Voltage generator and X-ray imaging system

Abstract

The invention provides a voltage generator (1) for an X-ray imaging system (4), the voltage generator (1) comprising a trigger system (2) configured to trigger the voltage generator (1) to initiate a transition to a first value of an output voltage of the voltage generator (1) in response to receiving a start cycle trigger signal, and in response to determining that the output voltage passes the predetermined threshold, triggering initiation of data acquisition of the detector (6) for a first integration period of a data acquisition cycle of the detector (6).

Description

Technical Field

[0001] The present invention provides a voltage generator, an X-ray imaging system, a method, a computer program product and a computer readable medium. Background Art

[0002] X-ray imaging systems usually use kVp switching as an image acquisition mode, where kVp refers to the output voltage of a voltage generator, which provides operating power for the radiation source of the imaging system.

[0003] In this imaging mode, the output voltage kVp is rapidly alternated between low kVp and high kVp to acquire consecutive projections with different spectra (eg, different X-ray spectra).

[0004] For example, during an acquisition cycle of a detector of an imaging system, a voltage generator can switch or transition between two voltage values ​​(i.e., a high voltage and a low voltage). A cycle can include, for example, at least a high voltage period and a low voltage period. A trigger signal, such as from an angular encoder, can be used to initiate the rising and falling transitions of the output voltage.

[0005] The quality depends on having a well-defined and stable synchronization of the output spectrum of the radiation source with the data acquisition. Changes in the output spectrum (e.g., X-ray flux) will cause changes in the effective spectrum of the acquired data. Spectral processing, e.g. for material decomposition, depends on the spectrum and is very sensitive to differences between the assumed spectrum and the true spectrum, and therefore to changes in the spectrum.

[0006] US2014 / 0321603A1 describes an X-ray CT apparatus. The X-ray CT apparatus includes an image generation unit, a discrimination unit, a monochromatic X-ray image generation unit, a combined image generation unit, and a display unit. The image generation unit generates a plurality of reference material images corresponding to each of a plurality of reference materials based on multi-energy pre-reconstruction data obtained by scanning an object. The discrimination unit discriminates each of a plurality of materials contained in an imaging region of the object based on the plurality of reference material images.

[0007] However, the temporal behavior of the subsystems of the imaging system may lead to significant variations. This in turn may lead to artifacts in the data processing. As an example, there are system components that typically have uncertainty (also called jitter) in their temporal behavior.

[0008] As an example, a voltage generator may include a resonator and a transformer to generate a voltage, such as a high AC voltage. An energy injector may be provided, which is configured to inject energy into the resonator to increase the output voltage. When no energy is injected, the output voltage will therefore drop due to the output load of the X-ray tube. A current switch may be used for energy injection, and a change in the switch state may be allowed only during a zero crossing of the resonator. Thus, the generator may react to an external trigger signal only at discrete time points (e.g., zero crossings). Since the phase and frequency of the resonator are difficult to dynamically control and synchronize with a periodic trigger signal, inaccuracies in the time response, such as jitter, may occur. As an example, a generator with an average resonant frequency of 100 kHz may show J Gen = Random reaction time between 0 and 5 μs.

[0009] Therefore, existing systems face the adverse effects of uncertainty in temporal behavior. Summary of the invention

[0010] It is an object of the present invention to allow mitigating the adverse effects of uncertainties in the temporal behavior (eg jitter).

[0011] The invention provides a voltage generator, an X-ray imaging system, a method, a computer program product and a computer readable medium according to the independent claims. Preferred embodiments are laid out in the dependent claims.

[0012] The present invention provides a voltage generator for an X-ray imaging system, the voltage generator comprising a trigger system. The trigger system is configured to trigger the voltage generator to initiate a transition to a first value of an output voltage of the voltage generator in response to receiving a start cycle trigger signal. The trigger system is also configured to trigger the initiation of data acquisition of the detector for a first integration period of a data acquisition cycle of the detector in response to determining that the output voltage passes a predetermined threshold.

[0013] Therefore, the start cycle trigger signal can cause the start of the data acquisition cycle of the X-ray detector. At the same time, the data acquisition can be closely related to the actual output voltage of the voltage generator, specifically, the integration period can be more accurately synchronized with the voltage transition.

[0014] Thus, the trigger system as described above allows a well-defined synchronization of data acquisition with the output spectrum of the voltage generator and, respectively, of the radiation source powered by the voltage generator.

[0015] Note that data acquisition by, for example, a detector in an imaging system (e.g., a CT system) may be structured / divided into successive integration periods IP of the detector. For example, the incident X-ray flux reaching each detector pixel may be converted and integrated during one IP to form, for example, one acquisition data sample associated with one projection.

[0016] Transitions between high and low values ​​of the output voltage are particularly problematic in terms of contaminating the high and low frequency spectra with the intermediate spectrum. Therefore, using the present trigger system (which triggers acquisition based on output voltage values ​​passing a predetermined threshold during such transitions) allows mitigating the contamination effects of the intermediate spectrum.

[0017] Thus, the above challenges are overcome. Specifically, triggering data acquisition based on the actual output voltage allows for accounting for any delays during the ramp-up or ramp-down of the output voltage. For example, the rise and fall of a voltage signal can conventionally introduce timing uncertainties, which can be eliminated using the trigger system of the present disclosure.

[0018] Thus, the present disclosure may provide a triggering scheme to reduce the effects of jitter during kVp switching (e.g., spectral CT kVp switching), particularly when the detector integration also captures X-ray flux during kVp voltage transitions (i.e., transitions of the output voltage between a first value and a second value).

[0019] As an example, the triggering scheme may use a comparator that detects when the voltage during the voltage transition is above / below a threshold and triggers the detector integration in response. Thus, the triggering system may include a comparator. The triggering system may alternatively or additionally include a voltage detection system. As will be seen below, the present disclosure may also optionally provide a timer that is started during the voltage transition (e.g., during the transition to the high kVp phase). The end of the timer may trigger the next voltage transition, for example, a downward transition from the high kVp phase to the low kVp phase.

[0020] The voltage generator of the present disclosure is a voltage generator for providing operating power for an X-ray imaging system, in particular, for a radiation source of the X-ray imaging system. The voltage generator may be a high voltage generator. Note that the voltage generator is not limited to an element that generates an output voltage, but also includes one or more components that implement other functions (including but not limited to the function of triggering the system), such as software and / or hardware components.

[0021] The voltage generator may be configured to output power according to an output power (kVp) switching scheme.The voltage generator may be configured to transition, in particular, alternate, between two output voltage values, in particular, a first value and a second value.

[0022] According to the present disclosure, the first value may be a high voltage value and the second value may be a low voltage value, or vice versa. Thus, in particular, transitioning to the first value may include transitioning (eg, rising or falling) from the second value to the first value.

[0023] Specifically, the voltage generator may be configured to transition to a first value, maintain the output voltage at the first value, then transition to a second value and maintain the output voltage at the second value. This may be repeated.

[0024] According to the present disclosure, the transition is triggered in response to receiving a start-up cycle trigger signal.

[0025] According to the present disclosure, the start cycle trigger signal may be an angular trigger signal obtained, for example, from an angular encoder of, for example, the CT gantry position during rotation. This may, for example, ensure that the angular position of each projection is well defined and may simplify image reconstruction. Due to the variation in rotation speed, the cycles may have different lengths. As an alternative to using a start cycle trigger signal from an angular encoder, a periodic trigger signal may be used.

[0026] As can be seen above, the transition is triggered in response to receiving the start cycle trigger signal, and thus the data acquisition cycle, in particular its first integration period, can be triggered in response to the actual transition of the output voltage (more specifically, in response to the output voltage passing a predetermined threshold). Accordingly, the start cycle trigger signal can thus cause or indicate the start of the data acquisition cycle of the detector. At the same time, the integration period can be tightly coupled to the voltage transition.

[0027] It should be noted that due to coupling the integration period to the output voltage, a certain degree of decoupling from the start cycle trigger signal is introduced. In particular, this means that a correction can be provided that takes into account that the data acquisition is not precisely synchronized with the start cycle trigger signal. For example, when the start cycle trigger signal is an angular encoder trigger signal, the orientation associated with the integration period may have an offset, and a correction for this offset can be provided.

[0028] The correction can be achieved, for example, by detecting the time difference between the start cycle trigger signal (angle encoder trigger signal) and the trigger signal that triggers the start of data acquisition for the integration period. The time difference can be used to estimate the angle mismatch between the nominal angle of the encoder trigger signal and the real gantry angle at which the data acquisition is started. The estimated angle mismatch can be used for reconstruction to correct the angle jitter. Alternatively, the correction can be performed by means of an adaptive digital phase-locked loop A-DPLL, which models the rotation of the gantry to which the angle encoder is attached, for example. The A-DPLL trigger signal that can be used is explained in detail in European patent application EP21216352.1, which is incorporated herein by reference. The A-DPLL can be used to improve the angular accuracy of the trigger signal from the angle encoder. Within the A-DPLL, the gantry angle is estimated, and the actual value obtained at the acquisition trigger time can be used for image reconstruction to correct the angle jitter.

[0029] As briefly mentioned above, the triggering system according to the present disclosure may be configured to start a timer at predetermined time intervals in response to determining that the output voltage passes a predetermined threshold. That is, the timer may be started when the first integration period starts.

[0030] According to the present disclosure, the trigger system may also be configured to output a transition trigger signal in response to expiration of the timer, wherein the transition trigger signal is configured to trigger the voltage generator to initiate a transition from a first value of the output voltage to a second value. Specifically, the first value may be higher than the second value.

[0031] Using a timer as disclosed herein allows further reduction of jitter. Specifically, when the first value is a high voltage value, the jitter of the high voltage period can be effectively reduced by means of the timer. Then, any remaining integrated jitter (including, for example, cycle length jitter) will occur in and be substantially consumed by the low voltage period, which is less sensitive than the high voltage period.

[0032] According to the present disclosure, the threshold value may be a first threshold value, and the trigger system may be further configured to trigger the end of data collection for the first integration period after triggering the start of data collection for the first integration period and in response to determining that the output voltage passes through a predetermined second threshold value. Optionally, the trigger system may also be configured to trigger the start of data collection for a second integration period of the data collection cycle after triggering the start of data collection for the first integration period and in response to determining that the output voltage passes through a predetermined second threshold value.

[0033] Specifically, the second integration period may be started at the same time as the first integration period ends.

[0034] By using the second threshold, the second integration period can be reliably synchronized with the voltage transitions, thereby reducing adverse effects due to jitter.

[0035] The first threshold may be the same as the second threshold. Alternatively, the first threshold may be different from the second threshold. Each threshold may be selected based on the steepness of the corresponding transition and / or in order to minimize the deleterious effects of jitter.

[0036] Providing different thresholds may be advantageous, for example, because transitions may differ in steepness and / or because jitter may be more or less harmful during high voltage or low voltage periods.

[0037] According to the present disclosure, transitioning to the first value of the output voltage may include increasing the output voltage. In response to determining that the output voltage exceeds a threshold, specifically, exceeds a first threshold, triggering the start of data acquisition of the detector for a first integration period of the data acquisition cycle may be performed. Thus, the data acquisition cycle may be started at a high voltage period, and the first integration period may be associated with the high voltage period.

[0038] Alternatively or additionally, according to the present disclosure, transitioning from a first value of the output voltage to a second value / the second value may include reducing the output voltage. In response to determining that the output voltage drops below a predetermined second threshold / the predetermined second threshold, an end of data acquisition for a first integration period / the triggering of the end may be performed, and optionally, a start of data acquisition for a second integration period / the second integration period of the data acquisition cycle / the triggering of the start of data acquisition / the triggering of the start. Thus, the second integration period may be associated with a low voltage period.

[0039] The data acquisition cycle may include at least a first integration period and a second integration period and a high voltage period and a low voltage period associated therewith. The second integration period may follow the first integration period. Thus, the high voltage period and the low voltage period may follow each other. The data acquisition cycle may optionally include more than two integration periods.

[0040] Similar to determining the gantry angle at the start of the first data acquisition, the reconstructed gantry angle can be determined using the trigger signal of the second data acquisition. As described above, the time measurement or the modeled angle of the A-DPLL can be used to estimate the gantry angle of the second data acquisition. This correction will reduce the reconstructed angle jitter.

[0041] The voltage generator may be included in an imaging system (eg, an X-ray imaging system), and in particular, may be included in or connected to an X-ray source so as to provide operating power to the X-ray source.

[0042] The present invention also provides an X-ray imaging system, comprising a trigger system, wherein the trigger system is configured to trigger a voltage generator to initiate a transition to a first value of an output voltage of the voltage generator in response to receiving a start cycle trigger signal. The trigger system is further configured to trigger the initiation of data acquisition of the detector for a first integration period of a data acquisition cycle of the detector in response to determining that the output voltage passes a predetermined threshold.

[0043] The voltage generator may be part of or connected to an X-ray imaging system. The voltage generator may be a voltage generator configured to power an X-ray source of the X-ray imaging system, in particular, a voltage generator connected to or included in the X-ray source.

[0044] The advantages and features outlined above in the context of a voltage generator are analogously applicable to an X-ray imaging system.In particular, the trigger system may be any of the trigger systems described above.

[0045] The trigger system may be part of the voltage generator (as described above), or it may be separate from and in signal communication with the voltage generator.

[0046] The trigger system according to the present disclosure may also be configured to start a timer at a predetermined time interval in response to determining that the output voltage passes a predetermined threshold. Specifically, according to the present disclosure, the trigger system may also be configured to output a transition trigger signal in response to the timer expiring, wherein the transition trigger signal is configured to trigger the voltage generator to start a transition from a first value of the output voltage to a second value.

[0047] According to the present disclosure, the threshold value may be a first threshold value, and the trigger system may be further configured to trigger the end of data collection for the first integration period after triggering the start of data collection for the first integration period and in response to determining that the output voltage passes through a predetermined second threshold value. Optionally, the trigger system may also be configured to trigger the start of data collection for a second integration period of the data collection cycle after triggering the start of data collection for the first integration period and in response to determining that the output voltage passes through a predetermined second threshold value. The first threshold value may be the same as the second threshold value. Alternatively, the first threshold value may be different from the second threshold value.

[0048] According to the present disclosure, transitioning to the first value of the output voltage may include increasing the output voltage, and in response to determining that the output voltage exceeds a threshold, specifically, exceeds the first threshold, triggering the start of data acquisition of the detector for a first integration period of the data acquisition cycle may be performed.

[0049] Alternatively or additionally, according to the present disclosure, the transition from a first value of the output voltage to a second value / the second value may include reducing the output voltage, and in response to determining that the output voltage drops below a predetermined second threshold / the predetermined second threshold, the end of data acquisition for the first integration period / the triggering of the end may be performed, and optionally, the start of data acquisition for a second integration period / the second integration period for the data acquisition cycle / the triggering of the start of data acquisition / the triggering of the start may be performed.

[0050] The X-ray imaging system according to the present disclosure may comprise a voltage generator, in particular a voltage generator as described above or specified in the claims.As briefly mentioned above, the trigger system may be partially or completely comprised in the voltage generator, or may be external to the voltage generator.

[0051] Alternatively or additionally, an X-ray imaging system according to the present disclosure may include an X-ray source, in particular a voltage generator as described above or specified in the claims. The X-ray source may be configured such that the output voltage of the voltage generator provides operating power for the X-ray source.

[0052] Alternatively or additionally, an X-ray imaging system according to the present disclosure may include a detector, wherein the detector is configured to perform data acquisition. The detector may be any detector suitable for X-ray imaging. The detector may be configured to perform data acquisition according to a trigger signal provided by a trigger system.

[0053] Alternatively or additionally, the X-ray imaging system according to the present disclosure may include a voltage detection system configured to detect the output voltage. The voltage detection system may be configured to output the value of the output voltage to, for example, a comparator.

[0054] Alternatively or additionally, the X-ray imaging system according to the present disclosure may include a comparator, the comparator being configured to detect that the output voltage passes through a predetermined threshold, specifically, a first threshold and / or a second threshold, and in response thereto, trigger the detector to start data acquisition for an integration period, specifically, for the first integration period and / or for the second integration period, and optionally trigger a timer / the timer. For example, the comparator may receive the value of the output voltage from the voltage detection system.

[0055] The present invention also provides a method for operating a voltage generator for an X-ray imaging system and / or an X-ray imaging system, in particular a voltage generator and / or an X-ray imaging system as described above or specified in the claims. The method includes triggering the voltage generator to initiate a transition to a first value of an output voltage of the voltage generator in response to receiving a start cycle trigger signal. The method also includes triggering the initiation of data acquisition of the detector for a first integration period of a data acquisition cycle of the detector in response to determining that the output voltage passes a predetermined threshold.

[0056] This determination may be performed using a voltage detection system that detects the output voltage and / or a comparator that detects that the output voltage has crossed a predetermined threshold.

[0057] The method of the present disclosure may include starting a timer at predetermined time intervals in response to determining that the output voltage passes through a predetermined threshold.

[0058] Specifically, the method of the present disclosure may include: in response to expiration of a timer, outputting a transition trigger signal, wherein the transition trigger signal is configured to trigger a voltage generator to initiate a transition from a first value to a second value of an output voltage.

[0059] The threshold may be a first threshold, and the method may further include, after triggering initiation of data collection for the first integration period and in response to determining that the output voltage passes a predetermined second threshold, triggering an end of data collection for the first integration period, and optionally, triggering initiation of data collection for a second integration period of the data collection cycle. The first threshold may be the same as or different from the second threshold.

[0060] Transitioning to the first value of the output voltage may include increasing the output voltage, and wherein triggering initiation of data acquisition of the detector for a first integration period of the data acquisition cycle may be performed in response to determining that the output voltage exceeds a threshold, in particular the first threshold.

[0061] Alternatively or additionally, the transition from a first value of the output voltage to a second value / the second value may comprise reducing the output voltage, wherein, in particular, in response to determining that the output voltage drops below a predetermined second threshold value / the predetermined second threshold value, an end of data acquisition for a first integration period / the triggering of the end may be performed, and optionally, a start of data acquisition for a second integration period / the second integration period for a data acquisition cycle / the triggering of the start of data acquisition may be performed.

[0062] The present invention also provides a computer program product comprising instructions, which, when the program is executed by a computer, cause the computer to perform one or more method steps described in the present disclosure.

[0063] The present invention also provides a computer-readable medium comprising instructions, which, when executed by a computer, cause the computer to perform one or more method steps described in the present disclosure.

[0064] The features and advantages outlined in the context of the voltage generator similarly apply to the X-ray imaging system, method, computer program product, and computer readable medium of the present disclosure.

[0065] Other features, examples and advantages will become apparent from the detailed description taken with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 shows a schematic and not to scale illustration of a voltage generator according to the present disclosure;

[0067] Figure 2 shows a schematic and not to scale illustration of an X-ray imaging system according to the present disclosure;

[0068] Figure 3 A flow chart showing a method according to the present disclosure; and

[0069] Figure 4 A timing diagram according to the present disclosure is shown.

[0070] List of reference numerals:

[0071] Voltage generator 1

[0072] Trigger System 2

[0073] Data processing system 3

[0074] X-ray imaging system 4

[0075] X-ray source 5

[0076] Detector 6

[0077] Voltage detection system7

[0078] Comparator 8

[0079] Angle encoder 9

[0080] Steps S11 to S17

[0081] Arrow 21-28 DETAILED DESCRIPTION

[0082] Figure 1A schematic and not to scale illustration of a voltage generator 1, in particular a high voltage HV generator, according to the present disclosure is shown. It comprises a trigger system 2, which is configured to trigger the voltage generator to initiate a transition to a first value of the output voltage of the voltage generator in response to receiving a start cycle trigger signal. The trigger system is further configured to trigger the initiation of data acquisition of the detector for a first integration period of the data acquisition cycle in response to determining that the output voltage passes a predetermined threshold. Thus, the start cycle trigger signal may cause the initiation of a data acquisition cycle of the detector.

[0083] The triggering system may be implemented at least in part using a data processing system 3, for example comprising one or more computing devices. In particular, any determining steps may be performed by the data processing system and / or one or more triggering steps may be performed by the data processing system.

[0084] The voltage generator, in particular the trigger system, can be configured to perform any method according to the present disclosure, in particular as follows Figure 3 For example, it can be configured as follows Figure 4 The trigger system, in particular the entire voltage generator, may be included in or connected to any X-ray imaging system according to the present disclosure, in particular as Figure 2 Specifically, the voltage generator may be included in the X-ray source of the X-ray imaging system according to the present disclosure or may be connected to the X-ray source of the X-ray imaging system according to the present disclosure.

[0085] Figure 2 A schematic and not to scale illustration of an X-ray imaging system 4 according to the present disclosure is shown. The X-ray imaging system comprises a voltage generator 1. The X-ray imaging system comprises a triggering system 2 according to the present disclosure, for example Figure 1 The trigger system may be external to the voltage generator as shown in this example, or it may be, for example, Figure 1 A portion of a voltage generator is shown.

[0086] Figure 2 The X-ray imaging system 4 shown also includes an X-ray source 5, and the X-ray source and the voltage generator 1 are configured such that the voltage generator 1 provides operating power to the X-ray source 5. Figure 2 In FIG. 5 , the voltage generator 1 is shown as being separate from the X-ray source 5 , but the voltage generator 1 may alternatively be incorporated into the X-ray source 5 .

[0087] exist Figure 2 In the embodiment, the X-ray imaging system 4 further comprises a detector 6 which is configured to perform data acquisition for X-ray imaging directed by the trigger system 2 .

[0088] Figure 2 The illustrated X-ray imaging system 4 also includes an optional voltage detection system 7, which is configured to detect the output voltage. For example, this can allow the trigger system to determine whether the output voltage passes a predetermined threshold. To this end, the voltage detected by the voltage detection system can be compared with the threshold.

[0089] Figure 2 The illustrated X-ray imaging system further comprises an optional comparator 8 configured to detect that the output voltage passes a predetermined threshold and, in response thereto, trigger the detector to initiate data acquisition for an integration period. The comparator 8 may be part of the trigger system 2.

[0090] The comparator 8 may be implemented entirely in hardware or entirely in software or a combination of hardware and software. The comparator 8 may be configured so that it detects that the output voltage passes through a first threshold and so that it detects that the output voltage passes through a second threshold different from the first threshold. Alternatively, two comparators may be provided, one for each of the first and second thresholds.

[0091] The comparator 8 may be configured such that it determines whether the output voltage exceeds or falls below one or more threshold values.

[0092] Optionally, the comparator 8 may be configured to also trigger a timer in response to determining that the output voltage passes a threshold or one or more thresholds.

[0093] The X-ray imaging system 4 may further include an optional angle encoder 9, which may output an angle trigger signal used as a start cycle trigger signal.

[0094] Figure 3 A flow chart of a method of operating a voltage generator for an X-ray imaging system according to the present disclosure and / or operating an X-ray imaging system according to the present disclosure is shown. For example, the voltage generator or the X-ray imaging system may be as described above. Figure 1 or Figure 2 The method may be implemented, for example, as follows: Figure 4 The timing diagram is shown.

[0095] In step S11, a start cycle trigger signal is received, for example by a trigger system. For example, the start cycle trigger signal may be an angle trigger signal received from an angle encoder. The start cycle trigger signal triggers the voltage generator to initiate a transition to a first value of the output voltage of the voltage generator. For example, the voltage generator may be triggered to initiate an increase in the output voltage to a high value kVp H .

[0096] In step S12, it is determined, for example, by a comparator, that the output voltage passes a (first) predetermined threshold. To this end, the output voltage may be detected by a voltage detection system, and the detected voltage may be input into the comparator. For example, it may be determined that the output voltage exceeds a (first) predetermined threshold.

[0097] In step S13, in response to determining that the output voltage passes through a (first) predetermined threshold, data acquisition of the detector for a first integration period of the data acquisition cycle is initiated. To this end, for example, the comparator may output a trigger signal when the detected voltage passes through a predetermined threshold.

[0098] In optional step S14, a timer is started when the output voltage passes a predetermined (first) threshold.

[0099] In optional step S15, the transition trigger signal triggers the voltage generator to initiate a transition from the first value to the second value of the output voltage, e.g., in response to expiration of a timer or some other triggering event. For example, the voltage generator may be triggered to initiate a reduction in the output voltage to a low value kVp L .

[0100] In optional step S16, it is determined, for example by a comparator, that the output voltage passes a (second) predetermined threshold value, which may be the same as or different from the (first) threshold value of step S12. To this end, the output voltage may be detected by a voltage detection system, and the detected voltage may be input into the comparator. For example, it may be determined that the output voltage drops below the (second) predetermined threshold value.

[0101] In optional step S17, in response to determining in step S16 that the output voltage passes through the (second) predetermined threshold, data acquisition of the detector for the second integration period of the data acquisition cycle is initiated. To this end, for example, when the detected voltage passes through the (second) predetermined threshold, the comparator can output a trigger signal.

[0102] Optionally, steps S12 and S13 and optionally one or more of steps S14 to S17 may be repeated one or more times.

[0103] The method may return to step S11, which marks the start of another data collection cycle, and some or all of the above steps may be repeated for the data collection cycle. For example, the method may return to step S11 after step S17, i.e. after at least the second integration period has been started, such as Figure 3 shown.

[0104] Figure 4 An exemplary timing diagram representing the method of the present disclosure is shown.

[0105] A start cycle trigger signal, such as an angular trigger signal provided based on an angular encoder signal, triggers the voltage source to start increasing the output voltage (arrow 21). This causes (arrow 22) the output voltage kVp to increase, specifically, to transition to (and maintain) a high output voltage. The value of the output voltage is input to a comparator (arrow 23). The comparator detects that the output voltage exceeds a threshold value, and in response, triggers the start of data acquisition by the detector for a first integration period (arrow 24) and optionally triggers the start of a timer (arrow 25). In response to the expiration of the timer (or some other triggering event), the voltage generator is triggered to reduce the output voltage (arrow 26), which causes the output voltage to decrease (arrow 27). The comparator detects that the output voltage drops below a threshold value, and in response, triggers the start of data acquisition by the detector for a second integration period (arrow 28). In this example, the first integration period is labeled "ACQ high" because it is performed when the output voltage is high, and the second acquisition period is labeled "ACQ low" because the output voltage is low. In a next step, for example triggered by a second start cycle trigger signal, the start of another first acquisition period can be triggered, for example in the above-described manner. This can also end the previous second acquisition period. Therefore, the first and second acquisition periods can together form an acquisition cycle.

[0106] However, variations from this triggering scheme are possible. For example, a cycle may include more than just two acquisition periods. Furthermore, a cycle may be initiated at a decrease in the output signal and thus with a low voltage acquisition period "ACQ low". Furthermore, alternative triggering events (i.e., other than a timer triggered by a comparator) may be used to end the first acquisition period and initiate the second acquisition period.

[0107] As already explained above in other contexts, the threshold that needs to be crossed (e.g., exceeded) by the output voltage to trigger the initiation of data collection for a first integration period may be different from the threshold that needs to be crossed by the output voltage to cease data collection for the first integration period and / or trigger the initiation of data collection for a second integration period.

[0108] Although the present invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered as exemplary rather than restrictive. The present invention is not limited to the disclosed embodiments. In view of the foregoing description and drawings, it will be apparent to those skilled in the art that various modifications may be made within the scope of the invention defined by the claims. In the claims, any reference numerals placed between brackets shall not be interpreted as limiting the claims. The word "comprising" does not exclude the presence of elements or steps other than those listed in the claims. The word "one" or "an" before an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by means of hardware comprising several different elements and / or by means of a suitably programmed processor or computer (such as a data processing system 3). In a device claim that lists several devices, several of these devices may be embodied by the same hardware item. For example, the X-ray imaging system claim lists a voltage generator 1 and an X-ray source 5, and in one embodiment, the voltage generator 1 may be incorporated into the X-ray source 5. Measures recorded in mutually different dependent claims may be advantageously used in combination.

Claims

1. A voltage generator (1) for providing operating power to an X-ray source (5) of an X-ray imaging system (4), the voltage generator (1) comprising a trigger system (2), the trigger system being configured to: In response to receiving a start cycle trigger signal, triggering the voltage generator (1) to start a transition to a first value of the output voltage of the voltage generator (1); and In response to determining that the output voltage passes through a predetermined threshold, initiation of data acquisition of the detector (6) for a first integration period of a data acquisition cycle of the detector (6) of the X-ray imaging system (4) is triggered.

2. The voltage generator (1) according to claim 1, the trigger system (2) being further configured to start a timer at predetermined time intervals in response to determining that the output voltage passes the predetermined threshold.

3. The voltage generator (1) according to claim 2, the trigger system (2) is also configured to output a transition trigger signal in response to expiration of the timer, and the transition trigger signal is configured to trigger the voltage generator (1) to start the transition from the first value to the second value of the output voltage.

4. Voltage generator (1) according to any one of the preceding claims, wherein: The threshold is a first threshold, and the trigger system (2) is further configured to: after triggering the start of data acquisition for the first integration period, in response to determining that the output voltage passes a predetermined second threshold, trigger the end of the data acquisition for the first integration period, and optionally trigger the start of data acquisition for a second integration period of the data acquisition cycle, specifically, wherein the first threshold is different from the second threshold.

5. Voltage generator (1) according to any one of the preceding claims, in, the transition to the first value of the output voltage comprises increasing the output voltage, and wherein, in response to determining that the output voltage exceeds the threshold, in particular exceeds the first threshold, the triggering of the start of the data acquisition of the detector (6) for the first integration period of the data acquisition cycle is performed, and / or wherein the transition from the first value of the output voltage to the second value / the second value comprises reducing the output voltage, specifically wherein, in response to determining that the output voltage drops below a predetermined second threshold value / the predetermined second threshold value, the end of the data acquisition for the first integration period / the triggering of the end is performed, and optionally, the start of data acquisition / the triggering of the start of data acquisition for a second integration period / the second integration period of the data acquisition cycle is performed.

6. An X-ray imaging system (4), comprising: The voltage generator (1) according to any one of claims 1 to 5, X-ray source (5), Detector (6), Wherein, the trigger system comprises: a voltage detection system (7), which is configured to detect the output voltage, and / or A comparator (8) is configured to detect that the output voltage passes through the predetermined threshold, specifically, the first threshold and / or the second threshold, and in response thereto, trigger the detector (6) to start data acquisition for an integration period, specifically, for the first integration period and / or the second integration period, and optionally trigger a timer / the timer.

7. A method for operating a voltage generator (1) for providing operating power for an X-ray source of an X-ray imaging system (4), in particular a voltage generator (1) according to any one of claims 1 to 5, and / or a method for operating an X-ray imaging system (4), in particular an X-ray imaging system (4) according to claim 6, the method comprising: In response to receiving a start cycle trigger signal, triggering the voltage generator (1) to start a transition to a first value of the output voltage of the voltage generator (1); as well as In response to determining that the output voltage passes through a predetermined threshold, triggering the start of data acquisition of the detector (6) for a first integration period of a data acquisition cycle of the detector (6) of the X-ray imaging system (4), Specifically, the determination is performed using a voltage detection system (7) for detecting the output voltage and / or a comparator (8) for detecting that the output voltage passes through the predetermined threshold.

8. The method according to claim 7, further comprising: In response to determining that the output voltage crosses the predetermined threshold, a timer is initiated at predetermined time intervals.

9. The method according to claim 8, further comprising: In response to the timer expiring, a transition trigger signal is output, wherein the transition trigger signal is configured to trigger the voltage generator (1) to initiate a transition from the first value to a second value of the output voltage.

10. The method according to any one of claims 7 to 9, wherein: The threshold is a first threshold, and the method further includes: after triggering the start of data collection for the first integration period, in response to determining that the output voltage passes a predetermined second threshold, triggering the end of the data collection for the first integration period, and optionally, triggering the start of data collection for a second integration period of the data collection cycle, specifically, wherein the first threshold is different from the second threshold.

11. The method according to any one of claims 7 to 10, in, the transition to the first value of the output voltage comprises increasing the output voltage, and wherein, in response to determining that the output voltage exceeds the threshold, in particular exceeds the first threshold, the triggering of the start of the data acquisition of the detector (6) for the first integration period of the data acquisition cycle is performed, and / or wherein the transition from the first value of the output voltage to the second value / the second value comprises reducing the output voltage, specifically wherein, in response to determining that the output voltage drops below a predetermined second threshold value / the predetermined second threshold value, the end of the data acquisition for the first integration period / the triggering of the end is performed, and optionally, the start of data acquisition / the triggering of the start of data acquisition for a second integration period / the second integration period of the data acquisition cycle is performed.

12. A computer program product comprising instructions which, when said program is run by a computer, cause said computer to perform the method according to any one of claims 7 to 11.

13. A computer readable medium comprising a computer program product according to claim 12.

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