JP5792569B2 - Radiation imaging system and long imaging method of radiation imaging system - Google Patents

Description

  The present invention relates to a radiation imaging system and a long imaging method of the radiation imaging system.

  In the medical field, X-ray imaging systems using radiation, such as X-rays, are known. The X-ray imaging system includes an X-ray generation apparatus that generates X-rays and an X-ray imaging apparatus that receives an X-ray and captures an X-ray image. The X-ray generator has an X-ray source that irradiates X-rays toward a subject, a radiation source control device that controls driving of the X-ray source, and an irradiation switch for inputting an X-ray irradiation start instruction. ing. An X-ray imaging apparatus is an X-ray image detection apparatus that receives an X-ray transmitted through a subject and detects an X-ray image, and a console that controls driving of the X-ray image detection apparatus and performs various image processing on the X-ray image. have.

  In the recent field of X-ray imaging systems, X-ray image detection apparatuses using a flat panel detector (FPD) as a detection panel are widely used in place of X-ray films and imaging plates (IP). In the FPD, pixels that accumulate signal charges corresponding to the amount of incident X-rays are arranged in a matrix. The FPD accumulates signal charge for each pixel, converts the accumulated signal charge into a voltage signal by a signal processing circuit, detects an X-ray image representing the image information of the subject, and uses this as digital image data Output.

  An electronic cassette (portable X-ray image detection apparatus) in which an FPD is built in a rectangular parallelepiped housing has also been put into practical use. Unlike the type that cannot be removed because the electronic cassette is installed on the photographic stand, it can be used detachably attached to an existing photographic stand for film cassettes and IP cassettes or a dedicated photographic stand. It is used by placing it on a bed or holding it on the subject itself in order to take an image of a particular part. In addition, in order to take pictures of elderly people who are being treated at home or those who are suddenly ill due to accidents, disasters, etc., they may be taken out of hospitals where there is no equipment for taking pictures.

  The X-ray imaging system is provided with a sensor for detecting the X-ray dose that has passed through the subject. When the integrated value of the X-ray dose detected by the sensor reaches a preset threshold value, X-ray irradiation from the X-ray source is stopped. Some perform automatic exposure control (AEC).

  For X-ray imaging, the X-ray source and the X-ray image detection apparatus are fixed at a single position and a single part such as the chest or abdomen is imaged. In some cases, the detection device is moved to capture a plurality of images at each movement position. The latter is called long-length imaging, and is performed mainly for the purpose of observing the condition of the bone of the subject, such as bone age and curvature. Imaging sites include the entire spine that covers the upper body from the lower neck to the waist of the subject, and the entire lower limb that covers the lower body from the waist to the toes.

  In long imaging, an operator such as a radiographer first sets an imaging range according to the physical characteristics of the subject such as height, sitting height, and crotch length. The number of times of imaging is determined based on the imaging range and the size of the X-ray image detection device (imaging surface on which pixels of the detection panel are arranged). Furthermore, the positions of the X-ray source and the X-ray image detection device for each imaging are set so that the imaging surfaces overlap at adjacent imaging positions. Then, imaging is performed a plurality of times while moving the X-ray source and the X-ray image detection apparatus to each imaging position. After imaging, a plurality of X-ray images are synthesized using an overlap area generated by overlapping of imaging surfaces at adjacent imaging positions as a margin, and one long image is generated.

  In long imaging, the imaging range is wide, and parts such as the waist and legs that are extremely different from the body thickness and the area of the unexposed area that is not exposed to X-rays are continuously imaged. It is difficult to control the X-ray dose to the optimum value. In addition, when generating a long image, a smooth continuity is given to the joints (overlapping areas) of a plurality of X-ray images to facilitate interpretation and diagnosis, so that it is unnatural as a single image. It is necessary not to become.

  Therefore, in Patent Document 1, an index value (average value of pixel values, etc.) of overlap areas of individual X-ray images is calculated after long imaging, and the display gradations of the overlap areas are aligned (density variation is adjusted). The tone processing is corrected (to reduce). By specifying an image serving as a reference for gradation processing and correcting gradation processing of other images in a chained manner based on the designated image, the density difference at the joint of the long image is made inconspicuous.

  In Patent Document 2, a subject is photographed with a camera, its contour is extracted, and based on this, an AEC daylighting field for individual photographing of a long photographing is set. The FPD pixel is used as an AEC sensor, and AEC is performed at each photographing position based on signals from pixels existing in the set daylighting field.

JP 2004-057506 A JP2011-139761A

  The invention described in Patent Document 1 has a problem in that it is necessary to correct the gradation processing, and the processing becomes complicated, and it takes time to generate a long image accordingly. Further, although the image density can be changed by correcting the gradation processing, the fundamental image quality itself such as graininess cannot be changed. For this reason, when the X-ray dose of each photographing is not appropriate, there is a possibility that the image will be an unnatural long image with the same density but not uniform graininess.

  In the invention described in Patent Document 2, it is necessary to install a camera only for setting a lighting field, and to extract the contour of the subject from the image of the camera. The complexity and lengthening of time are inevitable.

  The present invention has been made in view of the above problems, and can easily produce a long image suitable for diagnosis with uniform graininess without increasing the scale and cost of the apparatus, complicating the processing, and increasing the time. It is an object of the present invention to provide a radiation imaging system and a long imaging method for the radiation imaging system.

  The radiation imaging system of the present invention stores a radiation source that irradiates a subject with radiation, and receives the radiation transmitted through the subject, accumulates signal charges, and outputs the signal charges to the signal lines in accordance with driving of the switching element. A radiation image detection apparatus having a detection panel in which a plurality of pixels are arranged, and a radiation field that has a light field on substantially the entire imaging surface provided with the pixels of the detection panel, and detects a dose of radiation transmitted through the subject A dose detection sensor that moves the radiation source and the radiation image detection device relative to each other, and divides a long imaging range including a plurality of parts of the subject so that the imaging surfaces partially overlap. In a radiography system that shoots n times within a range of n (n is a natural number of 2 or more), synthesizes n radiation images obtained thereby, and generates and displays a single long image The above Calculated by a dose index value calculation means for calculating a dose index value of an overlap region of the radiographic image generated by dividing a long imaging range so that the imaging surfaces partially overlap, and the dose index value calculation means Threshold setting means for setting an irradiation stop threshold for the k-th imaging based on the k-1th imaging dose index value for the k-1th imaging (k = 2, 3, 4,..., N); When the integrated value of the doses detected by the dose detection sensor existing in the overlap region between the first imaging and the kth imaging reaches the irradiation stop threshold set by the threshold setting means, the radiation of the kth imaging And automatic exposure control means for stopping irradiation of radiation from the source.

  Of the n imaging ranges, the first imaging range and the storage means for storing in advance the lighting field of the dose detection sensor and the irradiation stop threshold of the automatic exposure control means, or of the n imaging ranges It is preferable to provide an operation input means for setting a photographing range for the first photographing, a lighting field of the dose detection sensor, and an irradiation stop threshold value of the automatic exposure control means. The automatic exposure control means is not the irradiation stop threshold set based on the overlap region and the dose index value for the first imaging, but the lighting field and the irradiation stop threshold stored in the storage means, or the operation Automatic exposure control is performed with the lighting field and irradiation stop threshold set by the input means. In the case where the storage means is provided, the imaging range to be imaged for the first time includes the waist, and the area corresponding to the waist is stored in the lighting field.

  The dose index value calculation means calculates a pixel value of the overlap region as a dose index value.

  The dose detection sensor is the pixel directly connected to the signal line without a switching element. The radiological image detection apparatus is an electronic cassette in which the detection panel is housed in a portable housing.

  The long imaging method of the radiation imaging system of the present invention includes a radiation source for irradiating a subject with radiation, a signal charge accumulated by receiving the radiation transmitted through the subject, and a signal charge according to driving of the switching element. A radiological image detection apparatus having a detection panel in which a plurality of pixels are arranged to output to a signal line, and a light field in substantially the entire imaging surface provided with the pixels of the detection panel, and transmitted through the subject A radiation imaging system including a dose detection sensor for detecting a radiation dose, wherein the radiation source and the radiation image detection device are relatively moved so that a long imaging range including a plurality of parts of a subject is captured on the imaging surface Are captured n times in the imaging range (n is a natural number of 2 or more) divided so as to partially overlap, and a single long image is synthesized by synthesizing n radiation images obtained thereby. Generate and display A method of calculating a dose index value for calculating a dose index value of an overlap region of the radiographic image generated by dividing the long imaging range so that the imaging surface partially overlaps And an irradiation stop threshold value of the k-th imaging based on the dose index value of the (k−1) -th imaging (k = 2, 3, 4,..., N) calculated in the dose index value calculating step. A threshold setting step to be set, and an integrated value of the dose detected by the dose detection sensor existing in the overlap region between the (k-1) th imaging and the kth imaging is an irradiation stop threshold set in the threshold setting step And the automatic exposure control step of stopping the irradiation of the radiation from the radiation source in the k-th imaging.

  Since the present invention performs automatic exposure control so that the dose of the overlap region of each image of the long image becomes the same, without increasing the device scale and device cost, making the process complicated and lengthening, A long image suitable for diagnosis with uniform graininess can be easily obtained.

It is the schematic which shows the structure of a X-ray imaging system. It is a figure which shows the internal structure of a radiation source control apparatus, and the connection relation of a radiation source control apparatus and another apparatus. It is a block diagram which shows the internal structure of an electronic cassette. It is a figure for demonstrating arrangement | positioning and the lighting field of the detection pixel of FPD of an electronic cassette. It is a block diagram which shows the internal structure of the AEC part and communication part of an electronic cassette. It is a figure which shows the imaging conditions set to the console. It is a block diagram which shows the internal structure of a console. It is a block diagram which shows the function of a console, and the flow of information. (A) is a figure which shows each imaging position at the time of long imaging | photography, (B) is a figure which shows the image data acquired at each imaging position. It is a figure which shows the lighting field and irradiation stop threshold value of each imaging | photography of long imaging | photography. It is a flowchart which shows the flow of a process of long imaging | photography. It is a flowchart which shows the flow of a process of AEC. It is a figure which shows another aspect of FPD.

  In FIG. 1, an X-ray imaging system 2 includes an X-ray source 10, a radiation source control device 11 for controlling the operation of the X-ray source 10, an irradiation switch 12 for instructing the start of X-ray irradiation, and a subject. An electronic cassette 13 that detects X-rays transmitted through M and outputs an X-ray image, a console 14 that controls operation of the electronic cassette 13 and image processing of the X-ray image, and subjects M are imaged in a standing posture. And a standing photographing stand 15. The X-ray source 10, the radiation source control device 11, and the irradiation switch 12 constitute an X-ray generator, the electronic cassette 13, and the console 14 constitute an X-ray imaging device, respectively. In addition to this, a radiation source moving mechanism 16 for setting the X-ray source 10 in a desired direction and position is provided.

  The X-ray source 10 includes an X-ray tube 17 that emits X-rays, and an irradiation field limiter (collimator) 18 that limits an X-ray irradiation field emitted by the X-ray tube 17 to a rectangular shape. The X-ray tube 17 includes a cathode made of a filament that emits thermoelectrons, and an anode (target) that emits X-rays when the thermoelectrons emitted from the cathode collide. The irradiation field limiter 18 is formed, for example, by arranging a plurality of lead plates that shield X-rays in a grid pattern, and an irradiation opening that transmits X-rays is formed at the center, and is controlled by the radiation source control device 11. The size of the irradiation opening is changed by moving the position of the lead plate to limit the irradiation field.

  The radiation source control device 11 is configured so that the X-ray irradiation field from the irradiation field limiter 18 is such that the X-ray irradiation field substantially coincides with the imaging surface 41 of the FPD 40 of the electronic cassette 13 (see FIG. 3). Hereinafter, the collimator angle is adjusted in two directions: a Z direction perpendicular to the floor surface of the photographing room and an X direction (direction perpendicular to the paper surface) which is the width direction of the imaging surface 41. “Θ” in the figure indicates the collimator angle in the Z direction.

  Further, the radiation source control device 11 drives the radiation source moving mechanism 16 so as to move the X-ray source 11 up and down following the up and down movement in the Z direction of the holder 19 of the upright imaging table 15 during long imaging. To control. The radiation source moving mechanism 16 holds, for example, the X-ray source 10 suspended from the ceiling of the radiographing room, and an arm that can be expanded and contracted in the Z direction, and the arm is attached to move the X-ray source 10 for each arm in the XY direction (Y The direction is made up of a rail that moves in a direction parallel to the floor of the radiographing room and perpendicular to the X direction) and a drive source such as a motor, and is automatically controlled under the control of the radiation source control device 11 or by a radiographer or the like. It is possible to change the position of the X-ray source 10 manually by an operator.

  As shown in FIG. 2, the radiation source control device 11 boosts an input voltage with a transformer to generate a high voltage tube voltage, and supplies the X-ray source 10 through a high voltage cable. Main information and signals of the console 14 that controls the tube voltage that determines the energy spectrum of the X-rays irradiated by the source 10, the tube current that determines the irradiation amount per unit time, and the X-ray irradiation time. And a communication I / F 32 that mediates transmission and reception.

  An irradiation switch 12, a memory 33, and a touch panel 34 are connected to the control unit 31. The irradiation switch 12 is, for example, a two-stage push switch operated by an operator. The irradiation switch 12 generates a warm-up start signal for starting the warm-up of the X-ray source 10 by one-stage push, and the X-ray source by two-stage push. 10 generates an irradiation start signal for starting irradiation. These signals are input to the radiation source control device 11 through a signal cable. The control unit 31 starts power supply from the high voltage generator 30 to the X-ray source 10 when receiving the irradiation start signal from the irradiation switch 12.

  The memory 33 stores several types of imaging conditions such as tube voltage and tube current irradiation time product (mAs value) in advance. The shooting conditions are manually set by the operator through the touch panel 34. The radiation source control device 11 tries to irradiate X-rays with the tube voltage or tube current irradiation time product of the set imaging conditions. When the AEC detects that a necessary and sufficient dose has been reached, the X-ray irradiation is stopped even if it is less than the tube current irradiation time product (irradiation time) to be irradiated on the radiation source control device 11 side. To function. In order to prevent the X-ray irradiation from ending before the target dose is reached and the AEC is determined to stop the irradiation, the imaging conditions of the X-ray source 10 include the current irradiation time product (irradiation). The maximum value is also set.

  The irradiation signal I / F 35 is connected to the electronic cassette 13 when the X-ray irradiation stop timing is defined based on the output of the detection pixel 65 (see FIG. 3) of the electronic cassette 13. In this case, when receiving a warm-up start signal from the irradiation switch 12, the control unit 31 transmits an inquiry signal to the electronic cassette 13 via the irradiation signal I / F 35. When the electronic cassette 13 receives the inquiry signal, it performs preparatory processing such as completion of reset processing and accumulation start processing. Then, an irradiation permission signal, which is a response to the inquiry signal from the electronic cassette 13, is received by the irradiation signal I / F 35, and when an irradiation start signal is received from the irradiation switch 12, the power from the high voltage generator 30 to the X-ray source 10 is received. Start feeding. The control unit 31 stops the power supply from the high voltage generator 30 to the X-ray source 10 when receiving the irradiation stop signal emitted from the electronic cassette 13 by the irradiation signal I / F 35, thereby irradiating the X-ray. Stop.

  As is well known, the electronic cassette 13 includes an FPD 40 and a portable housing (not shown) that houses the FPD 40. The casing of the electronic cassette 13 is substantially rectangular and has a flat shape, and the plane size is the same size as a film cassette or an IP cassette (also called a CR cassette) (a size conforming to the international standard ISO 4090: 2001). is there. For this reason, it can be attached to an existing photographing stand for a film cassette or an IP cassette.

  The electronic cassette 13 is detachably set on the holder 19 of the standing imaging stand 15 so that the imaging surface 41 of the FPD 40 is held in a posture facing the X-ray source 10. The electronic cassette 13 can be used as a single unit by being placed on the bed on which the subject M lies, or held by the subject M itself, instead of being set on the standing imaging stand 15.

  In FIG. 1, the standing imaging stand 15 sets the holder moving mechanism 20 that moves the holder 19 up and down in the Z direction without changing the orientation of the imaging surface 41 of the FPD 40 of the electronic cassette 13 and the imaging range W of the subject M. And an operation unit 21 for performing the operation. The holder moving mechanism 20 can change the position of the holder 19 automatically under the control of the console 14 or manually by an operator. The imaging range W is an example of an imaging range when performing whole spine imaging, and is a range that substantially covers the upper body of the subject M from the neck to the waist.

Operation unit 21 sets a movement button 22 for moving the holder 19 up and down, the first setting button 23 for setting the upper end position Z _T of the imaging range W, the lower end position Z _B of the photographic range W And a second setting button 24.

A first mark 25 indicating the upper end position of the imaging surface 41 of the FPD 40 and a second mark 26 indicating the lower end position of the imaging surface 41 are formed on the side surface of the holder 19 by printing or the like. The operator operates the movement button 22 of the operation unit 21 to move the holder 19 upward, and depresses the first setting button 23 at a desired position, thereby setting the position corresponding to the first mark 25 to the imaging range W. set to the upper end position _{Z T.} Further, by operating the movement button 22 to move the holder 19 downward and pressing the second setting button 24 at a desired position, the position corresponding to the second mark 26 is set to the lower end position Z _{B of the} imaging range W. Set to. Information on the imaging range W set by the operation unit 21 is transmitted to the console 14.

  In FIG. 3, the electronic cassette 13 includes an antenna 42 and a battery 43, and wireless communication with the console 14 is possible. The antenna 42 transmits and receives radio waves for wireless communication to and from the console 14. The battery 43 supplies power for operating each part of the electronic cassette 13. The battery 43 is a relatively small battery that can be accommodated in the thin electronic cassette 13. The battery 43 can be taken out from the electronic cassette 13 and set in a dedicated cradle for charging. The battery 43 may be configured to be capable of wireless power feeding.

  In addition to the antenna 42, the electronic cassette 13 is provided with a socket 44. The socket 44 is provided for wired connection with the console 14, and is used when wireless communication between the electronic cassette 13 and the console 14 becomes impossible due to the remaining amount of the battery 43 being insufficient. When a cable from the console 14 is connected to the socket 44, wired communication with the console 14 becomes possible. At this time, power may be supplied from the console 14 to the electronic cassette 13.

  The antenna 42 and the socket 44 are provided in the communication unit 45. The communication unit 45 transmits and receives various types of information and signals including image data between the antenna 42 or the socket 44 and the control unit 46 and the memory 47 (such as a life check signal for checking whether or not communication is normally performed). Mediate.

  The FPD 40 includes a TFT active matrix substrate, and includes an imaging surface 41 formed by arranging a plurality of pixels 50 that accumulate signal charges corresponding to the amount of incident X-rays on the substrate. The plurality of pixels 50 are two-dimensionally arranged in a matrix of i rows (X direction) × j columns (Z direction) at a predetermined pitch.

  The FPD 40 further includes a scintillator (phosphor, not shown) that converts X-rays into visible light, and is an indirect conversion type in which visible light converted by the scintillator is photoelectrically converted by the pixels 50. The scintillator is made of CsI (cesium iodide), GOS (gadolinium oxysulfide), or the like, and is disposed so as to face the entire surface of the imaging surface 41 on which the pixels 50 are arranged. Note that the scintillator and the FPD 40 may be a PSS (Penetration Side Sampling) system in which the scintillator and the FPD 40 are arranged in this order when viewed from the X-ray incident side, or conversely, an ISS (Irradiation Side Sampling) arranged in the order of the FPD 40 and the scintillator. The method may be used. Alternatively, a direct conversion type FPD using a conversion layer (such as amorphous selenium) that directly converts X-rays into charges may be used without using a scintillator.

  The pixel 50 includes a photodiode 51 that is a photoelectric conversion element that generates charges (electron-hole pairs) upon incidence of visible light, a capacitor (not shown) that accumulates charges generated by the photodiode 51, and a switching element. A thin film transistor (TFT) 52 is provided.

  The photodiode 51 has a structure in which a semiconductor layer (for example, PIN type) that generates electric charge and an upper electrode and a lower electrode are arranged above and below the semiconductor layer. In the photodiode 51, a TFT 52 is connected to the lower electrode, and a bias line 53 is connected to the upper electrode. The bias lines 53 are provided by the number of rows (i rows) of the pixels 50 in the imaging surface 41. 54. The connection 54 is connected to a bias power supply 55. A bias voltage Vb is applied from the bias power supply 55 to the upper electrode of the photodiode 51 through the connection line 54 and the bias line 53. An electric field is generated in the semiconductor layer by application of the bias voltage Vb, and charges (electron-hole pairs) generated in the semiconductor layer by photoelectric conversion are applied to the upper and lower electrodes, one having a positive polarity and the other having a negative polarity. The electric charge is accumulated in the capacitor.

  The TFT 52 has a gate electrode connected to the scanning line 56, a source electrode connected to the signal line 57, and a drain electrode connected to the photodiode 51. The scanning lines 56 and the signal lines 57 are wired in a grid pattern, the scanning lines 56 are as many as the number of rows of the pixels 50 in the imaging surface 41 (i rows), and the signal lines 57 are as many as the number of columns of the pixels 50 (j columns). Min) each is provided. The scanning line 56 is connected to the gate driver 58, and the signal line 57 is connected to the signal processing circuit 59.

  The gate driver 58 drives the TFT 52 to accumulate a signal charge corresponding to the incident amount of X-rays in the pixel 50, a read (main reading) operation for reading the signal charge from the pixel 50, and a reset (empty reading). ) Make an action. The control unit 46 controls the start timing of each of the operations executed by the gate driver 58.

  In the accumulation operation, the TFT 52 is turned off, and signal charges are accumulated in the pixel 50 during that time. In the reading operation, gate pulses G1 to Gi for sequentially driving the TFTs 52 in the same row are generated in sequence from the gate driver 58, the scanning lines 56 are sequentially activated one by one, and the TFTs 52 connected to the scanning lines 56 are sequentially supplied. Turn on. The charge accumulated in the capacitor of the pixel 50 is read out to the signal line 57 and input to the signal processing circuit 59 when the TFT 52 is turned on.

  Dark charges are generated in the semiconductor layer of the photodiode 51 regardless of whether or not X-rays are incident. This dark charge is accumulated in the capacitor because the bias voltage Vb is applied. Since the dark charge generated in the pixel 50 becomes a noise component for the image data, a reset operation is performed to remove this. The reset operation is an operation for sweeping out dark charges generated in the pixels 50 through the signal line 57.

  The reset operation is performed by, for example, a sequential reset method in which the pixels 50 are reset row by row. In the sequential reset method, similarly to the signal charge reading operation, gate pulses G1 to Gi are sequentially generated from the gate driver 58 to the scanning line 56, and the TFTs 52 of the pixels 50 are turned on line by line. While the TFT 52 is on, dark charge flows from the pixel 50 to the integrating amplifier 60 through the signal line 57. In the reset operation, unlike the read operation, the charge accumulated in the integrating amplifier 60 by the multiplexer (MUX) 61 is not read, and the reset pulse RST is generated from the control unit 46 in synchronization with the generation of the gate pulses G1 to Gi. Is output, and the integrating amplifier 60 is reset.

  Instead of the sequential reset method, multiple rows of array pixels are grouped as a group, and the reset is performed sequentially within the group, and the dark charge of the number of rows in the group is simultaneously discharged. An all-pixel reset method that simultaneously sweeps out the dark charges may be used. The reset operation can be speeded up by a parallel reset method or an all-pixel reset method.

  The signal processing circuit 59 includes an integrating amplifier 60, a MUX 61, an A / D converter 62, and the like. The integrating amplifier 60 is individually connected to each signal line 57. The integrating amplifier 60 includes an operational amplifier and a capacitor connected between the input and output terminals of the operational amplifier, and the signal line 57 is connected to one input terminal of the operational amplifier. The other input terminal of the integrating amplifier 60 is connected to the ground (GND). The integrating amplifier 60 integrates the charges input from the signal line 57, converts them into voltage signals D1 to Dj, and outputs them. The MUX 61 is connected to the output terminal of the integrating amplifier 60 in each column via an amplifier 63 and a sample hold (S / H) unit 64. An A / D converter 62 is connected to the output side of the MUX 61.

  The MUX 61 selects one integration amplifier 60 in order from the plurality of integration amplifiers 60 connected in parallel, and serially inputs the voltage signals D1 to Dj output from the selected integration amplifier 60 to the A / D converter 62. . The A / D converter 62 converts the input voltage signals D1 to Dj into digital data and outputs the digital data to the memory 47 built in the electronic cassette 13. An amplifier may be connected between the MUX 61 and the A / D converter 62.

  When the voltage signals D1 to Dj for one row are read from the integrating amplifier 60 by the MUX 61, the control unit 46 outputs a reset pulse RST to the integrating amplifier 60 and turns on the reset switch 60a of the integrating amplifier 60. As a result, the signal charge for one row accumulated in the integrating amplifier 60 is reset. When the integrating amplifier 60 is reset, the gate pulse of the next row is output from the gate driver 58, and reading of the signal charges of the pixels 50 of the next row is started. These operations are sequentially repeated to read out the signal charges of the pixels 50 in all rows.

  When the reading of all rows is completed, image data representing an X-ray image for one screen is recorded in the memory 47. This image data is read from the memory 47 and output to the console 14 through the communication unit 45. In this way, an X-ray image of the subject M is detected.

  The control unit 46 causes the FPD 40 to perform a reset operation at the timing of receiving the inquiry signal from the control unit 31 of the radiation source control device 11 and returns an irradiation permission signal to the radiation source control device 11. Then, at the timing when the irradiation start signal is received, the operation of the FPD 40 is shifted from the reset operation to the accumulation operation.

  In addition to the pixels 50 connected to the signal line 57 via the TFT 52 as described above, the FPD 40 includes a plurality of detection pixels 65 short-circuited to the signal line 57 not connected to the TFT 52 in the same imaging surface 41. ing. The detection pixel 65 is a pixel that is used to detect the dose of X-rays that pass through the subject M and enter the imaging surface 41, and functions as an irradiation start detection sensor, an irradiation end detection sensor, and an AEC sensor. Function as. The detection pixels 65 occupy about several percent of the pixels 50 in the imaging surface 41.

  As shown in FIG. 4, the detection pixels 65 follow a waveform trajectory 66 indicated by a dotted line symmetrical with respect to the center of the imaging surface 41 so that the detection pixels 65 are evenly scattered in the imaging surface 41 without being locally biased in the imaging surface 41. Is provided. The detection pixels 65 are provided one by one in the column of the pixels 50 to which the same signal line 57 is connected, and the columns in which the detection pixels 65 are provided are provided by sandwiching, for example, two to three columns in which the detection pixels 65 are not provided. It is done. The position of the detection pixel 65 is known at the time of manufacturing the FPD 40, and the FPD 40 stores the positions (coordinates) of all the detection pixels 65 in a nonvolatile memory (not shown) in advance. The arrangement of the detection pixels 65 shown here is an example, and can be changed as appropriate.

  Since the detection pixel 65 is not provided with the TFT 52 between the signal line 57 and is directly connected to the signal line 57, the signal charge generated in the detection pixel 65 is immediately read out to the signal line 57. The same applies to the normal pixel 50 in the same column even when the TFT 52 is turned off and the signal charge is being accumulated. For this reason, the charge generated in the detection pixel 65 always flows into the integration amplifier 60 on the signal line 57 to which the detection pixel 65 is connected. During the accumulation operation, the charge from the detection pixel 65 accumulated in the integration amplifier 60 is output to the A / D converter 62 as a voltage value via the MUX 61 at a predetermined sampling period.

  In FIG. 3, the AEC unit 67 is driven and controlled by the control unit 46. The AEC unit 67 acquires a voltage value (referred to as an AEC detection signal) from the signal line 57 to which the detection pixel 65 is connected via the A / D converter 62.

  5, the AEC unit 67 includes a lighting field selection circuit 75, an integration circuit 76, a comparison circuit 77, and a threshold value generation circuit 78. The lighting field selection circuit 75 selects which detection pixel 65 uses the AEC detection signal for AEC among the plurality of detection pixels 65 scattered in the imaging surface 41 based on the lighting field information from the console 14. The integration circuit 76 integrates the AEC detection signals from the detection pixels 65 selected by the lighting field selection circuit 75. The comparison circuit 77 starts monitoring the integrated value of the AEC detection signal from the integration circuit 76 when the start of X-ray irradiation is detected. Then, the integrated value and the irradiation stop threshold given from the threshold generation circuit 78 are compared at an appropriate timing. When the integrated value reaches the threshold value, the comparison circuit 77 outputs an irradiation stop signal.

  The communication unit 45 is provided with an irradiation signal I / F 80 in addition to the antenna 42 and the socket 44 described above. The irradiation signal I / F 35 of the radiation source control device 11 is connected to the irradiation signal I / F 80. The irradiation signal I / F 80 receives an inquiry signal, transmits an irradiation permission signal in response to the inquiry signal, and outputs a comparison circuit 77, that is, an irradiation stop signal.

  The console 14 is communicably connected to the electronic cassette 13 by a wired method or a wireless method, and controls the operation of the electronic cassette 13. Specifically, the imaging conditions are transmitted to the electronic cassette 13 to set the signal processing conditions of the FPD 40 (such as the gain of an amplifier that amplifies the voltage corresponding to the accumulated signal charge) and the electronic cassette 13. Controls such as turning on / off the power of the camera, switching the mode to a power saving mode, and a shooting preparation state are performed.

  The console 14 performs various image processing such as offset correction, gain correction, and defect correction on the X-ray image data transmitted from the electronic cassette 13. In the defect correction, the pixel value of the column with the detection pixel 65 is interpolated with the pixel value of the column without the adjacent detection pixel 65. The image-processed X-ray image is displayed on the display 89 (see FIG. 7) of the console 14, and the data is connected to the storage device 87 and the memory 86 (both see FIG. 7) in the console 14, or connected to the console 14 via a network. Stored in a data storage such as a stored image storage server.

  The console 14 receives an input of an examination order including information such as a patient's sex, age, imaging region, and imaging purpose, and displays the examination order on the display 89. The examination order is input from an external system that manages patient information such as HIS (Hospital Information System) and RIS (Radiation Information System) and examination information related to radiation examination, or is manually input by an operator. The examination order includes imaging parts such as the head, chest, abdomen, whole spine, all lower limbs, front, side, oblique, PA (X-ray irradiation from the back of the subject M), AP (X-ray subject) The shooting direction such as irradiation from the front of M) is included. The operator confirms the contents of the inspection order on the display 89 and inputs imaging conditions corresponding to the contents through the operation screen of the display 89.

  As shown in FIG. 6, the console 14 can set imaging conditions for each imaging region. In the imaging condition, an illumination stop threshold value for determining whether to stop X-ray irradiation in comparison with the daylighting field of the detection pixel 65 and the integrated value of the AEC detection signal of the detection pixel 65 is stored. Information on this shooting condition is stored in the storage device 87. The lighting field a of the detection pixel 65 in the whole spine imaging is an area of about 3/5 in the lower side indicated by the dashed line hatching in FIG. 4, and the lighting field b in the whole leg imaging is about 3/5 in the upper side shown by the solid line hatching. These areas are set as regions, and both are portions corresponding to the waist portion of the first photographing. After the second shooting, the daylighting field becomes the overlap area 110 (see FIG. 9), so only the daylighting field is set. Here, only the entire spine and all lower limbs of the long image are illustrated as the imaging parts, but actually other imaging parts such as the chest AP, the chest PA, the head, and the abdomen and the imaging conditions corresponding to them are also provided. It is remembered.

  In FIG. 7, the computer constituting the console 14 includes a CPU 85, a memory 86, a storage device 87, a communication I / F 88, a display 89, and an input device 90. These are interconnected via a data bus 91.

  The storage device 87 is, for example, an HDD (Hard Disk Drive). The storage device 87 stores a control program and application program (hereinafter referred to as AP) 92. The AP 92 is a program for causing the console 14 to execute various functions relating to X-ray imaging such as examination order and X-ray image display processing, X-ray image processing, and setting of imaging conditions.

The memory 86 is a work memory for the CPU 85 to execute processing. The CPU 85 centrally controls each part of the computer by loading the control program stored in the storage device 87 into the memory 86 and executing processing according to the program. The communication I / F 88 is a network interface that performs wireless or wired transmission control with external devices such as the RIS, HIS, image storage server, and electronic cassette 13. The input device 90 is a keyboard, a mouse, or a touch panel integrated with the display 89. Input device 90, and when setting the photographing conditions, the distance from the position _{Y 0} of the imaging surface 41 of the FPD40 to the position _{Y 1} of the focus of the X-ray tube 17; inputting the (SID Source Image Distance, see FIG. 1) It is operated when.

  In FIG. 8, when the CPU 85 of the console 14 activates the AP 92 and selects long shooting, the drive condition setting unit 100, the drive control unit 101, the cassette control unit (corresponding to the threshold setting unit) 102, the dose index value calculation unit 103, an image processing unit 104, and a display control unit 105. The drive condition setting unit 100 sets the movement range of the holder 19 and the X-ray source 10 during long imaging, the imaging position within the movement range, and the collimator angle by the irradiation field limiter 18. The drive control unit 101 drives the radiation source moving mechanism 16 and the irradiation field limiter 18 via the radiation source control device 11 according to various driving conditions set by the driving condition setting unit 100, and the holder moving mechanism 20. Drive. The image processing unit 104 collects image data obtained at each shooting position of long shooting in addition to the above-described various image processing such as offset correction, gain correction, defect correction, and the like, and synthesizes them to generate a long image. Create image data. The display control unit 105 causes the display 89 to display a composite X-ray image (long image) based on the long image data, an operation menu necessary for imaging, and the like.

  The driving condition setting unit 100 sets a moving range setting unit 106 that sets the moving range of the holder 19 and the X-ray source 10, a collimator angle setting unit 107 that sets a collimator angle, and sets an imaging position within the moving range. The photographing position setting unit 108 is configured.

The movement range setting unit 106 sets the upper end and lower end positions Z _T and Z _B of the imaging range W input from the operation unit 21 as the movement ranges of the holder 19 and the X-ray source 10. For full spine imaging, holder moving mechanism 20, the position where the height of the second mark 26 of the holder 19 coincides with the lower end position Z _B and movement start position, the height of the first mark 25 is in the upper end position Z _T The holder 19 is moved between the movement start position and the movement end position with the matching position as the movement end position. If from the waist of the total leg imaging to the imaging range W to toe, opposite to the movement start position the position where the height of the first mark 25 matches the upper end position Z _T, the height of the second mark 26 is the lower end position the position corresponding to Z _B and movement end position. Therefore, in both the whole spine photography and all the lower limb photography, the lumbar region is the first part to be photographed. Similarly, the radiation source moving mechanism 16 moves the X-ray source 10 between the movement start position and the movement end position so as to interlock with the holder 19.

The collimator angle setting unit 107 calculates a collimator angle based on the SID input via the input device 90 and the size (known) of the imaging surface 41 of the FPD 40. When the length of the imaging surface 41 in the Z direction is FOV (see FIG. 9), the collimator angle θ with respect to the Z direction is obtained by the following equation (1). The collimator angle with respect to the X direction can be calculated in the same manner.
θ = 2 × tan ⁻¹ {(FOV / 2) / SID} Expression (1)

  Since the movement of the holder 19 and the X-ray source 10 is performed in conjunction with each other, the positional relationship between the holder 19 and the X-ray source 10 at each imaging position does not change. For this reason, the collimator angle θ obtained by the above equation (1) is commonly applied to each photographing position. The radiation source control device 11 drives the irradiation field limiter 18 so that the collimator angle θ becomes the value obtained by the above equation (1).

Photographing position setting unit 108, the distance between the upper end position Z _T and the lower end position Z _B, based on the Z-direction length FOV of the imaging surface 41, to set each imaging position at the time of a long shot. Specifically, first, the following formula (2)
(Z _T -Z _B ) / FOV (2)
Calculate Then, in order to overlap the imaging surfaces 41 at adjacent imaging positions, the number of times of imaging n is calculated by adding 1 to the quotient when the calculation result of the above equation (2) is divisible and rounding up after the decimal point when it is not divisible. Once you have determined the number of photographing times n, as shown in FIG. 9 (A), the height of the second mark 26 is the lower end position Z _B to the movement start position matching (first-time photographing position) P1, the first mark 25 (for all spine imaging, the reverse is the case of all lower extremity imaging) height movement end position corresponding to the upper end position Z _T (n-th photographing position) define a Pn, movement end position between the movement start position P1 Pn Positions equally divided by (n−1) are defined as other imaging positions.

For example, in the case of Z _T −Z _B = 100 cm and FOV = 25 cm, since it is divisible by (Z _T −Z _B ) / FOV = 4, the number of times of photographing n is calculated as 4 + 1 and “5”. The distance d between the photographing positions P1, P2, P3, P4, and P5 is 18.75 cm. When Z _T −Z _B = 100 cm and FOV = 30 cm, it is not divisible by (Z _T −Z _B ) /FOV=3.33... . The distance d between the photographing positions P1, P2, P3, and P4 is approximately 23.3 cm.

FIG. 9B shows image data I1, I2,..., In obtained at the respective photographing positions P1, P2,. In the image data with adjacent shooting positions, an overlap region 110 is generated due to the overlap of the imaging surfaces 41 at the adjacent shooting positions. The overlap region 110 serves as a daylighting field for the detection pixel 65 after the second shooting, and also serves as a glue margin when the image processing unit 104 generates long image data. The overlap amount γ of the overlap region 110 is calculated by the following equation (3).
γ = {n × FOV− (Z _T −Z _B )} / (n−1) (3)
When Z _T −Z _B = 100 cm and FOV = 25 cm, γ = (5 × 25−100) /2=12.5 cm, Z _T −Z _B = 100 cm, and FOV = 30 cm, γ = (4 × 30-100) /3≈6.7 cm.

  The shooting position setting unit 108 outputs information on the calculated number of shootings n and the interval d between the shooting positions to the drive control unit 101. Under the control of the drive controller 101, the holder moving mechanism 20 and the radiation source moving mechanism 16 sequentially move the holder 19 and the X-ray source 10 from the imaging positions P1 to Pn in the Z direction at intervals d. At each imaging position, the focal point of the X-ray tube 17 is located on an extension of a perpendicular drawn from the center of the imaging surface 41 in the Y direction. After the second imaging, the radiation source control device 11 controls the driving of the X-ray source 10 so that X-rays are emitted when the X-ray source 10 moves to each imaging position and stops.

  Further, the imaging position setting unit 108 outputs information on the calculated overlap amount γ of the overlap region 110 to the cassette control unit 102, the image processing unit 104, and the dose index value calculation unit 103. The image processing unit 104 generates long image data by connecting the image data at each photographing position in the overlap region 110 based on the information on the overlap amount γ.

  The dose index value calculation unit 103 receives image data at each imaging position from the image processing unit 104 every time imaging is performed at each imaging position. Then, an area of image data corresponding to the overlap area 110 is specified based on the information on the overlap amount γ from the imaging position setting unit 108. The dose index value calculation unit 103 calculates a dose index value of an area corresponding to the identified overlap area 110. The dose index value may be any value as long as it represents the dose of X-rays incident on the overlap region 110, and is obtained by analyzing the average value of the pixel values in the region corresponding to the overlap region 110 or image data by histogram analysis. A known dose index value such as an S value, an EI value, or a REX value can be used.

  The dose index value calculation unit 103 converts the calculated dose index value into an AEC irradiation stop threshold value, and outputs the conversion result to the cassette control unit 102. The conversion formula between the dose index value and the irradiation stop threshold value is stored in the storage device 87 in advance, and the dose index value calculation unit 103 reads the conversion formula from the storage device 87 and converts the dose index value into the irradiation stop threshold value.

  The cassette control unit 102 provides the electronic cassette 13 with information on the lighting field and the irradiation stop threshold set in the shooting conditions stored in the storage device 87 in the first shooting of the long shooting. In the case of whole spine imaging, information on the lighting field a and the irradiation stop threshold th1 is shown in the lowermost part of FIG. 10, and in the case of all lower limb imaging, information on the lighting field b and the irradiation stop threshold th2. Specifically, the lighting field information is represented by plane coordinates corresponding to the position in the imaging surface 41 of the pixel 50 (including the detection pixel 65), where the coordinate of the upper left pixel 50 is the origin (0, 0). When the lighting field is rectangular, for example, it is represented by coordinates of two points connected by a diagonal line.

After the second imaging, the cassette control unit 102 provides the electronic cassette 13 with the overlap region 110 as information on the lighting field and the irradiation stop threshold output from the dose index value calculation unit 103 as information on the irradiation stop threshold. That is, as shown in the uppermost part of FIG. 10, in the k-th shooting (k = 2, 3, 4,..., N), the overlap region 110 (OL) with the shooting range of the k−1th shooting is obtained. _{k−1, k} ) becomes the daylighting field, and the irradiation stop threshold th _Rk−1 converted from the dose index value R _{k−1 of the} overlap region 110 in the _k− 1th imaging is set as the AEC irradiation stop threshold. . Therefore, AEC is performed so that the X-ray dose incident on the overlap region 110 is the same between the (k-1) th imaging and the kth imaging. Since FIG. 10 shows an example of whole spine imaging, the imaging position moves from the waist of the first imaging toward the upper side (neck side). The opposite is true when photographing all lower limbs.

  The lighting field selection circuit 75 selects a lighting field for each shooting in the long shooting based on the lighting field information provided from the cassette control unit 102. Further, the threshold generation circuit 78 changes the irradiation stop threshold for each shooting in the long shooting based on the information on the irradiation stop threshold provided by the cassette control unit 102.

  Next, with reference to the flowcharts of FIGS. 11 and 12, a processing procedure in the case of performing long imaging (all spine imaging) in the X-ray imaging system 2 will be described.

First, after the X-ray source 10 and the standing imaging stand 15 are arranged at appropriate positions for imaging, the SID is measured and this value is consoled by the input device 90 as shown in step 10 (S10) of FIG. 14 Subsequently, the subject M is placed at a predetermined position in front of the standing imaging stand 15, and in this state, the movement button 22 of the operation unit 21 is operated, and the first of the holder 19 is placed on the upper end of the imaging range W of the subject M to be desired. set the upper end position Z _T by pressing the first setting button 23 by aligning one mark 25, the second align the second mark 26 on the lower end of the imaging range W of the patient M to a desired setting the lower end position _{Z B} by pressing the setting button 24 (S11).

  A position sensor comprising a potentiometer or the like for detecting the horizontal position of the X-ray source 10 or the standing imaging stand 15 is provided when the SID has not been changed and has already been input, and the SID can be automatically calculated based on the output of the position sensor. In this case, the procedure of S10 may be omitted.

Measurement values of SID, and the upper end position setting value _{Z T} and the lower end position _{Z B} is input to the driving condition setting unit 100. In the drive condition setting unit 100, the movement range, collimator angle θ, the number of times of shooting n, the shooting positions P 1, P 2,. .., Pn and the interval d, and the overlap amount γ of the overlap region 110 are calculated (S12). These pieces of information are output to the drive control unit 101 and the like.

  Next, under the control of the drive control unit 101, the radiation source moving mechanism 16 and the holder moving mechanism 20 are driven, and the X-ray source 10 and the holder 19 are moved to the first imaging position P1. Further, the irradiation field limiter 18 is driven by the radiation source control device 11, and the irradiation field is adjusted to be the collimator angle θ calculated by the collimator angle setting unit 107 (S13).

Thereafter, the X-ray imaging system 10 enters a standby state for an irradiation start instruction (S14). When the irradiation switch 12 is operated by the operator and an irradiation start instruction is given (YES in S14),
X-ray irradiation is started from the X-ray source 10, and accordingly, the FPD 40 starts a charge accumulation operation, and the first imaging is performed (S15).

  In the electronic cassette 13, AEC based on the output of the detection pixel 65 is performed in the AEC unit 67 simultaneously with the accumulation operation of the FPD 40. As shown in FIG. 12, the lighting field selection circuit 75 performs AEC detection of a plurality of detection pixels 65 input from the A / D converter 62 based on the lighting field information provided from the cassette control unit 102 of the console 14. Among the signals, the AEC detection signal from the detection pixel 65 existing in the lighting field (lighting field a in the first shooting) is selected, and the selected AEC detection signal is output to the integration circuit 76 (S30). The integrating circuit 76 integrates the detection signals (S31).

  The threshold generation circuit 78 generates an irradiation stop threshold (irradiation stop threshold th1 in the first imaging) given from the cassette control unit 102, and outputs this to the comparison circuit 77. The comparison circuit 77 compares the integrated value of the detection signal from the integration circuit 76 with the irradiation stop threshold value from the threshold value generation circuit 78 (S32), and when the integrated value reaches the threshold value (YES in S33), the irradiation stop signal. Is output. The irradiation stop signal output from the comparison circuit 77 is transmitted toward the irradiation signal I / F 35 of the radiation source controller 11 via the irradiation signal I / F 80 (S34).

  When receiving the irradiation stop signal with the irradiation signal I / F 35, in the radiation source control device 11, the power supply from the high voltage generator 30 to the X-ray source 10 is stopped by the control unit 31, whereby X-ray irradiation is performed. Stopped. In the electronic cassette 13, the operation of the FPD 40 shifts from the accumulation operation to the read operation, and image data is output by this read operation.

The image data output from the FPD 40 is wired or wirelessly transmitted to the console 14 via the communication unit 45 and subjected to various image processing by the image processing unit 104. In the first shooting, image data I1 is acquired (S16 in FIG. 11). The image data I1 is sent from the image processing unit 104 to the dose index value calculation unit 103. In dose index value calculating section 103, the dose indicator value R ₁ of the first time overlap region OL _{1, 2} of the second time imaging is calculated from the image data I1. Then,該線amount index value _{R 1} is converted into illumination stop threshold value _{th R1} (S17).

After the first imaging, the X-ray source 10 and the holder 19 are moved to the second imaging position P2 (S18), and the second imaging is performed at the imaging position P2 (S19). In this case, the AEC section 67, the overlap region _{OL 1, 2} of the detection field is first time and second time imaging, the irradiation stop threshold value is set to _{th R1} same process as S30~S34 in FIG 12 is performed.

In the same manner, the image data Ik-1 is acquired in the k-1th imaging (S20), and the dose index value of the overlap region OLk _{-1, k with} the _kth imaging of the image data Ik-1 is acquired. R _k-1 is calculated by the dose index value calculation unit 103 and converted to an irradiation stop threshold th _Rk-1 (S21). Then, the X-ray source 10 and the holder 19 are moved to the k-th imaging position Pk (S22), and the daylighting field is overlapped with the k-1 and k-th imaging overlap areas OL _{k-1, k} , the irradiation stop threshold. _Is taken as th _Rk-1 and the k _- th shooting is performed (S23), thereby obtaining image data Ik (S24). These processes are continued until the number of photographing is n (k = n, YES in S25).

  After the n-th shooting, the image processing unit 104 connects the image data I1, I2,..., In obtained at the shooting positions P1, P2,. A compositing process is performed to make the long image data for one sheet (S26). The generated long image data is displayed on the display 89 by the display control unit 105 (S27).

  As described above, according to the present invention, since the AEC is performed so that the incident dose of the overlap region 110 in each shooting of the long shooting is the same, the graininess of the joint of the long image is uniform, A long image that is easy to diagnose can be provided.

  In the first shooting, AEC is performed with the pre-stored lighting field and the irradiation stop threshold, so that the optimum image quality can be ensured in the first shooting. Since this state is inherited to some extent after the subsequent second shooting, it is possible to obtain a long image with good overall image quality and unnatural synthesis.

  As image processing, only the dose index value needs to be calculated. Moreover, since the calculation is performed during imaging rather than after imaging, it does not take time to generate a long image. Further, since the daylighting field is stored in advance or limited to the overlap area 110, the daylighting field can be selected easily and quickly.

  The present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted without departing from the gist of the present invention.

  In the above-described embodiment, the region that is imaged for the first time using the pre-stored lighting field and the irradiation stop threshold is the lumbar region for both the entire spine and the entire lower limbs. The reason for this is that the lumbar region has the pelvis and is likely to be the most notable part at the time of diagnosis. However, the present invention is not limited to this, and a part other than the waist may be photographed for the first time. Further, the operator may set the part to be imaged for the first time, its lighting field and the irradiation stop threshold value via the input device 90 or the like. For example, when knee arthropathy is examined by photographing all lower limbs, the knee is the first part to be imaged, and the area of both knee joints of the human body diagram displayed on the display 89 by setting the range of the mouse and touch pen is set as the lighting field To do.

  Instead of the first and second marks 25 and 26 in the above embodiment, a sighting device that emits a visible light beam or a laser beam in the Y direction is provided at the position of the holder 19 corresponding to the upper end position and the lower end position of the imaging surface 41. The imaging range W may be set using the beam irradiation position as a guide. Alternatively, a configuration may be adopted in which the imaging range W is actually measured with a ruler and an actual value is input from the input device 90 without providing an sighting device or the like.

  When the ratio of the overlap amount γ of the overlap region 110 to the length FOV in the Z direction of the imaging surface 41 increases, the exposure amount of the subject M increases in the overlap region 110, and thus an upper limit is set for the overlap amount γ. (Eg, 10% length of FOV) is preferred. Then, the overlap amount γ calculated using the above equation (3) is compared with a predetermined upper limit value. When the overlap amount γ is larger than the upper limit value, each photographing position P1 is set so that the overlap amount γ becomes the upper limit value. , P2,..., Pn are evenly shifted in the vertical direction.

  Alternatively, the overlap amount γ may always be a constant value. In this case, the imaging surface 41 may protrude from the imaging range W in the n-th imaging. In this case, the X-ray irradiation field is limited to the upper end or the lower end of the imaging range W.

  In the above-described embodiment, the pixel 50 for image detection and the detection pixel 65 serving as an AEC sensor exist independently from each other. Therefore, the pixel value of a column with a detection pixel 65 is the pixel value of a column with no adjacent detection pixel 65. It is necessary to perform defect correction to be interpolated. For this reason, the image quality of the X-ray image may be degraded. Therefore, the defect correction is not necessary by configuring the FPD like the FPD 150 shown in FIG.

  In FIG. 13, the FPD 150 includes a first pixel 151 dedicated to image detection and a second pixel 152 for image detection and AEC. The first and second pixels 151 and 152 are arranged in a matrix at an appropriate ratio like the pixel 50 and the detection pixel 65 in the above embodiment. The first and second pixels 151 and 152 have two photodiodes 153 and 154, respectively. The photodiodes 153 and 154 of the first pixel 151 are connected in parallel, and one end is connected to the signal line 57 via the TFT 52. On the other hand, the photodiode 153 of the second pixel 152 is connected at one end to the signal line 57 via the TFT 52 similarly to the first pixel 151, but the photodiode 154 is directly connected to the signal line 57 without passing through the TFT 52. ing. That is, the photodiode 154 of the second pixel 152 has the same configuration as the detection pixel 65 of the above embodiment.

  The charges accumulated in the two photodiodes 153 and 154 are read from the first pixel 151. On the other hand, only the charges accumulated in the photodiode 153 are read from the second pixel 152. Since the photodiode 154 does not contribute to the generation of the X-ray image because the photodiode 154 is used for AEC, the second pixel 152 has a larger amount of accumulated charge than the first pixel 151 at the same incident dose when the opening areas of the photodiodes 153 and 154 are the same. Although it is substantially halved, the pixel value cannot be obtained from the location of the detection pixel 65, and the image quality deterioration of the X-ray image can be suppressed as compared with the above-described embodiment in which only defect correction is performed. A coefficient or the like corresponding to the pixel value of the first pixel 151 when the pixel value of the second pixel 152 is multiplied based on the opening areas of the photodiodes 153 and 154 is obtained in advance, and the coefficient is output to the output of the second pixel 152. If the correction is performed by multiplying by X, an X-ray image can be generated without performing defect correction, and the adverse effect on the image quality of the X-ray image due to the use of some of the pixels constituting the FPD for AEC is almost complete. Can be eliminated.

  In the above-described embodiment, the case of standing imaging in which the holder 19 is moved in the vertical direction with respect to the subject M in the standing posture has been described as an example, but the present invention is not limited to this, and the present invention is not limited to this. The present invention can also be applied to the supine imaging in which the holder is moved in the horizontal direction with respect to the subject M lying down. In the above-described embodiment, the holder 19 is moved along the body axis direction of the subject M. However, long imaging may be performed by moving the holder 19 in a direction different from the body axis direction of the subject M.

  Moreover, although the said embodiment has illustrated the linear movement system which moves X-ray source 10 linearly with the movement of the holder 19 with which the electronic cassette 13 was mounted | worn, with the movement of the holder with which the electronic cassette was mounted | worn Therefore, the present invention may be applied to a swinging method in which the angle of the X-ray source is changed so as to change the X-ray irradiation direction. Further, imaging may be performed while the holder 19 and the X-ray source 10 are moved without stopping at each imaging position.

  If a defect occurs in the detection pixel 65 of the electronic cassette 13 or communication between the radiation source control device 11 and the electronic cassette 13 is interrupted during imaging due to a disconnection of wiring or the like, the irradiation stop signal is not correctly transmitted and received, and the AEC is There may be cases where it does not work. In particular, since the maximum value of the current irradiation time product is set as an imaging condition on the radiation source control device 11 side, there is a possibility that the exposure dose to the patient may become the upper limit value or more if AEC does not work. Therefore, the electronic cassette 13 is provided with a test mode, and test photographing is performed under all photographing conditions of the console 14 immediately after installation or before photographing for one day. Even after the electronic cassette 13 transmits an irradiation stop signal to the radiation source control device 11, the detection pixel 65 continues to detect X-rays, and if X-ray irradiation stop is detected within a predetermined time, it is normal. If it is determined that AEC is being performed, and if it is not detected, it is determined that some failure has occurred, and a warning message is displayed on the display 89 of the console 14.

  In addition, when the radiation signal I / F 35, 80 of the radiation source control device 11 and the electronic cassette 13 can be connected by both wired and wireless, the wireless communication is unstable as a result of monitoring the radio field intensity and the like. When it is determined that it is, a warning may be displayed so as to switch to wired.

  In the above embodiment, the detection pixel 65 short-circuited and connected to the signal line 57 without using the TFT 52 is used as the AEC sensor, but the pixel 50 generates the bias line 53 that supplies the bias voltage Vb to each pixel 50. The amount of current may be detected by monitoring the current of the bias line 53 connected to a specific pixel 50 by using the current based on the charge, and leaks from the pixel 50 when all the TFTs 52 are turned off. The dose may be detected based on the leak charge. Further, an AEC detection pixel having a different configuration and independent output from the pixel 50 may be provided on the same plane as the imaging surface 41.

  In the above embodiment, the example in which the console 14 and the electronic cassette 13 are separate has been described. However, the console 14 does not have to be an independent device, and the function of the console 14 may be mounted on the electronic cassette 13. Similarly, the radiation source control device 11 and the console 14 may be integrated. Further, the present invention is not limited to an electronic cassette that is a portable X-ray image detection device, and may be applied to an X-ray image detection device that is installed on an imaging table.

  The present invention can be applied not only to X-rays but also to imaging systems that use other radiation such as gamma rays.

2 X-ray imaging system 10 X-ray source 11 Radiation source control device 13 Electronic cassette 14 Console 35 Irradiation signal I / F
40, 150 FPD
50 pixels 65 detection pixels 67 AEC section 80 irradiation signal I / F
85 CPU
89 Display 90 Input device 102 Cassette control unit 103 Dose index value calculation unit 151, 152 First and second pixels

Claims (8)

A radiation source for irradiating the subject with radiation;
A radiological image detection apparatus having a detection panel in which a plurality of pixels that receive radiation transmitted through a subject, accumulate signal charges, and output the signal charges to a signal line according to driving of a switching element;
A dose detection sensor for detecting a dose of radiation transmitted through the subject, having a daylighting field on substantially the entire imaging surface provided with the pixels of the detection panel;
The radiation image detecting apparatus and the radiation source is moved, n (n is a natural number of 2 or more of the imaging surface a long shooting range is divided so as to partially overlap containing a plurality of sites of a subject ) In the radiographic imaging system that synthesizes n times of radiographs and generates and displays a single long image.
A dose index value calculating means for calculating a dose index value of an overlap region of the radiographic image generated by dividing the long imaging range so that the imaging surface partially overlaps;
A threshold value for setting an irradiation stop threshold value for the k-th imaging based on the dose index value for the (k-1) -th imaging (k = 2, 3, 4,..., N) calculated by the dose index value calculating means. Setting means;
When the integrated value of the dose detected by the dose detection sensor existing in the overlap region between the (k-1) th imaging and the kth imaging reaches the irradiation stop threshold set by the threshold setting means, the kth A radiation imaging system comprising: automatic exposure control means for stopping radiation irradiation by the radiation source for imaging. A storage means for preliminarily storing an imaging range to be imaged for the first time among the n imaging ranges, a lighting field of the dose detection sensor, and an irradiation stop threshold value of the automatic exposure control means;
The automatic exposure control means does not use the exposure stop threshold set based on the overlap region and the dose index value for the first imaging, but automatically controls exposure based on the lighting field and the irradiation stop threshold stored in the storage means. The radiation imaging system according to claim 1, wherein:   The radiation imaging system according to claim 2, wherein the first imaging range includes the waist, and an area corresponding to the waist is stored in the daylighting field. An operation input means for setting an imaging range to be imaged for the first time among the n imaging ranges, a lighting field of the dose detection sensor, and an irradiation stop threshold value of the automatic exposure control unit;
The automatic exposure control means automatically exposes the first exposure with the lighting field and the irradiation stop threshold set by the operation input means, not the irradiation stop threshold set based on the overlap region and the dose index value. The radiation imaging system according to claim 1, wherein control is performed.   The radiation imaging system according to claim 1, wherein the dose index value calculating unit calculates a pixel value of the overlap region as a dose index value.   6. The radiation imaging system according to claim 1, wherein the dose detection sensor is the pixel directly connected to a signal line without a switching element.   The radiation imaging system according to claim 1, wherein the radiation image detection device is an electronic cassette in which the detection panel is housed in a portable housing. A radiation source for irradiating the subject with radiation;
A radiological image detection apparatus having a detection panel in which a plurality of pixels that receive radiation transmitted through a subject, accumulate signal charges, and output the signal charges to a signal line according to driving of a switching element;
A radiation imaging system having a daylighting field on substantially the entire imaging surface provided with the pixels of the detection panel, and a dose detection sensor that detects a dose of radiation transmitted through the subject,
The radiation image detecting apparatus and the radiation source is moved, n (n is a natural number of 2 or more of the imaging surface a long shooting range is divided so as to partially overlap containing a plurality of sites of a subject ) In the imaging range, and the n radiographic images obtained thereby are combined to generate and display a single long image,
A dose index value calculating step for calculating a dose index value of an overlap region of the radiographic image generated by dividing the long imaging range so that the imaging surface partially overlaps;
A threshold value for setting an irradiation stop threshold value for the k-th imaging based on the dose index value for the (k−1) -th imaging (k = 2, 3, 4,..., N) calculated in the dose index value calculating step. Configuration steps;
When the integrated value of the dose detected by the dose detection sensor existing in the overlap region between the (k-1) th imaging and the kth imaging reaches the irradiation stop threshold set in the threshold setting step, the kth An automatic exposure control step of stopping irradiation of radiation from the radiation source for imaging.

Images