Operation of a detector device

Abstract

Detector device (4) for a computed tomography system (1), which detector device (4) has a number of individual detectors (20a, 20b, 20c, 20d, 20m) and at least one detector control unit (5) each having a plurality of components and is designed such that it can be switched into at least one power-saving mode in which at least some of the components of the individual detectors (20a, 20b, 20c, 20d, 20m) are deactivated and at the same time at least some of the components of the detector control unit (5) are not deactivated.

Description

The invention relates to a detector device for a computed tomography system, which has a number of individual detectors and at least one detector control unit and a voltage supply for the individual detectors and the detector control unit. The invention furthermore relates to a computed tomography system having such a detector device and to a method for operating a detector device of a computed tomography system.Such detector devices are used in particular in computed tomography systems. The individual detectors are generally analog components (therefore the individual detectors are also frequently referred to as "analog front end") which comprise the actual detector elements which convert the incoming x-ray radiation into electrical signals as measurement data as individual pixels of the detector, and at least one highly integrated analog-to-digital converter (ADC) and a multiplexer which is connected upstream of the ADC and which transfers the analog signals of the detector elements or pixels to the common ADC. How many such individual detectors have a detector device depends on the one hand on the total number of detector elements or pixels of the detector and on the other hand on the number of pixels or detector elements per individual detector. For example, there are "smaller" single detectors that include only 16 channels for 16 single pixels and a common multiplexer with a downstream ADC. However, there are also individual detectors with 64 channels or more. For a detector device with only 64 or 128 pixels, it would therefore be sufficient in principle to use only one or two individual detectors with 64 channels each. As a rule, however, a plurality of individual detectors is required. The measurement data digitized by the ADCs are sent by the individual detectors to the detector control unit, which serves not only to take over the measurement data or raw data for image reconstruction, but also to actuate the individual detectors, i.e. to transmit corresponding control signals to them, for example in order to read out the measurement data in a synchronized manner, etc. The electronics of the detector control unit usually operate digitally, for which reason the detector control unit is generally also referred to as a "digital backend".In order to supply the large number of pixels (conventional computed tomography systems have approximately 50,000 pixels or even more) and the electronics for controlling the individual detectors and for transmitting the relatively large amounts of data, namely the acquired projection data or raw data, these detector devices require a great deal of power. Depending on the detector type and number of individual detectors, a power of up to 400 watts or even more is currently required in individual cases. The main portion of the required power is thereby dispensed with for the analog individual detectors. Thus, roughly estimated, these require about 95% of the total power of the detector device. Since the number of pixels (and thus usually also of the individual detectors) increases steadily--computed tomography systems with more than 100,000 pixels are currently being planned--an even higher power requirement is to be assumed in the future.Regardless of the current use of the medical imaging system or computed tomography system, the maximum power for the complete detector electronics has always been used up to now. However, in clinics or radiologic practices, it frequently occurs that a computed tomography system is operated even over a longer period of time without direct patient examination, i.e. without raw data for images currently being acquired. This time period may be only a few minutes, for example between two scans of a patient, if the patient has to be rearranged or other organs are to be detected or a contrast medium is first given. However, this period of time can also last a few hours up to half a day or even over a night between different patients. In order to reduce unnecessary energy consumption during longer waiting times, there has hitherto only been the possibility of switching off the complete computed tomography system, which in turn takes the expense of the time required to put the device back into operational readiness. It is therefore not possible in many cases to switch off the complete system, in particular if it is clear that the next patient examination takes place in the foreseeable time, but also, if appropriate, overnight, if, for example, accidents have to be expected.The document DE 10 2005 014 119 A1 discloses systems and methods for managing the energy consumption of a medical imaging detector by using trigger signals, environmental state data and / or determining a variable time interval trigger event that is unique for each energy consumption state.The publication DE 10 2014 226 686 A1 discloses a device and a method for transmitting signals in an imaging medical system.The document DE 10 2012 204 601 A1 discloses an X-ray imaging apparatus comprising a determination device for determining an operating state of a connected apparatus and a display control device configured to control a transition to a masking display state according to the determined operating state.The document DE 10 2005 049 228 B4 discloses a detector having an array of photodiodes.It is an object of the present invention to specify a detector device, a corresponding computed tomography system and a method for operating a detector device, in which the power requirement can nevertheless be reduced.This object is achieved by a detector device according to claim 1, a computed tomography system according to claim 11 and a method for operating a detector device according to claim 12.As described at the beginning, the detector device according to the invention has a number (i.e. at least one, but preferably a plurality) of individual detectors, in particular in the form of the analog front ends explained above, and a detector control unit, in particular in the form of the digital backend described above. This detector control unit can also comprise a plurality of subunits or modules which are assigned, for example, to groups of individual detectors and are coupled to a common unit in order in turn to coordinate the groups with one another. Preferably, however, it is a single detector control unit to which all individual detectors are connected. The individual detectors and the detector control unit each have, as usual, a plurality of components, such as, for example, operational amplifiers, sample-and-hold elements, analog multiplexers ADCs, etc. in the individual detectors or controllers, power supplies, etc. in the detector control unit.According to the invention, this detector device is now designed such that it can be switched over into at least one power-saving mode in which at least some of the components of the individual detectors are deactivated and at the same time at least some of the components of the detector control unit are not deactivated. If, in particular, the components of the individual detectors (such as, for example, the operational amplifiers and / or sample hold elements and / or multiplexers and / or ADCs) which consume a particularly large amount of energy are deactivated when they are not required, considerable amounts of energy can be saved overall.Since essential components remain active in the detector control unit (i.e. the digital backend), even in the power saving mode, the full power readiness of the computed tomography system can nevertheless be established at any time considerably more quickly than when the entire system is switched off. This is particularly due to the fact that a) the firmware of the controllers on the digital backend does not have to be reconfigured, b) the training sequence for the data transmission within the different sub-controllers (which may have the tasks of correctly driving the front-end modules, correctly configuring them and converting the data coming from the front-end modules and into a defined protocol) does not have to be carried out again in order to ensure a secure data transmission, c) the data interface from the detector to the imaging computer does not have to be checked again for correct and error-free data transmission, d) the control communication network does not have to be reconstructed and verified again, e) the existing and stored calibration data do not have to be generated again and stored again in the digital backend electronics for the analog frontends.Therefore, the computed tomography system-unlike previously-can not only be switched on and off, but it can additionally be switched back and forth in the switched-on state between at least one such power saving mode and a further operating state (referred to below as "scan mode") in which raw data can be acquired.The amount of energy actually saved depends on which components are deactivated in the power saving mode and which remain active. This in turn depends on how quickly the detector device can be switched back from the power saving mode to the scanning mode. When the individual detectors are completely deactivated, up to 95% of the energy can be saved in the power saving mode, as will be explained later. If only parts of the individual detectors are deactivated, in order to be able to switch back into the scanning mode particularly quickly, for example, up to 75% of the energy can be saved.In this case, it is also possible in principle to combine different power-saving modes, i.e. for example, in the case of brief pauses of only a few minutes, the system is switched over into a first power-saving mode in which only a few components of the individual detectors that consume particularly much energy are deactivated, but from which it is possible to switch back into the scanning mode in a few seconds, and in the case of expected longer pauses, for example, the individual detectors are completely deactivated in a second power-saving mode. It is also possible here for a changeover to be made if appropriate between the different power-saving modes. In principle, however, considerable energy can already be saved if only one power saving mode is available.A computed tomography system according to the invention is equipped with such a detector device according to the invention.A method according to the invention for operating a detector device of a computed tomography system of the aforementioned type is characterized in that after a switch to a power saving mode, at least some of the components of the individual detectors are deactivated and at the same time at least some of the components of the detector control unit are not deactivated.With the aid of the invention, it is therefore possible to drastically reduce the power consumption of the computed tomography system outside the actual operation for patient examination and thus to provide an overall more energy-saving system. A further advantage is that the heat generation of the detector device is on average lower, since no power is absorbed by the individual detectors during the standby times and is emitted in the form of waste heat. In this way, additional energy for cooling the detector device can be saved. Furthermore, the reliability of the detector device is increased since the average operating temperature is thereby lowered.Further, particularly advantageous embodiments and developments of the invention are evident 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 and the features of different exemplary embodiments can be combined to form new exemplary embodiments.In a particularly preferred variant, the detector device is designed such that certain components of the detector control unit that are not required in the power-saving mode are also deactivated in a power-saving mode. This means that the detector control unit is then also deactivated insofar as only the components required in the power saving mode remain active. These components, which are also required in the power-saving mode, are, for example, besides the components which, as explained later, are required to switch back from the power-saving mode, one or more controllers which receive the switching signals for switching on / off from the system controller and in turn generate these switching signals. By contrast, it is possible to switch off e.g. the measurement data generation unit, the synchronization unit, the monitoring unit of the individual detectors, and the communication unit within the detector control unit.If, as explained later for a preferred exemplary embodiment, the detector device is designed such that it allows the switching to different power-saving modes, for example a first power-saving mode for short pauses and particularly fast switching back into the scan mode and a second power-saving mode for longer pauses, this variant is preferably used only in the second power-saving mode, since switching off components of the detector control unit can be associated with a somewhat increased time outlay for switching back into the scan mode.In order to switch over into a power-saving mode, the individual detectors can preferably each have a deactivation device. This deactivation device can be designed to deactivate specific components (i.e. for example the analog components described above) of the individual detector in question, for example by outputting a suitable deactivation command. This procedure is particularly suitable for switching to a power saving mode, from which switching back to the scanning mode can be very quickly performed.The deactivation device can comprise, for example, an interpreter unit in an input / output interface (I / O interface) of the individual detector, which interprets specific commands coming from the detector control unit and / or a system controller of the imaging system accordingly as commands or signals for switching to the power-saving mode or for switching back to the scanning mode. These may also be conventional commands which are already transmitted to the individual detectors in any case, such as a "scan preload command", which is usually transmitted by the system controller in order to prepare a scan, and which is then followed a so-called "make data signal" for initiating the actual data acquisition a short time (for example 1 to 2 s). This make data signal is generally applied as long as data are acquired. The switching off of the make data signal can in turn be regarded as a signal or event in order to switch over into the power saving mode and to deactivate the relevant components of the individual detector.A detector device also usually has a voltage supply arrangement for the individual detectors and the detector control unit. This is, for example, one or more power supply units with a power supply connection, e.g. to the power supply network, which is provided externally, and a corresponding power supply system within the detector device for distributing the electrical power to the components of the detector control unit and to the individual detectors. This voltage supply arrangement is preferably predominantly integrated into the detector control unit, for example by integrating one or more power supply units into the detector control unit and also providing the corresponding lines (e.g. in the form of conductor tracks, cabling, plugs or the like) and connections for the individual detectors. In principle, however, it could also be formed in a separate unit to which the individual detectors and the detector control unit are connected via corresponding voltage supply lines.The voltage supply arrangement preferably has at least one switching device and is designed such that in a first switching state of this switching device, which corresponds to a power-saving mode (or power-saving switching state), the voltage supply of the individual detectors is interrupted and the voltage supply for the detector control unit is still maintained. In this power saving mode, the power requirement can be reduced to a very small fraction, for example-as explained above-to around 5% or less, since the voltage supply of the individual detectors can be switched separately from the voltage supply of the control electronics and thus the individual detectors are no longer supplied with energy at all in the power saving mode.In this procedure, the voltage supply arrangement and / or the switching device are particularly preferably designed such that, in the first switching state of the switching device (i.e. in the power-saving mode), the voltage supply is additionally interrupted for specific components of the detector control unit that are not required in the power-saving mode. That is, just here-as explained above-the voltage supply for the drive unit is maintained only insofar as the components required in the power saving mode are still supplied.The switching device can be realized in various ways. Preferably, however, the switching device is integrated into the detector control unit, i.e. is formed as part of the latter.The switching device preferably comprises at least one switching unit and a switching control unit for controlling the switching unit. These components are then preferably also parts of the detector control unit.The switching device is particularly preferably designed such that in the first switching state at least the voltage supply for the switching unit or the switching units and the switching control unit is maintained, since with the aid of these, a switching back from standby mode to full operating mode is to take place.There are also various possibilities for realizing the switching unit(s). In principle, these could be separate switches, such as one or more MOSFETs or an arrangement of a plurality of switches, which are connected in between in the lines for the energy supply. The switching inputs of these switches can be controlled, for example, by the switching control unit. In order to keep the number of switches low, it is advantageous to arrange them, for example, in front of possible distribution nodes if, for example, a plurality of individual detectors are supplied with voltage from the same output of a power supply unit.In a variant which is constructed with as few additional components as possible and is therefore preferred, the voltage supply arrangement comprises at least one power supply unit, preferably a plurality of power supply units, each having at least one supply voltage input, an integrated switching unit and a supply voltage output, and a deactivation input for inputting a deactivation signal for the supply voltage output. Via this deactivation input, the integrated switching unit of the power supply unit can thus be switched with the aid of the deactivation command in such a way that no supply voltage is present any longer at the relevant supply voltage output. It is possible here for a plurality of supply voltage outputs to be connected simultaneously via a deactivation input or for a dedicated deactivation input to be present for each supply voltage input. Such a deactivation input, also referred to below as "enable input", is then connected to the switching control unit and receives from the latter the deactivation signal for deactivating the associated supply voltage output or the associated supply voltage outputs, so that the voltage supply to the individual detectors connected thereto is interrupted and is thus switched over into the standby mode.This deactivation signal (which could also be referred to as deactivation command) can be, for example, simply a logic switching state of a switching output of the switching control unit. By switching back the switching output of the switching control unit, the deactivation signal can then also be canceled again, so that the integrated switching units in the power supply units cancel the voltage supply interruption again and the supply voltage is present again at the supply voltage outputs and is thus switched back into the full operating mode. However, it would likewise also be possible for a special reactivation command to be sent from the switching control unit to the power supply unit or units, for example again to the deactivation input or to one or more separate activation inputs, in order to switch over again from the standby mode to the full operating mode.For their function, the individual detectors may each require some detector operating data, in particular calibration data or correction values. Such calibration data or correction values serve, for example, to compensate for hardware-dependent differences in the sensitivity of the various individual detectors. These calibration data are determined in a calibration method during the first startup of the detector device or of the computed tomography system and can then be stored in a system controller of the computed tomography system. During operation, the detector operating data, in particular calibration data, are stored in suitable memories of the individual detectors, so that the individual detectors can operate with these values. The calibration method can be carried out again at certain intervals, for example during maintenance of the system, in order to update the data. In addition to the calibration data or correction values, there are also other detector operating data which can be stored in a corresponding manner and can be respectively stored in the memories of the individual detectors for the respective operation, such as, for example, detector operating data or configuration data which specify which measurement range is used (whether, for example, a high-dose or low-dose recording), wherein the sensitivity of the respective individual detectors can be adjusted with the aid of the detector operating data, or detector operating data which influence the readout speed at the individual detectors, etc.The detector device preferably comprises a suitable detector operating data management unit which is designed to transmit detector operating data, preferably calibration data, to the individual detectors first after the voltage supply has been switched on again. The corresponding detector operating data can be taken, for example, from the memory of the system controller of the medical system, i.e., according to the invention, the computed tomography controller, or the system controller can be caused to transmit this detector operating data to the individual detectors, as in the case of a complete re-activation of the overall system. For this purpose, the detector operating data management unit is connected in terms of data technology to the individual detectors and the switching control unit in order to carry out this task in synchronization with the changeover from the standby mode to the full operating mode, i.e. to ensure that the individual detectors receive the respective detector operating data.In particular, the detector device preferably has a detector operating data management unit in such a way that before the switching device is switched to the first switching state, i.e. before the switching to the standby mode, detector operating data, preferably the aforementioned calibration data, are read out by the individual detectors and stored in a memory assigned to the individual detectors.This memory is particularly preferably a separate memory which is not identical to the memory in which the system control of the medical technology system has stored this data. When the voltage supply of the individual detectors is switched on again, i.e. when switching back from standby mode to full operating mode, the detector operating data can then be sent back from this memory to the individual detectors. The detector operating data management unit can consequently be the same detector operating data management unit which also provides for the transmission of the detector operating data to the individual detectors again. Reading out the detector operating data from the individual detectors independently of the system control before switching to the standby mode and storing these operating data for the individual individual detectors in a separate memory provided or reserved separately for this purpose, and sending them back to the individual detectors after switching back from the standby mode with the aid of a separate detector operating data management unit, has the advantage that the switching device can operate completely autonomously, i.e. without intervention in the system control of the medical system. In this case, it should be taken into account that the system control itself is a highly complex system and the outlay for the design of the detector device according to the invention can be significantly reduced by the autonomous detector operating data management unit having its own memory, which can preferably also be part of the switching device or at least of the detector control unit. This separate memory can preferably be a memory which is integrated into the detector control unit, for example. In principle, however, it is also possible to use a different memory area which is easily accessible for the detector operating data management unit but is also used by other components.As mentioned above, in a preferred variant, different power saving modes can be combined with one another. In this case, (only) specific components of an individual detector can particularly preferably be deactivated automatically with the aid of the deactivation device of the individual detector when data acquisition is complete. This can be effected, for example, as described above when the make data signal is canceled. The power saving mode is then preferably also automatically canceled in the case of a scan command, for example upon receipt of the scan preload signal, and switched back into the scan mode, so that the detector device is immediately ready to acquire raw data upon receipt of the subsequent make data signal.A changeover to another power saving mode, in which a voltage supply of the individual detectors is completely interrupted and therefore even more energy is saved, is, on the other hand, preferably initiated intentionally by the user by a command from a user interface if a longer pause is present. This power saving mode is then preferably also canceled again via the user interface.The invention is explained in more detail below with reference to the attached figures on the basis of exemplary embodiments. In this case, identical components are provided with identical reference numerals in the different figures. The following are shown: FIG. 1 shows a roughly schematic representation of an exemplary embodiment of a computed tomography system according to the invention, FIG. 2 is a partial block diagram of an embodiment of a detector device according to the invention, FIG. 3 is a partial block diagram of an exemplary embodiment of an individual detector of the detector device according to FIG. 2, FIG. 4 shows a flow diagram of an embodiment of a method according to the invention.FIG. 1 shows, by way of example and roughly schematically, a computed tomography system 1 according to the invention, which comprises a computed tomography device 30 and a system controller 2 with a user terminal 25.The system control 2 is shown here as a unit separate from the computed tomography device 30 and connected thereto via lines. In principle, however, it can also be integrated completely or partially into the computed tomography device 30.The computed tomography device 30 comprises a patient table 33 for supporting a patient P as the examination object P, wherein the patient table 33 is adjustable along a system axis 34 so that the patient P is movable into and through the measurement field. The system axis 34 is also referred to as the z-axis.The computed tomography apparatus 30 furthermore comprises in the usual manner a gantry 31 with a source-detector arrangement 32, 4 mounted rotatably about the system axis 34. the source-detector arrangement has an X-ray radiation source 32 and a detector device 4, which are aligned opposite one another on the gantry 31 in such a way that, during operation, an X-ray radiation emanating from the focus of the X-ray radiation source 32 impinges on the individual detectors of the detector device 4 through the measurement field (which is defined by space between the X-ray radiation source 32 and the detector device 4 through which the X-ray radiation beams pass). The individual detectors of the detector device 4 are structured into individual pixels which are arranged in a plurality of detector rows and columns. The individual detectors are spatially arranged in such a way that they offer a contiguous pixelated detector surface 35 on which the x-ray radiation impinges, so that spatially resolved projection data can be measured. The electronic structure of the detector device 4 is explained in more detail below with reference to FIGS. 2 and 3.Such a computed tomography system 1 is used for 3D image reconstruction, as is known. In order to record image data from an examination region (or what is known as a "region of interest" in the interior of the examination object P, e.g. a region with a specific organ), projection data from a multiplicity of different projection directions are captured during rotation of the source-detector arrangement. In the case of a so-called "spiral scan", for example, during a rotation of the source-detector arrangement, a continuous adjustment of the patient table 33 in the direction of the system axis 34 takes place simultaneously. The X-ray source and the detector thus move on a helical path around the patient P in this type of scan.The projection data represent the intensity values of the X-ray radiation attenuated by the patient P measured at the individual pixels. The projection data are sent as so-called raw data via a data channel D to the system controller 2, which has an image reconstruction device 28, in which the image data can be reconstructed from the interior of the patient P in the usual manner on the basis of the raw data. These can then be displayed, for example, on a display unit 26 of the user terminal 25 and / or stored in a memory and / or sent to other systems. The user terminal 25 furthermore comprises, inter alia, a keyboard 27 as an input device, with which a user can optionally set values for parameters, in particular for raw data acquisition and / or image reconstruction. Via this user terminal 25, for example, as will be described below, a command for switching to a specific power saving mode, referred to below as "standby mode", or for switching back from this standby mode can be input by the operator.The computed tomography apparatus 30, and thus also the detector device 4, is supplied with the required operating voltage or the required electrical power via a supply line V. In FIG. 1, this supply line V runs to the system control 2, which in turn is connected to a suitable energy supply network in clinic or practice (not shown). In principle, however, the computed tomography device 30 could also itself be connected to a suitable energy supply network. This depends, for example, on which components are present in the computed tomography device 30 in order to convert the voltage supplied by the power supply network into the voltages required by the components of the computed tomography device 30.As already explained at the beginning, it is disadvantageous in the prior art computed tomography systems that, in order to maintain a rapid operational readiness, the computed tomography system must be supplied with all components permanently with the required (maximum) electrical power, which is also required during the raw data acquisition.In order to greatly reduce this high energy input, the detector device 4 is designed here such that, in a first energy saving mode (referred to below as "acquisition ready mode"), certain components of the individual detectors 20 a, 20 b, 20 c, 20 d... 20m (analog front end) can be automatically deactivated if they are not currently used for data acquisition, and in addition the voltage supply of the individual detectors 20a, 20b, 20c, 20d... 20m and the voltage supply of the detector control unit 5 (digital backend) required for this purpose can be controlled separately in order to provide the individual detectors 20a, 20b, 20c, 20d... in a second energy saving mode, the above-mentioned standby mode in which even more energy is saved. 20m completely to be disconnected from the voltage supply.A construction of the detector device 4 suitable for this purpose is shown in FIGS. 2 and 3 in each case in the form of partial block diagrams, wherein for the sake of simplicity only roughly the components particularly relevant for this invention are shown schematically.FIG. 2 shows the detector device 4 with the detector control unit 5 and a plurality of individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mconnected thereto. The detector control unit 5 is in turn connected via the supply voltage line V and a data channel D to the system control 2 of the computed tomography system 1. Again, only those components are schematically shown by the detector control unit 5 which are required for the operation according to the invention with the possibility of separate disconnection of the voltage supply for the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 m. It is clear that this detector control unit 5 also has all further components which have conventional detector control units. The individual detectors 20 a, 20 b, 20 c, 20 d... 20m in FIG. 2 is only shown roughly schematically as individual blocks. A somewhat more detailed schematic representation of the structure of the individual detectors 20a, 20b, 20c, 20d,..., 20m can be seen from FIG. 3.Each of the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mcomprises a number of photodiodes 40 which form the individual detector elements or pixels of the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 m. An electrical signal is generated in the usual manner by the incidence of the X-ray radiation on the photodiodes. The photodiodes 40 are here merely representative of each type of radiation converters that convert X-ray radiation into electrical signals. Such an individual detector 20 a, 20 b, 20 c, 20 d,..., 20 mmay have 16, 32, 64, 128 or even more pixels, for example.The photodiodes 40 are each connected to ground GND and, for detecting the electrical signal generated by the incidence of the X-ray radiation, are connected to an operational amplifier 41, to which a capacitor 42 is connected in parallel in the usual manner. At the output of the operational amplifier 41 there is likewise in each case in the usual manner a sample-and-hold element 43, the outputs of these sample-and-hold elements 43 being in each case connected to a common multiplexer 44 for all pixels or detector channels. This multiplexer 44 reads out the signals of the individual detector channels in chronological succession and delivers all signals to an analog-to-digital converter (ADC) 45 in a temporal multiplex method. This then delivers the digitized measurement data to a preprocessing unit 46, which corrects the measurement data, for example, on the basis of predefined calibration data which are stored in a memory 47 and take account of the sensitivities for the individual pixels, and carries out further precalculations, such as the reformatting of the data into a specific data transmission protocol.The individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mare each connected to the detector control unit 5 via data channels DD. Via these data channels DD, the raw data can be transferred from the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mto the detector control unit 5 in each case and conversely control data, in particular detector operating data DB, e.g. calibration data DB, can also be taken over or transmitted. The connection of the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mto the data channel DD is effected in each case via an input / output interface 49. Configuration data which are used by the input / output interface 49 can be stored in a further memory 48. This input / output interface 49 also receives via the data channel DD specific commands for driving the various components of the respective individual detector 20 a, 20 b, 20 c, 20 d,..., 20 m, in particular the scan preloaod signal SP already mentioned above, in order to make the detector ready for a data acquisition and the make data signal MD, whereupon the data acquisition takes place and the individual signals of the photodiodes 40 are read out and processed as described.In the detector control unit 5, the data channels DD are connected here, for example, to an internal controller 17, which on the other hand is in turn connected via a data channel D to the system controller 2 and thus forwards the data from the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mto the system controller 2 and vice versa. It is clear that instead of a single controller 17 a plurality of controllers can also be used in parallel here or the controller 17 can consist of a plurality of sub-controllers and optionally further components.In addition, the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mare each supplied with the necessary voltage by the detector control unit 5. For this purpose, the individual detectors 20 a, 20 b, 20 c, 20 d... 20m are connected to the detector control unit 5 via supply lines VS as mentioned above. The connection is made here on the part of the individual detectors 20 a, 20 b, 20 c, 20 d... 20 mvia the input / output interface 49, however, a separate voltage supply interface may also be present. The detector control unit 5 also has a voltage supply arrangement 10 which comprises, inter alia, a plurality of power supply units 6 a, 6 b,..., 6 n. Each of these power supply units 6 a, 6 b,..., 6 nhas a supply voltage input 11, a supply voltage output 12 and a so-called "enable input" 13, that is to say a deactivation input 13. In each of the power supplies 6a, 6b... In FIG. 6 n, an internal switching unit 14 is located, which is designed such that, when a specific voltage potential is set at the enable input 13, i.e. a specific logic switching state is reached, the associated supply voltage output 12 is deactivated, i.e. no voltage is present there.The power supply units 6 a, 6 b,..., 6 nare connected with their supply voltage inputs 11 for example to the supply line V for the system control 2 and are supplied from there with an input voltage of 12 V. The supply voltage of 5V required for the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mis output at the supply voltage outputs 12. However, it is explicitly pointed out that these voltages are only examples and other voltage combinations are also possible in principle.The power of the individual power supply units 6 a, 6 b,..., 6 neach suffices for a plurality of individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mto be connected to a supply voltage output 12. In the exemplary embodiment shown in FIG. 2, these are in each case two individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mat a supply voltage output 12 of a power supply unit 6 a, 6 b,..., 6 n.In addition to the controller 17, the voltage supply arrangement 10 additionally comprises a switching control unit 7 which is likewise arranged in the detector control unit 5, for example in the form of a microcontroller or the like, for example on the same circuit board on which the power supplies 6 a, 6 b,..., 6 nare also located. The controller 17 and the switching control unit 7 are here coupled to one another by data technology or can communicate with one another.This switching control unit 7 has a switching output 15, referred to below as "enable output" 15, via which an enable signal ES can be applied to the enable inputs 13 of the power supplies 6 a, 6 b,..., 6 n, to which the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mare connected. This means that this switching control unit 7 is designed such that, for switching to the aforementioned standby mode, the enable output 15 is supplied as enable signal ES with the logic voltage level which is required to deactivate the associated supply voltage outputs 12 via the enable inputs 13 of the power supplies 6 a, 6 b,..., 6 n. The switching control unit 7 thus forms, together with the switching devices 14 in the individual power supplies 6 a, 6 b,..., 6 n, the switching device for switching from a full operating mode to a standby mode by the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 m no longer being supplied with the required operating voltage.In order to ensure that the required components of the detector control unit 5 are still supplied with voltage at least also in the standby mode, the detector control unit 5 is equipped with at least one additional power supply unit 6, which can be constructed, for example, in the same manner as the other power supply units 6 a, 6 b,..., 6 n. This means that this power supply unit 6 also has a supply voltage input 11 which is connected to the supply voltage line V for the system control 2, and a supply voltage output 12 at which the supply voltage required for the further components of the detector control unit 5, for example again 5 V, is output.As an example, it is shown here that a supply voltage input 16 of the switching control unit 7 is connected to the supply voltage output 12 of this power supply unit 6. The controller 17 is likewise supplied by this power supply unit 6 (not explicitly shown). Unlike in the case of the power supplies 6 a, 6 b,..., 6 nprovided for the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 m, however, the enable input 13 is not connected here to the enable output 15 of the switching control unit 7. Thus, even when switching to the standby mode, the supply voltage output 12 of this power supply unit 6 is not switched off and the switching control unit 7, the controller 17 and further components of the detector control unit 5 which are supplied with the supply voltage via this output are not deactivated. Of course, in addition to the power supply unit 6 shown, further power supplies can also be present which supply other components of the detector control unit 5 that are not to be switched off in the standby mode with the necessary voltage and which are likewise not deactivated via the enable signal ES.In order to activate the enable signal ES, i.e. in order to bring the enable output 15 of the switching control unit 7 to the appropriate switching state, a "standby command" SB can simply be sent from the system controller 2 to the detector control unit 5 via the data channel D. For this purpose, the system controller 2 can have a standby activation interface 3, for example in the form of a software component, with which a corresponding window is displayed on the display device 26 of the user interface 25, and the operator can give the corresponding standby command for switching to the standby mode via an input device 27 either with the aid of the keyboard or a mouse (not shown) or another pointing device. In an analogous manner, the user can also input a corresponding command in order to switch back from the standby mode, in which the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mare then supplied with the necessary operating voltage again. In the case shown in FIG. 2, the standby command SB and, correspondingly, also the command for switching back from the standby mode are initially transmitted from the system controller 2 to the controller 17 of the detector control unit 5, which then forwards this command to the switching control unit 7.As a rule, the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mneeds detector operating data DB intended for operation, which are stored in each case in one or more memories 47, 48 (see FIG. 3 ) of the individual individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 m. These include, inter alia, calibration data DB, on the basis of which different sensitivities of the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mare compensated, and configuration data for the individual detectors. These memories 47, 48 in the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mare usually volatile memories, i.e. the memory contents are lost when the supply voltage is switched off.In principle, this detector operating data for the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mare stored in the system controller 2. This means that when switching from stand-by mode to full mode again, the required detector operating data, in particular calibration data DB, could be transmitted from there via the detector control unit 5 to the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 m. This could be initiated by the switching control unit 7 or also synchronously with the standby command SB by the system controller 2 itself. However, in order to intervene as little as possible in the complex system of the system controller 2 in an implementation of the switching device according to the invention, the switching control unit 7 has a detector operating data management unit 8 with a separate memory 9 in the preferred exemplary embodiment illustrated in FIG. 2. The detector operating data management unit 8 and the memory 9, like the remaining components of the switching control unit 7, are also supplied with the necessary voltage in the standby mode, i.e. are not switched off.With the aid of the detector operating data management unit 8, it can be ensured that the detector operating data DB, in particular calibration data DB, from the memories 47, 48 of the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mare additionally stored in the memory 9. This can take place either once after a new calibration or a new specification of detector operating data DB to the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 m, but also automatically each time before switching to the standby mode is intended. After switching back from standby mode to full mode, the detector operating data DB can be retrieved from the memory 9 and written back into the memories 47, 48 of the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 m.Since, as can be understood, a certain amount of time is required for this storage of the calibration data DB and thus for the complete preparation of the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mfor one scan (in the case of a 64-channel detector, approximately 8 to 10 s), such a switching into standby mode is not always expedient in the case of shorter pauses, for example in the waiting times between two scans, if the patient is merely repositioned briefly. In order to save energy even in these short scan pauses (since these short pauses can naturally also add up to a very long total period of time over an operating day), there is the possibility here of automatically switching over to the first energy saving mode, the above-mentioned acquisition ready mode. In contrast to the standby mode, this switching takes place only within the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 m, for which reason reference is made once again to FIG. 3.For this purpose, the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mcomprise an interpreter unit 50, for example as part of the input / output interface 49. This interpreter unit 50 can interpret specific commands which the relevant individual detector 20 a, 20 b, 20 c, 20 d,..., 20 m receives from the system controller 2 via the detector control unit 5 and output a deactivation signal DS in order to deactivate specific components of the relevant individual detector 20 a, 20 b, 20 c, 20 d,..., 20 msuch that they no longer consume energy.In the exemplary embodiment illustrated in FIG. 3, this deactivation signal DS acts in particular for the operational amplifiers 41, the sample-and-hold elements 43, the multiplexer 44, the analog-to-digital converter 45 and the preprocessing unit 46, since these components require the most energy and can easily be switched off from power. In particular, the input / output interface 49 with the interpreter unit 50 and the memories 47, 48 with the calibration data DB and configuration data are not affected by the deactivation signal DS, since these should continue to operate unchanged and in particular the calibration data DB should also remain stored on site.The effect of the deactivation signal DS is only schematically shown here as a line to the individual components concerned. In fact, it is any signal for de-energizing the relevant components, for example, a power supply of the relevant components can be easily interrupted with this signal DS using one or more suitable switches.In the specific case, quite specific typical signals of the system control 2 are used to trigger the deactivation or activation of the components. On the one hand, this is the scan preload signal SP, which is emitted by the system controller 2 shortly before a scan, so that on the one hand the X-ray source and on the other hand the detector are prepared for a subsequent scan. This scan preload signal SP is output when the operator actuates the X-ray trigger at the user interface of the system controller 2. From the actuation of this X-ray trigger until the actual emission of X-ray radiation, approximately 1 to 2 s are required anyway. Therefore, in synchronism with the radiation triggering, approximately 1 to 2 s later (i.e. corresponding to the time required by the X-ray source to emit the X-ray radiation) the actual make data signal MD follows, which ensures that, from the receipt of this make data signal MD, the raw data are acquired at the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 m, i.e. the photodiodes 40 are read out as described. This make data signal MD is applied until no more data are to be read out. The deactivation of this make data signal MD can therefore be interpreted by the interpreter unit 50 in such a way that the deactivation signal DS is subsequently output in order to deactivate the components mentioned. Conversely, the scan preload signal SP can be used to switch on the current for the components again, i.e. to cancel the deactivation signal DS.The above-mentioned preferred procedure for switching to stand-by mode and back is once again illustrated with reference to the flow chart in FIG. 4.In step I, the detector control unit 5 or the switching control unit 7 receives a standby command SB from the standby activation interface 3 of the system controller 2 via the data channel D. Thereupon, in step II, the detector operating data management unit 8 of the switching control unit 7 first ensures that the detector operating data DB is read out from the individual memories of the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mand stored in the separate memory 9. Subsequently, the enable output 15 of the switching control unit 7 is switched over, i.e. an enable signal ES is output and thus the power supplies 6 a, 6 b,..., 6 nof the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mare deactivated via the enable inputs 13 and thus their voltage supply is interrupted (step III).In step IV, a wait is then made until a full mode activation signal is again sent to the detector control unit 5 or the switching control unit 7 via the standby activation interface 3. If such a full-mode switch-on signal is then received, in step V, the deactivation of the supply voltage outputs 12 of the power supplies 6 a, 6 b,..., 6 nof the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mis first canceled, i.e. the interruption of the voltage supply for the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mis canceled again. Subsequently, in step VI, the operation control data DB or calibration data DB are sent again to the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mwith the aid of the detector operation data management unit 8, so that the entire computed tomography system 1 is fully operational.The cancelling of the power supply interruption and the returning of the calibration data to the individual detectors 20 a, 20 b, 20 c, 20 d,..., 20 mtakes less than 10 s. This is considerably faster than the time required to establish full operational readiness (requiring about 5 min) when the computed tomography system is completely switched on again.In the exemplary embodiment illustrated here, a "full operational readiness" of the detector device 4 is understood to mean an operating state as represented in the last method step VII in FIG. 4, i.e. the detector device 4 is either in the acquisition readiness mode ABM in which the above-described components of the individual detectors 20 a, 20 b, 20 c, 20 d... remain. 20 m, or in the scan mode SM, in which all components are active and data can be acquired. The operating state of the detector device 4 is then automatically determined by signals from the system controller, for example the above-mentioned scan preload signal SP and the make data signal MD. If the detector device 4 is in the acquisition ready mode ABM, the user can switch back to the standby mode at any time by means of a standby command SB, which is represented in FIG. 4 by a loop to method step I.With the aid of the detector device modified according to the invention, it is therefore possible to drastically reduce the total energy requirement of the imaging system, in particular if the system is not used for imaging for a longer time, but rather only needs to maintain operational readiness. In this time, a reduction of the power consumption by 95% is entirely possible.Finally, it is pointed out once again that the control devices described in detail above are merely exemplary embodiments which can be modified in a wide variety of ways by the person skilled in the art without departing from the scope of the invention. In particular, it is also possible for the detector device to be constructed in such a way that only one of the above-described power saving modes can be switched on. Likewise, the use is not restricted to individual detectors which are constructed in the manner explained above in the exemplary embodiment, but rather the construction can also be completely different, for example with counting X-ray detectors which then naturally also have components adapted thereto for accepting and processing the data. What is only decisive is that in the manner according to the invention components which require a particularly large amount of energy can be deactivated in the individual detector when they are not used. Furthermore, the use of the indefinite article "a" or "an" does not exclude that the features in question can also be present multiple times. Likewise, it is not excluded that elements of the present invention represented as individual units consist of several interacting partial components, which may optionally also be spatially distributed.

Claims

Detector device (4) for a computed tomography system (1), which detector device (4) has a number of individual detectors (20a, 20b, 20c, 20d, 20m) and at least one detector control unit (5) with in each case a plurality of components and is designed such that it can be switched over into at least one power-saving mode in which at least some of the components of the individual detectors (20a, 20b, 20c, 20d, 20m) are deactivated and at the same time at least some of the components of the detector control unit (5) are not deactivated.Detector device according to Claim 1, wherein the detector device (4) is designed such that certain components of the detector control unit (5) which are not required in the power-saving mode are deactivated in the power-saving mode.Detector device according to claim 1 or 2, wherein the individual detectors (20a, 20b, 20c, 20d, 20m) each have a deactivation device for deactivating specific components of the respective individual detector (20a, 20b, 20c, 20d, 20m).Detector device according to one of the preceding claims, wherein the detector device (4) has a voltage supply arrangement (10) for the individual detectors (20a, 20b, 20c, 20d, 20m) and the detector control unit (5), and this voltage supply arrangement (10) has at least one switching device (7, 14) and is designed such that, in a first switching state of the switching device (7, 14), the voltage supply of the individual detectors (20a, 20b, 20c, 20d, 20m) is interrupted and the voltage supply for the detector control unit (5) is maintained further.Detector device according to claim 4, wherein the switching device (7, 14) is integrated into the detector control unit (5).Detector device according to one of Claims 4 or 5, wherein the switching device (7, 14) comprises at least one switching unit (14) and a switching control unit (7) for actuating the switching unit (14).Detector device according to claim 6, wherein the switching device (7, 14) is designed such that in the first switching state at least the voltage supply for the switching unit (14) and the switching control unit (7) is maintained.Detector device according to one of Claims 4 to 7, wherein the voltage supply arrangement (10) has at least one power supply unit (6a, 6b, 6n) having at least one supply voltage input (11), an integrated switching unit (14) and a supply voltage output (12), and a deactivation input (13) for inputting a deactivation signal (ES) for a supply voltage output (12) (enable input), which is connected to the switching control unit (7).Detector device according to one of Claims 4 to 8, having a detector operating data management unit (8) which is designed, after the voltage supply is switched on again, to transmit first detector operating data (DB), preferably calibration data (DB), to the individual detectors (20a, 20b, 20c, 20d, 20m).Detector device according to one of Claims 4 to 9, having a detector operating data management unit (8) which is designed, before the switching device (7, 14) is switched to the power-saving mode, to read out detector operating data (DB), preferably calibration data (DB), from the individual detectors (20a, 20b, 20c, 20d, 20m) and store it in a memory (9) assigned to the individual detectors (20a, 20b, 20c, 20d, 20m).Computed tomography system (1) having a detector device (4) according to one of the preceding claims.Method for operating a detector device (4) of a computed tomography system (1), wherein the detector device (4) has a number of individual detectors (20a, 20b, 20c, 20d, 20m) and at least one detector control unit (5), wherein after a switch to a power saving mode, at least some of the components of the individual detectors (20a, 20b, 20c, 20d, 20m) are deactivated and at the same time at least some of the components of the detector control unit (5) are not deactivated.Method according to Claim 12, wherein specific components of the relevant individual detector (20a, 20b, 20c, 20d, 20m) are deactivated in each case with the aid of a deactivation device of an individual detector (20a, 20b, 20c, 20d, 20m).Method according to Claim 12 or 13, wherein a voltage supply for the individual detectors (20a, 20b, 20c, 20d, 20m) is interrupted and a voltage supply for the detector control unit (5) is still maintained in the process.Method according to Claims 13 and 14, wherein a deactivation of specific components of an individual detector (20a, 20b, 20c, 20d, 20m) takes place automatically with the aid of the deactivation device of the individual detector (20a, 20b, 20c, 20d, 20m) when a data acquisition is ended, and a changeover to a standby mode in which a voltage supply of the individual detectors (20a, 20b, 20c, 20d, 20m) is interrupted is initiated by a command from a user interface.Method according to one of Claims 12 to 15, in which, before switching to the power-saving mode, in particular the standby mode, detector operating data (DB), preferably calibration data (DB), are read out by the individual detectors (20a, 20b, 20c, 20d, 20m) and are stored assigned to the individual detectors (20a, 20b, 20c, 20d, 20m), and, after switching back from the power-saving mode, in particular the standby mode, the detector operating data (DB) assigned to them in each case are sent back to the individual detectors (20a, 20b, 20c, 20d, 20m).

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