High-speed kVp switching using nonlinear inductance and resonant operation

Abstract

The present invention relates to a system and method for high voltage switching in a computed tomography system. The system includes an oscillator circuit having a nonlinear inductor and a capacitor. The inductor and capacitor are connected in series, and the capacitor is connected to a high voltage line of a high voltage power supply. The inductor has an inductance that decreases with increasing current through the inductor, so that the inductance of the inductor changes significantly during resonant operation of the oscillator circuit, thereby essentially providing a square voltage that is applied to the capacitor. The square voltage modulates the high voltage of a high voltage generator, thereby switching the high voltage level applied to the electrodes of the computed tomography system.

Description

Technical Field

[0001] The present invention relates to a system for high-voltage switching of a computed tomography apparatus, a computed tomography apparatus including the system for high-voltage switching, and a method for high-voltage switching of a computed tomography apparatus.

Background Art

[0002] Spectral imaging appears to be becoming mainstream in X-ray computed tomography (CT). In spectral imaging, X-ray images of an object are acquired at at least two different peak energies of X-ray radiation. This is achieved by rapidly switching the high-voltage potential applied to the X-ray tube of a computed tomography apparatus. Switching of the peak high voltage (kVp) is an easy way to implement a spectral function at low cost and provides efficient spectral imaging for all patients. Ultra-high-speed kVp switching is the simplest and most cost-effective means of spectral CT and has the potential for even better image quality than dual-layer detectors. Ultra-high-speed switching, when properly implemented, maintains the applicant's claim of "spectral always on". Several ways of implementing electronic devices to support ultra-high-speed kVp switching are known. However, many of these have some drawbacks such as high cost or low fault tolerance. Therefore, a very cost-effective and robust solution for all possible fault conditions such as tube arc discharge is needed.

[0003] Therefore, the inventors of the present invention have found it advantageous to have a system and method for high-voltage switching of a computed tomography apparatus that provides highly reliable and cost-effective high-voltage switching.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The object of the present invention is to provide a system and method for high-voltage switching of computed tomography (CT) scanners that provides highly reliable and cost-effective high-voltage switching and reduces stress on the electrodes of the CT scanner. [Means for solving the problem]

[0005] The object of the present invention is solved by the subject matter of the independent claims, and further embodiments are incorporated into the dependent claims. The embodiments described similarly include a system for high-voltage switching of a computed tomography apparatus, a computed tomography apparatus including a system for high-voltage switching, and a method for high-voltage switching of a computed tomography apparatus. Synergistic effects may arise from various combinations of embodiments, but these are not described in detail.

[0006] Furthermore, while all embodiments of the present invention concerning methods may be performed in the order of steps described, it should be noted that this is not the only required order of steps in the methods. The methods presented herein may be performed in a different order of steps disclosed without departing from the respective embodiments of the methods unless expressly referred to below to the contrary.

[0007] According to a first aspect of the present invention, a system for high-voltage switching of a computed tomography apparatus is provided. The system includes a high-voltage generator, an inductor having nonlinear inductance, and a capacitor. A first connection terminal of the capacitor is communicatively connected to the high-voltage generator, and a second connection terminal of the capacitor is communicatively connected to the first connection terminal of the inductor to use the resonant operation of the current through the inductor. The inductor is configured to produce a reduction in nonlinear inductance as the current through the inductor increases, and the inductor is configured to produce a reduction in nonlinear inductance at a predefined current level of current through the inductor that is below the maximum current of the resonant operation.

[0008] The proposed system uses a resonant circuit connected to the high-voltage output of a high-voltage generator. The resonant circuit includes a capacitor and an inductor connected in series, thereby enabling resonant operation. One connector of the capacitor is connected to the high-voltage output, and the other connector is connected to the first side of the inductor. The second side of the inductor is connected to ground or to another output of the high-voltage generator. Communicative connection must be understood as establishing a conductive connection between each element. The resonant operation of the circuit results in a current flowing through the inductor, maintained by the inductance L of the inductor, thereby charging the capacitor. At maximum charge of the capacitor, the direction of the current flowing through the inductor changes, and the capacitor is discharged. When an inductor with constant invariant inductance is used, the sinusoidal shape of the current through the inductor and the voltage in the capacitor are supplied, respectively. However, spectral imaging applications may require a square-shaped voltage rather than a sinusoidal voltage. In this application, the square-shaped voltage waveform is achieved by using a nonlinear inductor rather than by using a switch in the resonator. The nonlinear inductor provides inductance that depends on the current flowing through the inductor. At low current values ​​below a predefined current level, and therefore at high capacitor charges, a high inductance in the inductor limits the current, preferably to less than 500 mA. This relatively low current keeps the capacitor charge essentially constant and, therefore, the capacitor voltage level nearly constant. However, if the current through the inductor increases beyond the predefined current level, the inductor is automatically configured to significantly reduce its inductance. Preferably, the inductance is reduced to at least 1 / 100th. However, a small inductance must remain to maintain resonant operation. This steeply decreasing inductance preferably allows for a rapid increase in current up to several tens of amperes, thereby resulting in rapid discharge and rapid recharging of the capacitor in the opposite direction.When the resonant current drops below a predefined current level, the inductor is configured to automatically recover its high inductance and again limit the current to preferably less than 500mA, thereby keeping the capacitor voltage nearly constant at different voltage levels. Therefore, the system of the present invention supplies a square-shaped voltage applied to the capacitor, achieved by using the resonant operation due to the nonlinear inductance of the inductor.

[0009] In one embodiment of the present invention, the inductor includes a magnetic core configured to magnetically saturate at a predefined current level.

[0010] An inductor contains a magnetic core that saturates at a low magnetic field strength. Many materials are suitable for this task, and in particular, single-crystal or amorphous soft magnetic alloys are used. When a magnetic core that saturates at a given magnetic field strength is provided in an inductor, the inductance of the inductor decreases as the magnetic core reaches saturation. The magnetic field that causes the magnetic core to saturate is caused by the current flowing through the inductor.

[0011] In one embodiment of the present invention, an inductor is configured to provide a first inductance when the current through the inductor is below a predefined current level, and to provide a second inductance when the current through the inductor is above a predefined current level, wherein the second inductance is at least 1 / 100th of the first inductance.

[0012] When the inductance of an inductor drops sharply near a predefined current level, different values ​​of inductance are obtained for inductance below and above the predefined current level, respectively. The ratio of the first inductance to the second inductance is at least about 100 in this embodiment of the invention, and can be 10000 or greater. However, the dependence of inductance on current is a continuous function. In addition, the inductance also includes slight variations when the current through the inductor is clearly below or clearly above the predefined current level. Thus, the first inductance is interpreted as the average value of the inductance when the current is sufficiently small compared to the predefined current level, and the second inductance is interpreted as the average value of the inductance when the current is sufficiently large compared to the predefined current level.

[0013] In one embodiment of the present invention, the system is configured to supply a voltage to be applied to a capacitor that is essentially constant at a first voltage level or a second voltage level when the current through the inductor falls below a predefined current level during resonant operation, and when the current through the inductor exceeds a predefined current level, the voltage applied to the capacitor rapidly changes from the first voltage level to the second voltage level, or from the second voltage level to the first voltage level.

[0014] The voltage applied to the capacitor rapidly changes its voltage level from a first voltage level to a second voltage level, and vice versa, when the inductance is low. For a certain period, the inductance of the inductor is high, and as a result, the current through the inductor is below a predefined current level, and the voltage across the capacitor remains approximately constant at either the first or second voltage level. Thus, a voltage flat region is provided.

[0015] In one embodiment of the present invention, the voltage applied to the capacitor is essentially a square voltage.

[0016] These flat regions of voltage applied to the capacitor at two different voltage levels, along with abrupt transitions from one voltage level to the other at very short time intervals, result in a square voltage. The square voltage has the advantage that the voltage remains constant for most of the time, allowing the computed tomography (CT) system to acquire data for most of the time. Because the transition from one voltage level to another is smooth and continuous due to the nonlinear inductance, the proportion of high-frequency current applied to the X-ray tube during high-voltage switching is low. This reduces stress on the X-ray tube and increases the reliability of the CT system's operation.

[0017] In one embodiment of the present invention, the inductor is configured to provide a nonlinear inductance such that a first dependence of the inductance on a current in a first direction through the inductor is different from a second dependence of the inductance on a current in a second direction through the inductor, where the first direction is opposite to the second direction, and / or the system is configured to supply a voltage applied to a capacitor which is essentially an asymmetric square voltage.

[0018] To use a duty cycle that suits the needs of computed tomography (CT) scanners, a square-shaped voltage with an asymmetric waveform is required. In an asymmetric waveform, the time the voltage is at a first voltage level differs from the time the voltage is at a second voltage level. This is achieved by providing an inductor with nonlinear inductance and different behavior in the positive and negative current directions. For example, the inductor is configured to provide separate predefined current levels in each current direction, where the first predefined current level differs from the second predefined current level. Alternatively, the inductor is configured to provide a first inductance and / or a second inductance of different values ​​in the positive and negative current directions, respectively.

[0019] In one embodiment of the present invention, the inductor includes a first inductor having a nonlinear inductance, a second inductor having a nonlinear inductance and connected in series with the first inductor, and a diode that functions as a rectifier and / or is configured to be connected in parallel with the first inductor or the second inductor.

[0020] To obtain the correct duty cycle, the diode is used to operate at least one of at least two inductors in only one current direction. In this embodiment of the present invention, the effective inductance of an inductor including a first inductor and a second inductor connected in series changes in one current direction when one of the inductors is short-circuited by the diode.

[0021] In one embodiment of the present invention, the system includes a bias device configured to expose an inductor to an external magnetic field, or the system includes a bias circuit configured to generate a DC bias current through the inductor.

[0022] Alternatively, core saturation may be modulated by a switching current source acting on an additional winding of the nonlinear inductor. By biasing the inductor with an external magnetic field, saturation of the inductor, specifically the inductor core, is achieved at different current levels through the inductor. Since this external magnetic field does not change direction with changes in the direction of current through the inductor, the sum of the external magnetic field and the magnetic field produced by the current through the inductor is different for the first and second current directions, respectively. Thus, the predefined current levels differ for the positive and negative current directions. Alternatively, the system may include a bias circuit configured to produce a DC current through the inductor, which is summed with the AC current of the resonant operation through the inductor. Thus, the resulting current through the inductor differs for the first and second current directions, thereby resulting in different behavior of the inductance due to the current of the resonant operation in the positive and negative current directions, respectively. Thus, the DC current is supplied by an amplifier connected to a relatively large linear inductor, which ensures a current through a bias circuit with an amplitude that does not change significantly over one period of resonant operation.

[0023] In one embodiment of the present invention, the system includes a tuning mechanism configured to adjust the resonant frequency of the resonant operation.

[0024] To synchronize high-voltage switching with the rotation speed of the X-ray tube of a computed tomography (CT) scanner, the system must be configured to provide an adjustable resonant frequency. This is ensured by an adjustment mechanism configured to provide an opportunity to adjust at least one of the inductance of an inductor and the capacitance of a capacitor.

[0025] In one embodiment of the present invention, the adjustment mechanism includes at least one of a switchable capacitor, an adjustable capacitor, a switchable inductor, or an adjustable inductor.

[0026] To use the adjustment mechanism, the system comprises an adjustable or switchable capacitor configured to adjust the capacitance of the capacitor. Additionally or alternatively, the system comprises an adjustable or switchable inductor configured to adjust the inductance of the inductor. In this way, the resonant frequency of the resonant operation is adapted to the specific needs of the computed tomography apparatus.

[0027] In one embodiment of the invention, the inductor includes a first inductor having a non-linear inductance and a second inductor having a non-linear inductance and connected in series with the first inductor, and the system includes a first control inductor inductively coupled to the first inductor and a second control inductor inductively coupled to the second inductor, and the system is configured to supply a first control current to the first control inductor and a second control current to the second control inductor, and the first control current has the same number of amperes as the second control current but in the opposite direction.

[0028] In this embodiment of the invention, the adjustment of the resonant frequency of the resonant operation is achieved by affecting the value of a predefined current level of the inductor. The inductor is separated into a first inductor and a second inductor connected in series. Each of the first inductor and the second inductor comprises a respective control inductor inductively coupled to the first inductor and the second inductor, respectively. By supplying an adjustable current having the same magnitude but opposite current directions through the first control inductor and the second control inductor, respectively, the resonant frequency is adjusted. The opposite current directions in the control inductors provide good decoupling and symmetric behavior of the circuit in both current directions of the resonant operation. Thereby, the influence on the resonant operation is effected by either a direct current through the first and second control inductors or an alternating current having the same frequency as the resonant frequency of the resonant operation.

[0029] In one embodiment of the present invention, the system includes a drive mechanism configured to excite a resonant operation.

[0030] An external input is required to excite and drive the resonant operation of the current passing through the inductor. When the drive mechanism is controlled at the resonant frequency, this external input supplies energy to excite the current and maintain the resonant operation.

[0031] In one embodiment of the present invention, the drive mechanism includes the switching of a high-voltage generator, or the drive mechanism includes an amplifier inductively coupled to the inductor, or an amplifier capacitively coupled to a capacitor.

[0032] To excite and drive the resonant operation of the system, the oscillation of the high voltage of the high-voltage generator can be used. However, this is very inconvenient. Therefore, in this embodiment of the present invention, a drive mechanism included in the system is provided. This drive mechanism includes an amplifier for generating an alternating current. The drive mechanism is inductively coupled to the inductor, or at least to the first or second inductor of the inductor. Therefore, when the frequency of the drive mechanism is appropriately adjusted, the alternating current of the drive mechanism induces an alternating current of the resonant operation through the inductor of the system. However, the drive mechanism may also be coupled to the system resistively at various power supply points or inductively by using a dedicated transformer. This amplifier is also used to adjust the resonant frequency to an accurate desired value.

[0033] In one embodiment of the present invention, the system further includes a smoothing inductor, and the first connection terminal of the capacitor is connected to the high-voltage output of the high-voltage generator via the smoothing inductor.

[0034] This additional inductor after the high-voltage source smooths the current supplied by the high-voltage source and consumed by the X-ray tube by limiting the current's variation. The resonator current needs to charge the entire system and the intrinsic capacitance of the computed tomography apparatus during each cycle; therefore, this smoothing inductor reduces the capacitance observed by the resonator, making the voltage curve more predictable and easing the system's designed power handling capabilities.

[0035] According to another aspect of the present invention, a computed tomography apparatus is provided which includes a system according to any of the embodiments described above.

[0036] A computed tomography (CT) scanner includes a system comprising a nonlinear inductor, a capacitor, and a high-voltage generator. In addition, the CT scanner includes an X-ray tube with electrodes, and the high-voltage output of the high-voltage generator, and therefore the first connection terminal of the capacitor, is connected to the electrodes. The resonant operation of the system causes charging and discharging of the capacitor connected to the electrodes. Thus, the charging current of the capacitor is used to charge and discharge the intrinsic capacitance of the computed tomography scanner, such as the capacitance of the electrodes, cables, or the high-voltage generator. Therefore, the square voltage supplied by the system is superimposed with the high voltage supplied by the high-voltage generator, and the high voltage applied to the electrodes of the X-ray tube is switched between two different high-voltage levels. Furthermore, the computed tomography scanner or system includes a processing unit configured to control the switching of the high voltage by manipulating the resonant operation.

[0037] According to another aspect of the present invention, a method for high-voltage switching of a computed tomography apparatus is provided. This method comprises the steps of preparing a computed tomography apparatus according to the above-mentioned aspect of the present invention, driving a current through an inductor to excite a resonant action, and switching a high voltage applied to the electrodes of the X-ray tube of the computed tomography apparatus.

[0038] In the first step of this method, a computed tomography apparatus is prepared. This apparatus includes an X-ray tube and a system according to one of the embodiments described above. In the second step, a current through a nonlinear inductor of the system is excited and driven at the system's resonant frequency. This essentially applies a square voltage to the capacitor, resulting in high-voltage switching of the voltage applied to the electrodes of the X-ray tube of the computed tomography apparatus.

[0039] According to another aspect of the present invention, a computer program element is provided which, when executed by a processing unit, instructs the processing unit to perform a method comprising the steps of driving a current through an inductor of a system according to any of the above embodiments, thereby exciting a resonant action and switching a high voltage applied to the electrodes of an X-ray tube of a computed tomography apparatus.

[0040] The computer program elements are executed in one or more processing units that are instructed to perform methods for high-voltage switching of a computed tomography (CT) scanner.

[0041] Preferably, the elements of the program are stored in a computed tomography apparatus that includes a system for high-voltage switching, and a processing unit that executes the elements of this program is part of the apparatus.

[0042] A computer program element may be part of a computer program, or it may be an entire program in itself. For example, a computer program element may be used to update an existing computer program in order to carry out the present invention.

[0043] Computer program elements are stored on computer-readable media. Computer-readable media can be considered storage media such as USB sticks, CDs, DVDs, data storage devices, hard disks, or any other media on which the aforementioned program elements are stored.

[0044] According to another aspect of the present invention, a processing unit is provided which is configured to execute the computer program elements according to the above-described embodiment.

[0045] The processing unit may be distributed across one or more different devices that execute the computer program elements according to the present invention. Thereafter, the advantages provided by any of the above embodiments apply equally to all of the other embodiments, and vice versa.

[0046] In short, the present invention relates to a system and method for high-voltage switching of a computed tomography (CT) system. The system includes an oscillator circuit having a nonlinear inductor and a capacitor. The inductor and capacitor are connected in series, and the capacitor is connected to a high-voltage line of a high-voltage power supply. The inductor has an inductance that decreases with increasing current through the inductor, and as a result, the inductance of the inductor changes significantly during the resonant operation of the oscillator circuit, thereby supplying a square voltage that is essentially applied to the capacitor. The square voltage modulates the high voltage of a high-voltage generator, thereby switching the high-voltage level applied to the electrodes of the X-ray tube of the computed tomography system.

[0047] The above-described aspects and embodiments will become apparent from the exemplary embodiments described below and will be explained by referring to the exemplary embodiments described below. Exemplary embodiments of the present invention will be described below with reference to the following drawings. [Brief explanation of the drawing]

[0048] [Figure 1] This figure shows a schematic setup of a system for high-voltage switching in a computed tomography apparatus according to a first embodiment of the present invention. [Figure 2A] This figure shows a graph of the square voltage applied to the capacitor over time. [Figure 2B] This figure shows a graph of the asymmetrical square voltage applied to the capacitor over time. [Figure 3] This figure shows a graph of the inductance of a nonlinear inductor with respect to the current flowing through it. [Figure 4] This figure shows a schematic setup of a system for high-voltage switching in a computed tomography apparatus according to a second embodiment of the present invention. [Figure 5] This figure shows a schematic setup of a system for high-voltage switching in a computed tomography apparatus according to a third embodiment of the present invention. [Figure 6] This figure shows a schematic setup of a system for high-voltage switching in a computed tomography apparatus according to a fourth embodiment of the present invention. [Figure 7] This figure shows a schematic setup of a system for high-voltage switching in a computed tomography apparatus according to a fifth embodiment of the present invention. [Figure 8] This figure shows a schematic setup of the computed tomography apparatus according to the present invention. [Figure 9] This is a block diagram of a method for high-voltage switching of a computed tomography apparatus according to the present invention. [Modes for carrying out the invention]

[0049] Figure 1 shows a schematic setup of a system 100 for high-voltage switching of a computed tomography apparatus 200 according to a first embodiment of the present invention. Described from left to right, the components are an X-ray tube 210 with electrodes 220, a capacitor 195 to ground, and all capacitances in the generator, cables, etc. A high-voltage generator 110 with a high-voltage outlet 111 is shown on the right side of the image. The system includes an LC series circuit shown in the figure, which includes a capacitor 130 and an inductor 120. The capacitor 130 has a first connection terminal 131 and a second connection terminal 132. The inductor 120 has a first connection terminal 121 and a second connection terminal 122. In the resonant operation of the system, current 140 flows through the LC circuit, and in particular through the inductor 120, which is a nonlinear inductor. The inductance is highly nonlinear. This means that the inductor 120 has a magnetic core that saturates with a current of 500 mA or less passing through it. The relative permeability of the magnetic core material is approximately 10,000 or higher. This means that the time when the current amplitude is below the saturation level of the magnetic core is very long compared to the time when the current is above the saturation level of the magnetic core (high current). The time for low current below a given current level 145 is a constant voltage region of voltage 150 across capacitor 130, while at high currents, the voltage changes rapidly from one constant voltage region 151 to the other constant voltage region 152. In simple cases, oscillation of current 140 is initiated using a voltage swing by a high-voltage generator 110.

[0050] Figure 2A shows a graph of the square voltage applied to the capacitor 130 over time. The voltage applied to the capacitor 130 switches between a first voltage level 151 and a second voltage level 152. Switching occurs when the current 140 flowing through the inductor exceeds a predetermined current level 145.

[0051] Figure 2B shows a graph of the asymmetric square voltage applied to the capacitor over time. The voltage applied to the capacitor 130 switches between a first voltage level 151 and a second voltage level 152. In this figure, the time that voltage 150 is at the second voltage level 152 is approximately twice the time that voltage 150 is at the first voltage level 151. Therefore, if the time for switching voltage 150 is controlled, for example, by the asymmetric behavior of the nonlinear inductor 120, the duty cycle of system 100 is adjusted.

[0052] Figure 3 shows a graph of the inductance of a nonlinear inductor 120 with respect to a current 140 flowing through the inductor 120. When the current 140 is less than a predefined current level 145, the inductance L is at the level of the first inductance 123. When the current 140 is greater than the predefined current level 145, the inductance L of the inductor 120 decreases rapidly and is at the level of the second inductance 124. The ratio of the first inductance 123 to the second inductance 124 is greater than 100, or, in a preferred embodiment, even greater than 10000.

[0053] Figure 4 shows a schematic setup of system 100 for high-voltage switching of computed tomography apparatus 200 according to a second embodiment of the present invention. Since the embodiment of the present invention shown in Figure 1 provides only symmetrical voltage swing, which may not be optimal with respect to the signal-to-noise ratio, one possible solution to this problem is shown in Figure 4. Compared with Figure 1, in this embodiment of the present invention, the inductor 120 is subdivided into a first inductor 126 and a second inductor 127, which are connected in series with each other. A diode 161 is connected in parallel with the first inductor 126 and configured to short-circuit the first inductor 126 only in one current direction of the current 140. The nonlinear inductor is divided into two sections, at least one of which is bridged by at least one diode. This has the effect of increasing the inductance and the time of constant voltage in one direction of current flow. The voltage-time dependence derived from this embodiment is shown in Figure 2B.

[0054] Figure 5 shows a schematic setup of a system 100 for high-voltage switching of a computed tomography apparatus 200 according to a third embodiment of the present invention. Since it is very inconvenient to excite the oscillation using a high-voltage generator, a dedicated amplifier for generating the oscillation voltage is added. In this embodiment of the present invention, the amplifier 181 is inductively coupled to the resonator, but other coupling modes (capacitive, resistive at various feed points, inductive but using a dedicated transformer, etc.) may also be used. The dedicated amplifier 181 may be used in all embodiments of the present invention. In this embodiment of the present invention, an additional drive mechanism 180 including the amplifier 181 is shown. The amplifier 181 drives an alternating current through the inductor of the drive mechanism 180 which is inductively coupled to at least one of the inductors of the inductor 120. Thus, the resonant operation current 140 is excited and driven through the inductor 120. However, in this embodiment of the present invention, this amplifier 181 inductively coupled to the inductor 120 is also used as a bias device 162 to affect the saturation level of the magnetic core of the inductor 120. Therefore, amplifier 181 is used to adjust the frequency of resonant operation to a precise desired value.

[0055] Figure 6 shows a schematic setup of system 100 for high-voltage switching of computed tomography apparatus 200 according to a fourth embodiment of the present invention. Since the computed tomography apparatus 200 has several rotational speeds, the frequency of resonant operation also requires a coarse adjustment method to change the frequency by more than a doubling, for example. This figure shows one embodiment in which the capacitance of capacitor 130 of the resonant circuit is adjusted by a suitable switch. Other places where capacitance and inductance are switched or otherwise changed are also possible. The switching can have more stages than shown in the drawing, thereby allowing for more precise frequency adjustment. When the rotation of the X-ray tube is slow, it is always possible to have more than two voltage swings per view, so adjustment over a range wider than about two is not necessary. However, it is technically possible to increase the frequency swing. In this embodiment, capacitor 130 is divided into two subcapacitors connected in parallel. One of the parallel branches includes a switch 170 connected in series with each capacitor. Thus, by opening and closing the switch, the capacitance of capacitor 130 is switched between two values. If both subcapacitors have the same capacitance, the capacitance of capacitor 130 doubles when switch 170 is closed.

[0056] Figure 7 shows a schematic setup of system 100 for high-voltage switching of computed tomography apparatus 200 according to a fifth embodiment of the present invention. In this embodiment, different techniques for steering the resonant operation of system 100 are shown. A high-power amplifier 181 is used to change the saturation level of inductor 120 in the resonant path. This means that the inductance of inductor 120 is changed, and therefore the time for which the voltage is constant is changed. In the figure, the resonant current field of inductor 120 and the steering current fields of the first control inductor 171 and second control inductor 172 of the adjustment mechanism 170 are collinear, and decoupling is achieved by splitting inductor 120 into two and driving each of the first inductor 126 and the second inductor 126 with currents in opposite directions. However, decoupling is better if the magnetic material forms a toroidal structure and the main winding and steering winding are formed to magnetize the core material in a direction perpendicular to it. Naturally, the amplifier 181 needs to modulate the current through kVp cycles to achieve the desired effect. In Figure 7, an additional smoothing inductor 190 is shown after the high-voltage generator 110. This smoothing inductor 190 makes the voltage curve more predictable, reduces the capacitance observed by the resonator, and thus mitigates the designed power handling function.

[0057] Figure 8 shows a schematic setup of the computed tomography apparatus 200 according to the present invention. The computed tomography apparatus 200 includes an X-ray tube 210 having electrodes 220 and a system 100 according to any of the above-described embodiments of the present invention. The computed tomography apparatus 200 further includes a processing unit 230 configured to control the high-voltage switching of the system 100.

[0058] Figure 9 is a block diagram of a method for high-voltage switching of a computed tomography apparatus 200 according to the present invention. The method comprises a first step of preparing the computed tomography apparatus 200 and a second step of driving a current 140 through an inductor 120, thereby exciting a resonant action and switching the high voltage applied to the electrode 220 of the X-ray tube 210 of the computed tomography apparatus 200.

[0059] Although the present invention is illustrated and described in detail in the drawings and the foregoing description, such illustrations and descriptions should be considered illustrative or illustrative and not limiting. The present invention is not limited to the disclosed embodiments. Other modifications to the disclosed embodiments can be understood and achieved by those skilled in the art from examining the drawings, disclosure and dependent claims in practicing the claimed invention.

[0060] In the claims, the words “equipment, include, and have” do not exclude other elements or steps, and the singular form does not exclude the plural. The mere fact that certain means are enumerated in different dependent claims does not indicate that combinations of these means cannot be used advantageously. No reference numeral in the claims should be construed as limiting the scope. [Explanation of symbols]

[0061] 100 Systems 110 High-voltage generator 111 High Voltage Output 120 Inductor 121 First connection terminal of the inductor 122 Second connection terminal of the inductor 123 First Inductance 124 Second Inductance 126 First Inductor 127 Second Inductor 130 Capacitors 131 Capacitor's first connection terminal 132 Capacitor's second connection terminal 140 Current passing through an inductor 145 Predefined current levels 150 Capacitor voltage 151 First voltage level 152 Second voltage level 161 Diode 162 Bias Devices 170 Adjustment mechanism 171 First control inductor 172 Second control inductor 180 Drive mechanism 181 Amplifier 190 Smoothing Inductor 195 Intrinsic Capacitance 200 Computed Tomography Scanning Equipment 210 X-ray tube 220 electrode 230 processing units

Claims

1. A system for high-voltage switching of a computed tomography scanner, wherein the system is High voltage generator, An inductor having nonlinear inductance, Capacitor and Includes, The first connection terminal of the capacitor is electrically connected to the high-voltage generator. The second connection terminal of the capacitor is electrically connected to the first connection terminal of the inductor in order to utilize the resonant behavior of the current passing through the inductor. The inductor causes a reduction in the nonlinear inductance as the current passing through the inductor increases. A system in which the inductor reduces the nonlinear inductance at a predefined current level of the current passing through the inductor that is below the maximum value of the current during the resonant operation.

2. The system according to claim 1, wherein the inductor includes a magnetic core that magnetically saturates at the predefined current level.

3. The inductor provides a first inductance when the current passing through the inductor is below the predefined current level, and provides a second inductance when the current passing through the inductor is above the predefined current level. The system according to claim 1 or 2, wherein the second inductance is at least 1 / 100th of the first inductance.

4. The system according to any one of claims 1 to 3, wherein, in the resonant operation, when the current through the inductor falls below the predefined current level, the system supplies a voltage to be applied to the capacitor which is essentially constant at a first voltage level or a second voltage level, and the voltage applied to the capacitor rapidly changes from the first voltage level to the second voltage level, or from the second voltage level to the first voltage level, when the current through the inductor exceeds the predefined current level.

5. The inductor provides a nonlinear inductance such that the first dependence of the inductance from the current in a first direction of the current passing through the inductor is different from the second dependence of the inductance from the current in a second direction of the current passing through the inductor, the first direction being opposite to the second direction, and / or The system according to any one of claims 1 to 4, wherein the system supplies a voltage applied to the capacitor, which is essentially an asymmetrical square voltage.

6. The aforementioned inductor A first inductor having nonlinear inductance, A second inductor having nonlinear inductance and connected in series with the first inductor, A diode that functions as a rectifier and / or is connected in parallel to the first inductor or the second inductor. The system according to claim 5, including the system described in claim 5.

7. The system according to claim 5, wherein the system includes a bias device for exposing the inductor to an external magnetic field, or the system includes a bias circuit for providing a DC bias current through the inductor.

8. The system according to any one of claims 1 to 7, wherein the system includes an adjustment mechanism for adjusting the resonant frequency of the resonant operation.

9. The aforementioned inductor A first inductor having nonlinear inductance, A second inductor having nonlinear inductance and connected in series with the first inductor, Includes, The aforementioned system A first control inductor inductively coupled to the first inductor, A second control inductor inductively coupled to the second inductor and Includes, The system supplies a first control current to the first control inductor and a second control current to the second control inductor. The system according to any one of claims 1 to 8, wherein the first control current has the same amperage as the second control current and in the opposite direction.

10. The system according to any one of claims 1 to 9, wherein the system includes a drive mechanism for exciting the resonant operation.

11. The system according to claim 10, wherein the drive mechanism includes switching of the high-voltage generator, or the drive mechanism includes an amplifier inductively coupled to the inductor, or an amplifier capacitively coupled to the capacitor.

12. The system according to any one of claims 1 to 11, further comprising a smoothing inductor, wherein the first connection terminal of the capacitor is connected to the high-voltage output of the high-voltage generator via the smoothing inductor.

13. A computed tomography apparatus comprising the system described in any one of claims 1 to 12.

14. A method for high-voltage switching of a computed tomography apparatus, wherein the method is The steps of preparing the computed tomography apparatus described in claim 13, The steps include driving the current through the inductor, thereby exciting a resonant action, and switching the high voltage applied to the electrodes of the X-ray tube of the computed tomography apparatus. A method having

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