CT system and calibration method based on CT tube filament current calibration

Abstract

The present invention discloses a CT system based on filament current calibration in a CT tube and a calibration method thereof, wherein the CT system includes a host, a CT frame fixed end, a CT frame rotating end, a calibration system, a data acquisition system, an imaging system and a workstation. The calibration method of the filament current in the CT tube includes obtaining a first calibration condition; exposing and calculating a suitable filament current value according to the first calibration condition; sampling and processing to obtain a series of suitable filament current values; fitting all filament current values ​​of the system according to some filament current values; optimizing the filament current correction time through the training tube in the CT system; and performing a filament current correction warning display through the daily scanning preheating protocol in the CT system. After the filament current is calibrated by the method of the present invention, it can play a basic guarantee role in the scanning imaging and hardware stability of the CT system.

Description

Technical Field

[0001] The invention belongs to the field of medical systems, and in particular relates to a method and system for calibrating a filament current in a CT tube in a computer tomography imaging system. Background Art

[0002] X-rays are electromagnetic waves with extremely short wavelengths and high energy. The wavelength of X-rays is shorter than that of visible light, and its photon energy is tens to hundreds of thousands times greater than that of visible light. They were discovered by German physicist W.K. Roentgen in 1895, so they are also called Roentgen rays. X-rays are currently widely used in medical imaging diagnosis.

[0003] The CT tube radiates X-rays, which are attenuated by the human body and reach the detector. Computer tomography technology is used to reconstruct the projection data into human body cross-sectional images.

[0004] The CT tube is one of the most core and key components in the computer tomography system. The CT tube is actually a large high-vacuum cathode ray diode with a cathode and an anode, and a filament is set on the cathode. During the operation of the CT tube, by applying current to the cathode filament, the filament is heated and a cloud of free electrons is generated, and then a high voltage is applied to the cathode and cathode. Due to the sudden increase in the potential difference between the cathode and cathode, under the drive of the high-voltage strong electric field, the active free electron beam on the cathode filament will collide with the anode tungsten target and undergo energy conversion. Part of the electrical energy is converted into X-rays emitted by the window, and the other part of the electrical energy is converted into heat energy and dissipated by the heat dissipation system. Among them, the current supplied to the cathode filament is called the filament current, the voltage between the cathode and cathode is called the tube voltage, and the current formed by the electrons generated by the heating of the filament moving at high speed to the anode under the action of the high-voltage electric field between the cathode and cathode is called the tube current (also called mA).

[0005] Before using each CT tube, the corresponding relationship between the tube current and the filament current needs to be calibrated. The commonly used methods include the following:

[0006] First, by exposing at each working point of the filament current, the corresponding tube current value is obtained through testing. Due to the large number of working points, a large number of tests are required to obtain the corresponding relationship between the tube current and the filament current to achieve the calibration of the filament current of the X-ray tube. Therefore, the current method has the disadvantages of too many exposure points and too much data volume, and there is a problem of wasting the life of the X-ray tube;

[0007] The second is to directly use the relevant parameters provided by the manufacturer. Compared with the above process, this parameter does not need to be corrected, but the accuracy and precision are slightly worse, because the high-voltage system for the filament current provided by the tube manufacturer is likely to be different from the high-voltage system used by the medical device manufacturer itself, so the modulation method of the filament current in the high-voltage system is also different;

[0008] The third is to use partial scanning conditions for calculation, but still use the system preheating, tube training and filament current correction as independent systems that do not interfere with each other. At the same time, with the convergence of the previous filament current, the subsequent independent filament current correction conditions should be more accurate and the iteration speed should be faster, but there is no corresponding optimization plan in the design plan currently seen. Summary of the invention

[0009] The purposes of the present invention include the following: to solve the problem of additional dose suffered by patients due to the long stabilization time of the filament current during actual scanning reconstruction; to solve the problem of excessive dependence of traditional filament current on manufacturer parameters and too many exposure times for filament current correction; to optimize the process and efficiency of filament current correction from the system level; to solve the problem of how to provide timely warning when problems with filament current occur during clinical use of the system from the system level.

[0010] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0011] A CT system based on filament current calibration in a CT tube, comprising:

[0012] The host is responsible for the interaction between the system and the user, sending the workflow required by the user to the entire system and feeding back the results to the user;

[0013] The fixed end of the CT rack is responsible for receiving instructions from the host and controlling the work of the entire hardware system;

[0014] The rotating end of the CT rack receives the instructions sent by the fixed end of the CT rack through the slip ring;

[0015] The correction system is responsible for the overall correction and calibration of the CT system. By adjusting the various components of the CT system, the CT system works in a good state. At the same time, according to the characteristics of the CT system, a series of correction tables are generated. The correction tables are used in the preprocessing stage of the reconstruction system, so that the CT system can produce tomographic images with low noise and high contrast.

[0016] The data acquisition system is responsible for receiving the data acquisition instructions from the host, receiving the raw data generated by the hardware through the DMS, and storing it on the hard disk;

[0017] The imaging system is responsible for receiving the reconstruction instructions from the host, reading the raw data collected by the data acquisition system, using the correction table generated by the correction system, reconstructing the image through computer tomography technology, and feeding it back to the host;

[0018] Workstation, after receiving the image reconstructed by the reconstruction system, the host can send it to the workstation for diagnosis according to user needs.

[0019] Preferably, the host sends the scanning workflow to the fixed end of the CT rack, sends the imaging workflow to the imaging system, sends the correction workflow to the correction system, and displays the feedback of the above components to the user, and stores the results in the database, file, and server.

[0020] Preferably, the fixed end of the CT gantry includes a scanning bed system and a rotating motor, which is the core brain of the CT hardware and is responsible for the overall scheduling work; the rotating end of the CT gantry includes a collimator control system, a DMS data acquisition system, a high-voltage control system, and a tube. The rotating end of the CT gantry serves as the core computing unit of the CT hardware, and generates data required by the reconstruction system through exposure of the high-voltage control system and data acquisition of the DMS system. The data is transmitted to the data acquisition system through a slip ring and a data acquisition card, and then applied to the reconstruction system for image preprocessing and reconstruction.

[0021] A method for calibrating the filament current in a CT tube comprises the following steps:

[0022] 1) Obtaining a first calibration condition;

[0023] 2) exposing and calculating a suitable filament current value according to the first calibration condition;

[0024] 3) Sampling and processing to obtain a series of appropriate filament current values;

[0025] 4) According to the partial filament current values, all filament current values ​​of the system are obtained by fitting;

[0026] 5) Optimize the filament current correction time through tube training in the CT system;

[0027] 6) Filament current correction warning display is performed through the daily scan warm-up protocol in the CT system.

[0028] Preferably, the first correction condition obtained in step 1) specifically refers to the tube voltage value, the tube current value and the initial filament current value; step 2) specifically refers to performing exposure according to the set tube voltage value, the tube current value and the initial filament current value, and calculating the actual appropriate filament current value according to the feedback filament current value curve.

[0029] Preferably, in the step 3), all exposure conditions in the system, including the tube voltage and the tube current, are sampled, a small number of points are selected for exposure calculation, and corresponding appropriate filament current values ​​are obtained respectively; in the step 4), nonlinear fitting is performed on the appropriate filament current value obtained by the sampled exposure calculation, so as to obtain the filament current values ​​under all exposure conditions of the system.

[0030] Preferably, the training operation of the CT tube in step 5) is an indispensable part of the system initialization installation. Incorporating data collection of filament current correction into this process can significantly reduce the correction time of the filament current. The daily scanning preheating protocol of the CT tube in step 6) is one of the most frequently used parts in the system. The system collects necessary data on the filament current during preheating, and determines whether it is necessary to prompt the user to update the filament current correction by determining the value of the filament current at this time.

[0031] A method for calibrating the filament current in a CT tube, the specific steps are as follows:

[0032] Obtain the tube voltage, tube current, tube focus size, and filament current curve provided by the tube manufacturer, count the initial curve values ​​of multiple hardware, and perform average calculation as the initial filament current meter value;

[0033] Acquire the first scanning condition, including the tube voltage, the tube current, the focal point size and the filament current value, perform exposure, and collect the corresponding filament current feedback value as the first data, and collect the corresponding tube current feedback value as the second data;

[0034] Analyze the curve characteristics of the first data according to the first data, obtain the peaks and troughs of the first data curve, and record the time information corresponding to the peaks and troughs;

[0035] According to the first data and the second data, the curve characteristics in the first data and the second data are analyzed, a first time point corresponding to the start of stability of the filament current in the first data and a second time point corresponding to the start of stability of the tube current in the second data are obtained, the first time point and the second time point are compared, and the earlier time point is taken as the start time point of system exposure stability;

[0036] Determine whether the start time of exposure stabilization is less than the ideal value, which is 40ms by default. If it is less than the ideal value, the filament current has reached the requirement and the filament current value is considered qualified under this condition.

[0037] Determine whether the start time of exposure stability is less than the ideal value, which is 40ms by default. If it is greater, the filament current has not yet reached the requirement and iterative exposure is required to reach the convergence condition.

[0038] During iterative exposure, the filament current value needs to be updated each time. The direction of the next filament current adjustment is determined by judging the location of the peaks and valleys and the absolute difference with the stable filament current.

[0039] During iterative exposure, the amplitude of each adjustment of the filament current uses the dichotomy method to ensure the convergence and correction speed of the filament current correction process;

[0040] After the current condition filament current calibration is qualified, the same operation is performed on all sampling points in the system to obtain the appropriate filament current for all sampling points;

[0041] The filament currents at all sampling points are nonlinearly fitted to obtain the appropriate filament currents under all conditions. The nonlinear fitting here is generally polynomial fitting, exponential fitting or power function fitting.

[0042] Preferably, the method for calibrating the filament current in a CT tube further comprises the following steps:

[0043] In the CT system, the CT tube is trained according to the needs, and the impurities in the tube have been removed;

[0044] The tube training operation requires a large number of exposure operations. The exposure conditions during this operation, including tube voltage, tube current, and exposure times, can cover multiple sampling points. The number of exposure times under a single condition ensures that convergence can be achieved within the number of exposure times.

[0045] During the tube training operation, it is necessary to control the data acquisition system, collect the same exposure data as the filament current correction, and perform iterative calculations to obtain the appropriate filament current values ​​under different conditions;

[0046] After the tube training operation is completed, nonlinear fitting needs to be performed based on the sampling points used in the tube training process and the corresponding filament current convergence values ​​to obtain the appropriate filament current under all conditions;

[0047] This method uniquely integrates filament current correction into other essential system correction links, reducing system correction time, saving correction steps, and optimizing the process during the initial installation of the system.

[0048] Preferably, the method for calibrating the filament current in a CT tube further comprises the following steps:

[0049] In CT systems, preheating is an essential daily step before the system performs scanning and imaging;

[0050] Collect data related to filament current correction during the preheating process;

[0051] The collected filament current data is used to determine whether the filament current meets the conditions. When the filament current does not meet the conditions and needs to be iteratively updated, the user is given an early warning message that the current filament current has deviated and the system is corrected.

[0052] The present invention has the following beneficial effects and advantages:

[0053] Through filament current correction, the system scan can quickly reach a stable state, ensuring image quality from the perspective of the radiation source; by sampling all scanning conditions of the system, filament current correction is performed on some scanning conditions, and then fitted to all scanning conditions, thereby solving the problem of too many exposure times and long correction time in traditional filament current correction; filament current correction efficiency is optimized at the system level. Filament current correction and tube training operations are both essential processes during the initial installation of the CT system. Traditionally, everyone handles the two separately, which wastes time and the number of exposures of the tube. The two are organically combined so that the filament current process is integrated into the training process; during the use of the system, the daily warm-up process can be monitored. When a problem with the filament current is found, the user is informed in a timely manner to prevent the patient from receiving additional exposure that does not meet the image quality requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a component connection diagram of the CT system in the present invention;

[0055] Figure 2 The present invention is a flow chart of the calibration method of the CT tube filament current;

[0056] Figure 3 This is a flow chart of single condition filament current correction in the present invention;

[0057] Figure 4 This is a flow chart of multi-condition filament current correction in the present invention;

[0058] Figure 5 It is a flow chart combining the tube training process and the filament current correction in the present invention;

[0059] Figure 6 It is the preheating flow chart of the present invention; DETAILED DESCRIPTION

[0060] In order to more clearly illustrate the technical solution, implementation process and related factors of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0061] This system involves a correction method for the filament current of a CT tube in computer tomography technology (such as Figure 2 The method can be applied to the filament current correction of the CT system.

[0062] like Figure 1 As shown, Figure 1 Several important components of the third-generation CT system were demonstrated, including:

[0063] The host 101 is responsible for the interaction between the system and the user, sends the workflow required by the user to the entire system, and feeds back the results to the user; typically, it sends the scanning workflow to the CT gantry fixed end 102, sends the imaging workflow to the imaging system 106, sends the correction workflow to the correction system 104, and displays the feedback of the above systems to the user, and stores the results in the database, file, server, etc. as necessary;

[0064] The CT gantry fixed end 102 is responsible for receiving instructions from the host 101 and controlling the work of the entire hardware system, including the CT gantry rotating end 103, the scanning bed system, the rotating motor, etc. It is the core brain of the CT hardware and is responsible for the overall scheduling work;

[0065] The CT gantry rotating end 103 receives the instruction sent by the CT gantry fixed end 102 through the slip ring. The rotating end includes the collimator control system, the DMS data acquisition system, the high-voltage control system, the tube, etc. The CT gantry rotating end 103 is equivalent to the core computing unit of the CT hardware. Through the exposure of the high-voltage control system and the data acquisition of the DMS system, the data required by the reconstruction system 106 is generated, and the data is transmitted to the data acquisition system 105 through the slip ring and the data acquisition card, and then applied to the reconstruction system 106 for image preprocessing and reconstruction;

[0066] The correction system 104 is responsible for the overall correction and calibration of the CT system, which is equivalent to adjusting various CT system subcomponents to make the CT system work in a good state. At the same time, according to the characteristics of the CT system, a series of correction tables are generated for the preprocessing stage of the reconstruction system 106, so that the CT system can generate tomographic images with low noise and high contrast;

[0067] The data acquisition system 105 is responsible for receiving the data acquisition instructions from the host 101, receiving the raw data generated by the hardware through the DMS, and storing it on the hard disk;

[0068] The imaging system 106 is responsible for receiving the reconstruction instruction from the host 101, reading the raw data collected by the data acquisition system 105, using the correction table generated by the correction system 104, reconstructing the image through the computer tomography technology, and feeding it back to the host 101;

[0069] Workstation 108: After receiving the image reconstructed by reconstruction system 106, host 101 can send it to workstation 108 according to user's needs for diagnosis.

[0070] like Figure 3 As shown in the figure, the single-condition filament current correction process includes the following steps:

[0071] S1, obtain the average filament current table stored in the system. This table is obtained from the experience of the previous system. Generally speaking, about 10 prototypes with the same high voltage system and the same bulb system can be taken to obtain the corrected filament current of each machine, and then the filament current tables of these machines are averaged, which is used as the initial average filament current table of the entire system stored in the system;

[0072] S2, obtaining a first set of scanning conditions, including the tube voltage, the tube current, the focal spot size, and the original value of the filament current, as the first correction condition.

[0073] In S2, it should be noted that the filament current is not only related to the tube voltage and tube current, but also directly related to the focal size. Generally, under the same tube voltage and tube current conditions, the filament current corresponding to a small focal point will be larger than the filament current corresponding to a large focal point.

[0074] S3, exposing the first calibration condition and collecting feedback data, including at least integration time, filament current curve, mA curve, kV curve. Usually, the integration time unit is milliseconds or higher precision. The filament current curve includes the oscillation period of the filament current and the stable period of the filament current. The filament current curve can indirectly reflect the quality of the initial filament current setting. The larger the oscillation amplitude and the longer the oscillation period, it can be considered that the filament current value setting under the first calibration condition deviates more from the ideal value.

[0075] S4, calculating the stable value of the filament current curve, and recording the timestamp when it is initially stable, which is recorded as the first calculation. In the first calculation, the filament current is first smoothed to eliminate the influence of burrs, and then the average of the last 30% of the data of the filament current curve is selected as the filament current value in the stable period, and the filament current error threshold is read to calculate the timestamp when the filament current is initially stable;

[0076] S5, determining whether the first calculation result reaches a stable state. If so, it indicates that the current filament current value is appropriate, the calibration is completed, and the current value is the appropriate filament current value. If not, the subsequent iterative calibration needs to be continued.

[0077] In S5, the criterion for determining whether a stable state is reached is whether the timestamp of the filament current stabilization is less than the system expectation, such as 40 ms or less designed by the system. The system expectation is related to the specific system.

[0078] S6, calculate the peak value and trough value of the filament current, and the corresponding timestamp, which is recorded as the second calculation; before the filament current curve reaches a stable state, there will be a curve similar to damped motion. Through simple comparison operations or derivative operations, multiple peaks and troughs in the system can be found. The positions of the peaks and troughs and the corresponding timestamps need to be recorded in the second calculation.

[0079] In S6, special attention should be paid to the fact that although the filament current curve has been smoothed before, there are still some small peaks and valleys that should not be included in the system. Therefore, the two points with the largest peak amplitude and the smallest valley amplitude should be considered as the key points and recorded as the characteristic points of the filament current curve.

[0080] S7, according to the second calculation result and the characteristic point of the filament current curve, the filament current adjustment direction can be adjusted as the third calculation.

[0081] In S7, when the timestamp corresponding to the peak of the filament current curve is smaller than the timestamp corresponding to the trough, it means that the filament current value during the original exposure acquisition may be too small. Because the high-voltage control system finds that the setting conditions are too small, the system characteristics will first increase its value to quickly reach a stable filament current, and then achieve a stable tube current.

[0082] On the contrary, in S7, when the timestamp corresponding to the peak of the characteristic point of the filament current curve is greater than the timestamp corresponding to the trough, it means that the filament current value during the original exposure acquisition may be too large, because the high-voltage control system finds that the setting conditions are too large, and the system characteristics will first lower its value to quickly achieve a stable filament current, and then achieve a stable tube current.

[0083] S8, using the binary search method in combination with the third calculation to calculate a new filament current. The purpose of using the binary search method is to make the numerical correction of the filament current under this condition converge quickly.

[0084] After the calculation of S8 is completed, it is necessary to enter step S3 and iterate the process.

[0085] S9, combining the calculation methods of S8 and S5, determines whether the iteration process is completed.

[0086] From S3 to S9, if convergence is achieved, the calibration is successfully completed. If the calibration still does not converge after reaching the maximum number of iterations, it means that the calibration of this condition has failed.

[0087] like Figure 4 As shown in the figure, the multi-condition filament current correction process includes the following steps:

[0088] S11, sampling all scanning conditions of the system to obtain a partial correction condition list.

[0089] All scanning conditions referred to in S11 are conditions that affect the values ​​of the filament current, including the tube voltage, the tube current and the focal spot size, but do not include conditions corresponding to other imaging systems 106, such as collimation system parameters.

[0090] In S11, all conditions are sampled. In a general CT system, the number of kV is 3 to 5, the focus is 1 to 2, and the tube current ranges from 5mA to 670mA. Therefore, the priority sampling object is the tube current. According to the type of the final fitting curve, the number of sampling points is generally 3 to 5 mA.

[0091] S12, obtaining a first set of scanning conditions, including the tube voltage, the tube current, the focal spot size, and the original value of the filament current, as a second correction condition.

[0092] S13, performing a correction calculation on the second correction according to the process from S1 to S9 to obtain a second correction result;

[0093] S14, comparing the initial filament current correction table according to the second correction result, and updating the subsequent default values ​​of the filament current.

[0094] In S14, the purpose of updating the default value of the subsequent filament current is to make the subsequent filament current correction converge faster and reduce the number of scans. The fundamental reason is that the shape of the filament current curve is generally fixed, and when one point is offset, other points will also be offset by a similar method.

[0095] In S14, the formula for updating the values ​​of other filament current meters is as follows:

[0096] Filament new =Filame nt old +Filame nt offset

[0097] Where: Filament offset is the difference between the second calibration result and the default filament current value;

[0098] Filament old It is the default filament current value for other conditions;

[0099] Filament new is the updated filament current value for other conditions;

[0100] S15, obtaining subsequent scanning conditions, including tube voltage, tube current, focus size, and original value of filament current, as the third correction condition.

[0101] S16, obtaining a third corrected filament current correction result through iterative scanning calculation as a third correction result.

[0102] S17, according to the second filament correction result and the third correction result, compare the initial filament current correction table and update the subsequent filament current default value. The updating method also refers to the formula in S14.

[0103] After the process from S15 to S17 is completed, it is necessary to refer to the updating method of the filament current meter value in the process from S12 to S14 to continue updating the other filament current values ​​that have not been scanned. The purpose is also to converge faster, reduce the number of system exposures, and save exposure time.

[0104] S18, according to the filament current correction results under all sampling conditions, fitting calculation is performed to obtain the appropriate filament current for all scanning conditions; in S18, according to previous experience and data fitting results, generally all three methods can be used for fitting, and the effect of fitting is related to the number of selected sampling points. The fitting formula can use the following formula.

[0105] f(x)=a n *x n +a n-1 *x n-1 +a n-2 *x n-2 +...+a0

[0106] f(x)=a*x b +c

[0107] f(x)=a*e bx +c

[0108] a, b, c, a in the above formula n All are fitting coefficients. In S18, three fitting formulas are mentioned. Different CT systems, different tubes, and different high pressures may require different applicable formulas, but the principles are similar. Therefore, it is necessary to make an adaptation selection based on the actual data used.

[0109] like Figure 5 As shown in the figure, the training process and filament current correction process flow chart include the following steps:

[0110] S21, similar to the multi-condition filament current correction, obtains the list of training tube exposure conditions.

[0111] In S21, the exposure condition of each training tube needs to be executed several times, which is greater than the general iteration number of the filament current correction. Therefore, this single condition can be used to reduce the exposure time and exposure number of the filament current correction.

[0112] In S21, there are many combinations of overall exposure conditions, some of which can fully meet the requirements of S18, which can greatly reduce the filament current correction time.

[0113] S22, expose in the order specified in the exposure condition list to ensure the correctness of the tube training process. The process here is to use the tube training operation to achieve the purpose of filament current correction, so the first thing to ensure is the tube training process.

[0114] S23, it should be noted that the current exposure condition has not reached the upper limit of the number of times, and the current filament current correction still does not obtain a suitable result. At this time, iterative calculation can be performed to obtain the filament current value used for the next exposure.

[0115] In S23, it is important to note that the necessary data needs to be retained for each exposure and then calculated. The time for this calculation and data saving cannot affect the normal training workflow.

[0116] S24, it should be noted that when the current exposure condition reaches the number of times, the filament current data corresponding to this round of exposure conditions should be retained for subsequent overall fitting. The data can be saved to a file, database or server to prevent data loss.

[0117] S25, after the tube training is finished, all the conditions and results of the filament current corrections that have been performed are counted, and combined with S18, a fitting calculation of the overall filament current correction result is performed.

[0118] S26, for some conditions that fail to meet the calculation data volume requirement of S18, a supplementary scan of separate conditions can be performed. Even so, the number of filament current exposures can be greatly reduced.

[0119] like Figure 6 As shown, the CT system tube preheating flowchart includes the following steps.

[0120] S31, similar to the multi-condition filament current correction, obtains a list of preheating exposure conditions.

[0121] S32, obtain the exposure conditions in the list, and expose in the specified order, while saving the raw data required for the filament current.

[0122] S33, while exposing, obtain the filament current of the current exposure condition and continue the filament current correction analysis based on the data.

[0123] S34, calculate whether the current filament current value is qualified, the formula is as follows:

[0124] Delta = abs(Filame nt current -Filame nt config )

[0125] Where Filament currentThe appropriate filament current calculated for the current, Filament config is the filament current obtained by filament current correction in the configuration file, and Delta is the difference between the absolute values ​​of the two.

[0126] In S34, the threshold for determining whether the filament current is qualified needs to be set reasonably. If the setting is too strict, it may cause unnecessary trouble to the user.

[0127] S35, when the calculation result Delta in S34 exceeds the threshold setting, the system prompts the user to perform filament current correction update, otherwise the image may be affected.

Claims

1. A method for calibrating the filament current in a CT tube of a CT system, characterized in that: It includes the following steps: 1) obtaining a first calibration condition; 2) Expose and calculate the filament current value according to the first calibration condition; 3) Sampling and processing to obtain a series of filament current values; 4) According to the partial filament current values, all the filament current values ​​of the system are fitted; 5) Optimize the filament current correction time through tube training in the CT system; 6) Filament current correction warning display through daily scan warm-up protocol in CT system; The specific steps of this calibration method are as follows: Obtain the tube voltage, tube current, tube focus size, and filament current curve provided by the tube manufacturer, count the initial curve values ​​of multiple hardware, and perform average calculation as the initial filament current meter value; Acquire the first scanning condition, including the tube voltage, the tube current, the focal point size and the filament current value, perform exposure, and collect the corresponding filament current feedback value as the first data, and collect the corresponding tube current feedback value as the second data; Analyze the curve characteristics of the first data according to the first data, obtain the peaks and troughs of the first data curve, and record the time information corresponding to the peaks and troughs; According to the first data and the second data, the curve characteristics in the first data and the second data are analyzed, a first time point corresponding to the start of stability of the filament current in the first data and a second time point corresponding to the start of stability of the tube current in the second data are obtained, the first time point and the second time point are compared, and the earlier time point is taken as the start time point of system exposure stability; Determine whether the start time of exposure stabilization is less than the ideal value, which is 40ms by default. If it is less than the ideal value, the filament current has reached the requirement and the filament current value is considered qualified under this condition. Determine whether the start time of exposure stability is less than the ideal value, which is 40ms by default. If it is greater, the filament current has not yet reached the requirement and iterative exposure is required to reach the convergence condition. During iterative exposure, the filament current value needs to be updated each time. The direction of the next filament current adjustment is determined by judging the location of the peaks and valleys and the absolute difference with the stable filament current. During iterative exposure, the amplitude of each adjustment of the filament current uses the dichotomy method to ensure the convergence and correction speed of the filament current correction process; After the current condition filament current calibration is qualified, the same operation is performed on all sampling points in the system to obtain the appropriate filament current for all sampling points; Nonlinear fitting is performed on the filament currents at all sampling points to obtain appropriate filament currents under all conditions, wherein the nonlinear fitting includes polynomial fitting, exponential fitting or power function fitting.

2. The method for calibrating the filament current in the CT tube of the CT system according to claim 1, characterized in that: The training operation of the CT tube in step 5) is an indispensable part of the system initialization installation. Incorporating the data collection of the filament current correction into this process can greatly reduce the correction time of the filament current. The daily scanning preheating protocol of the CT tube in step 6) is one of the most frequently used parts in the system. The system collects necessary data on the filament current during preheating, and determines whether it is necessary to prompt the user to update the filament current correction by determining the value of the filament current at this time.

3. The method for calibrating the filament current in a CT tube of a CT system according to claim 1, characterized in that: It also includes the following steps: In the CT system, the CT tube needs to be trained after installation to remove the impurities in the tube; The tube training operation requires a large number of exposure operations. The exposure conditions during this operation, including tube voltage, tube current, and exposure times, can cover multiple sampling points. The number of exposure times under a single condition ensures that convergence can be achieved within the number of exposure times. During the tube training operation, it is necessary to control the data acquisition system, collect the same exposure data as the filament current correction, and perform iterative calculations to obtain the filament current values ​​under different conditions; After the tube training operation is completed, nonlinear fitting is required based on the sampling points used in the tube training process and the corresponding filament current convergence values ​​to obtain the appropriate filament current under all conditions.

4. The method for calibrating the filament current in the CT tube of a CT system according to claim 1, characterized in that: It also includes the following steps: In CT systems, preheating is an essential daily step before the system performs scanning and imaging; Collect data related to filament current correction during the preheating process; The collected filament current data is used to determine whether the filament current meets the conditions. When the filament current does not meet the conditions and needs to be iteratively updated, the user is given an early warning message that the current filament current has deviated and the system is corrected.

Images