X-ray scanning control system
By connecting all gates to a single power supply and directly controlling the anode current, the problem of excessive long conversion time and insufficient deactivation time in the X-ray scanning system is solved, and a significant shortening of the scanning time is achieved.
Patent Information
- Application Number
- CN202280099930.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2022-09-12
- Publication Date
- 2025-04-25
AI Technical Summary
When existing X-ray scanning systems quickly switch multiple X-ray emitters, they face the problem of the anode current activation conversion time and the deactivation time are not short enough, which affects the scanning efficiency.
By connecting all gates to the positive terminal of a single power supply and grounding the negative terminal of the power supply, a method of directly controlling the anode current is adopted, using closed-loop control and PID controller to quickly charge the parasitic capacitors to reduce downtime.
The activation conversion time of each transmitter is achieved, the deactivation time is significantly reduced, and the scanning time is reduced by about 25%, while avoiding the need for calibration of individual cathode current demand values for multiple X-ray emitters.
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Figure CN119896035A_ABST
Abstract
Description
Technical Field
[0001] As the title of the invention indicates, the present invention relates to an X-ray scanning control system, which consists of a plurality of emitters and at least one X-ray receiver, wherein the emitters and the receiver are arranged so that an object is placed between the plurality of emitters and the at least one receiver to capture an image of the object, wherein only one emitter can be transmitting at a given moment to avoid distortion of the obtained image, so that once the transmission of one X-ray emitter is carried out and completed, the transmission of another emitter starts, and the next transmission does not start until the previous transmission is completed or deactivated.
[0002] The present invention is characterized by a special design and configuration of each element being part of the scanning system, in particular of each element of the activation and deactivation system of each X-ray emitter, to increase the scanning speed.
[0003] By means of the control system, 3D scanning and / or tomosynthesis or any other type of scanning may be performed.
[0004] The present invention therefore belongs to the field of control devices, in particular to the field of control devices for use in X-ray machines. Background Art
[0005] X-ray images are one of the most commonly used techniques for visualizing the internal structure of an object for various applications such as healthcare, security control, non-destructive testing, etc. One of the known limitations of flat 2D images is the presence of structural noise in the image caused by the overlap of several objects (or tissues in medical images) in the X-ray beam. To avoid this effect, several techniques (such as computed tomography and tomosynthesis) are used to create 3D or multi-layer images of an object.
[0006] These methods require repeated imaging of the object of interest from a variety of angles, typically ranging from 15° (in the case of tomosynthesis) to 360° (in the case of computed tomography). Typically, this variation is achieved by rotation (or other geometric displacement) of the X-ray source around the object with repeated cyclic imaging processes for subsequent processing and reconstruction of 3D or multi-slice images.
[0007] The invention disclosed herein is based on another principle: using multiple X-ray sources positioned in a predetermined manner, rapidly changing between them, to obtain a predetermined number of images, which are subsequently processed to reconstruct a 3D or multi-layer image.
[0008] To make this type of 3D or multi-layer image, very fast switching between multiple X-ray sources is required, typically in the range of 5μs to 15μs. This is usually done using a cold cathode X-ray tube, which typically includes an anode, cathode, and emission control grid.
[0009] Furthermore, and in a complementary manner, scanning systems face several issues inherent to the physics of X-ray emitters:
[0010] The grid is positively biased at several kV (between 0.5kV and 10kV) relative to the cathode and must be controlled from ground;
[0011] The high voltage supply that powers the anode is approximately 20KV to 180KV and must also be referenced to ground so that the anode current can be measured quickly, easily and safely.
[0012] The first solution of the prior art is as follows Figures 1 to 5 shown.
[0013] Figure 1 A series of X-ray emitter-receiver groups are shown, all of which share the same power supply (Aps) connected to each anode (A), all grids (G) are grounded, and each cathode (K) has a current controller and a power supply of several kV; therefore, there are as many current controllers and power supplies (Gps) as there are emitter-receiver groups (1, 2, ..., 100).
[0014] Figure 1 The solution shown consists in arranging all gates to ground, thereby requiring as many current controllers and power supplies as transmitter-receiver sets.
[0015] This is achieved by directly controlling the cathode current (IK) using a cathode current demand value (DIK) that has been pre-calibrated in a separate process, which in turn controls the anode current (IA) that produces the X-ray emission.
[0016] Figure 2 A block diagram of this prior art embodiment is shown. When the cathode current demand value (DIK) obtained by a previous calibration process is used to obtain the desired value of the anode current (IA), the cathode current demand value (DIK) is used as a reference for the controller (CLR1). The output of the controller (CLR1) attacks the gate of a high voltage transistor (Q1) (Mosfet or IGBT), which controls the cathode current (IK) according to the current demand value (DIK) at its input. The controller (CLR1) uses the cathode current (IK) as a feedback value for the transistor gate current control (Q1).
[0017] The controller (CLR1) is preferably of the integrator type, but may be of another similar type.
[0018] exist Figure 3In the , a very decisive factor that has to be taken into account is shown in detail. This decisive factor is the parasitic capacitance (CGK) between the grid and the cathode of the X-ray tube. Typical values of this capacitance are between 15pF and 30pF; although this seems to be an almost negligible value, since it usually has to be charged between 0.5kV and 10kV in a typical time of between 5μs and 15μs, it requires a constant load current of 10mA to 100mA. Considering that the typical maximum value of the anode current (IA) is 100mA, the value of said parasitic capacitance is completely not negligible.
[0019] Figure 3 It is also shown how a large portion of the cathode current (IK) constitutes the current (IC) that is directed to charging the parasitic capacitance (CGK) between the gate and cathode, which steals current from the gate (IG), causing the anode to also deliver a lower anode current (IA).
[0020] Figure 4 It shows how the controller (CLR1) perfectly controls the cathode current (IK) with a switching time of 5 μs, as required by the 3D scanner.
[0021] However, in Figure 5 In Figure 1, we see what happens to the anode current (IA) due to the parasitic capacitance (CGK) between the gate and cathode.
[0022] The rise or activation transition time of the anode current (IA) is slower than expected because some of the gate current (IG) has been directed to the parasitic capacitance (CGK) between the gate and cathode. The expected anode current (IA) value will not be reached until the parasitic capacitance (CGK) between the gate and cathode is fully charged, making the activation transition time much longer than expected.
[0023] On the other hand, the falling transition time or deactivation time is expected to be 5μs to 15μs because this is the response time of the controller (CLR1) and transistor (Q1), which directly cuts off the total current of the circuit, including the anode current (IA).
[0024] This implementation inherently raises four important questions:
[0025] 1. For each of the multiple X-ray emitters that make up the 3D scanner, the individual current demand value (DIK) is calibrated as necessary.
[0026] 2. Maintain the accuracy status of each X-ray transmitter regardless of its degradation due to usage patterns and time.
[0027] 3. Due to the parasitic capacitance (CGK) between the gate and cathode, the activation transition time or rise time of the anode current (IA) is shortened.
[0028] 4. Due to the response time of the controller (CLR1), the transient deactivation time or fall time of the anode current (IA) is shortened.
[0029] Therefore, the object of the present invention is to develop an X-ray scanning control system which overcomes the above mentioned problems by means of a scanning control system such as described below, the essence of which is contained in claim 1.
[0030] Another solution is Figure 6 As shown, this involves connecting all gates to the positive terminal of a single power supply, while grounding the negative terminal of said power supply, so that the number of independent current controllers is only as many as the number of transmitter-receiver groups, all of which have only one power supply. Summary of the invention
[0031] The object of the invention is essentially contained in the independent claim, different embodiments are contained in the dependent claims.
[0032] The object of the present invention is to control an X-ray scanning system by directly controlling the anode current through gate control, the system comprising a plurality of emitters and at least one receiver, the emitters and the receiver being arranged opposite to each other, wherein only one emitter can be transmitting at a specific moment, that is, once the transmission of one X-ray emitter is carried out and completed, the transmission of another emitter starts, and the next transmission does not start until the transmission is finished or deactivated.
[0033] By means of the control system, 3D scanning and / or tomosynthesis or any other type of scanning may be performed.
[0034] The geometry adopted by the plurality of transmitters and the at least one receiver may be any known geometry and is not limiting in any case, such that the object to be scanned is located between the plurality of transmitters and the at least one receiver.
[0035] In short, the system is a scanning system with multiple X-ray emission sources, wherein the geometrical shape in which the multiple emission sources are arranged is not restricted.
[0036] Therefore, the emission time of each emitter must be extremely short, on the order of 5μs to 15μs. Likewise, the activation and deactivation transition times of the emitters must be as short as possible, always less than 5μs. To achieve this, the fastest and most efficient way is to use a linear controller for the gate current, which in turn is controlled and corrected by real-time measurement of the anode current.
[0037] The solution proposed by the present invention is to connect all the gates to the positive terminal of a single power supply, while connecting the negative terminal of said power supply to ground, so there are as many independent current controllers as there are transmitter-receiver groups, but with only one power supply.
[0038] Furthermore, the main idea of the present invention is to directly control the anode current instead of the cathode current to avoid the above-mentioned harmful effects.
[0039] To this end, the control system has a controller that uses as reference the current demand of the anode that produces the X-ray emission, and the feedback to the controller is the actual current of the anode. This control avoids the need to calibrate the current demand of the cathode based on the anode current.
[0040] The controller keeps each transmitter in perfect accuracy at all times through closed-loop control, eliminating the need to recalibrate transmitters due to transmitter degradation caused by usage type and time.
[0041] The controller is preferably of the PID type, but another type of control may also be applied.
[0042] The integral portion of the controller corrects errors and adjusts the accuracy of the anode current (IA), while the derivative portion enables the parasitic capacitance between the gate and cathode to charge faster, greatly improving the activation transition time or rise time.
[0043] Furthermore, to improve the speed of activation and deactivation times, the deactivation time or fall time is reduced by applying a signal to the buffer to short the gate of the control transistor without waiting for a response from the CLR1 controller.
[0044] In addition, as a complement and supplement, the CLR1 controller can apply an overcurrent during the rise time of the cathode current to quickly charge the parasitic capacitance between the gate and the cathode. When the CGK capacitor is fully charged and in a steady state, the overcurrent stops.
[0045] The above method achieves:
[0046] Avoiding the need for calibration of individual cathode current demand values (DIK) for each of the multiple X-ray emitters;
[0047] Maintain the accuracy status of each X-ray emitter;
[0048] Shorten activation transition time or rise time;
[0049] The deactivation transition time is shortened, which significantly reduces the scan time by about 25% relative to the time required by the current controller, without shortening the activation time and deactivation time.
[0050] Unless otherwise specified, all technical and scientific elements used in this specification have the meanings commonly understood by those skilled in the art to which the invention belongs. In the practice of the present invention, methods and materials similar or equivalent to those described in this specification can be used.
[0051] In the specification and claims, the word "comprise" and its variations are not intended to exclude other technical features, additions, components or steps. For those skilled in the art, other purposes, advantages and features of the present invention will be inferred in part from the specification and in part from the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS
[0052] To supplement the description herein, and to help better understand the characteristics of the invention, according to a preferred practical embodiment of the invention, said specification is accompanied as an integral part thereof by a set of drawings, in which the following are given in an illustrative and non-limiting manner:
[0053] Figure 1 One prior art embodiment is shown where the gate is grounded, requiring as many power supplies and current controllers as transmitter-receiver sets.
[0054] Figure 2 Shows Figure 1 A block diagram of cathode current control (IK) of a prior art embodiment is shown.
[0055] Figure 3 The parasitic capacitance (CGK) between the grid and cathode of an X-ray tube is shown in detail.
[0056] Figure 4 A graph of cathode current (IK) is shown and how the controller (CLR1) perfectly controls cathode current (IK).
[0057] Figure 5 A graph of anode current (IA) versus time is shown, and how the time required to reach the desired value increases due to the effect of parasitic capacitance (CGK) between the gate and cathode.
[0058] Figure 6 An embodiment proposed according to the invention is shown, wherein all gates are connected to a single power supply.
[0059] Figure 7 A block diagram of the control used in an embodiment that is the object of the present invention is shown, which control includes directly controlling the anode current (IA).
[0060] Figure 8 Deactivation of exposure via the EXP signal is shown in detail.
[0061] Fig. 9A graph of cathode current (IK) versus time is shown, and how the CLR1 controller applies overcurrent during the rise time (t1) of the cathode current (IK) to quickly charge the parasitic capacitance (CGK) between the gate and cathode.
[0062] Fig.10 shows a graph of anode current (IA) versus time, comparing Figure 5 and Fig.10 , it can be seen that reduced activation time (t1) and deactivation time (t3) are achieved. DETAILED DESCRIPTION
[0063] In view of the accompanying drawings, a preferred embodiment of the proposed invention is described below.
[0064] Figures 1 to 5 An embodiment of the prior art explained in the background of the present invention is shown.
[0065] Figure 6 An embodiment is shown as the object of the present invention, in which all gates (G) are connected to the positive terminal of a single power supply (Gps), while the negative terminal of the power supply (Gp) is grounded, requiring as many current controllers as X-ray beam emitter-receiver groups, wherein the current controllers include at least one transistor (Q1) and a controller (CLR1), in which the anode current (IA) is controlled instead of the cathode current (IK) to avoid the above-mentioned very negative effects.
[0066] Figure 7 A possible embodiment of the control of the anode current (IA) is shown, wherein a controller (CLR1) comprises a comparator (COMP) which is referenced to the current demand (DIA) of the anode producing the X-ray emission, and the feedback of the comparator (COMP) is the actual anode current (IA); and also comprises a control (G(s)), wherein the output of the controller (CLR 1) can be directly applied to the gate of a transistor (Q1) which controls the cathode current (IK).
[0067] The controller (CLR1) avoids the need to calibrate the cathode current demand (DIK) based on the anode current (IA).
[0068] The presence of the controller (CLR1) avoids the need to recalibrate the transmitters as they degrade due to type of use and time, since the controller (CLR1) always keeps each transmitter in a state of perfect accuracy due to closed loop control.
[0069] The control (G(s)) of the controller (CLR1) may be of PID type, but another type of control may also be applied.
[0070] The integral portion of the controller corrects errors and adjusts the accuracy of the anode current (IA), while the derivative portion enables faster charging of the parasitic capacitance (CGK) between the gate and cathode, greatly improving the activation transition time or rise time.
[0071] Furthermore, in a complementary manner, a buffer may be provided between the output of the controller (CLR1) and the input gate of the transistor (Q1), the buffer being responsible for delivering the necessary current to the transistor gate (Q1) to improve its response time in activation and deactivation of X-ray exposure.
[0072] Figure 8 The buffer is shown in detail, including the signal (EXP). The response time of the controller (CLR1) is similar to the activation time, i.e. 5μs. However, when the signal (EXP) is turned off, this time can be greatly reduced to the nanosecond range by the buffer, shorting the Q1 gate without waiting for the response of the CLR1 controller.
[0073] Fig. 9 It shows how the controller (CLR1) applies an overcurrent during the rise time (t1) of the cathode current (IK) to quickly charge the parasitic capacitance (CGK) between the gate and cathode. The overcurrent stops when the parasitic capacitance (CGK) between the gate and cathode is fully charged and in a stable state, which is represented by the stabilization time (t2).
[0074] Fig.10 It is shown that the anode current (IA) rises optimally during the rise time (t1) until settling at a nominal value during the settling time (t2).
[0075] During the stabilization time (t2), the cathode current (IK) and the anode current (IA) remain stable.
[0076] During the fall or deactivation time (t3), the control system receives an end-of-exposure signal, where the transistor gate (Q1) is shorted by the buffer and its currents (including IA) are extinguished optimally within nanoseconds.
[0077] After fully describing the characteristics of the present invention, in addition to the way of putting it into practice, it should be noted that, in essence, the present invention can also be put into practice in other embodiments that are different in details from those shown in the examples, and the scope of protection is equally applicable to these embodiments, as long as the main principles thereof are not changed, varied or modified.
Claims
1. An X-ray scanning control system, wherein: The X-ray scanning control system includes a plurality of emitters and at least one receiver, the emitters and the receiver are arranged opposite to each other, wherein only one emitter can be transmitting at a specific time, wherein once the transmission of one X-ray emitter is carried out and completed, the transmission of another emitter starts, and the next transmission does not start until the transmission is completed or deactivated, wherein each X-ray emitter includes an anode (A) connected to a single power supply (Aps), and includes a cathode (K) and a grid (G), wherein all grids (G) are connected to the positive terminal of a single power supply (Gps), and the negative terminal of the power supply (Gps) is grounded; in addition, there is at least one controller (CLR1) in each cathode (K) for controlling the anode current (IA), and wherein each controller (CLR 1) includes a comparator (COMP), wherein the comparator (COMP) uses the current demand (DIA) of the anode as a reference, and the feedback of the comparator (COMP) is the actual anode current (IA); and also includes a control (G(s)), wherein the controller (CLR 1) is connected to the gate of a transistor (Q1) which controls the cathode current (IK).
2. The X-ray scanning control system according to claim 1, wherein: Between the output of the controller (CLR1) and the input gate of the transistor (Q1), a buffer may be used to deliver necessary current to the gate of the transistor (Q1) to improve its response time in activation and deactivation of X-ray exposure, wherein the buffer includes a signal (EXP).
3. The 3D X-ray scanning control system according to claim 1, wherein: The controller (CLR1) applies an overcurrent during a rise time (t1) of the cathode current (IK) to quickly charge a parasitic capacitor (CGK) between the gate and the cathode, wherein the overcurrent stops when the parasitic capacitor (CGK) between the gate and the cathode is fully charged and in a stable state.
4. An X-ray scanning control system according to any one of the preceding claims, wherein: The control (G(s)) of the controller (CLR1) is of PID type.