Control method and device for current modulation of narrow pulse ray source tube

Abstract

The invention discloses a narrow pulse ray source tube current modulation control method and device. The control method comprises the following steps: setting a tube current target value of sequence first exposure; calculating to obtain a filament basic current of sequence first exposure through a basic filament correction algorithm; first exposure is carried out, and ray source tube current sampling data of the first exposure, brightness data of dose feedback detection and attenuation graph information data are collected; and for the second exposure and subsequent exposure of the sequence, the tube current target value, the filament basic current and the filament compensation current of the current exposure are independently adjusted and set according to the acquired data of the previous exposure, and then the current exposure is carried out, so that accurate tube current modulation and output are realized, and the requirement of the CT system on tube current modulation is met.

Description

Technical Field

[0001] The invention relates to a control method for current modulation of a narrow pulse ray source tube, and also to a corresponding control device, belonging to the technical field of radiation imaging. Background Art

[0002] CT (Computed Tomography) equipment uses X-rays to scan a certain thickness of the object or human body part, and reconstructs the collected data of the X-rays that penetrate the object or human body part to obtain a tomographic image of the object or human body part. CT imaging has the characteristics of fast scanning time and clear images, and is currently widely used in medical, security inspection, and industrial fields.

[0003] In the prior art, the X-rays in the CT device are generated and emitted by the tube (also called the ray tube, which together with the high-voltage generator constitutes the ray source). The cathode filament of the tube is heated by applying a filament current. When the temperature reaches a certain level, the active electrons on the cathode filament in the high electric field environment overflow and bombard the anode target of the tube to generate X-rays. The process of the electron overflow reaching the anode is characterized by the tube current (also called mA current). During the exposure process of the ray source, under the condition that the electric field strength remains unchanged, the density of the overflowing electrons is changed by adjusting the filament current applied to the cathode filament, so that the number of emitted electrons changes, that is, the tube current is adjusted, thereby changing the radiation dose of the CT device. Generally, there is a thermal hysteresis process from the change of the filament current to the change of the filament temperature. The traditional ray source can generate continuous X-rays ranging from hundreds of milliseconds to tens of seconds. On the one hand, it has enough time to react to the temperature change of the filament; on the other hand, its continuous current output is conducive to the closed-loop regulation of the tube current, which is easy to achieve the requirements of the tube current modulation of the CT system. As for the narrow pulse radiation source used in static CT system, it needs to provide narrow pulse sequence exposure from 500 microseconds to several milliseconds. The influence of thermal hysteresis of the filament cannot be ignored. The closed-loop regulation effect of the tube current is poor in a short time, resulting in poor accuracy and controllability of the tube current, which makes it difficult to meet the requirements of tube current modulation of the CT system.

[0004] In the Chinese patent with patent number ZL 201410494104.2, a method for controlling the filament current in a CT tube is disclosed. This control method still has the problems of poor tube current control effect and poor controllability for the non-continuous exposure control of narrow pulses, and cannot meet the requirements of tube current modulation of narrow pulse ray sources. In addition, in the Chinese patent application with application number 202311456512.4, a ray control method is disclosed. When this ray control method controls the filament current through the grid beam, on the one hand, the focal spot size will be affected and change, which will affect the imaging effect of the system and increase the complexity of the system algorithm; on the other hand, when the grid beam changes, the change of its focal spot will constrain the exposure power, so that the range of tube current modulation is limited. Summary of the invention

[0005] The primary technical problem to be solved by the present invention is to provide a control method for current modulation of a narrow pulse ray source tube.

[0006] Another technical problem to be solved by the present invention is to provide a control device for current modulation of a narrow pulse ray source tube.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] According to a first aspect of an embodiment of the present invention, a method for controlling current modulation of a narrow pulse ray source tube is provided, comprising the following steps:

[0009] (100) performing tube current modulation for the first exposure of the sequence, comprising the following sub-steps:

[0010] (1) Setting the tube current target value for the first exposure of the sequence;

[0011] (2) according to the tube current target value of the first exposure of the sequence, the basic filament current of the first exposure of the sequence is calculated by a basic filament correction algorithm;

[0012] (3) performing the first exposure of the filament base current of the first exposure of the filament loading sequence, and collecting the radiation source tube current sampling data, the brightness data of the dose feedback detection and the attenuation diagram information data of the first exposure;

[0013] (200) Modulating the tube current for the second exposure and subsequent exposures of the sequence, including the following sub-steps:

[0014] (4) performing error analysis and calculation based on the sampling data of the radiation source tube current of the previous exposure and the brightness data of the dose feedback detection and the corresponding relationship between the two to obtain an error correction coefficient;

[0015] (5) setting a tube current target value for this exposure based on the attenuation map information data of the previous exposure and the relationship between the tube current and the attenuation map information data;

[0016] (6) using the error correction coefficient to correct the tube current target value for this exposure to obtain a corrected tube current target value; and then calculating the filament basic current for this exposure of the sequence using a basic filament correction algorithm;

[0017] (7) calculating a tube current difference obtained by subtracting the tube current corresponding to the attenuation map information data of the previous exposure from the tube current target value of the current exposure, and judging the tube current difference; when the tube current difference is not equal to zero, proceeding to step (8); when the tube current difference is equal to zero, proceeding to step (9);

[0018] (8) searching for the difference coefficient and the adjustment time table according to the tube current difference, obtaining the filament current compensation coefficient and the compensation output time coefficient, and calculating the filament compensation current and filament compensation time for this exposure; then proceeding to step (10);

[0019] (9) using the filament base current, filament compensation current and filament compensation time of the previous exposure as the filament base current, filament compensation current and filament compensation time of the current exposure;

[0020] (10) superimposing the filament base current of this exposure and the filament compensation current of this exposure and loading them to the filament for this exposure; at the same time, collecting the radiation source tube current sampling data, the brightness data of the dose feedback detection and the attenuation diagram information data of this exposure;

[0021] (11) looping through steps (4) to (10) until the last exposure of the exposure sequence, and then proceeding to the next step;

[0022] (12) The narrow pulse sequence exposure ends.

[0023] Preferably, in step (2), the calculation of the filament base current for the first exposure of the sequence satisfies the following formula:

[0024] f1=λ1*I 2 +λ2*I+I0

[0025] Among them, f1 is the basic current of the filament for the first exposure of the sequence, λ1 is the coefficient of the quadratic term of the polynomial fitting, λ2 is the coefficient of the linear term of the polynomial fitting, I is the target value of the tube current, and I0 is the constant term of the polynomial fitting.

[0026] Preferably, in step (4), the calculation of the error correction coefficient satisfies the following formula:

[0027] ki =a1 / a2

[0028] Among them, k i represents the error correction coefficient, i represents the sequence number of this exposure; a1 is the sampling data of the ray source tube current of the previous exposure, and a2 is the tube current value corresponding to the brightness data of the dose feedback detection of the previous exposure.

[0029] Preferably, in step (6), the calculation of the filament base current of this exposure satisfies the following formula:

[0030] f i =λ1*(I x ) 2 +λ2*I x +I0

[0031] Among them, f i Indicates the filament base current of this exposure, i indicates the sequence number of this exposure; I x is the target value of the tube current after correction for this exposure; λ1 is the coefficient of the quadratic term of the polynomial fitting, λ2 is the coefficient of the linear term of the polynomial fitting, and I0 is the constant term of the polynomial fitting.

[0032] Preferably, in step (8), when the tube current difference is greater than zero, the filament compensation current Ic of this exposure is i and the filament compensation time Tc i The calculation satisfies the following formula:

[0033] Ic i =p*(Ith_h)

[0034] Tc i =v*Te

[0035] Among them, p is the filament current compensation coefficient corresponding to the positive tube current difference, v is the compensation output time coefficient, Ith_h is the fixed fluctuation high threshold of the filament current, and Te is the exposure time of this exposure.

[0036] Preferably, in step (8), when the tube current difference is less than zero, the filament compensation current Ic of this exposure is i and the filament compensation time Tc i The calculation satisfies the following formula:

[0037] Ic i =n*(Ith_l)

[0038] Tc i =v*Te

[0039] Among them, n is the filament current compensation coefficient corresponding to the negative tube current difference, v is the compensation output time coefficient, Ith_l is the fixed fluctuation low threshold of the filament current, and Te is the exposure time of this exposure.

[0040] According to a second aspect of an embodiment of the present invention, there is provided a control device for current modulation of a narrow pulse ray source tube, comprising a processor and a memory, wherein the processor and the memory are coupled; wherein:

[0041] The memory is used to store computer programs;

[0042] The processor is used to run the computer program stored in the memory to execute the above-mentioned control method for narrow pulse ray source tube current modulation.

[0043] Compared with the prior art, the control method for tube current modulation of a narrow pulse ray source provided in the embodiment of the present invention uses the relevant data collected in the previous exposure to set and adjust the tube current and filament current of the next exposure. In the sequential exposure, each exposure pulse is automatically advanced and preset separately to achieve accurate tube current modulation and output, thereby meeting the requirements of tube current modulation of the CT system. Therefore, the control method for tube current modulation of a narrow pulse ray source provided in the embodiment of the present invention has the beneficial effects of good controllability of tube current output, high accuracy, and excellent closed-loop regulation effect in a short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A flow chart of a method for controlling current modulation of a narrow pulse ray source tube provided by an embodiment of the present invention;

[0045] Figure 2 A schematic diagram of a control device for current modulation of a narrow pulse ray source tube provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The technical content of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] For ease of understanding and explanation, the concept of "narrow pulse sequence exposure" provided by the narrow pulse radiation source is first briefly introduced. Narrow pulse sequence exposure, also known as narrow exposure pulse sequence, is a group of narrow pulses orderly distributed in time, which characterizes the tube current that can generate X-rays, i.e., mA current. The first exposure in the sequence means that the radiation source emits the first narrow pulse X-ray. The parameters such as the width, tube current, and time interval of each narrow pulse in the narrow pulse sequence can be the same or different. By adjusting the narrow pulse sequence exposure design, the radiation dose of the CT device can be changed, thereby obtaining the required specific image information, so as to achieve the purpose of optimizing image contrast and clarity.

[0048] like Figure 1 As shown, a method for controlling current modulation of a narrow pulse ray source tube provided by an embodiment of the present invention comprises at least the following steps:

[0049] S100: performing tube current modulation for the first exposure of the sequence, including the following sub-steps:

[0050] S1: Set the tube current target value for the first exposure of the sequence.

[0051] The CT system sets the tube current target value for the first exposure of the sequence according to the radiation dose required by the task.

[0052] S2: According to the tube current target value of the first exposure of the sequence, the basic filament current of the first exposure of the sequence is calculated by the basic filament correction algorithm.

[0053] In one embodiment of the present invention, the basic filament correction algorithm includes at least the following sub-steps: in each gear of the electric field voltage of 70 to 140 kV (10 kV step), the filament current is gradually increased from the lowest value of the filament current in a fixed increment to carry out tube training, the tube current data corresponding to the filament current at each voltage gear is recorded, the tube core tube current / filament current curve is drawn, and a polynomial fitting is carried out for the data, and at the same time, the coefficient of determination of the fitting effect is analyzed. When the coefficient of determination is ≥0.5, the effect of the fitting formula is accepted; when the coefficient of determination is <0.5, the region with a large fitting error is subjected to a segmented fitting method to improve the fitting credibility. After the above operation process, the calculation formula of the basic filament current can be obtained. When the tube current target value at a certain voltage level is set, the formula can be used to deduce the filament current that needs to be loaded for the output of this working condition, that is, the basic filament current.

[0054] For example, after the operation of the basic filament correction algorithm, the calculation formula of the filament basic current f1 for the first exposure of the sequence is as follows:

[0055] f1=λ1*I 2 +λ2*I+I0 (1)

[0056] Among them, λ1 is the coefficient of the quadratic term of the polynomial fitting, λ2 is the coefficient of the linear term of the polynomial fitting, I is the target value of the tube current, and I0 is the constant term of the polynomial fitting.

[0057] S3: The filament basic current of the first exposure of the filament loading sequence is used for the first exposure. At the same time, the radiation source tube current sampling data, the brightness data of the dose feedback detection and the attenuation diagram information data of the first exposure are collected.

[0058] The X-ray source tube current sampling data of the first exposure is collected by the X-ray source device, and the brightness data and attenuation map information data of the dose feedback detection are collected by the CT system. The collected data will be used to modulate the tube current of the next exposure in the sequence exposure to form an advance preset plan for each exposure pulse separately during the narrow pulse sequence exposure process.

[0059] S200: performing tube current modulation for the second exposure and subsequent exposures of the sequence, including the following sub-steps:

[0060] S4: performing error analysis and calculation based on the ray source tube current sampling data of the previous exposure and the brightness data of the dose feedback detection and the corresponding relationship between the two to obtain the error correction coefficient k.

[0061] The tube current feedback link of the X-ray source is a linear sampling mechanism. After obtaining the X-ray source tube current sampling data and the dose feedback detection data, the X-ray source control system can correct the ratio of its internal tube current sampling according to the linear ratio. Assuming that the X-ray source tube current sampling data of the previous exposure is a1, and the tube current value corresponding to the brightness data of the dose feedback detection is a2, then the error correction coefficient k i for:

[0062] k i =a1 / a2 (2)

[0063] Among them, i represents the sequence number of this exposure.

[0064] S5: According to the attenuation map information data of the previous exposure and the relationship between the tube current and the attenuation map information data, a target tube current value of the radiation source for the current exposure is set.

[0065] The CT system uses the attenuation map information data of the previous exposure projection to calculate the relationship between the tube current and the attenuation map information data, and obtains the tube current value required for the next exposure projection, which is set as the tube current target value. The filament base current required by the radiation source can then be determined based on the tube current target value of this exposure.

[0066] S6: The target tube current value of this exposure is corrected using the error correction coefficient k to obtain a corrected target tube current value; and then the basic filament correction algorithm is used to calculate the basic filament current of the sequence for this exposure.

[0067] Assume that the corrected tube current target value is I x , the filament base current f of this exposure i The calculation formula is as follows:

[0068] f i =λ1*(I x ) 2 +λ2*I x+I0 (3)

[0069] Among them, f i It represents the basic current of the filament for this exposure, i represents the sequence number of this exposure; λ1 is the coefficient of the quadratic term of the polynomial fitting, λ2 is the coefficient of the linear term of the polynomial fitting, I is the target value of the tube current, and I0 is the constant term of the polynomial fitting.

[0070] S7: Calculate the tube current difference obtained by subtracting the tube current corresponding to the attenuation map information data of the previous exposure from the tube current target value of the current exposure, and judge the tube current difference; when the tube current difference is not equal to zero, go to step S8; when the tube current difference is equal to zero, go to step S9.

[0071] S8: searching the difference coefficient and adjusting the time table according to the tube current difference, obtaining the filament current compensation coefficient and the compensation output time coefficient, and calculating the filament compensation current and filament compensation time for this exposure; then proceeding to step S10.

[0072] The calculation of the filament compensation current and the filament compensation time in step S8 includes two cases:

[0073] The first case: When the tube current difference is greater than zero, the filament compensation current Ic for this exposure i and filament compensation time Tc i The calculation is as follows:

[0074] Ic i =p*(Ith_h) (4)

[0075] Tc i =v*Te (5)

[0076] Among them, p is the filament current compensation coefficient corresponding to the positive tube current difference, v is the compensation output time coefficient, Ith_h is the fixed fluctuation high threshold of the filament current, and Te is the exposure time of this exposure.

[0077] The difference coefficient and adjustment time table are the corresponding relationship tables of the output positive (negative) tube current difference, filament current compensation coefficient and compensation output time coefficient when the system corrects the filament basic current of the first exposure of the sequence through the basic filament correction algorithm. The filament compensation current and its compensation output time can be obtained by looking up the table and calculating, which serves as the compensation scheme for the filament current of this exposure. Among them, the setting of the fixed fluctuation high threshold of the filament current is usually based on the filament life curve. Within the safe range of the filament life, a larger value is selected as the fixed fluctuation high threshold. For example, the working range of the filament current is 6A. According to the filament life curve and the safety range (0.95), the fixed fluctuation high threshold of the filament current is selected as 5.7A.

[0078] The second case: When the tube current difference is less than zero, the filament compensation current Ic for this exposure i The calculation is as follows:

[0079] Ic i =n*(Ith_l) (6)

[0080] Wherein, n is the filament current compensation coefficient corresponding to the negative tube current difference, and Ith_l is the fixed fluctuation low threshold of the filament current.

[0081] Filament compensation time Tc i Formula (5) is still used for calculation. The setting of the fixed fluctuation low threshold of the filament current is usually selected to be less than or equal to the preheating current value, for example, the fixed fluctuation low threshold of the filament current is selected to be 2.5A.

[0082] S9: The filament base current, filament compensation current and filament compensation time of the previous exposure are used as the filament base current, filament compensation current and filament compensation time of this exposure.

[0083] When the tube current difference is equal to zero, it means that the tube current output is accurate and does not need to be readjusted this time. The parameter settings for this exposure can use the parameter settings for the previous exposure. It should be noted that if the previous exposure is the first exposure in the sequence, the filament compensation current and filament compensation time are both zero.

[0084] The above steps S4 to S9 are mainly the process of setting and adjusting the tube current and the filament current of the current exposure according to the relevant data collected in the previous exposure.

[0085] S10: superimpose the filament base current of this exposure and the filament compensation current of this exposure and load them to the filament for this exposure; at the same time, collect the ray source tube current sampling data of this exposure, the brightness data of the dose feedback detection and the attenuation diagram information data.

[0086] S11: loop through steps S4 to S10 until the last exposure of the exposure sequence, and then proceed to the next step.

[0087] The second exposure and subsequent exposure sequences execute steps S4 to S10 in a loop, and the system implements advance preset adjustment and control of each exposure pulse individually. It should be noted that the loading time of the filament compensation current is only the duration of the compensation output time, which is less than or equal to the exposure time of this exposure, and the exposure time is the loading time of the filament basic current.

[0088] S12: Narrow pulse sequence exposure ends.

[0089] The above describes in detail the various steps of the control method for the narrow pulse ray source tube current modulation provided in the embodiment of the present invention. Through the above steps, each exposure pulse in the narrow pulse sequence exposure process is preset in advance, thereby achieving accurate control of the tube current to meet the requirements of the narrow pulse ray source tube current modulation.

[0090] The control method of the narrow pulse ray source tube current modulation is further described below through an embodiment of a narrow pulse sequence exposure process in an application scenario.

[0091] For example, in a certain application scenario, a narrow pulse radiation source needs to carry out sequential exposure at a voltage level of 120kV. The parameter values ​​for the first exposure of the sequence are as follows: the tube current target value is 180mA, the exposure time is 1.3ms, and the interval time is 16ms, so as to set the relevant information for starting the radiation source system. In addition, according to the working parameters of the tube core, the high threshold of the fixed fluctuation of the filament is set to 5.7A, and the low threshold of the fixed fluctuation of the filament current is set to 2.5A. The process of the control method of the tube current modulation of the narrow pulse radiation source is as follows.

[0092] S101: Set the tube current target value for the first exposure of the sequence to 180 mA.

[0093] The CT system sets the tube current target value for the first exposure of the sequence of the radiation source device according to the radiation dose required by the task.

[0094] S102: Based on the tube current target value of 180 mA for the first exposure of the sequence, the basic filament correction algorithm is used to calculate the basic filament current f1 for the first exposure of the sequence at a voltage level of 120 kV using the above formula (1):

[0095] f1=-0.000045*180 2 +0.016563*180+3.894685=5.418025A;

[0096] Among them, -0.000045 is the coefficient of the quadratic term of the polynomial fit, 0.016563 is the coefficient of the linear term of the polynomial fit, and 3.894685 is the constant term of the polynomial fit.

[0097] S103: The filament base current of the first exposure in the filament loading sequence is 5.418A for the first exposure. At the same time, the radiation source device collects the radiation source tube current of 179mA for the first exposure. The CT system collects the brightness data and attenuation map information data of the dose feedback detection. The tube current value corresponding to the dose feedback brightness data collected by the CT system is 174mA.

[0098] Here is the second exposure process:

[0099] S104: According to the sampling data of the ray source tube current 179mA of the previous exposure and the brightness data of the dose feedback detection and the corresponding relationship between the two, an error analysis is performed to obtain the error correction coefficient k1:

[0100] k1=a1 / a2=179 / 174=1.0287;

[0101] Among them, a1 is the sampling data of the tube current of the ray source, and a2 is the tube current value corresponding to the brightness data detected by dose feedback.

[0102] S105: The CT system sets a target tube current value for the current exposure of the radiation source according to the attenuation map information data of the previous exposure and the relationship between the tube current and the attenuation map information data.

[0103] The CT system uses the attenuation map information data of the previous exposure projection to calculate according to the relationship between the tube current and the attenuation map information data, and obtains the tube current value required for the next exposure projection as 170mA, that is, sets the tube current target value of the radiation source for this exposure to 170mA.

[0104] S106: The target tube current value of this exposure is corrected using the error correction coefficient k1, and the modified target tube current value is 174.879 mA; the basic filament correction algorithm is used to calculate the basic filament current f2 of this exposure sequence at a voltage level of 120 kV as follows:

[0105] f2=-0.000045*174.879 2 +0.016563*174.879+3.894685=

[0106] 5.415A;

[0107] S107: The tube current target value 170mA of this exposure minus the tube current 174mA corresponding to the attenuation map information data of the previous exposure, the tube current difference is -4mA. The tube current difference is less than zero, so the filament compensation current and filament compensation time need to be calculated according to the second case of the aforementioned step S8.

[0108] S108: According to the tube current difference -4mA, the difference coefficient and adjustment time table are searched (see Table 1), and the filament current compensation coefficient corresponding to the negative tube current difference is obtained as 1.0 and the compensation output time coefficient is 0.1; the filament compensation current Ic2 and filament compensation time Tc2 of this exposure are calculated as follows:

[0109] Ic2=1.0*2.5=2.5A

[0110] Tc2=0.1*1.3=0.13ms

[0111] Among them, 2.5A is the fixed fluctuation low threshold of the filament current, and 1.3ms is the exposure time of this exposure. Then, the process goes to step S110.

[0112] Table 1 Differential coefficient and adjustment schedule at 120kV level

[0113] Negative tube current difference -10mA~0 -20mA~-10mA <-20mA Filament current compensation factor 1.0 1.1 1.2 Compensation output time coefficient 0.1 0.35 0.5

[0114] It should be noted that Table 1 only lists the coefficient table corresponding to the negative tube current difference, and does not include the data when the tube current difference is positive. In addition, in order to further improve the accuracy of compensation, the difference coefficient and adjustment time table can be formulated as a matrix table with a smaller scale. For example, the negative tube current difference is within the range of -20mA to 0, which can be divided into six or more intervals, and the filament current compensation coefficient and filament current compensation time coefficient corresponding to each interval are listed respectively. It is also possible to introduce a closed loop by using real-time data analysis in the process of quoting the table.

[0115] S110: The filament base current of 5.415A (exposure time is 1.3ms) and the filament compensation current of 2.5A (filament compensation time is 0.13ms) of this exposure are superimposed and loaded to the filament for this exposure; at the same time, the radiation source device collects the radiation source tube current sampling data of this exposure, and the CT system collects the brightness data and attenuation map information data of the dose feedback detection.

[0116] S111: loop through steps S104 to S110 until the last exposure of the exposure sequence, and then proceed to the next step.

[0117] S112: The narrow pulse sequence exposure ends.

[0118] It should be noted that, in the subsequent sequence exposure process, if the tube current difference calculated in step S107 of a certain sequence exposure is greater than zero, step 108 will be replaced by the first case of step S8 in the aforementioned method; if the tube current difference calculated in step S107 is equal to zero, step 108 will be replaced by step S10 in the aforementioned method.

[0119] It can be seen from the above embodiments that the control method for tube current modulation of a narrow pulse radiation source provided by the embodiments of the present invention, in a sequential exposure, uses the relevant data collected in the previous exposure to separately set and adjust the tube current and filament current of the next exposure, thereby achieving precise tube current modulation and output.

[0120] Based on the above narrow pulse ray source tube current modulation control method, the embodiment of the present invention further provides a narrow pulse ray source tube current modulation control device, such as Figure 2As shown, the control device includes one or more processors and a memory. The memory is coupled to the processor and is used to store one or more computer programs. When the one or more computer programs are executed by the one or more processors, the one or more processors implement the control method for current modulation of the narrow pulse ray source tube in the above embodiment.

[0121] The processor is used to control the overall operation of the control device to complete all or part of the steps of the control method for current modulation of the narrow pulse ray source tube. The processor module can be a central processing unit (CPU), a graphics processing unit (GPU), a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a digital signal processing (DSP) chip, etc. The memory is used to store various types of data to support operations on the control device, and these data may include, for example, instructions for any application or method for operating the control device, and data related to the application. The memory module can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, etc.

[0122] In summary, compared with the prior art, the control method for tube current modulation of a narrow pulse ray source provided in the embodiment of the present invention uses the relevant data collected in the previous exposure to set and adjust the tube current and filament current of the next exposure. In the sequential exposure, each exposure pulse is automatically pre-set in advance to achieve accurate tube current modulation and output, thereby meeting the requirements of tube current modulation of the CT system. Therefore, the control method for tube current modulation of a narrow pulse ray source provided in the embodiment of the present invention has the beneficial effects of good controllability of tube current output, high accuracy, and excellent closed-loop regulation effect in a short time.

[0123] The above is a detailed description of the control method and device for current modulation of the narrow pulse ray source tube provided by the present invention. For those skilled in the art, any obvious changes made to it without departing from the essence of the present invention will constitute an infringement of the patent right of the present invention and will bear corresponding legal responsibilities.

Claims

1. A control method for current modulation of a narrow pulse ray source tube, characterized in that The steps include: (100) performing tube current modulation for the first exposure of the sequence, comprising the following sub-steps: (1) Setting the tube current target value for the first exposure of the sequence; (2) according to the tube current target value of the first exposure of the sequence, the basic filament current of the first exposure of the sequence is calculated by a basic filament correction algorithm; (3) performing the first exposure of the filament base current of the first exposure of the filament loading sequence, and collecting the radiation source tube current sampling data, the brightness data of the dose feedback detection and the attenuation diagram information data of the first exposure; (200) Modulating the tube current for the second exposure and subsequent exposures of the sequence, including the following sub-steps: (4) performing error analysis and calculation based on the sampling data of the radiation source tube current of the previous exposure and the brightness data of the dose feedback detection and the corresponding relationship between the two to obtain an error correction coefficient; (5) setting a tube current target value for this exposure based on the attenuation map information data of the previous exposure and the relationship between the tube current and the attenuation map information data; (6) using the error correction coefficient to correct the tube current target value of this exposure to obtain a corrected tube current target value; Then the basic filament correction algorithm is used to calculate the basic filament current of the sequence for this exposure; (7) calculating a tube current difference obtained by subtracting the tube current corresponding to the attenuation map information data of the previous exposure from the tube current target value of the current exposure, and judging the tube current difference; when the tube current difference is not equal to zero, proceeding to step (8); when the tube current difference is equal to zero, proceeding to step (9); (8) searching for the difference coefficient and the adjustment time table according to the tube current difference, obtaining the filament current compensation coefficient and the compensation output time coefficient, and calculating the filament compensation current and filament compensation time for this exposure; then proceeding to step (10); (9) using the filament base current, filament compensation current and filament compensation time of the previous exposure as the filament base current, filament compensation current and filament compensation time of the current exposure; (10) superimposing the filament base current of this exposure and the filament compensation current of this exposure and loading them to the filament for this exposure; at the same time, collecting the radiation source tube current sampling data, the brightness data of the dose feedback detection and the attenuation diagram information data of this exposure; (11) looping through steps (4) to (10) until the last exposure of the exposure sequence, and then proceeding to the next step; (12) The narrow pulse sequence exposure ends.

2. The control method for narrow pulse ray source tube current modulation as claimed in claim 1, characterized in that In step (2), the basic filament correction algorithm includes the following sub-steps: At the preset electric field voltage level, the filament current is gradually increased from the lowest value in fixed increments to train the tube, the tube current data corresponding to the filament current at each voltage level is recorded, the tube core current / filament current curve is drawn, and polynomial fitting is performed on the tube current data; Analyze the coefficient of determination of the fitting effect; when the coefficient of determination is ≥ 0.5, the effect of the fitting formula is accepted; When the coefficient of determination is less than 0.5, the region with large fitting error is fitted in sections to improve the fitting reliability.

3. The control method for narrow pulse ray source tube current modulation as claimed in claim 2, characterized in that In step (2), the calculation of the filament base current for the first exposure of the sequence satisfies the following formula: f1=λ1*I 2 +λ2*I+I0 Among them, f1 is the basic current of the filament for the first exposure of the sequence, λ1 is the coefficient of the quadratic term of the polynomial fitting, λ2 is the coefficient of the linear term of the polynomial fitting, I is the target value of the tube current, and I0 is the constant term of the polynomial fitting.

4. The control method for narrow pulse ray source tube current modulation as claimed in claim 1, characterized in that In step (4), the calculation of the error correction coefficient satisfies the following formula: <h2 style=";text-align:left;direction:ltr">k<h2 style=";text-align:left;direction:ltr"> i <h2 style=";text-align:left;direction:ltr"> (a1 / a2) Among them, k i represents the error correction coefficient, i represents the sequence number of this exposure; a1 is the sampling data of the ray source tube current of the previous exposure, and a2 is the tube current value corresponding to the brightness data of the dose feedback detection of the previous exposure.

5. The control method for narrow pulse ray source tube current modulation as claimed in claim 1, characterized in that In step (6), the calculation of the filament base current for this exposure satisfies the following formula: f i =λ1*(I x ) 2 +λ2*I x +I0 Among them, f i Indicates the filament base current of this exposure, i indicates the sequence number of this exposure; I x is the target value of the tube current after correction for this exposure; λ1 is the coefficient of the quadratic term of the polynomial fitting, λ2 is the coefficient of the linear term of the polynomial fitting, and I0 is the constant term of the polynomial fitting.

6. The control method for narrow pulse ray source tube current modulation as claimed in claim 1, characterized in that In step (8), when the tube current difference is greater than zero, the filament compensation current Ic of this exposure is i and the filament compensation time Tc i The calculation satisfies the following formula: Ic i =p*(Ith_h) Tc i =v*The Among them, p is the filament current compensation coefficient corresponding to the positive tube current difference, v is the compensation output time coefficient, Ith_h is the fixed fluctuation high threshold of the filament current, and Te is the exposure time of this exposure.

7. The control method for narrow pulse ray source tube current modulation as claimed in claim 1, characterized in that In step (8), when the tube current difference is less than zero, the filament compensation current Ic of this exposure is i and the filament compensation time Tc i The calculation satisfies the following formula: Ic i =n*(Ith_l) Tc i =v*The Among them, n is the filament current compensation coefficient corresponding to the negative tube current difference, v is the compensation output time coefficient, Ith_l is the fixed fluctuation low threshold of the filament current, and Te is the exposure time of this exposure.

8. A control device for current modulation of a narrow pulse ray source tube, characterized in that It includes a processor and a memory, wherein the processor and the memory are coupled; wherein, The memory is used to store computer programs; The processor is used to run the computer program stored in the memory to execute the control method for current modulation of a narrow pulse ray source tube as claimed in any one of claims 1 to 7.

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