X-ray scanning control system

Abstract

An X-ray scanning control system includes multiple emitters and at least one receiver arranged opposite each other, and repeatedly enables only one emitter at a given time until an exposure is performed. Each X-ray emitter includes an anode (A), a grid (G), and a cathode (K) connected to a single power supply (Aps). At least one controller (CLR1) is connected to each cathode and controls an anode current (IA). Each controller (CLR1) includes a comparator (COMP) based on an anode current demand (DIA), and the feedback of the comparator (COMP) is the actual anode current (IA). This avoids correction of the cathode current demand value, maintains precision in all X-ray emitters, and shortens activation transition times and deactivation transition times.

Description

[Technical Field]

[0001] As the title of the invention suggests, the present invention relates to an X-ray scanning control system comprising a plurality of emitters and at least one X-ray receiver, the at least one X-ray receiver being arranged to capture an image of an object placed between the plurality of emitters and the at least one X-ray receiver, and in order to avoid distortion of the image obtained, only one emitter is allowed to emit at a given moment, and when an emission by one X-ray emitter is completed, an emission by another X-ray emitter is initiated, and the next emission is not initiated until the previous emission is completed or deactivated.

[0002] The present invention is characterized by a special design and configuration of each element that is part of the scanning system, in particular the activation and deactivation system of each X-ray emitter, in order to increase the scanning speed.

[0003] The control system can be used to perform 3D scanning and / or tomosynthesis or other types of scanning.

[0004] The invention therefore belongs to the field of control means, in particular controls used in X-ray devices. [Background technology]

[0005] X-ray imaging is one of the most commonly used techniques for visualizing the internal structure of an object and is used in a variety of applications, including medicine, security control, non-destructive testing, etc. One known limitation of flat 2D images is the presence of structural noise in the image, caused by the overlap of several objects (or tissues in the case of medical images) in the X-ray beam. To circumvent this effect, several techniques (such as computed tomography and tomosynthesis) are used to create 3D or multi-slice images of the object.

[0006] These methods require repeated imaging of the object from various angles, typically ranging from 15° (for tomosynthesis) to 360° (for computed tomography). This variation is usually achieved by rotating the x-ray source (or other geometric movement) around the object, along with a cyclically repeated imaging process for post-processing and reconstruction of 3D or multi-slice images.

[0007] The invention disclosed herein is based on a different principle, which uses multiple X-ray sources arranged in a predetermined manner and acquires a predetermined number of images by rapidly changing between them, which are then processed to reconstruct a 3D or multi-slice image.

[0008] Creating this type of 3D or multi-slice image requires very rapid switching between multiple x-ray sources, typically in the range of 5 μs to 15 μs, which is typically accomplished using a cold cathode x-ray tube, which typically includes an anode, a cathode, and an emission control grid.

[0009] Additionally, scanning systems face several problems inherent in the physics of X-ray emitters, including: The positive bias voltage of the grid relative to the cathode is several kV (0.5 kV to 10 kV) and must be controlled from the ground level. The high voltage power supply powering the anode is on the order of 20kV to 180kV and must be referenced to earth so that the anode current can be measured quickly, easily, and safely.

[0010] A first solution of the prior art is shown in FIGS.

[0011] Figure 1 shows a set of X-ray emitter-receivers, all of which share the same power supply (Aps) connected to each of the anodes (A), all of the grids (G) are connected to ground, and each of the cathodes (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 sets (1, 2, ..., 100).

[0012] Figure 1 shows that this solution, consisting of connecting all grids to ground, requires as many current controllers and power supplies as there are emitter-receiver pairs. This is done by directly controlling the cathode current (IK) using a cathode current demand (DIK) that has been pre-corrected in a separate process, which in turn controls the anode current (IA) that produces the x-ray radiation.

[0013] Figure 2 shows a block diagram of this prior art embodiment. To obtain the desired value of the anode current (IA), a cathode current demand (DIK) obtained by a pre-correction process is used, which is used as a reference for the controller (CLR1). The output of the controller (CLR1) acts on the gate of a high-voltage transistor (Q1) (MOSFET or IGBT) that controls the cathode current (IK) according to the current demand (DIK) at its input. The controller (CLR1) uses the cathode current (IK) as a feedback value for controlling the gate current of the transistor (Q1).

[0014] The controller (CLR1) is preferably of the integral type, but may be of another similar type.

[0015] Figure 3 details a crucial factor that must be taken into account: the parasitic capacitance (CGK) between the grid and cathode of the X-ray tube. This capacitance typically has a value between 15 pF and 30 pF, and must be charged in a time typically between 5 μs and 15 μs, usually between 0.5 kV and 10 kV. While this may seem practically negligible, it requires a constant load current of 10 mA to 100 mA. Considering that the typical maximum anode current (IA) is 100 mA, this parasitic capacitance cannot be ignored at all.

[0016] Figure 3 also shows that a large portion of the cathode current (IK) is the current (IC) that arises to charge the parasitic capacitance (CGK) between the grid and the cathode, which takes current from the grid (IG) and therefore causes the anode to emit a reduced anode current (IA).

[0017] Figure 4 shows how the controller (CLR1) precisely controls the cathode current (IK) according to the requirements of the 3D scanner, with a transition time of 5 μs.

[0018] On the other hand, Figure 5 shows what happens to the anode current (IA) due to the effect of the parasitic capacitance (CGK) between the grid and the cathode.

[0019] The rise time or activation transition time of the anode current (IA) is slower than expected because a portion of the grid current (IG) flows in the parasitic capacitance (CGK) between the grid and the cathode. The expected anode current (IA) value is not reached until the parasitic capacitance (CGK) between the grid and the cathode is fully charged, causing the activation transition time to be significantly longer than expected.

[0020] On the other hand, the fall time or deactivation transition time is the response time of the controller (CLR1) having the transistor (Q1), which directly cuts off all current in the circuit, including the anode current (IA), so the expected time is 5 to 15 μs.

[0021] This embodiment essentially presents four key challenges:

[0022] 1. The necessary correction of the individual current requirements (DIK) for each of the multiple X-ray emitters that make up the 3D scanner.

[0023] 2. Maintaining the accuracy of each and every X-ray emitter, regardless of degradation due to usage and time of use.

[0024] 3. Reduction of activation transition time or rise time of anode current (IA) due to parasitic capacitance between grid and cathode (CGK).

[0025] 4. A reduction in the deactivation transition or fall time of the anode current (IA) due to the response time of the controller (CLR1).

[0026] It is therefore an object of the present invention to create an X-ray scanning control system which solves the above-mentioned problems by means of a scanning control system as described below, the essence of which is stated in claim 1.

[0027] The novel solution, shown in Figure 6, consists of connecting all grids to the positive terminal of a single power supply while connecting the negative terminal of that power supply to ground, so that there are only as many independent current controllers as there are emitter-receiver pairs, and only a single power supply for all of them. Summary of the Invention

[0028] The subject matter of the invention is essentially contained in the independent claims, with various embodiments contained in the dependent claims.

[0029] The subject of the present invention is the control of an X-ray scanning system by direct control of the anode current via a grid control, in which a number of emitters and at least one receiver are arranged opposite each other, in which only one emitter is capable of emitting at a given moment, and in which when an emission by one X-ray emitter is performed and completed, an emission by another X-ray emitter is initiated and no further emission is initiated until the emission in question has finished or is deactivated.

[0030] The control system can be used to perform 3D scanning and / or tomosynthesis, or any other type of scanning.

[0031] The geometric arrangement adopted by the multiple emitters and at least one receiver may be any known one and is in no way limited, such that the object to be scanned is located between the multiple emitters and the at least one receiver.

[0032] In short, it is a scanning system having a plurality of X-ray radiation sources, and the geometric shape of the arrangement of the plurality of radiation sources is not limited.

[0033] For this reason, the emission time of each emitter must be extremely short, on the order of 5 μs to 15 μs. Similarly, the activation and deactivation transition times of the emitters must be as short as possible, always less than 5 μs. The quickest and most efficient way to do this is to use a linear controller for the grid current, which is in turn controlled and corrected by real-time measurement of the anode current.

[0034] The solution presented in this invention is to connect all grids to the positive terminal of a single power supply, while the negative terminal of that power supply is grounded; therefore, there are as many independent current controllers as there are emitter-receiver pairs, but only a single power supply.

[0035] 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 deleterious effects.

[0036] To this end, the control system includes a controller that references the current demand of the anode that produces the x-ray radiation, with the controller feedback being the actual anode current, eliminating the need to correct the cathode current demand based on the anode current.

[0037] The controller uses closed-loop control to keep each and every emitter in a state of sufficient accuracy at all times, thereby avoiding the need to recalibrate the emitters in response to emitter degradation due to usage and time.

[0038] The controller is preferably of the PID type, although other forms of control may also be applied.

[0039] The integral part of the controller corrects errors and adjusts the accuracy of the anode current (IA), while the differential part speeds up the charging of the parasitic capacitance between the grid and cathode, significantly improving the activation transition time or rise time.

[0040] Furthermore, to speed up activation and deactivation times, the deactivation or fall time is reduced by applying a signal to a buffer to short the gate of the control transistor without having to wait for a response from the CLR1 controller.

[0041] Additionally and complementary, the CLR1 controller can provide an overcurrent during the rise time of the cathode current to rapidly charge the parasitic capacitance between the grid and the cathode, which ends when the CGK capacitor is fully charged and reaches a steady state.

[0042] By the above means, the following is achieved: The need for individual cathode current requirement (DIK) corrections for each of multiple x-ray emitters is avoided. · The individual accuracy of all X-ray emitters is maintained. · Activation transition or rise time is reduced. The deactivation transition time is reduced, thus significantly reducing the scanning time by as much as 25% compared to the time required for current controllers without using measures to reduce the activation and deactivation times.

[0043] Unless otherwise specified, all technical and scientific elements used herein have the meaning commonly understood by one of ordinary skill in the art to which this invention pertains. Methods and materials similar or equivalent to those described herein may be used in the practice of the present invention.

[0044] In the present specification and claims, the use of the word "comprises" and variations thereof is not intended to exclude other technical features, additional elements, components, or steps. For those skilled in the art, other objects, advantages, and features of the invention will be inferred partly from the description and partly from the practice of the invention. [Brief explanation of the drawings]

[0045] To supplement this specification and to facilitate a better understanding of the characteristics of the invention by means of preferred practical embodiments, this specification is accompanied, as an integral part thereof, by the following set of drawings, which are presented by way of example and not of limitation:

[0046] [Figure 1] Figure 1 shows a prior art embodiment in which the grid is grounded and requires as many power supplies and current controllers as there are emitter-receiver pairs. [Figure 2] FIG. 2 shows a block diagram of the cathode current (IK) control of the prior art embodiment shown in FIG. [Figure 3] FIG. 3 shows in detail the parasitic capacitance (CGK) between the grid and cathode of an X-ray tube. [Figure 4] FIG. 4 is a graph of the cathode current (IK) and shows how the controller (CLR1) accurately controls the cathode current (IK). [Figure 5] FIG. 5 is a graph of anode current (IA) versus time, showing how the effect of the parasitic capacitance between the grid and cathode (CGK) increases the time required to reach the desired value. [Figure 6] FIG. 6 shows an embodiment proposed by the present invention, in which all grids are connected to a single power source. [Figure 7] FIG. 7 shows a block diagram of the control used in an embodiment of the invention, consisting of direct control of the anode current (IA). [Figure 8] FIG. 8 shows in detail the deactivation of exposure using the EXP signal. [Figure 9] FIG. 9 is a graph of the cathode current (IK) against time, showing how the CLR1 controller supplies an overcurrent during the rise time (t1) of the cathode current (IK) to quickly charge the parasitic capacitance (CGK) between the grid and the cathode. [Figure 10] FIG. 10 shows a graph of anodic current (IA) versus time, and comparing FIG. 5 with FIG. 10, it can be seen that reduced activation times (t1) and deactivation times (t3) were achieved. DETAILED DESCRIPTION OF THE INVENTION

[0047] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0048] 1 to 5 show a prior art embodiment that will be described in the Background of the Invention section of the present invention.

[0049] Figure 6 shows an embodiment of the present invention in which all grids (G) are connected to the positive terminal of a single power supply (Gps), the negative terminal of which is connected to ground, and which requires as many current controllers as there are emitter-receiver pairs in the X-ray beam, the current controller comprising at least one transistor (Q1) and a controller (CLR1), and in which the anode current (IA) is controlled instead of the cathode current (IK) to avoid the very negative effects mentioned above.

[0050] FIG. 7 shows a possible embodiment for controlling the anode current (IA), in which a controller (CLR1) comprises a comparator (COMP) referenced to the anode current requirement (DIA) for generating X-ray radiation, the feedback of which is the actual anode current (IA), and further comprises a control unit (G(s)) capable of applying the output of the controller (CLR1) directly to the gate of a transistor (Q1) controlling the cathode current (IK).

[0051] The controller (CLR1) avoids the need to correct the cathode current demand (DIK) based on the anode current (IA).

[0052] The presence of the controller (CLR1) avoids the need to recalibrate the emitters in response to emitter degradation due to usage and time, as the closed control loop keeps each and every emitter in a state of sufficient accuracy at all times.

[0053] The control section (G(s)) of the controller (CLR1) may be of a PID type, but other types of control may also be applied.

[0054] The integral part of the controller corrects errors and adjusts the accuracy of the anode current (IA), while the differential part speeds up the charging of the parasitic capacitance (CGK) between the grid and cathode, significantly improving the activation transition time or rise time.

[0055] Additionally, a buffer may be provided between the output of the controller (CLR1) and the input gate of the transistor (Q1) to supply the necessary current to the transistor gate (Q1) to improve the response time both in activating and deactivating the X-ray exposure.

[0056] Figure 8 shows the details of the buffer containing the signal (EXP). The controller (CLR1) has a similar response time as the activation time, i.e., 5 μs. However, this activation time can be significantly reduced to the nanosecond range by having the buffer short out the Q1 gate when the signal (EXP) is turned off, without waiting for the response of the CLR1 controller.

[0057] Figure 9 shows how the controller (CLR1) provides an overcurrent during the rise time (t1) of the cathode current (IK) to quickly charge the grid-to-cathode parasitic capacitance (CGK). This overcurrent ends when the grid-to-cathode parasitic capacitance (CGK) is fully charged and reaches a steady state, represented by the stabilization time (t2).

[0058] FIG. 10 shows that the anode current (IA) rises optimally during the rise time (t1) until it stabilizes at its nominal value during the stabilization time (t2).

[0059] During the stabilization time (t2), the cathode current (IK) and the anode current (IA) remain stable.

[0060] During the fall time or deactivation time (t3), the control system receives the exposure end signal, the gate of the transistor (Q1) is shorted by the buffer, and its current (including IA) optimally decays in a few nanoseconds.

[0061] Having fully described the nature of the present invention as well as the manner in which it may be practiced, it is hereby submitted that the invention may be practiced in other embodiments which differ in detail from those illustrated, and protection equally applies to them, provided that, in essence, the central principles thereof are not altered, varied or modified.

Claims

1. An X-ray scanning control system comprising a plurality of emitters and at least one receiver arranged opposite each other, and only one emitter capable of emitting radiation at a given moment, wherein when radiation by one X-ray emitter is performed and completed, radiation by another X-ray emitter is initiated, and the next radiation is not initiated until the radiation is completed or deactivated, each of the X-ray emitters comprises an anode (A), a cathode (K), and a grid (G) connected to a single power supply (Aps), and all of the grids (G) are connected to the positive terminal of the single power supply (Gps), while: The negative terminal of the power supply (Gps) is grounded, and each of the cathodes (K) is provided with at least one controller (CLR1) for controlling the anode current (IA), each of the controllers (CLR1) comprising a comparator (COMP) based on the anode current demand (DIA) and whose feedback is the actual anode current (IA), and a control unit (G(s)), and the output of the controller (CLR1) is connected to the gate of a transistor (Q1) for controlling the cathode current (IK).

2. 2. The X-ray scanning control system of claim 1, wherein a buffer is provided between the output of the controller (CLR1) and the input gate of the transistor (Q1) to provide the necessary current to the gate of the transistor (Q1) to improve the response time of both activation and deactivation of X-ray exposure, the buffer including a signal (EXP).

3. 2. The X-ray scanning control system of claim 1, wherein the controller (CLR1) supplies an overcurrent during a rise time (t1) of the cathode current (IK) to rapidly charge a parasitic capacitance (CGK) between the grid and the cathode, and the overcurrent ends when the parasitic capacitance (CGK) between the grid and the cathode is fully charged and reaches a steady state.

4. 4. The X-ray scanning control system according to claim 1, wherein the control section (G(s)) of the controller (CLR1) is of a PID type.

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