CN109521455B - X-ray image detector for realizing automatic gain switching and method thereof - Google Patents
X-ray image detector for realizing automatic gain switching and method thereof Download PDFInfo
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- G01T1/02—Dosimeters
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Abstract
The invention discloses an X-ray image detector for realizing automatic gain switching and a method thereof. The image detector comprises a detection module, a selection switch, a control module, a plurality of charge amplifiers and a signal processing module. The image detector detects the preset value of the effective X-ray dose of each charge amplifier in the over-low and saturated state of the image gray value to obtain the minimum and maximum effective X-ray dose corresponding to each charge gain stage, so that when the image detector is used for shooting a film normally, the selection switch is controlled to switch to the charge gain stage corresponding to the effective X-ray dose according to the measured effective X-ray dose, automatic, accurate and efficient imaging is realized, saturation or over-low brightness of the image is prevented, image quality is improved, the film breakage rate is reduced, and the situation that a patient is repeatedly irradiated is avoided.
Description
Technical Field
The invention relates to an X-ray image detector (hereinafter referred to as X-ray image detector) for realizing automatic gain switching, and also relates to a corresponding automatic gain switching method, belonging to the technical field of radiation imaging.
Background
An X-ray imaging system images by receiving directly projected X-rays with an X-ray detector. If quantum noise is not a concern, it is desirable that the image of the signal received by an ideal detector be a spatially uniform image (typically, simple median or low pass filtering can be used to reduce quantum noise) when an X-ray source is directly impinging on the detector. Since the sensitivity of each pixel element on an actual detector to receive a signal is not uniform, the brightness of the imaged image is not uniform.
When an X-ray image is acquired, due to the difference of the X-ray intensities, the condition that the brightness of the image output under the current integral gain is too low or saturated easily occurs, so that the imaging effect is affected. The existing X-ray detector can set an integral gain gear, but is preset in the use process and cannot be changed in the image acquisition process, so that the brightness of the image can be known after the X-ray output is completed. If the brightness of the acquired image is saturated or too low, the image is re-acquired under the condition of adjusting the X-ray intensity or integrating gain, thereby causing the patient to be repeatedly irradiated.
Disclosure of Invention
The primary technical problem to be solved by the present invention is to provide an X-ray image detector for implementing automatic gain switching.
Another technical problem to be solved by the present invention is to provide a method for implementing automatic gain switching of the above-mentioned X-ray image detector.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
according to a first aspect of an embodiment of the present invention, there is provided an X-ray image detector for implementing automatic gain switching, including a detection module, a selection switch, a control module, a plurality of charge amplifiers and a signal processing module; each charge amplifier is respectively connected with the corresponding signal processing module, each signal processing module is connected with the control module, the control module is respectively connected with the detection module and the selection switch, and the selection switch is respectively connected with each charge amplifier;
the detection module is used for measuring the X-ray intensity corresponding to the minimum value and the maximum value of the image gray level of each charge gain stage of each charge amplifier respectively, and calculating and storing the minimum value and the maximum value of the effective X-ray dose corresponding to each charge gain stage through the control module;
and during normal shooting, the control module controls the selection switch to be switched to a charge gain gear corresponding to the effective X-ray dose according to the calculated effective X-ray dose.
Preferably, under each charge gain stage of each charge amplifier, the obtained image gray values corresponding to the X rays with different energy levels are transmitted to the control module through the charge amplifier and the signal processing module, so as to obtain the minimum value and the maximum value of the image gray corresponding to each charge gain stage.
The detection module is preferably realized by a semiconductor probe and is used for measuring the X-ray intensity and acquiring the voltage value and the effective level output time of the X-ray intensity, wherein the product of the voltage value and the effective level output time of the X-ray intensity is the effective dose of the X-ray.
Preferably, each charge amplifier comprises a low-noise differential input single-ended output operational amplifier, a reset switch, a plurality of feedback capacitors with different capacitance values and a plurality of control switches; the inverting input end of the low-noise differential input single-ended output operational amplifier is respectively connected with the reset switch and one end of each control switch, the non-inverting input end of the low-noise differential input single-ended output operational amplifier is connected with the reference voltage, the other end of the reset switch is connected with the output end of the low-noise differential input single-ended output operational amplifier, the other end of each control switch is connected with one end of the corresponding feedback capacitor, and the other end of the feedback capacitor is respectively connected with the output end of the low-noise differential input single-ended output operational amplifier.
Preferably, one end of each control switch is further connected to the other end of the selection switch, and the control switch is controlled by the selection switch, so that the charge amplifier is switched to a charge gain switch corresponding to a certain feedback capacitor.
Preferably, each signal processing module obtains an image gray value corresponding to the X-ray collected by the photoelectric conversion module according to the following formula;
X＝K*Vout
wherein K represents a proportionality coefficient, vout represents a voltage signal processed by the signal processing module, and K is a positive number.
Wherein preferably, the control module obtains the effective dose sizes of the X-rays with different energy levels according to the following formula;
E＝V*s
wherein V represents a voltage value of the X-ray intensity, and s represents the X-ray intensity effective level output time.
According to a second aspect of the embodiment of the present invention, there is provided a method for implementing automatic gain switching for an X-ray image detector, including the steps of:
measuring the X-ray intensity corresponding to the minimum and maximum values of the image gray level of each charge gain stage of each charge amplifier, and calculating and storing the minimum and maximum values of the effective X-ray dose corresponding to each charge gain stage;
during normal shooting, according to the calculated effective X-ray dose, the selection switch is controlled to be switched to a charge gain gear corresponding to the effective X-ray dose.
Preferably, the method calculates and stores the minimum value and the maximum value of the effective X-ray dose corresponding to each charge gain stage, and comprises the following substeps:
transmitting the obtained image gray values corresponding to the X rays with different energy levels to corresponding control modules under each charge gain stage of each charge amplifier to obtain the minimum value and the maximum value of the image gray corresponding to each charge gain stage;
and respectively acquiring voltage values and effective level output time of the X-ray intensity corresponding to the minimum and maximum image gray levels of each charge gain stage, and transmitting the acquired voltage values and effective level output time of the X-ray intensity to the control module to respectively acquire the effective X-ray doses corresponding to the minimum and maximum image gray levels of each charge gain stage.
Preferably, the method switches to a charge gain stage corresponding to the effective X-ray dose according to the calculated effective X-ray dose, and comprises the following substeps:
transmitting X-rays, measuring, transmitting the obtained voltage value of the X-ray intensity and the output time of the effective level to a control module, and calculating the effective dose of the X-rays;
judging whether the effective dose of the X-ray is between the minimum value and the minimum value of the corresponding effective dose of the X-ray under the current charge gain range according to the effective dose of the X-ray; if not, the selection switch is controlled to be switched to a charge gain gear corresponding to the effective dose of the X-ray.
The X-ray image detector provided by the invention can obtain the corresponding X-ray effective dose range in the over-low and saturated states by carrying out the pre-value detection on the X-ray effective dose of the image gray value in the over-low and saturated states under each charge gain stage of each charge amplifier, so that the X-ray image detector is convenient for automatically switching to the more proper charge gain stage according to the measured X-ray effective dose in the normal shooting process, realizes automatic, accurate and efficient imaging, prevents the image from being saturated or has over-low brightness, improves the image quality, reduces the film breakage rate, and further avoids the situation that a patient is repeatedly radiated.
Drawings
FIG. 1 is a schematic diagram of an X-ray image detector according to the present invention;
FIG. 2 is a schematic circuit diagram of each charge amplifier in the X-ray image detector according to the present invention;
fig. 3 is a flowchart of a method for implementing automatic gain switching in an X-ray image detector according to the present invention.
Detailed Description
The technical contents of the present invention will be described in further detail with reference to the accompanying drawings and specific examples.
As shown in fig. 1, the X-ray image detector provided by the present invention includes a scintillation crystal layer L1, a photoelectric conversion module L2, a substrate L3, a detection module T, a first selection switch IGS [0], a second selection switch IGS [1], a plurality of charge amplifiers 10 and signal processing modules 20 corresponding to the photoelectric conversion module L2, and a control module 30, which are sequentially connected; the photoelectric conversion module L2 is correspondingly connected to an input end of each charge amplifier 10, an output end of each charge amplifier 10 is connected to an input end of a corresponding signal processing module 20, an output end of each signal processing module 20 is respectively connected to an input end of a control module 30, an input end of the control module 30 is also connected to an output end of a detection module T, an output end of the control module 30 is connected to one end of a first selection switch IGS [0] and one end of a second selection switch IGS [1], and the other ends of the first selection switch IGS [0] and the second selection switch IGS [1] are respectively connected to an input end of each charge amplifier 10.
Specifically, the scintillation crystal layer L1 is configured to convert X-rays emitted by the X-ray tube into visible light when the X-rays pass through the object to be projected onto the X-ray image detector. The scintillator crystal layer L1 is preferably a cesium iodide (CsI) material, and other materials such as GOS may be used.
The photoelectric conversion module L2 is configured to convert energy of received visible light into an equal proportion of charge amount, and transmit the charge amount to the corresponding charge amplifier 10 to be converted into a voltage signal. The photoelectric conversion module L2 may be an X-ray image sensor formed by photoelectric conversion units having the same number as that of pixels of an image, and a pixel array formed by m×n pixels having the same size is provided on a panel of the X-ray image sensor. The pixel array consists of m rows and n columns of pixels, wherein m and n are natural numbers greater than or equal to 1. Each pixel corresponds to one photoelectric conversion unit, and the photoelectric conversion unit L20 may employ a photoelectric conversion chip (PD chip) composed of photodiodes; each photoelectric conversion unit L20 is connected to the input terminal of the corresponding charge amplifier 10 through a gate switch (gate switch SGT shown in fig. 2, which is generally in an active state) for transmitting the corresponding charge amount of each pixel to the corresponding charge amplifier 10 to be converted into a voltage signal, respectively.
The substrate L3 is used for fixing the scintillation crystal layer L1, the photoelectric conversion module L2 and the installation detection module T; the substrate L3 has a smooth surface, and preferably is made of a metal material such as aluminum or copper with uniform material.
The detection module T is configured to measure the X-ray intensity, obtain a voltage value of the X-ray intensity and an output time of an effective level of the X-ray intensity, and transmit the voltage value of the X-ray intensity and the output time of the effective level of the X-ray intensity to the control module 30, so that the control module 30 obtains the effective dose of the X-ray according to the following formula.
E＝V*s (1)
Wherein V represents the voltage value of the X-ray intensity, s represents the X-ray intensity effective level output time
It should be emphasized that the detection module T measures the X-ray intensity, after the amplification of the signal amplifying circuit, the amplified X-ray intensity is converted into a voltage signal by the a/D conversion circuit (analog-to-digital conversion circuit), and the effective level of the X-ray intensity is output by the comparator.
The detection module T can adopt a semiconductor probe which can be arranged at different positions in the substrate to form the X-ray image detector with different specifications. According to the actual requirement, the present X-ray image detector with proper specification can be selected, and the first selection switch IGS [0] and the second selection switch IGS [1] are controlled by the control module 30 to automatically switch the present image detector to a proper charge gain stage according to the measured effective dose of the X-rays.
As shown in fig. 2, each charge amplifier 10 includes a low noise differential input single-ended output operational amplifier a, a reset switch S14, a plurality of feedback capacitances having different capacitance values, and control switches (S11 to St, t is a positive integer) corresponding to the plurality of feedback capacitances; wherein the inverting input end of the low-noise differential input single-ended output operational amplifier A is respectively connected with the reset switch S14 and one end of each control switch, and the non-inverting input end of the low-noise differential input single-ended output operational amplifier A is connected with the reference voltage V ICM The other end of the reset switch S14 is connected with the output end of the low-noise differential input single-ended output operational amplifier A, and one end of each control switch is also respectively connected with a first selection switch IGS 0]And a second selector switch IGS [1]]The other end of each control switch is connected with one end of the corresponding feedback capacitor, the other end of each feedback capacitor is divided intoAnd the output end of the low-noise differential input single-ended output operational amplifier A is connected with the output end of the low-noise differential input single-ended output operational amplifier A.
Since the capacitance value of the feedback capacitor of each charge amplifier 10 is different, and the amount of charge corresponding to the X-ray acquired by the present X-ray image detector at the same energy level is unchanged, that is, the amount of charge corresponding to the X-ray acquired by the photoelectric conversion unit corresponding to each pixel in the image is unchanged, it can be obtained that the amount of charge of the X-ray at the same energy level acquired by each photoelectric conversion unit is equal to the product of the feedback capacitor of the corresponding charge amplifier 10 and the output voltage of the charge amplifier 10, and the feedback capacitor of the charge amplifier 10 is inversely proportional to the output voltage of the charge amplifier 10.
In addition, as shown in fig. 1 and 2, in each charge amplifier 10, the inverting input terminal of the low-noise differential input single-ended output operational amplifier a is connected to the corresponding photoelectric conversion unit L20 through the gate switch SGT, and each charge amplifier 10 is connected to the corresponding signal processing module 20, respectively; each photoelectric conversion unit L20 transmits the converted charge amount corresponding to each pixel to the charge amplifier 10, converts the converted charge amount to a corresponding voltage signal through the charge amplifier 10, transmits the voltage signal to the corresponding signal processing module 20, processes the voltage signal corresponding to each pixel through single-ended-to-differential, amplification, analog-to-digital conversion and the like through the signal processing module 20, and obtains the gray value corresponding to each pixel according to the following formula.
X＝K*Vout (2)
Wherein K represents a proportionality coefficient, vout represents a voltage signal processed by the signal processing module, and K is a positive number. It is not difficult to find that in the case of X-rays of the same energy level, the larger the capacitance value of the feedback capacitance of each charge amplifier 10, the smaller the gradation value of the pixel. When the capacitance value of the feedback capacitance of each charge amplifier 10 is unchanged, the larger the energy level of the X-ray corresponding voltage signal is for each pixel, so that the larger the gray value of the pixel is.
Therefore, the capacitance values of the feedback capacitors of each charge amplifier 10 can be set to different values according to actual requirements, so that each charge amplifier 10 of the present X-ray image detector has a plurality of charge gain stages. For each pixel, each feedback capacitance corresponds to a charge gain stage corresponding to a maximum and minimum of the image gray scale while ensuring image sharpness; when the gray value of each pixel is lower than the minimum gray value, the brightness of the image is too low; when the gray value of each pixel is higher than the maximum gray value, the image is saturated.
Each charge amplifier 10 of the X-ray image detector is placed in the same charge gain stage, the energy level of the X-rays is changed, a plurality of image gray values corresponding to the X-rays with different energy levels can be obtained through the charge amplifier 10 and the signal processing module 20, and images formed by gray values of all pixels corresponding to the X-rays with different energy levels are respectively judged through the control module 30, so that the minimum image gray value when the image brightness is not excessively low and the maximum image gray value when the image saturation is not generated in each charge gain stage are determined, and the energy level range of the X-rays between the maximum image gray value and the minimum image gray value is obtained.
Because the X-ray image detector can respectively measure the intensity of the X-rays with different energy levels, and transmit the obtained voltage values of the X-ray intensity with different energy levels and the output time of the effective level of the X-ray intensity to the control module 30 to obtain the effective doses of the X-rays with different energy levels; therefore, according to the determined X-ray energy level range between the maximum value and the minimum value of the image gray level corresponding to each charge gain stage, an effective dose range of the X-rays between the maximum value and the minimum value of the image gray level of each charge gain stage can be obtained, and the dose range can be directly stored by the control module 30, so that when the present X-ray image detector is used, the present X-ray image detector can be automatically switched to the appropriate charge gain stage according to the measured effective dose of the X-rays, so as to perform more accurate adjustment of image brightness, avoid image saturation or too low brightness to improve image quality, reduce the defect rate, and avoid the requirement of secondary photography of a patient due to the defect.
It should be emphasized that when the present X-ray image detector is used to automatically switch to a suitable charge gain stage according to the measured effective dose of X-rays, it is necessary to ensure that the reset switch S14 is in an off state; when the present X-ray image detector needs to be restored to the initial state (the state in which the charge gain stage does not need to be switched), the reset switch S14 can be controlled to be in the closed state.
The specific structure of the X-ray image detector provided by the present invention is described above, and the method of automatic gain switching adopted by the X-ray image detector is described in detail below.
As shown in fig. 3, the method for automatic gain switching adopted by the present X-ray image detector includes the following steps:
step S1: and measuring the X-ray intensities corresponding to the minimum and maximum values of the image gray scale of each charge gain stage of each charge amplifier, and calculating and storing the minimum and maximum values of the effective X-ray dose corresponding to each charge gain stage.
The method comprises the following substeps:
step S11, under each charge gain stage of each charge amplifier, transmitting the obtained image gray values corresponding to the X rays with different energy levels to a control module to obtain the minimum value and the maximum value of the image gray corresponding to each charge gain stage;
each charge amplifier 10 of the X-ray image detector is placed in the same charge gain stage, the order from the minimum energy level to the maximum energy level of the X-ray tube is adjusted, the tube voltage of the X-ray tube is changed in the same step length, the electric charge amounts corresponding to the X-rays of different tube voltages (different energy levels) under the current charge gain stage are detected and respectively obtained through each photoelectric conversion unit L20, and the image gray values corresponding to the X-rays of different tube voltages under the current charge gain stage are respectively obtained through the corresponding charge amplifier 10 and the signal processing module 20 in sequence.
Since each photoelectric conversion unit L20 corresponds to one pixel unit in the image, the image gray value corresponding to the X-ray of each tube voltage is the gray value of all pixels under the X-ray of the current tube voltage; the control module 30 determines the minimum image gray value and the corresponding X-ray tube voltage when the image brightness is not too low and the maximum image gray value and the corresponding X-ray tube voltage when the image saturation is not present in the current charge gain stage according to the image formed by the image gray values corresponding to the X-rays of each tube voltage.
Since the tube voltage of the X-ray tube is equal to the energy level of the X-ray emitted by the X-ray, the image gray value range corresponding to the image gray value in the current charge gain range when the image gray value is not too low and in the saturation state is the image gray minimum value to the image gray maximum value, and the X-ray energy level range corresponding to the image gray minimum value is the X-ray energy level corresponding to the image gray maximum value. By adopting the method, each charge amplifier 10 is placed in different charge gain stages in turn, and the corresponding image gray value range and X-ray energy level range can be obtained when the charge gain stages of each charge amplifier 10 are not excessively low and in saturation.
Step S12: and respectively acquiring voltage values and effective level output time of the X-ray intensity corresponding to the minimum and maximum values of the image gray levels of each charge gain stage, and transmitting the acquired voltage values and effective level output time of the X-ray intensity to a control module to respectively acquire the effective X-ray doses corresponding to the minimum and maximum values of the image gray levels of each charge gain stage.
The method comprises the steps of pre-detecting the effective X-ray dose of an image gray value under each charge gain stage of each charge amplifier in an excessively low and saturated state, and transmitting the voltage values of the X-ray intensity of the two energy levels and the effective X-ray intensity output time to a control module 30, wherein the voltage values of the X-ray intensity of the two energy levels and the effective X-ray intensity output time are determined in the step S11, and the effective X-ray dose of the two energy levels is calculated by the control module according to a formula (1) so as to obtain and store the effective X-ray dose of the current image gray value and the maximum X-ray intensity of each charge amplifier; the corresponding X-ray effective dose range is that the X-ray effective dose range corresponding to the X-ray effective dose corresponding to the minimum and maximum image gray level under the current charge gain level of each charge amplifier is directly stored by the control module 30 between the calculated effective doses of the two energy levels of X-rays. Similarly, the above method can obtain the effective X-ray dose corresponding to the minimum and maximum values of the image gray scale under each charge gain stage of each charge amplifier 10, and the effective X-ray dose ranges corresponding to the image gray scale under the condition of no excessively low and saturation are stored in the control module 30 respectively.
Step S2: during normal shooting, according to the calculated effective X-ray dose, the selection switch is controlled to be switched to a charge gain gear corresponding to the effective X-ray dose.
The method comprises the following substeps:
step S21: and emitting X-rays, measuring, transmitting the obtained voltage value of the X-ray intensity and the output time of the effective level to a control module, and calculating the effective dose of the X-rays.
X-rays are emitted through an X-ray tube, the X-rays pass through an object to be projected to the X-ray image detector, the X-rays are measured through the detection module T, and the obtained voltage value of the intensity of the X-rays and the output time of the effective level of the intensity of the X-rays are transmitted to the control module 30, so that the control module 30 calculates the effective dose of the X-rays according to the formula (1).
Step S22: judging whether the effective dose of the X-ray is between the minimum value and the minimum value of the corresponding effective dose of the X-ray under the current charge gain range according to the effective dose of the X-ray; if not, the selection switch is controlled to switch to a charge gain range corresponding to the effective dose of X-rays.
The control module 30 determines whether the effective dose of the X-rays calculated in step S21 is between the minimum and maximum image gray levels for each charge amplifier 10 stored in the effective dose of the X-rays, and if the effective dose of the X-rays is not between the minimum and maximum image gray levels for the stored current charge gain level, the control module 30 controls
And the first selection switch IGS [0] and the second selection switch IGS [1] are manufactured to switch each charge amplifier 10 to a charge gain stage corresponding to the X-ray effective agent, so that the image display effect is not affected due to low or saturated brightness of the image output under the X-ray effective agent, and the aims of accurate and efficient image processing and display are fulfilled.
Assuming that each charge amplifier 10 has 3 charge gain stages, the capacitance value of the feedback capacitor corresponding to each charge gain stage is 0.2pF, 0.5pF and 1pF, respectively; when the first selection switch IGS [0] and the second selection switch IGS [1] are both 0, the charge gain stage corresponding to the feedback capacitance of 0.2pF can be switched; when the first selection switch IGS [0] is 1 and the second selection switch IGS [1] is 0, the charge gain stage corresponding to the feedback capacitance of 0.5pF can be switched; when the first selection switch IGS [0] and the second selection switch IGS [1] are both 1, the charge gain stage corresponding to the feedback capacitance of 1pF can be switched. If each charge amplifier 10 is in the charge gain stage corresponding to the feedback capacitance of 0.5pF, the control module 30 determines that the effective dose of the emitted X-rays will saturate the image brightness in the current charge gain stage, and controls the first selection switch IGS [0] and the second selection switch IGS [1] to be 1, and switches the current charge gain stage to the charge gain stage corresponding to the feedback capacitance of 1pF, so as to satisfy that the effective dose of the emitted X-rays will not saturate the image brightness in the charge gain stage. If each charge amplifier 10 is in the charge gain stage corresponding to the feedback capacitance of 0.5pF, the control module 30 determines that the effective dose of the emitted X-ray will make the image brightness too low in the current charge gain stage, and controls the first selection switch IGS [0] and the second selection switch IGS [1] to be 0, so as to switch the current charge gain stage to the charge gain stage corresponding to the feedback capacitance of 0.2pF, thereby ensuring that the image display effect is not affected due to the low image brightness output in the effective dose of the X-ray, and achieving the purposes of accurate and efficient image processing and display.
The X-ray image detector provided by the invention obtains and stores the X-ray effective dose corresponding to the minimum and maximum values of the image gray level of each charge gain stage by carrying out pre-value detection on the X-ray effective dose when the image gray level of each charge gain stage of each charge amplifier is in an excessively low and saturated state; when the imaging device is used for shooting normally, according to the measured effective X-ray dose, the first selection switch and the second selection switch are controlled to be automatically switched to a charge gain gear corresponding to the effective X-ray dose, automatic, accurate and efficient imaging is achieved, saturation or low brightness of an image is prevented, image quality is improved, the film breakage rate is reduced, and accordingly the situation that a patient is repeatedly irradiated is avoided.
The X-ray image detector for realizing automatic gain switching and the method thereof provided by the invention are described in detail above. Any obvious modifications thereof, which would be apparent to those skilled in the art without departing from the true spirit of the present invention, would fall within the scope of the present patent claims.
Claims (8)
1. An X-ray image detector for implementing automatic gain switching, characterized in that: the device comprises a detection module, a selection switch, a control module, a plurality of charge amplifiers and a signal processing module; each charge amplifier is respectively connected with the corresponding signal processing module, each signal processing module is connected with the control module, the control module is respectively connected with the detection module and the selection switch, and the selection switch is respectively connected with each charge amplifier;
the detection module is realized by a semiconductor probe and is used for measuring the X-ray intensity and acquiring the voltage value of the X-ray intensity and the effective level output time; wherein the product of the voltage value of the X-ray intensity and the effective level output time is the effective dose of the X-ray;
transmitting the obtained image gray values corresponding to the X rays with different energy levels to the control module through the charge amplifier and the signal processing module under each charge gain stage of each charge amplifier to obtain the minimum value and the maximum value of the image gray corresponding to each charge gain stage;
the detection module is used for measuring the X-ray intensity corresponding to the minimum value and the maximum value of the image gray level of each charge gain stage of each charge amplifier respectively, and calculating and storing the minimum value and the maximum value of the effective X-ray dose corresponding to each charge gain stage through the control module;
and during normal shooting, the control module controls the selection switch to be switched to a charge gain gear corresponding to the effective X-ray dose according to the calculated effective X-ray dose.
2. The automatic gain switching X-ray image detector of claim 1, wherein:
each charge amplifier comprises a low-noise differential input single-ended output operational amplifier, a reset switch, a plurality of feedback capacitors with different capacitance values and a plurality of control switches; the inverting input end of the low-noise differential input single-ended output operational amplifier is respectively connected with the reset switch and one end of each control switch, the non-inverting input end of the low-noise differential input single-ended output operational amplifier is connected with the reference voltage, the other end of the reset switch is connected with the output end of the low-noise differential input single-ended output operational amplifier, the other end of each control switch is connected with one end of the corresponding feedback capacitor, and the other end of the feedback capacitor is respectively connected with the output end of the low-noise differential input single-ended output operational amplifier.
3. The automatic gain switching X-ray image detector of claim 2, wherein:
one end of each control switch is also connected with the other end of the selection switch, and the control switch is controlled by the selection switch so that the charge amplifier is switched to a charge gain switch corresponding to a certain feedback capacitor.
4. The automatic gain switching X-ray image detector of claim 1, wherein: each signal processing module obtains an image gray value corresponding to the X-rays acquired by the photoelectric conversion module according to the following formula;
wherein K represents a proportionality coefficient, vout represents a voltage signal processed by the signal processing module, and K is a positive number.
5. The X-ray image detector of claim 1 wherein the control module obtains the effective dose of X-rays at different energy levels according to the following formula:
where V represents a voltage value of the X-ray intensity, and s represents the X-ray intensity active level output time.
6. A method for implementing automatic gain switching of an X-ray image detector, based on the implementation of an X-ray image detector for implementing automatic gain switching according to any one of claims 1 to 5, characterized in that: the method comprises the following steps:
measuring the X-ray intensity corresponding to the minimum and maximum values of the image gray level of each charge gain stage of each charge amplifier, and calculating and storing the minimum and maximum values of the effective X-ray dose corresponding to each charge gain stage;
during normal shooting, according to the calculated effective X-ray dose, the selection switch is controlled to be switched to a charge gain gear corresponding to the effective X-ray dose.
7. The method for implementing automatic gain switching for an X-ray image detector according to claim 6, wherein: calculating and storing minimum and maximum effective X-ray dose values corresponding to each charge gain file, wherein the method comprises the following substeps:
transmitting the obtained image gray values corresponding to the X rays with different energy levels to corresponding control modules under each charge gain stage of each charge amplifier to obtain the minimum value and the maximum value of the image gray corresponding to each charge gain stage;
and respectively acquiring voltage values and effective level output time of the X-ray intensity corresponding to the minimum and maximum image gray levels of each charge gain stage, and transmitting the acquired voltage values and effective level output time of the X-ray intensity to the control module to respectively acquire the effective X-ray doses corresponding to the minimum and maximum image gray levels of each charge gain stage.
8. The method for implementing automatic gain switching for an X-ray image detector according to claim 6, wherein: according to the calculated effective X-ray dose, switching to a charge gain range corresponding to the effective X-ray dose, wherein the method comprises the following substeps:
transmitting X-rays, measuring, transmitting the obtained voltage value of the X-ray intensity and the output time of the effective level to a control module, and calculating the effective dose of the X-rays; judging whether the effective dose of the X-ray is between the minimum value and the minimum value of the corresponding effective dose of the X-ray under the current charge gain range according to the effective dose of the X-ray; if not, the selection switch is controlled to be switched to a charge gain gear corresponding to the effective dose of the X-ray.
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