WO2021208374A1 - 一种自动曝光控制系统及图像校正方法 - Google Patents

一种自动曝光控制系统及图像校正方法 Download PDF

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Publication number
WO2021208374A1
WO2021208374A1 PCT/CN2020/119674 CN2020119674W WO2021208374A1 WO 2021208374 A1 WO2021208374 A1 WO 2021208374A1 CN 2020119674 W CN2020119674 W CN 2020119674W WO 2021208374 A1 WO2021208374 A1 WO 2021208374A1
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Prior art keywords
circuit
ray
automatic exposure
ray source
output
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PCT/CN2020/119674
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English (en)
French (fr)
Inventor
崔志立
李运祥
张有为
魏青
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北京纳米维景科技有限公司
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Priority to EP20930977.2A priority Critical patent/EP4138383A4/en
Publication of WO2021208374A1 publication Critical patent/WO2021208374A1/zh
Priority to US18/046,920 priority patent/US20230068259A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/70—Circuitry for compensating brightness variation in the scene
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/0002—Inspection of images, e.g. flaw detection
    • G06T7/0012—Biomedical image inspection
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/58—Testing, adjusting or calibrating thereof
    • A61B6/582—Calibration
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V10/00—Arrangements for image or video recognition or understanding
    • G06V10/70—Arrangements for image or video recognition or understanding using pattern recognition or machine learning
    • G06V10/74—Image or video pattern matching; Proximity measures in feature spaces
    • G06V10/75—Organisation of the matching processes, e.g. simultaneous or sequential comparisons of image or video features; Coarse-fine approaches, e.g. multi-scale approaches; using context analysis; Selection of dictionaries
    • G06V10/751—Comparing pixel values or logical combinations thereof, or feature values having positional relevance, e.g. template matching
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N17/00—Diagnosis, testing or measuring for television systems or their details
    • H04N17/002—Diagnosis, testing or measuring for television systems or their details for television cameras
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/30—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from X-rays
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/70—Circuitry for compensating brightness variation in the scene
    • H04N23/73—Circuitry for compensating brightness variation in the scene by influencing the exposure time
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/30—Circuitry of solid-state image sensors [SSIS]; Control thereof for transforming X-rays into image signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/30—Transforming light or analogous information into electric information
    • H04N5/32—Transforming X-rays
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/40—Arrangements for generating radiation specially adapted for radiation diagnosis
    • A61B6/4007—Arrangements for generating radiation specially adapted for radiation diagnosis characterised by using a plurality of source units
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/54—Control of apparatus or devices for radiation diagnosis
    • A61B6/542—Control of apparatus or devices for radiation diagnosis involving control of exposure
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/54—Control of apparatus or devices for radiation diagnosis
    • A61B6/545—Control of apparatus or devices for radiation diagnosis involving automatic set-up of acquisition parameters
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10116—X-ray image
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10141—Special mode during image acquisition
    • G06T2207/10144—Varying exposure

Definitions

  • the invention relates to an automatic exposure control system, and also to a corresponding image correction method, belonging to the field of radiation imaging technology.
  • each X-ray source is set to the same exposure conditions (such as X-ray tube voltage and current, exposure time, referred to as kV, mA, and ms). There will be certain differences in the kV, mA, and ms of the X-rays actually output by each X-ray source.
  • the kV difference of X-rays is a difference in energy level, which will cause the calculated CT value (the pixels of the final image presented by the device to be represented by the CT value) will be biased, and the difference in the mA and ms of the X-ray will cause the difference in the signal-to-noise ratio , Thereby further affecting the calculation of the CT value.
  • the automatic exposure control (Auto Exposure Control, AEC) detector and high voltage generator are usually used online to realize automatic exposure control of the X-ray source.
  • the high-voltage generator receives the exposure signal (Spot signal), it emits X-rays.
  • the automatic exposure control detector integrates the energy of the X-rays and outputs an automatic exposure control signal.
  • the automatic exposure control signal is a ramp signal.
  • the high-voltage generator obtains the output signal of the threshold comparator and uses This shuts off the output of X-rays, so that the output energy of X-rays can be controlled.
  • the above-mentioned automatic exposure control is only for a single ray source, and is not suitable for a multi-ray source CT system. Therefore, it is necessary to design an automatic exposure control system to obtain the kV value of the actual X-ray and control the exposure time of the X-ray, so that the energy of the X-ray exposed by multiple X-ray sources in each projection exposure tends to be consistent.
  • the primary technical problem to be solved by the present invention is to provide an automatic exposure control system.
  • Another technical problem to be solved by the present invention is to provide an image correction method.
  • an automatic exposure control system including a main control unit and a plurality of automatic exposure units, the main control unit is connected to each of the automatic exposure units, and each of the automatic exposure units is In cascade connection, each of the automatic exposure units is installed at the exit of the corresponding X-ray source;
  • the automatic exposure unit is used to receive the exposure signal sent by the main control unit to detect the corresponding X-ray source to obtain the KV level of the X-ray output by the X-ray source, and at the same time, judge according to preset conditions Whether to send an automatic exposure control signal to the main control unit;
  • the main control unit adjusts the exposure timing according to receiving the automatic exposure control signal to achieve the purpose of automatic exposure control.
  • the preset condition is: when the automatic exposure unit detects the X-ray source, whether the obtained X-ray energy accumulation value reaches the preset X-ray energy output by the X-ray source Threshold.
  • the main control unit adopts a timing control board including a main controller and a first transceiver, the main controller is connected to the first transceiver, and the first transceiver uses a high-speed real-time serial
  • the bus is connected with each of the automatic exposure units.
  • each automatic exposure unit has a unique ID, and the ID of each automatic exposure unit is consistent with the ID of the corresponding X-ray source.
  • each of the automatic exposure units is cascaded through a high-speed real-time serial bus to interact with working parameters and detection results.
  • each of the automatic exposure units includes an automatic exposure control module and a processing module
  • the automatic exposure control module is connected to the output terminal of the main control unit on the one hand, and connected to the input terminal of the processing module on the other hand.
  • the output terminal of the processing module is connected to the input terminal of the main control unit.
  • the automatic exposure control module includes a first X-ray probe, a second X-ray probe, a first integration circuit, a second integration circuit, and a comparison circuit.
  • the output terminal of the first X-ray probe, the The processing module is respectively connected to the input terminal of the first integrating circuit, the output terminal of the second X-ray probe and the processing module are respectively connected to the input terminal of the second integrating circuit, and the output terminal of the first integrating circuit
  • the input terminal of the comparison circuit and the processing module are respectively connected, and the input and output terminals of the comparison circuit and the output terminal of the second integrating circuit are respectively connected to the processing module.
  • the automatic exposure control module includes a first X-ray probe, a second X-ray probe, a first integration circuit, a second integration circuit, and a comparison circuit.
  • the output terminal of the first X-ray probe and the The processing modules are respectively connected to the input terminals of the first integration circuit, the output terminals of the second X-ray probe and the processing module are respectively connected to the input terminals of the second integration circuit, and the output terminals of the second integration circuit.
  • the input terminal of the comparison circuit and the processing module are respectively connected, and the input and output terminals of the comparison circuit and the output terminal of the first integrating circuit are respectively connected to the processing module.
  • the automatic exposure control module includes a first X-ray probe, a second X-ray probe, a third X-ray probe, a first integration circuit, a second integration circuit, a third integration circuit, a first subtraction circuit, A second subtraction circuit and a comparison circuit; the output terminal of the first X-ray probe and the processing module are respectively connected to the input terminal of the first integrating circuit, the output terminal of the third X-ray probe, the processing module Are respectively connected to the input terminals of the third integration circuit, the output terminals of the second X-ray probe and the processing module are respectively connected to the input terminals of the second integration circuit, and the output terminals of the first integration circuit are respectively connected to The input terminal of the first subtraction circuit and the processing module, the output terminal of the third integration circuit are respectively connected to the input terminals of the first subtraction circuit and the second subtraction circuit, and the second integration circuit
  • the output terminal is connected to the input terminal of the second subtraction circuit, the output terminal of the first subtraction circuit is connected to the input terminal of the
  • the automatic exposure control module includes a first X-ray probe, a second X-ray probe, a third X-ray probe, a first integration circuit, a second integration circuit, a third integration circuit, a first subtraction circuit, A second subtraction circuit and a comparison circuit; the output terminal of the first X-ray probe and the processing module are respectively connected to the input terminal of the first integrating circuit, the output terminal of the third X-ray probe, the processing module Are respectively connected to the input terminals of the third integration circuit, the output terminals of the second X-ray probe and the processing module are respectively connected to the input terminals of the second integration circuit, and the output terminals of the first integration circuit are respectively connected to The input terminal of the first subtraction circuit and the processing module, the output terminal of the third integration circuit are respectively connected to the input terminals of the first subtraction circuit and the second subtraction circuit, and the second integration circuit
  • the output terminal is connected to the input terminal of the second subtraction circuit, the output terminal of the second subtraction circuit is connected to the input terminal of the
  • the processing module includes a digital-to-analog conversion circuit, the first analog-to-digital conversion circuit, a second analog-to-digital conversion circuit, a processor, and a second transceiver; the input terminal of the digital-to-analog conversion circuit is connected to the In the processor, the output terminal of the digital-to-analog conversion circuit is connected to the input terminal of the comparison circuit, the input terminal of the first analog-to-digital conversion circuit is connected to the output terminal of the first integrating circuit, and the second analog-to-digital conversion circuit is connected to the output terminal of the first integrating circuit.
  • the input end of the conversion circuit is connected to the output end of the second integrating circuit, the output ends of the comparison circuit, the first analog-to-digital conversion circuit, and the second analog-to-digital conversion circuit are connected to the processor, and the processing
  • the second transceiver is connected to the second transceiver, and the second transceiver is connected to the main control unit through a high-speed real-time serial bus.
  • the processing module includes a digital-to-analog conversion circuit, the first analog-to-digital conversion circuit, a second analog-to-digital conversion circuit, a processor, and a second transceiver; the input terminal of the digital-to-analog conversion circuit is connected to the In the processor, the output terminal of the digital-to-analog conversion circuit is connected to the input terminal of the comparison circuit, the input terminal of the first analog-to-digital conversion circuit is connected to the output terminal of the first subtraction circuit, and the second analog The input terminal of the digital conversion circuit is connected to the output terminal of the second subtraction circuit, the output terminals of the comparison circuit, the first analog-to-digital conversion circuit, and the second analog-to-digital conversion circuit are connected to the processor, the The processor is connected to the second transceiver, and the second transceiver is connected to the main control unit through a high-speed real-time serial bus.
  • an image correction method including the following steps:
  • Step S1 Obtain the initial reference pixel value of each X-ray source and the current image reference pixel value
  • Step S2 when images are collected normally, correct the obtained current image of each X-ray source according to the initial reference pixel value of each X-ray source and the current image reference pixel value;
  • Step S3 Obtain KV correction template coefficients of X-rays output by each X-ray source
  • Step S4 Perform KV correction on the image in step S2 according to the KV correction template coefficient of the X-ray.
  • step S1 includes the following sub-steps:
  • Step S11 For each of the X-ray sources, a dark field template and an air correction template are obtained respectively;
  • Step S12 Obtain the initial reference pixel value of each X-ray source according to the air correction template of each X-ray source;
  • Step S13 Obtain the actual projection image corresponding to each X-ray source, and obtain the current image reference pixel value of each X-ray source according to the actual projection image corresponding to each X-ray source.
  • the average gray value of each pixel of the dark field image of the X-ray source is obtained as the Dark field template.
  • the obtained gray values of the pixels of the multiple projection images corresponding to each of the X-ray sources are averaged, and the corresponding X-ray sources are respectively subtracted.
  • a dark field template is used as the air correction template for each X-ray source.
  • the mean value of all pixels in the column multiple pixels from the left and the mean value of the column multiple pixels from the right, whichever is greater is used as the initial reference pixel value of each X-ray source.
  • each pixel of the image obtained after exposure of each X-ray source is multiplied by the ratio of the initial reference pixel value of the corresponding X-ray source to the reference pixel value of the current image. , In order to get a group of images with the same overall gray value.
  • the KV level of the X-ray is the ratio of the first energy accumulation value and the second energy accumulation value of the X-ray.
  • the KV level of the X-ray is normalized to obtain the kV correction template coefficient.
  • the ratio of the pixel gray value of the image obtained after exposure of each X-ray source to the pixel gray value of the corresponding X-ray source air correction template is divided by Corresponding kV correction template coefficient.
  • the automatic exposure control system and image correction method provided by the present invention realize the detection of each X-ray source by setting the same number of automatic exposure units as the X-ray source to obtain the X-ray energy accumulation value and KV level, and when the X-ray source When the energy accumulation value of the ray reaches the energy threshold, the automatic exposure control signal is sent to the main control unit, so that the main control unit adjusts the exposure timing according to the automatic exposure control signal, and achieves the purpose of automatic exposure control at the same time, makes the X-ray single exposure output
  • the energy of X-ray is kept relatively fixed, and the problem of unstable X-ray output is optimized, so as to solve the problem of inconsistent X-ray output among various ray sources in the X-ray imaging system of multiple ray sources.
  • Figure 1 is a topological structure diagram of the automatic exposure control system provided by the present invention.
  • FIG. 2 is a structural diagram 1 of an automatic exposure control module in the automatic exposure control system provided by the present invention
  • FIG. 3 is a schematic structural diagram 2 of an automatic exposure control module in the automatic exposure control system provided by the present invention.
  • FIG. 4 is a schematic structural diagram 1 of another automatic exposure control module in the automatic exposure control system provided by the present invention.
  • FIG. 5 is a schematic structural diagram 2 of another automatic exposure control module in the automatic exposure control system provided by the present invention.
  • Fig. 6 is a flowchart of an image correction method provided by the present invention.
  • Figures 7 and 8 are the images after exposure of two X-ray sources respectively collected by two X-ray detectors before using the automatic exposure control system and image correction method provided by the present invention
  • Figures 9 and 10 show the exposure images of two X-ray sources collected by two X-ray detectors after using the automatic exposure control system and image correction method provided by the present invention.
  • the present invention provides an automatic exposure control system, including a main control unit 1 and multiple automatic The exposure unit 2, the main control unit 1 and each automatic exposure unit 2 are connected, the automatic exposure units 2 are cascaded, and each automatic exposure unit 2 is installed at the outlet of the corresponding X-ray source.
  • the automatic exposure unit 2 is used to receive the exposure signal sent by the main control unit 1 to detect the corresponding X-ray source to obtain the KV level of the X-ray output by the X-ray source and send it to the main control unit 1, and at the same time according to the preset Condition, determine whether to send an automatic exposure control signal to the main control unit 1.
  • the main control unit 1 adjusts the exposure timing according to the received automatic exposure control signal to achieve the purpose of automatic exposure control.
  • the preset condition is: when the automatic exposure unit 2 detects the X-ray source, whether the obtained X-ray energy accumulation value reaches the preset X-ray energy threshold value of the X-ray output by the X-ray source.
  • the energy accumulation value and energy threshold of the X-rays emitted by each X-ray source are presented in the form of voltage.
  • the set energy threshold of the X-ray output by each X-ray source is the same, and the energy threshold is set according to the X-ray energy required for each image acquisition and to ensure that the displayed image tends to an appropriate level.
  • the main control unit 1 sets the energy threshold of the X-ray output by the X-ray source corresponding to each automatic exposure unit 2 to control the energy level of the X-ray output by the automatic exposure of the designated X-ray source.
  • the obtained X-ray energy accumulation value is the energy accumulation value of the X-ray emission from the X-ray source.
  • the main control unit 1 adopts a timing control board that includes a main controller, FPGA (Field-Programmable Gate Array), and a first transceiver.
  • the main controller of the timing control board is connected to the first transceiver, and the A transceiver is connected to each automatic exposure unit 2 through a high-speed real-time serial bus.
  • the main control unit 1 can generate the exposure sequence.
  • the main control unit 1 sends a preparation signal to the high-voltage generator, it is designated to send exposure signals to one or more automatic exposure units 2 to turn on the automatic exposure unit 2, which not only realizes the specified X
  • the detection of the ray source also realizes the designation of one or more X-ray sources for exposure.
  • the main controller includes but is not limited to FPGA (Field-Programmable Gate Array) or CPLD (Complex Programmable Logic Device),
  • the automatic exposure control signal is sent to the main control unit 1, so that the main control unit 1 adjusts the exposure timing according to the automatic exposure control signal to achieve the purpose of automatic exposure control. Specifically, the main control unit 1 adjusts the width of the exposure signal sent to the corresponding automatic exposure unit 2 according to the automatic exposure control signal to stop the exposure action of the corresponding X-ray source.
  • the main control unit 1 Since the automatic exposure control signal is at a high level, when the main control unit 1 receives the automatic exposure control signal sent by one or more automatic exposure units 2, it needs to adjust the exposure signal sent to the corresponding automatic exposure unit 2 to low Level, so that the corresponding automatic exposure unit 2 stops detecting the X-ray source. At this time, the main control unit 1 also controls the high-voltage generator to stop providing high-voltage signals to the X-ray source to achieve the X-ray source of the corresponding X-ray source.
  • the main control unit 1 is also used to provide cascaded power for each automatic exposure unit 2 and is also responsible for the control of the high-speed real-time serial bus.
  • the high-speed real-time serial bus includes power supply and bus signals.
  • the high-speed real-time serial bus has an external interface with a pair of power supplies, a pair of ground and two differential half-duplex buses to form a full-duplex bus.
  • the four sets of power and bus signals of the high-speed real-time serial bus each use a pair of twisted pairs.
  • the high-speed real-time serial bus defines the information update cycle according to the needs of the system, and defines the basic baud rate according to the basic frame format data bits and the reliable margin bits. For example, if the information update period is defined as 1 us according to the needs of the system, the basic frame format data bits are 20 bits, and the reliability margin is 5 bits, the basic baud rate is (20+5)/1 us, which is 25MBps.
  • the main control unit 1 not only realizes the cascade power supply for each automatic exposure unit 2 through the high-speed real-time serial bus, but also sends the exposure signal for the X-ray source exposure and the X-ray energy threshold for comparison to the specified through the high-speed real-time serial bus.
  • the automatic exposure unit 2. On the other hand, the automatic exposure unit 2 sends the automatic exposure control signal and the KV level of the X-ray output by the X-ray source to the main control unit 1 through the high-speed real-time serial bus.
  • Each automatic exposure unit 2 has a unique ID to define its address.
  • the ID is identified by the source ID and focus ID, and the ID of each automatic exposure unit 2 is consistent with the ID of the corresponding X-ray source to identify The assembled automatic exposure unit 2 and the X-ray source have the same ID.
  • the main control unit 1 can broadcast the exposure timing to each automatic exposure unit 2 through a differential half-duplex bus, that is, the exposure signal, source ID and focus ID information to specify One or more X-ray sources perform exposure actions; since the main control unit 1 and each automatic exposure unit 2 are in the receiving state by default, when the designated one or more automatic exposure units 2 work, each automatic exposure unit 2 switches For the sending mode, the automatic exposure control signal and the KV level of the X-ray output by the X-ray source are sent to the main control unit 1, so that the main control unit 1 responds to the automatic exposure control signal fed back by the automatic exposure unit 2 corresponding to the specified X-ray source , Adjust the exposure timing of the X-ray source to achieve the purpose of automatic exposure control.
  • Each automatic exposure unit 2 is cascaded through a high-speed real-time serial bus to interactively work parameters and test results, and is beneficial to the reliability and engineering of the system.
  • Each automatic exposure unit 2 is assembled at the exit of the X-ray source, and there is no image of X-ray scattering caused by other measured objects, so that the detection result is more accurate.
  • each automatic exposure unit 2 includes an automatic exposure control module 21 and a processing module 22.
  • the automatic exposure control module 21 is connected to the output terminal of the main control unit 1 on the one hand, and to the processing module 22 on the other hand.
  • the input terminal, the output terminal of the processing module 22 is connected to the input terminal of the main control unit 1.
  • the main control unit 1 After the main control unit 1 sends a preparation signal to the high-voltage generator, it is designated to send an exposure signal to the automatic exposure control module 21 of one or more automatic exposure units 2 to turn on the automatic exposure control module 21 to achieve the specified X-ray source Detect and output the X-ray energy accumulation value obtained in real time to the processing module 22 to obtain the KV level of the X-ray output by each X-ray source and send it to the main control unit 1.
  • the processing module 22 sends an automatic exposure control signal to the main control unit 1, In this way, the main control unit 1 adjusts the exposure timing according to the automatic exposure control signal to achieve the purpose of automatic exposure control.
  • the automatic exposure control module 21 includes a first X-ray probe 210, a second X-ray probe 211, a first integration circuit 212, a second integration circuit 213, and a comparison circuit 214.
  • the parts of the automatic exposure control module 21 can have the following two connection relationships.
  • the first connection relationship is: the output terminal of the first X-ray probe 210 and the processing module 22 are respectively connected to the input terminal of the first integrating circuit 212, and the second The output terminal of the X-ray probe 211 and the processing module 22 are respectively connected to the input terminal of the second integration circuit 213, and the output terminal of the first integration circuit 212 is respectively connected to the input terminal of the comparison circuit 214 and the processing module 22.
  • the input and output of the comparison circuit 214 are The terminal and the output terminal of the second integrating circuit 213 are respectively connected to the processing module 22.
  • the second connection relationship of each part of the automatic exposure control module 21 is: the output end of the first X-ray probe 210 and the processing module 22 are respectively connected to the input end of the first integrating circuit 212, and the second X-ray probe 211
  • the output terminal and the processing module 22 are respectively connected to the input terminal of the second integration circuit 213, the output terminal of the second integration circuit 213 is respectively connected to the input terminal of the comparison circuit 214 and the processing module 22, the input and output terminals of the comparison circuit 214 and the first
  • the output ends of the integration circuit 212 are respectively connected to the processing module 22.
  • the working principles of the two connection relationships of the automatic exposure control module 21 of this embodiment are the same, except that in the process of realizing the automatic exposure control of the X-ray source, the first energy of the X-ray obtained by the first integrating circuit 212 can be selected.
  • the cumulative value I 0 or the second X-ray energy cumulative value I obtained by the second integration circuit 212 is output to the comparison circuit 214 to determine whether the X-ray first energy cumulative value or the X-ray second energy cumulative value I has reached a predetermined value.
  • Set the energy threshold of the X-ray to determine whether to send an automatic exposure control signal to the main control unit 1, so that the main control unit adjusts the exposure timing to achieve the purpose of automatic exposure control.
  • the working principle of the automatic exposure control module 21 provided in this embodiment is described in detail by taking the output of the first energy accumulation value I 0 of the X-ray obtained by the first integrating circuit 212 to the comparison circuit 214 as an example.
  • the main control unit 1 sets the energy threshold of the X-ray output from the X-ray source corresponding to each automatic exposure unit 2, and transmits the energy threshold to the comparison circuit 214 through the processing module 22.
  • the main control unit 1 sends an exposure signal (Spot signal as shown in FIG.
  • the first X-ray probe 210 and the second X-ray probe 211 start to detect X-rays emitted from the X-ray source to continuously obtain the first X-ray current and the second X-ray current, and combine the first X-ray current and the second X-ray current.
  • An X-ray current and a second X-ray current are correspondingly output to the first integration circuit 212 and the second integration circuit 213 to realize the energy accumulation of X-rays; the first X-ray energy accumulation value I obtained by the first integration circuit 212 0 and the second energy accumulation value I of the X-ray obtained by the second integrating circuit 212 are respectively output to the processing module 22 to obtain the KV level of the X-ray output by the designated X-ray source.
  • the X-ray first energy accumulation value I 0 obtained by the first integration circuit 212 is also output to the comparison circuit 214, and the comparison circuit 214 compares the X-ray first energy accumulation value I 0 with the X-ray energy threshold. If the X-ray first energy accumulation value reaches the preset X-ray energy threshold, the processing module 22 sends an automatic exposure control signal (AECSpot signal as shown in FIG.
  • the main control unit 1 controls the high-voltage generator to stop supplying high voltage to the X-ray source, so as to shut off the X-ray output of the corresponding X-ray source; at the same time, the main control unit 1 also adjusts to the first integrating circuit 212, The width of the exposure signal sent by the second integrator circuit 213, that is, the exposure signal sent to the first integrator circuit 212 and the second integrator circuit 213 is closed, so that the first integrator circuit 212 and the second integrator circuit 213 remain in the cleared state, thereby realizing the stop The corresponding exposure action of the X-ray source.
  • the transmission of X-rays emitted by the X-ray source in the material follows the law of attenuation, it is based on changing the thickness of the absorbing material between the X-ray source and the probe to detect different X-ray intensities (X-ray intensity). Energy accumulation value).
  • the absorption material between the X-ray source and the first X-ray probe 210 and the second X-ray probe 211 is set to different thicknesses to obtain the first X-ray energy accumulation value I 0 and The second energy accumulation value I.
  • the first X-ray probe 210 and the second X-ray probe 211 will also have background currents when the X-ray source does not emit X-rays. It is relatively small, and has little effect on the first energy accumulation value I 0 and the second energy accumulation value I of the X-ray finally obtained, so the background detection in the case of no X-ray output can be ignored.
  • the automatic exposure control module 21 includes a first X-ray probe 210, a second X-ray probe 211, a third X-ray probe 215, a first integrating circuit 212, and a second X-ray probe.
  • the second integration circuit 213, the third integration circuit 216, the first subtraction circuit 217, the second subtraction circuit 218, and the comparison circuit 214; each part of the automatic exposure control module 21 can have the following two connection relationships:
  • the first connection relationship is: the output terminal of the first X-ray probe 210 and the processing module 22 are respectively connected to the input terminal of the first integrating circuit 212, and the output terminal of the third X-ray probe 215 and the processing module 22 are respectively connected to the third integrating circuit.
  • the input terminal of 216, the output terminal of the second X-ray probe 211, and the processing module 22 are respectively connected to the input terminal of the second integration circuit 213, and the output terminal of the first integration circuit 212 is respectively connected to the input terminal of the first subtraction circuit 217 and the processing module 22.
  • the output terminal of the third integration circuit 216 is connected to the input terminals of the first subtraction circuit 217 and the second subtraction circuit 218, respectively.
  • the output terminal of the second integration circuit 213 is connected to the input terminal of the second subtraction circuit 218, and the first subtraction circuit 217
  • the output terminal of is connected to the input terminal of the comparison circuit 214, and the input and output terminals of the comparison circuit 214 and the output terminals of the first subtraction circuit 217 and the second subtraction circuit 218 are respectively connected to the processing module 22.
  • the second connection relationship of each part of the automatic exposure control module 21 is: the output end of the first X-ray probe 210 and the processing module 22 are respectively connected to the input end of the first integrating circuit 212, and the third X-ray probe 215
  • the output terminal and the processing module 22 are respectively connected to the input terminal of the third integration circuit 216
  • the output terminal of the second X-ray probe 211 and the processing module 22 are respectively connected to the input terminal of the second integration circuit 213, and the output terminal of the first integration circuit 212
  • the input terminal of the first subtraction circuit 217 and the processing module 22 are respectively connected
  • the output terminal of the third integration circuit 216 is connected to the input terminals of the first subtraction circuit 217 and the second subtraction circuit 218, and the output terminal of the second integration circuit 213 is connected to the
  • the input terminal of the second subtraction circuit 218, the output terminal of the second subtraction circuit 218 are connected to the input terminal of the comparison circuit 214, the input and output terminals of the comparison circuit 214, and the output terminal
  • the working principle of the automatic exposure control module 21 of this embodiment is different from the automatic exposure control module 21 of the above embodiment in that: when the automatic exposure control module 21 of this embodiment detects the X-ray source, it takes X-rays into consideration. When the source does not emit X-rays, the first X-ray probe 210 and the second X-ray probe 211 will also have background currents. Therefore, the automatic exposure control module 21 of this embodiment performs complete light-shielding treatment on the third X-ray probe 215.
  • the background current output when the X-ray source does not emit X-rays is obtained, and the background current is output to the third integrating circuit 216 to obtain the background energy accumulation value K of the X-rays, and the background energy accumulation value K is output respectively To the first subtraction circuit 217 and the second subtraction circuit 218, so that the first subtraction circuit 217 can subtract the background energy accumulation value from the first energy accumulation value including the X-ray background energy obtained by the first integration circuit 212 After the value K, the first energy accumulation value I 0 of X-rays is obtained; similarly, the second subtraction circuit 218 subtracts the background energy from the second energy accumulation value of the received X-ray background energy obtained by the second integration circuit 213 After the energy accumulation value K, the second X-ray energy accumulation value I is obtained.
  • the comparison circuit 214 compares the received X-ray first energy accumulation value I 0 with the X-ray energy threshold value. In comparison, if the X-ray first energy accumulation value reaches the preset X-ray energy threshold, the processing module 22 sends an automatic exposure control signal to the main control unit 1, so that the main control unit 1 controls the high-voltage generator to stop sending the X-ray energy.
  • the ray source provides high voltage to shut off the X-ray output of the corresponding X-ray source; at the same time, the main control unit 1 will also adjust the exposure signal sent to the first integration circuit 212 and the second integration circuit 213 according to the automatic exposure control signal.
  • the width that is, the exposure signal sent to the first integration circuit 212 and the second integration circuit 213 is closed, so that the first integration circuit 212 and the second integration circuit 213 remain cleared, so as to stop the exposure action of the corresponding X-ray source.
  • the processing module 22 includes a digital-to-analog conversion circuit 220, a first analog-to-digital conversion circuit 221, a second analog-to-digital conversion circuit 222, a processor 223, and a second transceiver; wherein, the processor 223 includes But it is not limited to FPGA (Field-Programmable Gate Array), CPLD (Complex Programmable Logic Device, complex programmable logic device). The following uses an FPGA as an example for the processor 223 to describe the connection relationship between the various parts of the processing module 2.
  • FPGA Field-Programmable Gate Array
  • CPLD Complex Programmable Logic Device, complex programmable logic device
  • each part of the processing module 22 has two connection relationships; as shown in FIG. 2 and FIG. 3, when the first type of automatic exposure control module 21 is used, the connection of each part of the processing module 22
  • the relationship is: the input terminal of the digital-to-analog conversion circuit 220 is connected to the FPGA 223, the output terminal of the digital-to-analog conversion circuit 220 is connected to the input terminal of the comparison circuit 214, and the input terminal of the first analog-to-digital conversion circuit 221 is connected to the first integral of the automatic exposure control module 21
  • the output terminal of the circuit 212, the input terminal of the second analog-to-digital conversion circuit 222 is connected to the output terminal of the second integration circuit 212 of the automatic exposure control module 21, the comparison circuit 214, the first analog-to-digital conversion circuit 221, and the second analog-to-digital conversion circuit
  • the output terminal of 222 is connected to the FPGA 223, and the FPGA 223 is connected to the second transceiver.
  • the second transceiver is
  • the connection relationship of each part of the processing module 22 is: the input terminal of the digital-to-analog conversion circuit 220 is connected to the FPGA 223, and the output terminal of the digital-to-analog conversion circuit 220
  • the input terminal of the comparison circuit 214 is connected, the input terminal of the first analog-to-digital conversion circuit 221 is connected to the output terminal of the first subtraction circuit 217, and the input terminal of the second analog-to-digital conversion circuit 222 is connected to the output terminal of the second subtraction circuit 218.
  • the output terminals of the circuit 214, the first analog-to-digital conversion circuit 221, and the second analog-to-digital conversion circuit 222 are connected to the FPGA 223, which is connected to the second transceiver, and the second transceiver is connected to the first transceiver of the main control unit 1 through a high-speed real-time serial bus. Device.
  • the working principle of the processing module 22 is: the main control unit 1 sets the energy threshold of the X-ray output by the X-ray source corresponding to each automatic exposure unit 2, and sends the energy threshold to the FPGA 223 through the second transceiver, and the FPGA 223 will The energy threshold is sent to the digital-to-analog conversion circuit 220 and converted into an analog voltage, and then sent to the comparison circuit 214; the automatic exposure control module 21 detects the X-ray source, and the obtained first energy accumulation value c and the second energy accumulation value I correspond to After the first analog-to-digital conversion circuit 221 and the second analog-to-digital conversion circuit 222 convert them into digital signals, they are sent to the FPGA 223.
  • the FPGA 223 divides the first energy accumulation value I 0 and the second energy accumulation value I to obtain I/I 0 is the KV level of the X-ray output from the X-ray source, and is uploaded to the main control unit 1 through the second transceiver.
  • the FPGA223 is also used to receive the automatic exposure control signal and upload it to the main control unit 1 through the second transceiver, so that the main control unit 1 adjusts the exposure timing according to the automatic exposure control signal to achieve the purpose of automatic exposure control.
  • the automatic exposure control system realizes the detection of each X-ray source by setting the same number of automatic exposure units as the X-ray source to obtain the X-ray energy accumulation value and KV level, and when When the X-ray energy accumulation value reaches the energy threshold, it sends an automatic exposure control signal to the main control unit, so that the main control unit adjusts the exposure timing according to the automatic exposure control signal, and achieves the purpose of automatic exposure control while making the X-ray single exposure
  • the output energy is kept relatively fixed, and the problem of unstable X-ray output is optimized, thereby solving the problem of inconsistent X-ray output among various ray sources in an X-ray imaging system of multiple ray sources.
  • the present invention also provides an image correction method, which is used to further improve the problem of inconsistent brightness of the image obtained after each X-ray source is exposed. As shown in FIG. 6, the image correction method includes the following steps:
  • Step S1 Obtain the initial reference pixel value of each X-ray source and the current image reference pixel value.
  • This step includes the following sub-steps:
  • Step S11 For each X-ray source, a dark field template and an air correction template are obtained respectively.
  • the X-ray source does not emit X-rays, collect multiple (such as ⁇ 20) dark field images for each X-ray source separately, and compare the grayscale of the pixels of the multiple dark field images of each X-ray source The values are averaged, and the average gray value of the pixels of the dark field image of each X-ray source is obtained and saved as a dark field template of each X-ray source.
  • the X-ray emission conditions as the conditions required by the application, obtain multiple (such as ⁇ 20) projection images of each X-ray source, and set the multiple corresponding to each X-ray source
  • the gray values of the pixels of the projected image are averaged to obtain the average gray values of the pixels of each X-ray source projection image.
  • the average gray values of the pixels of each X-ray source projection image are subtracted After the dark field template of the corresponding X-ray source is saved, it is used as the air calibration template of each X-ray source.
  • Step S12 Obtain the initial reference pixel value of each X-ray source according to the air correction template of each X-ray source.
  • Step S13 Obtain the actual projection image corresponding to each X-ray source, and obtain the current image reference pixel value of each X-ray source according to the actual projection image corresponding to each X-ray source.
  • the mean value of all pixels in the column with multiple (such as 10) pixels from the left and the mean value of the column with multiple (such as 10) pixels from the right take The larger average pixel value is used as the current image reference pixel value of each X-ray source.
  • Step S2 When images are collected normally, the current image of each X-ray source obtained is corrected according to the initial reference pixel value of each X-ray source and the current image reference pixel value.
  • each pixel of the image obtained after exposure of each X-ray source is multiplied by the ratio of the initial reference pixel value of the corresponding X-ray source to the reference pixel value of the current image to obtain the overall gray
  • a group of images with basically the same degree value can effectively suppress the influence of unstable X-ray output on image processing, thereby solving the problem of inconsistent X-ray output among various ray sources in an X-ray imaging system with multiple ray sources.
  • two X-ray detectors are used to collect the exposure images of the two X-ray sources.
  • Figure 7 shows the use of the first X-ray detection
  • the image after exposure of the X-ray source collected by the detector, the mean gray value of the image, Mean is 20446.68
  • Figure 8 is the image after the exposure of the X-ray source collected by the second X-ray detector, the mean gray value of the image is 20951.46, the gray value difference between the images of the two X-ray sources is 504.78.
  • the two X-ray detectors collect the exposed images of the above two X-ray sources respectively.
  • Figure 9 shows the X-ray source collected by the first X-ray detector.
  • the mean gray value of the image is 20734.22, which is slightly improved compared to the overall brightness of the image in Figure 7;
  • Figure 10 is the image after the exposure of the X-ray source collected by the second X-ray detector.
  • the mean gray value Mean of is 20788.42, which is slightly lower than the overall brightness of the image in Fig. 2.
  • the gray value difference between the images of the two X-ray sources is 54.2. It is not difficult to find that the gray scale difference between the images of the two X-ray sources is greatly reduced; therefore, after using this image correction method, it is beneficial to improve the problem of inconsistent brightness of the images obtained after each X-ray source is exposed.
  • Step S3 Obtain KV correction template coefficients of X-rays output by each X-ray source.
  • the automatic exposure unit 2 of the automatic exposure control system realizes detection of each X-ray source to obtain the KV level of X-ray output by each X-ray source, and return the kV level of X-ray output from each X-ray source A unified processing to obtain kV correction template coefficients.
  • the process of obtaining the KV level of the X-ray output by each X-ray source is: the X-ray source is detected by the automatic exposure unit 2, and the first energy accumulation value I 0 and the second energy accumulation value I of the X-ray are obtained respectively, and the The first energy accumulation value I 0 of the X-ray and the second energy accumulation value I are divided to obtain I/I 0 , which is the KV level of the X-ray output by the X-ray source.
  • the specific realization process of the automatic exposure unit 2 obtaining the first energy accumulation value I 0 and the second energy accumulation value I of the X-ray is the same as the above.
  • Step S4 Perform KV correction on the image in step S2 according to the KV correction template coefficient of the X-ray.
  • the automatic exposure control system realizes the detection of each X-ray source, and sends the obtained KV level of the X-ray output by each X-ray source to the industrial computer, so that the industrial computer can check the X-ray output of each X-ray source
  • the kV correction template coefficient is obtained, and the X-ray KV correction template coefficient and air correction template are used to obtain the image after exposure to the X-ray source sent by the X-ray image detector during normal image acquisition. KV correction of the image.
  • the ratio of the pixel gray value of the image obtained after exposure of each X-ray source to the pixel gray value of the corresponding X-ray source air correction template is divided by the corresponding kV correction template Coefficient, to achieve KV correction of the image obtained after exposure of the X-ray source to improve the accuracy of image reconstruction.

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Abstract

本发明公开了一种自动曝光控制系统及图像校正方法。该系统包括主控单元和多个自动曝光单元，主控单元和各自动曝光单元连接，各自动曝光单元之间级联。该系统通过自动曝光单元实现对各X射线源的检测，以获得X射线的能量累积值和KV水平，并且当X射线的能量累积值达到能量阈值时，向主控单元发送自动曝光控制信号，使得主控单元根据自动曝光控制信号，调整曝光时序，达到自动曝光控制的目的的同时，使X射线单次曝光输出的能量保持相对固定，优化X射线输出不稳定的问题，从而解决多个射线源的X射线影像系统中各个射线源间X射线输出不一致的问题。

Description

一种自动曝光控制系统及图像校正方法 技术领域
本发明涉及一种自动曝光控制系统，同时也涉及相应的图像校正方法，属于辐射成像技术领域。
背景技术
针对多源静态CT系统，由于X射线源个体性能的差异，导致将每个X射线源设置相同的曝光条件(如X射线管电压和电流、曝光时间，简称kV、mA和ms)后，每个X射线源实际输出的X射线的kV、mA和ms会存在一定差异。其中，X射线的kV差异属于能量级别差异，会导致计算的CT值(设备最终呈现的图像的像素用CT值表示)会出现偏差，而X射线的mA和ms差异会造成信噪比的差异，从而进一步影响CT值的计算。
通常采用自动曝光控制(Auto Exposure Control，AEC)探测器和高压发生器联机实现对X射线源的自动曝光控制。当高压发生器接收到曝光信号(Spot信号)便发射X射线，同时，自动曝光控制探测器对X射线进行能量积分并输出自动曝光控制信号。一般情况下，该自动曝光控制信号为斜坡信号，当自动曝光控制信号高于高压发生器内部设置的阈值比较器所设定的阈值电压时，高压发生器获取阈值比较器的输出信号，并以此闸断X射线的输出，从而使得X射线的输出能量获得控制。
但是，上述的自动曝光控制仅针对单个射线源，并不适用于多射线源的CT系统。因此，需要设计一种自动曝光控制系统，用于获得实际X射线的kV值，并控制X射线的曝光时间，使得多个X射线源每次投影曝光的X射线的能量趋于一致。
发明内容
本发明所要解决的首要技术问题在于提供一种自动曝光控制系统。
本发明所要解决的另一技术问题在于提供一种图像校正方法。
为了实现上述目的，本发明采用下述的技术方案：
根据本发明实施例的第一方面，提供一种自动曝光控制系统，包括主控单元和多个自动曝光单元，所述主控单元和各所述自动曝光单元连接，各所述自动曝光单元之间级联，每个所述自动曝光单元安装在对应的X射线源的出口处；
所述自动曝光单元，用于接收所述主控单元发送的曝光信号，以对相应的X射线源进行检测，获得所述X射线源输出的X射线的KV水平，同时根据预设条件，判断是否向所述主控单元发送自动曝光控制信号；
所述主控单元根据接收所述自动曝光控制信号，调整曝光时序，以达到自动曝光控制的目的。
其中较优地，所述预设条件是：所述自动曝光单元检测所述X射线源时，获得的X射线的能量累积值是否达到预先设定的所述X射线源输出的X射线的能量阈值。
其中较优地，所述主控单元采用包含有主控器、第一收发器的时序控制板，所述主控器连接所述第一收发器，所述第一收发器通过高速实时串行总线与各所述自动曝光单元连接。
其中较优地，每个所述自动曝光单元具有唯一的ID，每个所述自动曝光单元的ID与对应的X射线源的ID保持一致。
其中较优地，每个所述自动曝光单元通过高速实时串行总线级联起来，以交互工作参数和检测结果。
其中较优地，每个所述自动曝光单元包括自动曝光控制模块和处理模块，所述自动曝光控制模块一方面连接所述主控单元的输出端，另一方面连接所述处理模块的输入端，所述处理模块的输出端连接所述主控单元的输入端。
其中较优地，所述自动曝光控制模块包括第一X射线探头、第二X射线探头、第一积分电路、第二积分电路、比较电路，所述第一X射线探头的输出端、所述处理模块分别连接所述第一积分电路的输入端，所述第二X射线探头的输出端、所述处理模块分别连接所述第二积分电路的输入端，所述第一积分电路的输出端分别连接所述比较电路的输入端和所述处理模块，所述比较电路的输入、输出端以及所述第二积分电路的输出端分别连接所述处理模块。
其中较优地，所述自动曝光控制模块包括第一X射线探头、第二X射线探头、第一积分电路、第二积分电路、比较电路，所述第一X射线探头的输出端与所述处理模块分别连接所述第一积分电路的输入端，所述第二X射线探头的输出端与所述处理模块分别连接所述第二积分电路的输入端，所述第二积分电路的输出端分别连接所述比较电路的输入端和所述处理模块，所述比较电路的输入、输出端以及所述第一积分电路的输出端分别连接所述处理模块。
其中较优地，所述自动曝光控制模块包括第一X射线探头、第二X射线探头、第三X射线探头、第一积分电路、第二积分电路、第三积分电路、第一减法电路、第二减法电路和比较电路；所述第一X射线探头的输出端与所述处理模块分别连接所述第一积分电路的输入端，所述第三X射线探头的输出端、所述处理模块分别连接所述第三积分电路的输入端，所述第二X射线探头的输出端、所述处理模块分别连接所述第二积分电路的输入端，所述第一积分电路的输出端分别连接所述第一减法电路的输入端和所述处理模块，所述第三积分电路的输出端分别连接所述第一减法电路、所述第二减法电路的输入端，所述第二积分电路的输出端连接所述第二减法电路的输入端，所述第一减法电路的输出端连接所述比较电路的输入端，所述比较电路的输入、输出端以及所述第一减法电路与所述第二减法电路的输出端分别连接所述处理模块。
其中较优地，所述自动曝光控制模块包括第一X射线探头、第二X射线探头、第三X射线探头、第一积分电路、第二积分电路、第三积分电路、第一减法电路、第二减法电路和比较电路；所述第一X射线探头的输出端与所述处理模块分别连接所述第一积分电路的输入端，所述第三X射线探头的输出端、所述处理模块分别连接所述第三积分电路的输入端，所述第二X射线探头的输出端、所述处理模块分别连接所述第二积分电路的输入端，所述第一积分电路的输出端分别连接所述第一减法电路的输入端和所述处理模块，所述第三积分电路的输出端分别连接所述第一减法电路、所述第二减法电路的输入端，所述第二积分电路的输出端连接所述第二减法电路的输入端，所述第二减法电路的输出端连接所述比较电路的输入端，所述比较电路的输 入、输出端以及所述第一减法电路与所述第二减法电路的输出端分别连接所述处理模块。
其中较优地，所述处理模块包括数模转换电路、所述第一模数转换电路、第二模数转换电路、处理器和第二收发器；所述数模转换电路的输入端连接所述处理器，所述数模转换电路的输出端连接所述比较电路的输入端，所述第一模数转换电路的输入端连接所述第一积分电路的输出端，所述第二模数转换电路的输入端连接所述第二积分电路的输出端，所述比较电路、所述第一模数转换电路、所述第二模数转换电路的输出端连接所述处理器，所述处理器连接所述第二收发器，所述第二收发器通过高速实时串行总线连接所述主控单元。
其中较优地，所述处理模块包括数模转换电路、所述第一模数转换电路、第二模数转换电路、处理器和第二收发器；所述数模转换电路的输入端连接所述处理器，所述数模转换电路的输出端连接所述比较电路的输入端，所述第一模数转换电路的输入端连接的所述第一减法电路的输出端，所述第二模数转换电路的输入端连接所述第二减法电路的输出端，所述比较电路、所述第一模数转换电路、所述第二模数转换电路的输出端连接所述处理器，所述处理器连接所述第二收发器，所述第二收发器通过高速实时串行总线连接所述主控单元。
根据本发明实施例的第二方面，提供一种图像校正方法，包括如下步骤：
步骤S1:获得每个X射线源初始参考像素值和当前图像参考像素值；
步骤S2:正常采集图像时，根据所述每个X射线源初始参考像素值和所述当前图像参考像素值，对获得的每个X射线源的当前图像进行校正；
步骤S3：获得每个X射线源输出的X射线的KV校正模板系数；
步骤S4：根据X射线的KV校正模板系数，对步骤S2的图像进行KV校正。
其中较优地，步骤S1包括如下子步骤：
步骤S11：针对每个所述X射线源，分别获得暗场模板和空气校正模板；
步骤S12：根据每个所述X射线源的所述空气校正模板，得到每个所述X射线源的初始参考像素值；
步骤S13：获得每个所述X射线源对应的实际投影图像，并根据每个所述X射线源对应的实际投影图像，得到每个所述X射线源的所述当前图像参考像素值。
其中较优地，在所述X射线源不发射X射线的情况下，获得每个所述X射线源暗场图像的像素的灰度值平均值，作为每个所述X射线源的所述暗场模板。
其中较优地，在确保投影区域内没有任何物体时，将获得的每个所述X射线源对应的多张投影图像的像素的灰度值取平均后，分别减去对应的X射线源的暗场模板，以作为每个所述X射线源的所述空气校正模板。
其中较优地，对每个所述X射线源的所述空气校正模板，在距离左边多个像素的那一列的所有像素的均值，和距离右边多个像素的那一列的均值，取其中较大的像素均值作为每个所述X射线源的所述初始参考像素值。
其中较优地，对每个所述X射线源对应的所述实际投影图像，在距离左边多个像素的那一列的所有像素的均值，和距离右边多个像素的那一列的均值，取其中较大的像素均值作为每个所述X射线源的所述当前图像参考像素值。
其中较优地，在正常采集图像时，将获得的每个X射线源曝光后得到的图像的每个像素，分别乘以对应的X射线源的初始参考像素值与当前图像参考像素值的比值，以得到图像整体灰度值一致的一组图像。
其中较优地，所述X射线的KV水平为X射线的第一能量累积值和第二能量累积值的比值。
其中较优地，所述X射线的KV水平做归一化处理，得到所述kV校正模板系数。
其中较优地，对图像进行KV校正时，将每个所述X射线源曝光后得到的图像的像素灰度值与对应的X射线源的空气校正模板的像素灰度值的比值，除以对应的kV校正模板系数。
本发明所提供的自动曝光控制系统及图像校正方法通过设置与X射线源数量相同的自动曝光单元，实现对各X射线源的检测，以获得X射线的能量累积值和KV水平，并且当X射线的能量累积值达到能量阈值时，向主控单元发送自动曝光控制信号，使得主控单元根据自动曝光控制信号，调整曝光时序，达到自动曝光控制的目的的同时，使X射线单次曝光输出的能量保持相对固定，优化X射线输出不稳定的问题，从而解决多个射线源的X射线影像系统中各个射线源间X射线输出不一致的问题。
附图说明
图1为本发明所提供的自动曝光控制系统的拓扑结构图；
图2为本发明所提供的自动曝光控制系统中，一种自动曝光控制模块的结构示意图1；
图3为本发明所提供的自动曝光控制系统中，一种自动曝光控制模块的结构示意图2；
图4为本发明所提供的自动曝光控制系统中，另一种自动曝光控制模块的结构示意图1；
图5为本发明所提供的自动曝光控制系统中，另一种自动曝光控制模块的结构示意图2；
图6为本发明所提供的一种图像校正方法的流程图；
图7和图8为使用本发明所提供的自动曝光控制系统和图像校正方法之前，由两个X射线探测器分别采集的两个X射线源曝光后的图像；
图9和图10为使用本发明所提供的自动曝光控制系统和图像校正方法之后，由两个X射线探测器分别采集的两个X射线源曝光后的图像。
具体实施方式
下面结合附图和具体实施例对本发明的技术内容做进一步的详细说明。
为了解决多射线源的CT系统中，多个X射线源的X射线输出能量不一致的问题，如图1所示，本发明提供了一种自动曝光控制系统，包括主控单元1和多个自动曝光单元2，主控单元1和各自动曝光单 元2连接，各自动曝光单元2之间级联，每个自动曝光单元2安装在对应的X射线源的出口处。
自动曝光单元2，用于接收主控单元1发送的曝光信号，实现对相应的X射线源进行检测，以获得X射线源输出的X射线的KV水平发送给主控单元1，同时根据预设条件，判断是否向主控单元1发送自动曝光控制信号。
所述主控单元1根据接收的自动曝光控制信号，调整曝光时序，以达到自动曝光控制的目的。
预设条件是：自动曝光单元2检测X射线源时，获得的X射线的能量累积值是否达到预先设定的X射线源输出的X射线的能量阈值。需要说明的是，每个X射线源发射的X射线的能量累积值和能量阈值以电压的形式呈现。其中，设定的每个X射线源输出的X射线的能量阈值相同，该能量阈值根据每次图像采集所需的X射线能量及保证呈现的图像趋于合适的水平进行设定。并且，通过主控单元1设定各个自动曝光单元2对应的X射线源输出的X射线的能量阈值，以控制指定X射线源自动曝光输出的X射线的能量水平。
自动曝光单元2检测X射线源时，获得的X射线的能量累积值是从X射线源开始发射X射线进行的能量累积值。
主控单元1采用包含有主控器、FPGA(Field-Programmable Gate Array,现场可编程门阵列)、第一收发器的时序控制板，该时序控制板的主控器连接第一收发器，第一收发器通过高速实时串行总线与各自动曝光单元2连接。主控单元1可以产生曝光时序，当主控单元1向高压发生器发送准备信号后，指定向一个或多个自动曝光单元2发送曝光信号，以开启自动曝光单元2，不仅实现对指定的X射线源的检测，还实现指定一个或多个X射线源进行曝光动作。其中，主控器包括但不限于FPGA(Field-Programmable Gate Array,现场可编程门阵列)或CPLD(Complex Programmable Logic Device,复杂可编程逻辑器件)，
当一个或多个自动曝光单元2对相应的X射线源进行检测的过程中，若各自动曝光单元2获得的X射线的能量累积值达到预先设定的X射线源输出的X射线的能量阈值，则向主控单元1发送自动曝光控 制信号，以使得主控单元1根据自动曝光控制信号调整曝光时序，以达到自动曝光控制的目的。具体的说，主控单元1根据自动曝光控制信号调整向相应的自动曝光单元2发送的曝光信号的宽度，以停止相应的X射线源的曝光动作。由于自动曝光控制信号为高电平，当主控单元1接收到一个或多个自动曝光单元2发送的自动曝光控制信号时，则需要将向相应的自动曝光单元2发送的曝光信号调整为低电平，使得相应的自动曝光单元2停止对X射线源的检测，此时，主控单元1还控制高压发生器停止向X射线源提供高压信号，以达到闸断相应的X射线源的X射线输出，从而实现在相同的能量阈值条件下，通过控制每个X射线源的X射线曝光时间，使多个X射线源每次投影曝光的X射线的能量趋于一致，即使X射线单次曝光输出的能量保持相对固定，以优化X射线输出不稳定的问题。
主控单元1还用于为各自动曝光单元2提供级联电源，同时负责对高速实时串行总线的控制。其中，高速实时串行总线，包括电源供电和总线信号。并且，高速实时串行总线对外接口，具有一对电源、一对地和两路差分半双工总线，形成全双工总线。并且，高速实时串行总线的四组电源和总线信号各使用一对双绞线。此外，高速实时串行总线根据系统的需要定义信息更新周期，并根据基本帧格式数据位数和可靠余量位数，定义基本波特率。例如，根据系统的需要定义信息更新周期为1us，基本帧格式数据位20位，可靠余量为5位，则基本波特率为(20+5)/1us，即25MBps。
主控单元1不仅通过高速实时串行总线实现为各自动曝光单元2提供级联电源，还通过高速实时串行总线将X射线源曝光用的曝光信号和比较用的X射线能量阈值发送给指定的自动曝光单元2。另一方面，自动曝光单元2通过高速实时串行总线将自动曝光控制信号和X射线源输出的X射线的KV水平发送给主控单元1。
每个自动曝光单元2具有唯一的ID，用于定义其地址，该ID用源ID和焦点ID进行标识，并且每个自动曝光单元2的ID与对应的X射线源的ID保持一致，以标识装配在一起的自动曝光单元2和X射线源具有相同的ID。由于不同的X射线源的源ID和焦点ID不同，因此主控单元1可以通过一路差分半双工总线向各个自动曝光单元2广播 曝光时序，即曝光信号、源ID和焦点ID信息，以指定一个或者多个X射线源进行曝光动作；由于默认状态下主控单元1及各自动曝光单元2处于接收状态，因此当指定的一个或多个自动曝光单元2工作时，各自动曝光单元2切换为发送模式将自动曝光控制信号和X射线源输出的X射线的KV水平发送给主控单元1，以便于主控单元1根据指定的X射线源对应的自动曝光单元2反馈的自动曝光控制信号，调整X射线源的曝光时序，以达到自动曝光控制的目的。
每个自动曝光单元2通过高速实时串行总线级联起来，以交互工作参数和检测结果，并有利于系统的可靠性和工程化。各自动曝光单元2装配在X射线源的出口处，没有其它被测物造成的X射线散射的影像，使得检测结果更准确。如图2～图4所示，每个自动曝光单元2包括自动曝光控制模块21和处理模块22，自动曝光控制模块21一方面连接主控单元1的输出端，另一方面连接处理模块22的输入端，处理模块22的输出端连接主控单元1的输入端。
当主控单元1向高压发生器发送准备信号后，指定向一个或多个自动曝光单元2的自动曝光控制模块21发送曝光信号，以开启自动曝光控制模块21，实现对指定的X射线源的检测，并将实时获得的X射线的能量累积值输出到处理模块22，以得到每个X射线源输出的X射线的KV水平并发送给主控单元1。同时，若自动曝光控制模块21对X射线源进行检测时获得的X射线的能量累积值达到预先设定的X射线的能量阈值，则通过处理模块22向主控单元1发送自动曝光控制信号，以使得主控单元1根据自动曝光控制信号调整曝光时序，以达到自动曝光控制的目的。
如图2所示，在本发明的一个实施例中，自动曝光控制模块21包括第一X射线探头210、第二X射线探头211、第一积分电路212、第二积分电路213、比较电路214；该自动曝光控制模块21各部分可以是以下两种连接关系，第一种连接关系为：第一X射线探头210的输出端、处理模块22分别连接第一积分电路212的输入端，第二X射线探头211的输出端、处理模块22分别连接第二积分电路213的输入端，第一积分电路212的输出端分别连接比较电路214的输入端和处理模块22，比较电路214的输入、输出端以及第二积分电路213的输出端 分别连接处理模块22。
如图3所示，自动曝光控制模块21各部分第二种连接关系为：第一X射线探头210的输出端与处理模块22分别连接第一积分电路212的输入端，第二X射线探头211的输出端与处理模块22分别连接第二积分电路213的输入端，第二积分电路213的输出端分别连接比较电路214的输入端和处理模块22，比较电路214的输入、输出端以及第一积分电路212的输出端分别连接处理模块22。
本实施例的自动曝光控制模块21的两种连接关系的工作原理相同，只不过在实现对X射线源自动曝光控制的过程中，可以选择将第一积分电路212获得的X射线的第一能量累积值I 0或第二积分电路212获得的X射线的第二能量累积值I输出到比较电路214，以判断X射线的第一能量累积值或X射线的第二能量累积值I是否达到预先设定的X射线的能量阈值，从而确定是否向主控单元1发送自动曝光控制信号，使得主控单元调整曝光时序，以达到自动曝光控制的目的。下面以第一积分电路212获得的X射线的第一能量累积值I 0输出到比较电路214为例，对该实施例所提供的自动曝光控制模块21的工作原理进行详细说明。
如图2所示，通过主控单元1设定各个自动曝光单元2对应的X射线源输出的X射线的能量阈值，并将该能量阈值通过处理模块22传输到比较电路214中，当高压发生器已做好准备向X射线管发射高压后，主控单元1向第一积分电路212与第二积分电路213发送曝光信号(如图2所示的Spot信号)，以开启第一积分电路212与第二积分电路213，第一X射线探头210与第二X射线探头211从X射线源发射x射线开始进行检测，以对应持续获得第一X射线电流和第二X射线电流，并将第一X射线电流和第二X射线电流对应输出到第一积分电路212与第二积分电路213中，实现对X射线的能量累积；第一积分电路212获得的X射线的第一能量累积值I 0以及第二积分电路212获得的X射线的第二能量累积值I，分别输出到处理模块22，以得到指定的X射线源的输出的X射线的KV水平。
其中，第一积分电路212获得的X射线的第一能量累积值I 0还输出到比较电路214中，比较电路214将该X射线的第一能量累积值I 0与X射线的能量阈值进行比较，若X射线的第一能量累积值达到预先设定的X射线的能量阈值，则通过处理模块22向主控单元1发送自动曝光控制信号(如图2所示的AECSpot信号)，使得主控单元1控制高压发生器停止向X射线源提供高压，以闸断相应的X射线源的X射线输出；同时，主控单元1还会根据自动曝光控制信号，调整向第一积分电路212、第二积分电路213发送的曝光信号的宽度，即关闭向第一积分电路212、第二积分电路213发送的曝光信号，使得第一积分电路212、第二积分电路213保持清零状态，从而实现停止相应的X射线源的曝光动作。
需求说明的是，由于X射线源发射的X射线在物质中的传输遵循衰减规律，因此基于改变X射线源到探头之间的吸收材料的厚度，以检测出不同的X射线强度(X射线的能量累积值)。在本发明实施例中，通过将X射线源分别到第一X射线探头210、第二X射线探头211之间的吸收材料设置不同的厚度，以获得X射线的第一能量累积值I 0和第二能量累积值I。本实施例的自动曝光控制模块21在对X射线源进行检测时，X射线源没有发射X射线时第一X射线探头210与第二X射线探头211也会有本底电流，由于本底电流比较小，对最终获得的X射线的第一能量累积值I 0和第二能量累积值I的影响不大，因此可以忽略对没有X射线输出的情况下的本底检测。
如图4所示，在本发明的另一个实施例中，自动曝光控制模块21包括第一X射线探头210、第二X射线探头211、第三X射线探头215、第一积分电路212、第二积分电路213、第三积分电路216、第一减法电路217、第二减法电路218和比较电路214；该自动曝光控制模块21各部分可以是以下两种连接关系，
第一种连接关系为：第一X射线探头210的输出端与处理模块22分别连接第一积分电路212的输入端，第三X射线探头215的输出端、处理模块22分别连接第三积分电路216的输入端，第二X射线探头 211的输出端、处理模块22分别连接第二积分电路213的输入端，第一积分电路212的输出端分别连接第一减法电路217的输入端和处理模块22，第三积分电路216的输出端分别连接第一减法电路217、第二减法电路218的输入端，第二积分电路213的输出端连接第二减法电路218的输入端，第一减法电路217的输出端连接比较电路214的输入端，比较电路214的输入、输出端以及第一减法电路217与第二减法电路218的输出端分别连接处理模块22。
如图5所示，自动曝光控制模块21各部分第二种连接关系为：第一X射线探头210的输出端与处理模块22分别连接第一积分电路212的输入端，第三X射线探头215的输出端、处理模块22分别连接第三积分电路216的输入端，第二X射线探头211的输出端、处理模块22分别连接第二积分电路213的输入端，第一积分电路212的输出端分别连接第一减法电路217的输入端和处理模块22，第三积分电路216的输出端分别连接第一减法电路217、第二减法电路218的输入端，第二积分电路213的输出端连接第二减法电路218的输入端，第二减法电路218的输出端连接比较电路214的输入端，比较电路214的输入、输出端以及第一减法电路217与第二减法电路218的输出端分别连接处理模块22。
本实施例的自动曝光控制模块21的工作原理与上面实施例的自动曝光控制模块21的不同之处在于：本实施例的自动曝光控制模块21在对X射线源进行检测时，考虑到X射线源没有发射X射线时第一X射线探头210与第二X射线探头211也会有本底电流，因此本实施例的自动曝光控制模块21通过对第三X射线探头215进行完全避光处理，实现获得X射线源没有发射X射线时输出的本底电流，并将该本底电流输出到第三积分电路216，得到X射线的本底能量累积值K，该本底能量累积值K分别输出到第一减法电路217与第二减法电路218中，以便于第一减法电路217将接收的第一积分电路212获得的包含有X射线的本底能量第一能量累积值减去本底能量累积值K后，得到X射线的第一能量累积值I 0；同样，第二减法电路218将接收的第二积分电路213获得的包含有X射线的本底能量第二能量累积值减去本底能量累积值K后，得到X射线的第二能量累积值I。
以第一减法电路217获得的X射线的第一能量累积值I 0输出到比较电路214为例，比较电路214将收到的X射线的第一能量累积值I 0与X射线的能量阈值进行比较，若X射线的第一能量累积值达到预先设定的X射线的能量阈值，则通过处理模块22向主控单元1发送自动曝光控制信号，使得主控单元1控制高压发生器停止向X射线源提供高压，以闸断相应的X射线源的X射线输出；同时，主控单元1还会根据自动曝光控制信号，调整向第一积分电路212、第二积分电路213发送的曝光信号的宽度，即关闭向第一积分电路212、第二积分电路213发送的曝光信号，使得第一积分电路212、第二积分电路213保持清零状态，从而实现停止相应的X射线源的曝光动作。
如图2～图5所示，处理模块22包括数模转换电路220、第一模数转换电路221、第二模数转换电路222、处理器223和第二收发器；其中，处理器223包括但不限于FPGA(Field-Programmable Gate Array,现场可编程门阵列)、CPLD(Complex Programmable Logic Device,复杂可编程逻辑器件)。下面以处理器223采用FPGA为例，对处理模块2各部分之间的连接关系进行说明。
根据自动曝光控制模块21的两种结构，处理模块22各部分具有两种连接关系；如图2和图3所示，当采用第一种自动曝光控制模块21时，处理模块22各部分的连接关系为：数模转换电路220的输入端连接FPGA223，数模转换电路220的输出端连接比较电路214的输入端，第一模数转换电路221的输入端连接自动曝光控制模块21的第一积分电路212的输出端，第二模数转换电路222的输入端连接自动曝光控制模块21的第二积分电路212的输出端，比较电路214、第一模数转换电路221、第二模数转换电路222的输出端连接FPGA223，FPGA223连接第二收发器，第二收发器通过高速实时串行总线连接主控单元1的第一收发器。
如图4和图5所示，当采用第二种自动曝光控制模块21时，处理模块22各部分的连接关系为：数模转换电路220的输入端连接FPGA223，数模转换电路220的输出端连接比较电路214的输入端，第一模数转换电路221的输入端连接的第一减法电路217的输出端，第 二模数转换电路222的输入端连接第二减法电路218的输出端，比较电路214、第一模数转换电路221、第二模数转换电路222的输出端连接FPGA223，FPGA223连接第二收发器，第二收发器通过高速实时串行总线连接主控单元1的第一收发器。
处理模块22的工作原理为：通过主控单元1设定各个自动曝光单元2对应的X射线源输出的X射线的能量阈值，并将该能量阈值通过第二收发器发送至FPGA223中，FPGA223将能量阈值发送至数模转换电路220转换成模拟电压后，发送至比较电路214中；自动曝光控制模块21对X射线源检测，获得的第一能量累积值c和第二能量累积值I对应经过第一模数转换电路221和第二模数转换电路222转换成数字信号后，发送至FPGA223中，FPGA223将第一能量累积值I 0和第二能量累积值I进行相除，得到I/I 0即为X射线源的输出的X射线的KV水平，并通过第二收发器上传至主控单元1。FPGA223还用于接收自动曝光控制信号，并通过第二收发器上传至主控单元1，以使得主控单元1根据自动曝光控制信号调整曝光时序，以达到自动曝光控制的目的。
综上所述，本发明所提供的自动曝光控制系统通过设置与X射线源数量相同的自动曝光单元，实现对各X射线源的检测，以获得X射线的能量累积值和KV水平，并且当X射线的能量累积值达到能量阈值时，向主控单元发送自动曝光控制信号，使得主控单元根据自动曝光控制信号，调整曝光时序，达到自动曝光控制的目的的同时，使X射线单次曝光输出的能量保持相对固定，优化X射线输出不稳定的问题，从而解决多个射线源的X射线影像系统中各个射线源间X射线输出不一致的问题。
经过本自动曝光控制系统后，多个X射线源的X射线输出不一致的问题得到了很大改善，X射线的能量输出也基本稳定。不过，多个X射线源的能量输出不一致性仍然有较小的差别，即使是单个X射线源的多次曝光，输出能量也不是完全一致。表现是不同X射线源曝光的影像或单个射线源的多个曝光影像灰度值有一定的差别，大约是1％左右，对于16位的影像，大约有500左右的差别。这一差别在重建图像 后会影响图像的均匀性，进而影响图像的密度分辨率。因此本发明还提供了一种图像校正方法，用于进一步改善每个X射线源曝光后，得到的图像亮度不一致的问题。如图6所示，该图像校正方法包括如下步骤：
步骤S1:获得每个X射线源初始参考像素值和当前图像参考像素值。
该步骤包括如下子步骤：
步骤S11：针对每个X射线源，分别获得暗场模板和空气校正模板。
在X射线源不发射X射线的情况下，分别为每个X射线源采集多张(如≥20张)暗场图像，并将每个X射线源的多张暗场图像的像素的灰度值取平均，得到每个X射线源暗场图像的像素的灰度值平均值，并进行保存，以作为每个X射线源的暗场模板。
在确保投影区域内没有任何物体时，设定X射线发射条件为应用需要的条件，获得每个X射线源的多张(如≥20张)投影图像，将每个X射线源对应的多张投影图像的像素的灰度值取平均，得到每个X射线源投影图像的像素的灰度值平均值，此时，将每个X射线源投影图像的像素的灰度值平均值分别减去对应的X射线源的暗场模板后，进行保存，以作为每个X射线源的空气校正模板。
步骤S12：根据每个X射线源的空气校正模板，得到每个X射线源初始参考像素值。
对每个X射线源的空气校正模板，在距离左边多个(如10个)像素的那一列的所有像素的均值，和距离右边多个(如10个)像素的那一列的均值，取其中较大的像素均值作为每个X射线源初始参考像素值。
步骤S13：获得每个X射线源对应的实际投影图像，并根据每个X射线源对应的实际投影图像，得到每个X射线源的当前图像参考像素值。
将被测物放到投影区域，分别获取每个X射线源对应的投影图像，并将每个X射线源的投影图像的像素的灰度值分别减去对应的X射线源的暗场模板，得到每个X射线源对应的实际投影图像。
对每个X射线源对应的实际投影图像，在距离左边多个(如10个)像素的那一列的所有像素的均值，和距离右边多个(如10个)像素的那一列的均值，取其中较大的像素均值作为每个X射线源的当前图像参考像素值。
步骤S2:正常采集图像时，根据每个X射线源初始参考像素值和当前图像参考像素值，对获得的每个X射线源的当前图像进行校正。
在正常采集图像时，将获得的每个X射线源曝光后得到的图像的每个像素，分别乘以对应的X射线源初始参考像素值与当前图像参考像素值的比值，以得到图像整体灰度值基本一致的一组图像，有效抑制X射线输出不稳定对图像处理的影响，从而解决多个射线源的X射线影像系统中各个射线源间X射线输出不一致的问题。
如图7和图8所示，使用本自动曝光控制系统和图像校正方法之前，由两个X射线探测器分别采集两个X射线源曝光后的图像，图7为采用第一个X射线探测器采集的X射线源曝光后的图像，该图像的灰度均值Mean为20446.68，图8为采用第二个X射线探测器采集的X射线源曝光后的图像，该图像的灰度均值Mean为20951.46，两个X射线源的图像之间的灰度值相差504.78。
同样，使用本自动曝光控制系统和图像校正方法之后，由两个X射线探测器分别采集上述两个X射线源曝光后的图像，图9为采用第一个X射线探测器采集的X射线源曝光后的图像，该图像的灰度均值Mean为20734.22，相对于图7的图像整体亮度有少许提升；图10为采用第二个X射线探测器采集的X射线源曝光后的图像，该图像的灰度均值Mean为20788.42，相对于图2的图像的整体亮度少许降低两个X射线源的图像之间的灰度值相差54.2。不难发现，两个X射线源的图像之间的灰度差别降低很多；因此使用本图像校正方法后，有利于改善每个X射线源曝光后，得到的图像亮度不一致的问题。
步骤S3：获得每个X射线源输出的X射线的KV校正模板系数。
通过本自动曝光控制系统的自动曝光单元2实现对每个X射线源进行检测，以获得每个X射线源输出的X射线的KV水平，对各个X射线源输出的X射线的kV水平做归一化处理，从而得到kV校正模板系数。
获得每个X射线源输出的X射线的KV水平的过程为：通过自动曝光单元2对X射线源进行检测，分别获得X射线的第一能量累积值I 0和第二能量累积值I，将X射线的第一能量累积值I 0和第二能量累积值I进行相除，得到I/I 0，即为X射线源的输出的X射线的KV水平。自动曝光单元2获得X射线的第一能量累积值I 0和第二能量累积值I的具体实现过程同上。
步骤S4：根据X射线的KV校正模板系数，对步骤S2的图像进行KV校正。
本自动曝光控制系统实现对每个X射线源进行检测，并将获得的每个X射线源输出的X射线的KV水平，发送到工控机上，以便于工控机对各个X射线源输出的X射线的KV水平做归一化处理，得到kV校正模板系数后，根据X射线的KV校正模板系数和空气校正模板，在正常采集图像时，对X射线图像探测器发送的X射线源曝光后得到的图像的进行KV校正。具体的说，正常采集图像时，将每个X射线源曝光后得到的图像的像素灰度值与对应的X射线源的空气校正模板的像素灰度值的比值，除以对应的kV校正模板系数，实现对X射线源曝光后得到的图像的进行KV校正，以提高图像重建精度。
以上对本发明所提供的自动曝光控制系统及图像校正方法进行了详细的说明。对本领域的一般技术人员而言，在不背离本发明实质内容的前提下对它所做的任何显而易见的改动，都将落入本发明专利权的保护范围。

Claims (22)

  1. 一种自动曝光控制系统，其特征在于包括主控单元和多个自动曝光单元，所述主控单元和各所述自动曝光单元连接，各所述自动曝光单元之间级联，每个所述自动曝光单元安装在对应的X射线源的出口处；
    所述自动曝光单元，用于接收所述主控单元发送的曝光信号，以对相应的X射线源进行检测，获得所述X射线源输出的X射线的KV水平，同时根据预设条件，判断是否向所述主控单元发送自动曝光控制信号；
    所述主控单元根据接收所述自动曝光控制信号，调整曝光时序，以达到自动曝光控制的目的。
  2. 如权利要求1所述的自动曝光控制系统，其特征在于：
    所述预设条件是：所述自动曝光单元检测所述X射线源时，获得的X射线的能量累积值是否达到预先设定的所述X射线源输出的X射线的能量阈值。
  3. 如权利要求1所述的自动曝光控制系统，其特征在于：
    所述主控单元采用包含有主控器、第一收发器的时序控制板，所述主控器连接所述第一收发器，所述第一收发器通过高速实时串行总线与各所述自动曝光单元连接。
  4. 如权利要求1所述的自动曝光控制系统，其特征在于：
    每个所述自动曝光单元具有唯一的ID，每个所述自动曝光单元的ID与对应的X射线源的ID保持一致。
  5. 如权利要求1所述的自动曝光控制系统，其特征在于：
    每个所述自动曝光单元通过高速实时串行总线级联起来，以交互工作参数和检测结果。
  6. 如权利要求1所述的自动曝光控制系统，其特征在于：
    每个所述自动曝光单元包括自动曝光控制模块和处理模块，所述自动曝光控制模块一方面连接所述主控单元的输出端，另一方面连接所述处理模块的输入端，所述处理模块的输出端连接所述主控单元的输入端。
  7. 如权利要求6所述的自动曝光控制系统，其特征在于：
    所述自动曝光控制模块包括第一X射线探头、第二X射线探头、第一积分电路、第二积分电路、比较电路，所述第一X射线探头的输出端、所述处理模块分别连接所述第一积分电路的输入端，所述第二X射线探头的输出端、所述处理模块分别连接所述第二积分电路的输入端，所述第一积分电路的输出端分别连接所述比较电路的输入端和所述处理模块，所述比较电路的输入、输出端以及所述第二积分电路的输出端分别连接所述处理模块。
  8. 如权利要求6所述的自动曝光控制系统，其特征在于：
    所述自动曝光控制模块包括第一X射线探头、第二X射线探头、第一积分电路、第二积分电路、比较电路，所述第一X射线探头的输出端与所述处理模块分别连接所述第一积分电路的输入端，所述第二X射线探头的输出端与所述处理模块分别连接所述第二积分电路的输入端，所述第二积分电路的输出端分别连接所述比较电路的输入端和所述处理模块，所述比较电路的输入、输出端以及所述第一积分电路的输出端分别连接所述处理模块。
  9. 如权利要求6所述的自动曝光控制系统，其特征在于：
    所述自动曝光控制模块包括第一X射线探头、第二X射线探头、第三X射线探头、第一积分电路、第二积分电路、第三积分电路、第一减法电路、第二减法电路和比较电路；所述第一X射线探头的输出端与所述处理模块分别连接所述第一积分电路的输入端，所述第三X射线探头的输出端、所述处理模块分别连接所述第三积分电路的输入端，所述第二X射线探头的输出端、所述处理模块分别连接所述第二积分电路的输入端，所述第一积分电路的输出端分别连接所述第一减法电路的输入端和所述处理模块，所述第三积分电路的输出端分别连接所述第一减法电路、所述第二减法电路的输入端，所述第二积分电路的输出端连接所述第二减法电路的输入端，所述第一减法电路的输出端连接所述比较电路的输入端，所述比较电路的输入、输出端以及所述第一减法电路与所述第二减法电路的输出端分别连接所述处理模块。
  10. 如权利要求6所述的自动曝光控制系统，其特征在于：
    所述自动曝光控制模块包括第一X射线探头、第二X射线探头、第三X射线探头、第一积分电路、第二积分电路、第三积分电路、第一减法电路、第二减法电路和比较电路；所述第一X射线探头的输出端与所述处理模块分别连接所述第一积分电路的输入端，所述第三X射线探头的输出端、所述处理模块分别连接所述第三积分电路的输入端，所述第二X射线探头的输出端、所述处理模块分别连接所述第二积分电路的输入端，所述第一积分电路的输出端分别连接所述第一减法电路的输入端和所述处理模块，所述第三积分电路的输出端分别连接所述第一减法电路、所述第二减法电路的输入端，所述第二积分电路的输出端连接所述第二减法电路的输入端，所述第二减法电路的输出端连接所述比较电路的输入端，所述比较电路的输入、输出端以及所述第一减法电路与所述第二减法电路的输出端分别连接所述处理模块。
  11. 如权利要求7或8所述的自动曝光控制系统，其特征在于：
    所述处理模块包括数模转换电路、所述第一模数转换电路、第二模数转换电路、处理器和第二收发器；所述数模转换电路的输入端连接所述处理器，所述数模转换电路的输出端连接所述比较电路的输入端，所述第一模数转换电路的输入端连接所述第一积分电路的输出端，所述第二模数转换电路的输入端连接所述第二积分电路的输出端，所述比较电路、所述第一模数转换电路、所述第二模数转换电路的输出端连接所述处理器，所述处理器连接所述第二收发器，所述第二收发器通过高速实时串行总线连接所述主控单元。
  12. 如权利要求9或10所述的自动曝光控制系统，其特征在于：
    所述处理模块包括数模转换电路、所述第一模数转换电路、第二模数转换电路、处理器和第二收发器；所述数模转换电路的输入端连接所述处理器，所述数模转换电路的输出端连接所述比较电路的输入端，所述第一模数转换电路的输入端连接的所述第一减法电路的输出端，所述第二模数转换电路的输入端连接所述第二减法电路的输出端，所述比较电路、所述第一模数转换电路、所述第二模数转换电路的输出端连接所述处理器，所述处理器连接所述第二收发器，所述第二收发器通过高速实时串行总线连接所述主控单元。
  13. 一种图像校正方法，其特征在于包括如下步骤：
    步骤S1:获得每个X射线源初始参考像素值和当前图像参考像素值；
    步骤S2:正常采集图像时，根据所述每个X射线源初始参考像素值和所述当前图像参考像素值，对获得的每个X射线源的当前图像进行校正；
    步骤S3：获得每个X射线源输出的X射线的KV校正模板系数；
    步骤S4：根据X射线的KV校正模板系数，对步骤S2的图像进行KV校正。
  14. 如权利要求13所述的图像校正方法，其特征在于步骤S1包括如下子步骤：
    步骤S11：针对每个所述X射线源，分别获得暗场模板和空气校正模板；
    步骤S12：根据每个所述X射线源的所述空气校正模板，得到每个所述X射线源的初始参考像素值；
    步骤S13：获得每个所述X射线源对应的实际投影图像，并根据每个所述X射线源对应的实际投影图像，得到每个所述X射线源的所述当前图像参考像素值。
  15. 如权利要求14所述的图像校正方法，其特征在于：
    在所述X射线源不发射X射线的情况下，获得每个所述X射线源暗场图像的像素的灰度值平均值，作为每个所述X射线源的所述暗场模板。
  16. 如权利要求14所述的图像校正方法，其特征在于：
    在确保投影区域内没有任何物体时，将获得的每个所述X射线源对应的多张投影图像的像素的灰度值取平均后，分别减去对应的X射线源的暗场模板，以作为每个所述X射线源的所述空气校正模板。
  17. 如权利要求14所述的图像校正方法，其特征在于：
    对每个所述X射线源的所述空气校正模板，在距离左边多个像素的那一列的所有像素的均值，和距离右边多个像素的那一列的均值，取其中较大的像素均值作为每个所述X射线源的所述初始参考像素值。
  18. 如权利要求14所述的图像校正方法，其特征在于：
    对每个所述X射线源对应的所述实际投影图像，在距离左边多个像素的那一列的所有像素的均值，和距离右边多个像素的那一列的均值，取其中较大的像素均值作为每个所述X射线源的所述当前图像参考像素值。
  19. 如权利要求14所述的图像校正方法，其特征在于：
    在正常采集图像时，将获得的每个X射线源曝光后得到的图像的每个像素，分别乘以对应的X射线源的初始参考像素值与当前图像参考像素值的比值，以得到图像整体灰度值一致的一组图像。
  20. 如权利要求1或14所述的图像校正方法，其特征在于：
    所述X射线的KV水平为X射线的第一能量累积值和第二能量累积值的比值。
  21. 如权利要求20所述的图像校正方法，其特征在于：
    所述X射线的KV水平做归一化处理，得到所述kV校正模板系数。
  22. 如权利要求21所述的图像校正方法，其特征在于：
    对图像进行KV校正时，将每个所述X射线源曝光后得到的图像的像素灰度值与对应的X射线源的空气校正模板的像素灰度值的比值，除以对应的kV校正模板系数。
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