Dose modulation method, high voltage generator and control method thereof, scanning apparatus

Abstract

The application discloses a dose modulation method, a high-voltage generator and a control method thereof, and a scanning device. The dose modulation method comprises the following steps: generating a tube current modulation carrier according to a maximum tube current of an initial scanning dose curve and an acquisition period of a detector; the initial scanning dose curve is determined according to a scanning protocol of a current scanning or a positioning image scanning result of the current scanning; determining a grid power supply control rule for performing the current scanning on a to-be-scanned object according to an amplitude relationship between the tube current modulation carrier and the initial scanning dose curve; and performing power supply control on a grid in an X-ray tube according to the grid power supply control rule; wherein an output value of the output tube current is equal to the maximum tube current of the initial scanning dose curve. The application realizes dynamic adjustment of an X-ray dose, and does not need to change a tube current, so that a situation that the tube current output is relatively lagged due to filament thermal inertia of the X-ray tube can be avoided.

Description

Technical Field

[0001] This invention relates to the field of X-ray scanning technology, and in particular to a dose modulation method, a high-voltage generator and its control method, and a scanning device. Background Technology

[0002] For medical X-ray imaging systems, minimizing radiation dose while meeting the needs of imaging therapy and diagnosis is crucial to protect the radiation safety of patients and medical staff; this is known as adhering to the principle of As Low As Reasonably Achievable (ALARA). During scanning, changes in the relative position of the X-ray source and the scanned object alter the equivalent scan load characteristics, thus affecting the X-ray energy received by the image receiving components. To comply with the ALARA principle, the radiation dose needs to be dynamically adjusted at different locations while maintaining image brightness and signal-to-noise ratio. Specifically, reducing the equivalent volume thickness decreases the dose, while increasing the equivalent volume thickness increases the dose, thereby reducing the total radiation dose throughout the scanning process.

[0003] A common dose modulation method involves maintaining a constant tube voltage during scanning and adjusting the tube current to change the X-ray dose emitted by the tube. The tube current depends on the filament temperature of the X-ray tube; adjusting the filament temperature regulates the tube current.

[0004] However, this method suffers from a slow filament temperature adjustment speed, typically reaching tens or even hundreds of milliseconds. This results in the tube current failing to quickly track changes in the target dose, not only failing to effectively reduce the dose but also potentially causing unsatisfactory image brightness and signal-to-noise ratio when scanning areas with thicker volumes. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defect in the prior art that the tube current cannot quickly track the change of the dose target value, and to provide a dose modulation method, a high voltage generator and its control method, and a scanning system.

[0006] The present invention solves the above-mentioned technical problems through the following technical solution:

[0007] In a first aspect, a dose modulation method is provided, the dose modulation method comprising:

[0008] A tube current modulation carrier is generated based on the maximum tube current of the initial scan dose curve and the detector acquisition period; the initial scan dose curve is determined according to the scanning protocol of the current scan or the positioning image scanning result of the current scan.

[0009] Based on the amplitude relationship between the tube current modulation carrier and the initial scan dose curve, the gate power supply control rule for the current scan of the object to be scanned is determined.

[0010] According to the gate power supply control rules, the gate in the X-ray tube is powered to control the output state of the tube current; wherein the output value of the tube current is equal to the maximum tube current of the initial scanning dose curve.

[0011] Optionally, the power supply control for the grid in the X-ray tube includes:

[0012] During the first target time period, a first level is provided to the gate to turn the gate off;

[0013] During the second target period, a second level is provided to the gate to turn on the gate;

[0014] Wherein, the first target time period is the time period in which the amplitude of the initial scan dose curve is greater than or equal to the amplitude of the tube current modulation carrier, and the second target time period is the time period in which the amplitude of the initial scan dose curve is less than the amplitude of the tube current modulation carrier.

[0015] Optionally, the power supply control for the grid in the X-ray tube includes:

[0016] During the first target time period, a first level is provided to the gate to turn the gate off;

[0017] During the third target period, a second level is provided to the gate to turn on the gate;

[0018] Wherein, the third target time period is the sum of the second target time period and the detector reset time; the first target time period is the corresponding time period in which the amplitude of the initial scan dose curve is greater than or equal to the amplitude of the tube current modulation carrier; the second target time period is the corresponding time period in which the amplitude of the initial scan dose curve is less than the amplitude of the tube current modulation carrier.

[0019] Optionally, when the tube current modulation carrier is sawtooth-shaped, the slope of the sawtooth side of the tube current modulation carrier is the ratio of the maximum tube current to the acquisition period.

[0020] Optionally, the trailing edge of the sawtooth wave is determined based on the detector's reset time.

[0021] Optionally, power supply control is provided for the grid in the X-ray tube, including:

[0022] When the intersection of the tube current modulation carrier and the initial scan dose curve is located at the leading edge of the tube current modulation carrier waveform, the voltage output to the gate switches from the first level to the second level to turn on the gate.

[0023] When the intersection point is located at the trailing edge of the waveform of the tube current modulation carrier, the voltage output to the gate switches from the second level to the first level to turn off the gate.

[0024] Optionally, it also includes:

[0025] When the gate is turned on, the power supply status of the high voltage generator of the X-ray tube is recorded, and the switching time for the next gate shutdown is determined based on the recorded power supply status.

[0026] Optionally, it also includes:

[0027] When the gate is turned on, the power modulation state of the high voltage generator of the X-ray tube is recorded simultaneously. Based on the recorded power modulation state, the power modulation state of the high voltage generator after the gate is turned off is determined.

[0028] Optionally, when the high-voltage generator operates in discontinuous current mode, power supply control is performed on the grid of the X-ray tube, including:

[0029] After the tube current modulation carrier intersects with the initial scan dose curve at the leading edge of the tube current modulation carrier waveform, the first switching time from the first level to the second level is determined by the zero-crossing point of the resonant current of the high-voltage generator's resonant converter.

[0030] Optionally, when the high-voltage generator is operating in continuous current mode, power supply control of the X-ray tube grid includes:

[0031] When the tube current modulation carrier and the initial scan dose curve intersect at the trailing edge of the tube current modulation carrier waveform, the second switching time for switching from the second level to the first level is determined by the resonant current value of the resonant converter of the current high voltage generator.

[0032] Secondly, a control method for a high-voltage generator is provided, including:

[0033] Determine the gate power supply control rule for the current scan of the object to be scanned; the gate power supply control rule is obtained according to the dose modulation method described in any one of the first aspects;

[0034] According to the gate power supply control rules, the output of the gate power supply unit of the high voltage generator to the gate of the X-ray tube is controlled.

[0035] Optionally, the gate power supply control rule includes a gate power supply control curve;

[0036] According to the gate power supply control rules, controlling the output power of the high-voltage generator to the gate of the X-ray tube includes:

[0037] When the gate power supply control curve is at the first level, the high voltage generator is controlled to supply the first level power to the gate to turn off the gate;

[0038] When the gate power supply control curve is at the second level, the high voltage generator is controlled to supply the second level power to the gate to turn on the gate;

[0039] Wherein, the amplitude of the first target time period in the gate power supply control curve is a first level, and the amplitude of the second target time period is a second level; the first target time period is the corresponding time period in which the amplitude of the initial scan dose curve is greater than or equal to the amplitude of the tube current modulation carrier, and the second target time period is the corresponding time period in which the amplitude of the initial scan dose curve is less than the amplitude of the tube current modulation carrier;

[0040] Alternatively, the amplitude of the third target time period in the gate power supply control curve is the second level, and the third target time period is the sum of the second target time period and the detector reset time.

[0041] Optionally, it also includes:

[0042] When the gate is turned on, the power supply status of the high voltage generator of the X-ray tube is recorded, and the switching time for the next gate shutdown is determined based on the recorded power supply status.

[0043] Optionally, it also includes:

[0044] When the gate is turned on, the power modulation state of the high voltage generator of the X-ray tube is recorded simultaneously. Based on the recorded power modulation state, the power modulation state of the high voltage generator after the gate is turned off is determined.

[0045] Thirdly, an X-ray scanning device is provided, the X-ray scanning device comprising an X-ray tube and a detector, including:

[0046] A determining module is used to determine gate power supply control rules; the gate power supply control rules are obtained according to the dose modulation method described in any one of the first aspects;

[0047] The control module triggers the high-voltage generator to provide power to the X-ray tube according to the gate power supply control rules.

[0048] Fourthly, a high-voltage generator is provided, comprising:

[0049] The control unit is used to control the gate power supply unit and the cathode power supply unit according to the gate power supply control rules; wherein, the gate power supply control rules are the rules for the current scan of the object to be scanned, determined according to the amplitude relationship between the tube current modulation carrier and the initial scan dose curve, the tube current modulation carrier is generated according to the maximum tube current of the initial scan dose curve and the acquisition period of the detector; the initial scan dose curve is determined according to the scanning protocol of the current scan or the positioning image scanning result of the current scan;

[0050] The gate power supply unit is used to supply power to the gate of the X-ray tube;

[0051] The filament power supply unit is used to supply power to the cathode of the X-ray tube, so that the output value of the X-ray tube current is equal to the maximum tube current of the initial scan dose curve.

[0052] Optionally, it also includes:

[0053] A resonant converter, which operates in a resonant state, is used to control the high-voltage generator to supply power to the X-ray tube;

[0054] The control unit is used to record the power supply operating state of the resonant converter when the resonant converter supplies power to the X-ray tube, so that the resonant converter controls the high voltage generator to supply power to the X-ray tube according to the power supply operating state.

[0055] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0056] The positive and progressive effects of this invention are as follows: Based on the amplitude relationship between the tube current modulation carrier and the initial scan dose curve, this invention determines the gate power supply control rule for the current scan of the object to be scanned, and scans the object to be scanned using this gate power supply control rule, thereby realizing dynamic adjustment of X-ray dose without changing the tube current, which can avoid the situation where the tube current output is relatively lagging due to the thermal inertia of the X-ray tube filament. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of a dosage modulation process using existing dosage modulation methods;

[0058] Figure 2 A flowchart of a dose modulation method provided as an exemplary embodiment of the present invention;

[0059] Figure 3 A flowchart illustrating the steps of power supply control for the gate in an X-ray tube in a dose modulation method provided as an exemplary embodiment of the present invention;

[0060] Figure 4 A schematic diagram illustrating the determination of a gate power supply control curve, provided as an exemplary embodiment of the present invention;

[0061] Figure 5 A flowchart illustrating the steps of power supply control for the gate in an X-ray tube in another dose modulation method provided as an exemplary embodiment of the present invention;

[0062] Figure 6 A schematic diagram of a current-modulated carrier wave provided as an exemplary embodiment of the present invention;

[0063] Figure 7 A schematic diagram of the changes in tube voltage and tube current during dose modulation is provided as an exemplary embodiment of the present invention;

[0064] Figure 8 A flowchart of a control method for a high-voltage generator is provided as an exemplary embodiment of the present invention;

[0065] Figure 9 This is a schematic diagram of the power control strategy curve of a high-voltage generator during dose modulation, provided as an exemplary embodiment of the present invention.

[0066] Figure 10 This provides a schematic diagram of another power control strategy curve for a high-voltage generator during dose modulation, as an exemplary embodiment of the present invention.

[0067] Figure 11 A schematic diagram of another method for determining the gate power supply control curve, provided as an exemplary embodiment of the present invention;

[0068] Figure 12 This is a schematic diagram of another method for determining the gate power supply control curve, provided as an exemplary embodiment of the present invention. Detailed Implementation

[0069] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0070] Current dose modulation methods maintain a constant tube voltage during scanning and adjust the tube current to change the X-ray dose emitted by the tube. This approach results in the tube current failing to quickly track changes in the target dose value. Not only does it fail to effectively reduce the dose, but it can also lead to unsatisfactory image brightness and signal-to-noise ratio when scanning thicker areas. This is because, due to the thermal inertia of the X-ray tube filament, changes in filament current cannot immediately alter the tube current; the filament temperature adjustment takes tens or even hundreds of milliseconds, making it impossible to quickly track changes in the target dose value.

[0071] For details, please refer to [link / details]. Figure 1In the figure, curve A represents the tube current (mA) required for dose modulation, curve B represents the actual tube current output curve, and curve C represents the dynamic change of filament current during dose modulation. As can be seen from the figure, in zones 1 and 3, the actual output tube current is less than the tube current required for dose modulation, which leads to a decrease in medical image brightness and signal-to-noise ratio. In zone 2, the actual output tube current is higher than the tube current required for dose modulation, resulting in an excessively high output dose, failing to achieve the expected ALARA.

[0072] To address the aforementioned problems, this invention provides a dose modulation method that achieves dose modulation by maintaining the amplitude of the X-ray tube current constant and changing the tube current output time (i.e., the wire feeding time).

[0073] Figure 2 A flowchart of a dose modulation method provided for an exemplary embodiment of the invention is shown below. Figure 2 The dose modulation method includes the following steps:

[0074] Step 201: Generate a tube current modulation carrier based on the maximum tube current of the initial scan dose curve and the detector acquisition period.

[0075] The period of the tube current modulated carrier is determined according to the acquisition period of the detector, and the peak value of the tube current modulated carrier is determined according to the maximum tube current.

[0076] The initial scan dose profile is determined based on the scanning protocol or the positioning image results of the current scan. The initial scan dose profile is a tube current profile, which characterizes the relationship between the tube current of the X-ray tube and the radiation time. The tube current profile is used to guide the modulation of different doses according to the scanned object at different motion positions.

[0077] The acquisition period, initial scan dose curve, and maximum tube current can be determined according to the scanning protocol or the positioning image scan results of the current scan. The positioning image scan results are obtained by performing a positioning scan on the object to be scanned.

[0078] Step 202: Determine the gate power supply control rules for the current scan of the target object based on the amplitude relationship between the tube current modulated carrier and the initial scan dose curve.

[0079] In step 202, the gate is turned off when the amplitude of the initial scan dose curve is greater than or equal to the amplitude of the tube current modulation carrier; the gate is turned on when the amplitude of the initial scan dose curve is less than the amplitude of the tube current modulation carrier.

[0080] Step 203: According to the gate power supply control rules, the gate in the X-ray tube is powered to control the output state of the tube current.

[0081] The output value of the output tube current is equal to the maximum tube current of the initial scan dose curve. The output state of the tube current indicates whether the X-ray tube has tube current output.

[0082] It should be noted that "equal" does not mean that the difference between the output current and the maximum current is always zero, but rather that they are essentially equal. That is, the difference between the output current and the maximum current is less than a threshold value. This threshold value is an acceptable error range after considering waveform jitter, and can be determined based on the specific circumstances.

[0083] An X-ray tube is a vacuum diode operating at high voltage. It contains two electrodes: a filament that emits electrons (cathode) and a target that receives the electron bombardment (anode). A grid is positioned between the anode and the cathode. Powering the grid controls the tube current output. When the grid is on, there is no tube current output, and the X-ray tube does not emit X-rays. When the grid is off, there is tube current output, and the X-ray tube emits X-rays. Within a given period, the grid is controlled to open / close according to power supply rules, thereby controlling the X-ray tube's output line, ensuring that the total output line equals the area under the integral of the initial modulation curve.

[0084] In this embodiment, based on the amplitude relationship between the tube current modulation carrier and the initial scan dose curve, the gate power supply control rule for the current scan of the object to be scanned is determined. According to the gate power supply control rule, the power supply to the gate in the X-ray tube is controlled so that the output value of the X-ray tube current is equal to the maximum tube current of the initial scan dose curve. This achieves dynamic adjustment of the X-ray dose without changing the tube current, avoiding the relative lag in tube current output caused by the thermal inertia of the X-ray tube filament. The output value of the X-ray tube current being equal to the maximum tube current of the initial scan dose curve satisfies the image brightness and signal-to-noise ratio requirements of the object to be scanned at different scanning positions.

[0085] In one embodiment, the gate power supply control rule generally takes the form of a pulse curve throughout the entire initial dose modulation range. In this form, the amplitude of the pulse curve remains constant, while the pulse width and pulse interval vary. The amplitude of the pulse curve corresponds to the output tube current of the X-ray tube, and the pulse width and pulse interval correspond to the radiation time. Different pulse widths and pulse intervals result in different radiation times. Based on this pulse curve, the X-ray dose of the X-ray tube can be controlled, achieving the purpose of dynamically adjusting the X-ray dose.

[0086] In one embodiment, the tube current of the initial scan dose curve is positively correlated with the scan thickness of the object being scanned.

[0087] Specifically, for the same scanned area, the maximum tube current of the initial scan dose curve is positively correlated with the maximum thickness of the scanned object at different angles. For example, if the scanned object is the lung, the thickness of the lung tissue varies at different angles around the body during a CT scan. Therefore, the maximum tube current of the initial scan dose curve is positively correlated with the maximum thickness of the scanned object at different angles.

[0088] When the relative position of the X-ray tube and the object being scanned changes, the equivalent scanning load characteristics change, and therefore the X-ray energy received by the detector also changes. To comply with the ALARA principle and meet the brightness and signal-to-noise ratio requirements of medical images at different positions, the tube current of the initial scanning dose curve is determined based on the relative position of the X-ray tube and the object being scanned. This relative position is related to the thickness of the object being scanned; therefore, determining the tube current of the initial scanning dose curve based on the thickness of the object being scanned can meet the brightness and signal-to-noise ratio requirements of the medical images.

[0089] Furthermore, the tube current of the initial scan dose curve is positively correlated with the thickness of the object being scanned. When the object is thin, the dose is reduced and the corresponding tube current is smaller; when the object is thick, the dose is increased and the corresponding tube current is larger.

[0090] In one embodiment, experimental and / or historical data, including two parameters—the thickness of the object to be scanned and the scan dose curve—can be pre-fitted to obtain the correspondence between the object thickness and the scan dose curve. During the scanning process, an initial scan dose curve matching the thickness of the object to be scanned is determined based on this correspondence.

[0091] In this embodiment of the invention, a gate power supply control rule is determined based on an initial scanning dose curve that matches the thickness of the object to be scanned. Based on this gate power supply control rule, the object to be scanned is scanned, which can obtain a medical image that meets the requirements of brightness and signal-to-noise ratio, and can effectively reduce the X-ray dose.

[0092] In one embodiment, see Figure 3 The power supply control for the grid in the X-ray tube includes:

[0093] Step 203-1: During the first target time period, a first level is provided to the gate to turn the gate off;

[0094] Step 203-2: During the second target time period, the second level is provided to the gate to turn on the gate.

[0095] The first target time period is the time period in which the amplitude of the initial scan dose curve is greater than or equal to the amplitude of the tube current modulation carrier, and the second target time period is the time period in which the amplitude of the initial scan dose curve is less than the amplitude of the tube current modulation carrier.

[0096] It should be noted that the execution order of steps 203-1 and 203-2 is not limited to... Figure 3 The diagram shows the gate being turned off first and then on. The order of gate off and on is determined based on the amplitude relationship between the tube current modulated carrier and the initial scan dose curve.

[0097] In one embodiment, the gate power supply control rule generally takes the form of a pulse curve throughout the entire initial dose rule modulation interval, hereinafter referred to as the gate power supply control curve. The amplitude of the gate power supply control curve for the first target time period is set to a first level, and the amplitude of the gate power supply control curve for the second target time period is set to a second level; wherein, the first target time period is the corresponding time period in which the amplitude of the initial scan dose curve is greater than or equal to the amplitude of the tube current modulation carrier, and the second target time period is the corresponding time period in which the amplitude of the initial scan dose curve is less than the amplitude of the tube current modulation carrier.

[0098] The first voltage level is used to control the gate to turn off, and the second voltage level is used to control the gate to turn on. The first voltage level can be either high or low, depending on the gate's power supply mechanism. When the first voltage level is high, the second voltage level is low; when the first voltage level is low, the second voltage level is high.

[0099] The following example uses the scenario where the first voltage level is high and the second voltage level is low, for comparison. Figure 4 The process of determining the gate power supply control curve will be further explained.

[0100] See Figure 4 In the figure, curve D represents the initial scan dose curve, and curve C represents the tube current modulation carrier. The time period corresponding to the amplitude of the initial scan dose curve being greater than or equal to the amplitude of the tube current modulation carrier is determined as the first target time period, and the time period corresponding to the amplitude of the initial scan dose curve being less than the amplitude of the tube current modulation carrier is determined as the second target time period. The amplitude of the gate power supply control curve for the first target time period is set to a high level, and the amplitude of the gate power supply control curve for the second target time period is set to a low level.

[0101] Control the X-ray tube to Figure 4 The gate power supply control curve shown is ( Figure 4 The X-ray tube emits X-rays when the amplitude of the gate power supply control curve is high. When the amplitude of the gate power supply control curve is low, the gate is open, the X-ray tube has no tube current output, and the X-ray tube does not emit X-rays.

[0102] In this embodiment of the invention, the output tube current of the X-ray tube is controlled based on the gate power supply control curve presented as a pulse curve. The tube voltage of the X-ray tube remains constant, and dose modulation is achieved by switching the gate voltage. Since the gate control speed is generally in microseconds or tens of microseconds, compared to the tens or even hundreds of milliseconds required for filament temperature adjustment, it represents an order-of-magnitude improvement in control speed. Thus, the dose target value can be followed quickly and accurately during the scanning process.

[0103] In one embodiment, see Figure 5 The power supply control for the grid in the X-ray tube includes:

[0104] Step 203-1': During the first target time period, a first level is provided to the gate to turn the gate off;

[0105] Step 203-2': During the third target time period, the second level is provided to the gate to turn on the gate.

[0106] The third target time period is the sum of the second target time period and the detector reset time; the first target time period is the time period in which the amplitude of the initial scan dose curve is greater than or equal to the amplitude of the tube current modulation carrier; the second target time period is the time period in which the amplitude of the initial scan dose curve is less than the amplitude of the tube current modulation carrier.

[0107] Similar to steps 203-1 and 203-2, the gate power supply control rules in steps 203-1' and 203-2' generally take the form of a pulse curve throughout the entire initial dose rule modulation range. This pulse curve is called the gate power supply control curve.

[0108] Taking the first level as high and the second level as low as an example, the tube current of the gate power supply control curve in the third target period is set to high. Thus, during the period when the amplitude of the initial scan dose curve is less than the amplitude of the tube current modulated carrier and the period corresponding to the detector reset time, the gate is turned off, the X-ray tube has tube current output, and the X-ray tube emits X-rays.

[0109] The third target time period is the sum of the second target time period and the detector reset time. The second target time period is the time period in which the amplitude of the initial scan dose curve is less than the amplitude of the tube current modulated carrier.

[0110] In one embodiment, the tube current modulated carrier wave is a sawtooth wave, and the slope of the sawtooth edge is the ratio of the maximum tube current to the acquisition period. See also Figure 4 In the figure, curve C represents the sawtooth-shaped tube current modulated carrier wave.

[0111] In one embodiment, the trailing edge of the sawtooth wave is determined based on the detector's reset time. When the detector's reset time is 0, see [reference needed]. Figure 4 The trailing edge of the modulated carrier wave can be a 90° straight line, meaning the trailing edge of the modulated carrier waveform is perpendicular to the X-axis. When the detector's reset time is greater than 0, see [reference needed]. Figure 6 The trailing edge of the carrier wave waveform includes a line perpendicular to the X-axis and a gap T, which is the detector's reset time.

[0112] It should be noted that in other implementations, the tube current modulated carrier can be other waveform forms such as isosceles triangular wave or anti-sawtooth wave.

[0113] See Figure 11 When the tube current modulated carrier is an anti-sawtooth wave, the leading edge of the modulated carrier waveform is a 90° straight line, and the slope of the sawtooth hypotenuse (the trailing edge of the modulated carrier waveform) is the ratio of the maximum tube current to the acquisition period. Figure 4 Similarly, the amplitude of the gate power supply control curve for the first target time period is set to a high level, and the amplitude of the gate power supply control curve for the second or third target time period is set to a low level.

[0114] See Figure 12 When the tube current modulated carrier wave is an isosceles triangular wave, the slope of the sawtooth hypotenuse of the modulated carrier wave can be twice the ratio of the maximum tube current to the acquisition period. Figure 4 Similarly, the amplitude of the gate power supply control curve for the first target time period is set to a high level, and the amplitude of the gate power supply control curve for the second or third target time period is set to a low level.

[0115] In one embodiment, step 203 determines the gate-on and gate-off timing based on the intersection of the tube current modulation carrier and the initial scan dose curve. Specifically: when the intersection of the tube current modulation carrier and the initial scan dose curve is at the leading edge of the tube current modulation carrier waveform, the voltage output to the gate switches from a first level to a second level to turn on the gate. At this time, the X-ray tube has no tube current output, and the X-ray tube stops emitting X-rays. When the intersection is at the trailing edge of the tube current modulation carrier waveform, the voltage output to the gate switches from a second level to a first level to turn off the gate. At this time, the X-ray tube has tube current output, and the X-ray tube emits X-rays.

[0116] In one embodiment, the dose modulation method further includes: recording the power supply operating state of the high voltage generator of the X-ray tube when the gate is turned on, and determining the switching time for the next gate shutdown based on the recorded power supply operating state.

[0117] The operating state of the power supply can be characterized by the electrical parameters of the power supply device at that time, such as the resonant inductor current and / or resonant capacitor voltage of the high voltage generator.

[0118] In this embodiment, by recording the power supply operating state, a fast and stable switching between the gate on and off states can be achieved, avoiding tube voltage fluctuations.

[0119] In one embodiment, the dose modulation method further includes: recording the power modulation state of the high voltage generator of the X-ray tube when the gate is turned on, and determining the power modulation state of the high voltage generator after the gate is turned off based on the recorded power modulation state.

[0120] The power supply modulation state can be characterized by the magnitude of the power supply voltage gain.

[0121] In this embodiment, by recording the power supply modulation state, a fast and stable switching between the gate on and off states can be achieved, avoiding tube voltage fluctuations.

[0122] In one embodiment, the dose modulation method further includes: simultaneously recording the power modulation state and power operating state of the high voltage generator of the X-ray tube when the gate is turned on; determining the switching time for the next gate shutdown based on the recorded power operating state; and determining the power modulation state of the high voltage generator applied after the gate shutdown state is switched based on the recorded power modulation state.

[0123] In this embodiment, by recording the power supply modulation state and power supply operating state, and addressing the issue that the equivalent load of the high-voltage generator is affected when the gate control rules control the gate opening or closing state, the high-voltage generator control strategy is further adjusted to achieve rapid and stable switching between the gate opening and closing states, thus avoiding tube voltage fluctuations.

[0124] During dose modulation, the changes in tube voltage and tube current are as follows: Figure 7 As shown, at the beginning of each acquisition cycle, the grid is turned off, and the tube current begins to output. At this time, for the high-voltage generator, it transitions from no-load to working load, and the tube voltage will experience a certain drop, which is kV. drop After reaching the expected dose modulation point, i.e., after the first target time period, the grid gate turns on, and the tube current output stops. At this time, the high-voltage generator transitions from a working load to an unloaded state, and the tube voltage will experience a certain overshoot, with an overshoot of kV. overshoot The changes in tube voltage during the two stages mentioned above will affect the X-ray energy spectrum, thus impacting the final imaging results.

[0125] Based on this, in one embodiment, when the high-voltage generator is operating in discontinuous current mode, power supply control of the X-ray tube gate includes:

[0126] See Figure 9When the tube current modulation carrier and the initial scan dose curve are at the leading edge of the tube current modulation carrier waveform, the first switching time for switching from the first level to the second level is determined by the time when the resonant current of the resonant converter of the high voltage generator crosses zero.

[0127] In this embodiment, to optimize tube voltage sag and overshoot, the first switching moment from the first level to the second level is determined by the zero-crossing point of the resonant current of the high-voltage generator's resonant converter. This is equivalent to inserting a delay period. By delaying the off state of the switching gate, the tube current output of the X-ray tube is delayed, thereby avoiding tube voltage overshoot that could affect the X-ray energy spectrum. Although delaying the off state of the switching gate will cause a small change in dose during the sampling period, this change is negligible when the high-voltage generator power supply operates at high frequencies.

[0128] In one embodiment, when the high-voltage generator is operating in continuous current mode, power supply control of the X-ray tube gate includes:

[0129] See Figure 10 When the tube current modulation carrier intersects with the initial scan dose curve at the trailing edge of the current modulation carrier waveform, the second switching time for switching from the second level to the first level is determined by the resonant current value of the resonant converter of the current high voltage generator.

[0130] In this embodiment, to optimize the voltage drop and overshoot of the tube, the second switching moment for switching from the second level to the first level is determined by the resonant current value of the current resonant converter of the high-voltage generator. This is equivalent to inserting a delay period. By delaying the opening state of the switching gate, the tube voltage overshoot can be avoided from affecting the X-ray energy spectrum. Although delaying the opening state of the switching gate will cause a small change in the dose during the sampling period, this change is negligible when the high-voltage generator power supply is operating at high frequencies.

[0131] Figure 8 A flowchart of a control method for a high-voltage generator is provided as an exemplary embodiment of the present invention. The control method includes the following steps:

[0132] Step 401: Determine the gate power supply control rules for the current scan of the object to be scanned.

[0133] The gate power supply control rules are obtained according to the dose modulation method provided in any of the above embodiments.

[0134] Step 402: According to the gate power supply control rules, control the output of the gate power supply unit of the high voltage generator to the gate of the X-ray tube.

[0135] In this embodiment of the invention, the X-ray tube output current of the high-voltage generator is controlled to be the same or almost the same based on the gate power supply control rule, while the tube voltage of the X-ray tube remains constant. Dose modulation is achieved by switching the gate voltage through the gate power supply control rule. Since the gate control speed is generally in microseconds or tens of microseconds, compared to the tens or even hundreds of milliseconds required for filament temperature adjustment, there is an order-of-magnitude improvement in control speed, thus enabling rapid and accurate tracking of changes in the target dose value during scanning.

[0136] In one embodiment, the gate power supply control rule includes a gate power supply control curve, that is, the gate power supply control rule is presented in the form of a gate power supply control curve. Step 402 includes: when the gate power supply control curve is at a first level, controlling the gate power supply unit of the high-voltage generator to provide the first level to the gate to turn off the gate. At this time, the tube current is turned on, and X-rays are generated. When the gate power supply control curve is at a second level, controlling the gate power supply unit of the high-voltage generator to provide the second level to the gate to turn on the gate. At this time, the tube current is turned off, and X-rays are not generated.

[0137] The resonant converter of the high-voltage generator can operate in either continuous resonant current mode or discontinuous resonant current mode.

[0138] See Figure 4 The C-curve represents the initial scan dose curve required for dose modulation of the object under scan at different scan positions. It intersects the tube current modulation carrier D at point mA_match in each acquisition cycle t_period. At the leading edge of the tube current modulation carrier, the gate is turned off, and the high-voltage generator is controlled to output a tube current with an amplitude of mA_max until the intersection point mA_match, at which point the gate is turned on and the tube current is turned off. Therefore, the discharge duration in one acquisition cycle t_period is t_actual (i.e., the pulse width of the gate power supply control curve), equivalent to the tube current output mA_avg of the X-ray tube in one acquisition cycle (the area filled with slanted lines in the figure).

[0139] from Figure 4 As can be seen, the output tube current of the X-ray tube is equal to the maximum tube current mA_max of the initial scan dose curve. The dose modulation requirements at different scanning positions are changed by adjusting the tube current output duration t_actual. The equivalent tube current output mA_avg in this acquisition cycle is precisely the tube current mA_match expected by the tube current modulation carrier D in this sampling cycle.

[0140] In this embodiment of the invention, the firing time is controlled by opening and closing the gate of the X-ray tube, thereby changing the average tube current in each imaging cycle and thus altering the emission dose for that cycle, achieving dose modulation. The gate control speed is typically in the microseconds or tens of microseconds, representing an order-of-magnitude improvement over filament temperature control. This allows for rapid and accurate tracking of dose target changes during scanning, satisfying the ALARA principle.

[0141] In one embodiment, the control method further includes: recording the power supply operating state of the high voltage generator of the X-ray tube when the gate is turned on, and determining the switching time for the next gate shutdown based on the recorded power supply operating state.

[0142] The operating state of the power supply can be characterized, but is not limited to, by the resonant inductor current and / or the resonant capacitor voltage.

[0143] In one embodiment, the control method further includes: simultaneously recording the power modulation state of the high voltage generator of the X-ray tube when the gate is turned on, and determining the power modulation state of the high voltage generator after the gate is turned off based on the recorded power modulation state.

[0144] This invention provides an X-ray scanning device, comprising:

[0145] A determination module is used to determine the gate power supply control rules; the gate power supply control rules are obtained according to the dose modulation method provided in any of the above embodiments.

[0146] The control module triggers the high-voltage generator to provide power to the X-ray scanning equipment according to the gate power supply control rules.

[0147] X-ray scanning equipment also includes other components such as X-ray tubes and detectors. The specific working mechanisms of X-ray tubes and detectors are described in any of the above embodiments and will not be repeated here.

[0148] This invention also provides a high-voltage generator, which includes:

[0149] The control unit is used to control the gate power supply unit and the cathode power supply unit according to the gate power supply control rules; wherein, the gate power supply control rules are the rules for the current scan of the object to be scanned, determined according to the amplitude relationship between the tube current modulation carrier and the initial scan dose curve, the tube current modulation carrier is generated according to the maximum tube current of the initial scan dose curve and the acquisition period of the detector; the initial scan dose curve is determined according to the scanning protocol of the current scan or the positioning image scanning result of the current scan;

[0150] The gate power supply unit is used to supply power to the gate of the X-ray tube;

[0151] The filament power supply unit is used to supply power to the cathode of the X-ray tube, so that the output value of the X-ray tube current is equal to the maximum tube current of the initial scan dose curve.

[0152] Optionally, it also includes:

[0153] A resonant converter, which operates in a resonant state, is used to control the high-voltage generator to supply power to the X-ray tube;

[0154] The control unit is used to record the power supply operating state of the resonant converter when the resonant converter supplies power to the X-ray tube, so that the resonant converter controls the high voltage generator to supply power to the X-ray tube according to the power supply operating state.

[0155] The specific working mechanism of the high-voltage generator is described in any of the above embodiments and will not be repeated here.

[0156] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A dose modulation method, characterized in that, The dose modulation method includes: A tube current modulation carrier is generated based on the maximum tube current of the initial scan dose curve and the detector acquisition period; the initial scan dose curve is determined according to the scanning protocol of the current scan or the positioning image scanning result of the current scan. Based on the amplitude relationship between the tube current modulation carrier and the initial scan dose curve, the gate power supply control rule for the current scan of the object to be scanned is determined. According to the gate power supply control rules, the gate in the X-ray tube is powered to control the output state of the tube current; wherein the output value of the tube current is equal to the maximum tube current of the initial scanning dose curve.

2. The dose modulation method according to claim 1, characterized in that, The power supply control for the grid in the X-ray tube includes: During the first target time period, a first level is provided to the gate to turn the gate off; During the second target period, a second level is provided to the gate to turn on the gate; Wherein, the first target time period is the time period in which the amplitude of the initial scan dose curve is greater than or equal to the amplitude of the tube current modulation carrier, and the second target time period is the time period in which the amplitude of the initial scan dose curve is less than the amplitude of the tube current modulation carrier.

3. The dose modulation method according to claim 1, characterized in that, The power supply control for the grid in the X-ray tube includes: During the first target time period, a first level is provided to the gate to turn the gate off; During the third target period, a second level is provided to the gate to turn on the gate; Wherein, the third target time period is the sum of the second target time period and the detector reset time; the first target time period is the corresponding time period in which the amplitude of the initial scan dose curve is greater than or equal to the amplitude of the tube current modulation carrier; the second target time period is the corresponding time period in which the amplitude of the initial scan dose curve is less than the amplitude of the tube current modulation carrier.

4. The dose modulation method according to claim 1, characterized in that, When the tube current modulation carrier is sawtooth-shaped, the slope of the sawtooth side of the tube current modulation carrier is the ratio of the maximum tube current to the acquisition period.

5. The dose modulation method according to claim 4, characterized in that, The trailing edge of the sawtooth wave is determined based on the detector's reset time.

6. The dose modulation method according to claim 1, characterized in that, The power supply control for the grid in the X-ray tube includes: When the intersection of the tube current modulation carrier and the initial scan dose curve is located at the leading edge of the tube current modulation carrier waveform, the voltage output to the gate switches from the first level to the second level to turn on the gate. When the intersection point is located at the trailing edge of the waveform of the tube current modulation carrier, the voltage output to the gate switches from the second level to the first level to turn off the gate.

7. The dose modulation method according to claim 1, characterized in that, Also includes: When the gate is turned on, the power supply status of the high voltage generator of the X-ray tube is recorded, and the switching time for the next gate shutdown is determined based on the recorded power supply status.

8. The dose modulation method according to claim 7, characterized in that, Also includes: When the gate is turned on, the power modulation state of the high voltage generator of the X-ray tube is recorded simultaneously. Based on the recorded power modulation state, the power modulation state of the high voltage generator after the gate is turned off is determined.

9. The dose modulation method according to any one of claims 1-8, characterized in that, When the high-voltage generator is operating in discontinuous current mode, the power supply control for the X-ray tube grid includes: After the tube current modulation carrier and the initial scan dose curve intersect at the leading edge of the tube current modulation carrier waveform, the first switching time for switching from the first level to the second level is determined by the time when the resonant current of the resonant converter of the high voltage generator crosses zero.

10. The dose modulation method according to any one of claims 1-8, characterized in that, When the high-voltage generator is operating in continuous current mode, the power supply control for the X-ray tube grid includes: When the tube current modulation carrier and the initial scan dose curve intersect at the trailing edge of the tube current modulation carrier waveform, the second switching time for switching from the second level to the first level is determined by the resonant current value of the resonant converter of the current high voltage generator.

11. A control method for a high-voltage generator, characterized in that, include: Determine the gate power supply control rules for the current scan of the object to be scanned; the gate power supply control rules Obtained by the dose modulation method according to any one of claims 1-10; According to the gate power supply control rules, the output of the gate power supply unit of the high voltage generator to the gate of the X-ray tube is controlled.

12. The control method for the high-voltage generator according to claim 11, characterized in that, The gate power supply control rules include the gate power supply control curve; According to the gate power supply control rules, controlling the output power of the high-voltage generator to the gate of the X-ray tube includes: When the gate power supply control curve is at the first level, the high voltage generator is controlled to supply the first level power to the gate to turn off the gate; When the gate power supply control curve is at the second level, the high voltage generator is controlled to supply the second level power to the gate to turn on the gate; Wherein, the amplitude of the first target time period in the gate power supply control curve is a first level, and the amplitude of the second target time period is a second level; the first target time period is the corresponding time period in which the amplitude of the initial scan dose curve is greater than or equal to the amplitude of the tube current modulation carrier, and the second target time period is the corresponding time period in which the amplitude of the initial scan dose curve is less than the amplitude of the tube current modulation carrier; Alternatively, the amplitude of the third target time period in the gate power supply control curve is the second level, and the third target time period is the sum of the second target time period and the detector reset time.

13. The control method for the high-voltage generator according to claim 11 or 12, characterized in that, Also includes: When the gate is turned on, the power supply status of the high voltage generator of the X-ray tube is recorded, and the switching time for the next gate shutdown is determined based on the recorded power supply status.

14. The control method for the high-voltage generator according to claim 13, characterized in that, Also includes: When the gate is turned on, the power modulation state of the high voltage generator of the X-ray tube is recorded simultaneously. Based on the recorded power modulation state, the power modulation state of the high voltage generator after the gate is turned off is determined.

15. An X-ray scanning device, the X-ray scanning device comprising an X-ray tube and a detector, characterized in that, include: The determination module is used to determine the gate power supply control rules; the gate power supply control rules The dose modulation method according to any one of claims 1-10 is obtained; The control module triggers the high-voltage generator to provide power to the X-ray tube according to the gate power supply control rules.

16. A high-voltage generator, characterized in that, include: The control unit is used to control the gate power supply unit and the cathode power supply unit according to the gate power supply control rules; wherein, the gate power supply control rules are the rules for the current scan of the object to be scanned, determined according to the amplitude relationship between the tube current modulation carrier and the initial scan dose curve, the tube current modulation carrier is generated according to the maximum tube current of the initial scan dose curve and the acquisition period of the detector; the initial scan dose curve is determined according to the scanning protocol of the current scan or the positioning image scanning result of the current scan; The gate power supply unit is used to supply power to the gate of the X-ray tube; The filament power supply unit is used to supply power to the cathode of the X-ray tube, so that the output value of the X-ray tube current is equal to the maximum tube current of the initial scan dose curve.

17. The high-voltage generator according to claim 16, characterized in that, Also includes: A resonant converter, which operates in a resonant state, is used to control the high-voltage generator to supply power to the X-ray tube; The control unit is used to record the power supply operating state of the resonant converter when the resonant converter supplies power to the X-ray tube, so that the resonant converter controls the high voltage generator to supply power to the X-ray tube according to the power supply operating state.

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