are fed into the plurality of pixel electronics of the evaluation unit via the electrically conductive coupling.

[0067] In the processing step, the input electrical signals are processed into a digital pixel measurement signal by means of a respective pixel electronics of the plurality of pixel electronics.

[0068] In the step of adapting, at least one digital pixel measurement signal in a pixel electronics of the plurality of pixel electronics is adapted by means of the controllable digital signal processing unit of the pixel electronics.

[0069] The adjustment step allows the pixel measurement signal to be corrected, so that an improved data set of digital pixel measurement signals can be provided based on the adjusted pixel measurement signals. Based on an improved data set, for example, an improved X-ray image data set with higher image quality can then be generated.

[0070] The method may further comprise the step of adjusting the evaluation unit. Adjusting may comprise parameterizing, configuring, and / or programming at least one controllable digital signal processing unit and / or a memory element linked thereto. Adjusting may comprise adjusting an adjustment parameter, a configuration parameter, or a program code for executing an adjustment operation by the digital signal processing unit.

[0071] The advantages of the evaluation unit according to the invention and its design variants can also be directly transferred to the method for operating an X-ray detector according to the invention comprising an evaluation unit according to the invention according to one of the previously described design variants.

[0072] Within the scope of the invention, features described in relation to different embodiments of the invention and / or different claim categories (method, use, device, system, arrangement, etc.) can also be combined to form further embodiments of the invention. For example, a claim relating to a device can also be developed with features described or claimed in connection with a method, and vice versa. Functional features of a method can, for example, be implemented by appropriately designed physical components. In addition to the embodiments of the invention expressly described in this application, a wide variety of further embodiments of the invention are conceivable, which the person skilled in the art can arrive at without departing from the scope of the invention as defined by the claims.

[0073] The use of the indefinite articles "ein" or "eine" does not preclude the feature in question from being present multiple times. The use of the term "aufeinander" (to have) does not preclude the concepts linked by the term "aufeinander" (to have) from being identical. For example, the medical imaging device comprises the medical imaging device. The use of the term "einheit" does not preclude the object to which the term "einheit" refers from having multiple components that are spatially separated from one another.

[0074] In the context of the present application, the expression "based on" can be understood in particular in the sense of the expression "using." In particular, a formulation according to which a first feature is generated (alternatively: determined, determined, etc.) based on a second feature does not exclude the possibility that the first feature can be generated (alternatively: determined, determined, etc.) based on a third feature.

[0075] The invention is explained below using exemplary embodiments with reference to the accompanying figures. The representation in the figures is schematic, highly simplified, and not necessarily to scale. The same reference numerals are used for the same features in different figures. They show: Fig. 1 a schematic representation of a variant of an exemplary X-ray detector with an evaluation unit, Fig. 2 a schematic representation of a first embodiment of a signal processing unit in an evaluation unit, Fig. 3 a schematic representation of a second embodiment of a signal processing unit in an evaluation unit, Fig. 4. a schematic representation of a third embodiment of a signal processing unit in an evaluation unit, Fig. 5 an exemplary embodiment of a medical imaging device, and Fig. 6 a schematic process flow of a method for operating an X-ray detector.

[0076] Fig. Figure 1 shows an exemplary arrangement of several X-ray detectors 2 according to an exemplary embodiment. In the arrangement shown, the X-ray detectors 2 are arranged in a matrix to form a larger total area for detecting X-ray radiation. Other arrangements of one or more X-ray detectors are also possible.

[0077] In Fig. 1 shows an example of a direct-converting X-ray detector 2, comprising a converter unit 3 with a direct-converting converter material. The converter material can comprise, for example, CdTe, CZT, CdZnTeSe, CdTeSe, CdMnTe, InP, TlBr2, HgI2, GaAs, Si, or another suitable material. The top side of the converter element 3 has a first electrode 71 (top electrode). The bottom side of a respective converter unit 3 has sensor pixel electrodes 55. The sensor pixel electrodes 55 are connected to the evaluation unit 1 via the electrically conductive connections 69 and the evaluation pixel electrodes 57.

[0078] The evaluation unit 1 can be designed, in particular, in the form of an ASICS. The electrically conductive connections 69 can be designed, for example, as solder bump bonds or solder material in combination with copper pillars, or in some other way. The evaluation unit 1 is signal-coupled to the converter unit 3 via the sensor pixel electrodes 55, the electrically conductive connections 69, and the evaluation pixel electrodes 57.

[0079] An electric field can be applied between the first electrode 71 and the respective sensor pixel electrodes 57, which defines a sensitive detection volume in the converter element 3, each associated with an evaluation pixel electrode 57. The electrical signal generated in such a detection volume by energy deposition from incoming X-ray photons can then be fed into the evaluation unit 1, and in particular into a signal input of a pixel electronics unit 5 of the evaluation unit 1, via the associated electrically conductive connection 69 and the evaluation pixel electrode 57.

[0080] In the example shown, the evaluation unit 1 is also arranged on a substrate 61 and is connected to a peripheral electronics 65, for example via TSV connections 63 (“Through Silicon Via” connections) through the substrate 61.

[0081] An X-ray detector according to the invention can also be used in other ways than Fig. 1. In particular, the X-ray detector 1 can also be designed as an indirect-converting X-ray detector comprising an indirect-converting converter unit. Here and in the following Fig. For illustrative purposes, Figures 2 to 4 refer to a counting, direct-conversion X-ray detector. However, transferring the exemplary embodiments to an indirect-conversion X-ray detector and an integrating X-ray detector is readily possible for a person skilled in the art.

[0082] The evaluation unit 1 of the X-ray detector 2 has a plurality of pixel electronics 5. The pixel electronics 5 are designed to process the electrical signals fed into a respective pixel electronics 5 by the converter unit 3 into a digital pixel measurement signal.

[0083] In the example shown, the number of sensor pixel electrodes is 55, the number of conductive connections is 69, the number of evaluation pixel electrodes is 57, and the number of pixel electronics is 5 in the evaluation unit 1 are the same. However, other configurations are also possible.

[0084] According to the invention, the evaluation unit 1 has a plurality of pixel electronics 5, wherein each of the pixel electronics 5 has at least one controllable, digital signal processing unit 7, which is designed to adapt a processed, digital pixel measurement signal in a respective pixel electronics of the plurality of pixel electronics 5.

[0085] The plurality of pixel electronics 5, each comprising a digital signal processing unit 7, can correspond to the above-described plurality of pixel electronics 5. This means that each of the pixel electronics 5 of the plurality can also be part of the plurality of pixel electronics 5. However, other configurations are also possible.

[0086] A respective pixel electronics unit 5 of the plurality of pixel electronics units of the evaluation unit 1 can comprise analog and digital circuit elements. The pixel electronics units 5 of the plurality of pixel electronics units 5 are at least designed to receive an electrical signal from a converter unit 3 via at least one signal input and to digitize an input electrical signal, so that a digital pixel measurement signal can be provided in a pixel electronics unit based on the processing of a signal fed in by a coupled converter unit 3. The digital signal processing unit 7 according to the invention of the pixel electronics unit 5 can comprise one or more digital circuit elements, which is designed orwhich are configured to perform an adaptation operation based on a digital pixel measurement signal that adapts the digital pixel measurement signal, so that the pixel electronics 5 can subsequently provide a digital pixel measurement signal adapted by the signal processing unit 7. The adaptation operation can comprise an arithmetic or logical operation.

[0087] The digital signal processing unit 7 of a respective pixel electronics 5 of the plurality of pixel electronics 5 is designed to be controllable, in the sense that it can be parameterized, configured and / or even programmable, thus enabling setting and adaptation of the signal processing unit 7 or the adaptation operation performed by it.

[0088] The digital signal processing units 7 of the plurality of pixel electronics 5 can be configured to be individually controllable, so that each digital signal processing unit 7 can be individually adjusted and, if necessary, differently from the signal processing unit 7 of another pixel electronics 5 of the plurality. The digital signal processing units 7 of the plurality of pixel electronics can also be comprehensively controlled only within a group of pixel electronics 5, so that the signal processing units 7 can be adjusted jointly and in the same way, at least within this group.

[0089] Fig. Fig. 2 shows a purely schematic representation of a first embodiment of a signal processing unit 7 in an evaluation unit 1 of an X-ray detector 2 as shown by way of example in Fig. 1 shown.

[0090] For illustrative purposes, only three pixel electronics 5 of an evaluation unit 1 are shown, each of which is coupled to the converter unit 5 via an electrically conductive connection. In particular, each pixel electronics has a signal input for feeding in electrical signals.

[0091] As already mentioned in the description of Fig. As mentioned in section 1, reference is made here to a photon-counting, direct-conversion X-ray detector. However, transfer to an integrating and / or indirect-conversion X-ray detector is readily possible.

[0092] In the example shown, a signal amplification unit 13 and a comparator 15 with an adjustable threshold value THR are connected to a respective signal input of a pixel electronics unit 5 coupled to the converter unit 3. An electrical signal fed in from the converter unit based on the energy deposition of an X-ray photon in the converter material is amplified in the signal amplification unit. Typically, the amplified signal is also shaped into a voltage pulse using a pulse shaper. The amplified signal is compared with an adjustable threshold value THR by the comparator 15, whereby a binary counting signal is output if the threshold value is exceeded. The binary counting signal can then be counted using the counting element 19, designed, for example, as an incremental counter.The counting element 19 provides the digital pixel measurement signal in the form of its counter reading, which is then adjusted by the digital signal processing unit 7. In other embodiments, additional elements can also be provided in the pixel electronics.

[0093] In the embodiment shown, the digital signal processing unit 7 of a respective pixel electronics unit 5 comprises a measured value memory 11, into which the digital pixel measurement signal can be transferred. This means that the counter reading of the counting element can be transferred to the measured value memory 11.

[0094] The digital signal processing unit 7 is then configured to adapt the pixel measurement signal transmitted to the measured value memory 11. For this purpose, the signal processing unit 7 shown comprises a switching element 9 configured to perform an operation based on the digital pixel measurement signal stored in the measured value memory 11.

[0095] The signal processing unit 7 can, for example, comprise an adding element, a multiplying element, a dividing element, a calculating element for an exponential function, or another digital circuit element 9 as a digital circuit element 9. In particular, a plurality of differently designed digital circuit elements 9 can be provided, which can perform different operations for adapting the digital pixel measurement signal. In particular, the interconnection of the circuit elements 9 can be configured by adapting configuration parameters. This can enable a selection of an operation or a configurable cascading of operations. For this purpose, one or more multiplexers or a network for interconnecting the circuit elements 9 can be provided in the signal processing unit 7.Likewise, a memory element can be provided for at least one configuration parameter, which can be called up for a configuration of the signal processing units.

[0096] In the embodiment shown, the signal processing unit 7 also includes a memory element 22 for at least one adaptation parameter. An adaptation parameter stored in a memory element 22 can, for example, include a weighting factor, a decay time constant of an exponential function, a summand, a comparison parameter, or the like, which is included in the adaptation operation of the signal processing unit. The memory element 22 is, in particular, designed to be controllable, thus enabling adaptation of the at least one adaptation parameter in the memory element 22.

[0097] The signal processing unit 7 also has a memory element 21 for at least one digital pixel measurement signal previously processed by the pixel electronics 5. A plurality of adjustment parameter values ​​can be stored in the memory element. An adjustment parameter can be selected for the adjustment operation at least as a function of the pixel measurement signal.

[0098] The digital signal processing unit 7 shown can be configured to adapt a current digital pixel measurement signal transmitted in the measured value memory 11 based on at least one previously processed digital pixel measurement signal from the memory element 21 and based on the at least one adaptation parameter stored in the memory element 22. For example, the previously measured pixel measurement signal can be transmitted to the memory element 21 before an adaptation of the previously measured pixel measurement signal and subsequently incorporated into the adaptation of a current measured pixel measurement signal. The memory element 21 can, in particular, also be configured to store more than one previously measured digital pixel measurement signal.

[0099] Alternatively or additionally, a memory element for at least one digital pixel measurement signal from an adjacent pixel electronics unit 5 can also be formed in the signal processing unit 7. The digital signal processing unit 7 can be designed to adapt a current digital pixel measurement signal based on at least one digital pixel measurement signal from an adjacent pixel electronics unit 5. The memory element can be designed to store digital pixel measurement signals from a plurality of adjacent pixel electronics units 5. The pixel electronics units 5 can be designed or connected to one another in terms of signal technology in such a way that a transmission of the pixel measurement signals between the pixel electronics units 5 is possible, ie that a digital pixel measurement signal from an adjacent pixel electronics unit can be transmitted to a memory element of the pixel electronics unit in question.

[0100] An adjustment parameter for an adjustment operation can be selected depending on a pixel measurement signal from an adjacent pixel electronics 55 or depending on a previously measured pixel measurement signal.

[0101] In the example shown, all pixel electronics 5 are designed identically. However, there may be different designs.

[0102] After adjusting the digital pixel measurement signal, the adjusted pixel measurement signal can be output or read out. Only one comparator 15 and one counting element 19 are shown in the illustration. In other embodiments, multiple comparators 15, each with an adjustable threshold THR, and counting elements 19 coupled thereto can be provided with each signal input, so that, based on this, multiple digital pixel measurement signals are provided in each pixel electronics unit 5. If multiple digital pixel measurement signals are provided by means of a pixel electronics unit 5, the signal processing unit 7 can be configured to adjust all or only a portion of the digital pixel measurement signals.

[0103] Fig. 3 shows a further embodiment of a signal processing unit 7 of an evaluation unit 1.

[0104] In this case, only one switching element 9 and one measured value memory 11 are shown for illustrative purposes. However, additional switching elements 9 and / or memory elements may also be provided. Furthermore, a memory element 24 for at least one adaptation parameter or configuration parameter is also provided in the evaluation unit 1, which is used to adjust the digital signal processing units 7 of a plurality of pixel electronics 5.

[0105] This means that in this illustrated case, not every signal processing unit 7 has a memory element for at least one adaptation parameter or at least one configuration parameter, but rather this is provided jointly for at least one group of signal processing units 7. The parameter or parameters from the overarching memory element 24 can then be incorporated equally into the configuration of the signal processing unit 7 or the adaptation operation of the digital pixel measurement signal of all pixel electronics 5 of the group of pixel electronics 5. The group can comprise the entire plurality of pixel electronics 5 of the evaluation unit 1. However, multiple groups, each with an associated overarching memory element 24, can also be provided.

[0106] In addition, each pixel electronics unit 5 comprises a further readout memory element 27, into which the adjusted pixel measurement signal can be output, ie, essentially copied, from the measured value memory 11 of the signal processing unit 7. The adjusted digital pixel measurement signal can be read out from the readout memory element 27.

[0107] In this way, the readout can also be decoupled from the adaptation of the digital pixel measurement signals in the signal processing unit 7. This advantageously prevents dead times.

[0108] Fig. 4 shows a further embodiment of a signal processing unit 7.

[0109] In this variant, the digital signal processing unit 7 comprises a processor core 23 with an arithmetic logic unit (ALU).

[0110] In addition, the evaluation unit 1 comprises a program memory 25, which comprises a program code for controlling a processor core 23 of a signal processing unit 7 of a pixel electronics unit of the plurality of pixel electronics units 5.

[0111] In the variant shown, the program memory 25 is designed to be comprehensive for the digital signal processing units 7 of a plurality of pixel electronics 5.

[0112] In addition to the program memory 25, a memory element (not shown in the illustration) for at least one adaptation parameter can also be provided, preferably also across multiple pixel electronics 5 for adaptation parameters which are included in the adaptation of a digital pixel measurement signal by means of the ALU.

[0113] The control of the processor cores in the pixel electronics of the multitude of pixel electronics can then be implemented according to the Single Instruction Multiple Data (SIMD) principle. This allows the same operation to be executed simultaneously on multiple data items, in this case the pixel measurement signal(s) of the pixel electronics.

[0114] Fig. 5 shows an exemplary embodiment of a medical imaging device 32 with a detection unit 36 ​​comprising at least one X-ray detector 2 according to the invention and an X-ray source 37 in opposition to the detection unit 36. The X-ray source 37 is designed to expose the detection unit 36, and thus a converter unit 3 of the X-ray detector 2, with X-ray radiation. The medical imaging device 32 shown is designed in particular as a computed tomography device. The computed tomography device comprises a gantry 33 with a rotor 35. The rotor 35 comprises the X-ray source 37 and the detection unit 36. The rotor 35 is rotatable about the rotation axis 43. The examination object 39, here a patient, is mounted on the patient couch 41 and is movable along the rotation axis 43 by the gantry 33. In general, the object 39 can comprise, for example, an animal patient and / or a human patient.The computing unit 700 is provided for controlling the medical imaging device and / or for generating an X-ray image data set based on pixel measurement signals processed and adapted by the X-ray detector 2.

[0115] In the case of a computed tomography device, a (raw) X-ray image dataset of the object is typically acquired from a plurality of angular directions using at least one X-ray detector 2, which is based on processed electrical pixel measurement signals from the pixel electronics 5 of the evaluation unit 1. Subsequently, a final X-ray image dataset can be reconstructed based on the (raw) X-ray image dataset using a mathematical method, for example, comprising a filtered backprojection or an iterative reconstruction method.

[0116] The computing unit 700 may include a control unit for controlling the medical imaging device 32 and a generation unit 55 for generating an X-ray image dataset based on pixel measurement signals. The computing unit 700 may be configured to control, i.e., configure, parameterize, or program, the controllable digital signal processing units 7 in the pixel electronics 5 or elements provided across a plurality of pixel electronics 5, for example, memory elements.

[0117] Furthermore, an input device 47 and an output device 49 are connected to the computing unit 700. The input device and the output device can, for example, enable interaction, such as manual configuration, confirmation, or triggering of a method step by a user.

[0118] Fig. 6 shows a schematic process flow of a method for operating an X-ray detector 2 according to the invention, for example according to one of the methods described in connection with Fig. Variants described in 1 to 4.

[0119] The method comprises the step of exposing S1 the converter unit 3 of the X-ray detector 2 with X-ray radiation by means of an X-ray source 37 and thereby generating electrical signals in the converter unit 3, which are fed into the plurality of pixel electronics 5 of the evaluation unit 1 via the electrically conductive coupling.

[0120] The method further comprises the step of processing S2 the fed-in electrical signals by means of a respective pixel electronics 5 of the plurality of pixel electronics 5 into a digital pixel measurement signal.

[0121] The method further comprises the step of adaptation S3, wherein at least one digital pixel measurement signal in a pixel electronics 5 is adapted by means of the controllable digital signal processing unit 7 of the pixel electronics 5.

[0122] The adjusting step S3 allows a correction of the pixel measurement signal to be performed, so that an improved data set of digital pixel measurement signals can be provided based on the adjusted pixel measurement signals. Based on an improved data set, an improved X-ray image data set with higher image quality can then be generated, for example. The method can accordingly also comprise a step of providing the digital pixel measurement signals of the pixel electronics 5, wherein at least one provided pixel measurement signal is an adjusted digital pixel measurement signal.

[0123] The method may further comprise the step of setting S0 of the evaluation unit 1. Setting S0 may comprise parameterizing, configuring, and / or programming at least one signal processing unit 7 and / or a memory element 24, 25, 22 linked thereto for at least one adaptation parameter, a configuration parameter, or a program memory by controlling the signal processing unit 7 by a user. For this purpose, the evaluation unit 1 may comprise at least one control data input, via which a transmission, selection, or adaptation of parameters or program code for setting at least one signal processing unit 7 is enabled. Control may be enabled, for example, by means of a computing unit 700 and an input device 47 and output device 49 coupled thereto.The user can, for example, select a setting, such as a tube current or a tube voltage of a medical device, or an application sequence, i.e., a specific examination type, which can then be incorporated into the setting of the evaluation unit 1. For example, based on this, an adaptation parameter set or a configuration parameter set for the signal processing unit 7 can be selected automatically or semi-automatically by means of the computing unit 700, and the set or merely selection information can be transmitted to the signal processing unit 7. Parameters can also be selected manually, for example, by direct input by a user using an input unit 47 and transmission to the signal processing unit 7.

Claims

[1] Evaluation unit (1) for an X-ray detector (2) for signal-technical coupling to a converter unit (3) which is designed to convert incoming X-ray radiation into electrical signals, comprising a plurality of pixel electronics (5), wherein a respective pixel electronics (5) is designed to process the electrical signals fed by the converter unit (3) into a respective pixel electronics (5) into a digital pixel measurement signal, and wherein each of the pixel electronics (5) has at least one controllable, digital signal processing unit (7) which is designed to adapt a processed, digital pixel measurement signal in a respective pixel electronics (5), wherein the digital signal processing unit (7) of a respective pixel electronics (5) comprises a measured value memory (11) into which the digital pixel measurement signal can be transmitted, and the digital signal processing unit (7) is designed,to adapt the pixel measurement signal transferred to the measured value memory (11). [2] Evaluation unit (1) according to claim 1, wherein the evaluation unit (1) is designed as an application-specific, integrated readout circuit. [3] Evaluation unit (1) according to one of the preceding claims, wherein the respective digital signal processing unit (7) is designed to adapt a current digital pixel measurement signal based on at least one previously processed digital pixel measurement signal or based on at least one digital pixel measurement signal of an adjacent pixel electronics unit (5). [4] Evaluation unit (1) according to one of the preceding claims, wherein the respective digital signal processing unit (7) comprises a digital circuit element (9) from the following list • an adding element, • a multiplier element, • a division element, • a calculation element for an exponential function, • a multiplexer. [5] Evaluation unit (1) according to one of the preceding claims, wherein the respective digital signal processing unit (7) comprises a memory element (22) for at least one adaptation parameter or at least one configuration parameter for setting the signal processing unit (7). [6] Evaluation unit (1) according to one of the preceding claims, wherein a memory element (24) for at least one adaptation parameter or at least one configuration parameter is formed in the evaluation unit (1) for setting the digital signal processing units (7) of a plurality of pixel electronics (5). [7] Evaluation unit (1) according to one of the preceding claims, wherein the respective digital signal processing unit (7) comprises a processor core (23) with an arithmetic-logic unit. [8] Evaluation unit (1) according to claim 7, wherein the evaluation unit (1) comprises a program memory (25) which comprises a program code for controlling a processor core (23) of a signal processing unit (7) of a pixel electronics unit of the plurality of pixel electronics units (5). [9] Evaluation unit (1) according to claim 8, wherein the program memory (25) is designed to be comprehensive for the digital signal processing units (7) of a plurality of pixel electronics (5). [10] X-ray detector (2) comprising an evaluation unit (1) according to one of the preceding claims and a converter unit (3), wherein each pixel electronics (5) of the plurality of pixel electronics (5) is electrically conductively coupled to the converter unit (3) for feeding electrical signals into the pixel electronics (5). [11] Medical imaging device (32) comprises at least one X-ray detector (2) according to claim 10 and, in opposition thereto, an X-ray source (37) designed to expose the X-ray detector (2) with X-ray radiation. [12] The medical imaging device (32) of claim 11, wherein the medical imaging device (32) comprises a computed tomography device. [13] Method for operating an X-ray detector (2) according to claim 10, comprising the steps of • Exposing (S1) the converter unit (3) to X-ray radiation by means of an X-ray source (37) and thereby generating electrical signals in the converter unit (3), which are fed into the plurality of pixel electronics (5) of the evaluation unit (1) via the electrically conductive coupling, • Processing (S2) the supplied electrical signals by means of a respective pixel electronics (5) of the plurality of pixel electronics (5) to form a digital pixel measurement signal, • Adapting (S3) at least one digital pixel measurement signal in a pixel electronics (5) by means of the controllable digital signal processing unit (7).

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