X-ray tube filament operation

Abstract

The present invention relates to the operation of a filament of an X-ray tube. In order to provide an X-ray tube with improved wear, a control device 10 for pulsed operation of a generator for an X-ray tube is provided. The X-ray tube is controlled to provide a plurality of X-ray pulses, two successive pulses separated in time by an emission pause. The emission pause comprises at least a first and a second part. A filament current is provided to a cathode filament of the X-ray tube such that in an emission pause between two successive pulses, a first filament current is provided during the first part of the pause and a second filament current is provided during the second part of the pause, the first filament current being lower than the second filament current. By operating the filament in this way, the filament temperature is reduced, which results in a significantly less wear and tear on the X-ray tube and an increased lifespan of the X-ray tube.

Description

[Technical field]

[0001] The invention relates to the operation of a filament in an X-ray tube, in particular to a control device for the pulsed operation of a generator for an X-ray tube, a generator for the voltage supply of an X-ray tube, an X-ray imaging system and a method for operating a generator of an X-ray tube in a pulsed manner. [Background technology]

[0002] X-ray imaging is considered an important imaging modality in medical imaging. An X-ray tube is used to generate X-ray radiation that passes through a subject and strikes an X-ray detector. For various reasons, e.g., limitations in certain flat X-ray detectors, it is necessary to generate the X-ray radiation in a pulsed manner. In such pulsed X-ray image acquisition, an X-ray image is acquired using a series of short X-ray pulses. Such a series of pulses is called an imaging run.

[0003] A critical part in an X-ray tube is the cathode filament. The filament must have a certain high temperature to reach the desired emission current during the X-ray pulse. X-ray tubes used, for example, in cardiovascular X-ray systems, exhibit wear of the cathode filament. The wear is the result of deposition of the tungsten of which the cathode filament is composed. Summary of the Invention [Problem to be solved by the invention]

[0004] There is therefore a need to provide an X-ray tube, particularly for pulsed operation, with improved field life. [Means for solving the problem]

[0005] The object of the present invention is solved by the subject matter of the independent claims, further embodiments are incorporated in the dependent claims. It is noted that the below described aspects of the invention also apply to a control device for the operation of a generator for an X-ray tube, a generator for the voltage supply of an X-ray tube, an X-ray imaging system and a method for operating a generator of an X-ray tube.

[0006] According to one embodiment, a control device for pulsing a generator for an X-ray tube is provided. The control device includes a data input and a controller. The data input is configured to provide a signal for an X-ray imaging run including a plurality of X-ray pulses for acquiring at least one X-ray image. The controller is configured to control the generator to provide a filament current for generating heat in a filament of an X-ray cathode. The generator is configured to provide a plurality of X-ray pulses, whereby each two consecutive X-ray pulses of the plurality of X-ray pulses are separated in time by an emission pause. The emission pause includes at least a first portion and a second portion. To provide the filament current, the controller is further configured to control the generator to adjust the filament current in an emission pause between two consecutive pulses, whereby to provide at least a first filament current during a first portion of the pulse and a second filament current during a second portion of the pause. The first filament current is lower than the second filament current.

[0007] In a preferred embodiment, the controller is configured to provide filament currents at an operational level during an x-ray pulse, the first filament current being lower than the operational level and / or the second filament current being higher than the operational level, accordingly, providing the first filament current is also referred to as "blanking" and providing the second filament current is also referred to as "boosting" hereinafter.

[0008] Thus, in effect, during a first portion of the emission pause, the filament temperature is reduced from an operational value and the second filament current is provided as an intermediate heating current to restore the filament temperature to the operational value during a second portion of the emission pause, i.e., the operational value of the filament temperature corresponds to the temperature required to emit the electron beam during an x-ray pulse.

[0009] By operating the filament in this manner, during pulsed operation of the x-ray tube, the filament temperature between pulses is lower than if the filament current were continuously held at the operating level, thereby resulting in significantly less wear without impairing the quality of the x-ray beam or other significant effects. The effect is that the filament is subjected to a lower temperature between pulses, which results in less deposition of tungsten and therefore less wear.

[0010] According to one example, the controller is configured to control the generator such that the first and second filament currents are applied repeatedly during at least a portion of the emission pauses, thereby resulting in repeated cooling and heating of the filament during pulsed operation of the x-ray tube.

[0011] In one example, cooling and heating of the filament occurs during each emission pause between two successive pulses of each of the multiple X-ray pulses.

[0012] In an alternative example, cooling and heating of the filament occurs during a subset of emission pauses, for example, during pauses after a predetermined number of pauses have occurred with no or at least a reduced degree of blank / boost activation.

[0013] According to one example, the controller is configured to control the generator such that the duration of the first portion and the duration of the second portion are determined based on a weighted calculation of results from the boost curve and results from the blank curve to extract blank and boost times within a given pulse pause duration while still reaching an operating filament temperature during the pulse.

[0014] For example, the sum of the boost and blank times must be less than or equal to the pause duration and reach the operating current at the end of the pause.

[0015] In one example, the controller is configured to control the generator such that the duration of the first portion and the duration of the second portion are determined based on a weighted calculation of the results from the boost curve and the blank curve to derive a maximum blank time and a maximum boost time for a given pulse pause duration while still reaching the operating filament temperature at the start of the next pulse.

[0016] Note that in one example, both the blank and boost are made to be maximum in the sense that they fall exactly within each pause and still reach the operating current when the next pulse of the imaging run begins. They could both be shorter, but then the filament would be heated for longer at a less optimal operating level.

[0017] Note that the length of the first portion and the length of the second portion are not independent. The exact blank and boost curves are taken as the basis for calculating the optimal switch point. The temperature drop during the first portion needs to be compensated by the temperature increase during the second portion (unless the generator is tuned to a different voltage / emission current set point). The blank and boost curves predict how much time will be required for blanking and boosting to achieve this with the blank and boost currents chosen for the first and second filament currents.

[0018] According to one example, to generate an electron beam having a desired emission current for generating X-ray pulses for an imaging run, the controller is configured to control the generator to provide a plurality of voltage pulses corresponding to the X-ray pulses. Additionally or alternatively, the controller is configured to repeatedly open the electric field-based suppression device, each opening of the device corresponding to one of the plurality of X-ray pulses.

[0019] According to one example, the controller is configured to control the generator such that the current during the first portion of the pause is sufficient to define a predetermined minimum current to be maintained as the available current throughout the pause.

[0020] According to a further aspect, a generator for a pulsed voltage supply of an X-ray tube is further provided. The generator includes as generator components a control device according to one of the previous examples, a power input, an electrical transformer arrangement, and a power output. The power input is connectable to a power source configured to provide an input in the form of electrical energy for operating the X-ray tube. The power source is connected to the electrical transformer arrangement. The electrical transformer arrangement is configured to convert the electrical input into a suitable DC high voltage and a suitable current for the pulsed operation of the X-ray tube. The power output is configured to provide a suitable high voltage and a suitable current. The power output is connectable to the X-ray tube. Furthermore, the control device is configured to control the generator components.

[0021] According to a further aspect, an X-ray imaging system is provided, the system including an X-ray tube for generating X-ray radiation, a control device according to one of the above examples, and a generator for voltage supply of the X-ray tube according to the above examples. The X-ray tube includes an anode and a cathode. The cathode includes at least one cathode filament for emitting at least one electron beam towards the anode. The control device controls the pulsing of the cathode filament by controlling an electric transformer arrangement of the generator.

[0022] According to a further aspect, there is also provided a method of operating an X-ray tube generator in a pulsed manner, the method comprising the steps of: providing a signal for an x-ray imaging run including a plurality of x-ray pulses for acquiring at least one x-ray image; providing a filament current to generate heat in a filament of a cathode of the x-ray tube to reach a desired emission current during an x-ray pulse; generating an electron beam having a desired emission current directed from the cathode to the anode of the X-ray tube under the influence of a voltage between the anode and the cathode to generate a plurality of X-ray pulses with desired characteristics.

[0023] To provide filament current, the following steps are performed: providing a plurality of pulses to generate an electron beam having a desired emission current to generate a plurality of x-ray pulses, where two consecutive pulses of the plurality of pulses are separated in time by an emission pause, the emission pause including at least a first portion and a second portion; In an emission pause between two successive pulses, a step of adjusting the filament current is performed, whereby a first filament current is provided in a first portion of the pause and a second filament current is provided in a second portion of the pause.

[0024] The first filament current is lower than the second filament current, preferably the first filament current is too low to maintain the filament temperature to reach the desired emission current of the electron beam, and the second filament current is provided as an intermediate heating current to prepare the filament for the desired emission current of the electron beam for the next x-ray pulse.

[0025] According to one aspect, a control of the energy supply of the filament of an X-ray tube is provided that supplies a stepped current for heating the filament in order to reduce wear during operation of the X-ray tube. The stepped current is applied during the pause between two successive X-ray pulses. In a first part, a lower current is supplied, i.e. a first filament current, e.g., just enough current to ensure that sufficient energy is supplied to other components of the tube. The lower current allows the filament to cool. The lower current therefore provides a blank (particularly with respect to filament temperature). In a second part, a higher current is supplied to emit electrons towards the anode of the X-ray tube during a subsequent X-ray pulse, thereby heating the cathode filament to the required temperature required to generate X-ray radiation. The higher current heats the filament at a faster rate. The higher current therefore provides a boost (particularly with respect to filament temperature).

[0026] Preferably, during pulse pauses, regardless of whether the cooling or heating period is greater, the temperature of the filament is lower than if the operating filament current had been maintained during this period.

[0027] In one example, between pulses, the temperature of the filament is reduced to the lowest possible value, but the filament is brought back up to the operating temperature in time for the next pulse.

[0028] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0029] Exemplary embodiments of the invention are described below with reference to the following drawings: [Brief description of the drawings]

[0030] [Figure 1] FIG. 2 shows a schematic diagram of an example of a control device for operating a generator for an X-ray tube. [Diagram 2] FIG. 2 shows a schematic diagram of an example of a generator for the voltage supply of an X-ray tube. [Diagram 3] FIG. 1 is a diagram illustrating an example of an X-ray imaging system. [Figure 4] FIG. 2 illustrates steps of an example method for operating an X-ray tube generator. [Diagram 5] FIG. 1 shows a graph with curves representing different currents and voltages during an exemplary imaging run. [Figure 6a-6b] FIG. 6 shows the curves of FIG. 5 in separate graphs for better visualization. [Figure 7a-7d] FIG. 1 shows a graph with boost and blank curves as an example for determining blank and boost times. [Figure 8] 1 is a graph showing emission current and intermediate cooling current, and estimated consumption savings for an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Next, specific embodiments will be described in more detail with reference to the accompanying drawings. In the following description, similar drawing reference numbers are used for similar elements in different drawings. Matters defined in this specification, such as detailed configurations and elements, are provided to facilitate a comprehensive understanding of the exemplary embodiments. Also, well-known functions or configurations are not described in detail, since they would obscure the embodiments in unnecessary detail. Moreover, expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements, and do not modify individual elements of the list.

[0032] In a thermionic X-ray tube, electrons emitted by a heated cathode are accelerated by a strong electric field in a vacuum towards the anode, where they produce "bremsstrahlung", also known as X-rays, when produced by an X-ray tube. The amount of X-rays is proportional to the emission current flowing between the anode and the cathode. Apart from the cathode surface size, surface condition, and material, which are "fixed" in a particular tube design, the emission current is a function of the voltage between the cathode and the anode and the temperature of the cathode. The cathode is usually a strip or coil of a high melting point metal, such as tungsten, called the filament. When the cathode is heated, the metal of the filament evaporates and eventually the filament becomes very thin at a certain place and breaks. This explains the general wear mechanism of thermionic X-ray tubes.

[0033] For imaging, X-ray tubes are operated in a pulsed mode. Rather than producing a sustained amount of X-rays, the X-ray tube produces a series of short pulses of high intensity, called an imaging run. This mode of operation supports detectors that require a reset period during which no X-rays are produced during two imaging frames. In addition, the short, intense pulses result in less image blurring due to motion.

[0034] Based on the type of procedure and, for example, the x-ray retention experienced in the previous image, the tube voltage, emission current, and pulse width settings are determined. At that point, the filament is held at standby temperature by passing a standby filament heating current through the filament. This current is between 2A and 3A. Based on the desired set points of the tube voltage and emission current, the operating filament current is determined by interpolation, for example, using a look-up table called a static adaptation table, in which the relationship between the filament current, the tube voltage, and the resulting emission current is recorded. The operating filament current is between 4A and 6A. The "boost time" required to "boost" the filament temperature from the standby temperature to the operating temperature is then determined by interpolating a table called a boost table. At the beginning of the run, a boost current, typically about 8A, is passed through the filament to rapidly heat it up to the operating temperature, after which the operating filament heating current is applied. If there are no changes in the set points, this current remains the same for the duration of the run. Also, an "idle-blank time" is determined by interpolation of the blank table. After the run, an idle-blank current of about 1-1.5 A is applied again to rapidly reduce the filament temperature to the standby temperature.

[0035] As the filament wears out (evaporates), its resistance changes over time, which means that the recorded static fit table and the boost and blank tables become less accurate over time. For this reason, an automatic adjustment of the fit table to compensate for the wear of the filament is made, and the fit table is updated for every run. This eliminates the need for fit procedures after an initial fit procedure during the life of the tube for X-ray generators in which this method is implemented. The method continually corrects the values ​​obtained from the static fit table and the boost and blank tables to remain accurate over the entire tube life in the field.

[0036] 1 shows a schematic diagram of an example of a control device 10 for operating a generator for an X-ray tube. The control device 10 includes a data input 12 and a controller 14. The data input 12 is configured to provide a signal for an X-ray imaging run including a plurality of X-ray pulses for acquiring at least one X-ray image. The controller 14 is configured to control the generator to provide a filament current for generating heat in a filament of a cathode of the X-ray tube. The generator thereby generates an electron beam with a desired emission current directed from the cathode to the anode of the X-ray tube under the influence of a tube voltage between the anode and the cathode to generate an X-ray pulse with desired characteristics.

[0037] The controller 14 is configured to control the X-ray tube to supply a plurality of pulses to generate an electron beam having a desired emission current to generate a plurality of X-ray pulses, two successive pulses of the plurality of pulses being separated in time by an emission pause, i.e., during a pulse, the filament current supplied corresponds to a normal operating current level that would emit an electron beam at the desired emission current from the cathode towards the anode at a corresponding tube voltage.

[0038] The emission pause includes at least a first portion and a second portion. The controller 14 is further configured to control the generator to adjust the filament current in the emission pause between two successive pulses, thereby supplying a first filament current during the first portion of the pause and a second filament current during the second portion of the pause. The first filament current is lower than the second filament current, and preferably also lower than the operating current level. In effect, the first filament current is too low to maintain the filament at a temperature required for the emission of the electron beam. As a result, the filament temperature drops during the first portion of the emission pause.

[0039] Preferably, the second filament current is provided as an intermediate heating current to prepare the filament for subsequent emission of the desired emission current of the electron beam during the next X-ray pulse. Preferably, the second filament current is higher than the operating current level, so that at the start of the next pulse, the temperature of the filament is restored to the operating value required for emission of the electron beam.

[0040] Accordingly, the supply of the first and second filament currents, i.e. blanking and boosting, is performed between successive pulses in an imaging run to conserve filament wear. That is, the current supplied to the filament of the X-ray tube is first reduced to the first filament current between successive pulses of an imaging run, thereby cooling the filament. Shortly before the next pulse, an increased boosting current is used as the second filament current, so that the filament returns to the operating temperature at the start of the pulse. This is repeated throughout the pulsed imaging run, preferably within each of two adjacent X-ray pulses.

[0041] A first arrow indicates the supply of signals, for example from a user interface 18 to the control device 10. A second arrow indicates the supply of control commands, signals etc. of the controller 14, for example to an X-ray imager 22. The frame 24 indicates the option of arranging the data input 12 and the controller 14 in a common structure or housing. However, they may also be arranged in a decoupled manner.

[0042] The controller 14 is also called a data processor.

[0043] In one example, the controller 14 is configured to control the generator to adjust the filament current in a pulse pause between two successive pulses and to supply an additional filament current in the additional portion of the pause. In one example, the additional filament current is supplied after the second filament current, the additional filament current being lower than the second filament current. In yet another option, the additional filament current is higher than the current during the first portion of the pause.

[0044] Optionally, not shown in detail, the controller 14 is configured to control the generator such that a first filament current is provided during the first portion of the pause, the first filament current being lower than the second filament current.

[0045] In one example, the first filament current is low at 0 A, e.g., no current at all.

[0046] Supplying a current lower than the operating current for some of the interpulse parts results in a lower temperature of the filament during the pause between two pulses, which results in less wear of the filament. Lower current also results in lower temperature, which results in a cooling effect. This is also called intercooler or intercooling method.

[0047] The effect is to reduce wear or severe wear of the filament by reducing the time that operating current is continuously supplied to the filament during an entire imaging run. Reducing the current by 2 / 10 A has been shown to approximately double the lifetime. Increasing the current by 2 / 10 A approximately halves the lifetime.

[0048] In other words, a standby current is applied outside of a run, a boost current is applied in preparation for a run, an operating current is applied during a pulse, and a blank current is used after the run. A first filament current is applied after a pulse, and a second filament current is applied before the next pulse. During a pulse, an operating current is applied, followed by the first filament current, then the second filament current, and then back to the operating current for the next pulse. Preferably, the first and second filament currents are applied between two successive pulses of each of the multiple x-ray pulses of an imaging run. However, in accordance with this, alternative schemes are envisaged in which the first and second filament currents are applied during some emission pauses but not during other pauses, e.g., in an alternating manner.

[0049] In one example, in a very long pause between two pulses, an additional filament current approximately equal to the standby current is provided between the first filament current and the second filament current.

[0050] With this scheme in mind, the second filament current becomes the operating current, and the correct operating current is lower than the second filament current, rather than the second filament current being followed by the first filament current or a current lower than the first filament current, the first filament current being followed by a standby current higher than the first filament current.

[0051] In such variations, if the first filament current is not equal to a "blank" current used to return the filament to the standby temperature, or if the second filament current is not equal to a "boost" current to heat the filament from the standby temperature to the operating temperature, then different "boost" and / or "blank" curves must be used to determine the duration of the first and last portions of the pause.

[0052] In one example, the second filament current is provided in the second or third portion of the pause. Note that the pause may also refer to other portions, i.e., more portions. In one example, the further portion is disposed between the first and second portions.

[0053] In another option, not shown in detail, the controller 14 is configured to control the generator such that application during the first portion of the pause and application of the second filament current results in cooling and heating of the filament during each pause.

[0054] In one example, the controller 14 is configured to control the generator such that a first filament current is supplied during a first portion of the pause and a second filament current is supplied during a second portion of the pause.

[0055] In one example, the first portion is larger than the second portion.

[0056] In one example, the second portion is larger than the first portion.

[0057] In another example, the first portion is equal to the second portion.

[0058] In a further option, not shown in detail, the controller 14 is configured to control the generator such that the duration of the first portion and the duration of the second portion are maximized based on a weighted calculation of the results from the boost curve and the blank curve to yield blank and boost times for a given pulse pause duration while still reaching the operating filament temperature during the pulse.

[0059] In a further option, also not shown in detail, the controller 14 is configured to control the generator such that the blank curve and the boost curve are interpolated from a look-up table.

[0060] Optionally, but not specifically shown, the lookup table is updated based on the detected depletion of the filament. Optionally, in addition or alternatively, the results from the lookup table are corrected for the detected depletion of the filament.

[0061] In another option, not shown in detail, the controller 14 is configured to control the generator to provide at least two voltage pulses to generate an electron beam having a desired emission current to generate an x-ray pulse. Alternatively, or in addition, the controller 14 is configured to open the electric field-based suppression device twice.

[0062] For example, the electric field-based suppression device may be implemented as a grid switch.

[0063] In one example, the pulse is generated by a magnetic field.

[0064] Optionally, not shown in detail, the controller 14 is configured to control the generator such that after the second filament current, the operating filament current is supplied in a pulse.

[0065] In one example, the controller 14 is configured to control the generator such that a transition from the second filament current to the operating filament current occurs immediately before an emission pulse of the emission current is generated.

[0066] In one example, the controller 14 is configured to control the generator such that the operating filament current is provided after the second filament current and before the voltage pulse for the emission current is generated.

[0067] In one example, the controller 14 is configured to control the generator such that multiple sequences of pulses are provided for multiple images, each pulse in the sequence being separated from the preceding / following pulse by a pulse pause, and the first and second filament currents are provided consecutively or interrupted by a standby filament current in case of very long pauses. Furthermore, the sequence of pulses is followed by an idle time, after which a further imaging sequence is provided, during at least a part of the idle time an idle filament current is provided. Furthermore, at the start of this idle time, a first idle filament current is provided to cool the filament to a standby temperature, and then a second idle filament current is provided during the remaining time of the idle time to maintain the standby temperature (standby current). Optionally, the second idle filament current is chosen to be higher than the first filament current, such that the heating time to the operating temperature is as short as possible, but thermionic emission does not take place at the highest operating voltage between the anode and the cathode.

[0068] In one example, the first idle filament current is provided as the first filament current, where the first idle filament current is referred to as the first filament current, and the second idle filament current is referred to as the standby filament current.

[0069] The multiple images are also referred to as a sequence of images.

[0070] Optionally, not shown in detail, the controller 14 is configured to control the generator such that before the sequence of pulses is delivered, a heating filament current is delivered, the heating filament current being equal to the second filament current.

[0071] In one example, the heating filament current is approximately equal to the second filament current.

[0072] Optionally, although not shown in detail, the controller 14 is configured to control the generator such that the current during the first portion of the pause is sufficient to define a predetermined minimum current to be maintained as the effective current throughout the entire pause.

[0073] In one example, the first filament current is sufficient to define a predetermined minimum current to be maintained as the active current throughout the pause.

[0074] In one example, the sequence of pulses is followed by an idle period after which a further imaging sequence is delivered, and the controller is configured to control the generator such that the idle filament current is sufficient to define a predetermined minimum current to be maintained as the effective current throughout the pause.

[0075] In one example, the first filament current and the idle filament current are the lowest currents in the setup and all other currents are higher. The approach is to ensure that there is enough current to maintain the grid switch electronics internal to the x-ray tube.

[0076] In a tube without a grid switch, the first filament current and also the idle filament current are 0A.

[0077] In one example, the controller 14 is configured to control the generator such that the first and second filament currents are provided with parameters that maintain a predetermined minimum current as the effective current throughout the pause, the parameters including filament current values ​​and durations of the first and second filament currents.

[0078] Fig. 2 shows a schematic example of a generator 50 for a pulsed voltage supply of an X-ray tube. The generator 50 includes an example of a control device 10 according to one of the previous examples. Furthermore, a power input 52, an electrical transformer arrangement 54 and a power output 56 are provided. The power input 52 is connectable to a power source configured to provide an input in the form of electrical energy for operating the X-ray tube. The power input 52 is connected to the electrical transformer arrangement 54. The electrical transformer arrangement 54 is configured to convert the voltage input into a suitable DC high voltage and a suitable current for the pulsed operation of the X-ray tube. The power output 56 is configured to provide a suitable high voltage and a suitable current. The power output 56 is connectable to the X-ray tube. The control device 10 is configured to control said generator components, for example the electrical transformer arrangement 54.

[0079] The frame 58 indicates the option of arranging the control device 10, the power input 52, the electrical transformer arrangement 54, and the power output 56 in a common structure or housing. However, they may also be arranged in a decoupled manner. A first arrow 60 indicates the signal supply. A second arrow 62 indicates the electrical output.

[0080] 3 shows a schematic diagram of an example of an X-ray imaging system 100. The X-ray imaging system 100 comprises an X-ray tube 102 for generating X-ray radiation. Furthermore, the X-ray imaging system 100 comprises an example of a control device 10 according to one of the previous examples and an example of a generator 50 for a voltage supply of the X-ray tube according to the previous examples. The X-ray tube 102 comprises an anode and a cathode (not shown in detail). The cathode comprises at least one cathode filament for emitting at least one electron beam towards the anode. The control device 10 controls the operation of the cathode filament by controlling an electric transformer arrangement 54 of the generator 50.

[0081] As an example, the X-ray tube 102 is mounted on one end of a C-arm 106, which has a detector 108 at its other end. A subject support 110 is shown. Also shown near the subject support 110 is a display device 112. The C-arm and other equipment are mounted to a ceiling support structure. A console 114 is shown in the lower right front of FIG. 3, which includes a display along with a mouse, keypad, tablet and control knobs for actively controlling the X-ray imaging system 100. Connection lines 104 indicate data connections between the console 114 and the control device 10 and the generator 50.

[0082] In one example, the cathode is comprised of two cathode filaments for emitting an electron beam towards the anode.

[0083] 4 illustrates steps of an example method 200 for operating an X-ray tube generator in a pulsed manner. The method 200 includes the following steps.

[0084] In a first step 202, a signal is provided for an x-ray imaging run including a number of x-ray pulses for acquiring at least one x-ray image.

[0085] In a second step 204, a filament current is provided to generate heat in a filament of the cathode of the x-ray tube to reach a desired emission current during an x-ray pulse.

[0086] In a third step 206, an electron beam having a desired emission current is generated that is directed from the cathode to the anode of the X-ray tube under the influence of a voltage between the anode and the cathode to generate an X-ray pulse with desired characteristics.

[0087] To provide filament current, the following steps are taken:

[0088] In a fourth step 208, a plurality of pulses are provided to generate an electron beam having a desired emission current for generating a plurality of X-ray pulses, where two consecutive pulses of the plurality of pulses are separated in time by an emission pause, the emission pause including at least a first portion and a second portion.

[0089] In a fifth step 210, during an emission pause between two successive pulses, the filament current is adjusted, thereby providing at least a second filament current during a second portion of the pause.

[0090] In the first portion, the filament current is lower than the second filament current and is too low to maintain the filament temperature to reach the desired emission current of the electron beam.

[0091] The second filament current is provided as an intermediate heating current to prepare the filament for the desired emission current of the electron beam for the next x-ray pulse.

[0092] In one example, the second filament current is provided during a final portion of the pause.

[0093] In one example, one pulse provides one image. In another example, two or more pulses are provided for a single image. However, the intercooler scheme provided is for all variations in which multiple pulses are used and at least one pulse pause is provided between two consecutive pulses.

[0094] In one example, the x-ray pulses are not generated for the purpose of producing an image, but rather for calibrating components of an imaging system or measuring aspects of the imaging system performance.

[0095] In one example of this method, the first filament current is too low to maintain the filament temperature to reach the desired emission current of the electron beam.

[0096] FIG. 5 shows a graph 500 with curves representing different currents and voltages during an exemplary imaging run. The left vertical axis 502 shows the tube voltage and emission current, while the right vertical axis 504 shows the filament current. The horizontal axis 506 shows time. FIG. 5 shows a first curve 508 of the tube voltage and a second curve 510 of the emission current (for better understanding, the curves are shown separately in FIG. 6a and FIG. 6b). The third curve 512 shows the intermediate cooling current, and the fourth curve 513 (only partially shown) shows the filament current when no intercooler scheme is used. It is noted that the filament current follows the intermediate cooling current in a first part before the pulse and in a second part after the pulse. It is also noted that in this case, a field suppression device, also known as a grid switch, is used to create the pulses, and the tube voltage is kept at a constant level during the entire run.

[0097] Four markers 514 indicate four X-ray pulses. A pause 516 is provided between the pulses 514. Note that the pulse itself has a duration 518. The four X-ray pulses form a sequence of pulses, also called a run 520. The run 520 is followed by a blanking period as a first part of a wait or idle period 522, after which the filament current returns to a standby current. Initially, i.e. before the first pulse of the (first) run, a start period 524 is provided, during which an initial heating of the filament takes place. Prior to the initial heating, a standby mode is provided. The run 520 and idle periods 522 form a clock rate 526, during which the runs and idle periods are consistently repeated.

[0098] The pauses 516 between the pulses 514 are shown to include a first portion 528 for a blanking phase and a second portion 530 for a boost phase.

[0099] As an example, the pulses are generated using a grid, eg, a field suppression device, and the voltage remains constant during the run.

[0100] In other examples, the pulses are generated in other possible ways.

[0101] Figures 6a and 6b show the curves of the graph 500 of Figure 5 in separate graphs 600a and 600b for better visualization. The left vertical axis 602 shows the tube voltage and the emission current, while the right vertical axis 604 shows the filament current. The horizontal axis 606 shows the time. Figure 6a shows a first curve 608 of the tube voltage and a second curve 610 of the emission current. Furthermore, a third curve 612 of the intercooler current is shown in Figure 6b. Four markers 614 show four X-ray pulses. It should be noted that the very short indicated periods at the beginning and end of the curve 612 show the standby current, the lowest level shows the blank current, the highest level shows the boost level, and the four short plateaus between the boost and blank levels show the operating current.

[0102] 7a, 7b, 7c, and 7d show graphical illustrations of how the duration of the first and second phases in a pulse pause can be obtained using the boost and blank curves as an example. The vertical axis 702 shows the filament current. The horizontal axis 704 shows the boost or blank time.

[0103] 7a shows a first graph 700a with a boost curve 706 and a blank curve 708. As a first step, the operating current is determined and identified in the graph, as shown by the hash line 710.

[0104] 7b shows a second graph 700b with a boost curve 706 and a blank curve 708. As a next step, the two curves 706, 708 are virtually moved to intersect at the operating current 710. For example, the blank curve 708 is moved to the right, as indicated by the hash line 708'.

[0105] 7c shows a third graph 700c with a boost curve 706 and a blank curve 708. As a next step, a location is identified where a defined pulse pause 712 (given by the determined pulse rate and pulse width) fits between the curves. For example, the pulse pause 712 is moved upwards as shown by the hash line 712'.

[0106] 7d shows a fourth graph 700d with a boost curve 706 and a blank curve 708. The blank time 714 and boost time 716 can be determined by protruding the intersection point vertically, as shown by hash line 718.

[0107] The shape of the curve segment is used to calculate the "wear" at rest.

[0108] 8 shows a graph 800 illustrating an example emission current and intermediate cooling current. The left vertical axis 802 shows emission current and depletion. The right vertical axis 804 shows filament current. The horizontal axis 806 shows time. A first curve 808 shows emission current, a second curve 810 shows intermediate cooling current, a third curve 812 shows equivalent current (obtained from blank and boost curve sections), a fourth curve 814 shows operating current, and a fifth curve 816 shows depletion savings.

[0109] Assuming that the filament current is held constant at the operating level between pulses, the proposal is to blank and boost between pulses. With regard to "filament wear", the temperature of the filament follows the blank and boost. While this does not seem like much in current, the "wear" savings can be significant, for example, savings of over 20%.

[0110] The term "desired characteristics" relates to characteristics of the radiation beam such as spectrum / spectrum, energy and duration.

[0111] During pulsed operation of an X-ray system, a series of several pulses for imaging is called a run. The pulses have a duration (pulse width) on the order of magnitude of about 10 ms, and often a pulse rate of 15 pulses per second (pps) is used. An X-ray run has a duration of about 10 s to several minutes. For example, with a frame rate of 15 pps and a pulse width of 10 ms, X-rays are generated only during 15% of the time in an imaging run. The scheme of the first and second filament currents in the sequence of pulses supports that the filament needs to be at operating temperature during the 15% of the time. It is proposed to use a procedure to cool the filament as fast as possible immediately after the X-ray pulse and to heat it again as fast as possible at the correct time before the next pulse, just in time to produce the next pulse with the correct X-ray settings. The lower temperature between pulses leads to a significant reduction in tungsten deposition, which results in a significantly longer tube life.

[0112] In one example, a first filament current is provided during a first portion of the pause and a second filament current is provided during a second portion of the pause.

[0113] Optionally, the first portion is greater than the second portion.

[0114] The emission current is a function of, among other things, the temperature of the filament and the voltage between the anode and the cathode. The emission current is a characteristic of the electron beam that is generated between the cathode and the anode when the cathode has a sufficiently high temperature and the voltage between the anode and the cathode is sufficiently high.

[0115] A filament current is supplied to the x-ray tube to generate heat in the cathode filament to reach a desired emission current during an x-ray pulse.

[0116] The emission current is also called the anode current.

[0117] The filament current is also called the cathode (heating) current.

[0118] The first filament current, also called the blanking current, is supplied during the blanking phase.

[0119] A second filament current, also called the boost current, is provided during the boost phase.

[0120] The first filament current is set to provide a minimum supply for operating the X-ray tube electronic components in the idle time between two pulses, but without, or at least substantially without, heating of the filament. In X-ray tubes without such electronic components, or in X-ray tubes where the components are supplied differently, this current is 0 A (no current at all). The desired emission is the next emission to generate the next X-ray pulse.

[0121] In one example, boosting is performed at 5 to 10 A, for example 8 A. This results in a high temperature of the filament.

[0122] In one example of this method, application of a first filament current and a second filament current results in cooling and heating of the filament during each pause.

[0123] Heating is also called boosting. In one example, the current is as high as possible for as short a time as possible.

[0124] In one example, application of the first filament current and the second filament current results in cooling and heating of the filament during each pause compared to a filament where a constant filament current is provided during the pause, the constant filament current being higher than the first filament current and the constant filament current being lower than the second filament current.

[0125] Alternating cooling and heating procedures of the filament are performed in a sequence of pulses, for example a sequence of four pulses, five pulses, six pulses, seven pulses, eight pulses, nine pulses, or ten or more pulses.

[0126] In one example of this method, a first filament current is provided during a first portion of the pause and a second filament current is provided during a second portion of the pause, the first portion being greater than the second portion.

[0127] In one example, the first filament current is supplied during at least 60% of the pause period. For example, the first filament current is supplied during at least 75% of the pause period.

[0128] In one example, the blanking and boosting periods are based on the blank curve and the boost curve. Depending on the situation, this results in different ratios of blanking and boosting periods. In one example, blanking takes longer than boosting. In another example, boosting takes longer than blanking.

[0129] In one example of this method, the duration of the first portion and the duration of the second portion are determined based on a weighted calculation of the results from the boost curve and the results from the blank curve to extract the blank time and boost time for a given pulse pause duration.

[0130] Optionally, the blanking and boosting times are chosen to sum up to be equal to the pulse pause, optionally short with a small safety margin. After the chosen period of blanking and boosting, the filament temperature returns to or near the temperature required to deliver the next pulse, which corresponds to the operating filament current required to maintain this temperature. During the pulse, the operating filament current is optionally provided to drop to the blanking current immediately after the pulse.

[0131] In one example, blanking and boosting between x-ray pulses is performed by automatic determination of the first and second portions.

[0132] The calculation provides the exact point in time to switch from blanking to boosting, i.e. from the first filament current to the second filament current.

[0133] In one example of this method, the blank curve and the boost curve are obtained from a prepared look-up table, and the look-up table is updated based on the detected depletion of the filament or the values ​​obtained from the table are corrected accordingly.

[0134] Correct determination of the point between pulses to switch from blanking to boosting requires significant processing power in the generator controller.

[0135] In one example of this method, the transition from the second filament current to the operating filament current occurs immediately before the next x-ray pulse is generated.

[0136] In one example of this method, a sequence of pulses is provided for a sequence of images, each pulse separated from the preceding / following pulse by an emission pause, and the first filament current and the second filament current are provided consecutively, the sequence of pulses is followed by an idle period, after which a further imaging sequence is provided.

[0137] Optionally, at the start of the idle time, the filament current is set to a blank level equal to the first filament current to allow the temperature to drop to a filament standby temperature corresponding to an equilibrium temperature when the filament is heated by the standby current, and then a standby filament current is supplied during the remainder of the idle time, the standby filament current being higher than the first filament current.

[0138] In one example, four levels of filament current are provided to operate the X-ray tube cathode filament: standby current, boost current, operating current, and blank current. When the X-ray tube is in standby mode (ready for operation but not emitting X-rays), the cathode filament is kept at a temperature that allows rapid heating to the operating temperature but does not lead to thermionic emission when the highest operating voltage is applied between the anode and cathode. In preparation for an X-ray acquisition, the desired settings of the tube voltage and emission current are first determined. From these two values, the set point of the operating filament current (adjusted for filament wear) is determined. The difference between the standby current and the operating current is used to determine how long the maximum current (boost current) needs to be applied to make the filament reach a temperature corresponding to the equilibrium temperature at the operating current. After the boost current has been applied for said period, the filament current switches to the operating current. Typically, during an unregulated run, the filament current remains at the operating level until the last pulse of the run is given. After this final pulse, the filament current is reduced to the blank level for a calculated period of time to cool the filament to a temperature corresponding to the equilibrium temperature of the filament current at the standby level, after which the filament current is switched back to the standby level.

[0139] When an acquisition run consists of two or more x-ray pulses, an intercooler becomes relevant. It works by performing blanking and boosting between the pulses. Usually the pause between two pulses is not long enough to blank to the standby temperature and boost back to the operating temperature, so it is necessary to calculate some point between two pulses to switch from blanking to boosting in order to return to the operating temperature before the next pulse starts. During the pulse the filament current is kept at the operating level, after which the filament current is reduced to the blanking level again.

[0140] If there is a long pause between pulses, it may happen that the pulse pause exceeds the time needed to blank to the standby temperature and boost back up to the operating temperature again. In such a case, it is possible to switch the filament current from the blanking current to the standby current and then boost the current again in time to avoid the temperature dropping below the standby temperature.

[0141] In one example of an X-ray tube, the blank current is not zero because this current is also used to supply the electronics inside the tube. When this is not needed, in one example, the blank current is set to zero, i.e., 0 A.

[0142] Optionally, the blank, boost and standby currents are fixed but adjusted for filament depletion. The operating current is set to obtain the desired emission current at the tube voltage used.

[0143] In one example, the blank current is a first filament current and the boost current is a second filament current.

[0144] The term "approximately equal" refers to a deviation of up to ±25%, such as up to ±10%, of the value of the current. In one example, a deviation of up to ±5% is provided. In a further example, the first idle filament current is equal to the first filament current.

[0145] The acquisition of several images in the form of a sequence with several pulses is also called a run or image run, which is related to X-ray techniques known as pulsed fluoroscopy, cine, or test shot lock-in multiphase.

[0146] In one example of this method, a boost filament current is provided before the sequence of pulses is provided, the heating filament current being equal to the second filament current.

[0147] In one example, the standby current is provided before the image sequence and its preheating begins.

[0148] The duration refers to the blank time of the first filament current and the boost time of the second filament current.

[0149] Note that it is provided to perform boosting and blanking between pulses as well as before and after a run.

[0150] By performing wear calculations based on field data from system usage, it is possible to estimate the reduction in wear per run when blanking and boosting are performed between pulses compared to the situation where the filament heating current is kept constant during the run. A wear reduction of about 35% is achieved. It is also possible to predict the wear reduction. This is true for X-ray systems where a series of pulses is used and wear of the cathode filament is the failure mode.

[0151] In one example (see also FIG. 5), a fluoroscopic imaging run is performed with a frame rate of, for example, 7.5 fps (frames per second). For the tube voltage, values ​​in the range of 90-100 kV are provided, and for the current, values ​​in the range of 100-200 mA, for example 150-160 mA, are provided. As an example, four pulses are provided in the run. As an initial boost, a current between 5-10 A, for example 8 A, is provided for a duration of 150-300 ms, for example 250 ms. The operating current is determined to be 3-8 A, for example 5-6 A, for a duration of 300-500 ms, for example 400 ms. Furthermore, a blank current is provided of 1-2 A, for example 1.5 A, for a duration of 500-1000 ms, for example 800 ms. Between the pulses, blank and boost schemes of two different filament currents are provided. An operating current of 5-6 A, for example 5.4 A, is required. The pause between pulses is set to 100-150 ms, for example 125 ms, with a safety margin of 1-5 ms, for example 3 ms.

[0152] Suitable applications are in X-ray devices, i.e. X-ray tubes and X-ray generators, where X-ray radiation is generated in a pulsed mode rather than in a continuous mode. A further suitable application relates to X-ray devices, where the adaptation table is kept continuously up to date.

[0153] In the example of a fixed system, the pulse width (duration of the pulse) is about 7 ms. A pulse rate of 15 pulses per second (pps) is used, but 7.5 pps is also possible, which makes this application of blank and boost between pulses even more beneficial. With 15 pps and a 7 ms pulse width, for every second in the run, only 15 x 7 = 105 ms is filled with x-rays, which is about 10% of a second. The pulse tact is 1 / 15, or about 67 ms. In this time frame, there is a 7 ms pulse, leaving 60 ms for blank and boost to reduce filament temperature and associated wear.

[0154] The blank and boost curves (represented by the blank and boost tables) are not symmetrical and are estimated using a fourth order polynomial. Using the processing capabilities of the X-ray generator, a fictitious filament heating current is found that falls along the blank curve and rises along the boost curve within the available time (in this case 60 ms) such that the operational filament heating current is reached again. At this point, the X-ray generator should switch from blanking to boosting and be back at the temperature required during the pulse in which the operational filament heating current is applied. If the pause between pulses is long enough that the fictitious filament heating current falls below the standby current, blanking is stopped and the standby current is applied until it is time to start boosting again.

[0155] The system needs to be able to control the use of this algorithm because it is advantageous to be able to switch it off, for example, when a variable pulse rate is used (e.g., when the pulses are synchronized with the patient's heart rate) or if the set point is not yet stable.

[0156] In one example, the system generator interface is provided with a general switching on / off command to fully enable or disable the generator intercooler as a safety measure to switch the generator intercooler completely off in case of an unexpected problem.

[0157] In another example, for each run, the EPX used (a cluster of settings that optimizes the system for the procedure of which the X-ray run is a part) decides whether the intercooler should be used or not. For example, if the X-ray pulse is synchronized with an external source, it is better to switch the intercooler off. This setting is ignored if the mechanism is normally switched off.

[0158] When the desired set point is reached, the generator indicators show regulation has settled, and both the general intercooler switch and the EPX associated intercooler switch are on, the intercooler will operate.

[0159] In one example, a computer program or program element for controlling an apparatus according to one of the above-mentioned examples is provided, which program or program element is adapted to perform the method steps of one of the above-mentioned method examples when executed by a processing unit.

[0160] In another exemplary embodiment of the invention, a computer program or a computer program element is provided, characterized in that it is adapted to execute, on a suitable system, the method steps with respect to the method according to one of the previous embodiments.

[0161] Hence, a computer program element is stored in a computing unit or distributed across two or more computing units, which is also part of an embodiment of the present invention. This computing unit is adapted to execute or direct the execution of the steps of the above-mentioned method. Moreover, it is adapted to operate the components of the above-mentioned apparatus. The computing unit is adapted to operate automatically and / or to execute user instructions. The computer program is loaded into the working memory of a data processor. The data processor is thereby equipped to execute the method of the present invention.

[0162] Aspects of the invention are embodied in a computer program product, which is a collection of computer program instructions stored on a computer-readable storage device that can be executed by a computer. The instructions of the invention may be any interpretable or executable code mechanism, including, but not limited to, a script, an interpretable program, a dynamic link library (DLL), or a Java class. The instructions may be provided as a complete executable program, a partial executable program, as a modification (e.g., an update) to an existing program, or as an extension (e.g., a plug-in) to an existing program. Moreover, parts of the processing of the invention may be distributed across multiple computers or processors.

[0163] As discussed above, a processing unit, e.g., a controller, implements the control method. The controller can be implemented in numerous ways using software and / or hardware to perform the various functions required. A processor is one example of a controller that uses one or more microprocessors that are programmed using software (e.g., microcode) to perform the functions required. However, a controller can be implemented with or without the use of a processor, as well as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions.

[0164] Examples of controller components used in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field programmable gate arrays (FPGAs).

[0165] This exemplary embodiment of the invention covers both computer programs that use the invention from the beginning and computer programs that, through updates, turn existing programs into programs that use the invention.

[0166] Furthermore, the computer program element may provide all the necessary steps to fulfill the procedures of the exemplary embodiments of the methods described above.

[0167] According to a further exemplary embodiment of the present invention, a computer readable medium, such as a CD-ROM, is presented, having stored thereon a computer program element, the computer program element being as described in the previous section. The computer program may be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless communication systems.

[0168] However, the computer program may also be presented over a network such as the World Wide Web and downloaded from such a network into the working memory of a data processor. According to a further exemplary embodiment of the invention, a medium for making a computer program element downloadable is provided, the computer program element being configured to perform a method according to one of the previously described embodiments of the invention.

[0169] It should be noted that the embodiments of the present invention are described with reference to different subject matters. In particular, some embodiments are described with reference to method type claims, while other embodiments are described with reference to apparatus type claims. However, those skilled in the art will understand from the above and following description that, unless otherwise indicated, any combination of features belonging to one type of subject matter, as well as any combination between features relating to different subject matters, is considered to be disclosed by the present application. However, all features can be combined to provide synergistic effects that go beyond the simple sum of the features.

[0170] While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the dependent claims.

[0171] In the claims, the words "comprise, include, have" do not exclude other elements or steps, and the words "a" or "an" do not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be interpreted as limiting the scope.

Claims

1. 1. A control device for the pulsed operation of a generator for an X-ray tube, said control device comprising: A data input unit; Controller and Including, the data input providing a signal for an x-ray imaging run including a plurality of x-ray pulses for acquiring at least one x-ray image; the controller controls the generator to provide a filament current to generate heat in a filament of a cathode of the X-ray tube to reach a desired emission current during an X-ray pulse; the generator provides the plurality of X-ray pulses, whereby each two consecutive X-ray pulses of the plurality of X-ray pulses are separated in time by an emission pause, the emission pause including at least a first portion and a second portion; a control device, wherein the controller adjusts the filament current in the emission pause between the two consecutive pulses, thereby supplying a first filament current in the first portion of the pause and a second filament current in the second portion of the pause, the first filament current being lower than the second filament current.

2. 2. The control device of claim 1, wherein the controller provides the filament current at an operating level during an x-ray pulse, the first filament current being lower than the operating level and the second filament current being higher than the operating level.

3. 2. The control device of claim 1, wherein the controller controls the generator such that the first filament current and the second filament current result are repeatedly applied during at least a portion of the emission pause between successive pulses of the plurality of x-ray pulses.

4. 2. The control device of claim 1, wherein the duration of the first portion and the duration of the second portion are determined based on a weighted calculation of results from a boost curve and a blank curve to derive blank and boost times for a given pulse pause duration while controlling the generator to still reach the operating filament temperature during the pulse.

5. The control device of claim 1 , wherein the controller controls the generator such that the blank curve and the boost curve are interpolated from a look-up table.

6. the look-up table is updated based on the detected depletion of the filament; and / or The control device of claim 5 , wherein the results from the lookup table are corrected for the detected depletion of the filament.

7. 2. The control device of claim 1, wherein the controller controls the generator to supply a plurality of voltage pulses corresponding to the X-ray pulses to generate the electron beam having the desired emission current for generating the X-ray pulses.

8. 2. The control device of claim 1, wherein the controller controls the generator such that an operating filament current is supplied during the pulse after the second filament current.

9. the controller controls the generator to supply a heating filament current before the sequence of pulses is supplied; The control device of claim 1 , wherein the heating filament current is equal to the second filament current.

10. 2. The control device of claim 1, wherein the controller controls the generator such that a filament current during the first portion of the pause is sufficient to define a predetermined minimum filament current to be maintained as an effective current throughout the pause.

11. 1. A generator for a pulsed voltage supply of an X-ray tube, said generator comprising: A control device according to any one of claims 1 to 10; a power input; an electrical transformer device; Power output section and Including, the power input is connectable to a power source for providing input in the form of electrical energy for operating the X-ray tube, the power source being connected to the electrical transformer arrangement; the electrical transformer device converts the electrical input into a suitable DC high voltage and a suitable current for pulsed operation of the x-ray tube; the power output provides the appropriate high voltage and the appropriate current; the power output is connectable to the X-ray tube; A generator wherein the control device controls generator components.

12. an x-ray tube for generating x-ray radiation; A generator according to claim 11; 1. An X-ray imaging system comprising: the X-ray tube includes an anode and a cathode; the cathode includes at least one cathode filament for emitting at least one electron beam toward the anode; An x-ray imaging system wherein the control device controls the pulsing of the cathode filament by controlling an electrical transformer arrangement of the generator.

13. 1. A method for operating an x-ray tube generator in a pulsed manner, comprising: providing a signal for an x-ray imaging run including a plurality of x-ray pulses for acquiring at least one x-ray image; providing a filament current to generate heat in a cathode filament of the x-ray tube to reach a desired emission current during an x-ray pulse; generating an electron beam having a desired emission current directed from the cathode of the X-ray tube to the anode under the influence of a voltage between the anode and the cathode to generate the plurality of X-ray pulses with desired characteristics; and To supply the filament current: providing a plurality of pulses to generate the electron beam having the desired emission current to generate the plurality of X-ray pulses, wherein each two consecutive X-ray pulses of the plurality of X-ray pulses are separated in time by an emission pause, the emission pause including at least a first portion and a second portion; adjusting the filament current during the emission pause between the two consecutive pulses, thereby providing a first filament current during the first portion of the pause and a second filament current during the second portion of the pause; was carried out, The method, wherein the first filament current is lower than the second filament current.

14. A computer program product enabling a processor to carry out the method according to claim 13.

15. A computer readable medium having stored thereon the computer program of claim 14.

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