阅读说明：本技术 基于ct球管中灯丝电流校准的ct系统及其校准方法 (CT system based on filament current calibration in CT bulb tube and calibration method thereof ) 是由 相会财 邢占峰 王群 晏雄伟 王鑫 宋晓飞 于 2020-10-20 设计创作，主要内容包括：本发明公开了一种基于CT球管中灯丝电流校准的CT系统及其校准方法,其中CT系统包括主机,CT机架固定端,CT机架旋转端,校正系统,数据采集系统,建像系统和工作站。其中CT球管中灯丝电流的校准方法包括获取第一校正条件；根据第一校正条件曝光并计算合适的灯丝电流数值；采样处理得到一些列合适的灯丝电流数值；根据部分灯丝电流数值拟合得到系统所有的灯丝电流数值；通过CT系统中的训管优化灯丝电流校正时间；通过CT系统中的日常扫描预热协议进行灯丝电流校正预警显示。应用本发明的方法进行灯丝电流校正后,能够对CT系统的扫描成像以及硬件稳定起到基础保障作用。(The invention discloses a CT system based on filament current calibration in a CT bulb tube and a calibration method thereof, wherein the CT system comprises a host, a fixed end of a CT frame, a rotating end of the CT frame, a correction system, a data acquisition system, an image building system and a workstation. The calibration method of the filament current in the CT bulb tube comprises the steps of obtaining a first correction condition; exposing and calculating a proper filament current value according to the first correction condition; sampling to obtain a plurality of proper filament current values; fitting according to the partial filament current values to obtain all filament current values of the system; optimizing filament current correction time through a training tube in a CT system; and performing filament current correction early warning display through a daily scanning preheating protocol in the CT system. After the method is used for filament current correction, the method can play a basic role in ensuring the scanning imaging and hardware stability of the CT system.)

1. The utility model provides a CT system based on filament current calibration in CT bulb which characterized in that: which comprises

The host is responsible for the interaction between the system and the user, issues the workflow required by the user to the whole system and feeds back the result to the user;

the CT rack fixing end is responsible for receiving the instruction sent by the host and controlling the work of the whole hardware system;

the CT frame rotating end receives a command transmitted by the CT frame fixed end through the slip ring;

the correction system is responsible for the overall correction and calibration work of the CT system, the CT system works in a good state by adjusting each part of the CT system, and simultaneously, a series of correction tables are generated by correction according to the characteristics of the CT system, and the correction tables are used for reconstructing the preprocessing stage of the system, so that the CT system generates a tomographic image with low noise and high contrast;

the data acquisition system is responsible for receiving a data acquisition instruction of the host, receiving original raw data generated by hardware through the DMS and storing the original raw data on the hard disk;

the image building system is used for receiving a reconstruction instruction of the host, reading original raw data acquired by the data acquisition system, using a correction table generated by the correction system, reconstructing an image through a computed tomography technology and feeding back the image to the host;

and the host computer can send the images reconstructed by the reconstruction system to the workstation according to the requirements of users for diagnosis.

2. The CT system according to claim 1, wherein the CT system is based on filament current calibration in a CT bulb, and comprises: the host machine issues a scanning workflow to the fixed end of the CT frame and issues an image establishing workflow to an image establishing system; issuing a correction workflow to a correction system; and the feedback of the above components is displayed to the user, and the result is stored in a database, a file and a server.

3. The CT system according to claim 1, wherein the CT system is based on filament current calibration in a CT bulb, and comprises: the fixed end of the CT rack comprises a scanning bed system and a rotating motor, is a core brain of CT hardware and is responsible for integral scheduling work; the CT frame rotating end comprises a collimator control system, a DMS data acquisition system, a high-voltage control system and a bulb tube, the CT frame rotating end serves as a core computing unit of CT hardware, data required by a reconstruction system are generated through exposure of the high-voltage control system and data acquisition of the DMS system, the data are transmitted to the data acquisition system through a slip ring and a data acquisition card, and then the data are applied to the reconstruction system to carry out image preprocessing and reconstruction.

4. A method for calibrating a filament current in a CT bulb of a CT system according to claim 1, wherein: which comprises the following steps:

1) acquiring a first correction condition;

2) exposing and calculating a proper filament current value according to the first correction condition;

3) sampling to obtain a plurality of proper filament current values;

4) fitting according to the partial filament current values to obtain all filament current values of the system;

5) optimizing filament current correction time through a training tube in a CT system;

6) and performing filament current correction early warning display through a daily scanning preheating protocol in the CT system.

5. The method for calibrating the filament current in the CT bulb according to claim 4, wherein: the first correction condition obtained in the step 1) specifically refers to a bulb voltage value, a bulb current value and an initial filament current value; the step 2) specifically refers to exposure according to a set bulb voltage value, a bulb current value and an initial filament current value, and an actual appropriate filament current value is calculated according to a feedback filament current value curve.

6. The method for calibrating the filament current in the CT bulb according to claim 4, wherein: sampling all exposure conditions in the system in the step 3), including bulb voltage and bulb current, selecting a small number of points for exposure calculation, and respectively obtaining corresponding appropriate filament current values; and 4) carrying out nonlinear fitting on the appropriate filament current numerical value obtained by sampling exposure calculation in the step 4) so as to obtain the filament current numerical value of the system under all exposure conditions.

7. The method for calibrating the filament current in the CT bulb according to claim 4, wherein: the tube training operation of the CT bulb tube in the step 5) is an indispensable link for system initialization and installation, and the data acquisition of filament current correction is combined in the process, so that the correction time of the filament current can be greatly reduced; the daily scanning preheating protocol of the CT bulb tube in the step 6) is one of the most frequently used parts in the system, the system performs necessary data acquisition of a filament current part during preheating, and whether the user needs to be prompted to update filament current correction is judged by judging the value of the filament current at the moment.

8. The method for calibrating the filament current in the CT bulb according to claim 4, wherein: the method comprises the following specific steps:

obtaining bulb tube voltage, bulb tube current, bulb tube focus size and filament current curves provided by a bulb tube manufacturer, counting initial curve values of a plurality of hardware, and carrying out average calculation to obtain initial filament ammeter values;

acquiring a first scanning condition comprising bulb tube voltage, bulb tube current, focus size and filament current numerical value, exposing, acquiring corresponding filament current feedback numerical value as first data, and acquiring corresponding bulb tube current feedback numerical value as second data;

according to the first data, analyzing the curve characteristics in the first data, acquiring the wave crests and wave troughs of the first data curve, and recording the time information corresponding to the wave crests and wave troughs;

according to the first data and the second data, analyzing curve characteristics in the first data and the second data, acquiring a first time point corresponding to the stable start of the filament current in the first data and a second time point corresponding to the stable start of the bulb tube current in the second data, comparing the first time point with the second time point, and taking the earlier time point as the start time point of the stable exposure of the system;

judging whether the starting time point of stable exposure is smaller than an ideal value, defaulting to 40ms, if so, determining that the filament current reaches the requirement, and determining that the filament current value is qualified under the condition;

judging whether the starting time point of stable exposure is smaller than an ideal value, defaulting to 40ms, if so, determining that the filament current does not meet the requirement, and performing iterative exposure to meet the convergence condition;

during iterative exposure, the filament current value needs to be updated every time, and the direction of adjusting the next filament current is determined by judging the position of the peak and the trough and the absolute difference value of the stable filament current;

during iterative exposure, the amplitude of each adjustment of the filament current uses a bisection method to ensure convergence and correction speed of a filament current correction process;

after the current-condition filament current is corrected to be qualified, performing the same operation on all sampling points in the system to obtain the proper filament currents of all the sampling points;

and performing nonlinear fitting on the filament currents of all sampling points to obtain the appropriate filament currents under all conditions, wherein the nonlinear fitting is generally polynomial fitting, exponential fitting or power function fitting.

9. The method for calibrating the filament current in the CT bulb according to claim 4, wherein: it also includes the following steps:

in the CT system, after the CT bulb tube is installed, tube training operation is required, and miscellaneous gas in the bulb tube is removed;

the tube training operation needs a large amount of exposure operation, the exposure conditions during the operation, including bulb voltage, bulb current and exposure times, can cover a plurality of sampling points, wherein the number of the exposure times under a single condition ensures that convergence can be obtained within the times;

when the tube training operation is performed, a data acquisition system needs to be controlled, exposure data which are the same as filament current correction are acquired, iterative calculation is performed, and appropriate filament current values under different conditions are obtained;

after the tube training operation is finished, nonlinear fitting is carried out according to sampling points used in the tube training process and corresponding filament current convergence values to obtain appropriate filament currents under all conditions;

the method originally integrates the filament current correction into other necessary system correction links, reduces the system correction time, saves the correction steps and optimizes the procedure during the initial installation of the system.

10. The method for calibrating the filament current in the CT bulb according to claim 4, wherein: it also includes the following steps:

in the CT system, preheating is an indispensable daily step before the system performs scanning imaging;

collecting related data of filament current correction in the preheating process;

judging whether the filament current meets the condition or not according to the collected filament current data, and when the filament current does not meet the condition and needs to be updated in an iteration mode, carrying out early warning prompt on a user, wherein the early warning information is that the current filament current has a deviation, and correcting the system.

Technical Field

The invention belongs to the field of medical systems, and particularly relates to a method and a system for calibrating filament current in a CT bulb tube in a computed tomography system.

Background

The X-ray is an electromagnetic wave with extremely short wavelength and large energy, the wavelength of the X-ray is shorter than that of visible light, and the photon energy of the X-ray is tens of thousands to hundreds of thousands times larger than that of the visible light. It was discovered by german physicist w.k. roentgen in 1895, so it is also called roentgen ray. X-rays are currently widely used in medical imaging diagnostics.

The CT bulb tube radiates X-rays which reach the detector after being attenuated by the human body, and reconstruction from projection data to a human body tomographic image is realized through a computed tomography technology.

The CT bulb is one of the most central key components in a computed tomography system, and is actually a large high vacuum cathode ray diode having a cathode and an anode, with a filament disposed on the cathode. In the working process of the CT bulb tube, current is added to a cathode filament, so that the filament is heated and generates a free electron cloud set, then high voltage is added to the anode and the cathode, the potential difference between the anode and the cathode is increased sharply, free electron beams in an active state on the cathode filament impact an anode tungsten target and generate energy conversion under the drive of a high-voltage strong electric field, one part of electric energy is converted into X rays and emitted by a window, and the other part of electric energy is converted into heat energy and emitted by a heat dissipation system. The current supplied to the cathode filament is referred to as a filament current, the voltage between the cathode and anode is referred to as a bulb voltage, and the current generated by electrons generated by heating the filament moving at high speed to the anode under the action of the high-voltage electric fields of the cathode and anode is referred to as a bulb current (also referred to as mA).

Before each CT bulb is used, the corresponding relationship between the tube current and the filament current needs to be calibrated, and the currently common method includes the following steps:

the method comprises the steps that firstly, exposure is carried out on each working point of filament current, corresponding tube current values are obtained through testing, and due to the fact that the number of the working points is large, the corresponding relation between the tube current and the filament current can be obtained through a large number of tests, and the filament current of an X-ray tube is calibrated;

secondly, directly using relevant parameters provided by manufacturers, wherein the parameters do not need to be corrected relative to the above process, but are slightly poor in accuracy and precision, and because a high-voltage system matched with the filament current provided by a bulb manufacturer is probably different from a high-voltage system used by the manufacturer of the medical apparatus, the modulation modes of the filament current in the high-voltage system are also different;

and thirdly, calculating by using partial scanning conditions, and still using preheating and training tubes of the system and filament current correction as a non-interference independent system, wherein along with the convergence condition of the previous filament current, the subsequent independent filament current correction conditions are more accurate and the iteration speed is higher, but no corresponding related optimization scheme exists in the currently seen design scheme.

Disclosure of Invention

The objects of the present invention include the following: the problem of extra dosage suffered by a patient due to overlong filament current stabilization time during actual scanning reconstruction is solved; the problems that the traditional filament current excessively depends on factory parameters and the correction exposure times of the filament current are excessive are solved; the flow and efficiency of filament current correction are optimized and solved from the system level; the problem of how to give an early warning in time when the filament current has a problem in the clinical use process of the system is solved from the system level.

The technical scheme adopted by the invention for realizing the purpose is as follows:

a CT system based on the filament current calibration in CT bulb tube includes

The host is responsible for the interaction between the system and the user, issues the workflow required by the user to the whole system and feeds back the result to the user;

the CT rack fixing end is responsible for receiving the instruction sent by the host and controlling the work of the whole hardware system;

the CT frame rotating end receives a command transmitted by the CT frame fixed end through the slip ring;

the correction system is responsible for the overall correction and calibration work of the CT system, the CT system works in a good state by adjusting each part of the CT system, and simultaneously, a series of correction tables are generated by correction according to the characteristics of the CT system, and the correction tables are used for reconstructing the preprocessing stage of the system, so that the CT system generates a tomographic image with low noise and high contrast;

the data acquisition system is responsible for receiving a data acquisition instruction of the host, receiving original raw data generated by hardware through the DMS and storing the original raw data on the hard disk;

the image building system is used for receiving a reconstruction instruction of the host, reading original raw data acquired by the data acquisition system, using a correction table generated by the correction system, reconstructing an image through a computed tomography technology and feeding back the image to the host;

and the host computer can send the images reconstructed by the reconstruction system to the workstation according to the requirements of users for diagnosis.

Preferably, the host issues a scanning workflow to the fixed end of the CT frame and an imaging workflow to the imaging system; issuing a correction workflow to a correction system; and the feedback of the above components is displayed to the user, and the result is stored in a database, a file and a server.

Preferably, the fixed end of the CT gantry comprises a scanning bed system and a rotating motor, which are core brains of CT hardware and are responsible for overall scheduling work; the CT frame rotating end comprises a collimator control system, a DMS data acquisition system, a high-voltage control system and a bulb tube, the CT frame rotating end serves as a core computing unit of CT hardware, data required by a reconstruction system are generated through exposure of the high-voltage control system and data acquisition of the DMS system, the data are transmitted to the data acquisition system through a slip ring and a data acquisition card, and then the data are applied to the reconstruction system to carry out image preprocessing and reconstruction.

A method for calibrating filament current in a CT bulb tube comprises the following steps:

1) acquiring a first correction condition;

2) exposing and calculating a proper filament current value according to the first correction condition;

3) sampling to obtain a series of appropriate filament current values;

4) fitting according to the partial filament current values to obtain all filament current values of the system;

5) optimizing filament current correction time through a training tube in a CT system;

6) and performing filament current correction early warning display through a daily scanning preheating protocol in the CT system.

Preferably, the first correction condition obtained in step 1) specifically refers to a bulb voltage value, a bulb current value and an initial filament current value; the step 2) specifically refers to exposure according to a set bulb voltage value, a bulb current value and an initial filament current value, and an actual appropriate filament current value is calculated according to a feedback filament current value curve.

Preferably, in the step 3), all exposure conditions in the system, including the bulb voltage and the bulb current, are sampled, a small number of points are selected for exposure calculation, and corresponding appropriate filament current values are obtained respectively; and 4) carrying out nonlinear fitting on the appropriate filament current numerical value obtained by sampling exposure calculation in the step 4) so as to obtain the filament current numerical value of the system under all exposure conditions.

Preferably, the tube training operation of the CT bulb in the step 5) is an indispensable link for system initialization and installation, and the data acquisition of filament current correction is combined into the process, so that the correction time of the filament current can be greatly reduced; the daily scanning preheating protocol of the CT bulb tube in the step 6) is one of the most frequently used parts in the system, the system performs necessary data acquisition of a filament current part during preheating, and whether the user needs to be prompted to update filament current correction is judged by judging the value of the filament current at the moment.

A method for calibrating filament current in a CT bulb tube comprises the following specific steps:

obtaining bulb tube voltage, bulb tube current, bulb tube focus size and filament current curves provided by a bulb tube manufacturer, counting initial curve values of a plurality of hardware, and carrying out average calculation to obtain initial filament ammeter values;

acquiring a first scanning condition comprising bulb tube voltage, bulb tube current, focus size and filament current numerical value, exposing, acquiring corresponding filament current feedback numerical value as first data, and acquiring corresponding bulb tube current feedback numerical value as second data;

according to the first data, analyzing the curve characteristics in the first data, acquiring the wave crests and wave troughs of the first data curve, and recording the time information corresponding to the wave crests and wave troughs;

according to the first data and the second data, analyzing curve characteristics in the first data and the second data, acquiring a first time point corresponding to the stable start of the filament current in the first data and a second time point corresponding to the stable start of the bulb tube current in the second data, comparing the first time point with the second time point, and taking the earlier time point as the start time point of the stable exposure of the system;

judging whether the starting time point of stable exposure is smaller than an ideal value, defaulting to 40ms, if so, determining that the filament current reaches the requirement, and determining that the filament current value is qualified under the condition;

judging whether the starting time point of stable exposure is smaller than an ideal value, defaulting to 40ms, if so, determining that the filament current does not meet the requirement, and performing iterative exposure to meet the convergence condition;

during iterative exposure, the filament current value needs to be updated every time, and the direction of adjusting the next filament current is determined by judging the position of the peak and the trough and the absolute difference value of the stable filament current;

during iterative exposure, the amplitude of each adjustment of the filament current uses a bisection method to ensure convergence and correction speed of a filament current correction process;

after the current-condition filament current is corrected to be qualified, performing the same operation on all sampling points in the system to obtain the proper filament currents of all the sampling points;

and performing nonlinear fitting on the filament currents of all sampling points to obtain the appropriate filament currents under all conditions, wherein the nonlinear fitting is generally polynomial fitting, exponential fitting or power function fitting.

Preferably, the method for calibrating the filament current in the CT bulb further comprises the following steps:

in the CT system, the CT bulb tube is subjected to tube training operation according to the later requirement, and miscellaneous gases in the bulb tube are removed;

the tube training operation needs a large amount of exposure operation, the exposure conditions during the operation, including bulb voltage, bulb current and exposure times, can cover a plurality of sampling points, wherein the number of the exposure times under a single condition ensures that convergence can be obtained within the times;

when the tube training operation is performed, a data acquisition system needs to be controlled, exposure data which are the same as filament current correction are acquired, iterative calculation is performed, and appropriate filament current values under different conditions are obtained;

after the tube training operation is finished, nonlinear fitting is carried out according to sampling points used in the tube training process and corresponding filament current convergence values to obtain appropriate filament currents under all conditions;

the method originally integrates the filament current correction into other necessary system correction links, reduces the system correction time, saves the correction steps and optimizes the procedure during the initial installation of the system.

Preferably, the method for calibrating the filament current in the CT bulb further comprises the following steps:

in the CT system, preheating is an indispensable daily step before the system performs scanning imaging;

collecting related data of filament current correction in the preheating process;

judging whether the filament current meets the condition or not according to the collected filament current data, and when the filament current does not meet the condition and needs to be updated in an iteration mode, carrying out early warning prompt on a user, wherein the early warning information is that the current filament current has a deviation, and correcting the system.

The invention has the following beneficial effects and advantages:

the system scanning quickly reaches a stable state through filament current correction, and the image quality is ensured from a ray source; the filament current correction of partial scanning conditions is carried out by sampling all scanning conditions of the system, and then all scanning conditions are fitted, so that the problems that the traditional filament current correction exposure times are too many and the correction time is too long are solved; the filament current correction efficiency is optimized from the system level, the filament current correction and the bulb tube training operation are one of the indispensable processes in the initial installation of the CT system, in the traditional situation, the filament current correction and the bulb tube training operation are separated from each other and are processed, so that the time and the exposure times of the bulb tube are wasted, and the filament current process is combined into the tube training process by organically combining the filament current correction and the bulb tube training operation; in the use process of the system, the preheating process every day can be monitored, when the problem of the filament current is found, the filament current is timely informed to a user, and the patient is prevented from receiving extra exposure which cannot meet the image quality requirement.

Drawings

FIG. 1 is a wiring diagram of components of a CT system of the present invention;

FIG. 2 is a flowchart of a method for calibrating a filament current of a CT bulb according to the present invention;

FIG. 3 is a flow chart of single-condition filament current correction in the present invention;

FIG. 4 is a flowchart of the multi-condition filament current calibration of the present invention;

FIG. 5 is a flowchart of the present invention combining a training tube process with filament current calibration;

FIG. 6 is a flow chart of the preheating of the present invention;

Detailed Description

In order to more clearly explain the technical solution, implementation process and related factors of the present invention, the following describes the present invention in detail with reference to the accompanying drawings and embodiments.

The system relates to a CT bulb tube filament current correction method (as shown in figure 2) and an optimized correction flow scheme in the computed tomography technology, and the method can be applied to the filament current correction of a CT system.

As shown in FIG. 1, FIG. 1 illustrates several important components of a third generation CT system, including:

the host 101 is responsible for interaction between the system and the user, issues a workflow required by the user to the whole system, and feeds back a result to the user; typically, the method comprises the steps of sending a scanning workflow to the fixed end 102 of the CT frame, and sending an imaging workflow to the imaging system 106; issuing a correction workflow to the correction system 104; the feedback of the system is displayed to the user, and necessary storage results are stored in a database, a file, a server and the like;

the CT rack fixing end 102 is responsible for receiving the instruction issued by the host 101 and controlling the work of the whole hardware system, including the CT rack rotating end 103, the scanning bed system, the rotating motor and the like, which are the core brain of the CT hardware and are responsible for the overall scheduling work;

the CT frame rotating end 103 receives an instruction transmitted by the CT frame fixed end 102 through the slip ring, the rotating end comprises a collimator control system, a DMS data acquisition system, a high-voltage control system, a bulb tube and the like, the CT frame rotating end 103 is equivalent to a core calculation unit of CT hardware, data required by a reconstruction system 106 are generated through exposure of the high-voltage control system and data acquisition of the DMS system, and are transmitted to a data acquisition system 105 through the slip ring and a data acquisition card, and then the data acquisition system is applied to the reconstruction system 106 to perform image preprocessing and reconstruction;

the correction system 104 is responsible for the overall correction and calibration of the CT system, which is equivalent to make the CT system work in a good state by adjusting various CT system subcomponents, and simultaneously correct and generate a series of correction tables according to the characteristics of the CT system, and the correction tables are used in the preprocessing stage of the reconstruction system 106, so that the CT system generates a tomographic image with low noise and high contrast;

the data acquisition system 105 is responsible for receiving a data acquisition instruction of the host 101, receiving original raw data generated by hardware through a DMS (digital distribution system) and storing the original raw data on the hard disk;

the image creating system 106 is responsible for receiving a reconstruction instruction of the host 101, reading original raw data acquired by the data acquisition system 105, reconstructing an image by using a correction table generated by the correction system 104 through a computed tomography technology, and feeding back the image to the host 101;

the workstation 108, the host 101, after receiving the image reconstructed by the reconstruction system 106, can send the image to the workstation 108 for diagnosis according to the user's requirements.

As shown in fig. 3, the single-condition filament current correction process includes the following steps:

s1, obtaining an average filament current table stored in the system, the table is obtained 202 from experience of the previous system, generally speaking, 10 left and right prototypes of the same high voltage system and the same bulb tube system can be taken to obtain the filament current after correction of each machine, and then the filament current tables of the machines are averaged, which is the initial average filament current table stored in the system of the whole system;

and S2, acquiring a first group of scanning conditions, including bulb voltage, bulb current, focus size and filament current original value, as first correction conditions.

In S2, it should be noted that the filament current is not only related to the bulb voltage and the bulb current, but also directly related to the size of the focus, and generally, under the same conditions of the bulb voltage and the bulb current, the filament current corresponding to the small focus is larger than the filament current corresponding to the large focus;

s3, exposing the first calibration condition, and collecting feedback data, which at least includes an integration time, a filament current curve, a mA curve, and a kV curve, where the integration time is generally in units of milliseconds or higher precision, the filament current curve includes an oscillation period of the filament current and a stabilization period of the filament current, the filament current curve can laterally reflect the initial filament current setting, and the larger the oscillation amplitude is, the longer the oscillation period is, the larger the deviation of the filament current value setting under the first calibration condition from an ideal value can be considered;

s4, calculating a stable value of the filament current curve, recording a timestamp when the filament current is initially stable, recording the timestamp as a first calculation, in the first calculation, firstly, smoothing the filament current to eliminate the influence of burrs, then, selecting the average value of 30% of data behind the filament current curve as a filament current value of a stable period, reading a filament current error threshold, and calculating to obtain the timestamp when the filament current is initially stable;

s5, judging whether the first calculation result reaches a stable state, if so, indicating that the current filament current value is appropriate, and finishing the correction, wherein the current value is the appropriate filament current value; if the steady state is not reached, the subsequent iterative corrections need to be continued.

The criterion for determining whether the steady state is reached in S5 is whether the timestamp of the filament current stabilization is less than a system expectation, such as 40ms or less for a system design, which is system-specific.

S6, calculating the peak value and the trough value of the filament current and the corresponding time stamp, and recording as a second calculation; filament current curve has the curve similar to damping motion before reaching steady state, through simple contrast operation or derivation operation, all can find a plurality of crest troughs in the system, need record the position of crest trough and corresponding time stamp in the second calculation.

In S6, it is particularly noted that although the filament current curve is smoothed in the foregoing, some small peaks and valleys should not be included in the system, and therefore two points of maximum peak amplitude and minimum valley amplitude are considered as important points and are marked as characteristic points of the filament current curve;

s7, the filament current adjustment direction may be adjusted as a third calculation according to the second calculation result and the characteristic point of the filament current curve.

In S7, when the characteristic point of the filament current curve is found, the timestamp corresponding to the peak is smaller than the timestamp corresponding to the valley, which indicates that the filament current value may be smaller when the original exposure collection is performed, because the high-voltage control system finds that the set condition is smaller, the system characteristic will pull up the value first, so as to reach the stable filament current quickly, and further reach the stable bulb tube current.

On the contrary, in S7, in the filament current curve characteristic point, the timestamp that the crest corresponds is greater than the timestamp that the trough corresponds, and it is probably bigger than the filament current numerical value when originally carrying out exposure collection, because the condition that high voltage control system found its setting is bigger than a bit, the system characteristic will pull down its numerical value earlier to reach stable filament current fast, and then reach stable bulb electric current.

And S8, calculating to obtain a new filament current by using a dichotomy and combining with a third calculation. The dichotomy is used for the purpose of rapidly converging the filament current value correction under this condition.

After the calculation at S8 is completed, the process proceeds to step S3, and the process is iterated.

And S9, combining the calculation methods of S8 and S5 to judge whether the iteration process is finished.

S3 to S9, if convergence is reached, the correction is successfully ended. If the maximum iteration number is reached and the correction is still not converged, the condition correction is failed.

As shown in fig. 4, the multi-condition filament current correction process includes the following steps:

s11, all scanning conditions of the system are sampled, and a partial correction condition list is obtained.

All scan conditions referred to in S11 are conditions that affect the filament current component values, including bulb voltage, bulb current, and focus size, excluding other imaging system 106 corresponding conditions, such as collimation system parameters.

In S11, sampling all conditions, wherein in a general CT system, the number of kV is 3 to 5, the focus is 1 to 2, and the change range of bulb tube current is 5mA to 670mA, so that the prior sampling object is bulb tube current, and the number of sampling points is 3 to 5mA according to the type of the finally fitted curve;

and S12, acquiring a first group of scanning conditions including bulb voltage, bulb current, focus size and filament current original values as second correction conditions.

S13, carrying out correction calculation on the second correction according to the process from S1 to S9 to obtain a second correction result;

and S14, comparing the initial filament current correction table according to the second correction result, and updating the subsequent filament current default value.

In S14, the purpose of updating the subsequent filament current default values is to make the subsequent filament current corrections converge faster per reduction in the number of scans. The fundamental reason for this is that the shape of the filament current curve is generally fixed, and when one point is shifted, other points are similarly shifted.

In S14, the formula for updating the values of the other filament ammeters is as follows:

Filame nt_new＝Filame nt_old+Filame nt_offset

wherein: filame nt_offsetIs the difference between the second correction result and the default filament current value;

Filame nt_olddefault filament current values for other conditions;

Filament_newupdated filament current values for other conditions;

and S15, acquiring subsequent scanning conditions including bulb voltage, bulb current, focus size and filament current original value as third correction conditions.

And S16, calculating a third corrected filament current correction result through iterative scanning to obtain the third corrected filament current correction result.

And S17, comparing the initial filament current correction table according to the second filament correction result and the third correction result, and updating the subsequent filament current default value. The manner of updating also refers to the formula in S14.

After the processes from S15 to S17 are finished, it is necessary to refer to the updating manner of the filament ammeter values in the processes from S12 to S14 to continuously update the other filament current values that are not scanned, so as to achieve faster convergence, reduce the exposure times of the system, and save the exposure time.

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

f(x)＝a_n*xⁿ+a_n-1*x^n-1+a_n-2*x^n-2+...+a₀

f(x)＝a*x^b+c

f(x)＝a*e^bx+c

A, b, c, a in the above formula_nAre all fitting coefficients; in S18, three fitting formulas, different CT systems, different bulbs, different high voltages, and different applicable formulas may be different, but the principles are similar, so that the formula needs to be adapted and selected according to actually adopted data.

As shown in fig. 5, the flowchart combining the tube training process and the filament current correction includes the following steps:

s21, similar to the multi-conditional filament current correction, a training tube exposure condition list is obtained.

In S21, the exposure condition of each training tube needs to be performed several times, which are greater than the number of general iterations of filament current correction, so that the filament current correction exposure time and the exposure number can be reduced by using the single condition.

In S21, the overall exposure conditions are combined a lot, and the requirements of S18 can be completely met under partial conditions, so that the filament current correction time can be greatly reduced.

And S22, exposing according to the sequence specified by the exposure condition list to ensure the correctness of the tube training process, wherein the process is to achieve the purpose of filament current correction by using the tube training operation, so the tube training process is ensured firstly.

S23, it should be noted that the current exposure condition does not reach the upper limit of the times, and the current filament current correction still does not obtain a proper result, at this time, the calculation may be iterated, so as to obtain the filament current value used in the next exposure.

In S23, it should be noted that, each exposure needs to retain the necessary data and then perform the calculation, and the calculation and the time for saving the data cannot affect the normal management workflow.

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

And S25, counting all the conditions and correction results of the filament current correction after the tube training is finished, and performing fitting calculation on the whole filament current correction result by combining S18.

S26, for the part can not reach the S18 calculation data volume requirement conditions, can carry on the independent condition supplementary scanning, even this, can also reduce the filament current and expose the number of times greatly.

As shown in FIG. 6, the CT system bulb preheating flow chart comprises the following steps.

S31, similar to the multi-conditional filament current correction, a preheat exposure condition list is acquired.

S32, the exposure conditions in the list are acquired and exposed in the specified order while paying attention to the raw data required to preserve the filament current.

And S33, acquiring the filament current under the current exposure condition while exposing, and combining the data to continue the filament current correction analysis.

S34, calculating whether the current filament current value is qualified or not, wherein the formula is as follows:

Delta＝abs(Filame nt_current-Filame nt_config)

wherein Filame nt_currentFilame nt, the current calculated appropriate filament current_configThe filament current obtained by filament current correction in the configuration file is Delta which is the difference between the absolute values of the two.

In S34, the threshold for determining whether the filament current is acceptable needs to be set reasonably, and if the threshold is set too harsh, unnecessary trouble may be caused to the user.

S35, when the calculated result Delta in S34 exceeds the threshold setting, the system prompts the user that a filament current correction update is required, otherwise an image may be affected.