CN108013887B

CN108013887B - Automatic exposure control method and device and automatic exposure system

Info

Publication number: CN108013887B
Application number: CN201610972767.XA
Authority: CN
Inventors: 李海春; 刘玉东; 李焕文
Original assignee: Beijing Neusoft Medical Equipment Co Ltd
Current assignee: Beijing Neusoft Medical Equipment Co Ltd
Priority date: 2016-10-28
Filing date: 2016-10-28
Publication date: 2020-09-11
Anticipated expiration: 2036-10-28
Also published as: CN108013887A

Abstract

The embodiment of the invention discloses an automatic exposure control method, which is applied to an X-ray machine and comprises the following steps: sending the initial tube voltage and the initial tube current to a high-voltage generator so that the high-voltage generator emits X rays according to the initial tube voltage and the initial tube current to start exposure; detecting a feedback voltage generated by the ionization chamber to obtain a first comparison voltage; when the first comparison voltage is greater than or equal to the sampling voltage, obtaining a reference voltage; continuously detecting the feedback voltage generated by the ionization chamber to obtain a second comparison voltage; and when the second comparison voltage is greater than or equal to the reference voltage, the high-voltage generator is switched off, and the exposure is stopped. Therefore, the reference voltage is set according to the actual exposure process, so that the setting of the reference voltage is more reasonable, the accuracy of automatic exposure control can be ensured, an exposure image with ideal gray scale is obtained, the stability and reliability of the quality of the exposure image are ensured, and the condition that the reference voltage is set by experience in the prior art, namely underexposure or overexposure is avoided.

Description

Automatic exposure control method and device and automatic exposure system

Technical Field

The invention relates to the technical field of medical equipment, in particular to an automatic exposure control method and device and an automatic exposure system.

Background

In X-ray machines, the purpose of using Automatic Exposure Control (AEC) techniques is to obtain images of consistent and reliable quality. For a direct digital radiography system (DR system), under the condition of a certain X-ray quality, the imaging gray scale of a flat panel detector is proportional to the input X-ray dose of the detector. In addition, the imaging gray scale of the flat panel detector is also related to the magnitude of the tube voltage and the attenuation magnitude of the attenuation object. Under the same condition of the thickness of the attenuation object, the imaging gray scale of the flat panel detector is gradually increased along with the increase of the tube voltage. And under the condition of the same tube voltage, the thicker the attenuator, the greater the attenuation of the attenuator, and the lower the imaging gray scale of the flat panel detector. Therefore, in order to obtain an image with stable and reliable quality, for an object to be irradiated with small attenuation, the AEC technology is adopted to control the DR system to use a small dose for exposure; for the irradiated object with larger attenuation, AEC technology is adopted to control the DR system to use larger dose for exposure.

In a DR system, an ionization chamber is used to detect the X-ray dose reaching the detector. Thus, the AEC technology can cut off the radiation of X-rays according to the feedback signal detected by the ionization chamber so as to control the dosage reaching the flat panel detector and obtain images with stable and reliable quality. Therefore, a person skilled in the art needs to set a series of target doses corresponding to the gray scales of target images for the objects to be irradiated with different thicknesses, and control the image quality by controlling the X-ray dose reaching the detector. However, in actual operation, since the skilled person cannot accurately estimate the attenuation of the object to be irradiated, the skilled person can only refer to the data such as the thickness of the object to be irradiated (e.g. the selected exposure protocol, the type of the object to be irradiated, the height and size of the patient, etc.), and set the corresponding X-ray input dose according to experience, and the stability and reliability of the image quality cannot be ensured.

Disclosure of Invention

In view of the above, the present invention provides an automatic exposure control method and apparatus, and an automatic exposure system, which can solve the problem in the prior art that the stability and reliability of the image quality cannot be ensured due to the fact that the X-ray dose reaching the detector cannot be accurately set.

The embodiment of the invention provides an automatic exposure control method, which is applied to an X-ray machine, wherein the X-ray machine comprises the following steps: a high voltage generator, a detector and an ionization chamber; the X-ray emitted by the high-voltage generator reaches the detector through a target to be irradiated, the detector images according to the reached X-ray, and the ionization chamber generates a feedback voltage according to the X-ray dosage reaching the detector; the method comprises the following steps:

sending an initial tube voltage and an initial tube current to the high-voltage generator so that the high-voltage generator emits X-rays according to the initial tube voltage and the initial tube current to start exposure;

detecting a feedback voltage generated by the ionization chamber to obtain a first comparison voltage;

when the first comparison voltage is greater than or equal to a sampling voltage, obtaining a reference voltage, wherein the reference voltage is greater than the sampling voltage;

continuously detecting the feedback voltage generated by the ionization chamber to obtain a second comparison voltage;

and when the second comparison voltage is greater than or equal to the reference voltage, switching off the high-voltage generator and stopping exposure.

Preferably, the obtaining of the reference voltage includes:

acquiring a voltage model and the equivalent attenuation thickness of the illuminated object;

and inputting the equivalent attenuation thickness and the voltage of the exposure tube into the voltage model to obtain the reference voltage, wherein the voltage of the exposure tube is equal to the initial tube voltage or the voltage of the detection tube, and the voltage of the detection tube is detected when the first comparison voltage is greater than or equal to the sampling voltage.

Preferably, the obtaining the voltage model includes:

obtaining a sample set and constructing an initial model, wherein the sample set comprises a plurality of groups of samples, and each group of samples comprises a group of equivalent attenuation thicknesses, exposure tube voltages and reference voltages;

training the initial model using the sample set;

and obtaining the voltage model according to the trained initial model.

Preferably, the acquiring an equivalent attenuation thickness of the illuminated object includes:

obtaining a thickness model;

when the first comparison voltage is greater than or equal to the sampling voltage, recording the exposure duration time to obtain a first time;

inputting the sampling voltage, the initial tube current and the first time into the thickness model to obtain the equivalent attenuation thickness; or, inputting the sampling voltage, the voltage of the detection tube, the current of the detection tube and the first time into the thickness model to obtain the equivalent attenuation thickness;

the detection tube voltage is detected when the first comparison voltage is larger than or equal to the sampling voltage, and the detection tube current is detected when the first comparison voltage is larger than or equal to the sampling voltage.

Preferably, the obtaining of the thickness model includes:

obtaining a sample set and constructing an initial model, wherein the sample set comprises a plurality of groups of samples, and each group of samples comprises a group of equivalent attenuation thickness, exposure tube voltage, exposure tube current, exposure duration and reference voltage;

training the initial model using the sample set;

and obtaining the thickness model according to the trained initial model.

The embodiment of the invention also provides an automatic exposure control device, which is applied to an X-ray machine, wherein the X-ray machine comprises: a high voltage generator, a detector and an ionization chamber; the X-ray emitted by the high-voltage generator reaches the detector through a target to be irradiated, the detector images according to the reached X-ray, and the ionization chamber generates a feedback voltage according to the X-ray dosage reaching the detector; the apparatus, comprising: the device comprises a high-voltage control module, a voltage detection module, a first comparison module, a voltage acquisition module and a second comparison module;

the high-voltage control module is used for sending the initial tube voltage and the initial tube current to the high-voltage generator so that the high-voltage generator emits X rays according to the initial tube voltage and the initial tube current to start exposure; when the comparison result of the second comparison module is that the second comparison voltage is greater than or equal to the reference voltage, the high-voltage generator is cut off, and exposure is stopped;

the voltage detection module is used for detecting the feedback voltage generated by the ionization chamber to obtain a first comparison voltage; when the comparison result of the first comparison module is that the first comparison voltage is greater than or equal to the sampling voltage, continuously detecting the feedback voltage generated by the ionization chamber to obtain a second comparison voltage;

the first comparison module is used for comparing the magnitude relation between the first comparison voltage and the sampling voltage;

the voltage obtaining module is configured to obtain the reference voltage and send the reference voltage to the high-voltage control module when the comparison result of the first comparing module is that the first comparison voltage is greater than or equal to the sampling voltage, where the reference voltage is greater than the sampling voltage;

the second comparison module is used for comparing the magnitude relation between the second comparison voltage and the reference voltage.

Preferably, the voltage obtaining module includes: the voltage model acquisition submodule, the thickness acquisition submodule and the voltage calculation submodule are connected;

the voltage model obtaining submodule is used for obtaining a voltage model;

the thickness obtaining submodule is used for obtaining the equivalent attenuation thickness of the illuminated target;

the voltage calculation submodule is used for inputting the equivalent attenuation thickness and the exposure tube voltage into the voltage model to obtain the reference voltage, the exposure tube voltage is the initial tube voltage or the detection tube voltage, and the detection tube voltage is the tube voltage detected when the first comparison voltage is greater than or equal to the sampling voltage.

Preferably, the voltage model obtaining sub-module includes: the system comprises an initial submodule, a training submodule and a generating submodule;

the initial submodule is used for acquiring a sample set and constructing an initial model, the sample set comprises a plurality of groups of samples, and each group of samples comprises a group of equivalent attenuation thicknesses, exposure tube voltage and reference voltage;

the training submodule is used for training the initial model by utilizing the sample set;

and the generation submodule is used for obtaining the voltage model according to the trained initial model.

Preferably, the thickness acquisition submodule includes: the thickness model acquisition sub-module, the time recording sub-module and the thickness calculation sub-module are connected with the thickness calculation sub-module;

the thickness model obtaining submodule is used for obtaining a thickness model;

the time recording sub-module is used for recording the exposure duration time to obtain a first time when the comparison result of the first comparison module is that the first comparison voltage is greater than or equal to the sampling voltage;

the thickness calculation submodule is used for inputting the sampling voltage, the initial tube current and the first time into the thickness model to obtain the equivalent attenuation thickness; or, the thickness submodule is used for inputting the sampling voltage, the voltage of the detection tube, the current of the detection tube and the first time into the thickness model to obtain the equivalent attenuation thickness;

Preferably, the thickness model obtaining submodule includes: the system comprises an initial submodule, a training submodule and a generating submodule;

the initial submodule is used for acquiring a sample set and constructing an initial model, the sample set comprises a plurality of groups of samples, and each group of samples comprises a group of equivalent attenuation thickness, exposure tube voltage, exposure tube current, exposure duration and reference voltage;

and the generation submodule is used for obtaining the thickness model according to the trained initial model.

The embodiment of the invention also provides an automatic exposure system which is applied to the X-ray machine; the system, comprising: the device comprises a high-voltage generator, a detector, an ionization chamber, a comparator and a controller;

the controller is used for sending the initial tube voltage and the initial tube current to the high-voltage generator; when the first comparison result is that the feedback voltage is greater than or equal to the sampling voltage, obtaining a reference voltage, and sending the reference voltage to the comparator, wherein the reference voltage is greater than the sampling voltage; when the second comparison result is that the feedback voltage is greater than or equal to the reference voltage, cutting off the X-rays emitted by the high-voltage generator and stopping exposure;

the high voltage generator is used for emitting X rays to the detector according to the initial tube voltage and the initial tube current and starting exposure;

the detector is used for sensing the arriving X-ray and imaging according to the arriving X-ray;

the ionization chamber is used for generating the feedback voltage according to the X-ray dosage reaching the detector and sending the feedback voltage to the comparator;

the comparator is used for comparing the magnitude relation between the feedback voltage and the sampling voltage to obtain a first comparison result, and sending the first comparison result to the controller; and comparing the magnitude relation between the feedback voltage and the reference voltage to obtain a second comparison result, and sending the second comparison result to the controller.

Compared with the prior art, the invention has at least the following advantages:

according to the automatic exposure control method provided by the embodiment of the invention, the initial tube voltage and the initial tube current are set according to experience, and the high-voltage generator is controlled to emit X rays to start exposure according to the initial tube voltage and the initial tube current. Thereafter, a feedback voltage generated by the ionization chamber is detected. When the feedback voltage is greater than or equal to the sampling voltage, the reference voltage is acquired according to parameters (such as attenuation of the object to be irradiated, exposure conditions and the like) obtained and acquired in advance. And continuously detecting the feedback voltage generated by the ionization chamber, and judging the magnitude relation between the feedback voltage and the reference voltage. And when the feedback voltage is greater than the reference voltage, cutting off the power supply of the high-voltage generator and stopping exposure. Therefore, the reference voltage is set according to the actual exposure process, so that the setting of the reference voltage is more reasonable, the accuracy of automatic exposure control can be ensured, an exposure image with ideal gray scale is obtained, the stability and reliability of the quality of the exposure image are ensured, and the condition that the reference voltage is set by experience in the prior art, namely underexposure or overexposure is avoided.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1a is a schematic diagram of the architecture of a prior art AEC control system;

FIG. 1b is a schematic structural diagram of a conventional DR system in an actual working process;

FIG. 1c is a schematic diagram of the ionization chamber of a prior art DR system;

FIG. 2 is a schematic flow chart illustrating an embodiment of an automatic exposure control method according to the present invention;

fig. 3 is a schematic flowchart of a sample set obtaining method according to an embodiment of the present invention;

fig. 4 is a schematic flowchart of a scene example of an automatic exposure control method according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of an automatic exposure control apparatus according to an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of an automatic exposure system according to an embodiment of the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to FIG. 1a, a prior art AEC control system is shown. Existing AEC control systems include: high voltage generator 11, detector 12, ionization chamber 13, amplifier 14, comparator 15 and cut-off circuit 16.

Wherein the high voltage generator 11 is an X-ray generating device that emits X-rays through a bulb connected thereto. The X-rays pass through an attenuator to detector 12. The detector 12 is an imaging device that converts received X-rays into electric signals, and obtains an exposure image by imaging with a built-in reading circuit. Detector 12 (fig. 1c is a schematic view of the ionization chamber configuration). A grid can be arranged between the tube and the bulb to filter out the influence of scattered X-rays on the imaging result. The ionization chamber 13 is a detector for measuring ionizing radiation using the ionization effect of the ionizing radiation, and is generally placed between the detector 12 and an attenuator for detecting the X-ray dose reaching the detector 12. During exposure, the ionization chamber 13 is capable of converting received X-rays into a voltage signal that is proportional to the incident X-ray dose. Amplifier 14 is connected to ionization chamber 13 and comparator 15 and modulates the feedback signal of ionization chamber 13. The comparator 15 is responsible for comparing the preset reference voltage Vref with the modulated feedback signal, and triggering the cut-off circuit 16 according to the comparison result. The cutoff circuit 16 is responsible for cutting off the high voltage generator 11. Fig. 1b shows a schematic structural diagram of a conventional DR system in an actual operation process.

In practical applications, a person skilled in the art empirically sets the exposure dose, which corresponds to a reference voltage Vref, for different targets to be irradiated in advance. During exposure, ionization chamber 13 accumulates the X-ray dose received by detector 12 and converts the dose into a voltage signal. The voltage signal is converted to a comparison voltage by an amplifier 14. The comparison voltage gradually increases with the accumulation of X-ray irradiation. When the comparison voltage exceeds the reference voltage Vref, the shutdown circuit 16 is triggered. The cutoff circuit 16 cuts off the high voltage generator 11 to terminate the exposure. The image obtained by the detector 12 is thus the image obtained according to the desired dose setting.

However, since the attenuation of the object to be illuminated cannot be accurately estimated by those skilled in the art, the reference voltage Vref can only be empirically set in advance. This results in a dose of X-rays reaching the detector 12 that is not as expected, and does not ensure a stable and reliable image quality.

Therefore, the embodiment of the invention provides an automatic exposure control method, after exposure is started, the exposure process is monitored in real time, the attenuation of the illuminated target is accurately estimated according to a model obtained by pre-training, and the accurate response relation between the current exposure gray level and the reference voltage is obtained, so that the reference voltage is more reasonably set, the exposure accuracy is ensured, and the exposure image with ideal gray level is obtained. Therefore, in the actual working process of the X-ray machine, the automatic exposure control method can ensure that the gray scale of the finally obtained image is in line with the expectation, and the quality of the exposed image is stable and reliable.

In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, embodiments accompanying the drawings are described in detail below.

First, it should be noted that the automatic exposure control method and apparatus provided by the embodiments of the present invention are all applied to an X-ray machine. The X-ray machine comprises: a high voltage generator, a detector and an ionization chamber (the specific structure is similar to that shown in fig. 1a and 1b, and the detailed description is omitted); the X-ray emitted by the high-voltage generator reaches the detector through the irradiated object, the detector images according to the reached X-ray, and the ionization chamber generates a feedback voltage according to the X-ray dose reaching the detector.

The method comprises the following steps:

referring to fig. 2, the flowchart of the automatic exposure control method according to the embodiment of the present invention is schematically shown.

The automatic exposure control method provided by the embodiment comprises the following steps:

step S201: sending the initial tube voltage and the initial tube current to the high-voltage generator so that the high-voltage generator emits X rays according to the initial tube voltage and the initial tube current to start exposure;

it is understood that the magnitude of the tube voltage affects the penetration of the X-rays, i.e., the "quality" of the X-rays; the magnitude of the tube current affects how much X-rays are in a unit area, i.e. the "amount" of X-rays. The exposure conditions (i.e. tube voltage, tube current and exposure time) are set by those skilled in the art to realize the exposure of different objects to obtain exposure images with expected quality.

It should be noted here that, in the present various DR systems, some of the DR systems can adjust the tube voltage and the tube current during the exposure process, but some DR systems cannot adjust the tube voltage and the tube current during the exposure process. For DR systems that cannot adjust tube voltage and current during exposure, the set values of initial tube voltage and initial tube current have a significant impact on the quality of the exposed image. Under the condition of certain X-ray dose, if the used initial tube voltage is too small to expose a thicker irradiated object, the tube current is too large; however, when the tube voltage is too high to expose the portion with small thickness, the tube current is too low. This can result in undesirable quality of the resulting exposed image. For a DR system capable of adjusting the tube voltage and the tube current in the exposure process, although the adjustment range of the tube current is very wide, too small tube current can cause too long exposure time, and a patient easily moves or breathes in the exposure process, so that an exposed image is blurred, and the image quality is not high. Too large tube current can cause too short exposure time, which causes the precision of automatic exposure control to be reduced and the exposure to be inaccurate, and also can cause the quality of the exposed image to be unsatisfactory. Therefore, in the actual control process, the skilled person needs to specifically set the initial tube voltage and the initial tube current according to the actual situation.

Generally, the thickness of different parts of human body can be equivalent to the thickness of the mold body (generally made of polymethyl methacrylate) used in the automatic exposure calibration, and the equivalent attenuation thickness of the part can be obtained. At this time, the attenuation of the irradiated portion is the same as that of the phantom. Thus, the initial tube voltage and the initial tube current can be set according to the intermediate value of the body thickness of the irradiated part. It is understood that the initial tube voltage and the initial tube current may be set by those skilled in the art according to the height and weight of the patient and other values within the equivalent attenuation thickness range of the irradiated portion. Table 1 shows equivalent attenuation thickness ranges for several conventional illuminated sites.

TABLE 1 names of sites and equivalent attenuation thickness

Location of a body part	Equivalent attenuation thickness (cm)
		Head part	15-20
Chest part	15-20
		Abdomen correcting device	20-25
Abdomen side	25-35
		Knee joint	5-15
Foot part	3-8
		Hand part	1-5

For example, the initial tube voltage and the initial tube current may be set according to a setting of an Anatomy Program Radiography (APR) function preset on an X-ray machine. The APR function enables automatic setting of appropriate exposure conditions for different anatomical regions.

Step S202: detecting a feedback voltage generated by the ionization chamber to obtain a first comparison voltage;

it is noted that, as can be seen in fig. 1C, the ionization chamber is divided into a plurality of fields, namely a central C-field, a left L-field and a right R-field. In the practical application process, a person skilled in the art needs to select a field required to be induced by the ionizer according to the practical shooting requirement, and control the exposure process according to the feedback voltage of the selected field to ensure the image quality of the region of interest. For example, when taking a chest radiograph, the region where both lungs are located is usually selected as the region of interest, i.e., L field and R field; when the head image is shot, only the C field needs to be sensed. At the same time, the ionization chamber can also measure the X-ray dose received by each field on the detector. Therefore, in practical operation, the signals in the corresponding channels (L, R or C) are read according to the selection of the detector field in the current exposure process to obtain the feedback voltage generated by the ionization chamber, and obtain the first comparison voltage. In addition, since the feedback voltage of the ionization chamber is small, one skilled in the art can modulate the feedback voltage using an amplifier to amplify it into a voltage signal usable by the system. At this time, the first comparison voltage is an amplified feedback voltage.

Step S203: when the first comparison voltage is greater than or equal to a sampling voltage, obtaining a reference voltage, wherein the reference voltage is greater than the sampling voltage;

it is understood that the gray scale of the exposure image is related to the intensity of the X-ray (i.e., the tube voltage), the attenuation of the X-ray intensity by the object to be irradiated (i.e., the equivalent attenuation thickness of the object to be irradiated), and the exposure time. In the AEC control system, the exposure time is controlled by setting a reference voltage. Therefore, in order to ensure the stability and reliability of the quality of the exposure image, the accurate reference voltage needs to be obtained based on the tube voltage used in the actual exposure and the equivalent attenuation thickness of the object to be irradiated.

Specifically, when the first comparison voltage is greater than or equal to the sampling voltage, it can be regarded as one exposure performed with the sampling voltage as the reference voltage. At this time, the actual conditions in the exposure process, that is, the initial tube voltage, the equivalent attenuation thickness of the irradiated object, and the sampling voltage (that is, the reference voltage used in the exposure) can be obtained.

And then, a data model can be constructed in a sample training mode to obtain the corresponding relation among the tube voltage, the equivalent attenuation thickness of the illuminated object, the reference voltage and the image gray scale. And inputting the actually obtained initial tube voltage, the equivalent attenuation thickness of the irradiated object and the target gray scale of the exposure image into the data model, so as to obtain the reference voltage required by the exposure image with the target gray scale.

It should be noted that, those skilled in the art need to specifically set the sampling voltage according to actual situations. If the sampling voltage is too small, the influence of noise on the adjustment time is too large, the error of the obtained reference voltage is increased, and the quality of an exposure image is not ideal; the too large sampling voltage will cause the obtaining timing of the reference voltage to lag, and the obtaining timing is missed, which will also affect the exposure result. For example, an approximate reference voltage (e.g., an empirically estimated reference voltage in the prior art) may be first empirically derived and the sampled voltage set to 10% -50% of the approximate reference voltage.

In a preferred implementation of this embodiment, the obtaining the reference voltage includes:

step S2031: acquiring a voltage model and the equivalent attenuation thickness of the illuminated object;

specifically, the equivalent attenuation thickness of the target can be obtained empirically (e.g., the equivalent attenuation thickness of the target is set according to the equivalent attenuation thickness range given in table 1).

It should be noted that, a person skilled in the art can specifically obtain a relation model, i.e., a voltage model, between parameters such as equivalent attenuation thickness of an object to be irradiated, tube voltage, reference voltage, and gray scale of an exposure image in an exposure process through steps of data sampling, data fitting, regression, and the like.

In addition, other factors (e.g., X-ray energy, etc.) may also affect the exposure process. Therefore, on the basis of the equivalent attenuation thickness and the voltage of the exposure tube, the influence of other factors on the specific exposure process can be comprehensively considered to set the reference voltage, so that the accuracy of setting the reference voltage is further improved, and the stability of the quality of an exposed image is ensured. At this time, the influence of the above factors (such as X-ray energy) on the reference voltage setting needs to be considered in the voltage model.

As an example, the obtaining the voltage model includes:

the method comprises the steps of firstly, obtaining a sample set and constructing an initial model, wherein the sample set comprises a plurality of groups of samples, and each group of samples comprises a group of equivalent attenuation thicknesses, exposure tube voltages and reference voltages;

it will be appreciated that one skilled in the art may perform exposure simulation in a DR system to acquire a sample set (i.e., a data sampling process). For example, data can be sampled by illuminating different thicknesses of a PMMA phantom using different exposure conditions to obtain multiple exposure images. At this time, each exposure image corresponds to a group of samples, and the group of samples includes parameters (tube voltage, tube current, reference voltage, PMMA phantom thickness and exposure time) of the exposure image and an average gray scale of a region corresponding to the PMMA phantom position in the exposure image. In addition, the DR system structure used in the data sampling process needs to be consistent with the DR system structure used in practical application (for example, all grids are included or none are included), so that accurate reference voltage can be acquired when a voltage model obtained by training the sample set is subsequently used, and finally, an exposure image with stable and reliable quality is obtained.

It should also be noted that the PMMA phantom can be placed anywhere on the detector, but it is necessary to cover a certain field (L field, R field, or C field) of the ionization chamber completely to ensure accurate data acquisition. And when the PMMA die body is completely covered with the C field and then data sampling is carried out, the average gray scale in the sample is the average gray scale of the area corresponding to the C field in the exposure image. At the moment, in the actual operation process, if the gray scale of the middle area of the final image needs to meet the requirement, the trained voltage model can be directly used to obtain accurate reference voltage; if the gray scale of the left or right region of the final image needs to meet the requirement, the reference voltage corresponding to the C field is converted into the reference voltage to be used according to the known functional relationship between the regions in the DR system, and the specific functional relationship is not described herein again. Similarly, when the PMMA phantom is completely covered with the L field (or R field) and then data sampling is performed, the average gray level in the sample is the average gray level of the region corresponding to the L field (or R field) in the exposure image. The conversion of the reference voltages is similar and will not be described herein.

Referring to fig. 3, the figure is a schematic flow chart of a sample set obtaining method according to an embodiment of the present invention.

Step S301: sending a preset tube voltage and a preset tube current to the high-voltage generator, so that the high-voltage generator emits X-rays according to the preset tube voltage and the preset tube current, exposure is started, and the X-rays reach the detector through an attenuator with a preset thickness;

it should be noted that the preset tube voltage and the preset tube current can be set according to experience by presetting the attenuation of the thickness.

The sampling process is the same for different DR systems. Since the application range of the tube voltage in the DR system is generally 40kV-150kV, a person skilled in the art can select several tube voltage sampling points of 50kV, 55kV, 65kV, 75kV, 85kV, 95kV, 110kV and 130kV for data sampling. Meanwhile, based on the known equivalent attenuation thickness range of different parts in the human body, PMMA motifs with the thickness of 5cm, 10cm, 15cm and 20cm can be selected as the irradiated attenuation objects in the data sampling process. In order to improve the sampling efficiency, the actual sampling quantity can meet the precision requirement of subsequent model training.

Step S302: detecting a feedback voltage generated by the ionization chamber to obtain a sample voltage;

step S303: when the sample voltage is greater than or equal to a preset reference voltage, stopping exposure, and recording the exposure duration time, the feedback voltage generated by the ionization chamber, and the tube voltage and the tube current at the high-voltage generator to respectively obtain the exposure time, the reference voltage, the tube voltage and the tube current in a group of samples, wherein the thickness of the attenuator is the equivalent attenuation thickness in the group of samples;

in one example, the feedback voltage may be an amplified feedback voltage. The tube voltage and the tube current at the high voltage generator may be an average value of a tube voltage actually detected and an average value of a tube current actually detected in an exposure process, respectively.

Step S304: acquiring an image generated by the detector, and detecting the average gray level in a sample region in the image to obtain the average gray level in the group of samples, wherein the sample region corresponds to the region covered by the reference sample;

step S305: after changing the preset tube voltage, the preset tube current and the preset reference voltage, repeatedly executing the steps S301 to S304 to obtain a plurality of groups of samples;

step S306: after changing the thickness of the attenuator, repeating steps S301 to S305 to obtain the sample set.

In the specific sampling process, a PMMA die body with the thickness of 5cm can be placed between a high-voltage generator and a detector, exposure conditions corresponding to tube voltages of 50kV, 55kV, 65kV, 75kV, 85kV, 95kV, 110kV and 130kV are applied one by one to start exposure, and automatic exposure control is carried out according to empirically set reference voltages. And then, after PMMA die bodies with the thicknesses of 10cm, 15cm and 20cm are placed between a high-voltage generator and a detector one by one, the exposure and automatic exposure control processes are repeated again to finish data sampling, and a sample set is obtained.

It should also be noted that the initial model may be implemented according to a classical least squares based polynomial fitting method. However, the accuracy of the voltage model obtained by the method depends on the setting of the polynomial order, and the anti-interference performance is general. In addition, those skilled in the art can construct a voltage model by a Support Vector Machine (SVM) method. The SVM is established on the basis of a VC (Vapnik-Chervonenkis Dimension) theory and a structure risk minimization principle of a statistical learning theory, has the advantages of strong learning capability on small samples (namely when the number of the samples is limited), can be well applied to a method for identifying, classifying and fitting small sample data, and has good popularization capability. However, the solution process of the SVM is a quadratic optimization problem, and the calculation process is relatively complex. One skilled in the art may also use a Least Squares Support Vector Machine (LS-SVM) method to construct the voltage model. The LS-SVM solving process is a linear KKT (Karush-Kuhn-Tucker) system solving process, so that the calculation efficiency is high. Therefore, in order to improve the speed and accuracy of the model building, i.e., the training process, in this embodiment, a LS-SVM-based training method is used to build the voltage model, and the initial model is a data model built based on a least squares support vector machine. At the moment, the training of the model can be completed only by collecting a small number of samples in the data sampling process, the efficiency of model training is improved, and the method has high accuracy and expandability.

In particular, for a given sample data set

Wherein x_kFor corresponding input data in a set of samples during sample training, y_kFor corresponding output data, x, in the set of samples during sample training_k∈Rⁿ，y_k∈ R. in SVM, the relationship between data is expressed as shown in equation 1:

equation 1:

wherein the non-linear mapping

Rⁿ→R^mMapping input data to a high-dimensional feature space (also infinite dimension), w ∈ R^mOffset by a constant b ∈ R.

At this time, for the high efficiency of the calculation process, in the LS-SVM, the fitting problem of the data is described as solving the following objective function, i.e., equation 2:

equation 2:

is subject to:

wherein e is_kGamma is a penalty factor for the deviation variable.

And introducing a Lambertian function to solve to obtain a formula 3:

equation 3:

wherein, α_k∈ R is the Lagrangian multiplier.

Then, equation 4 is obtained according to the necessary condition that the extreme value exists:

equation 4:

at this time, erasing w and e can obtain a KKT system of (N +1) × (N +1), as shown in equation 5:

equation 5:

wherein A, Y, α and Ω are kernel functions, I is an identity matrix, and a ═ 1]^T，Y＝[y₁,...,y_N]^T，α＝[α₁,...,α_N]^T，

To satisfy the merser theorem, radial basis kernel functions are used, i.e.

Finally, equation 6 and equation 7 are obtained:

equation 6:

equation 7:

then, the function-fitting model for the LS-SVM of equation 1 gives the following equation, equation 8:

equation 8:

wherein, α_kAnd b has been prepared fromEquation 6 and equation 7.

Secondly, training the initial model by using the sample set;

here, the parameters used in the sample training are γ 10000 and σ 6000. The above parameters can be set by those skilled in the art according to practical situations, and are not listed here.

It will be appreciated that the equivalent attenuation thickness of the object to be illuminated may be empirically derived by those skilled in the art, and may be set, for example, according to the thickness range of the equivalent phantom given in table 1.

And finally, obtaining the voltage model according to the trained initial model. That is, a voltage model for acquiring a reference voltage required to reach a target gray is obtained according to equation 8 (equation 9):

equation 9:

wherein, y^vIs a reference voltage required in actual operation, x^v＝[kv,t]Input data used for calculating reference voltage in actual operation are provided, kv is exposure tube voltage in actual operation, and t is equivalent attenuation thickness of an illuminated object in actual operation;

for the kth group of samples in the sample set, kv_kIs the exposure tube voltage in the kth set of samples, t_kIs the equivalent attenuation thickness in the kth set of samples, with the corresponding output as

refV_kFor the reference voltage in the kth set of samples,

the reference voltage required for reaching the target gray level in the kth group of samples;

is a support value of the kth group of samples, b^vThe offset constants can be obtained through sample training; the offset is gray level offset and can be obtained by calculating the average value of the gray levels of the same area in the output image of the DR system and the image obtained in the sampling process when no X-ray is radiated; avl_targetThe target gray value of the interested area in the final image in the actual operation is obtained; avl_kIs the average gray value of the region corresponding to the region of interest in the final image in the actual operation in the kth group of sample images.

In practical application, with the increase of the thickness of the irradiated object, even if the exposure image obtained by the automatic exposure control method can meet the requirement of the expected target gray value, the signal-to-noise ratio and the contrast of the exposure image are reduced. This requires different target gray-scale values to be set for different thicknesses of the target to be illuminated to improve the signal-to-noise ratio and contrast of the final exposure image. For this case, the skilled person only needs to adjust the reference voltage obtained according to equation 9 according to the required target gray-level value. During specific training, the input in the formula 9 is kept unchanged, and the corresponding output becomes the response relation between the gray level in the sample and the reference voltage, which is specifically expressed as

Then, the input data for calculating the reference voltage in the actual operation is input into formula 9, and the obtained output is multiplied by the target gray scale to be achieved, so that the reference voltage required for achieving the target gray scale can be calculated.

In addition, since the magnitude of the tube voltage affects the penetration of X-rays, the equivalent attenuation thickness of the irradiated object is related to the tube voltage used in the exposure. However, the accuracy is not high as a person skilled in the art generally selects an equivalent attenuation thickness from the range of equivalent attenuation thicknesses shown in table 1 empirically. Therefore, in order to further improve the accuracy of automatic exposure control and the stability of the quality of the final exposure image, the actual equivalent attenuation thickness of the irradiated object can be accurately obtained according to the actual exposure condition in the exposure process.

In a preferred embodiment of this embodiment, to further improve the accuracy of automatic exposure control, a person skilled in the art may also use a thickness model trained in advance to accurately obtain the equivalent attenuation thickness of the object to be illuminated based on the actual exposure condition. The obtaining the equivalent attenuation thickness of the illuminated object comprises:

firstly, obtaining a thickness model;

it will be appreciated that the rate of change of the feedback voltage generated by the ionization chamber varies with different tube currents. I.e. the exposure time is related to the tube current. Under the condition of a certain reference voltage, the equivalent attenuation thickness of the irradiated object also has an influence on the exposure time. Therefore, the thickness model needs to take the reference voltage, the exposure time and the tube current as the basis to comprehensively consider the influence of the tube voltage on the equivalent attenuation thickness of the irradiated object.

Similarly, those skilled in the art can obtain a relation model between the tube voltage, the tube current, the exposure time, the reference voltage and the equivalent attenuation thickness of the illuminated object, i.e. a thickness model, through the steps of data sampling, data fitting, regression and the like.

Other factors (e.g., X-ray energy, etc.) may also affect the exposure process. Therefore, on the basis of the tube voltage, the tube current, the exposure time and the reference voltage, the influence of other factors on the equivalent attenuation thickness of the illuminated object can be comprehensively considered, so that the accuracy of setting the final reference voltage is further improved, and the stability of the quality of the exposed image is improved. At this time, the influence of the above factors (such as X-ray energy) on the effective attenuation thickness needs to be considered in the acquired thickness model.

The following illustrates a specific process of thickness model acquisition. It is understood that the skilled person can also specifically select the method for obtaining the thickness model according to the actual situation.

Firstly, obtaining a sample set and constructing an initial model, wherein the sample set comprises a plurality of groups of samples, and each group of samples comprises a group of equivalent attenuation thickness, exposure tube voltage, exposure tube current, exposure duration and reference voltage;

it will be appreciated that one skilled in the art may perform exposure simulation in a DR system to acquire a sample set (i.e., a data sampling process).

In some possible embodiments of this embodiment, the method for obtaining a sample set described in the above example may be adopted, and the specific flow is shown in fig. 3, which is not described herein again.

Similarly, in order to improve the speed and accuracy of the model building, i.e., the training process, in this embodiment, a LS-SVM-based training method (i.e., the above formula 1 to formula 8) is used to build the thickness model, and the initial model is a data model built based on a least squares support vector machine.

Secondly, training the initial model by utilizing the sample set;

here, in this case, the parameters used in the sample training are γ 10000 and σ 10. The above parameters can be set by those skilled in the art according to practical situations, and are not listed here.

And finally, obtaining the thickness model according to the trained initial model. That is, a thickness model (formula 10) for obtaining an equivalent attenuation thickness of the object to be illuminated is obtained according to formula 8:

equation 10:

wherein, y^tFor an equivalent attenuation thickness of the object to be illuminated in practice,

inputting data used for calculating attenuation thickness in actual operation, wherein kv is exposure tube voltage in actual operation, refV is sampling voltage in actual operation, mA is exposure tube current in actual operation, and s is first time in actual operation;

for the kth group of samples in the sample data set, kv_kIs the tube voltage in the kth set of samples, refV_kIs the reference voltage, mA, in the kth set of samples_kIs the tube current in the kth set of samples, s_kIs the exposure duration in the kth set of samples, with the corresponding output as

t_kIs the thickness of the PMMA motif in the kth group of samples;

is a support value of the kth group of samples, b^tThe offset constants can be obtained by sample training.

It should be noted that since the X-ray is attenuated in the exponential form of e, it is used as an input to the thickness model

The distribution range of the data result obtained by calculation is more uniform and stable. It will be appreciated that one skilled in the art may also use other forms of sample data as input to train the initial model, and accordingly, x^tShould be in accordance with

The form of the same.

Secondly, when the first comparison voltage is larger than or equal to the sampling voltage, recording the exposure duration time to obtain first time;

Similarly, when the first comparison voltage is greater than or equal to the sampling voltage, the first comparison voltage can be regarded as one exposure with the sampling voltage as the reference voltage. At this time, the actual conditions in the exposure process of this time, that is, the tube voltage and the tube current used for the exposure and the exposure time (the time used when the first comparison voltage is greater than or equal to the sampling voltage) can be acquired. Then, the actual conditions (tube voltage, tube current and exposure time) in the exposure process are input into the thickness model, and the equivalent attenuation thickness of the irradiated object in the exposure can be obtained.

Due to various interference factors, there is a difference between the actual tube voltage and tube current at the high voltage generator and the given initial tube voltage and initial tube current during the exposure process. Therefore, the voltage and the current of the detection tube are input into the thickness model to obtain the equivalent attenuation thickness of the illuminated object, the accuracy of the equivalent attenuation thickness can be improved, and the stability of the image quality is further ensured.

Step S2032: and inputting the equivalent attenuation thickness and the voltage of the exposure tube into the voltage model to obtain the reference voltage, wherein the voltage of the exposure tube is equal to the initial tube voltage or the voltage of the detection tube, and the voltage of the detection tube is detected when the first comparison voltage is greater than or equal to the sampling voltage.

The voltage of the detection tube is input into the voltage model to obtain the reference voltage, so that the accuracy of the reference voltage can be improved, and the stability of the image quality is further ensured.

Step S204: continuously detecting the feedback voltage generated by the ionization chamber to obtain a second comparison voltage;

and according to the selection of the detector field in the current exposure process, obtaining a second comparison voltage through the feedback voltage generated by the ionization chamber obtained in the corresponding channel. The second comparison voltage may also be an amplified feedback voltage.

Step S205: and when the second comparison voltage is greater than or equal to the reference voltage, switching off the high-voltage generator and stopping exposure.

It is to be understood that when the second comparison voltage is greater than or equal to the reference voltage, i.e. indicating that the X-ray radiation reaches the desired dose, the gray level of the final exposed image reaches the target gray level, the exposure may be stopped. Specifically, the exposure may be stopped by cutting off the tube voltage and the tube current using a cut-off circuit.

To better explain the technical solution provided by the embodiment of the present invention, fig. 4 is a flowchart of an example scenario of an automatic exposure control method provided by the embodiment of the present invention, and the flowchart includes:

it should be noted that, in order to avoid the logic oscillation, the reference voltage needs to be set only once. At this time, a reference voltage adjustment flag may be set and set to 0 at the start of exposure.

Step S401: the reference voltage and the exposure conditions (tube voltage and tube current) are empirically set, the reference voltage adjustment flag is set to 0, and the high voltage generator is controlled to start exposure according to the exposure conditions.

Step S402: the feedback signal generated by the ionization chamber is read in a fixed period, and the feedback signal is amplified by an amplifier to obtain a comparison voltage.

Step S403: judging whether the comparison voltage is greater than a reference voltage or not; if yes, stopping exposure; if not, go to step S404;

step S404: judging whether the comparison voltage is greater than or equal to the sampling voltage and whether a reference voltage adjustment flag is 0; if yes, go to step S405, otherwise go to step S402.

Step S405: the reference voltage is updated according to the sampling voltage, the attenuation of the illuminated object, the exposure condition and other factors, and after the reference voltage adjustment flag is set to 1, the step S402 is repeatedly executed.

In the automatic exposure control method provided in this embodiment, an initial tube voltage and an initial tube current are set empirically, and a high voltage generator is controlled to emit X-rays to start exposure according to the initial tube voltage and the initial tube current. Thereafter, a feedback voltage generated by the ionization chamber is detected. When the feedback voltage is greater than or equal to the sampling voltage, the reference voltage is acquired according to parameters (such as attenuation of the object to be irradiated, exposure conditions and the like) obtained and acquired in advance. And continuously detecting the feedback voltage generated by the ionization chamber, and judging the magnitude relation between the feedback voltage and the reference voltage. And when the feedback voltage is greater than the reference voltage, cutting off the power supply of the high-voltage generator and stopping exposure. Therefore, the reference voltage is set according to the actual exposure process, so that the setting of the reference voltage is more reasonable, the accuracy of automatic exposure control can be ensured, an exposure image with ideal gray scale is obtained, the stability and reliability of the quality of the exposure image are ensured, and the condition that the reference voltage is set by experience in the prior art, namely underexposure or overexposure is avoided.

Based on the automatic exposure control method provided by the embodiment, the embodiment of the invention also provides an automatic exposure control device.

The embodiment of the device is as follows:

referring to fig. 5, it is a schematic structural diagram of an embodiment of an automatic exposure control apparatus provided in the present invention.

The automatic exposure control device provided by the embodiment comprises: the high-voltage control module 100, the voltage detection module 200, the first comparison module 300, the voltage acquisition module 400 and the second comparison module 500;

the high voltage control module 100 is configured to send an initial tube voltage and an initial tube current to the high voltage generator, so that the high voltage generator emits X-rays according to the initial tube voltage and the initial tube current to start exposure; when the comparison result of the second comparison module 500 is that the second comparison voltage is greater than or equal to the reference voltage, the high voltage generator is switched off, and the exposure is stopped;

the voltage detection module 200 is configured to detect a feedback voltage generated by the ionization chamber to obtain a first comparison voltage; when the comparison result of the first comparison module 300 is that the first comparison voltage is greater than or equal to the sampling voltage, continuously detecting the feedback voltage generated by the ionization chamber to obtain a second comparison voltage;

the first comparing module 300 is configured to compare a magnitude relationship between the first comparison voltage and the sampling voltage;

the voltage obtaining module 400 is configured to obtain the reference voltage and send the reference voltage to the high voltage control module when the comparison result of the first comparing module 300 is that the first comparison voltage is greater than or equal to the sampling voltage, where the reference voltage is greater than the sampling voltage;

it is understood that the gray scale of the exposure image is related to the intensity of the X-ray (i.e., the tube voltage) and the attenuation of the X-ray intensity by the object to be irradiated (i.e., the equivalent attenuation thickness of the object to be irradiated) and the exposure time. In the AEC control system, the exposure time is controlled by setting a reference voltage. Therefore, in order to ensure the stability and reliability of the quality of the exposure image, the accurate reference voltage needs to be obtained based on the tube voltage used in the actual exposure and the equivalent attenuation thickness of the object to be irradiated.

The second comparing module 500 is configured to compare a magnitude relationship between the second comparison voltage and the reference voltage;

in one example, the voltage acquisition module 400 includes: a voltage model acquisition sub-module, a thickness acquisition sub-module, and a voltage calculation sub-module (all not shown in the figure);

the voltage model obtaining submodule is used for obtaining a voltage model;

in some possible implementations of this embodiment, the voltage model obtaining sub-module includes: an initial sub-module, a training sub-module, and a generation sub-module (all not shown in the figure);

it should be noted that the initial model may be a data model constructed based on a least squares support vector machine.

As an example, the initial sub-module includes: the control sub-module, the detection sub-module, the comparison sub-module, the processing sub-module, the first cycle control sub-module and the second cycle control sub-module (all not shown in the figure);

the control submodule is used for sending a preset tube voltage and a preset tube current to the high-voltage generator so that the high-voltage generator emits X rays according to the preset tube current and the preset tube current to start exposure, and the X rays reach the detector through an attenuation object with a preset thickness; when the comparison result of the comparison submodule is that the sample voltage is greater than or equal to a preset reference voltage, stopping exposure, recording the exposure duration time, the feedback voltage generated by the ionization chamber, and the tube voltage and the tube current at the high-voltage generator, and respectively obtaining the exposure time, the reference voltage, the tube voltage and the tube current in a group of samples, wherein the thickness of the attenuator is the equivalent attenuation thickness in the group of samples;

the detection submodule is used for detecting the feedback voltage generated by the ionization chamber to obtain a sample voltage;

the comparison submodule is used for comparing the magnitude relation between the sample voltage and a preset reference voltage;

the processing sub-module is used for acquiring the image generated by the detector and detecting the average gray level in a sample area in the image to obtain the average gray level in the group of samples, wherein the sample area corresponds to the area covered by the reference sample;

the first circulation control submodule is used for triggering the control submodule, the detection submodule, the comparison submodule and the processing submodule again after changing the preset tube voltage, the preset tube current and the preset reference voltage to obtain a plurality of groups of samples;

and the second circulation control submodule is used for triggering and executing the control submodule, the detection submodule, the comparison submodule, the processing submodule and the first circulation control submodule again after the thickness of the attenuating object is changed, so that the sample set is obtained.

In order to further improve the accuracy of automatic exposure control, a person skilled in the art can also use a thickness model trained in advance to accurately acquire the equivalent attenuation thickness of the illuminated object based on the actual exposure condition.

In some possible implementations of this embodiment, the thickness obtaining sub-module includes: a thickness model acquisition sub-module, a time recording sub-module, and a thickness calculation sub-module (all not shown in the figure);

it will be appreciated that the rate of change of the feedback voltage generated by the ionization chamber varies with different tube currents. I.e. the exposure time is related to the tube current. Under the condition of a certain reference voltage, the equivalent attenuation thickness of the irradiated object can also influence the exposure time. Therefore, the thickness model needs to take the reference voltage, the exposure time and the tube current as the basis to comprehensively consider the influence of the tube voltage on the equivalent attenuation thickness of the irradiated object.

In one example, the thickness model acquisition submodule includes: an initial sub-module, a training sub-module, and a generation sub-module (all not shown in the figure);

As an example, the initial sub-module may include: the control sub-module, the detection sub-module, the comparison sub-module, the processing sub-module, the first cycle control sub-module and the second cycle control sub-module (all not shown in the figure);

In the automatic exposure control device provided in this embodiment, after the initial tube voltage and the initial tube current are set empirically, the high-voltage control module controls the high-voltage generator to emit X-rays to start exposure according to the initial tube voltage and the initial tube current. Thereafter, a voltage detection module detects a feedback voltage generated by the ionization chamber. When the first comparison module judges that the feedback voltage is greater than or equal to the sampling voltage, the voltage acquisition module acquires the reference voltage according to the parameters (such as attenuation of the illuminated object, exposure conditions and the like) obtained and acquired in advance. Then, the voltage detection module continues to detect the feedback voltage generated by the ionization chamber, and the second comparison module judges the magnitude relation between the feedback voltage and the reference voltage. When the second comparison module judges that the feedback voltage is greater than the reference voltage, the high-voltage control module cuts off the power supply of the high-voltage generator and stops exposure. Therefore, the reference voltage is set according to the actual exposure process, so that the setting of the reference voltage is more reasonable, the accuracy of automatic exposure control can be ensured, an exposure image with ideal gray scale is obtained, the stability and reliability of the quality of the exposure image are ensured, and the condition that the reference voltage is set by experience in the prior art, namely underexposure or overexposure is avoided.

Based on the automatic exposure control method and device provided by the embodiment, the embodiment of the invention also provides an automatic exposure system.

The embodiment of the system is as follows:

referring to fig. 6, it is a schematic structural diagram of an embodiment of an automatic exposure system provided in the present invention.

The automatic exposure system provided by the embodiment is applied to an X-ray machine; the system, comprising: a high voltage generator 61, a detector 62, an ionization chamber 63, a comparator 64, and a controller 65;

the controller 65 for sending an initial tube voltage and an initial tube current to the high voltage generator 61; when the first comparison result is that the feedback voltage is greater than or equal to the sampling voltage, obtaining a reference voltage and sending the reference voltage to the comparator 64, wherein the reference voltage is greater than the sampling voltage; when the second comparison result is that the feedback voltage is greater than or equal to the reference voltage, the X-ray emitted by the high voltage generator 61 is cut off, and the exposure is stopped;

In a preferred embodiment of this embodiment, to further improve the accuracy of automatic exposure control, a person skilled in the art may also use a thickness model trained in advance to accurately obtain the equivalent attenuation thickness of the object to be illuminated based on the actual exposure condition.

The high voltage generator 61 is configured to emit X-rays to the detector 62 according to the initial tube voltage and the initial tube current, and start exposure;

the detector 62 is used for sensing the arriving X-ray and imaging according to the arriving X-ray;

the ionization chamber 63 is configured to generate the feedback voltage according to the X-ray dose reaching the detector 62, and send the feedback voltage to the comparator 64;

the comparator 64 is configured to compare a magnitude relationship between the feedback voltage and the sampling voltage to obtain the first comparison result, and send the first comparison result to the controller 65; comparing the magnitude relationship between the feedback voltage and the reference voltage to obtain the second comparison result, and sending the second comparison result to the controller 65;

in the automatic exposure system provided by this embodiment, the initial tube voltage and the initial tube current are set according to experience, and then the initial tube voltage and the initial tube current are sent to the high voltage generator through the controller. And enabling the high-voltage generator to emit X-rays to start exposure according to the initial tube voltage and the initial tube current, and enabling the detector to image according to the arriving X-rays. The ionization chamber then generates a feedback voltage according to the X-ray dose reaching the detector. When the comparator determines that the feedback voltage is greater than or equal to the sampling voltage, the controller is triggered. The controller obtains the reference voltage according to the parameters (such as the thickness of the irradiated object, the tube voltage and the tube current at the high voltage generator and the like) obtained in advance. Then, the comparator determines the magnitude relationship between the feedback voltage and the reference voltage. And when the feedback voltage is greater than the reference voltage, triggering the controller to cut off the power supply of the high-voltage generator and stop exposure. Therefore, the reference voltage is set according to the actual exposure process, so that the setting of the reference voltage is more reasonable, the accuracy of the exposure process can be ensured, an exposure image with ideal gray scale is obtained, the stability and reliability of the quality of the exposure image are ensured, and the condition that the reference voltage is set by experience in the prior art, namely underexposure or overexposure is avoided.

It should be noted that, in the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. The system or the device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make numerous possible variations and modifications to the present teachings, or modify equivalent embodiments to equivalent variations, without departing from the scope of the present teachings, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.

Claims

1. An automatic exposure control method is characterized in that the method is applied to an X-ray machine, and the X-ray machine comprises the following steps: a high voltage generator, a detector and an ionization chamber; the X-ray emitted by the high-voltage generator reaches the detector through a target to be irradiated, the detector images according to the reached X-ray, and the ionization chamber generates a feedback voltage according to the X-ray dosage reaching the detector; the method comprises the following steps:

2. The automatic exposure control method according to claim 1, wherein the obtaining a reference voltage includes:

3. The automatic exposure control method according to claim 2, wherein the obtaining a voltage model includes:

training the initial model using the sample set;

and obtaining the voltage model according to the trained initial model.

4. The automatic exposure control method according to claim 2, wherein the obtaining an equivalent attenuation thickness of the object to be illuminated includes:

obtaining a thickness model;

5. The automatic exposure control method according to claim 4, wherein the obtaining of the thickness model includes:

training the initial model using the sample set;

and obtaining the thickness model according to the trained initial model.

6. An automatic exposure control device, characterized in that, be applied to X line machine, X line machine includes: a high voltage generator, a detector and an ionization chamber; the X-ray emitted by the high-voltage generator reaches the detector through a target to be irradiated, the detector images according to the reached X-ray, and the ionization chamber generates a feedback voltage according to the X-ray dosage reaching the detector; the apparatus, comprising: the device comprises a high-voltage control module, a voltage detection module, a first comparison module, a voltage acquisition module and a second comparison module;

7. The automatic exposure control device according to claim 6, wherein the voltage acquisition module includes: the voltage model acquisition submodule, the thickness acquisition submodule and the voltage calculation submodule are connected;

the voltage model obtaining submodule is used for obtaining a voltage model;

8. The automatic exposure control apparatus according to claim 7, wherein the voltage model acquisition sub-module includes: the system comprises an initial submodule, a training submodule and a generating submodule;

9. The automatic exposure control apparatus according to claim 8, wherein the thickness acquisition submodule includes: the thickness model acquisition sub-module, the time recording sub-module and the thickness calculation sub-module are connected with the thickness calculation sub-module;

10. The automatic exposure control apparatus according to claim 9, wherein the thickness model acquisition submodule includes: the system comprises an initial submodule, a training submodule and a generating submodule;

11. An automatic exposure system is characterized in that the automatic exposure system is applied to an X-ray machine; the system, comprising: the device comprises a high-voltage generator, a detector, an ionization chamber, a comparator and a controller;