EP4706344A1 - Cooling for x-ray system having at least two x-ray sources - Google Patents

Abstract

The invention relates to a cooling system (100) for an X-ray system (102) having at least two X-ray sources. The cooling system comprises a cooling unit (120) configured to provide a total flow (230) of cooling medium for cooling the X-ray source (110) and a further X-ray source (210); a flow divider (220) configured to divide the total flow (230) of cooling medium between a partial flow (231) towards the X-ray source (110) and a further partial flow (232) towards the further X-ray source (210); and a controller (150) for controlling the cooling unit (120). The controller is configured to receive a stand-by trigger signal, and in response to the stand-by trigger signal, control the cooling system (100) to adapt the partial flow (231) to provide a stand-by cooling flow towards the X-ray source (110) at a stand-by flow rate; and to receive an application trigger signal, and in response to the application trigger signal, control the cooling system (100) to adapt the partial flow (231) to provide an application cooling flow towards the X-ray source (110) at an application flow rate. The application flow rate of the application cooling flow is larger than a the stand-by flow rate of the stand-by cooling flow. The invention also relates to an X-ray system comprising the cooling system, a method for cooling an X-ray source of an X-ray system, a computer program element, and a computer-readable medium.

Description

COOLING FOR X-RAY SYSTEM HAVING AT LEAST TWO X-RAY SOURCES

FIELD OF THE INVENTION

The invention relates to a cooling system for an X-ray system having at least two X-ray sources, an X-ray system comprising the cooling system, a cooling method for the X-ray system, a computer program element, and a computer-readable medium.

BACKGROUND OF THE INVENTION

JP2009043652A describes a cooler that cools an X-ray tube by circulating a coolant. The cooler includes a pump circulating the coolant, a heat exchanger discharging heat of the coolant to the outside, and a flow rate control mechanism controlling the circulation flow rate of the coolant in process of operation of the X-ray tube.

JPH03171541 A discloses a cooling method and device of target for an X-ray generator. While a power is supplied to a filament to emit electrons, the power is detected with a power detector, and the result is sent to a control device as power signals. Based on the signals, the control device controls the operation of a throttle device in a flow path so as that the diameter of a water pipe is widened or narrowed depending upon that the supplied power is large or small respectively.

A main task related to X-ray generation in medical and other imaging applications is heat management. Only a small fraction of electrical energy applied to an X-ray source, such as an X-ray tube used in combination with a high voltage generator, is converted into useful radiation. Most of the electric power is converted into thermal energy. Therefore, for practical implementations of X-ray systems, a cooling unit is typically connected to the X-ray source. Generally, the cooling unit is either directly attached to the X-ray source, such as to an X-ray tube housing, or located in a separate control room and connected to the X-ray source via oil or water hoses. With respect to X-ray sources and the imaging system in which they are used, cooling units can be a major cost driver as well as a main contributor to overall failure rates. The cooling unit typically includes a pump for pumping cooling liquid, which significantly adds to the overall energy consumption and noise level of the imaging system. Such pumps may also be prone to failure. In the case of bi-plane systems with two X-ray sources, like some X-ray systems for interventional imaging, the cooling unit for each X-ray source may contribute significantly to costs, energy consumption and noise.

Hence, there is a need to improve cooling of X-ray sources for X-ray systems. SUMMARY OF THE INVENTION

It is, inter alia, an object of the invention to provide improved cooling of an X-ray system having at least two X-ray sources.

The invention is defined by the independent claims. Advantageous embodiments are defined in the dependent claims.

According to a first aspect of the invention, there is provided a cooling system for an X- ray system. The cooling system comprises: a cooling unit configured to provide a total flow of cooling medium for cooling an X-ray source and a further X-ray source; a flow divider configured to divide the total flow of cooling medium between a partial flow towards the X-ray source and a further partial flow towards the further X-ray source; and a controller for controlling the cooling unit, wherein the controller is configured to: receive a stand-by trigger signal, and in response to the stand-by trigger signal, control the cooling system to adapt the partial flow to provide a stand-by cooling flow towards the X-ray source at a stand-by flow rate; and receive an application trigger signal, and in response to the application trigger signal, control the cooling system to adapt the partial flow to provide an application cooling flow towards the X- ray source at an application flow rate, wherein the application flow rate of the application cooling flow is larger than the standby flow rate of the stand-by cooling flow.

The cooling unit is configured to provide a total flow of cooling medium for cooling the X-ray source and a further X-ray source. The cooling system comprises a flow divider configured to divide the total flow of cooling medium between a partial flow towards the X-ray source and a further partial flow towards the further X-ray source. The partial flow is adapted to be at the stand-by cooling flow rate in response to the stand-by trigger signal, and the partial flow is adapted to be at the application cooling flow rate in response to the application trigger signal.

The system can thus be used for cooling at least two X-ray sources. Such as for cooling of a bi-plane X-ray imaging system with two X-ray sources. In this way, a single cooling unit may provide cooling medium to both X-ray sources, which leads to a reduction in cost, size, energy consumption etc. The partial flow depends on the total flow as well as the flow division of the flow divider. The partial flow may be controlled by the controller, in response to either of the trigger signals, by controlling the cooling unit to adapt the total flow.

The stand-by cooling flow is sufficient to cool components of the X-ray source when the X-ray source is in a stand-by mode, such as before or in between X-ray applications like X-ray imaging applications. The application cooling flow is sufficient to cool components of the X-ray source during a selected application of the X-ray source, such as during imaging with an X-ray imaging system. In this way, the cooling flow of cooling medium to the X-ray source may be kept at a low level when the X-ray source is in stand-by mode, while providing sufficiently increased cooling when needed. This allows for reduced energy consumption and noise of the cooling unit and may extend the life-time of the system and/or its components such as the pump. The cooling system may thus dynamically provide the necessary cooling to the X-ray source, without wasting unnecessary energy. The stand-by cooling flow is preferably kept at a minimum level, high enough to account for energy inputs which are independent of an X-ray source application.

The stand-by flow rate may be predetermined, e.g. stored in a memory accessible to the controller, and/or may be determined or adapted based on the stand-by trigger signal. To ensure that after an X-ray application, the cooling is not reduced too quickly to the stand-by cooling flow rate, the controller may, in response to the stand-by trigger signal, provide for a gradual and/or delayed reduction from the application flow rate to the stand-by flow rate.

Data that is stored in, or provided to, the controller may comprise information pertaining to the X-ray source, such as X-ray tube age, usage history, as well as limits and specifications regarding parameters like temperature, current, voltage, anode rotation frequency etc.

The cooling unit may be directly attached to the X-ray source or may be located at a distance from the X-ray source. The cooling unit may comprise a conduit configured to be connected to the X-ray source. The flow of cooling medium may then be provided to the X-ray source via the conduit. The cooling unit may preferably comprise a pump for pumping cooling medium. The cooling flow rate may then be controlled by the controller via electrical input parameters to the cooling unit pump.

The controller is preferably connected (wired or wireless) to the X-ray system, such as to an X-ray system controller, a high voltage generator and/or to the X-ray source. This allows for data exchange between (components of) the imaging system and the controller.

The cooling system may comprise sensors connected to the controller, such as temperature sensors. The cooling system may, alternatively or additionally, be connected to the output of sensors external to the cooling system, such as sensors of the X-ray system or its components.

The controller may comprise a data processor for providing data processing functions.

The data processor may be a suitable computer, such as an electronic control module etc., which may also be a distributed computer system. The data processor or the computer, respectively, may comprise one or more of a processor, a memory, a data interface, a field-programmable gate array (FPGA), an applicationspecific integrated circuit (ASIC), or the like. The controller may be software-controlled by instructions in the memory. A computer program element comprising these instructions may be made available for downloading from a server (e.g. via the internet) or stored on a (non-transitory) medium. The cooling system may comprise a user interface, such that a user may interact with the controller.

According to an embodiment, the flow divider is configured to provide an adaptable division of the total flow of cooling medium, and the controller is configured to control the cooling unit to adapt the total flow of cooling medium, and/or to control the flow divider to adapt the division of the total flow of cooling medium.

Preferably, both the flow divider and the total flow of cooling medium can be individually controlled via the controller, and preferably the respective trigger signals comprise information relating to both X-ray sources and/or for which X-ray source the status is changing (from stand-by to application or the other way around). In this way, when both X-ray sources are in stand-by mode, a low cooling flow rate may be provided to both X-ray sources. When one of the X-ray sources is used for an application and the other is in stand-by mode, the flow divider can be controlled such that the higher application cooling flow is only provided where needed and the X-ray tube in stand-by still receives the (minimal) stand-by flow of cooling medium. In this way, significant energy, noise and cost reductions may be achieved as compared to a prior art bi-plane system with multiple cooling units each running with a constant high flow rate.

According to an embodiment, the application trigger signal comprises data regarding an X-ray application, and the controller is configured to adapt the application flow rate based on the X-ray application.

In this way, based on the data regarding the X-ray application, the cooling unit may provide an application cooling flow that is tailored to the circumstances, such as an X-ray imaging application at hand. Excessive or insufficient cooling of the X-ray source can be reduced or avoided.

According to an embodiment, the above-mentioned data regarding the X-ray application comprises at least one of an X-ray source voltage, an X-ray source current, an application power level, a number of X-ray imaging frames, an exposure time, an anode rotation frequency, and an imaging system gantry rotation frequency.

According to an embodiment, the application trigger signal comprises data regarding an X-ray source temperature, and the controller is configured to adapt the application flow rate based on the X-ray source temperature.

The cooling system may in this way, via the cooling unit, provide an application cooling flow that is tailored to the circumstances by taking the X-ray source temperature into account. Excessive or insufficient cooling of the X-ray source can be reduced or avoided. The data regarding the X-ray source temperature may comprise a distinct temperature value or temperature range for one or more locations at the X-ray source. The data regarding an X-ray source temperature may include data from temperature sensors, such as a currently detected temperature value or an (integrated) temperature value acquired over a certain time period. The data may include simulated and/or predicted values, such as provided from an X-ray source temperature computer model.

According to an embodiment, the application trigger signal comprises temporal data regarding a planned X-ray application, and the controller is configured to adapt the application flow rate and/or a timing of the application cooling flow based on the application trigger signal. With information about e.g. when a planned X-ray application is about to take place or is planned to change or end, the controller may timely adapt the application cooling flow, such as to timely ramp up or down the flow of cooling medium, provide advanced or delayed timing to switch to a determined flow of cooling medium etc. In this way, proactive adaptation of the cooling flow can be achieved and e.g. temperature peaks can be avoided. This may improve cooling efficiency and positively impact the lifetime of system components.

According to an embodiment, the controller is configured to determine a temporal behavior of cooling and/or heating of components of the X-ray source, and the controller is configured to adapt the application cooling flow and/or the stand-by cooling flow based on the determined temporal behavior.

The flow of cooling medium may not reach and cool each component of the X-ray source at the same moment. There may be a temporal difference between different components with respect to temperature increase as a result of applied power at the X-ray source, the time it takes for cooling medium in a flow from the cooling unit to arrive at the respective component, the time needed for cooling of the respective component by the cooling medium, etc. In this way, by determining and adapting to such behavior, the cooling of components of the X-ray source may be improved. A computer model, such as a digital twin, may be used to model the cooling behavior of the X-ray source components.

Examples of X-ray source components include an X-ray source frame, a window, parts of a rotational system such as a bearing axis, an anode etc. With the determined temporal behavior, the controller can adapt the cooling flow rate as well as the timing of the cooling flow to reduce the risk of any components being overheated, while also avoiding unnecessary cooling. Hence, increased efficiency of cooling may be provided. This may be particularly advantageous in combination with control of cooling based on information about future planned imaging applications.

E.g. with combined complex data sets, such as from one or several of the computer models mentioned above, artificial intelligence models like neural networks may advantageously be applied by the controller to regulate the cooling flows.

According to an embodiment, the cooling unit is configured to provide a total flow of cooling medium for cooling the X-ray source and a further X-ray source. The cooling system comprises a flow divider configured to divide the total flow of cooling medium between a partial flow towards the X- ray source and a further partial flow towards the further X-ray source. The partial flow is adapted to be at the stand-by cooling flow rate in response to the stand-by trigger signal, and the partial flow is adapted to be at the application cooling flow rate in response to the application trigger signal.

According to a second aspect of the invention, there is provided an X-ray system comprising an X-ray source, a further X-ray source, and the cooling system according to any embodiment of the first aspect of the invention.

The X-ray system may be e.g. a medical imaging system or an X-ray system for other purposes, such as scanning luggage. The X-ray system has at least two X-ray sources, such as a bi-plane X-ray system. Examples of X-ray systems include a computed tomography system, a radiography system, a fluoroscopy system, a C-arm X-ray system for interventional guidance etc.

According to a third aspect of the invention, there is provided a cooling method for an X- ray system, the method comprising: controlling a cooling unit to provide a total flow of cooling medium for cooling an X-ray source and a further X-ray source; controlling a flow divider to divide the total flow of cooling medium between a partial flow towards the X-ray source and a further partial flow towards the further X-ray source; receiving a stand-by trigger signal; in response to the stand-by trigger signal, controlling the cooling unit and/or the flow divider to adapt the partial flow to provide a stand-by cooling flow at a stand-by flow rate to the X-ray source; receiving an application trigger signal; and in response to the application trigger signal, controlling the cooling unit and/or the flow divider to adapt the partial flow to provide an application cooling flow at an application flow rate to the X-ray source, wherein the application flow rate of the application cooling flow is larger than the standby flow rate of the stand-by cooling flow.

According to an embodiment, the application trigger signal comprises data regarding an imaging application, and the method comprises adapting the application flow rate based on the X-ray application.

According to an embodiment, the application trigger signal comprises data regarding an X-ray source temperature, and the method comprises adapting the application flow rate based on the X- ray source temperature.

According to a fourth aspect of the invention, there is provided a computer program element, which, when being executed by a controller of a cooling system for an X-ray system, is adapted to cause the controller to perform the method according to the third aspect of the invention or any embodiments thereof.

According to a fifth aspect of the invention, there is provided a computer-readable medium having stored thereon the computer program element mentioned above.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 schematically illustrates a cooling system for cooling an X-ray system having an

X-ray source. Fig. 2 schematically illustrates a cooling system for cooling an X-ray system having two X-ray sources according to embodiments of the invention.

Fig. 3 schematically illustrates a method for cooling an X-ray source of an X-ray system.

Fig. 4 schematically illustrates a method for cooling at least two X-ray sources of an imaging system according to embodiments of the invention.

Fig. 5 schematically illustrates an example of dynamics between X-ray source power, X- ray source temperature and cooling medium flow rate.

DETAILED DESCRIPTION OF EMBODIMENTS

An example of an improved cooling system 100 in combination with an X-ray system

102 is schematically illustrated in Fig. 1. The X-ray system 102 at the left side of the figure comprises an X-ray source 110. The X-ray source 110 may be an X-ray tube or may be an assembly comprising an X- ray tube, high voltage generator etc. The imaging system 102 may include an imaging system controller 180. The imaging system controller 180 may physically be part of the imaging system 102, e.g. in a gantry of a computed tomography system, or may be partly or completely remote from the imaging system 102, such as in a workstation connected to the imaging system 102. The imaging system 102 may include or be connected to a sensor 170. The sensor 170 may measure at least one of a temperature, a rotation frequency, a voltage, a current, a magnetic field etc.

The cooling system 100 comprises a controller 150. The controller 150 may include a data processor 160. The controller 150 is connected to a cooling unit 120. The cooling unit is configured to provide a flow 130 of cooling medium towards the X-ray source 110 for cooling the X-ray source, and may include a pump to generate flows. The cooling medium may be water, oil or any other suitable cooling medium. The cooling medium may be a liquid or a gas.

The cooling unit 100 or parts thereof may be directly attached to the X-ray source or located separately, such as in proximity to the imaging system or in a separate control room. In the example in Fig. 1, the cooling unit 120 is separate from the X-ray source 110 and connected in a flow circuit to the X-ray source via conduits 132. Such a conduit 132 may be a hose or pipe for transporting medium such as oil or water.

The cooling unit in the example is configured to provide a flow 130 of cooling medium towards the X-ray source as well as to receive 140 cooling medium back from the X-ray source to complete the cooling circuit. For illustration, Fig. 1 shows a simple example of a cooling circuit. However, it is noted that in embodiments the cooling system 100 may employ cooling in multiple stages, with multiple cooling mediums, such as two-stage cooling with e.g. oil, water, or air etc., such as multiple cooling mediums in combination with a heat exchanger.

The controller 150 is configured to receive a stand-by trigger signal. The stand-by trigger signal may be transmitted from the imaging system 102, such as the imaging system controller 180. The stand-by trigger signal from the imaging system 102 may comprise information that the X-ray source is currently in stand-by and/or temporal information indicating when the X-ray source is planned to be in stand-by mode. The stand-by trigger signal may be transmitted from a sensor 170, such as a sensor 170 for sensing parameters of the X-ray source 110 or the X-ray system 102. The sensor 170 may sense e.g. a temperature, sound, rotation of e.g. a gantry of the imaging system, current, voltage etc. In other words, the sensor 170 may sense parameters directly linked to a suitable level of cooling, such as temperature, power usage etc., and/or the sensor may sense the activity of the imaging system 102 and/or X-ray source 110, e.g. via sound, rotation etc. In response to the stand-by trigger signal, the controller 150 controls the cooling unit 120 to provide a stand-by cooling flow rate towards the X-ray source 110. The stand-by cooling flow rate should be sufficient to cool components of the X-ray source when the X-ray source is in a stand-by mode, such as before or in between X-ray applications like X-ray imaging applications. Even when the X-ray source is not used during an application, there will be some level of heating occurring. The stand-by cooling flow is preferably kept at a minimum level that is still sufficient to cool the X-ray source in stand-by mode. Since the cooling unit 120, e.g. a pump of the cooling unit, is operated at a lower frequency when the X-ray source 110 is in stand-by as compared to when in use during an application, overall energy consumption and noise level may be significantly improved. Reducing the noise levels may be of particular importance in cases where a pump of the cooling unit is close to the patient and/or hospital staff, such as e.g. in a computed tomography system. A two-stage (e.g. oil-water) cooling system, such as used in some interventional guided therapy imaging systems, is another example where reduction of noise by improving pump usage may be of high significance for staff and patient experience.

The controller 150 is further configured to receive an application trigger signal. Similarly to the stand-by trigger signal, the application trigger signal may be transmitted from the imaging system 102, such as the imaging system controller 180. The application trigger signal from the imaging system 102 may comprise information that the X-ray source is currently in use for an application and/or temporal information indicating when the X-ray source is planned to be in use for the application. The application trigger signal may be transmitted from the sensor 170. Alternatively, the application trigger signal may be generated by a different sensor than the sensor 170 used to generate the stand-by trigger signal as discussed above. Also in this case, the sensor 170 may sense e.g. a temperature, sound, rotation of e.g. a gantry of the imaging system, current, voltage etc. The sensor may sense parameters directly linked to a suitable level of cooling, such as temperature, power usage etc., and/or the sensor may sense the activity of the imaging system and/or X-ray source, e.g. via sound, rotation etc. In response to the application trigger signal, the controller 150 controls the cooling unit 120 to provide an application cooling flow rate towards the X-ray source 110. The application cooling flow rate is larger than the stand-by cooling flow rate and should be sufficient to cool components of the X-ray source when the X-ray source is in use for the application. In this way, sufficient cooling of the X-ray source can be enabled.

In embodiments, the standby trigger signal may be the absence of the application trigger signal, or vice versa. For example, both the standby trigger signal and the application signal may be voltages on a same trigger signal line, with the standby trigger signal being represented by a different (e.g. lower) voltage than the application trigger signal. For example, the standby trigger signal may be represented by a logical zero, and the application trigger signal may be represented by a logical one. In embodiments, “receiving a standby trigger signal” may be implemented as “not receiving an application trigger signal”, and acting in response to receiving the standby trigger signal may be implemented as acting in response to not receiving the application trigger signal, and vice versa. The claims should be construed as covering all these embodiments, examples, and implementation options.

As discussed above, the application trigger signal may include temporal information to indicate a planned X-ray application. With information about e.g. when a planned X-ray application is about to take place or is planned to change or end, the controller 150 can adapt the application cooling flow, such as to timely ramp up or down the flow of cooling medium, provide advanced or delayed timing to switch to a particular predetermined flow rate of cooling medium etc. In this way, efficient control of the cooling flow rate can be improved, and possibly detrimental temperature peaks can be avoided without constantly having to operate at a maximum cooling flow. The controller 150 may be configured to determine a temporal behavior of cooling and/or heating of components of the X-ray source, such as differences between individual components or groups of components of the X-ray source. By determining and adapting the cooling flow rate and/or the timing of the cooling flow rate to such behavior, the cooling of components of the X-ray source may be improved. A computer model, such as a digital twin, neural network etc., may be used to model the cooling and/or heating behavior of the X-ray source components and/or to model appropriate control of the cooling flow rate to adapt to such behavior. The modelling of temporal behavior of cooling and/or heating of components of the X-ray source may be carried out in advance of using the cooling system 100. Where applicable, e.g. modelling, training of a neural network, optimizing cooling flow rates for various situations etc. may be carried out with a different processor compared to a processor that processes input signals during use of the cooling system 100.

Fig. 2 schematically illustrates an example of a cooling system 100 for cooling an X-ray system 102 having two X-ray sources 110, 210 according to embodiments of the invention. An example of such an X-ray system is a bi-plane X-ray imaging system. The cooling unit 120 is configured to provide a total flow 230 of cooling medium for cooling both X-ray sources 110, 120. The cooling system 100 comprises a flow divider 220 configured to divide the total flow 230 of cooling medium between a partial flow 231 towards one of the X-ray sources 110 and a further partial flow 232 towards the other X- ray source 210. In the example in Fig. 2, cooling medium is returned to the cooling unit via two separate flows 241, 242.

At least one of the partial flows 231, 232 is adapted to be at a stand-by cooling flow rate in response to a stand-by trigger signal for the corresponding X-ray source 110, 210. At least one of the partial flows 231, 232 is adapted to be at an application cooling flow rate in response to an application trigger signal for the corresponding X-ray source 110, 210. The flow divider 220 may preferably be configured to provide an adaptable division of the total flow of cooling medium. The share of the total flow 230 that is divided to be a first partial flow 231 and the share that is divided to be a second partial flow 232 may be electronically controlled, such as via an electronically controlled flow switch, flow adjustment Y-valve, or similar. The controller 150 may be configured to control the cooling unit 120 to adapt the total flow 230 of cooling medium, and/or to control the flow divider 220 to adapt the division of the total flow of cooling medium. Preferably, both the flow divider 220 and the total flow 230 of cooling medium can be individually controlled via the controller 150. The respective trigger signals may comprise information relating to each of the X-ray sources 110, 210 and/or for which X-ray source the status is changing (from stand-by to application or the other way around). Application data and/or temperature measurements for each of the X-ray sources may be considered. The sum of power inputs and/or temperature levels for the X-ray sources may determine the total flow 230 generated by the cooling unit 120. Individual application data and/or temperature data may determine the relative share of cooling medium flow between the X-ray sources. When both X-ray sources 110, 210 are in stand-by mode, a low cooling flow rate may be provided to each of the X-ray sources 110, 210. When one of the X-ray sources is being used for an application, such as during imaging, and the other X-ray source is in stand-by mode, the flow divider 220 may be controlled such that a higher application cooling flow rate is only provided to the X-ray source used for an application, and such that the X-ray source in stand-by still receives the (minimal) stand-by flow rate of cooling medium.

Similarly to the example in Fig. 1, the controller 150 in Fig. 2 may receive trigger signals from an imaging system controller 180 and/or a sensor 170. The application trigger signal may comprise data regarding an X-ray application, and the controller 150 may be configured to adapt the application flow rate based on the X-ray application. The application trigger signal may comprise data regarding a temperature of at least one of the X-ray sources 110, 210. The controller 150 may be configured to adapt the application flow rate for the at least one X-ray source based on such an X-ray source temperature. The application trigger signal may comprise temporal data regarding a planned X-ray application for at least one of the X-ray sources 110, 210. The controller 150 may be configured to adapt the application flow rate and/or a timing of the application cooling flow for the at least one X-ray source based on the application trigger signal. The controller 150 may be configured to determine a temporal behavior of cooling and/or heating of components of at least one of the X-ray sources 110, 210. The controller 150 may be configured to adapt the application cooling flow and/or the stand-by cooling flow to the at least one X-ray source 110, 210 based on the determined temporal behavior.

With the cooling system in Fig. 2, e.g. a bi-plane X-ray system 102 can be sufficiently cooled with an integral cooling capacity that is significantly less than the sum of the cooling capacity for two separately cooled X-ray sources. The sum of the electrical power needed for X-ray generation in such a bi-plane system is smaller than two times the electrical power needed for X-ray generation in a comparable monoplane configuration. Therefore, the cooling system 100 in Fig. 2 may provide a reduced noise level, reduced costs etc. as compared to two separate systems, each cooling one X-ray source. The cooling system 100, such as the cooling systems exemplified in Figs. 1 and 2 may be comprised in or integrated with the X-ray system 102. The X-ray system 102 may be e.g. a medical imaging system or an X-ray system for other purposes, such as scanning luggage. Examples of suitable medical X-ray systems include a computed tomography system, a radiography system, a fluoroscopy system, a C-arm X-ray system for interventional guidance etc.

Fig. 3 schematically illustrates a method for cooling an X-ray source of an X-ray system. The method may be carried out with a cooling system, such as the cooling system described with respect to Fig. 1. The method comprises: receiving 310 a stand-by trigger signal; in response to the stand-by trigger signal, controlling 320 a cooling unit to provide a stand-by cooling flow to the X-ray source; receiving 330 an application trigger signal; and in response to the application trigger signal, controlling 340 the cooling unit to provide an application cooling flow to the X-ray source, wherein an application flow rate of the application cooling flow is larger than a stand-by flow rate of the stand-by cooling flow.

Fig. 4 schematically illustrates a method for cooling at least two X-ray sources of an imaging system according to embodiments of the invention. The method may be carried out with a cooling system, such as the cooling system described with respect to Fig. 2. The method comprises controlling 402, 403 a cooling unit to provide a total flow of cooling medium for cooling at least two X- ray sources. The method in Fig. 4 also comprises controlling 404, 405 a flow divider to divide the total flow of cooling medium between a partial flow towards one of the at least two X-ray sources and a further partial flow towards another of the at least two X-ray sources.

In the example in Fig. 4, the method includes receiving 410 a stand-by trigger signal relating to at least one of the X-ray sources. In response to the stand-by trigger signal, the total flow of cooling medium and the flow divider are controlled 402, 404, such that a stand-by cooling flow rate is provided 420 to the at least one X-ray source. E.g. the partial flow towards one of the at least two X-ray sources is adapted to be a stand-by cooling flow rate in response to the stand-by trigger signal. The method in Fig. 4 includes receiving 430 an application trigger signal relating to at least one of the X-ray sources. In response to the application trigger signal, the total flow of cooling medium and the flow divider are controlled 403, 405, such that an application flow rate is provided 440 to the at least one X-ray source. E.g. the partial flow towards one of the at least two X-ray sources is adapted to be an application cooling flow rate in response to the application trigger signal.

Fig. 5 schematically illustrates an example of the dynamics between X-ray source power, X-ray source temperature and cooling medium flow rate over a period of time. Cooling medium flow rate may be controlled via electrical input parameters to a cooling unit pump. Starting from the left of the time-line in Fig. 5, the applied X-ray source power, as indicated by the line 510, is initially at a low level. The X-ray source 110 may be in a stand-by mode. Some amount of energy may be provided to the X-ray source in the stand-by mode, e.g. to drive an anode rotation, keeping components at a suitable stand-by current/voltage etc. In this way, the X-ray source is on stand-by and ready to be used for an application on short notice without lengthy start-up procedures. As can be seen from the temperature curve 520, thanks to the comparatively low supplied power, the temperature of the X-ray source 110 is also at a comparatively low level. The flow rate 530 of cooling medium is kept at a minimal stand-by flow rate. In other words, in the stand-by mode the energy consumption and noise for cooling the system may be kept at a low level.

At the time point indicated with a black arrow 540, an application trigger signal is received. In this example, the application trigger signal indicates that a change is about to happen, i.e. it indicates a planned or predicted change. E.g., the application trigger signal may indicate that the X-ray source power 510 is about to increase at a certain moment in time. Such as when a planned imaging acquisition is initiated. Alternatively, or additionally, the application trigger signal may indicate an instant parameter value detected by a sensor 170, such as by a temperature sensor, rotation sensor, current sensor, voltage sensor, sound sensor, etc., or a communicated or detected activity by the X-ray source 110 and/or X-ray system 102.

In response to the application trigger signal 540, the cooling medium flow rate 530 is increased to a level of an application flow rate. In this example there is a small delay after receiving the application trigger, e.g. to provide for a suitable timing with respect to the application that is about to happen. Although there is a delay, the application cooling flow rate in Fig. 5 is started before the increase in X-ray source power, such that the adapted cooling medium flow rate may cool the components of the X-ray source on time. Temporal behavior of cooling with the flow of cooling medium and/or heating of the components resulting from e.g. applied power to the X-ray source may be determined in advance, e.g. using a computer model. There may be a large (several seconds) delay between energy being deposited in the X-ray source and a heat wave arriving at the internal X-ray source structures (frame, window, bearing axis, etc.) which are in contact with the cooling medium.

When the X-ray source power 510 increases, this leads to an increase in temperature 520. In this example, the temperature 520 remains at an elevated level also after the X-ray source power 510 has been ramped down again, e.g. when imaging acquisition is finalized. Because of the higher application flow rate of cooling medium 530 as compared to the stand-by flow rate, the temperature 120 may be managed such that it does not exceed an allowed threshold. In other words, the application cooling flow rate provides sufficient cooling flow to keep the X-ray source at an acceptable temperature during and after use in an application.

At a point in time indicated with a white arrow 550, a stand-by trigger signal is received. The stand-by trigger signal may be triggered by a timer from the application trigger signal in 540. Alternatively, or additionally, the stand-by trigger signal may originate from a sensor, such as a temperature sensor indicating the X-ray source temperature 520. Alternatively, or additionally, the standby trigger signal may be initiated by the ramp-down in X-ray source power 510, e.g. in combination with a delay to allow for the temperature to drop. In the example in Fig. 5, the cooling medium flow rate 530 is, in response to the stand-by trigger signal, immediately ramped down to the stand-by-flow rate.

With the sequence as indicated in Fig. 5, the energy consumption, cost, noise level etc. of the cooling system may be significantly reduced as compared to e.g. constantly cooling the X-ray source. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and/or by means of a suitably programmed processor. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. Measures recited in mutually different dependent claims may advantageously be used in combination.

Claims

Claim 1. A cooling system (100) for an X-ray system (102), wherein the cooling system comprises: a cooling unit (120) configured to provide a total flow (230) of cooling medium for cooling an X-ray source (110) and a further X-ray source (210); a flow divider (220) configured to divide the total flow (230) of cooling medium between a partial flow (231) towards the X-ray source (110) and a further partial flow (232) towards the further X- ray source (210); and a controller (150) for controlling the cooling unit (120), wherein the controller is configured to: receive a stand-by trigger signal, and in response to the stand-by trigger signal, control the cooling system (100) to adapt the partial flow (231) to provide a stand-by cooling flow towards the X- ray source (110) at a stand-by flow rate; and receive an application trigger signal, and in response to the application trigger signal, control the cooling system (100) to adapt the partial flow (231) to provide an application cooling flow towards the X-ray source (110) at an application flow rate, wherein the application flow rate of the application cooling flow is larger than the standby flow rate of the stand-by cooling flow.

Claim 2. The cooling system according to claim 1, wherein the flow divider (220) is configured to provide an adaptable division of the total flow (230) of cooling medium between the partial flow (231) and the further partial flow (232), and wherein the controller (150) is configured to control the cooling unit (120) to adapt the total flow (230) of cooling medium, and/or to control the flow divider (220) to adapt the division of the total flow of cooling medium.

Claim 3. The cooling system according to claim 1 or 2, wherein the application trigger signal comprises data regarding an X-ray application, and wherein the controller (150) is configured to adapt the application flow rate based on the X-ray application.

Claim 4. The cooling system according to claim 3, wherein the data regarding the X-ray application comprises at least one of an X-ray source voltage, an X-ray source current, a number of X-ray imaging frames, an exposure time, an anode rotation frequency, and an imaging system gantry rotation frequency.

Claim 5. The cooling system according to any of the preceding claims, wherein the application trigger signal comprises data regarding an X-ray source temperature, and wherein the controller (150) is configured to adapt the application flow rate based on the X-ray source temperature.

Claim 6. The cooling system according to any of the preceding claims, wherein the application trigger signal comprises temporal data regarding a planned X-ray application, and wherein the controller (150) is configured to adapt the application flow rate and/or a timing of the application cooling flow based on the application trigger signal.

Claim 7. The cooling system according to any of the preceding claims, wherein the controller (150) is configured to determine a temporal behavior of cooling and/or heating of components of the X- ray source, and wherein the controller (150) is configured to adapt the application cooling flow and/or the stand-by cooling flow based on the determined temporal behavior.

Claim 8. An X-ray system (102) comprising an X-ray source (110), a further X-ray source (210), and the cooling system (100) according to any of the preceding claims.

Claim 9. A cooling method for an X-ray system, the method comprising: controlling (402) a cooling unit to provide a total flow of cooling medium for cooling an X-ray source and a further X-ray source; controlling (404) a flow divider to divide the total flow of cooling medium between a partial flow towards the X-ray source and a further partial flow towards the further X-ray source; receiving (310) a stand-by trigger signal; in response to the stand-by trigger signal, controlling (320) the cooling unit and/or the flow divider to adapt the partial flow to provide a stand-by cooling flow at a stand-by flow rate to the X- ray source; receiving (330) an application trigger signal; and in response to the application trigger signal, controlling (340) the cooling unit and/or the flow divider to adapt the partial flow to provide an application cooling flow at an application flow rate to the X-ray source, wherein the application flow rate of the application cooling flow is larger than the standby flow rate of the stand-by cooling flow.

Claim 10. The method according to claim 9, wherein the application trigger signal comprises data regarding an imaging application, and wherein the method comprises adapting the application flow rate based on the X-ray application.

Claim 11. The method according to claim 9 or 10, wherein the application trigger signal comprises data regarding an X-ray source temperature, and wherein the method comprises adapting the application flow rate based on the X-ray source temperature.

Claim 12. A computer program element, which, when being executed by a controller of a cooling system for an X-ray system, is adapted to cause the controller to perform the method according to any of claims 9-11.

Claim 13. A computer-readable medium having stored thereon the computer program element of claim 12.