JP2014090863A - Radiation image capturing system and automatic exposure control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform an appropriate automatic exposure control even when a communication delay occurs in a radiocommunication section between a radiation image capturing apparatus and an interface device.SOLUTION: An electronic cassette 1 detects applied radiation to capture a radiation image, and intermittently, wirelessly transmits dose information representing a dose of the detected radiation to an interface box 220. The interface box 220 generates a cumulative dose signal having a signal level according to the cumulative dose of the radiation applied to the electronic cassette 1 on the basis of each of the received dose information, and when determining that there is a delay in reception timing of the dose information, adjusts the signal level of the cumulative dose signal so as to reduce an error generated in the cumulative dose signal caused by the delay.

Description

  The present invention relates to a radiographic imaging system including a radiographic imaging apparatus that captures a radiographic image indicated by radiation transmitted through a subject, and an automatic exposure control method in the radiographic imaging system.

  In recent years, radiation detectors (FPD: Flat Panel Detector) have been put into practical use, which arrange radiation sensitive layers on TFT (Thin Film Transistor) active matrix substrates and generate digital data corresponding to the radiation dose. A radiographic imaging apparatus (hereinafter also simply referred to as an imaging apparatus) such as an electronic cassette that captures a radiographic image represented by radiation irradiated using the radiation detector has been put into practical use. Radiation detectors convert radiation into electrical signals, such as an indirect conversion method in which radiation is converted to light with a scintillator and then converted into charges with a photodiode, or radiation is converted into charges with a semiconductor layer containing amorphous selenium, etc. There are various materials that can be used for the semiconductor layer in each method.

  In recent years, there has been proposed a radiographic imaging system that performs wireless communication between a radiation generation apparatus and an imaging apparatus equipped with an FPD. If wireless communication can be performed between the radiation generating apparatus and an imaging apparatus such as an electronic cassette, the portability of the imaging apparatus can be improved and the system can be flexibly constructed.

  For example, in Patent Document 1, a radiation generating apparatus having a radiation irradiating unit that irradiates a subject with radiation and a detection element that converts the radiation irradiated from the radiation irradiating unit into a charge signal and accumulates them in a two-dimensional form. The arranged radiological image detection unit, the irradiation detection unit that detects the start of radiation irradiation, the imaging control unit that controls the operation state of the radiological image detection unit, and the radio that performs communication between the radiation generator and the imaging control unit And a radiation imaging system having communication means. In this radiation imaging system, the imaging control means does not receive the radiation irradiation start control signal from the radiation generator by the wireless communication means, and the radiation image detection unit detects the radiation irradiation start by the irradiation detection means. The detection element is shifted from the charge sweeping state to the charge accumulation state.

  Patent Document 2 discloses a radiographic imaging system that includes an X-ray generator and an imaging device including a radiation detector, and performs communication between them by radio. In this radiographic imaging system, the X-ray generator transmits an irradiation permission request signal to the imaging apparatus through a wireless communication path when a trigger is input, and the imaging apparatus receives an irradiation permission request signal and then receives an image of the radiation detector. It is described that an irradiation permission signal is sent back through a wireless communication path when the irradiation becomes possible, and the X-ray generator starts X-ray irradiation upon reception of the irradiation permission signal.

  On the other hand, when a radiographic image is captured by an imaging apparatus having a radiation detector, it is necessary to ensure good image quality while minimizing the dose of radiation applied to the subject. In order to acquire a radiographic image with good image quality, it is necessary to set radiation exposure conditions so that an appropriate dose of radiation according to the region to be imaged is emitted. Therefore, automatic exposure control (AEC) that detects the dose of radiation that has passed through the subject in an imaging device that has a radiation detector and controls the timing of stopping radiation from the radiation source based on the detection result. : Radiographic imaging system with Automatic Exposure Control) function has been proposed. In order to realize this automatic exposure control (AEC), a device in which a pixel for detecting a dose of radiation irradiated separately from a pixel for capturing a radiation image is embedded in a radiation detector has been proposed.

  For example, Patent Document 3 discloses a signal in which a plurality of pixels including a radiation image capturing pixel and a radiation detection pixel are arranged in a matrix in a detection region for detecting radiation and connected to the radiation detection pixel. A radiographic imaging apparatus that detects a dose of radiation irradiated by detecting electric charges flowing through wiring is described.

JP 2008-132216 A JP 2006-333898 A JP 2012-15913 A

  In a radiographic imaging system provided with a wireless communication means for performing wireless communication between a radiation generating apparatus and an imaging apparatus, it is considered that automatic exposure control (AEC) can be performed by wireless communication. The following can be considered as a configuration for realizing automatic exposure control (AEC) by wireless communication. That is, in an imaging apparatus such as an electronic cassette having a radiation detector, the radiation dose emitted from the radiation generator is detected, and dose information indicating the detected radiation dose is transmitted wirelessly. Such dose information is transmitted intermittently at a constant cycle, for example. Dose information transmitted from the imaging device is received by an interface device connected to the radiation generator. The interface device is an interface device that is interposed between an imaging apparatus such as an electronic cassette and a radiation generation apparatus, and converts dose information supplied from the imaging apparatus into a signal that can be recognized on the radiation generation apparatus side. The interface device generates a cumulative dose signal indicating the cumulative dose of radiation applied to the imaging device based on the received dose information, and supplies this to the radiation generator. When the radiation generation apparatus detects that the signal level of the accumulated dose signal supplied from the interface apparatus has reached a predetermined value, the radiation generation apparatus stops radiation irradiation.

  In the radiographic imaging system having such a configuration, a communication delay in the wireless communication section between the imaging apparatus and the interface apparatus becomes a problem. That is, when a communication delay occurs due to interference or the like in the wireless communication section, dose information transmitted from the imaging apparatus is received with a delay in the interface apparatus. When the dose information is delayed in reception timing, the accumulated dose cannot be accurately calculated in the interface device. As a result, the radiation stop timing in the radiation generator becomes inappropriate, and an excessive dose of radiation is exposed to the subject, or an appropriate radiographic image can be acquired due to a lack of dose. Disappear.

  The present invention has been made in view of the above points, and is automatically performed by wirelessly transmitting dose information indicating the dose of radiation irradiated to itself by the radiographic imaging device to an interface device that controls the radiation generator. In an aspect of performing exposure control (AEC), a radiographic imaging system capable of performing appropriate automatic exposure control (AEC) even when a communication delay occurs in a wireless communication section between the radiographic imaging device and the interface device, and The purpose is to provide a program.

  In order to achieve the above object, a radiographic imaging system according to the present invention captures a radiographic image by detecting irradiated radiation and wirelessly transmits dose information indicating the detected radiation dose at each predetermined transmission timing. A radiological image capturing device to be transmitted, and dose information wirelessly transmitted from the radiographic image capturing device, and a cumulative dose indicating a cumulative dose of radiation irradiated to the radiographic image capturing device based on each of the received dose information An interface device that generates a signal and adjusts the cumulative dose signal so as to reduce an error that occurs in the cumulative dose signal due to a delay in the reception timing of the dose information with respect to a transmission timing of the dose information.

  That is, the radiographic imaging device according to the present invention intermittently wirelessly transmits dose information indicating the detected dose of radiation toward the interface device. The interface device generates a cumulative dose signal indicating the cumulative dose of radiation irradiated to the radiographic imaging device based on each received dose information. Here, when a communication delay occurs due to interference or the like in the wireless communication section between the radiographic imaging device and the interface device due to interference or the like, there is a delay in the reception timing of dose information in the interface device. If it occurs, an error will occur in the accumulated dose signal. The interface apparatus according to the present invention adjusts the accumulated dose signal so as to reduce an error generated in the accumulated dose signal due to a delay in dose information reception timing. Therefore, even when a delay occurs in the reception timing of dose information, the signal level of the accumulated dose signal is maintained in an appropriate state.

  The radiographic imaging apparatus may wirelessly transmit the dose information at a predetermined transmission cycle. In this case, the interface apparatus may determine a delay in the reception timing of the dose information by comparing a transmission period of the dose information in the radiographic imaging apparatus and a reception interval of the dose information.

  Further, the interface device may be configured such that the interval between the reception time of the dose information received at the mth time and the reception time of the dose information received at the nth time after the mth time is (n− If it is longer than m) times, it may be determined that there is a delay in the reception timing of the dose information received at the nth time.

  Further, the interface device may be configured such that the interval between the reception time of the dose information received at the mth time and the reception time of the dose information received at the nth time after the mth time is (n− If it is shorter than m) times, it may be determined that there is a delay in the reception timing of the dose information received for the mth time.

  The radiographic imaging device transmits transmission cycle information indicating a transmission cycle of the dose information to the interface device, and the interface device transmits the transmission cycle of the dose information indicated by the received transmission cycle information and the The dose information reception interval may be compared to determine the delay of the dose information reception timing.

  The interface device may include a recording unit that records a reception time of each of the dose information, and may derive a dose information reception interval based on the reception time recorded by the recording unit.

  The recording means may attach time information indicating the reception time of each dose information to the dose information. That is, the recording means may add the reception time of the dose information to the dose in a so-called time stamp format.

  Further, the interface device controls the inclination of the cumulative dose signal based on each of the received dose information, and determines that the delay occurs in the reception timing of the dose information, the delay device Control means for controlling the slope of the cumulative dose signal so as to reduce an error generated in the cumulative dose signal may be included.

  When the control means determines that there is a delay in the reception timing of the dose information, the reception time of the dose information received with the delay is determined as having no delay. It is also possible to derive an estimation line that estimates the time transition of the cumulative dose signal in the case of shifting to, and to control the slope of the cumulative dose signal so that the cumulative dose signal matches the estimation line.

  In addition, the control means, when the signal level of the cumulative dose signal is excessive due to a delay in the reception timing of the dose information, by changing the signal level of the cumulative dose signal constant, The signal level may be matched to the estimated line.

  In addition, the radiographic imaging system according to the present invention further includes a radiation generator that stops radiation irradiation to the radiographic imaging device when it is detected that the signal level of the cumulative dose signal has reached a predetermined value. May be.

  In order to achieve the above object, the automatic exposure control method according to the present invention provides a radiographic imaging apparatus that detects radiation applied to itself and detects dose information indicating the radiation dose detected at a predetermined transmission timing. A step of wirelessly transmitting each time, and the interface device receives the dose information wirelessly transmitted from the radiographic imaging device, and the cumulative dose of radiation irradiated to the radiographic imaging device based on each of the received dose information And a radiation generator that emits radiation to the radiographic imaging device when the radiation generator detects that the signal level of the cumulative dose signal output from the interface device has reached a predetermined value. And an automatic exposure control method in a radiographic imaging system, comprising the step of: Scan device, and adjusts the cumulative dose signal so as to reduce the error generated in the accumulated dose signals by the delay of the reception timing of the dose information to the transmission timing of the dose information.

  According to the present invention, in a mode in which automatic exposure control (AEC) is performed by wirelessly transmitting dose information indicating a dose of radiation irradiated to the radiographic imaging device to an interface device that controls the radiation generation device. Appropriate automatic exposure control (AEC) can be performed even when a communication delay occurs in the wireless communication section between the radiographic imaging apparatus and the interface apparatus.

It is a block diagram which shows the structure of the radiation information system which concerns on embodiment of this invention. It is a side view which shows an example of the arrangement | positioning state of each apparatus in the radiography room of the radiographic imaging system which concerns on embodiment of this invention. It is a perspective view which shows the structure of the electronic cassette concerning embodiment of this invention. It is sectional drawing which shows schematic structure of the radiation detector which concerns on embodiment of this invention. It is a figure which shows the electrical structure of the radiation detector which concerns on embodiment of this invention. It is a top view which illustrated arrangement on a radiation detector of a pixel for dose detection concerning an embodiment of the present invention. It is a figure which shows the principal part structure of the electrical system of the imaging | photography system which concerns on this Embodiment. It is a block diagram which shows the structure of the signal processing part which concerns on embodiment of this invention. It is a flowchart which shows the flow of a process in the dose detection processing program which concerns on embodiment of this invention. It is a figure which shows the time transition of the accumulated dose signal produced | generated in the interface box which concerns on embodiment of this invention. It is a flowchart which shows the flow of a process in the inclination control program which concerns on embodiment of this invention. It is a flowchart which shows the flow of a process in the radiographic imaging processing program which concerns on this embodiment. It is the figure which illustrated the aspect which retrospectively corrects the reception timing of the dose information received with the delay by the interface box which concerns on the 2nd Embodiment of this invention. It is a figure which shows the time transition of the accumulated dose signal produced | generated in the interface box which concerns on the 2nd Embodiment of this invention. It is a flowchart which shows the flow of a process in the inclination control program which concerns on the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, substantially the same or equivalent components and parts are denoted by the same reference numerals.

  FIG. 1 is a diagram showing the configuration of a radiation information system (hereinafter referred to as “RIS” (Radiology Information System)) 100 according to an embodiment of the present invention.

  The RIS 100 is a system for managing information such as medical appointments and diagnosis records in the radiology department, and constitutes a part of a hospital information system (hereinafter referred to as “HIS” (Hospital Information System)).

  The RIS 100 includes a plurality of radiography requesting terminal devices (hereinafter referred to as “terminal devices”) 102, a RIS server 104, and a radiographic imaging system (hereinafter referred to as a radiography room (or operating room) in a hospital). , Referred to as “imaging system”) 200, which are connected to an in-hospital network 110 composed of a wired or wireless LAN (Local Area Network) or the like. The RIS 100 constitutes a part of the HIS provided in the same hospital, and an HIS server (not shown) that manages the entire HIS is also connected to the in-hospital network 110.

  The terminal device 102 is used by doctors and radiographers to input and view diagnostic information and facility reservations, and to make radiographic image capturing requests and imaging reservations. Each terminal device 102 includes a personal computer having a display device, and is connected to the RIS server 104 and the intra-hospital network 110 for mutual communication.

  The RIS server 104 receives an imaging request from each terminal device 102 and manages a radiographic imaging schedule in the imaging system 200, and includes a database 104A.

  The database 104A relates to patient (subject) attribute information (name, sex, date of birth, age, blood type, weight, patient ID (Identification), etc.), medical history, medical history, radiation images taken in the past, etc. Information, identification information (ID information) of the electronic cassette 1 described later used in the photographing system 200, information about the electronic cassette 1 such as model, size, sensitivity, start date of use, number of times of use, and the electronic cassette 1 are used. Thus, it is configured to include environment information indicating an environment in which a radiographic image is taken, that is, an environment in which the electronic cassette 1 is used (for example, a radiographic room or an operating room).

  The imaging system 200 captures a radiographic image by an operation of a doctor or a radiographer according to an instruction from the RIS server 104. The imaging system 200 includes an electronic cassette 1, a radiation generator 210, an interface box 220, and a console 230.

  The radiation generation apparatus 210 includes a radiation source 211 (see also FIG. 2) that irradiates a patient (subject) with a radiation such as an X-ray according to an exposure condition notified from the console 230.

  The electronic cassette 1 absorbs the radiation X transmitted through the imaging target region of the patient (subject), generates charges, and generates a radiation detector 10 (FIG. 3) that generates image information indicating a radiation image based on the generated charge amount. See also). The electronic cassette 1 has a function of detecting radiation emitted from the radiation generator 210 and outputting dose information indicating a dose per unit time of the detected radiation. The imaging system 200 according to the present embodiment has an automatic exposure control (AEC) function, and the timing of stopping the irradiation of radiation from the radiation generator 210 based on the dose information output from the electronic cassette 1 is determined. Be controlled. In the present embodiment, the above dose information is wirelessly transmitted from the electronic cassette 1 and received by the interface box 220.

  The interface box 220 is interposed between the electronic cassette 1 and the radiation generator 210, receives the above dose information wirelessly transmitted from the electronic cassette 1, and converts it into a signal format that can be recognized by the radiation generator 210. It is an interface device for doing. By providing such an interface box 220, an existing system that realizes automatic exposure control (AEC) using a conventional radiation detection device such as an ion chamber can be used as it is. In the present embodiment, the interface box 220 generates a cumulative dose signal Va that is an analog voltage signal indicating the cumulative dose of radiation irradiated to the electronic cassette 1 based on the dose information received from the electronic cassette 1, and It supplies to the radiation generator 210. When the radiation generator 210 detects that the voltage level of the cumulative dose signal Va supplied from the interface box 220 has reached a predetermined value, the radiation generator 210 stops the radiation irradiation.

  The console 230 acquires various types of information included in the database 104A from the RIS server 104, stores them in an HDD 236 (see FIG. 7) described later, and uses the information as necessary to use the electronic cassette 1 and the radiation generator 210. Control.

  FIG. 2 is a diagram illustrating an arrangement state of each apparatus constituting the imaging system 200 according to the embodiment of the present invention in the radiation imaging room 300.

  As shown in FIG. 2, the radiation imaging room 300 includes a standing base 310 used when capturing a radiographic image in a standing position and a supine position used when capturing a radiographic image in a lying position. A stand 320 is installed. The space in front of the standing base 310 is the imaging position 312 of the patient (subject) when radiographic images are captured in the standing position. The space above the prone table 320 is an imaging position 322 for the patient (subject) when radiographic images are taken in the prone position.

  The standing base 310 is provided with a holding unit 314 that holds the electronic cassette 1, and the electronic cassette 1 is held by the holding unit 314 when a radiographic image is taken in the standing position. Similarly, a holding unit 324 that holds the electronic cassette 1 is provided in the prone position table 320, and the electronic cassette 1 is held by the holding unit 324 when a radiographic image is taken in the prone position.

  In the radiation imaging room 300, the radiation source 211 constituting the radiation generator 210 can be rotated about a horizontal axis (in the direction of arrow a in FIG. 2) and in the vertical direction (in the direction of arrow b in FIG. 2). A support moving mechanism 214 is provided which is movable and further supported so as to be movable in the horizontal direction (the direction of arrow c in FIG. 2). Thereby, radiation imaging in a standing position and a supine position can be performed using a single radiation source 211.

  The cradle 310 has a housing portion 310 </ b> A that can store the electronic cassette 1. When the electronic cassette 1 is not used, the built-in battery is charged in a state of being housed in the housing portion 310A.

  In the imaging system 200, various types of information are transmitted and received between the radiation generator 210 and the console 230 and between the electronic cassette 1 and the console 230. In the imaging system 200 according to the present embodiment, dose information is wirelessly transmitted from the electronic cassette 1 to the interface box 220 in order to realize automatic exposure control (AEC).

  Next, the structure of the electronic cassette 1 as a radiographic imaging apparatus according to the present embodiment will be described. FIG. 3 is a perspective view showing the configuration of the electronic cassette 1. As shown in FIG. 3, the electronic cassette 1 includes a housing 2 made of a material that transmits radiation, and has a waterproof and airtight structure. When the electronic cassette 1 is used in an operating room or the like, there is a risk that blood or germs may adhere. Therefore, one electronic cassette 1 can be used repeatedly and continuously by sterilizing and cleaning the electronic cassette 1 as a waterproof and airtight structure as necessary.

  A space A for accommodating various components is formed inside the housing 2, and the patient (subject) is transmitted through the space A from the irradiation surface side of the housing 1 to which the radiation X is irradiated. The radiation detector 10 for detecting the radiation X and the lead plate 3 for absorbing the back scattered radiation of the radiation X are arranged in this order.

  An area corresponding to the position where the radiation detector 10 is disposed is an imaging area 4A capable of detecting radiation. The surface having the imaging region 4 </ b> A of the housing 2 is a top plate 5 in the electronic cassette 1. In the present embodiment, the radiation detector 10 has a TFT substrate 20 described later attached to the inner surface of the top plate 5. On the other hand, a cassette control unit 26 and a power supply unit 28 (both shown in FIG. 7), which will be described later, are accommodated on one end side inside the housing 2 at a position that does not overlap the radiation detector 10 (outside the range of the imaging region 4A). A case 6 is arranged.

  The casing 2 is made of, for example, carbon fiber (carbon fiber), aluminum, magnesium, bionanofiber (cellulose microfibril), or a composite material in order to reduce the weight of the entire electronic cassette 1.

  Next, the configuration of the radiation detector 10 built in the electronic cassette 1 will be described. FIG. 4 is a cross-sectional view schematically showing a laminated structure of the radiation detector 10. The radiation detector 10 uses a TFT substrate 20 formed by sequentially forming a signal output unit 12, a sensor unit 13, and a transparent insulating film 14 on an insulating substrate 16, an adhesive resin having low light absorption, and the like. And a scintillator 30 bonded on the TFT substrate 20.

  The scintillator 30 is formed on the sensor unit 13 via the transparent insulating film 14, and includes a phosphor that emits light by converting incident radiation into light. That is, the scintillator 30 absorbs radiation that has passed through the patient (subject) and emits light. The wavelength range of light emitted by the scintillator 30 is preferably a visible light range (wavelength 360 nm to 830 nm), and in order to allow monochrome imaging by the radiation detector 10, it may include a green wavelength range. More preferred. When imaging using X-rays as radiation, the phosphor used in the scintillator 30 preferably contains cesium iodide (CsI), and CsI (Tl) (with an emission spectrum of 420 nm to 700 nm at the time of X-ray irradiation) It is particularly preferable to use cesium iodide to which thallium is added. Note that the emission peak wavelength of CsI (Tl) in the visible light region is 565 nm.

  The sensor unit 13 includes an upper electrode 131, a lower electrode 132, and a photoelectric conversion film 133 provided between these electrodes. The photoelectric conversion film 133 is made of an organic photoelectric conversion material that generates charges by absorbing light emitted from the scintillator 30.

The upper electrode 131 is preferably made of a conductive material that is transparent at least with respect to the emission wavelength of the scintillator 30 because the light generated by the scintillator 30 needs to enter the photoelectric conversion film 133. Specifically, it is preferable to use a transparent conductive oxide (TCO) having a high transmittance for visible light and a small resistance value. Note that although a metal thin film such as Au can be used as the upper electrode 131, the TCO is preferable because the resistance value is likely to increase when the transmittance of 90% or more is obtained. For example, ITO, IZO, AZO, FTO, SnO ₂ , TiO ₂ , ZnO _{2 and the} like can be preferably used, and ITO is most preferable from the viewpoint of process simplicity, low resistance, and transparency. Note that the upper electrode 131 may have a single configuration common to all pixels, or may be divided for each pixel.

  The photoelectric conversion film 133 includes an organic photoelectric conversion material, absorbs light emitted from the scintillator 30, and generates charges according to the amount of absorbed light. The photoelectric conversion film 133 containing an organic photoelectric conversion material has a sharp absorption spectrum in the visible range, and electromagnetic waves other than light emitted by the scintillator 30 are hardly absorbed by the photoelectric conversion film 133. Therefore, it is possible to effectively suppress noise generated when radiation such as X-rays is absorbed by the photoelectric conversion film 133.

  The organic photoelectric conversion material that constitutes the photoelectric conversion film 133 is preferably such that its absorption peak wavelength is closer to the emission peak wavelength of the scintillator 30 in order to absorb light emitted by the scintillator 30 most efficiently. Ideally, the absorption peak wavelength of the organic photoelectric conversion material coincides with the emission peak wavelength of the scintillator 30, but if the difference between the two is small, the light emitted from the scintillator 30 can be sufficiently absorbed. . Specifically, the difference between the absorption peak wavelength of the organic photoelectric conversion material and the emission peak wavelength with respect to the radiation of the scintillator 30 is preferably within 10 nm, and more preferably within 5 nm. Examples of the organic photoelectric conversion material that can satisfy such conditions include quinacridone-based organic compounds and phthalocyanine-based organic compounds. For example, since the absorption peak wavelength in the visible region of quinacridone is 560 nm, if quinacridone is used as the organic photoelectric conversion material and CsI (Tl) is used as the material of the scintillator 30, the difference in peak wavelength can be made within 5 nm. Thus, the amount of charge generated in the photoelectric conversion film 133 can be substantially maximized.

  In order to suppress an increase in dark current, it is preferable to provide at least one of the electron blocking film 134 and the hole blocking film 135, and it is more preferable to provide both. The electron blocking film 134 can be provided between the lower electrode 132 and the photoelectric conversion film 133, and when a bias voltage is applied between the lower electrode 132 and the upper electrode 131, the photoelectric blocking film 133 is formed from the lower electrode 132. It is possible to prevent the dark current from being increased due to the injection of electrons. An electron donating organic material can be used for the electron blocking film 134. On the other hand, the hole blocking film 135 can be provided between the photoelectric conversion film 133 and the upper electrode 131, and when a bias voltage is applied between the lower electrode 132 and the upper electrode 131, It can be suppressed that holes are injected into the conversion film 133 and the dark current increases. An electron-accepting organic material can be used for the hole blocking film 135.

  A plurality of lower electrodes 132 are formed in a lattice shape (matrix shape) at intervals, and one lower electrode 132 corresponds to one pixel. Each lower electrode 132 is connected to a field effect thin film transistor (hereinafter simply referred to as TFT) 40 and a capacitor 50 that constitute the signal output unit 12. The insulating film 15 is interposed between the signal output unit 12 and the lower electrode 132, and the signal output unit 12 is formed on the insulating substrate 16. Since the insulating substrate 16 absorbs the radiation X in the scintillator 30, it is a thin substrate (a substrate having a thickness of about several tens of μm) that has low radiation X absorbability and has flexible electrical insulation. Specifically, it is preferably a synthetic resin, aramid, bionanofiber, or film glass (ultra-thin glass) that can be wound into a roll.

  Corresponding to the lower electrode 132, the signal output unit 12 includes a capacitor 50 for accumulating the charges transferred to the lower electrode 132, and a TFT 40 which is a switching element for converting the electric charges accumulated in the capacitor 50 into an electric signal and outputting the electric signal. Is formed.

  The capacitor 50 is electrically connected to the corresponding lower electrode 132 via a conductive wiring formed through the insulating film 15. Thereby, the electric charge collected by the lower electrode 132 can be moved to the capacitor 50. In the TFT 40, a gate electrode, a gate insulating film, and an active layer (channel layer) (not shown) are laminated, and a source electrode and a drain electrode are formed on the active layer with a predetermined interval.

  When the radiation detector 10 is of a so-called back side scanning method (PSS (Pentration Side Sampling) method), in which radiation is emitted from the scintillator 30 side to capture a radiation image, stronger light emission is obtained on the surface side of the scintillator 30. It is done. On the other hand, in the case of a so-called surface reading method (ISS (Irradiation Side Sampling) method) in which radiation images are taken by irradiating radiation from the TFT substrate 20 side, the scintillator 30 is stronger on the bonding surface side with the TFT substrate 20. Luminescence is obtained. In the radiation detector 10, the distance between the light emission position in the scintillator 30 and the TFT substrate 20 is shorter when the front surface reading method is used than when the rear surface reading method is used. High resolution.

  FIG. 5 is a diagram showing an electrical configuration of the radiation detector 10 constituting the electronic cassette 1. The electronic cassette 1 according to the present embodiment generates not only a function of taking a radiographic image but also generates and outputs dose information indicating a dose per unit time of radiation irradiated to the electronic cassette 1 via a subject. It has a function. The imaging system 200 according to the present embodiment has an automatic exposure control (AEC) function, and determines the timing of stopping irradiation of radiation from the radiation generator 210 based on the dose information output from the electronic cassette 1. Control. In order to realize this AEC function, the radiation detector 10 detects the dose of radiation that is transmitted through the subject and applied to the electronic cassette 1 in addition to the plurality of imaging pixels 60A for capturing a radiation image. A plurality of dose detection pixels 60B.

  As shown in FIG. 5, each of the imaging pixels 60 </ b> A includes a radiographic imaging sensor 13 </ b> A that is a part of the sensor unit 13 including the above-described photoelectric conversion film 133, and charges generated by the sensor 13 </ b> A. And a TFT 40 serving as a switching element that is turned on when the electric charge accumulated in the capacitor 50 is read out. The imaging pixels 60A are two-dimensionally arranged in rows and columns on the entire surface of the TFT substrate 20.

  The radiation detector 10 has a plurality of lines that extend in a certain direction (row direction) along the arrangement of the imaging pixels 60 </ b> A and supply a gate signal for turning on / off each TFT 40 to the gate terminal of each TFT 40. A plurality of signals for reading out the electric charges accumulated in the capacitor 50 through the on-state TFT 40 and extending in the direction (column direction) intersecting with the extending direction of the gate wiring 21 and the gate wiring 21 composed of G1 to Gn. Wiring 22 is provided. Each of the imaging pixels 60 </ b> A is provided corresponding to each intersection of the gate wiring 21 and the signal wiring 22.

  The dose detection pixel 60 </ b> B includes a radiation dose detection sensor 13 </ b> B that is a part of the sensor unit 13 including the photoelectric conversion film 133. The dose detection sensor 13B is directly connected to the signal wiring 22, and the electric charge generated by the sensor 13B flows out to the signal wiring 22 as it is. The sensors 13B are distributed and arranged over the entire area on the TFT substrate 20. In the present embodiment, the number of sensors 13B is smaller than the number of sensors 13A for radiographic imaging. In other words, the dose detection pixels 60B are formed on the TFT substrate 20 at a lower density than the imaging pixels 60A. A bias voltage is supplied to the radiation image capturing sensor 13A and the dose detection sensor 13B via a bias line (not shown), and both generate an amount of electric charge corresponding to the dose of the irradiated radiation. The size of the radiation image capturing sensor 13A and the dose detecting sensor 13B may be the same or different.

  FIG. 6 is a plan view illustrating the arrangement of the dose detection pixels 60 </ b> B on the radiation detector 10. Each of the signal wirings 22 is connected to a plurality (three in the example shown in FIG. 6) of dose detection pixels 60B adjacent to each other in the extending direction of the signal wirings 22, and the dose detection pixels 60B detect radiation. It arrange | positions so that it may disperse | distribute substantially uniformly in the container 10. FIG. In the example shown in FIG. 6, three dose detection pixels 60 </ b> B (dose detection sensor 13 </ b> B) are connected to the same signal wiring 22, but the dose detection pixels 60 </ b> B connected to the same signal wiring 22 The number can be changed as appropriate. The charges generated by the plurality of dose detection pixels 60 </ b> B connected to the same signal line 22 are added by joining on the signal line 22. A pixel unit 61 is formed by a plurality of dose detection pixels 60 </ b> B connected to the same signal wiring 22. In the example shown in FIG. 6, the pixel unit 61 is formed by three dose detection pixels 60B (sensor 13B). Note that the arrangement of the dose detection pixels 60B is not limited to that illustrated in FIG. 6, and in which part on the radiation detector 10 and how it is arranged can be changed as appropriate.

  FIG. 7 is a diagram illustrating a main configuration of the electrical system of the imaging system 200 according to the present embodiment. As shown in FIG. 7, the gate line driver 23 is arranged on one side of two adjacent sides of the radiation detector 10 incorporated in the electronic cassette 1, and the signal processing unit 24 is arranged on the other side. Each line G <b> 1 to Gn of the gate wiring 21 is connected to the gate line driver 23, and each of the signal wirings 22 is connected to the signal processing unit 24. The electronic cassette 1 includes an image memory 25, a cassette control unit 26, a wireless communication unit 27, and a power supply unit 28.

  The TFT 40 constituting the photographic pixel 60 </ b> A is driven to the ON state on a line basis by a gate signal supplied from the gate line driver 23 via the lines G <b> 1 to Gn of the gate wiring 21. When the TFT 40 is turned on, the electric charge generated by the sensor 13A and accumulated in the capacitor 50 is read out to each signal wiring 22 as an electric signal and transmitted to the signal processing unit 24. On the other hand, the charge generated by the sensor 13B constituting the dose detection pixel 60B flows out to the signal wiring 22 and is supplied to the signal processing unit 24 simultaneously with the generation of the charge, regardless of the gate signal from the gate line driver 23.

  FIG. 8 is a diagram illustrating a configuration of the signal processing unit 24. The signal processing unit 24 includes a charge amplifier 241 connected to each of the signal wirings 22. Each of the charge amplifiers 241 has an operational amplifier (operational amplifier circuit) 241A in which an inverting input terminal is connected to the corresponding signal wiring 22 and a non-inverting input terminal connected to the ground potential, and one terminal as an inverting input terminal of the operational amplifier 241A. Are connected, and the output terminal of the operational amplifier 241A includes a capacitor 241B having the other terminal connected thereto, and a reset switch 241C connected in parallel to the capacitor 241B.

  The charge generated in each of the imaging pixel 60A or the dose detection pixel 60B is accumulated in the capacitor 241B of the charge amplifier 241 via the signal wiring 22. The charge amplifier 241 generates an electric signal having a signal level corresponding to the amount of charge accumulated in the capacitor 241B, and supplies this to the sample and hold circuit 242. The electric charge accumulated in the capacitor 241B is discharged when the reset switch 92C is turned on in accordance with a control signal supplied from the cassette control unit 26, whereby the electric signal output from the charge amplifier 241 is reset.

  The sample hold circuit 242 samples and holds the signal level of the output signal of the charge amplifier 241 according to the control signal supplied from the cassette control unit 26, and supplies the held signal level to the multiplexer 243.

  The multiplexer 243 sequentially selects and outputs the signal level held in the sample hold circuit 242 according to the control signal supplied from the cassette control unit 26. That is, the multiplexer 243 converts the electrical signal from the sample hold circuit 242 into serial data and sequentially supplies this to an A / D (analog / digital) converter 244.

  The A / D converter 244 converts the signal level of the electrical signal sequentially supplied from the multiplexer 243 into a digital signal. That is, the A / D converter 244 outputs the pixel value of the imaging pixel 60A or the dose detection pixel 60B as a digital signal.

  The image memory 25 has a storage capacity capable of storing a predetermined number of image data, and image data obtained by imaging is sequentially stored in the image memory 25 every time a radiographic image is captured. The image memory 25 is connected to the cassette control unit 26.

  The cassette control unit 26 comprehensively controls the operation of the entire electronic cassette 1. The cassette control unit 26 includes a microcomputer, and includes a CPU (Central Processing Unit) 26A, a memory 26B including a ROM (Read Only Memory) and a RAM (Random Access Memory), a nonvolatile storage unit including a flash memory and the like. 26C. A wireless communication unit 27 is connected to the cassette control unit 26.

  The wireless communication unit 27 corresponds to a wireless local area network (LAN) standard represented by IEEE (Institute of Electrical and Electronics Engineers) 802.11a / b / g and the like, and performs wireless communication with external devices. Controls the transmission of various types of information. The cassette control unit 26 can wirelessly communicate with the console 230 and the interface box 220 via the wireless communication unit 27.

  The electronic cassette 1 is provided with a power supply unit 28, and various circuits and elements (a microcomputer functioning as a gate line driver 23, a signal processing unit 24, an image memory 25, a wireless communication unit 27, and a cassette control unit 26) are provided. The power supply unit 28 is operated by the power supplied from the power supply unit 28. The power supply unit 28 incorporates a battery (a rechargeable secondary battery) so as not to impair the portability of the electronic cassette 1, and supplies power from the charged battery to various circuits and elements. In FIG. 7, wiring for connecting the power supply unit 28 to various circuits and elements is omitted.

  The console 230 is configured as a server computer that performs control related to radiographic image capturing, and includes a display 231 that displays an operation menu, a captured radiographic image, and the like, and a plurality of keys. An operation panel 232 for inputting instructions. The console 230 includes a CPU 233 that controls the operation of the entire apparatus, a ROM 234 that stores various programs including a control program, a RAM 235 that temporarily stores various data, and an HDD that stores and holds various data. (Hard Disk Drive) 236, a display driver 237 that controls display of various types of information on the display 231, and an operation input detection unit 238 that detects an operation state of the operation panel 232. The console 230 includes a wireless communication unit 239 that transmits and receives various types of information such as image data to and from the electronic cassette 1 by wireless communication, and a communication port for transmitting exposure conditions and the like to the radiation generator 210. 240.

  The CPU 233, ROM 234, RAM 235, HDD 236, display driver 237, operation input detection unit 238, wireless communication unit 239, and communication port 240 are connected to each other via a system bus BUS. Therefore, the CPU 233 can access the ROM 234, RAM 235, and HDD 236, controls the display of various information on the display 231 via the display driver 237, and performs various operations with the electronic cassette 1 via the wireless communication unit 239. Transmission / reception of information and supply of exposure conditions to the radiation generator 210 via the communication port 240 can be performed. Further, the CPU 233 can grasp the operation state of the user with respect to the operation panel 232 via the operation input detection unit 238.

  The radiation generator 210 receives the radiation dose 211 that generates X-rays, the communication port 213 for receiving the exposure conditions transmitted from the console 230, and the accumulated dose signal Va supplied from the interface box 220 as an AEC control input. And an AEC input terminal 214 for receiving, and a control unit 212 for controlling the radiation source 211 based on the received exposure conditions and the accumulated dose signal Va. The exposure conditions supplied from the console 230 include information such as tube voltage and tube current. The control unit 212 controls the radiation source 211 to emit radiation from the radiation source 211 with a tube voltage and a tube current according to the exposure conditions. In addition, when the control unit 212 detects that the voltage level of the cumulative dose signal Va supplied from the interface box 220 has reached a predetermined threshold value, the control unit 212 stops radiation irradiation. In the imaging system 200 according to the present embodiment, the radiation generating apparatus 210, the console 230, and the interface box 220 can communicate with each other by wire, but these communications may be performed wirelessly.

  The interface box 220 is interposed between the electronic cassette 1 and the radiation generator 210, receives dose information wirelessly transmitted from the electronic cassette 1, and converts it into a signal format that can be recognized by the radiation generator 210. Interface device. More specifically, the interface box 220 is an analog voltage signal indicating the cumulative dose of radiation irradiated to the electronic cassette 1 based on the pixel value of the dose detection pixel 60B supplied as dose information from the electronic cassette 1. The accumulated dose signal Va is generated and supplied to the radiation generator 210.

  The wireless communication unit 221 has a function of receiving dose information wirelessly transmitted from the electronic cassette 1. The CPU 222 generates an inclination control signal θ for controlling the inclination of the cumulative dose signal Va, which is an output signal of the interface box 220, based on the pixel value as dose information intermittently supplied from the electronic cassette 1, Is supplied to the D / A converter 223. In addition, the CPU 222 detects a delay in the reception timing of dose information intermittently wirelessly transmitted from the electronic cassette 1, and reduces the error generated in the accumulated dose signal Va due to the delay. Adjust the signal level. The D / A converter 223 converts the tilt control signal θ, which is a digital signal supplied from the CPU 222, into an analog signal. That is, the D / A converter 223 generates an analog signal having a voltage level corresponding to the signal value of the inclination control signal θ. The integrator 224 performs time integration on the analog signal supplied from the D / A converter 223 and outputs the result. The output signal of the integrator 224 is supplied to the radiation generator 210 through the output terminal 225 as the accumulated dose signal Va indicating the accumulated dose of the radiation applied to the electronic cassette 1.

[Dose detection processing]
Below, the dose detection process which produces | generates the dose information which shows the dose per unit time of the radiation with which the electronic cassette 1 was irradiated to self is demonstrated.

  FIG. 9 is a flowchart showing a flow of processing in the dose detection processing program executed by the CPU 26 </ b> A of the cassette control unit 26 of the electronic cassette 1. The program is stored in advance in a predetermined area of the storage unit 26C of the cassette control unit 26. The program is executed at a predetermined timing when a radiographic image for diagnosis is captured using the imaging pixel 60A.

  In step S <b> 11, the CPU 26 </ b> A supplies a control signal to the charge amplifier 241 of the signal processing unit 24. When receiving the control signal, the charge amplifier 241 resets the charge amplifier 241 by turning on the reset switch 241C. When the reset of the charge amplifier 241 is completed, the reset switch 241C is driven to an off state.

  In step S12, the CPU 26A supplies control signals to the sample hold circuit 242 and the multiplexer 243 to drive them synchronously. Thereafter, when the radiation applied from the radiation generator 210 is applied to the electronic cassette 1, each of the imaging pixels 60A and each of the dose detection pixels 60B generates an electric charge. During the period when the electronic cassette 1 is irradiated with radiation, all the TFTs 40 are turned off, and the charge generated in the imaging pixel 60A is accumulated in the capacitor 50. On the other hand, the charge generated in the dose detection pixel 60B is input to the charge amplifier 241 connected to each signal line via each signal line 22. The charges from the plurality of dose detection pixels 60 </ b> B constituting the pixel unit 61 connected to the same signal wiring 22 merge on the signal wiring 22 and are supplied to the signal processing unit 24.

  Each charge amplifier 241 outputs an output signal corresponding to the amount of charge supplied through the signal wiring 22. Each sample hold circuit 242 connected to each charge amplifier 241 samples the output signal of the charge amplifier 241. The multiplexer 243 sequentially supplies the output of each sample hold circuit 242 to the A / D converter 244 in synchronization with the sampling period. The A / D converter 244 converts the analog signals sequentially supplied from the multiplexer 243 into digital signals. That is, the A / D converter 244 sequentially outputs a value obtained by sampling the output of each charge amplifier 241 as a digitized pixel value.

  In step S <b> 13, the CPU 26 </ b> A receives the digitized pixel value for each pixel unit 61 from the signal processing unit 24.

  In step S <b> 14, the CPU 26 </ b> A generates, for each pixel unit 61, dose information indicating the dose per unit time of the radiation applied to the electronic cassette 1 based on the received pixel value for each pixel unit 61. The dose information may indicate, for example, a value obtained by dividing the pixel value for each pixel unit received from the signal processing unit 24 by the accumulation time of the charge amplifier 241.

  In step S <b> 15, the CPU 26 </ b> A wirelessly transmits dose information corresponding to the pixel value of the dose detection pixel 60 </ b> B (pixel unit 61) to the interface box 220 via the wireless communication unit 27.

  In step S <b> 16, the CPU 26 </ b> A determines whether or not the radiation irradiation from the radiation generator 210 is stopped. For example, when the pixel value supplied from the signal processing unit 24 is equal to or less than a predetermined threshold, the CPU 26A detects that radiation irradiation from the radiation generation apparatus 210 has stopped. If the CPU 26A determines that radiation irradiation has not stopped, the process returns to step S11. That is, while radiation is being emitted from the radiation generator 210, the processes of steps S <b> 11 to S <b> 15 are repeatedly performed, and dose information is intermittently wirelessly transmitted from the electronic cassette 1 to the interface box 220. The cassette control unit 26 generates the dose information at a constant interval (for example, 1 msec cycle) by repeatedly executing the processes of steps S11 to S15, and wirelessly transmits the dose information to the interface box 220. When the CPU 26A determines in step S16 that the irradiation of radiation from the radiation generating apparatus 210 has been stopped, this routine ends.

As described above, in the electronic cassette 1 according to the present embodiment, in order to realize automatic exposure control (AEC), the dose information indicating the dose per unit time of the radiation applied to the radio cassette when the radiographic image is captured is intermittent. The interface box 220 is notified.
[Function of interface box]
Hereinafter, the operation of the interface box 220 that has received dose information from the electronic cassette 1 will be described. FIG. 10A is a diagram illustrating an example of a time transition of the accumulated dose signal Va generated by the interface box 220. FIG. As described above, the electronic cassette 1 uses a value corresponding to the pixel value of the dose detection pixel 60B (pixel unit) as a dose information indicating a dose per unit time of radiation irradiated to itself, for example, a fixed transmission cycle T (for example, 1 msec), wirelessly transmitted to the interface box 220. The dose information transmitted from the electronic cassette 1 is received by the wireless communication unit 221 of the interface box 220. Each plot in FIG. 10A shows the reception point of dose information in the interface box 220. In the example shown in FIG. 10A, a solid line indicates a case where dose information is received by the interface box 220 without a delay at times t ₁ , t ₂ , t ₃ , and t ₄ .

When receiving the _first dose information P 1 from the electronic cassette 1 at time t ₁ , the CPU 222 of the interface box 220 adds a predetermined coefficient α to the pixel value (or a value corresponding to the pixel value) as the dose information P _1. generating a tilt control signal theta ₁ by multiplying. The CPU 222 supplies the generated tilt control signal θ ₁ to the D / A converter 223.

D / A converter 223 converts the tilt control signals theta ₁ is a digital signal into an analog signal. That is, the D / A converter 223 generates an analog signal having a voltage level corresponding to the signal value of the inclination control signal θ ₁ . The D / A converter 223 supplies the generated analog signal to the integrator 224. The integrator 224 integrates the analog signal supplied from the D / A converter 223 over time. That is, the integrator 224 outputs an analog cumulative dose signal Va in which the voltage level rises with a slope corresponding to the value of the slope control signal θ ₁ . The cumulative dose signal Va rises with a slope corresponding to the value of the slope control signal θ ₁ during the period from the _first dose information reception time t ₁ to the second dose information reception time t ₂ .

When the CPU 222 of the interface box 220 receives dose information P ₂ , P ₃ , P ₄ ,... At times t ₂ , t ₃ , t ₄ ,..., Tilt control is performed based on each of these dose information. Signals θ ₂ , θ ₃ , θ ₄ ,... Are generated to control the slope of the accumulated dose signal Va. That is, the cumulative dose signal Va, the time t ₂ in a period from the ~t ₃ increases with a gradient corresponding to the value of the tilt control signals theta _2, the time t ₃ the slope in the period until ~t ₄ control signals theta ₃ It rises with a slope according to the value of. As described above, when receiving the dose information intermittently wirelessly transmitted from the electronic cassette 1, the interface box 220 updates the slope of the accumulated dose signal Va based on the received latest dose information. The accumulated dose signal Va is supplied to the radiation generator 210 via the output terminal 225 of the interface box 220.

  When the control unit 212 of the radiation generating apparatus 210 detects that the voltage level of the accumulated dose signal Va supplied via the AEC input terminal 214 has reached a predetermined threshold value, the control unit 212 stops the radiation irradiation from the radiation source 211. Thereby, automatic exposure control (AEC) is realized in the photographing system 200 according to the present embodiment.

Further, in FIG. 10 (a), transition of the accumulated dose signals Va when a delay in the reception timing of dose information P ₂ to be received at time t ₂ occurs is indicated by a broken line. The interface box 220 updates the slope of the cumulative dose signal Va when receiving dose information wirelessly transmitted from the electronic cassette 1, so that when the dose information reception timing is delayed from the normal timing, the cumulative dose signal An error occurs in the voltage level of Va. The interface box 220 adjusts the voltage level of the cumulative dose signal so as to reduce the error generated in the cumulative dose signal Va due to the delay in the reception timing of the dose information.

In FIG. 10B, the time transition of the accumulated dose signal Va when the dose information wirelessly transmitted from the electronic cassette 1 due to interference or the like is received by the interface box 220 with a delay is shown by a solid line. . In the example shown in FIG. 10 (b), there is shown the case where the second dose information P ₂ to be received at time t ₂ is received at time t _21. In this case, the slope of the cumulative dose signal Va is controlled by the slope control signal θ ₁ generated based on the dose information P ₁ received for the first time until the time t ₂₁ when the second dose information P ₂ is received. Will be. As a result, error occurs in the voltage level of the accumulated dose signals Va at time t _21.

  The CPU 222 of the interface box 220 receives the dose information received this time by comparing the reception interval between the dose information received earlier and the dose information received this time with the transmission period T of dose information in the electronic cassette 1. Determine timing delay. Then, when detecting the delay, the CPU 222 performs a process of correcting an error generated in the accumulated dose signal Va by generating an adjustment inclination control signal θ.

In the example shown in FIG. 10 (b), than the transmission period T of the interval between the reception time t ₁ of dose information P ₁ received the first time to the reception time t ₂₁ of dose information P ₂ received the second time is dose information Therefore, the CPU 222 determines that there is a delay in the reception timing of the _second dose information P2. The delay determination of the dose information reception timing may be performed, for example, by collating a reception time stamp given to the dose information. The reception time stamp is time information indicating the reception time of the dose information in the interface box 220, and is given to the dose information by the wireless communication unit 221. On the other hand, information indicating the transmission period T of dose information in the electronic cassette 1 is transmitted from the electronic cassette 1 together with the dose information, for example, and the interface box recognizes the transmission period T by receiving this information. As described above, the CPU 222 of the interface box 220 determines whether or not there is a delay in receiving the dose information based on the information indicating the transmission cycle T and the time information such as the reception time stamp given to the dose information. To do.

CPU222 of interface box 220, the first second and the interval from the reception time _{t 1} dose information _{P 1} to the reception time _{t 21} of dose information _{P 2} received the second time coincides with the transmission period T of the received estimating the time course of the cumulative dose signal Va in the case of shifting of the reception time of dose information P ₂ at time t _2. That is, the CPU 222 estimates the time transition of the cumulative dose signal Va when the slope control of the cumulative dose signal Va based on the slope control signal θ ₂ corresponding to the _second dose information P ₂ is started at time t ₂ (see FIG. 10 (b).

The CPU 222 generates a correction inclination control signal θ _m1 for the adjustment period τ _m1 from time t ₂₁ to t ₂₂ so that the voltage level of the accumulated dose signal Va in which an error has occurred at time t ₂₁ converges to the estimated line. Thus, the inclination control of the accumulated dose signal Va is performed. As in the example shown in FIG. 10B, when the signal level of the accumulated dose signal Va exceeds the estimated line due to the delay in the reception timing of the dose information, the correction inclination control signal θ _m1 is For example, it may correspond to zero inclination. In this case, in the adjustment period τ _m1 from time t ₂₁ to time t ₂₂ , the voltage level of the cumulative dose signal Va changes at a constant level. The CPU 222 derives the adjustment period τ _m1 and the correction inclination control signal θ _m1 by calculation so that the voltage level of the cumulative dose signal Va converges on the estimated line.

The voltage level of the accumulated dose signals Va at time t ₂₂ the adjustment period by such processing is completed is corrected to a proper value reaches the estimated line. CPU222 is cumulative dose signal Va voltage level is time _{t 22} after serving as the proper value of the slope of the cumulative dose signal Va by the inclination control signal theta ₂ which corresponds to the second dose information _{P 2} received at time _{t 21} To control. As described above, when the signal level of the cumulative dose signal Va becomes excessive due to the delay in the reception timing of the dose information, the voltage level of the cumulative dose can be made to converge to the estimated line by changing the voltage level constant. preferable. A method of converging the voltage level of the cumulative dose signal Va to the estimated line by shifting the voltage level of the cumulative dose signal Va to the estimated line is conceivable. In this case, however, the radiation generator 210 may make an error determination. is there. In this case, it is necessary to separately provide a subtractor or the like for correcting the output of the integrator 224, and the configuration becomes complicated.

Further, in the example shown in FIG. 10 (b), 3 th dose information P ₃ to be received at time t ₃ is received at time t _31. Thus, between times t ₂₂ ~t _31, the tilt control signal theta ₂ which has been generated based on the dose information P ₂ received the second time is maintained, the error in the voltage level of the accumulated dose signals Va at time t ₃₁ Has occurred.

Since the interval from the reception time t _{1 of the first} dose information P ₁ to the reception time t ₃₁ of the third dose information is longer than twice (2T) the transmission period T of dose information, the CPU 222 it is determined that a delay in the reception timing of dose information P ₃ is generated, processing is performed to correct the error caused in the cumulative dose signal Va derive the estimated line in the same manner as described above. Incidentally, a distance from the second reception time of dose information P ₂ to the third reception time of dose information P _3, the delay of the third reception timing of dose information P ₃ by comparing the transmission period T It may be determined. Further, the delay of the reception timing of the _third dose information P3 may be determined by comparing both the first and third reception intervals and the second and third reception intervals with the transmission period T.

CPU222, as the interval from the reception time _{t 1} of dose information _{P 1} received the first time to the reception time _{t 31} of dose information _{P 3} received for the third time is equal to 2 times (2T) of the transmission cycle T estimating the time course of the cumulative dose signal Va in the case of shifting the third reception time of dose information P ₃ at time t _3. That is, the CPU 222 uses the time transition of the cumulative dose signal Va when the tilt control of the cumulative dose signal Va based on the tilt control signal θ ₃ corresponding to the _third dose information P ₃ is started at time t ₃ as an estimated line. To derive.

The CPU 222 generates an inclination control signal θ _m2 for correction in the adjustment period τ _m2 from time t ₃₁ to t ₃₂ so that the voltage level of the accumulated dose signal Va in which an error has occurred at time t ₃₁ converges to the estimated line. Thus, the inclination control of the accumulated dose signal Va is performed.

The voltage level of the accumulated dose signals Va at time t ₃₂ the adjustment period ends by such processing is corrected to a proper value reaches the estimated line. CPU222 is the slope of the cumulative dose signal Va by cumulative dose signal Va voltage level is the time _{t 32} after serving as the proper value of the tilt control signals theta ₃ corresponding to the third dose information _{P 3} received at time _{t 31} To control.

  As described above, when a delay occurs at the reception time point of the dose information wirelessly transmitted from the electronic cassette 1, the interface box 220 corrects the error of the accumulated dose signal Va accompanying the communication delay.

  FIG. 11 is a flowchart showing a flow of processing in an inclination control program for performing inclination control of the accumulated dose signal Va executed by the CPU 222 of the interface box 220. The program is stored in advance in a predetermined area of a storage unit (not shown) of the interface box 220. The program is executed at a predetermined timing when a radiographic image for diagnosis is captured using the imaging pixel 60A.

  In step S21, the CPU 222 determines whether or not dose information is received from the electronic cassette 1 in the wireless communication unit 221. If reception of dose information is detected, the process proceeds to step S22.

  In step S22, the CPU 222 refers to the reception time stamp given to the m-th dose information received before this time and the reception time stamp given to the n-th (m <n) dose information received this time. .

  In step 23, the CPU 222 derives the dose information reception interval from the time indicated by the time stamp referred in step S22, and compares this with the dose information transmission cycle T, thereby receiving the reception timing of the nth dose information received this time. It is determined whether or not there is a delay. That is, the CPU 222 has a value obtained by multiplying the transmission time T of dose information by (n−m), the interval between the reception time of the m-th dose information received earlier and the reception time of the n-th dose information received this time. If it is longer, it is determined that there is a delay in the reception timing of the nth dose information received this time. Note that the dose information transmission period T in the electronic cassette 1 may be determined in advance, or the electronic cassette 1 transmits information indicating the transmission period T together with the dose information, and the interface box 220 receives the information to transmit the information. The period T may be acquired. Also, the nth dose received this time by comparing the interval between the reception time of the nth dose information received this time and the reception time of the (n-1) th dose information received last time and the transmission period T. It is also possible to make a delay determination of information reception timing.

  In step S24, the CPU 222 makes the interval between the reception time of the m-th dose information received previously and the reception time of the n-th dose information received this time coincide with (n−m) times the transmission cycle T. An estimated line (see FIG. 10B) of the cumulative dose signal Va when the reception time point of the nth dose information received this time is shifted is derived. That is, an estimation line is derived when the reception time point of the nth dose information received this time is shifted to a time point at which it is determined that there is no delay.

In step S25, the CPU 222 performs adjustment so that the voltage level of the accumulated dose signal Va in which an error has occurred due to the delay in receiving dose information is converged to the estimated line derived in step S24. The inclination control signal θ _m and the adjustment period τ _m are derived. Thus, the slope of the cumulative dose signal Va may, until adjustment period tau _m from the reception time of this dose information has elapsed, the control of the gradient corresponding to the gradient control signal theta _m for adjustment, the cumulative dose signal Va Voltage level reaches the estimated line derived in step S24.

  In step S26, the CPU 222 derives a slope control signal θ corresponding to the current dose information by multiplying the pixel value as the current dose information received in step S21 by a predetermined coefficient α, and calculates the accumulated dose signal Va. Control the tilt. Thereby, the cumulative dose signal Va traces on the estimated line derived in step S24. That is, the error generated in the accumulated dose signal Va due to the delay in receiving dose information is eliminated.

  In step S <b> 27, the CPU 222 determines whether radiation irradiation from the radiation generation apparatus 210 has stopped. For example, the CPU 222 can detect the radiation irradiation stop by receiving a control signal indicating the radiation irradiation stop supplied from the electronic cassette 1. When the CPU 222 detects that radiation irradiation has been stopped, this routine ends. When it is not detected that radiation irradiation has stopped, the process returns to step S21. That is, the CPU 222 continues to output the accumulated dose signal Va by repeatedly executing the processes of steps S21 to S26 while the radiation generator 210 is irradiated with radiation.

[Radiation image processing]
Below, the radiographic imaging process performed in the electronic cassette 1 which concerns on this embodiment is demonstrated. FIG. 12 is a flowchart showing a processing flow in the radiographic image capturing processing program executed by the CPU 26 </ b> A of the cassette control unit 26 of the electronic cassette 1. The radiographic image processing program is stored in advance in a predetermined area of the storage unit 26C of the cassette control unit 26.

  When radiographic images are taken using the electronic cassette 1, an initial information input screen for inputting predetermined initial information is displayed on the display 231 of the console 230. On the initial information input screen, for example, the input of the exposure condition such as the name of the patient (subject) who is to take a radiographic image, the part to be imaged, the posture at the time of imaging, the tube voltage and the tube current when the radiation is exposed A prompt message and an input area for these initial information are displayed. The photographer inputs predetermined initial information via the operation panel 232 from the initial information input screen.

  The initial information is transmitted from the console 230 to the electronic cassette 1 via the wireless communication unit 239. Further, the exposure condition included in the initial information is transmitted to the radiation generation apparatus 210 via the communication port 240. In response to this, the control unit 212 of the radiation generating apparatus 210 prepares for exposure under the received exposure conditions.

  When the CPU 26A of the cassette control unit 26 receives the initial information from the console 230, the CPU 26A executes the radiographic image capturing processing program.

  In step S <b> 31, the CPU 26 </ b> A of the cassette control unit 26 waits for a radiation irradiation start instruction from the console 230. When the CPU 26A receives an instruction to start radiation irradiation, the process proceeds to step S32.

  In step S32, the CPU 26A of the cassette control unit 26 supplies a control signal to the gate line driver 23 so as to turn off all the TFTs 40. As a result, the imaging pixel 60A is in a state in which charges generated in response to radiation irradiation can be accumulated.

  In step S33, the CPU 26A executes the above-described dose detection process (see FIG. 9). That is, the charges generated in each of the dose detection pixels 60 </ b> B in response to radiation irradiation are supplied to the signal processing unit 24 through the signal wiring 22. In the electronic cassette 1 according to the present embodiment, the charges from the plurality of dose detection pixels 60 </ b> B constituting the pixel unit 61 connected to the same signal wiring 22 merge on the signal wiring 22 to the signal processing unit 24. Then, the signal processing unit 24 generates a pixel value for each pixel unit. The CPU 26A generates dose information indicating the dose per unit time of the radiation applied to the electronic cassette 1 based on the pixel value for each pixel unit 61, and wirelessly transmits this to the interface box 220 at a predetermined transmission cycle T. . The interface box 220 generates a cumulative dose signal Va indicating the cumulative dose of radiation applied to the electronic cassette 1 based on the dose information supplied from the electronic cassette 1, and supplies this to the radiation generator 210. When the radiation generator 210 detects that the voltage level of the cumulative dose signal Va has reached a predetermined threshold, the radiation generator 210 stops radiation irradiation.

  In step S34, the CPU 26A reads out the electric charges accumulated in the imaging pixels 60A and generates a diagnostic radiation image. Specifically, the CPU 26 </ b> A supplies a control signal to the gate line driver 23 to output an ON signal to each gate wiring 21 sequentially from the gate line driver 23 line by line, and each TFT 40 connected to each gate wiring 21 is output. Turn on one line at a time. Thereby, the electric charge accumulated in the capacitor 50 of each photographing pixel 60A is read to each signal wiring 22, converted into a digital signal by the signal processing unit 24, and supplied to the CPU 26A. The CPU 26A generates diagnostic image data based on the digitized pixel value of the imaging pixel 60A and stores it in the image memory 25.

  In step S <b> 35, the CPU 26 </ b> A reads the image data stored in the image memory 25, transmits the read image data to the console 230 via the wireless communication unit 27, and then ends this routine.

  In the console 230, the image data supplied from the electronic cassette 1 is stored in the HDD 236, and the radiation image indicated by the image data is displayed on the display 231. In addition, the console 230 transmits this image data to the RIS server 104 via the hospital network 110. Note that the image data transmitted to the RIS server 104 is stored in the database 104A.

As described above, the electronic cassette 1 according to the embodiment of the present invention includes the dose detection pixel 60B for detecting the dose of radiation applied to the electronic cassette 1 and electronically based on the pixel value in the dose detection pixel 60B. Dose information indicating the dose per unit time of the radiation applied to the cassette 1 is generated. The electronic cassette 1 generates dose information at a predetermined sampling period, and sequentially wirelessly transmits it to the interface box 220. The interface box 220 generates an inclination control signal θ based on the received dose information, and controls the inclination of the accumulated dose signal Va by the inclination control signal θ. When the interface box 220 receives dose information from the electronic cassette 1, the interface box 220 controls the slope of the accumulated dose signal Va. Therefore, when reception of dose information is delayed in the interface box 220 due to interference or the like, an error occurs in the accumulated dose signal Va. Arise. Therefore, the interface box 220 determines the delay of the reception timing of the dose information by comparing the transmission period T of the dose information intermittently transmitted from the electronic cassette 1 with the reception interval of the dose information. Then, the interface box 220 derives an estimation line that estimates the time transition of the accumulated dose signal when the reception time of the dose information received with a delay is shifted to the time when it is determined that there is no delay, It generates a tilt control signal theta _m for adjustment to converge to the estimated line to control the slope of the cumulative dose signal Va with. As a result, the error generated in the accumulated dose signal Va due to the delay in the reception timing of the dose information is eliminated.

  As described above, according to the imaging system 200 according to the embodiment of the present invention, the accumulated dose signal Va converges to an appropriate value even when the dose information wirelessly transmitted from the electronic cassette 1 is received in the interface box 220 with a delay. Thus, appropriate automatic exposure control (AEC) can be performed.

[Second Embodiment]
Hereinafter, the inclination control of the accumulated dose signal Va in the interface box 220 according to the second embodiment of the present invention will be described. In the tilt control according to the first embodiment described above, the delay determination is performed only for the reception time of the latest dose information, and the reception time of the latest dose information is shifted to the time when it is determined that there is no delay. The accumulated dose signal Va is derived, and the inclination control of the accumulated dose signal Va is performed so as to coincide with the derived estimated line, thereby eliminating the error of the accumulated dose signal Va. On the other hand, in the tilt control according to the second embodiment, the delay of the reception timing of each dose information received in the past with reference to the reception time of the latest dose information is determined, and the dose information received with a delay. An estimated line of the accumulated dose signal Va when the reception timing of the signal is corrected retroactively is derived, and the inclination of the accumulated dose signal Va is controlled so as to coincide with the estimated line.

FIG. 13 is a diagram illustrating a mode in which the reception timing of the dose information received by the interface box 220 according to the second embodiment with a delay is retroactively corrected. In FIG. 13, the black plot indicates the actual reception timing of the dose information in the interface box 220, and the white plot indicates the corrected reception timing. Incidentally, the regular reception time of dose information is _{t 1, t 2, t 3} , t 4, t 5, time _{t 1 ~t 2, t 2 ~t} 3, t 3 ~t 4, t 4 ~t The interval of ₅ is assumed to coincide with the transmission period T of dose information.

In the example shown in FIG. 13, in step S101, 1 st dose information _{P 1} is received by the interface box 220 to the time _{t 12} which is delayed from the reception time _{t 1} of the normal, the second dose information _{P 2} are received regular when received at the interface box 220 from time t ₂ to the delay time t ₂₁ is shown.

In step S102, the interface box 220 CPU 222 is a spacing between the reception time of the reception time and dose information _{P 2} of dose information _{P 1} is shorter than the transmission period T of dose information, the dose information _{P 1} previously received It is determined that there is a delay in reception timing. In addition, CPU222 is good also as grasping | ascertaining the reception time of each dose information from the reception time stamp provided to the said dose information. The CPU 222 shifts the reception timing of the previously received dose information P ₁ to time t ₁₁ so that the interval between the reception time of the dose information P _{1 and} the reception time of the dose information P ₂ coincides with the transmission cycle T. An estimated line of the cumulative dose signal Va is derived to correct the current voltage level of the cumulative dose signal Va. That is, the CPU 222 derives an estimated line when the tilt control by the tilt control signal θ ₁ corresponding to the dose information P ₁ is started from the time t _11, and adjusts so that the accumulated dose signal Va reaches this estimated line. deriving a tilt control signal theta _m. Further, in the example shown in FIG. 13, in step S102, it is illustrated the case where the third dose information P ₃ is received by the reception time t ₃ of the normal.

In step S103, CPU 222 of interface box 220 is twice the transmission period T of the interval dose information and the reception time _{t 11} the reception time _{t 3} and dose information _{P 1} that is corrected in step S102 of dose information _{P 3} ( shorter than 2T), it is determined that the still delay the reception timing of dose information P ₁ that has been modified in the previous step S102 occurs. The CPU 222 corrects the reception timing of the dose information P ₁ to time t ₁ so that the interval between the reception time of the dose information P _{1 and the} reception time of the dose information P ₃ coincides with 2T. Further, CPU 222, since the interval between the reception time _{t 21} and the reception time _{t 3} of the dose information _{P 3} of the dose information _{P 2} is shorter than the transmission period T, which delay occurs in the reception timing of dose information _{P 2} Judge. The CPU 222 corrects the reception timing of the dose information P ₂ at time t ₂ so that the interval between the reception time of the dose information P _{2 and} the reception time of the dose information P ₃ coincides with the transmission cycle T. CPU222, the correction voltage level of the accumulated dose signals Va at the present time to derive an estimated line of the cumulative dose signal Va in this manner when the received timing of dose information P ₁ and P ₂ respectively times t ₁ and t ₂ To do. That, CPU 222 may initiate the tilt control by tilt control signal theta ₁ which corresponds to the dose information P ₁ with started at time t _1, the tilt control from time t ₂ due to the inclination control signal theta ₂ which corresponds to the dose information P ₂ was estimated line derives when the cumulative dose signal Va derives the tilt control signal theta _m for adjustment to reach the estimated line. Further, in the example shown in FIG. 13, in step S103, if the fourth dose information P ₄ is received at time t ₄₁ which is delayed from the reception time t ₄ of the normal is illustrated.

In step S104, CPU 222 of interface box 220, the distance between the reception time _t 1, _{t 2} of dose information _{P 1} and _{P 2} which is corrected at the receiving time _{t 41} and step S103 of dose information _{P 4,} respectively, the dose longer than the three times the transmission period T of the data (3T) and twice (2T), determines that the reception timing of dose information was modified P ₁ and P ₂ do not occur delays. In this case, CPU 222, the correction of the reception timing of dose information _{P 1} and _{P 2} is not performed. Similarly, since the interval between the reception time _{t 41} the reception time _{P 3} and dose information _{P 4} dose information _{P 3} is longer than the transmission period T, CPU 222, the correction of the reception timing of dose information _{P 3} is not performed. Further, in the example shown in FIG. 13, in step S104, it is illustrated when the fifth dose information P ₅ is received in the reception time t ₅ of the regular.

In step S105, the reception time _{t 5} the dose information _{P 5,} the reception time _{t 3} of the dose information _{P 3} that is not the reception time _t 1, _{t 2} and corrected dose information is corrected _P 1, _{P 2} in step S103 Are equal to 4T, 3T, and 2T, respectively, the CPU 222 of the interface box 220 has a delay in the reception timing of the corrected dose information P ₁ and P ₂ and the uncorrected dose information P _3. These reception timings are not corrected. Meanwhile, CPU 222, since the interval between the reception time _{t 41} the reception time _{t 5} and the dose information _{P 4} dose information _{P 5} is shorter than the transmission period T, which delay occurs in the reception timing of dose information _{P 4} Judge. The CPU 222 shifts the reception timing of the previously received dose information P ₄ to time t ₄ so that the interval between the reception time of the dose information P _{4 and} the reception time of the dose information P ₅ coincides with the transmission cycle T. The estimated line of the cumulative dose signal Va at is derived to correct the voltage level of the current cumulative dose signal Va. That is, the CPU 222 derives an estimated line when the tilt control by the tilt control signal θ ₄ corresponding to the dose information P ₄ is started from the time t _4, and for adjustment so that the accumulated dose signal Va reaches this estimated line. deriving a tilt control signal theta _m.

FIG. 14 is a diagram illustrating an example of a time transition of the cumulative dose signal Va generated by the interface box 220 according to the second embodiment. In Figure 14, the interface box 220, dose information _{P 1} of the first to be received at time _{t 1} is received at time _{t 11,} 2 nd dose information _{P 2} receives the reception time _{t 2} of the normal The case is shown. In this case, since the interval between the reception time t ₁₁ of dose information P ₁ received and the reception time t ₂ to first dose information P ₂ received the second time is shorter than the transmission interval T of dose information in the electronic cassette 1 , CPU 222 of interface box 220, it is determined that a delay in the reception timing of dose information _{P 1} received the first time has occurred. The analysis of the dose information reception timing may be performed, for example, by referring to a reception time stamp given to the dose information. The CPU 222 shifts the reception time of the dose information P ₁ to t ₁ so that the interval between the reception time of the dose information P _{1 and} the reception time of the dose information P ₂ coincides with the transmission interval T of the dose information. An estimation line (indicated by a broken line in FIG. 14) of the dose signal Va is derived. Slope in the period time t ₁ ~t ₂ such estimation line corresponds to the tilt control signal theta ₁ based on the dose information P ₁ received the first time, the slope in the period time t ₂ ~t ₃ a second time This corresponds to the tilt control signal θ ₂ based on the received dose information P ₂ .

The CPU 222 corrects the inclination during the adjustment period τ _m from time t ₂ to t ₂₁ so that the voltage level of the accumulated dose signal Va in which an error has occurred at the _second dose information reception time t ₂ converges to the estimated line. It generates a control signal theta _m the inclination control of the accumulated dose signals Va to. The CPU 222 derives the adjustment period τ _m and the correction inclination control signal θ _m by calculation so that the voltage level of the accumulated dose signal Va converges on the estimated line.

Such processing, the voltage level of the accumulated dose signals Va at time t ₂₁ is corrected to a proper value reaches the estimated line. The CPU 222 controls the slope of the cumulative dose signal Va by the slope control signal θ ₂ corresponding to the dose information P ₂ received for the second time after the time t ₂₁ when the voltage level of the cumulative dose signal Va becomes an appropriate value.

  In this way, when there is a delay in receiving the dose information wirelessly transmitted from the electronic cassette 1, the interface box 220 reduces the accumulated dose signal Va so as to reduce the error of the accumulated dose signal Va accompanying this communication delay. The tilt control is performed.

  FIG. 15 is a flowchart showing a flow of processing in the inclination control program for performing the inclination control of the cumulative dose signal Va executed by the CPU 222 of the interface box 220 according to the present embodiment. The program is stored in advance in a predetermined area of a storage unit (not shown) of the interface box 220. The program is executed at a predetermined timing when a radiographic image for diagnosis is captured using the imaging pixel 60A.

  In step S41, the CPU 222 determines whether or not dose information has been received from the electronic cassette 1 in the wireless communication unit 221. If reception of dose information is detected, the process proceeds to step S42.

  In step S42, the CPU 222 refers to the reception time stamp given to each of the dose information received before this time and the reception time stamp given to the dose information received this time.

  In step S43, the CPU 222 determines whether or not there is a delay in the reception timing of any of the previously received dose information based on the reception time of the dose information indicated by the reception time stamp referred in step S42. That is, the CPU 222 determines that the interval between the reception time of the nth dose information received this time and the reception time of the mth dose information received earlier is shorter than (n−m) times the transmission period T of dose information. If it is determined, it is determined that there is a delay in the reception timing of the m-th dose information received earlier. The CPU 222 determines the delay of the reception timing for each dose information received before this time, and if a delay is detected in any dose information, the process proceeds to step S44, and otherwise the process is performed. To step S46.

  In step S44, the CPU 222 determines that the interval between the reception time of the m-th dose information determined to be delayed in reception timing in step S43 and the reception time of the n-th dose information received this time is the transmission interval of dose information. The reception timing of the previously received m-th dose information is shifted so as to coincide with (n−m) times T, and an estimated line of the cumulative dose signal Va in this case is derived. That is, an estimation line is derived when the reception time point of the m-th dose information received earlier is shifted to the reception time point at which it is determined that there is no delay.

In step S45, the CPU 222 adjusts the inclination of the adjustment so that the voltage level of the accumulated dose signal Va in which an error has occurred due to the delay in the dose information reception timing converges on the estimated line derived in step S44. A control signal θ _m and an adjustment period τ _m are derived. Thus, the slope of the cumulative dose signal Va may, until adjustment period tau _m from the reception time of this received n-th dose information has elapsed, the control of the gradient corresponding to the gradient control signal theta _m for adjustment, The voltage level of the cumulative dose signal Va reaches the estimated line derived in step S44.

  In step S46, the CPU 222 derives an inclination control signal θ corresponding to the dose information by multiplying the pixel value as the current dose information received in step S41 by a predetermined coefficient α, and the inclination of the accumulated dose signal Va. To control. Thereby, the accumulated dose signal Va traces on the estimated line derived in step S44. That is, the error generated in the accumulated dose signal Va due to the delay in receiving dose information is eliminated.

  In step S <b> 47, the CPU 222 determines whether or not the irradiation of radiation from the radiation generator 210 has stopped. For example, the CPU 222 can detect the radiation irradiation stop by receiving a control signal indicating the radiation irradiation stop supplied from the electronic cassette 1. When the CPU 222 detects that radiation irradiation has been stopped, this routine ends. When it is not detected that radiation irradiation has stopped, the process returns to step S41. That is, the CPU 222 continues to output the accumulated dose signal Va by repeatedly executing the processes of steps S41 to S46 while the radiation generator 210 is irradiated with radiation.

  As described above, in the inclination control of the cumulative dose signal Va in the interface box 220 according to the second embodiment of the present invention, the delay of the reception timing of each dose information received earlier with the reception timing of the latest dose information as a reference. And the estimated line of the accumulated dose signal Va is derived when the reception timing of the received dose information received with a delay is retroactively corrected, and the slope of the accumulated dose signal Va is matched with this estimated line. To control. According to such tilt control, the estimated time line of the accumulated dose signal Va is derived by correcting each received time point of the received dose information with a delay so as to approach the normal reception time as time passes. It becomes possible to further improve the accuracy of the accumulated dose signal Va. As a result, more appropriate automatic exposure control (AEC) can be performed.

  In each of the above embodiments, the case where the dose per unit time of the radiation applied to the electronic cassette 1 is wirelessly transmitted to the interface box 220 as dose information is illustrated, but the present invention is not limited to this. For example, the cumulative dose of radiation applied to the electronic cassette 1 may be intermittently wirelessly transmitted to the interface box 220 as dose information. Further, the estimated time until the radiation irradiation stop calculated based on the radiation dose per unit time may be intermittently wirelessly transmitted to the interface box as dose information.

  Further, in each of the above embodiments, the interface box 220 exemplifies a case where the reception interval of the dose information is derived by referring to the time stamp given to the dose information. However, the reception time of the dose information is identified as the dose information identification. It may be stored in a storage medium in association with a code and read out as appropriate. In the above embodiment, the delay in receiving the dose information is detected by comparing the dose information reception interval and the dose information transmission period T. However, the present invention is not limited to this. . For example, the electronic cassette 1 adds a transmission time stamp indicating the transmission time of the dose information to the dose information and transmits it to the interface box. The interface box receives the transmission time stamp added to the received dose information and the reception The delay at the time of receiving the dose information may be determined by comparing the time stamp.

  Moreover, although each said embodiment illustrated the case where the transmission interval of the dose information wirelessly transmitted from the electronic cassette 1 was constant, the transmission interval of the dose information of dose information may be random. In this case, the electronic cassette 1 associates the transmission time of the dose information with the dose information, and the interface box 220 refers to the transmission time and the reception time of the dose information, thereby receiving the dose information reception timing. Can be determined. In addition, the electronic cassette 1 may attach information indicating a period until the dose information to be transmitted next is transmitted to the dose information to be transmitted this time.

  Further, in the above-described embodiment, the configuration in which the sensor 13B constituting the dose detection pixel 60B is directly connected to the signal wiring 22 is exemplified. However, similarly to the imaging pixel 60A, a TFT is connected to the sensor 13B and the sensor 13B is connected. It is also possible to configure so that the read timing of the charges can be controlled by the gate signal. Further, in the above embodiment, the configuration in which the imaging pixel 60A and the dose detection pixel 60B are connected to the common signal wiring 23 is illustrated, but the signal wiring connected to the imaging pixel 60A and the dose detection pixel 60B are exemplified. It is also possible to use a separate system for the signal wiring connected to.

  In the above embodiment, cassette control such as gate driver control and block organization processing is performed by the CPU 26A, but a predetermined information processing device such as a programmable gate IC such as an FPGA (Field Programmable Gate Array) is used. By loading the program, it can also function as the cassette control unit 26.

  Further, in the above-described embodiment, the sensors 13A and 13B constituting the imaging pixel 60A and the dose detection pixel 60B include an organic photoelectric conversion material that generates charges by receiving light generated by the scintillator 30. However, the present invention is not limited to this, and the sensors 13A and 13B may be configured to include an organic photoelectric conversion material. For example, a semiconductor such as amorphous selenium may be used for the sensors 13A and 13B, and radiation may be directly converted into electric charges.

  Further, in the above embodiment, the case where the dose detection pixel 60B is used for automatic exposure control (AEC) is exemplified, but it can also be used to detect the start of radiation irradiation from the radiation source 211. . As a result, the electronic cassette 1 can detect the radiation irradiation start by itself without receiving the instruction information for instructing the radiation irradiation start from the external device.

  In the above embodiment, the case where X-rays are applied as radiation has been described. However, the present invention is not limited to this, and other radiation such as γ-rays may be applied.

1 Electronic cassette 10 Radiation detectors 13A, 13B Sensor 20 TFT substrate 21 Gate wiring 22 Signal wiring 23 Gate line driver 24 Signal processing unit 26 Cassette control unit 26A CPU
26B memory 27 wireless communication unit 30 scintillator 40 TFT
50 Capacitor 60A Imaging Pixel 60B Dose Detection Pixel 210 Radiation Generator 211 Radiation Source 220 Interface Box 221 Wireless Communication Unit 230 Console

Claims (12)

A radiographic image capturing apparatus that wirelessly transmits dose information indicating the detected radiation dose and radiographically transmitted at a predetermined transmission timing while detecting the irradiated radiation and capturing a radiographic image;
Receiving dose information wirelessly transmitted from the radiographic imaging device, generating a cumulative dose signal indicating a cumulative dose of radiation irradiated to the radiographic imaging device based on each of the received dose information, and the dose An interface device for adjusting the cumulative dose signal so as to reduce an error generated in the cumulative dose signal due to a delay in reception timing of the dose information with respect to a transmission timing of information;
Including radiographic imaging system. The radiographic imaging device wirelessly transmits the dose information at a predetermined transmission cycle,
The radiographic imaging system according to claim 1, wherein the interface device determines a delay in receiving timing of the dose information by comparing a transmission period of the dose information and a reception interval of the dose information in the radiographic imaging device. .   In the interface device, the interval between the reception time of the dose information received at the mth time and the reception time of the dose information received at the nth time after the mth time is (nm) of the transmission period of the dose information. The radiographic imaging system according to claim 2, wherein it is determined that there is a delay in the reception timing of the dose information received at the n-th time when it is longer than twice.   In the interface device, the interval between the reception time of the dose information received at the mth time and the reception time of the dose information received at the nth time after the mth time is (nm) of the transmission period of the dose information. The radiographic imaging system according to claim 2, wherein it is determined that there is a delay in the reception timing of the dose information received at the m-th time when the time is shorter than twice. The radiographic imaging device transmits transmission cycle information indicating a transmission cycle of the dose information to the interface device,
The interface device determines a delay in the reception timing of the dose information by comparing a transmission cycle of the dose information indicated by the received transmission cycle information and a reception interval of the dose information. The radiographic imaging system of Claim 1.   The said interface apparatus has a recording means which records each receiving time of the said dose information, The reception interval of the said dose information is derived | led-out based on the receiving time recorded by the said recording means. Radiation imaging system.   The radiographic imaging system according to claim 6, wherein the recording unit attaches time information indicating a reception time of each dose information to the dose information.   The interface device controls an inclination of the cumulative dose signal based on each of the received dose information, and determines that a delay has occurred in a reception timing of the dose information, the cumulative dose is determined by the delay. The radiographic imaging system according to any one of claims 1 to 7, further comprising control means for controlling an inclination of the accumulated dose signal so as to reduce an error generated in the signal.   When the control means determines that there is a delay in the reception timing of the dose information, the control means shifts the reception time of the dose information received with the delay to a time when it is determined that there is no delay. The radiographic imaging according to claim 8, wherein an estimated line that estimates a time transition of the accumulated dose signal in a case of being inferred is derived, and an inclination of the accumulated dose signal is controlled so that the accumulated dose signal coincides with the estimated line. system.   When the signal level of the cumulative dose signal is excessive due to a delay in the reception timing of the dose information, the control means shifts the signal level of the cumulative dose signal to a constant signal level of the cumulative dose signal. The radiation image capturing system according to claim 9, wherein the radiation image is matched with the estimated line.   The radiation generation device according to any one of claims 1 to 10, further comprising a radiation generation device that stops irradiation of radiation to the radiographic imaging device when it is detected that a signal level of the cumulative dose signal has reached a predetermined value. Radiation imaging system. The radiographic imaging apparatus wirelessly transmits dose information indicating the dose of radiation detected by detecting the radiation applied to the radiographic apparatus at every predetermined transmission timing;
The interface device receives dose information wirelessly transmitted from the radiographic imaging device, and outputs a cumulative dose signal indicating a cumulative dose of radiation irradiated to the radiographic imaging device based on each of the received dose information Steps,
Radiographic imaging including a step of stopping radiation irradiation to the radiographic imaging apparatus when the radiation generation apparatus detects that the signal level of the accumulated dose signal output from the interface apparatus has reached a predetermined value. An automatic exposure control method in a system,
An automatic exposure control method in which the interface device adjusts the cumulative dose signal so as to reduce an error generated in the cumulative dose signal due to a delay in reception timing of the dose information with respect to a transmission timing of the dose information.

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