Reduction of the amount of data during internal data transmission in a radiation detector

Abstract

Method for generating projection data (PD) based on measurement signals from a radiation detector (1) with a plurality of sensor pixel electrodes (2), evaluation units (3) downstream of the plurality of sensor pixel electrodes (2), and a module electronic element (4) downstream of the evaluation units (3), comprising the steps: - Acquiring measurement signals (MS) by the sensor pixel electrodes (2), - Determining a respective count rate (CR) based on the measurement signals (MS) in the evaluation units (3), - Performing at least one additional data processing step in the evaluation units (3), generating processed count rate data (CR) such that the amount of data to be transmitted by the evaluation units (3) is reduced compared to the amount of data that would occur without the additional data processing step, - Transmitting the processed count rate data (CR) to the downstream module electronic element (4).- Generation of projection data (PD) by the downstream module electronic element (4) based on the processed count rate data (VZR), wherein the additional data processing step includes taking coincidence information into account when determining the processed count rates (VZR).

Description

[0001] The present invention relates to a method for generating projection data based on measurement signals from a radiation detector having a plurality of sensor pixel electrodes, evaluation units connected downstream of the plurality of sensor pixel electrodes, and a modular electronic element connected downstream of the evaluation units. Furthermore, the invention relates to a radiation detector. The invention also relates to an imaging system.

[0002] Modern imaging techniques often generate two- or three-dimensional image data that can be used to visualize an object under examination and for other applications. To obtain image information from an object under examination, systems based on the detection of electromagnetic waves that have interacted with the object under examination are often used.

[0003] One way to acquire image data from the interior of such an examination object is based on X-ray imaging technology. An X-ray system used for this purpose comprises an X-ray source for generating X-rays and an X-ray detector for detecting the X-rays. The X-ray detector comprises a detection unit that generates a detection signal for X-rays impinging on the detection unit, an evaluation unit that determines a set of count rates for X-rays impinging on the detection unit based on the detection signal, and a module electronic element that further processes the determined count rates, in particular correcting them for coincidence effects and combining them into projection data.

[0004] In order to acquire three-dimensional data from an examination subject, a computed tomography system (CT system for short) is frequently used to acquire projection measurement data from the examination subject. In CT systems, a combination of an X-ray source and an opposite X-ray detector, arranged on a gantry, usually rotates around a measurement space in which the examination subject (hereinafter referred to as the patient without loss of generality) is located. The center of rotation (also called the "isocenter") coincides with a so-called system axis z. In one or more rotations, the patient is irradiated with X-rays from the X-ray source, with projection measurement data or X-ray projection data being acquired with the help of the opposite X-ray detector.

[0005] The generated projection measurement data depends particularly on the design of the X-ray detector. X-ray detectors typically have a plurality of detection units, usually arranged in the form of a regular pixel array. The detection units each generate a detection signal for each X-ray incident on the detection units, which is analyzed at specific times with regard to the intensity and spectral distribution of the X-ray radiation in order to obtain conclusions about the object under examination and generate projection measurement data.

[0006] So-called quantum-counting X-ray detectors are now being used to detect projection measurement data. In such quantum-counting or photon-counting X-ray detectors, the X-ray detection signal is analyzed with regard to the intensity and spectral distribution of the X-ray radiation in the form of count rates. The count rates are provided as output data of a so-called detector channel, each of which is assigned to a detection unit. In quantum-counting or photon-counting detectors with multiple energy thresholds, each detector channel usually generates a set of count rates per projection based on the respective detection signal of the detection unit. The set of count rates can include count rates for several different energy thresholds, especially those checked simultaneously.The energy thresholds and the number of energy thresholds, each of which is assigned an energy threshold, are usually specified as signal analysis parameters for capturing the projection.

[0007] The control and signal analysis in an evaluation unit of such an X-ray detector is carried out by externally supplied register values, which are converted into control voltages via digital-to-analog converters (DACs for short).

[0008] Especially in modern CT systems, the amount of data to be transmitted and processed, resulting from the sensor signals, is extremely high and must be transmitted in real time. Even if the data to be transmitted is temporarily buffered in the rotating part of the CT system, the data transmission capacity is usually not sufficient to fully transmit the counting rates or projection data. With photon-counting X-ray detectors, the data rate is significantly increased compared to conventional systems, for example, by a factor of about 40, because multiple energy thresholds, for example four energy thresholds, must be measured for each of the much smaller pixels. In addition to the increased number of energy thresholds, the resolution of the photon-counting X-ray detectors is also significantly increased.For example, a pixel of a photon-counting X-ray detector has an area of ​​only one-tenth of a square millimeter, compared to the one-square millimeter of a conventional X-ray sensor. If the performance of photon-counting detectors is to be further improved, it is possible to further increase the number of energy thresholds and / or generate and transmit additional information, such as measurement data from coincidence measurements between neighboring pixels of an X-ray detector, thereby further increasing the data rate of the data to be transmitted in an X-ray detector.

[0009] Previous approaches to meeting the increased requirements aimed either at faster data transmission and higher-performance storage or at reducing the data rate by omitting data, in particular by selecting energy thresholds or limiting the readout to certain ranges or by calculating data in the module electronics element.

[0010] However, increasing data transmission capacity or storage capacity and thus also increasing processing capacity requires a great deal of effort and is also very cost-intensive, so that this approach has certain limitations.

[0011] Until now, it has been common practice to transmit all measurement data, especially count rates, from the evaluation units unprocessed to the downstream module electronics element, where they are processed. The measurement data is transmitted at a very high data rate and with a much higher bandwidth than is the case with subsequent data transmission, especially between the rotating and stationary parts of the CT system.However, this internal transmission in the rotating part already limits the overall data flow, as the complete readout of the measurement data takes a certain amount of time, for example, in the range of a few hundred µs. This time is further extended if the amount of measurement data increases, for example, due to an increase in the number of energy thresholds or the transmission of additional coincidence information, so that complete readout of this data is no longer possible within a desired time period, for example, 120 µs to 250 µs. To meet the desired time period, the only conventional options are to no longer read or transmit the measurement data completely, or to additionally consolidate the completely readout data in the module electronics element.Such summaries include, for example, the summation of neighboring pixel values ​​to form a larger pixel or a weighted summation of multiple energy thresholds within a single pixel.

[0012] Furthermore, attempts are also conventionally made to reduce the detector area to be read out, for example by significantly reducing the number of lines to be read out by more than 50 percent in order to reduce the total data stream.

[0013] However, the aforementioned procedures are usually associated with a reduction in image quality, so that these approaches do not always achieve the desired result.

[0014] It is therefore an object of the invention to provide a method for generating projection data on the basis of measurement signals from a radiation detector having a plurality of sensor pixel electrodes, which method enables improved image quality compared to conventional approaches for a given data transmission rate.

[0015] This object is achieved by means of a method for generating projection data on the basis of measurement signals of a radiation detector having a plurality of sensor pixel electrodes, evaluation units connected downstream of the plurality of sensor pixel electrodes and a module electronic element connected downstream of the evaluation units according to claim 1, by a radiation detector according to claim 10 and by an imaging system according to claim 11.

[0016] In the method according to the invention for generating projection data on the basis of measurement signals from a radiation detector having a plurality of sensor pixel electrodes, evaluation units connected downstream of the plurality of sensor pixel electrodes, and a module electronics element connected downstream of the evaluation units, measurement signals are detected by the sensor pixel electrodes.

[0017] In this context, a radiation detector is understood to mean a device that detects electromagnetic waves. The radiation detector preferably comprises an X-ray detector.

[0018] Furthermore, a counting rate assigned to the respective sensor pixel electrodes is determined based on the measurement signals in the evaluation units. The counting rate is defined as the number of measurement signals per unit of time.

[0019] For each pixel of the radiation detector, preferably a plurality of energy-dependent counting rates are determined for different energy threshold values ​​or electronic thresholds of an evaluation unit of the radiation detector.

[0020] Furthermore, at least one additional data processing step is carried out in the evaluation units, wherein processed count rate data is generated such that a data volume to be transmitted by the evaluation units is reduced compared to the data volume that would occur without the additional data processing step.

[0021] The processed count rate data is transmitted to the downstream module electronics element.

[0022] Finally, the downstream module electronics element generates projection data based on the processed count rate data. Advantageously, the calculation in the evaluation units allows for measurement-dependent configuration and adjustment of the amount of transmitted data at an early stage, adapting to the available data transmission capacities so that these can be utilized more effectively and enabling the transmission of the complete measurement information. By reducing the data volume already in the evaluation units, the performance of the components in the module electronics element can be reduced if necessary, thus saving resources and costs.In the best case, all calculations are transferred to the level of the evaluation units, so that the evaluation by the module electronics element can be completely omitted and thus an entire intermediate level of data collection and data processing in the radiation detector can possibly be dispensed with.

[0023] The radiation detector according to the invention, preferably an X-ray detector, has a detection unit that generates a detection signal for radiation, in particular X-rays, impinging on the detection unit. The detection unit has a plurality of sensor pixel electrodes. The radiation detector according to the invention also has a plurality of evaluation units that, based on the detection signal, determine a set of measured values ​​for X-rays impinging on the detection unit. The measured values ​​can, for example, relate to counting rates of counting events recorded with the aid of the radiation detector. They can also relate to time intervals between individual counting events, counting values, intensity values, or photon rates in a detector pixel. The set of measured values ​​usually comprises, as mentioned above, several counting rates that are determined simultaneously for a single detector channel.The count rates determined simultaneously for a single detector channel are determined, in particular for multiple energy thresholds, with energy threshold values ​​assigned to each of them that differ from one another. Furthermore, the radiation detector according to the invention also comprises a modular electronic element.

[0024] Such a radiation detector can be designed, for example, as a quantum-counting or photon-counting X-ray detector. In this case, the aforementioned detection unit of the X-ray detector according to the invention can, in particular, comprise a detection region for generating, for example, charge pulses as a detection signal for X-rays absorbed by the detection unit. The detection signal and, in particular, the charge pulses are thus particularly suitable for determining the energy of the absorbed X-rays.

[0025] The evaluation units can, in particular, be integrated into a so-called ASIC (Application Specific Integrated Circuit) or implemented in the form of an ASIC. In particular, the detection unit and at least parts of the evaluation units can be included in the aforementioned detector channel.

[0026] As already mentioned, the radiation detector according to the invention has a plurality of sensor pixel electrodes for detecting measurement signals.

[0027] The radiation detector according to the invention also has a plurality of evaluation units connected downstream of the sensor pixel electrodes for determining a counting rate based on the measurement signals in the respective evaluation units. The evaluation units are further configured to perform at least one additional data processing step. In the at least one additional data processing step, processed counting rate data is generated in such a way that the amount of data to be transmitted by the evaluation units is reduced compared to the amount of data that would occur without the additional data processing step.

[0028] The processed count rate data are transmitted from the evaluation units to a downstream module electronics element.

[0029] The radiation detector according to the invention also has a modular electronics element connected downstream of the evaluation units for generating projection data based on the processed count rate data. The radiation detector according to the invention shares the advantages of the method according to the invention for generating projection data based on measurement signals from a radiation detector.

[0030] According to the invention, an imaging system, preferably an X-ray imaging system, in particular a CT system, is further proposed, comprising a radiation source for emitting radiation, preferably X-rays, and a radiation detector according to the invention, preferably an X-ray detector, for detecting the radiation emitted by the radiation source.

[0031] The essential components of the radiation detector according to the invention can predominantly be implemented as software components executed in a processor. This particularly applies to the functions of the evaluation units. In principle, however, some of these components can also be implemented as software-supported hardware, for example as ASICS or FPGAs or the like, particularly when particularly fast calculations are required. Implementation as ASICS is particularly suitable for the evaluation units, and implementation as FPGAs is particularly suitable for the module electronics element. Likewise, the required interfaces, for example when only data from other software components is required, can be implemented as software interfaces. However, they can also be implemented as hardware interfaces that are controlled by suitable software.

[0032] A largely software-based implementation has the advantage that previously used evaluation units and / or module electronic elements of imaging systems, in particular X-ray imaging systems or CT systems, can be easily retrofitted by a software update in order to operate in the manner according to the invention. In this respect, the object is also achieved by a corresponding computer program product with a computer program that can be loaded directly into a memory device of one of the evaluation units and / or the module electronic elements of an imaging system, with program sections to carry out all steps of the method according to the invention when the program is executed in the evaluation units and / or module electronic elements. Such a computer program product can, in addition to the computer program, optionally contain additional components such as documentation and / or additional components, also hardware components, such asHardware keys (dongles etc.) to use the software.

[0033] A computer-readable medium, such as a memory stick, a hard disk, or another portable or permanently installed data storage device, can be used for transport to the evaluation unit and / or module electronics element and / or for storage on or in the evaluation unit and / or the module electronics element. The computer unit can store the program sections of the computer program that can be read and executed by a computer unit. For this purpose, the computer unit can, for example, have one or more cooperating microprocessors or the like.

[0034] Further, particularly advantageous embodiments and developments of the invention emerge from the dependent claims and the following description, wherein the independent claims of one claim category can also be developed analogously to the dependent claims of another claim category.

[0035] In one embodiment of the method according to the invention for generating projection data based on measurement signals from a radiation detector, processing is performed such that the processed count rate data can be transmitted to the downstream module electronics element with a maximum possible bit width per specified transmission cycle. Advantageously, the bit width of the processed count rate data to be transmitted is adapted to the maximum possible bit width, so that the transmission capacity between the evaluation units and the module electronics element is fully utilized. In this way, maximum performance can be achieved without data loss.

[0036] In a preferred variant of the method according to the invention for generating projection data based on measurement signals from a radiation detector, count rates associated with a plurality of different energy thresholds are determined, and when generating the processed count rate data, count rates associated with higher energy thresholds are determined as the difference to count rates of lower energy thresholds. By forming the difference, lower values ​​can be formed, for which less bit width is required for transmission. This advantageously allows the required data transmission capacity to be reduced without causing data loss during transmission.

[0037] The count rates assigned to higher energy thresholds are preferably expressed by coefficients of a fitting function. Such a fitting function preferably comprises a series of basis functions whose coefficients are to be determined. Such a series of basis functions is preferably designed as a power function. Particularly preferably, the fitting function comprises a Taylor series. Advantageously, the amount of data to be transmitted can be further reduced because the coefficients require less bit width than the complete values ​​of the count rates. Preferably, an offset value is specified for count rate values ​​assigned to an energy threshold, and for the remaining energy thresholds, the coefficients of a Taylor series are specified, which indicates the course of the count rates as a function of the energy of the energy thresholds. Advantageously, the bit width of the data to be transmitted can be particularly greatly reduced in this way.

[0038] In a variant of the method according to the invention for generating projection data on the basis of measurement signals from a radiation detector, the bit width of the processed counting rate data to be transmitted between the evaluation unit and the downstream module electronic element is predetermined as a function of the level of the expected flux rate of the radiation and the corresponding counting rate, thus optimizing the utilization of the possible transmission rate.

[0039] The measurement signals from different pixels are preferably acquired, in particular read out, using different acquisition modes, in particular read out modes. The number of measurement signals per pixel can thus advantageously be reduced if measurement signals are only transmitted for a portion of the energy thresholds per pixel. The measurement signals from neighboring pixels are preferably acquired, in particular read out, at different energy thresholds. For example, measurement signals for a first and second energy threshold are read out for a first subgroup of pixels, and measurement signals for the first and a third energy threshold are acquired, in particular read out, for a second subgroup of pixels that differs from the first subgroup. The missing measurement values ​​can be supplemented in each case with the aid of correlation corrections. The two subgroups of pixels preferably form an alternating pattern, preferably a checkerboard pattern.By combining the measurement signals from different pixels, the spectral information can be subsequently supplemented if necessary. Alternatively or additionally, so-called threshold mixing can be used, in which the measurement signals from several different energy thresholds of a pixel are combined, thus reducing the amount of data to be transmitted, although this also reduces the spectral resolution.

[0040] The additional data processing step preferably includes taking coincidence information into account when determining the processed count rates. Advantageously, the coincidence information is already taken into account and calculated in the evaluation units, so that the amount of data to be transmitted from the evaluation units to the module electronics element can be reduced, since the coincidence information no longer needs to be transmitted to the module electronics element because it has already been processed.

[0041] Particularly preferably, the additional data processing step comprises taking into account one of the following types of coincidence information when determining the processed count rates: - real coincidences through signal splitting - Random coincidences due to simultaneous events or counting events.

[0042] Random coincidences are generated by simultaneous events and not by signal splitting. These simultaneous events can be measured between non-adjacent pixels. They should be counted as different counts. It is also possible to estimate the number of random coincidences from a temporal overlap within a pixel: An event generates a typical signal duration t and a signal level above a threshold. If a new event occurs during this time period, the time period during which the signal level remains above the threshold is extended. If a time duration t_exp is greater than t, a pile-up event (i.e., two temporally overlapping signals) can be assumed. In this case, the random coincidence counter is incremented at all subsequent times t_exp until the signal falls below the threshold again. Such an approach is described in US Pat. No. 9,057,791 B2.

[0043] Coincidence information can be considered statistically by combining a set of counts recorded within a time interval, preferably 200 milliseconds. Alternatively, coincidences can also be considered directly for each event.

[0044] In one embodiment of the method according to the invention for generating projection data based on measurement signals from a radiation detector, the coincidence values ​​or coincidence information are therefore considered on an event-based basis. For example, a counting event is assigned to only one pixel and suppressed for the neighboring pixel. This advantageously reduces the computational effort compared to statistical evaluation. Furthermore, the temporal resolution of the measured counting rates is increased. Furthermore, the calculation is advantageously much faster than with a procedure based purely on statistical data. A temporal or statistical distribution can also serve as the basis for assigning events to a pixel. Such calculation can also be performed depending on the X-ray flux, the current counting rate, or the degree of pileup.

[0045] Optionally, the calculation steps in the evaluation units can also be performed only in high-flow cases, when the amount of data to be transmitted is particularly high. In contrast, in low-flow cases, where the counting rate is low, a conventional procedure with calculation in the module electronics element can be used if the data transmission is not limited by the hardware due to the low data rate.

[0046] In one embodiment of the method according to the invention, the radiation detector comprises one of the following detector types: - an X-ray detector, - a quantum-counting X-ray detector, - a photodetector.

[0047] The method according to the invention can advantageously be applied to different types of radiation detectors. However, it is particularly preferred to apply the method according to the invention to a quantum-counting X-ray detector of a CT system.

[0048] The invention will be explained in more detail below with reference to exemplary embodiments in the accompanying figures. In the various figures, identical components are provided with identical reference numerals. They show: Fig. 1 is a diagram illustrating a counting rate-energy relationship used to reduce the data to be transmitted in a method for generating projection data based on measurement signals of a radiation detector according to an embodiment of the invention, Fig. 2 is a diagram illustrating an adaptation of the data transmission bandwidth of the counting information to be transmitted to a specific application according to a second embodiment of the method for generating projection data based on measurement signals of a radiation detector, Fig. 3 is a diagram showing a pixel array of an X-ray detector in which the selection of energy thresholds to which the count rates are transmitted is arranged in a checkerboard pattern, Fig. 4 a graph symbolising a counting rate as a function of time for a pixel and an energy threshold, Fig. 5 is a diagram illustrating the change in the assignment of count events to energy thresholds of two pixels of an X-ray detector used for carrying out a method according to an embodiment of the invention, Fig. 6 is a flowchart illustrating a method for generating projection data based on measurement signals from a radiation detector according to an embodiment of the invention, Fig. 7 a schematic representation of a radiation detector according to an embodiment of the invention.

[0049] In Fig. 1 shows a diagram 10 illustrating a counting rate-energy relationship used to reduce the data to be transmitted within the framework of a method for generating projection data based on measurement signals from a radiation detector having a plurality of sensor pixel electrodes, a plurality of evaluation units connected downstream of the sensor pixel electrodes, and a modular electronic element connected downstream of the evaluation units, according to an exemplary embodiment of the invention. Thus, diagram 10 shows the counting rate ZR of an X-ray detector as a function of energy (in keV). Furthermore, diagram 10 shows four energy values ​​of four energy thresholds S1, S2, S3, S4 with the values ​​20 keV, 30 keV, 40 keV, and 70 keV.

[0050] In the Fig. 1, the count rate value of the lowest energy threshold S1 is used as offset ZR offand the count rate values ​​of the remaining thresholds S2, S3, S4 are transmitted as coefficients of a polynomial of order 3. In this way, the need for high bandwidth when transmitting the count rate values ​​can be greatly reduced.

[0051] In Fig. 2 shows a diagram 20 which illustrates an adaptation of the data transmission bandwidth of the counting information to be transmitted to a specific application according to a second exemplary embodiment of the method for generating projection data based on measurement signals from a radiation detector. In the second exemplary embodiment, the bit width for transmitting the data between the evaluation unit and the module electronic element is reduced in that the counting rate assigned to the second energy threshold S2 is not transmitted at all and the counting rate Z3 assigned to the third energy threshold is transmitted only as a ratio value Z3 / Z1 to the counting rate Z1 assigned to the first energy threshold S1. This reduction is useful, for example, if the counting rate Z3 assigned to the third energy threshold S3 is only required for a clinical question.The bit width for transmission can therefore be variably adjusted depending on the application scenario. This allows the available bit width to be optimized for the actual expected data values, allowing multiple pieces of information to be transmitted. If a high flow rate and correspondingly high counter readings are expected, partial saturation can also be deliberately planned.

[0052] In Fig. Figure 3 shows a diagram 30 illustrating a pixel array of an X-ray detector in which the energy thresholds S1, S2, S3, and S4, to which the count rates are transmitted, are arranged in a checkerboard pattern. Thus, different readout modes are configured for different pixels of the detector surface. This allows the data rate to be transmitted to be reduced while still achieving full spectral resolution, albeit with a reduced spatial resolution.

[0053] In Fig. 4 shows a graph 40 which shows a counting rate ZR(t, Pi, Si) as a function of time t for pixel P i and energy thresholds S i The illustration is intended to illustrate a variant of the method for generating projection data based on measurement signals of a radiation detector with a plurality of sensor pixel electrodes, a plurality of evaluation units connected downstream of the sensor pixel electrodes and a module electronic element connected downstream of the plurality of evaluation units according to an embodiment of the invention, in which count values ​​are offset against one another over a predetermined time readout interval. Fig. 4 referenced embodiment, a simple calculation step is carried out based on the counter readings, which different pixels P iassigned, after a readout interval, in this case 200 µs. This involves a summary and calculation of counting rates ZR(t, P i , S i ) to a single counting rate Z(P i , S i ) for the entire time interval of 200 µs.

[0054] Thus, a calculation of the coincidence information between two neighboring pixels P i possible: T1=t1−0.5*C11; T2=t2+0.5*C11.

[0055] Where t1 / 2 is the count rate value of the first / second energy threshold, and C11 is the value for the coincidence between the lower threshold S1 of the considered pixel P1 and the lower threshold S1 of the neighboring pixel P2. T1 / 2 is the corrected count rate value of the lower or upper energy threshold of the pixel P. iHere, a count rate-dependent addition of the coincidence values ​​is also possible. For example, in a truly high-flow case, the statistical error due to coincidence can be neglected, and in the otherwise used count rate range, the coincidence information can be integrated into the data to be transmitted without increasing the data rate at the interface between the evaluation unit and the electronic module element.

[0056] In Fig. 5 shows a diagram 50 which illustrates the change in the assignment of count events e1(P1), e1(P2) to energy thresholds S1, S2 of two pixels P1, P2 of an X-ray detector which is used for carrying out a method according to an embodiment of the invention. In this embodiment, the calculation of coincidences with the measured energy thresholds in the evaluation unit is carried out on an event-based basis. This means that in connection with Fig. The shift explained in Figure 4 occurs for individual count values. This calculation leads to a shift in the event of a coincidence between the lower energy threshold of the two pixels P1, P2 to the upper energy threshold, thus correcting the charge division of two pixels P1, P2. The effect of the calculation is then comparable to "next neighbor blocking," but is much faster than, for example, true charge summing. This calculation logic could also have a balancing effect with a temporal or statistical distribution between the pixels. Here, too, a flow-dependent admixture would be conceivable, for example, via scaling based on the measured pileup degree.

[0057] In Fig. 6 shows a flow chart 600 which describes a method for generating projection data PD based on measurement signals of a radiation detector 1 (see Fig. 7) with a plurality of sensor pixel electrodes 2, the plurality of sensor pixel electrodes 2 (see Fig. 7) downstream evaluation units 3 and one of the evaluation units 3 (see Fig. 7) downstream module electronic element 4 (see Fig. 7) is illustrated.

[0058] In step 6.I, measurement signals MS are detected by the sensor pixel electrodes 2.

[0059] In step 6.II, a respective counting rate ZR is determined based on the measurement signals in the evaluation units 3.

[0060] In step 6.III, an additional data processing step is performed in the evaluation units 3. This generates processed count rate data VZR whose data volume is reduced compared to the original count rates ZR.

[0061] In step 6.IV, the processed counting rate data VZR are transmitted to the downstream module electronic element 4.

[0062] In step 6.V, projection data PD are generated by the downstream module electronic element 4 based on the processed counting rate data VZR.

[0063] In Fig. Figure 7 shows a schematic representation of a radiation detector 1, in this case an X-ray detector 1 of a CT system, according to an embodiment of the invention. The X-ray detector 1 comprises a plurality of sensor pixel electrodes 2 for detecting measurement signals MS.

[0064] The X-ray detector 1 also comprises a plurality of evaluation units 3 connected downstream of the plurality of sensor pixel electrodes 2. The evaluation units 3 are configured to determine a counting rate ZR on the basis of the measurement signals MS and to generate processed counting rate data VZR, the amount of data to be transmitted of which is reduced compared to the amount of data that would occur without the additional data processing step.

[0065] The X-ray detector 1 has a module electronics element 4 connected downstream of the evaluation units 3 for generating projection data PD by the downstream module electronics element 4 on the basis of the processed counting rate data VZR.

[0066] Finally, it should be pointed out that the features of all exemplary embodiments or further developments disclosed in the figures can be used in any combination. Finally, it is also pointed out that the X-ray detector described in detail above, the X-ray imaging system, which can be modified in a variety of ways by a person skilled in the art without departing from the scope of the invention. For example, the X-ray detector can also be designed as a ring-shaped detector that completely encloses a measuring space of an imaging system in one direction. Furthermore, the use of the indefinite articles "a" or "an" does not exclude the possibility that the features in question can be present in multiple copies. Likewise, the term "unit" does not exclude the possibility that the components in question consist of several interacting subcomponents, which can also be spatially distributed if necessary.Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 9 057 791 B2

[0042]

Claims

[1] Method for generating projection data (PD) on the basis of measurement signals of a radiation detector (1) with a plurality of sensor pixel electrodes (2), evaluation units (3) connected downstream of the plurality of sensor pixel electrodes (2), and a module electronic element (4) connected downstream of the evaluation units (3), comprising the steps: - Acquisition of measurement signals (MS) by the sensor pixel electrodes (2), - Determining a respective counting rate (ZR) based on the measurement signals in the evaluation units (3), - carrying out at least one additional data processing step in the evaluation units (3), whereby processed counting rate data (VZR) are generated in such a way that a data volume to be transmitted by the evaluation units (3) is reduced compared to the data volume which would occur without the additional data processing step, - Transferring the processed count rate data (VZR) to the downstream module electronic element (4), - Generation of projection data (PD) by the downstream module electronic element (4) based on the processed count rate data (VZR). [2] Method according to claim 1, wherein the processing is carried out in such a way that the processed counting rate data (VZR) can be transmitted to the downstream module electronic element with a maximum possible bit width per specified transmission cycle. [3] Method according to claim 1 or 2, wherein counting rates (ZR) which are assigned to a plurality of different energy thresholds (S1, S2) are determined and, in the generation of the processed counting rate data (VZR), counting rates (ZR) which are assigned to higher energy thresholds are determined as a difference to counting rates of lower energy thresholds. [4] Method according to claim 3, wherein the count rates (ZR) to one of the energy thresholds (S1, S2, S3, S4) are expressed as an offset and the count rates to the remaining energy thresholds are expressed by coefficients of a fit function. [5] Method according to one of the preceding claims, wherein the bit width of the processed counting rate data (VZR) to be transmitted between the evaluation units (3) and the downstream module electronics element (4) is predetermined as a function of the level of the expected flow rate and counting rate, thus optimizing the utilization of the possible transmission rate. [6] Method according to one of the preceding claims, wherein the detection of the measurement signals (MS) from different pixels is carried out by different detection modes, whereby the measurement signals (MS) and counting rate data (ZR) determined therefrom can be clearly assigned to a specific pixel. [7] Method according to one of the preceding claims, wherein the additional data processing step comprises taking into account coincidence information when determining the processed count rates (VZR). [8] Method according to one of the preceding claims, wherein the additional data processing step comprises taking into account one of the following types of coincidence information in determining the processed count rates (VZR): - real coincidences through signal splitting, - Random coincidences. [9] Method according to one of claims 7 to 8, wherein consideration of the coincidence information is event-based. [10] Radiation detector (1), comprising: - a plurality of sensor pixel electrodes (2) for detecting measurement signals (MS), - a plurality of evaluation units (3) connected downstream of the sensor pixel electrodes (2) for determining a counting rate (ZR) on the basis of the measurement signals (MS) in the respective evaluation units (3) and for carrying out at least one additional data processing step in the evaluation units (3), wherein processed counting rate data (VZR) are generated in such a way that a data volume to be transmitted by the respective evaluation unit (3) is reduced compared to the data volume that would occur without the additional data processing step, and for transmitting the processed counting rate data (VZR) to a downstream module electronic element (4), - a module electronics element (4) connected downstream of the evaluation units (3) for generating projection data (PD) by the downstream module electronics element (4) on the basis of the processed counting rate data (VZR). [11] Imaging system, preferably X-ray imaging system, in particular CT system, with a radiation source (R) and a radiation detector (1) according to claim 10. [12] Computer program product comprising a computer program which is directly loadable into a memory device of an imaging system, with program sections for carrying out all steps of the method according to one of claims 1 to 9 when the computer program is executed in the X-ray imaging system. [13] Computer-readable medium on which program sections are stored which can be read and executed by a computer unit in order to carry out all the steps of the method according to one of claims 1 to 9 when the program sections are executed by the computer unit.

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