Strategy for controlling cathode width voltage

Abstract

Methods and systems are provided for controlling an electron beam (70) generated by an x-ray tube assembly (12) including a unipolar cathode (62). In one embodiment, the voltage supplied to the cathode (62) is controlled by a multi-stage switching unit (500) comprising a first control circuit (502) and a second control circuit (504). A bias voltage for turning on the cathode (62) is generated by a voltage source (570) of the second control circuit, and a gridding voltage for turning off the cathode (62) is generated by a plurality of voltage sources (520) of the first control circuit. When transitioning between the bias voltage and the gridding voltage and vice versa, a control strategy is used in which the voltage sources (520) of the first control unit (502) selectively engage and / or disengage in a discontinuous order according to an optimization protocol to prevent voltage imbalance between capacitors (521) of different stages (510) of the multi-stage switching unit (500).

Description

Technical Field

[0001] The subject matter disclosed herein relates to X-ray tube radiation sources, and more particularly to X-ray tube radiation sources having one or several electron beam control electrodes (eg, gridded electrodes). Background Art

[0002] In imaging systems, X-ray tubes are used as a source of X-ray radiation in projection X-ray systems, fluoroscopic systems, tomosynthesis systems, and computed tomography (CT) systems, among others. Typically, an X-ray tube includes a cathode and an anode. The cathode emits a stream of electrons in response to heat generated by an applied current via thermionic effect and in response to an electric field generated by a high voltage applied between the cathode and the anode. The anode includes a target that is struck by the electron stream. Thus, the target generates X-ray radiation and heat. Such systems are useful in medical settings, but are also used for mail and package screening, parts inspection, various research scenarios, and the like.

[0003] The radiation passes through a subject of interest (such as a human patient), and a portion of the radiation strikes a detector or photographic film that collects image data. In some X-ray systems, the photographic film is then developed to produce an image that can be used by a radiologist or attending physician for diagnostic purposes. In digital X-ray systems, a photodetector produces a signal representing the amount or intensity of radiation that impacts discrete pixel areas of the detector surface. The signal can then be processed to generate an image that can be displayed for viewing.

[0004] Interventional radiology (IR) refers to a subspecialty within radiology that provides minimally invasive (or at least limited invasive) diagnosis and treatment of disease. Various devices are provided to provide image guidance related to the diagnosis and treatment of disease. Non-limiting examples of minimally invasive disease treatments include angioplasty and catheter-delivered stents. A wide range of imaging modalities can be used to provide image guidance, such as X-ray equipment, ultrasound, MRI, and other imaging modalities. Interventional radiologists can use imaging equipment during procedures to obtain images used in conjunction with guiding interventional instruments through the body. For example, interventional instruments can utilize needles, catheters, etc.

[0005] The voltage supplied to the electrode of the cathode of the interventional imaging system can be controlled to block X-rays or adjust the intensity of the generated X-rays. Regarding controlling the electrode voltage, it is desirable to be able to produce a fast transition from a low level to a high level (e.g., a gate level to a bias level), and to control the electrode voltage waveform (e.g., settling time, accuracy, ripple, etc.) after the transition to properly control the electron beam. Various factors can affect the transition time. Summary of the invention

[0006] In one example, a method for an interventional imaging system includes applying a voltage to a gridded electrode of a cathode of the interventional imaging system via a multi-stage switching unit, the multi-stage switching unit including a first control circuit and a different second control circuit; during a first transition of the voltage from a first gridded voltage of the interventional imaging system generated by the first control circuit to a second bias voltage of the interventional imaging system generated by the second control circuit, selectively bypassing multiple stages of the first control circuit in a first non-continuous order to reduce the voltage from the first gridded voltage to a common voltage of the interventional imaging system; and during a second transition of the voltage from the second bias voltage generated by the second control circuit to the first gridded voltage generated by the first control circuit, selectively engaging the multiple stages of the first control circuit in a second non-continuous order to increase the voltage from the common voltage to the first gridded voltage.

[0007] The above advantages and other advantages and features of the present specification will be apparent from the following detailed description when considered alone or in conjunction with the accompanying drawings. It should be understood that the above summary is provided to introduce a series of concepts further described in the detailed description in a simplified form. This is not meant to identify key features or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims that follow the detailed description. In addition, the claimed subject matter is not limited to specific implementations that address any shortcomings mentioned above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Various aspects of the present disclosure may be better understood by reading the following detailed description and referring to the accompanying drawings, in which:

[0009] Figure 1 is a schematic diagram of an embodiment of a portion of an X-ray tube (e.g., with gridded electrodes) coupled to an X-ray controller / power supply (e.g., without gridding of the electron beam) according to various embodiments;

[0010] Figure 2 is a schematic diagram of an embodiment of a portion of an X-ray tube (e.g., with gridded electrodes) coupled to an X-ray controller / power supply (e.g., with gridding of the electron beam) according to various embodiments;

[0011] Figure 3 is a schematic diagram of a switch unit of an X-ray tube according to one or more embodiments;

[0012] Figure 4 is a diagram showing the use of one or more embodiments Figure 3 A schematic diagram of a first multi-level topology of a switching unit is shown;

[0013] Figure 5is a diagram showing the use of one or more embodiments Figure 3 A schematic diagram of a second multi-level topology of a switching unit shown;

[0014] Figure 6 is a schematic diagram of an interventional imaging system including a cable according to one or more embodiments;

[0015] Figure 7 is shown for controlling Figure 5 A flowchart of an exemplary method of a second multi-level topology;

[0016] Figure 8 It is shown that according to Figure 7 Method control Figure 5 A first timing diagram of a curve diagram of voltage change over time when the second multi-level topology structure is configured;

[0017] Fig. 9 Shows Figure 8 An exploded view of a portion of

[0018] Fig.10 shows a first graph illustrating output loss at a resistor of a control circuit according to one or more embodiments of the present disclosure;

[0019] Fig.11 shows a second graph illustrating output loss at a resistor of a control circuit according to one or more embodiments of the present disclosure;

[0020] Fig.12 is a second timing diagram illustrating a sequence of events during a first transition from a gridding voltage to a bias voltage in an interventional imaging system utilizing a basic protocol;

[0021] Fig.13 is a third timing diagram illustrating a sequence of events during a second transition from a bias voltage to a gridding voltage in an interventional imaging system utilizing a base protocol in accordance with one or more embodiments of the present disclosure;

[0022] Fig.14 is a fourth timing diagram illustrating a sequence of events during a first transition from a gridding voltage to a bias voltage in an interventional imaging system utilizing an optimized protocol in accordance with one or more embodiments of the present disclosure;

[0023] Fig.15 is a fifth timing diagram illustrating a sequence of events during a second transition from a bias voltage to a gridding voltage in an interventional imaging system utilizing an optimized protocol in accordance with one or more embodiments of the present disclosure; and

[0024] Fig.16 An optimized protocol for controlling the transition from a bias voltage to a gridding voltage according to one or more embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0025] Described herein are methods and systems for generating a voltage profile that can be used to control an electron beam (e.g., control of intensity and / or energy) generated by an X-ray tube assembly of an interventional imaging system. It should be noted that although various embodiments may be described in conjunction with an X-ray tube assembly having a particular configuration, other configurations, geometries, and arrangements are contemplated.

[0026] The x-ray tube includes a cathode that emits a stream of electrons in response to heat generated by an applied voltage, and an anode that includes a target that is struck by the stream of electrons to generate x-rays (e.g., to perform one or more x-ray exposures on a patient of an interventional imaging system). A voltage is applied at a gridded electrode of the cathode to turn the cathode on (e.g., a bias voltage to generate x-rays) or off (e.g., a grid voltage to stop the generation of x-rays).

[0027] The voltage change for switching the cathode on and off can be generated by driving the electronic device of the cathode connected by the cable. The cable can vary in length, changing from about 0.5m to about 40m. However, the method for controlling the cathode by a shorter cable may not be effective when applied to the cathode controlled by a longer cable. Composite factors may include the polarity of the cathode. The cathode can be bipolar, wherein the gridded voltage has a first polarity (e.g., negative) and the bias voltage has an opposite polarity (e.g., positive), or the cathode can be unipolar, wherein the gridded voltage and the bias voltage both have a single polarity (e.g., negative). The method for controlling a bipolar cathode may not be effective when applied to a unipolar cathode. Therefore, due to the dependence on a certain degree of voltage accuracy when applying the bias voltage, the current electronic device topology may not be suitable for driving a bipolar cathode via a long cable.

[0028] Specifically, some methods for driving bipolar cathodes through longer cables may be unnecessarily complex and expensive, and less compact when applied to unipolar cathodes. In addition, less complex methods for driving bipolar cathodes through shorter cables may result in slower transitions, higher losses, and potential inaccuracies when applied to cathodes driven through longer cables. A common problem is the temporary drop in cathode voltage when switching from a first voltage to a second voltage. The temporary voltage drop is related to the length of the cable (e.g., due to parasitic capacitance associated with the cable). The temporary voltage drop may be irrelevant (e.g., the amplitude is very small and the duration is short) when the cable is short (e.g., 0.5m), but may become unmanageable for longer cables. Therefore, current methods for driving cathodes may not be feasible for newer, most advanced interventional imaging systems with unipolar cathodes, which may rely on cables of 40m or more in length.

[0029] To solve this problem, a switch unit for controlling a unipolar cathode via a longer cable can be used, wherein the switch unit has a multi-stage topology, which includes a first control circuit for generating a gridded voltage and a second control circuit for generating a bias voltage. By separating the two functions, the duration of the transition from the gridded voltage to the bias voltage and vice versa can be reduced by performing the transition in two steps: a larger step that can be quickly performed with low precision using the first control circuit, and a smaller step that can be performed with higher precision using the second control circuit. Each of the gridded voltage and the bias voltage can be generated starting from a common voltage (considered as 0V herein for simplicity). That is, during the first transition from the gridded voltage to the bias voltage (e.g., turning on the cathode), the electrode voltage applied to the cathode is first adjusted to the common voltage (larger step) and then adjusted to the bias voltage (smaller step with higher precision). During the second transition from the bias voltage to the gridded voltage (e.g., turning off the cathode), the electrode voltage applied to the cathode is first adjusted to the common voltage (smaller step size) and then adjusted to the gridded voltage (larger step size). By performing the first and second transitions in this manner, the duration can be less than the threshold duration for driving a unipolar cathode via a longer cable.

[0030] However, one problem with this approach is that capacitor voltage imbalances between the levels of the multi-level switch unit may occur specifically during larger steps of transitions from a low gridded voltage (e.g., -8kV) to a common voltage (e.g., 0V) and vice versa, which may damage components of the first control circuit. Although the physics of the transition also applies to smaller steps, the effect is minimal due to the relatively small voltage changes caused by switching from a common voltage to a bias voltage (e.g., -1.2kV) and vice versa. As described in more detail below, the first control circuit includes a plurality of levels, each of which has a capacitance precharged to 1kV. When the desired cathode voltage is -8kV (cathode gate off), the plurality of levels are engaged, and when the cathode desired voltage is a common voltage (e.g., 0V), the plurality of levels are disengaged (e.g., bypassed). Whenever one of the plurality of levels is engaged / disengaged, there is energy transfer to / from the cable and cathode capacitance, as well as energy losses due to switching.

[0031] A straightforward way to control the first control circuit is to engage / disengage multiple stages simultaneously. However, this operation may generate high energy losses, primarily unacceptable current and voltage constraints on the electrical components of the switch unit. Alternatively, the stages may be engaged / disengaged sequentially, resulting in an almost 10x reduction in current and voltage constraints. However, taking full advantage of the energy savings may rely on the timing of the engagement / disengagement of each stage so that each stage reaches a steady state to restore capacitor charging / discharging. The timing to the steady state may depend on the stage capacitance value and the load capacitance value (which includes the cable capacitance), which may be negligible in a computed tomography (CT) system, but may be uncontrollably long in an interventional imaging system due to the longer cable length. Even if the timing between engaging two consecutive stages is not achieved, suboptimal energy savings may still be achieved, so it is still advantageous to operate the two consecutive stages sequentially.

[0032] When operating the stages sequentially with a short time between two consecutive stages, the capacitor voltage imbalance between the stages may temporarily appear. In fact, as the stages are progressively engaged / disengaged from the output and as the capacitors of the engaged stages are charged / discharged at each step, there will be an imbalance between the stages, resulting in a higher voltage constraint and a higher timing to a steady state for the stage that is connected to the output for the longest duration during the transition. Although this problem can be cleared after the relevant stage reaches a steady state, it adds stress to the parts of the circuit, which may cause premature aging and, in the worst case, immediate part failure. Aging and possible sudden part failure can be avoided by selecting larger rated components, but larger rated components can use more space and may be more expensive. Since space is very limited, this method may not be desirable.

[0033] In order to address the issues of aging and possible sudden part failure due to capacitor voltage imbalance, without relying on larger rated components, a control strategy is proposed herein for controlling the engagement / disengagement of the stages of the first control circuit in a manner that keeps the imbalance to a minimum via alternative stage switching during the transition, even before reaching a steady state at each step, which allows most or all stages to be connected to the output for the same duration during the transition.

[0034] Figures 1 to 5 , Fig.10 and Fig.11An exemplary configuration with relative positioning of various parts is shown. In at least one example, if shown as being in direct contact or directly coupled to each other, such elements may be referred to as being in direct contact or directly coupled, respectively. Similarly, in at least one example, elements shown as being adjacent or adjacent to each other may be adjacent or adjacent to each other, respectively. For example, parts placed in coplanar contact with each other may be referred to as being in coplanar contact. For another example, in at least one example, elements positioned to be spaced apart from each other and having only space therebetween without other parts may be described and cited as such. For another example, elements shown as being located above / below / below each other, located on opposite sides or located between the left / right sides of each other may be described and cited as such relative to each other. In addition, as shown in the figure, in at least one example, the topmost element or the point of the element may be referred to as the "top" of the part, and the bottommost element or the point of the element may be referred to as the "bottom" of the part. As used herein, top / bottom, upper / lower, above / below may be relative to the vertical axis of the figure, and may be used to describe the position of the elements relative to each other in the figure. Thus, in one example, elements shown as being above other elements are positioned vertically above other elements. For another example, the shapes of the elements depicted in the figures may be referred to as having those shapes (e.g., such as being round, straight, planar, curved, rounded, chamfered, angled, etc.). In addition, in at least one example, elements shown as intersecting each other may be referred to as intersecting elements or intersecting each other. In addition, in one example, elements shown as being within another element or being shown as being outside another element may be described and referenced as such.

[0035] Figure 1 and Figure 2 is a schematic diagram of an embodiment of a portion of an X-ray tube 12 (e.g., with a gridded electrode 58) coupled to an X-ray controller / power supply 38 (e.g., without electron beam gridding). The X-ray tube 12 includes an electron beam source 60, an anode assembly 64, and a gridded electrode 58, the electron beam source including a cathode 62, and the anode assembly including an anode 66. The cathode 62, the anode 66, and the gridded electrode 58 can be disposed within a housing (not shown) such as a glass envelope or a metal envelope. The X-ray tube 12 can be positioned within a case (not shown), which can be made of aluminum and lined with leads. In some embodiments, the anode assembly 64 can include a rotor and a stator (not shown) external to the X-ray tube 12, the stator at least partially surrounding the rotor for rotating the anode 66 during operation.

[0036] The cathode 62 is configured to receive an electrical signal via a series of electrical leads 68 (eg, coupled to a high voltage source) that initiates emission of an electron beam 70. The anode 66 is configured to receive the electron beam 70 at a target surface 72 and is configured to emit electrons at a target surface 72. Figure 2, as depicted in the figure, emits X-rays when struck by the electron beam 70, as indicated by the dashed line 74. The electrical signal may be a timing / control signal (via the X-ray controller / power supply 38) that causes the cathode 62 to emit an electron beam 70 of one or more energies. In addition, the electrical signal may at least partially control the electrical potential between the cathode 62 and the anode 66. The voltage difference between the cathode 62 and the anode 66 may range from tens of thousands of volts to over hundreds of thousands of volts. The anode 66 is coupled to a rotor (not shown) via a shaft (not shown). The rotation of the anode 66 allows the electron beam 70 to continuously strike different points on the periphery of the anode. Within the housing of the X-ray tube 12, preferably maintained at room temperature for about 10 -5 To about 10 -9 A vacuum of the order of Torr is applied to permit undisturbed transmission of the electron beam 70 between the cathode 62 and the anode 66.

[0037] The grid electrode 58 is configured to receive an electrical signal via a series of electrical leads 76 that causes the grid electrode 58 to grid the electron beam 70. The electrical signal can be a timing / control signal (via the X-ray controller / power supply 38) that causes the grid electrode 58 to grid the electron beam 70 when it is energized or powered to a specific level (e.g., less than +6000V to -5000V). The grid electrode 58 is disposed around the path 78 of the electron beam 70 between the electron beam source 60 (e.g., cathode 62) and the anode assembly 64 (e.g., anode 66). The grid electrode 58 can be annular in shape. As shown in FIG. Figure 3 As depicted, when the gridded electrode 58 is powered to a particular level (e.g., -3000 V to -5000 V), the electron beam 70 may be completely gridded or blocked from striking the anode 66. In certain embodiments, when the gridded electrode is energized at a different level (e.g., less than +6000 V and to -3000 V), the electron beam 70 may be partially gridded, resulting in a reduction in the electron beam 70 striking the anode 66. If the gridded electrode 58 is powered at a particular non-gridding level (e.g., +6000 V), no gridding of the electron beam 70 occurs (e.g., Figure 2 ). As discussed in more detail below, during the dynamic focus mode, the gridding of the electron beam 70 by the gridding electrode 58 is synchronized with the planned transition (e.g., the unstable portion). The gridding of the electron beam 70 can occur in a binary manner (e.g., on (no gridding) / off (gridding)). In other embodiments, the gridding of the electron beam can occur by switching between a fully gridded state and a partially gridded state. In other embodiments, the gridding of the electron beam can occur by switching between no gridding and partial gridding. In some embodiments, a constant partial gridding can be applied to the electron beam.

[0038] Various combinations of bias voltages and currents may be employed to control the electron beam. Specifically, different circuits that may be used to form a multi-stage control arrangement will now be described that may be implemented as a multi-stage architecture or topology with a voltage supply generated at the X-ray controller / power supply 38. These stages may be configured to change voltages quickly (such as sub-microseconds), control the maximum voltage, and / or control the shape of the waveform used to apply the voltage to the gridded electrode 58. These stages may each be configured differently to allow switching at different speeds.

[0039] For example, Figure 3 A switch cell 300 is shown, which can be used to form a level of a multi-level architecture or topology. It should be noted that the switch cell can be formed by different types of switch devices. In various embodiments, the switch device is a transistor, such as a metal oxide semiconductor field effect transistor (MOSFET). However, any type of switch device can be used, such as an insulated gate bipolar transistor (IGBT), which can be formed by different materials (such as silicon (Si), silicon carbide (SiC), gallium arsenide (GaAs) or any other material suitable for building such devices).

[0040] The switch unit 300 includes a pair of switches 302 and 304 (connected in series), each of which can be independently controlled to provide voltage switching from a reference voltage (shown as a voltage source 306). In this embodiment, the switch 302 is labeled as switch A and the switch 304 is labeled as switch B, where the voltage output (Vout) 308 is between the switches 302 and 304. The switch unit 300 includes a capacitor 321, which is connected to the switches 302 and 304 in parallel with the voltage source 306. The voltage source 306 generates a charge at the capacitor 321, which can be discharged according to the configuration of the switches 302 and 304.

[0041] In operation, in various embodiments, one of switches 302 and 304 is closed (creating a short circuit in the closed state) and the other switch is open (in the open state). For example, if switch 304 is closed and switch 302 is open, then Vout = Vcommon, which in various embodiments is zero volts (in Figure 3 If switch 304 is open and switch 302 is closed, then Vout = Vcommon + V.

[0042] The switch units 300 may be combined or cascaded, for example, to form Figure 4 The multi-stage switch unit 400 shown in FIG. 4 is shown in FIG. 4 . It should be noted that similar reference numerals denote similar parts. Figure 4Two stages are shown, but additional stages may be provided as described in more detail herein.It should be noted that for each of the switch cells 300, during a particular operating state, one of the switches 302 or 304 is open, while the other of the switches 304 or 302 is closed.

[0043] In operation, if switches 304a and 304b are closed (in which case switches 302a and 302b are open), voltage sources 306a and 306b and capacitors 321a and 321b are not connected to the output and Vout = Vcommon. If switch 304b is open and switch 304a is closed (in which case switch 302b is closed and switch 302a is open), voltage source 306a and capacitor 321a are not connected to the output, voltage source 306b and capacitor 321b are connected to the output and Vout = Vcommon + V. Similarly, if switch 304b is closed and switch 304a is open (in which case switch 302b is open and switch 302a is closed), voltage source 306a and capacitor 321a are connected to the output, voltage source 306b and capacitor 321b are not connected to the output and Vout = Vcommon + V. If switches 304a and 304b are both open (in which case switches 302a and 302b are both closed), then voltage sources 306a and 306b and capacitors 321a and 321b are connected to the output and Vout = Vcommon + V + V. Thus, in this operating state, the reference voltages from the two stages are summed. Thus, as more stages are added, incremental increases in the output voltage are possible (e.g., discrete changes) by opening and closing various switches in one or more of the stages. For example, if an output voltage of 6 kV (Vout) is desired, then the output voltage may be similar to Figure 4 The arrangement shown is used to connect six switch units 300, each of which has a 1 kV reference voltage source 306. In addition, by controlling the switches as described herein, the 1 kV reference voltage source 306 can be used to generate incremental increases of 1 kV between 0 kV and 6 kV. Figure 3 The one-stage configuration described above, the role of the capacitor 321 of each stage is to limit the temporary voltage reduction or increase from the 1kV reference voltage of the stage when the 1kV reference and capacitor are connected to the output and the output voltage changes. It should be noted that since each switch unit 300 has a reference voltage of 1kV in this example, the rating of switches 302 and 304 can be 1kV instead of 6kV and still provide a maximum output voltage from the multi-stage arrangement of 6kV. It should also be noted that the reference voltage at different stages may be different. For example, some stages may have a 1kV reference voltage, while other stages have a 2kV reference voltage. Other reference voltage values ​​may be provided, which may be non-integer values.

[0044] Figure 5An exemplary multi-stage switch unit 500 is shown, which includes a plurality of combined or cascaded switch units 300 in a multi-stage architecture or topology. The multi-stage switch unit 500 shows an electronic device topology for a unipolar cathode for an interventional imaging system, which can be gridded (e.g., turned off) and biased (e.g., turned on) using a voltage of only one polarity (negative polarity). Specifically, the unipolar cathode can be controlled by applying an output electrode voltage (e.g., V output 308) to a gridded electrode 550, where the output voltage (also referred to herein as an electrode voltage) is output by the multi-stage switch unit 500. The multi-stage switch unit 500 advantageously separates the generation of a gridding voltage and a bias voltage at the gridded electrode 550, where the gridding voltage is generated by a first control circuit 502 and the bias voltage is generated by a second control circuit 504.

[0045] The first control circuit 502 includes eight switching units (also referred to herein as stages): a first stage 510, a second stage 511, a third stage 512, a fourth stage 513, a fifth stage 514, a sixth stage 515, a seventh stage 516, and an eighth stage 517. In other embodiments, the first control circuit 502 may include a different number of switching units, depending on the voltage level required. Each stage may be Figure 3 and Figure 4 300, wherein each stage includes a voltage source 520, a first switch 522, and a second switch 524 (e.g., voltage source 306 and switches 302 and 204, respectively). However, compared to switch unit 300 and multi-stage switch unit 400, multi-stage switch unit 500 is a unipolar unit that generates a negative gridding voltage and a bias voltage (e.g., both the gridding voltage and the bias voltage are negative voltages applied to gridding electrode 550). Figure 4 Different from the multi-stage switch unit 400 , in the electronic device topology of the multi-stage switch unit 500 , a unipolar bridge 540 is used to connect each stage of the multi-stage switch unit 500 .

[0046] In various embodiments, each voltage source 520 of each stage of the first control circuit 502 can be connected via a corresponding capacitor 521 (e.g., Figure 3The capacitor 321 of the first control circuit 502 supplies a voltage of up to 1 kV. Therefore, when all stages are negatively connected to the output, the total electrode voltage output by the first control circuit 502 can be -8 kV (e.g., the sum of the -1 kV outputs from each of the stages 510-517). The total electrode voltage can be a negative gridded voltage greater than a threshold voltage (e.g., -5.5 kV) in magnitude, wherein a first voltage greater than the threshold voltage does not generate X-rays, and a second voltage less than the threshold voltage can generate X-rays. In other words, the interventional imaging system can be turned off by applying a total electrode voltage exceeding a threshold value (e.g., a gridded voltage) via the stages 510-517, and the interventional system can be turned on by applying a total electrode voltage less than the threshold voltage. In other embodiments, different numbers of stages can be used and / or voltage sources supplying different amounts of voltage can be used to generate different total voltages exceeding the threshold voltage.

[0047] During the bias to gate transition, all capacitors 521 of the stages 510-517 will be slightly discharged due to the discharge current used to offset the parasitic capacitance generated by the cables used to control the unipolar cathodes. Therefore, immediately after the bias to gate transition (e.g., after 50 μs), the total electrode voltage supplied by the corresponding capacitors 521 of the stages 510-517 will be less than the expected nominal voltage (e.g., the number of stages multiplied by the reference voltage), but still greater than the threshold voltage (e.g., -5.5 kV) to not generate X-rays. After a longer time (e.g., 5 ms), the capacitors 521 of the stages 510-517 will achieve the nominal voltage value using the voltage source 520 of the stages 510-517. hereinafter referred to as Figure 8 The temporary voltage drop is described in more detail. In some examples, the length of the cable can be 40m or more, with a total capacitance of approximately 7nF. In some embodiments, the first control circuit 502 can include a resistor 532 and an inductor 534, which can limit the peak current during the transition, minimize energy losses due to parasitic capacitance during the transition, and / or protect the electronics of the first control circuit 502 from tube arcing.

[0048] Brief reference Fig.10, shows a first output loss graph 1000 corresponding to a first embodiment of the first control circuit 502 that does not include the inductor 534. The first output loss graph 1000 includes a first output voltage curve graph 1002, wherein the first output voltage curve graph 1002 includes a first step output voltage curve 1010 and a first circuit output voltage curve 1012. The first step output voltage curve 1010 shows the command voltage applied to the gridded electrode 550 over time during the transition from the bias voltage to the gridded voltage, and the first circuit output voltage curve 1012 shows the actual electrode voltage generated at the gridded electrode 550 within the transition due to the command voltage. The first output loss graph 1000 also includes a first output current graph 1004 showing a first output current curve 1014 of the output current generated at the gridded electrode 550 due to the first circuit output voltage shown by curve 1012, and a first output resistor loss graph 1006 showing a first output resistor loss curve 1016 indicating energy loss over time at the resistor 532 based on the first output current curve 1014. As shown by the first output resistor loss curve 1016, the output resistor losses may approach 12 kW peak.

[0049] In contrast, Fig.11 A second output loss graph 1100 is shown corresponding to a second embodiment of the first control circuit 502 including the inductor 534. The second output loss graph 1100 includes a second output voltage graph 1102, wherein the second output voltage graph 1102 includes a second step output voltage graph 1110 and a second circuit output voltage graph 1112. The second step output voltage graph 1110 shows the command voltage applied to the gridded electrode 550 over time during the transition from the bias voltage to the gridded voltage, and the second circuit output voltage graph 1112 shows the actual electrode voltage generated at the gridded electrode 550 within the transition due to the command voltage. The second output loss graph 1100 also includes a second output current graph 1104 showing a second output current curve 1114 of the output current generated at the gridded electrode 550 due to the second circuit output voltage shown by the curve 1112, and a second output resistor loss graph 1106 showing a second output resistor loss curve 1116 indicating energy loss over time at the resistor 532 based on the second output current curve 1114. Fig.10Compared to the first output current curve 1014, the second output current curve 1114 shows an output current with a reduced amplitude when the inductor 534 is added to the first control circuit 502, which can reduce the constraints on the components of the switch unit 500 during the transition. Therefore, the output resistor loss indicated by the second output resistor loss curve 1116 (when the inductor 534 is included in the first control circuit 502) is lower than that indicated by Fig.10 The first output resistor loss curve 1016 indicates output resistor losses (eg, approximately 3 kW peak instead of 12 kW peak when the inductor 534 is not included in the first control circuit 502 ).

[0050] Back to Figure 5 In various embodiments, the second control circuit 504 controlling the bias voltage includes a high-precision voltage source 570, a capacitor 571 (e.g., capacitor 321) and various switches, such as switches 562-563. The voltage source 570 can be a variable, high-precision voltage source that can be supplied between 0V and -1200V with high accuracy (e.g., + / -50V) via the capacitor 571. A simplified bidirectional flyback can be used for the voltage source 570. The second control circuit 504 can generate a bias voltage (or not generate a bias voltage) by switching either or both of the switches 562 and 563 from a closed position to an open position (or vice versa). The level of the first control circuit 502 has no effect on the output voltage of the high-precision voltage source 570, which can be independently connected to the output or bypassed. In other words, in the first gate mode, the stages 510-517 are connected and the high precision voltage source 570 is bypassed, and in the second bias mode, the stages 510-517 are bypassed and the high precision voltage source 570 is connected. In this way, the selection of which voltage is applied to the gridded electrode 550 is performed by driving the selection switches 562, 563 and the switches from the stages 510 to 517. This hardware simplification is beneficial for the control strategy of the multi-stage switching cell 500, which makes the transition from gate to bias and vice versa very reproducible.

[0051] Figure 6 is a schematic diagram of an imaging system 600 according to various embodiments. The imaging system 600 may include Figure 1 and Figure 2 The described interventional imaging system may be included in the interventional imaging system. The imaging system 600 includes an X-ray unit 610 (e.g., Figure 1 X-ray tube assembly 50), controller 620 (eg, controller 66), including a plurality of voltage control modules 640 (eg, Figure 2 The circuit component 630 (eg, Figure 5In general, the controller 620 is operably coupled to the circuit assembly 630 and provides a desired voltage (or voltages) to the X-ray unit 610 via the cable 650 using the voltage control module 630.

[0052] In the illustrated embodiment, the X-ray unit 610 includes an electrode 612. A voltage above the gridding voltage threshold supplied to the electrode 612 deactivates the X-ray unit 610 by stopping the electron beam. A secondary voltage (bias voltage) supplied to the electrode 612, which is much lower than the gridding voltage, focuses or controls the size of the generated electron beam.

[0053] The controller 620 is configured to control various aspects of the system 100, including providing voltage to control the X-ray unit 610, for example, by controlling the voltage control module 640 of the circuit assembly 630. For example, based on the sensed voltage in the cable 650 measured using the sensor 653, the controller 620 can adjust the voltage provided to the X-ray unit 610 by controlling switches of one or more fine tuning circuit portions of the voltage control module 640 (e.g., switches 522 and 524 of the stages 510-517). The controller 620 may include processing circuitry configured to perform one or more tasks, functions, or steps discussed herein. It may be noted that "controller" as used herein is not necessarily intended to be limited to a single processor or computer. For example, the controller 620 may include multiple processors and / or computers, which may be integrated in a common housing or unit or which may be distributed in various units or housings. The circuit assembly 630 may be generally similar to the multi-stage switch unit 500 discussed herein in various aspects.

[0054] In the illustrated embodiment, the controller 620 includes a memory 622, which includes a tangible and non-transitory computer readable medium. It can be noted that the memory 622 can store thereon instructions for directing the controller 620 to perform one or more aspects of the methods, steps or processes discussed herein. In various embodiments, the controller 620 can simultaneously control a separate voltage control module and / or one or more groups of voltage control modules to control the total delivery voltage. For example, the controller 620 can actuate the switch portions of all or most of the modules to provide a large voltage change to turn on and off the electrodes, and can control one or more of the modules to fine tune the voltage to focus the electron beam.

[0055] Cable 650 operably connects circuit assembly 630 and X-ray unit 610. For example, conductor 652 of cable 650 can be operably coupled to a set of voltage control modules and to electrodes 612. The voltage provided via conductor 652 can be used to turn X-ray unit 610 on and off and / or can be used to control the focus of the electron beam. The provided voltage can include voltages applied to electrodes 612 (e.g., Figure 5 The grid voltage and / or bias voltage of the electrode 550 in the embodiment of the present invention may be generated by a first control circuit (e.g., the first control circuit 502) and a second control circuit (e.g., the second control circuit 504), respectively. Figure 5 As described, the generation of the gridding voltage and the bias voltage may also be separated.

[0056] In various embodiments, redundancy can be provided to improve reliability. For example, in some embodiments, multiple low voltage circuit portions can be utilized, wherein each low voltage circuit portion is coupled to a group of voltage control modules and is configured to control the voltage provided to the voltage control module of the corresponding group from a given low voltage circuit portion. Alternatively or additionally, multiple transformers can be utilized, wherein each transformer is operably coupled to at least one corresponding voltage control module. In some embodiments, a given transformer and a corresponding low voltage circuit portion can be coupled to a corresponding low voltage circuit portion.

[0057] Figure 7 A method for controlling a multi-level architecture such as Figure 5 The circuit of the multi-stage switch unit 500 is used to provide an interventional imaging system (such as the one described herein) Figure 6 , Fig.10 and Fig.11 A method 700 for powering a unipolar cathode of an X-ray tube of an interventional imaging system (as mentioned in ). The unipolar cathode can be used in modern interventional imaging systems, which can use a voltage greater than a threshold negative voltage (e.g., -8kV) for gate shutoff and rely on a precisely controllable bias voltage with an accuracy of + / -50V between a common voltage (e.g., a reference voltage for the circuit, which is considered to be 0V for simplicity in this article) and -1.2kV to turn on and control the electron beam shape. In other words, the bias voltage and gridding voltage are expressed relative to the common voltage. It should be understood that technically, the common voltage can be a high voltage, such as up to 125kV. Therefore, although the common voltage is referred to as 0V in this article, the common voltage can be -125kV in absolute terms, and the gridding voltage of -8kV can be an absolute voltage of -133kV.

[0058] Such a system may include a constraint for a maximum transition time from on to off and vice versa of less than 50 us, which may not be met by other alternative circuit control architectures.Method 700 may be performed by a controller or processor of an interventional imaging system based on instructions stored in a memory of the interventional imaging system.

[0059] Compared to alternative circuit control architectures, the multi-stage circuit of method 700 separates the first gate function from the second bias function, as described above with reference to Figure 5 As described, the electronics of the circuit are operated so that cathode opening is accomplished in two steps: from the off voltage (e.g., -8 kV) to the common voltage, and then from the common voltage to the desired bias voltage (e.g., -1.2 kV). Equivalently, cathode shutoff will also be accomplished in two steps: from the bias voltage (e.g., -1.2 kV) to the common voltage, and then from the common voltage to the off (gridding) voltage (e.g., -8 kV).

[0060] The method 700 begins at 702, where the method 700 includes receiving a first instruction to turn on a unipolar cathode of an interventional imaging system. In various embodiments, the first instruction may be an instruction to initiate generation of an X-ray pulse via a protocol selected by an operator of the interventional imaging system.

[0061] At 704, method 700 includes reducing the electrode voltage supplied to the gridded electrode 550 by one or more -1 kV first voltage sources of the interventional imaging system to the common voltage. It should be understood that since the voltage supplied to the gridded electrode 550 is a negative voltage, for purposes of the present disclosure, reducing the electrode voltage refers to reducing the absolute value of the electrode voltage (e.g., reducing the electrode voltage in a negative direction), and increasing the electrode voltage refers to increasing the absolute value of the electrode voltage (e.g., increasing the electrode voltage in a negative direction). The first voltage source may be Figure 5 A non-limiting example of a voltage source 520 for a stage 510-517 of a first control circuit 502 of a multi-stage switch unit 500, wherein a gridded voltage is achieved by combining multiple stage voltages generated by each of the stages 510-517, as described above. When the electrode voltage is reduced by sequentially bypassing the first voltage source, the second voltage source of the second control circuit (e.g., the high-precision voltage source 570 of the second control circuit 504) can remain turned off so that the second control circuit does not generate a voltage. For example, the second voltage source can be turned off by actuating switches 562-563 to the bypass position.

[0062] Reducing the electrode voltage supplied by one or more voltage sources to the gridded electrode 550 to the common voltage may include shutting down each of the first voltage sources in a series of steps, thereby reducing the electrode voltage by 1 kV at each step as the corresponding stage is bypassed until all voltage sources are shut down and the voltage supplied to the gridded electrode 550 is the common voltage. Each of the voltage sources may be shut down by opening or closing switches 522 and 524 of each of the stages 510-517, as described above with reference to Figure 4 Described below. Figure 8 and Fig. 9 The shut down of the voltage source is described in more detail.

[0063] In one approach, the first voltage source may be turned off and the stages may be bypassed by following a basic protocol in which the stages are bypassed sequentially from stage 510-517 in a continuous manner. For example, the first voltage source 520 of the first stage 510 may be turned off first; the second voltage source 520 of the second stage 511 may be turned off; the third voltage source 520 of the third stage 511 may be turned off; and so on until the eighth voltage source 520 of the eighth stage 517 is turned off. However, if the stages are bypassed sequentially in a continuous manner, then due to the reference Figure 6 The higher capacitance of the longer cables described may cause voltage imbalances between capacitors 521 of stages 510 - 517. Voltage imbalances may cause premature aging and possibly failure of components of the stages, including switches 522 and 524.

[0064] To reduce voltage imbalance, the levels 510-517 may be bypassed according to an alternative control strategy that specifies a first non-continuous order for shutting down the first voltage source. The first non-continuous order may be specified in a first optimization protocol that establishes a sequence for disengaging the levels 510-517 so that the voltage imbalance is minimized. At each step of the sequence, one or more levels may be selectively bypassed or engaged. For example, at the first step of the optimization protocol, the first level 510 may be bypassed (e.g., the voltage source 520 of the first level 510 may be shut down); at the second step, the fourth level 513 may be bypassed; at the third step, the fifth level 514 and the sixth level 515 may be bypassed and the fourth level 513 may be engaged; at the fourth step, the seventh level 516 and the eighth level 517 may be bypassed and the fifth level 514 may be engaged; and so on, until all levels 510-517 are bypassed. By selectively disengaging and engaging the stages in a non-sequential order, the voltages generated at the capacitors 521 of the stages 510-517 may be partially or fully equalized so that voltage imbalance is prevented. Thus, potential damage to components may be prevented or avoided. Figures 12 to 16 Alternative control strategies are described in more detail.

[0065] At 706, method 700 includes increasing the electrode voltage supplied to gridded electrode 550 from the common voltage to a bias voltage (e.g., -1.2 kV, with an accuracy of + / - 50V). Increasing the electrode voltage supplied to gridded electrode 550 from the common voltage to the bias voltage may include maintaining the voltage source of stages 510-517 off. At the same time, the bias voltage may be generated by second control circuit 504, which may be connected to gridded electrode 550 by opening switch 563 and closing switch 562. When the bias voltage is reached, the cathode may be turned on, whereby X-rays may be generated by the cathode and the X-ray may be performed.

[0066] At 708, method 700 includes receiving a second instruction to turn off the unipolar cathode (eg, to stop X-rays). The second instruction may be generated by the X-ray exposure protocol, or generated in a different manner.

[0067] At 710, method 700 includes reducing the electrode voltage from the bias voltage to the common voltage. Reducing the electrode voltage to the common voltage can be accomplished by opening switch 562 of the second control circuit and closing switch 563, so that no bias voltage generated by the second voltage source is applied to the cathode (e.g., to the gridded electrode 550). Reducing the electrode voltage from the bias voltage to the common voltage via the second control circuit can be performed quickly and without precision.

[0068] At 712, method 700 includes increasing the electrode voltage from the common voltage to the gridded voltage to turn off the unipolar cathode, thereby ending the X-ray. Increasing the electrode voltage to the common voltage can be achieved as described above with reference to steps 704 and / or 706, but wherein the individual voltage sources of the various stages of the multi-stage circuit are sequentially turned on. Specifically, a second optimization protocol can be used to sequentially engage the stages 510-517 in a second non-continuous order similar to the first non-continuous order at step 704 above to avoid voltage imbalances generated by cable capacitance. In various embodiments, the second non-continuous order can be the inverse order of the first non-continuous order. For example, at the first step length of the optimization protocol, the eighth stage 517 may be engaged (e.g., the voltage source 520 of the eighth stage 517 may be turned on); at the second step length, the sixth stage 515 and the seventh stage 516 may be engaged and the eighth stage 517 may be bypassed; at the third step length, the seventh stage 516 may be bypassed and the fourth stage 513 and the fifth stage 514 may be engaged; and so on, until all stages 510-517 are engaged. By selectively disengaging and engaging the stages in a non-sequential order, the voltages generated at the capacitors 521 of the stages 510-517 may be partially or fully equalized, so that voltage imbalance is prevented. Therefore, potential damage to components may be prevented or avoided.

[0069] In some embodiments, a matrix (such as that described below with reference to Fig.16 Similarly, a first non-contiguous order may be established in a matrix used by a controller of an interventional imaging system to execute a first optimization protocol.

[0070] Thus, the electrode voltage applied to the gridded electrode 550 to begin X-ray exposure may be generated by the second control circuit, and the electrode voltage applied to the gridded electrode 550 to end X-ray exposure may be generated by the first control circuit. The separation of these two functions allows for a reduction in voltage when precision (grid) is not required, while allowing for appropriate voltage precision for short periods of time when the bias voltage is applied to the gridded electrode 550. One advantage of separating these two functions is that the bias voltage generated by the second voltage source 570 of the second control circuit 504 may not be subject to the effects of being connected to a long cable (e.g., Figure 6 The temporary voltage reduction at the cathode gridded electrode 550 is caused by parasitic capacitance associated with the cable 650 of the cathode. During the transition from the common voltage to the bias voltage (e.g., -1.2 kV), the temporary voltage reduction can be minimal because it is proportional to the magnitude of the relatively small voltage change and can be easily absorbed by the maximum allowed transition duration and accuracy specified by the interventional imaging system. Similarly, during the cathode shutdown period, the electrode voltage is switched to the common voltage (thereby avoiding the temporary voltage drop) and is not then switched to the gridded voltage value.

[0071] During this final step of switching from the common voltage to -8 kV, a temporary voltage reduction may be evident when the electrode voltage reaches -7.1 kV, after which the electrode voltage may be increased more slowly to -8 kV, as shown in FIG. Figure 8 As shown. The temporary voltage reduction may have little effect on the operation of the cathode as long as the electrode voltage reached immediately after the switch occurs (-7.1 kV) is below the cathode's shutoff gating value applied by the interventional X-ray tube (e.g., -7 kV). The temporary voltage reduction may then fade away within a few milliseconds, allowing the cathode to reach the commanded steady state value at the gridded voltage (e.g., -8 kV).

[0072] Reference now Figure 8 , the exemplary timing diagram 800 shows the Figure 7 The method 700 comprises: Figure 5 8. The transition of the electrode voltage generated by the circuit of the multi-stage architecture of the multi-stage switching unit 500 over time. Time is shown on the horizontal axis of the timing diagram 800, and the electrode voltage is shown on the vertical axis.

[0073] Timing diagram 800 shows curve 802, which shows the amount of electrode voltage generated by the circuit over time when the circuit transitions from a first voltage, at which the unipolar cathode of the interventional imaging system is turned off (e.g., no X-rays are generated and no patient of the interventional imaging system is exposed to radiation), to a second bias voltage, at which the cathode is turned on (e.g., X-rays are generated and the patient is exposed to radiation). The time points of interest during the transition are shown by vertical dotted lines. In the depicted embodiment, the second bias voltage at which the cathode is turned on is -1.2 kV, with an accuracy of + / - 50 V, indicated by dashed line 804. Dashed line 806 indicates a threshold voltage of -5.5 kV, at which an electron beam may not be generated by the cathode. A voltage of -8 kV or less may be used to gate-off newer interventional imaging systems, as indicated by dashed line 808. In the depicted embodiment, the first voltage at which the cathode is gated off is −8 kV, as indicated by dashed line 810 .

[0074] At time t0, the cathode is turned off by the gate. At time t1, an X-ray exposure may be initiated via the interventional imaging system. For example, the X-ray exposure may be initiated according to a protocol executed by the interventional imaging system based on input from an operator of the interventional imaging system. When the X-ray exposure is initiated between time t1 and time t2, an instruction is provided to a controller of the interventional imaging system that, when executed, causes one or more switches of the multi-stage circuit to reduce the electrode voltage (in a negative direction) to a common voltage of the interventional imaging system, as indicated by curve 802. In the depicted embodiment, the common voltage is considered to be 0V.

[0075] Between time t2 and time t3, the electrode voltage is maintained at a common voltage (e.g., 0V). For example, the time between time t2 and time t3 may be less than 2.5us. In general, the time of 3.0us may be a threshold duration imposed by the interventional imaging system to stabilize the electrode voltage delivered to the gridded electrode 550 at each step of the transition between voltages. Fig. 9 A set of exemplary steps describing the transition. At time t3, an instruction is supplied to the controller, which, when executed, actuates one or more switches of the multi-stage circuit to increase the electrode voltage. Between time t3 and time t4, the electrode voltage increases from the common voltage (in the negative direction) to a second bias voltage of approximately -1.2 kV.

[0076] At time t4, a bias voltage is supplied to the cathode, and the cathode is turned on, thereby generating X-rays by the interventional imaging system and performing X-ray exposure. X-ray exposure is performed from time t4 to time t5. At time t5, the X-ray exposure is stopped, for example, according to the protocol. When the X-ray exposure is stopped, an instruction is supplied to the controller, which, when executed, actuates one or more switches of the multi-stage circuit to reduce the electrode voltage (in the negative direction) back to the common voltage. At time t6, the electrode voltage reaches the common voltage, which is maintained from time t6 to time t7.

[0077] At time t7, instructions are supplied to the controller which, when executed, actuate one or more switches of the multi-stage circuit to increase the electrode voltage (in a negative direction) back to the first voltage.Between time t7 and time t8, the electrode voltage increases (in a negative direction).

[0078] At time t8, the electrode voltage has increased to -7.1 kV, achieving the threshold voltage relied upon by newer interventional imaging systems for gate shutoff. Thus, by time t8, the interventional imaging system is no longer generating x-rays, having exceeded the threshold for generating the electron beam indicated by dashed line 806, and the patient is not exposed to radiation. Between time t8 and time t9, due to the temporary voltage reduction caused by the cable length described above, the electrode voltage slowly increases (in the negative direction) to achieve a first voltage at which, in this embodiment, the cathode is gate shutoff.

[0079] Therefore, under the proposed method for controlling the voltage transition between the first gridding voltage and the second bias voltage (and vice versa), the reference Figure 5 The described multi-stage circuit architecture can control the electrode voltage over a transition in a manner that can reduce the time of the transition while increasing the accuracy of the transition. Current methods of reducing the electrode voltage from a first gridded voltage to a second bias voltage can take a first, longer amount of time because of the size of the difference between the first gridded voltage and the second bias voltage and the accuracy relied upon for implementing the bias voltage. In contrast, the proposed method performs the transition in a second, shorter amount of time by breaking the transition into two separate steps.

[0080] When the cathode is turned on, in the first step, the electrode voltage is reduced to the common voltage in a first transition (e.g., between time t1 and time t2), and in the second step, the electrode voltage is increased to the bias voltage in a second transition (e.g., between time t3 and t4). The first step and the second step can be performed more quickly than directly reducing the electrode voltage to a precise, different (e.g., non-zero) voltage because the first transition generated by the second control circuit 504 (e.g., the bias circuit) is independent of the second transition generated by the first control circuit 502 (e.g., the gridding circuit). Therefore, the high-precision voltage source 570 of the second control circuit 504 can be less disturbed, and the bias voltage can be restored quickly and with a desired accuracy (e.g., less than 100 μs).

[0081] Similarly, when the unipolar cathode is turned off, the second transition from the second bias voltage to the first gridded voltage (e.g., time t5 to t9) can be performed in two steps: a first step in which the electrode voltage is reduced to the common voltage (by connecting to the common voltage, where precise control of the voltage transition is not an issue); and a second step in which the electrode voltage is increased to the first gridded voltage. During the second step, the voltage transition from the common voltage to the threshold voltage for the gate to turn off the cathode (e.g., time t7 to t8) can be performed quickly (e.g., in less than 50us) and with lower precision because once the cathode is no longer generating X-rays, achieving the first gridded voltage can be completed over a longer period of time, as indicated by curve 802 between times t8 and t9. For example, the longer period of time can be up to 5ms.

[0082] Fig. 9 An exploded view 900 of a portion of the timing diagram 800 (including the curve 802) is shown. Specifically, a portion of the curve 802 between time t1 and time t4 is shown, where the electrode voltage decreases (in a negative direction) from a first gridded voltage (e.g., -8 kV) to a common voltage (e.g., 0 V), and then increases to a second bias voltage (e.g., -1.2 kV with an accuracy of + / - 50 V). The exploded view 900 shows that the electrode voltage decreases in a series of steps 904. Each of the steps 904 may correspond to a step by opening or closing a multi-stage circuit (e.g., Figure 5The first gridded voltage may be generated by a first configuration of switches 522 and 524 of each of the stages 510-517, wherein the first configuration generates a maximum voltage amount (e.g., -8 kV) of the multi-stage circuit. At time 910, one or two switches of the first stage 510 are opened or closed to turn off the 1 kV voltage source 520 of the first stage 510, thereby reducing the negative voltage amount to -7 kV. At time 911, one or two switches of the second stage 511 are opened or closed to turn off the corresponding 1 kV voltage source 520, thereby reducing the negative voltage amount to -6 kV. At time 912, one or two switches of the third stage 512 are opened or closed to turn off the corresponding 1 kV voltage source 520, thereby reducing the negative voltage amount to -5 kV, and so on, until time t4, when all 1 kV voltage sources 520 of all stages 510-517 are turned off, and the electrode voltage is a common voltage.

[0083] Then, at time t4, a bias voltage shown by line 906 may be generated by the second control circuit 504 of the multi-stage switch unit 500. For example, switches 562-563 of the multi-stage switch unit 500 may be actuated to generate the bias voltage via the second high-precision voltage source 570. In this manner, the transition from the first gridded voltage to the bias voltage is advantageously performed in two steps by two different circuits of the multi-stage circuit. The first total time 920 taken by the multi-stage circuit to implement the bias voltage is the time between time t1 and time t4.

[0084] In contrast, the second dashed line 908 shows an alternative transition from the first gridded voltage directly to the bias voltage using a multi-stage circuit having the architecture disclosed herein. This alternative transition, even though it has some advantages, is less repeatable (more dependent on circuit (component tolerances) and environmental (cable length) variability) and includes simultaneous transitions of the retrace level and the 1 kV level (involving additional perturbations to the bias voltage and requiring more complex control). The second alternative transition from the first gridded voltage directly to the bias voltage (without transitioning through a common voltage) can be performed using an alternative circuit having a different architecture and not using a multi-stage circuit having the architecture disclosed herein (but with higher constraints on the electronic components).

[0085] Reference now Fig.12 , the second exemplary timing diagram 1200 shows the Figure 5 The first control circuit 502 generates a first transition of the voltage from a first gridded voltage at which the unipolar cathode of the interventional imaging system is turned off to a second bias voltage at which the cathode is turned on, without using the above reference Figure 7An alternative switching control strategy is described. During the first transition, the stages 510-517 of the first control circuit 502 are first sequentially turned off in a continuous order, and then the high-precision voltage source stage of the second control circuit 504 is turned on. The timing diagram 1200 includes three parts that share a common horizontal axis showing time, wherein the time points of interest during the transition are shown by vertical short dashed lines. The first transition has two parts, including a first part from time t1 to time t8, during which the first voltage generated by the first control circuit 502 is reduced and the second control circuit 504 does not generate a voltage, and a second part from time t8 to time t9, during which the first control circuit 502 does not generate a voltage and the second control circuit 504 generates a second bias voltage. In various embodiments, times t0-t9 occur at regular intervals with equal durations. For example, the equal duration can be 3μs per step (this depends on the transition duration requirements and the load (e.g., the cable between the electronic device and the tube)). It should be understood that in order to Figures 12 to 15 For purposes of this disclosure, a decrease in voltage refers to a decrease in the absolute value of the voltage, and an increase in voltage refers to an increase in the absolute value of the voltage.

[0086] The first portion 1202 shows the change in the combined voltage generated by the voltage sources (e.g., voltage source 520 and / or voltage source 570) of the switch unit 500 within the transition. The first portion 1202 includes a first curve 1210 indicating the step output voltage (referring to the command voltage generated by the switch unit 500 at different time points) and a second curve 1212 indicating the circuit output voltage (referring to the actual voltage generated at the cathode of the interventional imaging system (e.g., at the bias / gate electrode 550) at different time points due to the command voltage). The vertical axis of the first portion 1202 shows voltage.

[0087] The second portion 1204 shows the change in voltage generated at the capacitor (e.g., capacitor 521) of each stage of the first control circuit 502 during the first transition over time. The first curve 1220 shows the first charge generated at the first capacitor 521 of the first stage 510; the second curve 1221 shows the second charge generated at the second capacitor 521 of the second stage 511; the third curve 1222 shows the third charge generated at the third capacitor 521 of the third stage 512; and so on, until the eighth curve 1227 shows the eighth charge generated at the eighth capacitor 521 of the eighth stage 517. The vertical axis of the second portion 1204 shows voltage. The voltage contribution of the second control circuit 504 is not shown in the second portion 1204.

[0088] The third section 1206 indicates the engagement of each stage of the switch cell 500 (including the high-precision voltage source stage of the second control circuit 504 that generates the bias voltage) during the transition toward the bias voltage. Each stage can be engaged or bypassed. For example, when a first configuration of the switches of the stage (e.g., switches 522 and 524) connects the voltage source 520 of the stage to a circuit including the bias / gate electrode 550, the stage can be engaged, whereby the voltage contribution to the electrode voltage is the (negative) output voltage of the voltage source 520. When the second configuration of the switches bypasses the voltage source, the stage can be bypassed, whereby the voltage contribution to the electrode voltage is 0V.

[0089] Specifically, the first level curve 1230 indicates whether the first level 510 is engaged; the second level curve 1231 indicates whether the second level 511 is engaged; the third level curve 1232 indicates whether the third level 512 is engaged; the fourth level curve 1233 indicates whether the fourth level 513 is engaged; the fifth level curve 1234 indicates whether the fifth level 514 is engaged; the sixth level curve 1235 indicates whether the second level 515 is engaged; the seventh level curve 1236 indicates whether the seventh level 516 is engaged; and the eighth level curve 1237 indicates whether the eighth level 517 is engaged. The ninth level curve 1238 indicates whether the high-precision voltage source stage of the second control circuit 504 is engaged.

[0090] At time t0, the cathode is gridded and the maximum voltage of the interventional imaging system (e.g., -8 kV) is applied, as indicated by curves 1210 and 1212 of the first portion 1202. All stages are engaged, as indicated by the third portion 1206. Between times t1 and t8, the stages of the first control circuit 502 are bypassed in a continuous sequence, as indicated by curves 1230-1237 of the third portion 1206. At time t1, the first stage indicated by curve 1220 is bypassed; at time t2, the second stage indicated by curve 1221 is bypassed; at time t3, the third stage indicated by curve 1222 is bypassed; and so on, until time t8, when all stages 510-517 of the first control circuit are bypassed. At time t9, the high precision voltage source stage of the second control circuit 504 is engaged, as indicated by curve 1238 of the third portion 1206. When the high precision voltage source stage is engaged, the voltage generated by the switch cell 500 increases to a second bias voltage, as shown by curves 1210 and 1212 of the first portion 1202 .

[0091] However, as shown in the second portion 1204, the sequential shutdown of the stage generates an increased voltage imbalance between the stages. If the sequence of operations is continuous (stage 510, then stage 511, then stage 512, until stage 517), the first stage to be bypassed will remain at its initial voltage value each time another stage is bypassed, and the last stage to be bypassed will experience a voltage increase each time another stage is bypassed, potentially causing failure of the board. As indicated in the second portion 1204, as the voltage sources of the curves 1220-1227 are shut down in a continuous sequence, the voltage at the capacitor 521 of each subsequent stage increases. Therefore, the voltage generated at the eighth capacitor indicated by the eighth curve 1227 may exceed the threshold voltage, wherein the eighth stage and / or other components of the switch unit 500 may be damaged.

[0092] Specifically, at time t1, the first stage 510 is bypassed, and curve 1220 shows that the voltage generated at the capacitor 521 of the first stage (but not applied to the cathode) remains at 1.00 kV. At time t2, the second stage 511 is bypassed, and curve 1221 shows that the voltage generated at the capacitor 521 of the second stage increases to 1.03 kV due to the cable capacitance. At time t3, the third stage 512 is bypassed, and curve 1222 shows that the voltage generated at the capacitor 521 of the third stage increases to 1.07 kV. In this way, the voltage generated at each capacitor 521 of each of the stages 510-517 of the first control circuit increases incrementally as each stage is bypassed until time t8, when curve 1227 shows that the voltage generated at the capacitor 521 of the last stage 517 increases to above 1.15 kV, which may exceed the threshold voltage of the stage and cause damage to the stage. For example, one or both of switches 522 and 524 of the final stage 517 may be damaged.

[0093] like Figure 7 As described in method 700 of , a similar situation occurs during the second transition when the cathode is turned off (e.g., after performing an X-ray exposure). During the second transition, the high-precision voltage source stage of the second control circuit 504 is turned off, thereby reducing the second bias voltage generated by the switch unit 500 to the common voltage. If the stages 510-517 of the first control circuit 502 are then engaged in a continuous ordered sequence to generate the first gridded voltage, a voltage imbalance may also occur, such as Fig.13 shown.

[0094] Fig.131 is a third exemplary timing diagram 1300 illustrating the second transition. The timing diagram 1300 includes three portions that share a common horizontal axis showing time, wherein time points of interest during the second transition are shown by vertical dashed lines. The transition has two portions, including a first portion from time t1 to time t2, during which the second bias voltage generated by the second control circuit 504 is reduced to the common voltage and the first control circuit 502 does not generate a voltage, and a second portion from time t2 to time t9, during which the second control circuit 504 does not generate a voltage and the first control circuit 502 generates a first gridded voltage. As shown in Fig.12 In the example, times t0-t9 may occur at regular intervals.

[0095] The first portion 1302 shows the change of the combined voltage generated by the voltage sources (e.g., voltage source 520 and / or voltage source 570) of the switch unit 500 within the second transition. The first portion 1302 includes a first curve 1310 indicating the step output voltage (referring to the command voltage generated by the switch unit 500 at different time points) and a second curve 1312 indicating the circuit output voltage (referring to the actual voltage generated at the bias / gate electrode 550 at different time points due to the command voltage). The vertical axis of the first portion 1302 shows voltage.

[0096] The second portion 1304 shows the change in time of the voltage generated by the capacitor 521 of each stage of the first control circuit 502 during the second transition. The first curve 1320 shows the voltage generated at the first capacitor 521 of the first stage 510; the second curve 1321 shows the second voltage generated at the second capacitor 521 of the second stage 511; and so on, until the eighth curve 1327, which shows the eighth voltage generated at the eighth capacitor 521 of the eighth stage 517. The vertical axis of the second portion 1304 shows voltage. The voltage contribution of the second control circuit 504 is not shown in the second portion 1304.

[0097] The third portion 1306 indicates the engagement of each stage of the switch cell 500 (including the bias voltage generated by the high precision voltage source stage of the second control circuit 504) during the second transition. Each stage can be engaged or bypassed. The first stage curve 1330 indicates whether the first stage 510 is engaged; the second stage curve 1331 indicates whether the second stage 511 is engaged; the third stage curve 1332 indicates whether the third stage 512 is engaged; and so on, until the eighth stage curve 1337 indicates whether the eighth stage 517 is engaged. The ninth stage curve 1338 indicates whether the high precision voltage source stage of the second control circuit 504 is engaged.

[0098] At time t0, a second bias voltage is applied to the cathode by the second control circuit 504, and no voltage is applied by the first control circuit 502, as indicated by curves 1310 and 1312 of the first portion 1302. All stages of the first control circuit 502 are bypassed, as indicated by curves 1330-1337, and the second control circuit 504 is engaged, as indicated by curve 1338. At time t1, the high precision voltage source 570 of the second control circuit 504 is turned off, and the voltage is reduced to a common voltage (e.g., 0V) at time t2, as shown by curves 1310 and 1312. Between time t2 and t9, the stages 510 to 517 of the first control circuit 502 are engaged in a continuous sequence from stage 517 to stage 510, as indicated by curves 1330-1337 of the third portion 1306. At time t9, the voltage generated by the switch unit 500 approaches the first gridded voltage, as shown by curves 1310 and 1312 of the first portion 1302. The threshold voltage (e.g., Figure 8 ), the cathode is turned off and no x-rays are generated.

[0099] However, as shown in the second portion 1304 and as Fig.12 As seen in the second portion 1204 of , the sequential turning on of the stages generates an increasing voltage imbalance. In this scenario, each time a subsequent stage is engaged, the first stage that is engaged (which is the eighth stage 517) will experience a voltage reduction, potentially causing a failure of a component of the eighth stage 517. As shown in the second portion 1304, the voltage of the capacitor 521 of the eighth stage 517, indicated by curve 1327, decreases as subsequent stages are engaged in a continuous sequence. At time t2, the voltage decreases from 1.00 kV to 0.95 kV due to the second stage being turned on; at time t3, the voltage decreases from 0.95 kV to 0.90 kV due to the third stage being turned on; and so on, until reaching 0.80 kV when the eighth stage 510 is turned on. Stage 510 is not engaged until t9, and therefore the voltage reduction at this stage is very low compared to the eighth stage 517. Due to the imbalance, after the transition, the eighth stage 517 may take longer to reach its command voltage than the first stage 510 to reach its command voltage, thereby generating higher stress on the voltage source 520 of the eighth stage 517, which may cause damage to the switches and / or other components of the eighth stage 517.

[0100] In order to reduce the Fig.12 and Fig.13 The risk of damage caused by the sequential engagement and disengagement of the stages of the first control circuit 502 of the multi-stage switching unit 500 described above, and in order to reduce the amount of energy lost during the first transition and the second transition, Figure 7An alternative control strategy is described in method 700 of , in which the timing of each of the switching stages 510 - 517 is adjusted to ensure that all or most stages achieve equal voltage increases / decreases during respective engagements and disengagements, and the voltage imbalances described above are limited.

[0101] Fig.14 It is shown Fig.12 1400 is a fourth exemplary timing diagram of a first transition of a control system, wherein the stages 510-517 are not disengaged in sequence, but are selectively (e.g., out of sequence) disengaged according to an alternative control strategy. The timing diagram 1400 includes three portions that share a common horizontal axis showing time, wherein interesting time points during the transition are shown by dashed vertical dashed lines. Fig.12 , a first portion 1402 shows changes in a combined voltage generated by a stage of the switch unit 500 (eg, voltage source 520 and / or voltage source 570) during a first transition, including a first curve 1410 indicating a step output voltage and a second curve 1412 indicating a circuit output voltage.

[0102] The second portion 1404 shows the change in voltage generated by the capacitor (e.g., capacitor 521) of each stage of the first control circuit 502 during the first transition over time. The third portion 1406 indicates the engagement of each stage of the switch cell 500 (including the bias voltage generated by the high precision voltage source stage of the second control circuit 504) during the first transition. Each stage can be engaged or bypassed (e.g., disengaged). A set of stage curves 1430-1438 correspond to the voltage generated by the capacitor (e.g., capacitor 521) of each stage of the first control circuit 502 during the first transition. Fig.12 The level curves 1230-1238 of the second control circuit 504 are described. The level curve 1438 indicates whether the high precision voltage source level of the second control circuit 504 is engaged.

[0103] At time t0, the cathode is gridded and a voltage of -8.0 kV is applied, as indicated by curves 1410 and 1412 of first portion 1402. All stages are engaged except for the high precision voltage source stage of second control circuit 504 which is bypassed, as indicated by third portion 1406. Fig.12 , between times t1 and t8, stages 510 to 517 of first control circuit 502 are bypassed, as indicated by curves 1430-1437 of third portion 1406. At time t8, neither first control circuit 502 nor second control circuit 504 generates a voltage, and the cathode receives 0V, as shown by curves 1410 and 1412. At time t9, the second control circuit is engaged, and a second bias voltage is applied to the cathode. However, with Fig.12In contrast, stages 510-517 are bypassed out of order (e.g., order of stages) between t1 and t8. In the depicted embodiment, these stages are bypassed in a series of steps, as follows:

[0104] Step 1: At time t1, the first stage 510 is bypassed (curve 1430).

[0105] Step 2: At time t2, the fourth stage 513 is bypassed (curve 1433).

[0106] Step 3: At time t3, the fifth stage 514 and the sixth stage 515 are bypassed (curves 1434 and 1435), and the fourth stage 513 is engaged (curve 1433).

[0107] Step 4: At time t4, the seventh stage 516 and the eighth stage 517 are bypassed (curves 1436 and 1437), and the fifth stage 514 is engaged (curve 1434).

[0108] Step 5: At time t5, the second stage 511 and the third stage 512 are bypassed (curves 1431 and 1432), and the sixth stage 515 is engaged (curve 1435).

[0109] Step 6: At time t6, the fourth stage 513 and the fifth stage 514 are bypassed (curves 1433 and 1434), and the seventh stage 516 is engaged (curve 1436).

[0110] Step 7: At time t7, the sixth stage 515 and the seventh stage 516 are bypassed (curves 1435 and 1436), and the eighth stage 517 is engaged (curve 1437)

[0111] Step 8: At time t8, the eighth stage 517 (curve 1437) is bypassed. No voltage is generated by the first control circuit 502 or the second control circuit 504.

[0112] Step 9: At time t9, the ninth stage 504 (curve 1438, high precision voltage source stage) is turned on, engaging the second control circuit and applying a second bias voltage to the bias / gate electrode 550 (eg, to turn on the cathode).

[0113] As can be seen in the second portion 1404, due to the application of an alternative control strategy for disengaging stages 510-517, Fig.12 Voltage unbalance ratio Fig.12 At time t1, when the first stage 510 is bypassed, curve 1420 shows that the voltage generated at the capacitor 521 of the first stage (and not applied to the cathode) remains at 1.00 kV, as shown in Fig.12 However, Fig.12 In contrast, when the stages 511-517 are selectively engaged or bypassed between times t2 and t9 according to an alternative control strategy, the incremental increase in voltage at each capacitor 521 of the stages 511-517 is balanced between the capacitors 521. Thus, at time t8, when the first control circuit 502 is not generating a voltage (as shown in the first portion 1402), the curve of the voltage maintained at each capacitor 521 of the stages 511-517 shows an equal final voltage 1422. In the depicted embodiment, the equal final voltage 1422 is below 1.10 kV. The equal voltage 1422 may be below a threshold voltage for causing damage to switches or other components of the stages 511-517, whereby aging and potential sudden part failures due to capacitor voltage imbalance may not occur.

[0114] Fig.15 is a fifth exemplary timing diagram 1500, which illustrates a fifth exemplary timing diagram for Fig.13 During the second transition of (when stages 510-517 are sequentially engaged to achieve the gridded voltage (e.g., to turn off the cathode and stop the generation of x-rays)) an alternative control strategy for engaging stages 510-517 is applied. Fig.13 In contrast, rather than sequentially engaging stages 510-517, stages 510-517 are selectively engaged and / or bypassed according to an alternative control strategy to avoid the above referenced Fig.13 The described voltage imbalance. The timing diagram 1500 includes three parts that share a common horizontal axis showing time, wherein the time points of interest during the second transition are shown by the vertical dashed lines. Fig.13 , the first portion 1402 shows changes in the combined voltage generated by the voltage sources (e.g., voltage source 520 and / or voltage source 570) of the switch unit 500 during the second transition, including a first curve 1510 indicating the step output voltage and a second curve 1512 indicating the circuit output voltage.

[0115] The second portion 1504 shows the change in voltage generated by the capacitor 521 of each stage of the first control circuit 502 during the second transition over time. The third portion 1506 indicates the engagement of each stage of the switch cell 500 (including the bias voltage generated by the high precision voltage source stage of the second control circuit 504) during the second transition. Each stage can be engaged or bypassed. A set of stage curves 1530-1538 corresponds to the Fig.13 The level curve 1538 indicates whether the high precision voltage source level of the second control circuit 504 is engaged.

[0116] At time t0, a bias voltage of approximately -1.2 kV is applied, as indicated by curves 1510 and 1512 of first portion 1502. All stages are bypassed except for the high precision voltage source stage of second control circuit 504 that generates the bias voltage, as indicated by third portion 1506. At time t1, high precision voltage source stage 504 is bypassed. The voltage applied to the cathode is 0 V, as shown by curves 1510 and 1512. As shown in FIG. Fig.13 , between times t2 and t9, stages 510 to 517 of first control circuit 502 are engaged, as indicated by curves 1530-1537 of third portion 1406. Fig.13 In contrast, stages 510-517 are engaged out of sequence between t2 and t9. In the depicted embodiment, the stages are engaged in a series of steps according to an alternative control strategy. In various embodiments, these steps may be combined with the bypass Fig.14 The steps performed during stages 510-517 are shown to be the same, but in reverse order, as follows:

[0117] Step 1: At time t2, the eighth stage 517 (curve 1537) is engaged.

[0118] Step 2: At time t3, the sixth stage 515 and the seventh stage 516 are engaged (curves 1535 and 1536), and the eighth stage 517 is bypassed (curve 1537)

[0119] Step 3: At time t4, the fourth stage 513 and the fifth stage 514 are engaged (curves 1533 and 1534), and the seventh stage 516 is bypassed (curve 1536)

[0120] Step 4: At time t5, the second stage 511 and the third stage 512 are engaged (curves 1531 and 1532), and the sixth stage 515 is bypassed (curve 1535)

[0121] Step 5: At time t6, the seventh stage 516 and the eighth stage 517 are engaged (curves 1536 and 1537), and the fifth stage 514 is bypassed (curve 1534)

[0122] Step 6: At time t7, the fifth stage 514 and the sixth stage 515 are engaged (curves 1534 and 1535), and the fourth stage 513 is bypassed (curve 1433).

[0123] Step 7: At time t8, the fourth stage 513 is engaged (curve 1533).

[0124] Step 8: At time t9, the first stage 510 is engaged (curve 1530).

[0125] As can be seen in the second portion 1504, due to the application of an alternative control strategy for the engagement stages 510-517, Fig.13 By time t9, when the first stage 510 is engaged, curve 1520 shows that the voltage drop generated at the capacitor 521 of the first stage is still very low, as shown in FIG. Fig.13 As shown in curve 1320. However, Fig.13 In contrast, when the stages 511-517 are selectively engaged or disengaged between times t2 and t8 according to an alternative control strategy, the incremental decrease in voltage at each capacitor 521 of the stages 511-517 is balanced between the capacitors 521. Thus, at time t9, when the first control circuit 502 is not generating a voltage (as shown in the first portion 1502), the curve of the voltage maintained at each capacitor 521 of the stages 511-517 shows an equal voltage 1521. In the depicted embodiment, the equal voltage 1521 is approximately 0.90 kV. The voltage at both the first stage 510 and the stages 511-517 experience a further voltage drop after t9 because the voltage applied to the cathode achieves a gridded voltage of -8.0 kV, as described above with reference to FIG. Figure 8 As described (e.g., from line 808 to line 810). Equal voltage 1521 may be below a threshold voltage for causing damage to switches or other components of stages 511-517, whereby aging and potential sudden part failure due to capacitor voltage imbalance may not occur. In this manner, stages 510-517 may be selectively disengaged in a first order to achieve a bias voltage and selectively engaged in a second order to achieve a gridded voltage according to an alternative control strategy, wherein the second order is opposite to the first order.

[0126] It should be understood that Figures 12 to 15 This is for purposes of illustration, and in other embodiments, a different number of stages and / or order of selective engagement / disengagement of the stages may be used without departing from the scope of the present disclosure.

[0127] In various embodiments, these step sizes may be implemented by the interventional imaging system's software according to a protocol for an alternative switching strategy that specifies which of the stages 510-517 are to be engaged at different times during the first transition and the second transition. Fig.16 As shown, protocols can be programmatically joined using a level joining matrix.

[0128] refer to Fig.16 , shows an exemplary level engagement matrix 1600 according to an embodiment, which can be used to generate an optimized protocol for the interventional imaging system referred to herein to achieve the above reference Fig.15 The second transition. The level bonding matrix 1600 includes the corresponding Fig.15The stage engagement matrix 1600 includes nine numbered rows 1602 for step sizes 1-9 of the second transition described. The stage engagement matrix 1600 includes eight numbered columns 1604 corresponding to the stages 510-517 of the first control circuit 502 of the multi-stage switch unit 500. The stages are numbered from eight to one, which means that the first column 1620 represents Fig.15 The eighth level 517; the second column 1622 indicates Fig.15 16; and so on. Thus, at each of the nine steps, the corresponding row 1602 of the level engagement matrix 1600 includes a binary encoding in each cell corresponding to each of the eight levels, indicating whether the corresponding level is engaged or disengaged. In the depicted embodiment, the cell may include a 1 if the corresponding level is engaged, and may include a 0 if the corresponding level is disengaged.

[0129] For example, the first row 1610 includes all zeros, indicating that during the first step, all eight stages are disengaged and none of the stages of the first control circuit 502 are engaged. The second row 1612 includes a one in the first column 1620 and zeros in all other columns, indicating that during the second step, only one of the eight stages (e.g., the eighth stage) is engaged (e.g., switched from bypassing to engaging). The third row 1614 includes a zero in the first column 1620, a one in the second column 1622, a one in the third column 1624, and zeros in all other columns, indicating that during the third step, the eighth stage is disengaged (e.g., switched from engaging to bypassing), and the seventh and sixth stages are engaged. Fourth row 1616 includes a zero in first column 1620, indicating that the eighth stage is maintained disengaged (e.g., maintained bypassed); a zero in second column 1622, indicating that the seventh stage is disengaged; a one in third column 1624, indicating that the sixth stage is maintained engaged (e.g., maintained engaged); a one in fourth column 1626, indicating that the fifth stage is engaged; a one in fifth column 1628, indicating that the fourth stage is engaged; and zeros in all other columns. The remaining cells of the stage engagement matrix 1600 are similarly populated, so that the stage engagement matrix 1600 provides an effective binary (e.g., machine-readable) representation that can be consulted by a software routine of the interventional imaging system, for example, as a lookup table. The software routine can be executed by a processor of the interventional imaging system.

[0130] The technical effect of using a non-continuous control strategy to engage and disengage stages of a control circuit for controlling electrode voltages of an interventional imaging system during transitions between a gridding voltage of the interventional imaging system and a bias voltage of the interventional imaging system is that voltage imbalances between stages can be reduced, thereby reducing the risk of damage to components of the control circuit.

[0131] The present disclosure also provides support for a method for an interventional imaging system, the method comprising: applying a voltage to a gridded electrode of a cathode of the interventional imaging system via a multi-stage switching unit including a first control circuit and a different second control circuit during a first transition of the voltage from a first gridded voltage of the interventional imaging system generated by a first control circuit to a second bias voltage of the interventional imaging system generated by a second control circuit; selectively bypassing a plurality of stages of the first control circuit sequentially in a first non-continuous order to reduce the voltage from the first gridded voltage to a common voltage of the interventional imaging system; and selectively engaging a plurality of stages of the first control circuit sequentially in a second non-continuous order to increase the voltage from the common voltage to the first gridded voltage during a second transition of the voltage from a second bias voltage generated by the second control circuit to a first gridded voltage generated by the first control circuit. In a first example of the method, the cathode is a unipolar cathode, and both of the first gridded voltage and the second bias voltage are negative voltages. In a second example of the method optionally including the first example, the drive electronics of the unipolar cathode are connected by a cable having a length greater than 40 meters. In a third example of the method optionally including one or both of the first and second examples, each of the multiple stages of the first control circuit includes a -1kV voltage source, a capacitor, and at least two switches to bypass or negatively connect the -1kV voltage source to the cathode, and the second control circuit includes a high-precision voltage source capable of generating up to 1.2kV with an accuracy of + / -50V, a capacitor, and at least two switches to bypass or negatively connect the high-precision voltage source to the cathode. In a fourth example of the method optionally including one or more or each of the first to third examples, the first gridded voltage is -8kV relative to the common voltage, and the second bias voltage is between 0kV and -1.2kV relative to the common voltage. In a fifth example of the method optionally including one or more or each of the first to fourth examples, the second non-continuous order is the inverse of the first non-continuous order. In a sixth example of the method that optionally includes one or more or each of the first to fifth examples, selectively sequentially bypassing multiple stages of the first control circuit in a first non-contiguous order includes executing a first step sequence, wherein during each step in the first step sequence, at least one stage of the multiple stages is bypassed, and during at least one step in the first step sequence, a previously bypassed stage is engaged, and selectively sequentially engaging multiple stages of the first control circuit in a second non-contiguous order includes executing a second step sequence, wherein during each step in the second step sequence, at least one stage of the multiple stages is engaged, and during at least one step in the second step sequence, a previously engaged stage is bypassed.In a seventh example of the method, which optionally includes one or more or each of the first to sixth examples, the method further includes: selectively bypassing a plurality of stages of the first control circuit in a first non-contiguous order sequentially based on a first protocol generated according to a first stage engagement matrix stored in a memory of the interventional imaging system; and selectively engaging a plurality of stages of the first control circuit in a second non-contiguous order sequentially based on a second protocol generated according to a second stage engagement matrix stored in the memory, wherein the first stage engagement matrix and the second stage engagement matrix indicate when each of the plurality of stages will be engaged and when each of the plurality of stages will be bypassed. In an eighth example of the method, which optionally includes one or more or each of the first to seventh examples, the first stage engagement matrix and the second stage engagement matrix indicate when each of the plurality of stages will be engaged and when each of the plurality of stages will be bypassed via binary coding, wherein one indicates that the stage will be engaged and zero indicates that the stage will be bypassed. In a ninth example of the method, which optionally includes one or more or each of the first to eighth examples, the first protocol and the second protocol are optimized to reduce voltage imbalances between stages in the plurality of stages.

[0132] The present disclosure also provides support for an interventional imaging system, which includes: an X-ray source, which includes a unipolar cathode; a multi-stage switching unit, which includes a first control circuit and a second control circuit, the first control circuit being configured to generate a first gridded voltage at a gridded electrode of the unipolar cathode via multiple stages of the multi-stage switching unit, and the second control circuit being configured to generate a second bias voltage at the gridded electrode; and a controller, which is operably connected to the X-ray source and is configured to: when transitioning from the gridded voltage to the bias voltage, selectively bypass the multiple stages of the first control circuit in a first non-continuous order to reduce the voltage applied to the gridded electrode, and when transitioning from the bias voltage to the gridded voltage, selectively engage the multiple stages of the first control circuit in a second non-continuous order to increase the voltage applied to the gridded electrode, the second non-continuous order being the inverse of the first non-continuous order. In a first example of the system, both of the first gridding voltage and the second bias voltage are negative voltages relative to a common voltage of the interventional imaging system, and the drive electronics of the unipolar cathode are connected by a cable having a length greater than 40 meters. In a second example of the system that optionally includes the first example, each of the plurality of stages of the first control circuit includes a -1 kV voltage source, a capacitor, and at least two switches to bypass or negatively connect the -1 kV voltage source to the unipolar cathode, and the second control circuit includes a high precision voltage source capable of generating up to 1.2 kV with an accuracy of + / -50 V, a capacitor, and at least two switches to bypass or negatively connect the high precision voltage source to the unipolar cathode. In a third example of the system, which optionally includes one or both of the first example and the second example, the controller is further configured to: selectively bypass multiple stages of the first control circuit sequentially in a first non-continuous order by bypassing at least one stage of the multiple stages at each step in the first step sequence and engaging the previously bypassed stage during at least one step in the first step sequence; and selectively engage multiple stages of the first control circuit sequentially in a second non-continuous order by engaging at least one stage of the multiple stages at each step in the second step sequence and bypassing the previously engaged stage during at least one step in the second step sequence. In a fourth example of the system that optionally includes one or more or each of the first to third examples, the controller is further configured to: selectively bypass multiple stages of the first control circuit sequentially in a first non-sequential order based on a first protocol generated from a first-level engagement matrix stored in a memory of the interventional imaging system; and selectively engage multiple stages of the first control circuit sequentially in a second non-sequential order based on a second protocol generated from a second-level engagement matrix stored in the memory, wherein the first-level engagement matrix and the second-level engagement matrix indicate when each of the multiple stages will be engaged and when each of the multiple stages will be bypassed.In a fifth example of the system optionally including one or more or each of the first to fourth examples, the first stage engagement matrix and the second stage engagement matrix indicate when each of the multiple stages will be engaged and when each of the multiple stages will be bypassed via binary coding, wherein one indicates engaging the relevant stage and zero indicates bypassing the stage. In a sixth example of the system optionally including one or more or each of the first to fifth examples, the first protocol and the second protocol are optimized to reduce voltage imbalances between the stages of the multiple stages. In a seventh example of the system optionally including one or more or each of the first to sixth examples, under a first condition in which the multiple stages of the first control circuit are sequentially bypassed in a continuous order rather than in a first non-continuous order, the voltage imbalance between the stages causes the voltage at the stage to exceed a threshold voltage, which is a voltage that can cause damage to at least one component of the stage, and under a second condition in which the multiple stages of the first control circuit are sequentially bypassed in a first non-continuous order, the voltage imbalance does not cause the voltage at the stage to exceed the threshold voltage.

[0133] The present disclosure also provides support for a method for an interventional imaging system, the method comprising: in response to receiving an instruction to turn on a cathode of the interventional imaging system: retrieving a first-level engagement matrix from a memory of the interventional imaging system, the first-level engagement matrix comprising a binary code indicating a first non-continuous order of multiple levels of a first control circuit of a multi-level switch unit for bypassing and / or engaging the interventional imaging system; generating a first protocol for controlling the first control circuit based on the first-level engagement matrix; reducing a voltage of a gridded electrode supplied to the cathode from a first gridded voltage of the interventional imaging system to a common voltage of the interventional imaging system according to the first protocol; and increasing the voltage from the common voltage to a second bias voltage of the interventional imaging system via a second control circuit of the multi-level switch unit, and in response to receiving an instruction to turn off the cathode: increasing the voltage from the common voltage to the second bias voltage of the interventional imaging system; generating a second protocol for controlling the first control circuit based on a second non-continuous order, the second non-continuous order being the inverse of the first non-continuous order; reducing the voltage from the second bias voltage to the common voltage via the second control circuit; and increasing the voltage from the common voltage to the first gridded voltage according to the second protocol. In a first example of the method, the second non-sequential order is indicated by a binary encoding of a second level engagement matrix stored in a memory.

[0134] When introducing the elements of various embodiments of the present disclosure, the articles "one", "a kind of" and "the" are intended to mean that there are one or more such elements. The terms "first", "second", etc. do not represent any order, amount or importance, but are used to distinguish one element from another element. The terms "include", "comprises", and "have" are intended to be inclusive, and mean that additional elements may also exist in addition to the listed elements. As used herein, the terms "connected to", "coupled to", etc., an object (e.g., material, element, structure, member, etc.) may be connected to or coupled to another object, regardless of whether the one object is directly connected or coupled to another object, or whether there are one or more intervening objects between the one object and another object. In addition, it should be understood that reference to "an embodiment" or "embodiment" of the present disclosure is not intended to be interpreted as excluding the existence of additional embodiments that are also combined with the cited features.

[0135] In addition to any previously indicated modifications, those skilled in the art may devise numerous other variations and alternative arrangements without departing from the spirit and scope of the present specification, and the appended claims are intended to cover such modifications and arrangements. Therefore, although the information has been described in detail and in detail as described above in conjunction with what are currently considered to be the most practical and preferred aspects, it will be apparent to those of ordinary skill in the art that many modifications, including but not limited to form, function, mode of operation, and use, may be made without departing from the principles and concepts set forth herein. Likewise, as used herein, the examples and embodiments are meant to be illustrative in all respects and should not be construed as limiting in any way.

Claims

1. A method (700) for an interventional imaging system, the method (700) comprising: applying a voltage to a gridded electrode of a cathode of the interventional imaging system via a multi-stage switching unit, the multi-stage switching unit comprising a first control circuit and a different second control circuit; selectively bypassing a plurality of stages of the first control circuit sequentially in a first non-sequential order to reduce the voltage from the first gridded voltage to a common voltage for the interventional imaging system during a first transition of the voltage from a first gridded voltage for the interventional imaging system generated by the first control circuit to a second bias voltage for the interventional imaging system generated by the second control circuit (704); as well as During a second transition of the voltage from the second bias voltage generated by the second control circuit to the first gridded voltage generated by the first control circuit, selectively and sequentially engaging the plurality of stages of the first control circuit in a second non-sequential order to increase the voltage from the common voltage to the first gridded voltage (712).

2. The method (700) of claim 1, wherein the cathode is a unipolar cathode and both of the first gridding voltage and the second bias voltage are negative voltages.

3. The method (700) of claim 2, wherein the drive electronics of the unipolar cathodes are connected by a cable having a length greater than 40 meters.

4. The method (700) of claim 1, wherein: Each of the plurality of stages of the first control circuit includes a -1 kV voltage source, a capacitor, and at least two switches for bypassing or negatively connecting the -1 kV voltage source to the cathode; and The second control circuit includes a high precision voltage source capable of generating up to 1.2 kV with an accuracy of + / -50 V, a capacitor, and at least two switches to bypass or negatively connect the high precision voltage source to the cathode.

5. The method (700) of claim 4, wherein: The first gridding voltage is -8 kV relative to the common voltage, and the second bias voltage is between 0 kV and -1.2 kV relative to the common voltage. The method of claim 1 , wherein the second non-sequential order is the inverse of the first non-sequential order.

7. The method (700) of claim 1, wherein: selectively sequentially bypassing the plurality of stages of the first control circuit in the first non-sequential order comprises executing a first step sequence wherein during each step in the first step sequence at least one stage of the plurality of stages is bypassed and during at least one step in the first step sequence a previously bypassed stage is engaged; and Selectively sequentially engaging the plurality of stages of the first control circuit in the second non-sequential order includes executing a second step sequence, wherein during each step in the second step sequence, at least one stage of the plurality of stages is engaged, and during at least one step in the second step sequence, a previously engaged stage is bypassed.

8. The method (700) of claim 1, further comprising: selectively sequentially bypassing the plurality of stages of the first control circuit in the first non-sequential order based on a first protocol generated according to a first stage engagement matrix stored in a memory of the interventional imaging system; as well as selectively sequentially engaging the plurality of stages of the first control circuit in the second non-sequential order based on a second protocol generated according to a second stage engagement matrix stored in the memory (704); Wherein the first stage engagement matrix and the second stage engagement matrix indicate when each of the plurality of stages is to be engaged and when each of the plurality of stages is to be bypassed.

9. The method (700) of claim 8, wherein the first level engagement matrix and the second level engagement matrix indicate when each of the plurality of levels will be engaged and when each of the plurality of levels will be bypassed via binary encoding, wherein one indicates that the level will be engaged and zero indicates that the level will be bypassed.

10. The method (700) of claim 8, wherein the first protocol and the second protocol are optimized to reduce voltage imbalances between stages in the plurality of stages.

11. An interventional imaging system (600), comprising: An X-ray source, the X-ray source comprising a unipolar cathode (62); A multi-stage switch unit (300, 500, 500, 400), the multi-stage switch unit comprising: a first control circuit (502), the first control circuit being configured to generate a first gridded voltage at a gridded electrode (612, 550, 58, 550) of the unipolar cathode (62) via a plurality of stages (510) of the multi-stage switch unit (300, 500, 500, 400); and a second control circuit (504), the second control circuit being configured to generate a second bias voltage at the gridded electrode (612, 550, 58, 550); and a controller (620, 66) operably connected to the x-ray source and configured to: selectively bypassing the plurality of stages (510) of the first control circuit (502) sequentially in a first non-sequential order to reduce the voltage applied to the gridded electrode (612, 550, 58, 550) when transitioning from the gridded voltage to the bias voltage; and The plurality of stages (510) of the first control circuit (502) are selectively engaged sequentially in a second non-sequential order to increase the voltage applied to the gridded electrodes (612, 550, 58, 550) when transitioning from the bias voltage to the gridded voltage, the second non-sequential order being the inverse of the first non-sequential order.

12. The interventional imaging system (600) of claim 11, wherein both of the first gridding voltage and the second bias voltage are negative voltages relative to a common voltage of the interventional imaging system (100, 600), and the drive electronics of the unipolar cathode (62) are connected via a cable (650) having a length greater than 40 meters.

13. The interventional imaging system (600) of claim 11, wherein: Each of the plurality of stages (510) of the first control circuit (502) comprises a -1 kV voltage source (520), a capacitor (521), and at least two switches (522, 524) for bypassing or negatively connecting the -1 kV voltage source (520) to the unipolar cathode (62); and The second control circuit (504) includes a high precision voltage source (570) capable of generating up to 1.2 kV with an accuracy of + / -50 V, a capacitor (571), and at least two switches (562, 563) for bypassing or negatively connecting the high precision voltage source (570) to the unipolar cathode (62).

14. The interventional imaging system (600) of claim 13, wherein the controller (620, 66) is further configured to: selectively bypassing the plurality of stages (510) of the first control circuit (502) sequentially in the first non-sequential order by bypassing at least one stage (510) of the plurality of stages (510) at each step in the first sequence of first steps (904) and engaging a previously bypassed stage (510) during at least one step in the first sequence of first steps (904); and The plurality of stages (510) of the first control circuit (502) are selectively sequentially engaged in the second non-sequential order by engaging at least one stage (510) of the plurality of stages (510) at each step in a second step sequence and bypassing a previously engaged stage (510) during at least one step in the second step sequence.

15. The interventional imaging system (600) of claim 14, wherein the controller (620, 66) is further configured to: selectively sequentially bypassing the plurality of stages (510) of the first control circuit (502) in the first non-sequential order based on a first protocol generated from a first stage engagement matrix (1600) stored in a memory (622) of the interventional imaging system (100, 600); and selectively sequentially engaging the plurality of stages (510) of the first control circuit (502) in the second non-sequential order based on a second protocol generated from a second stage engagement matrix (1600) stored in the memory (622); Wherein the first stage engagement matrix (1600) and the second stage engagement matrix (1600) indicate when each stage (510) of the plurality of stages (510) is to be engaged and when each stage (510) of the plurality of stages (510) is to be bypassed.

16. The interventional imaging system (600) of claim 15, wherein the first level engagement matrix (1600) and the second level engagement matrix (1600) indicate via binary coding when each of the multiple levels (510) will be engaged and when each of the multiple levels (510) will be bypassed, wherein one indicates engaging the relevant level (510) and zero indicates bypassing the level (510).

17. The interventional imaging system (600) of claim 15, wherein the first protocol and the second protocol are optimized to reduce voltage imbalances between stages (510) in the plurality of stages (510).

18. The interventional imaging system (600) of claim 17, wherein: Under a first condition in which the plurality of stages (510) of the first control circuit (502) are sequentially bypassed in a sequential order but not in the first non-sequential order, the voltage imbalance between the stages causes a voltage at a stage (510) to exceed a threshold voltage, the threshold voltage being a voltage capable of causing damage to at least one component of the stage (510); Under a second condition in which the plurality of stages (510) of the first control circuit (502) are sequentially bypassed in the first non-sequential order, the voltage imbalance does not cause the voltage at the stage (510) to exceed the threshold voltage.

19. A method (700) for use in an interventional imaging system, the method comprising: In response to receiving an instruction to turn on a cathode of the interventional imaging system (702): retrieving a first stage engagement matrix from a memory of the interventional imaging system, the first stage engagement matrix comprising a binary code indicating a first non-sequential order of a plurality of stages of a first control circuit of a multi-stage switch unit of the interventional imaging system for bypassing and / or engaging; generating a first protocol for controlling the first control circuit based on the first level bonding matrix; reducing a voltage supplied to a gridded electrode of the cathode from a first gridded voltage of the interventional imaging system to a common voltage of the interventional imaging system according to the first protocol (704); as well as increasing the voltage from the common voltage to a second bias voltage of the interventional imaging system via a second control circuit of the multi-stage switch unit (706); as well as In response to receiving an instruction to close the cathode (708): generating a second protocol for controlling the first control circuit based on a second non-sequential order, the second non-sequential order being the inverse of the first non-sequential order; reducing the voltage from the second bias voltage to the common voltage via the second control circuit (710); and The voltage is increased from the common voltage to the first gridded voltage according to the second protocol (712).

20. The method (700) of claim 19, wherein the second non-sequential order is indicated by a binary encoding of a second level stitching matrix stored in the memory.

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