WO2014038461A1

WO2014038461A1 - Radiographic imaging system, radiation generating apparatus and method for operating same

Info

Publication number: WO2014038461A1
Application number: PCT/JP2013/073113
Authority: WO
Inventors: 亮今▲邨▼
Original assignee: 富士フイルム株式会社
Priority date: 2012-09-04
Filing date: 2013-08-29
Publication date: 2014-03-13
Also published as: JP2014050418A; JP5984294B2

Abstract

The present invention reduces the time taken for a single radiographic imaging operation in which pre-imaging and actual imaging is set. An irradiation switch of an X-ray imaging system is a two-step press switch in which SW2 cannot be switched on without first pressing SW1. A radiation source control device starts warming up an X-ray source when the irradiation switch is half pressed (i.e., SW1 is on). When the irradiation switch is kept half pressed after the X-ray source has warmed up, the warmed up state is maintained, and when the irradiation switch is pressed all the way down (i.e., SW2 is on), the X-ray source starts emitting radiation for actual imaging without carrying out a second warm up.

Description

Radiography system, radiation generator and method of operating the same

The present invention relates to a radiation imaging system for taking a radiation image, a radiation generation apparatus, and an operation method thereof.

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 generator that generates an X-ray, and an X-ray imaging apparatus that captures an X-ray image formed by X-rays transmitted through a subject (patient). The X-ray generator inputs an X-ray source for irradiating X-rays toward a subject, a radiation source control device for controlling the drive of the X-ray source, and a drive instruction for operating the X-ray source to the radiation source control device Irradiation switch. The X-ray imaging apparatus detects an X-ray image detection apparatus that detects an X-ray image by converting an X-ray transmitted through a subject into an electrical signal, and drive control of the X-ray image detection apparatus. Have a console to do.

The X-ray source has an X-ray tube which emits thermoelectrons from a filament (cathode) by applying a high voltage, and emits X-rays by colliding the emitted thermoelectrons with a target (anode). There is. Since the focal point of the target which the thermal electrons collide with is heated to a high temperature, a rotating anode type is generally used as an X-ray tube in which the target is rotated to dissipate heat. In the rotary anode type X-ray source, warm-up such as raising the rotational speed of the target to a prescribed rotational speed is performed before X-ray irradiation. On the other hand, as an irradiation switch, a two-step push switch capable of two-step press operation of half press and full press is generally used. In the case of a two-step push switch, the source controller causes the X-ray source to start warm-up when receiving an input of a drive instruction by a half press from the irradiation switch, and receives an input of a drive instruction by a full press. The source is started to emit X-rays.

As an X-ray imaging apparatus, instead of an X-ray image recording apparatus using an X-ray film or an IP (imaging plate) cassette, one using an X-ray image detection apparatus that electronically detects an X-ray image ing. The X-ray image detection device has a sensor panel also referred to as a flat panel detector (FPD).

The sensor panel has an imaging area in which pixels for storing signal charges according to the amount of incident X-rays are arranged in a matrix. The pixel includes a photoelectric conversion unit that generates charge and stores the generated charge, and a switching element such as a TFT. The sensor panel stores signal charges for each pixel, reads out the stored signal charges to a signal processing circuit via a switching element such as a TFT, and converts the X-ray image into a voltage signal by the signal processing circuit. To detect.

In addition, in the X-ray imaging system, the integrated value (accumulated dose) of X-ray dose is acquired during X-ray imaging (during irradiation) in order to obtain a radiation image of appropriate image quality while suppressing the exposure dose to the subject. AEC (Automatic Exposure Control) may be performed to stop the irradiation of the X-ray by the X-ray source when the measured cumulative dose reach the target dose. The dose irradiated by the X-ray source is the tube current time product which is the product of the X-ray irradiation time (unit; s) and the tube current (unit; mA) that defines the dose irradiated by the X-ray source per unit time Determined by (mAs value). Although imaging conditions such as irradiation time and tube current have approximate recommended values depending on the imaging site (chest and head) of the subject, gender, age, etc., X-ray transmittance changes due to individual differences such as the physical constitution of the subject AEC will be conducted to obtain more appropriate image quality.

As the method of AEC, for example, as described in JP-A-2011-115368, one X-ray imaging is performed by a set of pre-imaging and main imaging, and based on the result of the pre-imaging, the main imaging There is a method of determining imaging conditions such as X-ray irradiation time and tube current time product (mAs value). The imaging conditions of the pre-imaging are determined based on, for example, the imaging region and patient information such as age and gender.

In the X-ray imaging system of JP 2011-115368 A, a series of processes of pre-imaging, determination of imaging conditions for main imaging, and main imaging are continuously executed according to one pressing operation of the irradiation switch. Before the pre-shooting and the main shooting, warm-up of the X-ray source is performed respectively.

In JP 2011-115368 A, since warm-up of the X-ray source is performed twice before the pre-shooting and the main taking, the time taken for one X-ray taking a set of the pre-taking and the main taking is taken It will be so long. The warm-up includes mechanical operation such as increasing the rotation of the rotary anode, and thus takes several seconds, and is longer than the irradiation time of X-rays of the order of several seconds to several seconds. In addition, even if the time increased by warm-up in a single X-ray imaging is short, the time is accumulated when imaging a large number of patients such as mass screening, so the influence on the diagnostic efficiency Too big.

An object of the present invention is to provide a radiation imaging system, a radiation generation apparatus, and an operation method thereof that can shorten the time required for one radiation imaging that combines pre-imaging and main imaging and improve the diagnostic efficiency. I assume.

In order to achieve the above object, a radiation imaging system of the present invention comprises a radiation generating device and a radiation imaging device. The radiation generator emits radiation toward the subject. The radiation imaging apparatus receives radiation transmitted through a subject and takes a radiation image. The radiation imaging system performs one imaging by a main imaging for capturing a radiation image and a pre-imaging for determining imaging conditions for the main imaging prior to the main imaging. The radiation generator comprises a radiation source, an irradiation switch, and a source controller. The radiation source performs a first irradiation for pre-imaging and a second irradiation for main imaging. The irradiation switch can perform at least two steps of pressing operation, and inputs a drive instruction by the pressing operation. The radiation source control device controls the drive of the radiation source based on the drive instruction. Furthermore, the radiation source control device receives an input of a drive instruction by the first pressing operation of the irradiation switch, and causes the radiation source to start warm-up before the first irradiation, and after the completion of the warm-up While the first-step pressing operation is not released, the warm-up is maintained, and the driving instruction by the pressing operation after the second step of the irradiation switch is input without releasing the first-step pressing operation. In the case, the second irradiation is started without warming up.

Preferably, the first irradiation is performed after the warm-up is completed and until the second irradiation is started.

The irradiation switch is, for example, a two-step push switch capable of full-pressing, which is a first-step pressing operation, and a second-step pressing operation. In this case, the radiation source control device starts the warm-up upon receiving the input of the drive instruction by the half press, and further starts the first irradiation following the warm-up, and receives the input of the drive instruction by the full press. To start. Alternatively, the radiation source control device starts the warm-up upon receiving the drive instruction input by the half press, and further receives the drive instruction input by the first full press to initiate the first irradiation, and then the half press The second irradiation is started in response to the input of the drive instruction by the second full-press after returning to.

The irradiation switch may be a three-step push switch capable of full-pressing, which is a first-step pressing operation, a first-step pressing, a second-step pressing operation, and a third-step pressing operation. In this case, the radiation source control device starts the warm-up upon receiving the drive instruction input by one-step push, receives the drive instruction input from the middle push, starts the first irradiation, and receives the drive instruction input by the full-press. Receive and start the second irradiation.

The radiation source control apparatus transmits, for example, an irradiation start request signal for requesting permission of irradiation start to the radiation imaging apparatus before performing each of the first irradiation and the second irradiation, and as a response to the irradiation start request signal, When the radiation permission signal is received from the radiation imaging apparatus, each of the first radiation and the second radiation is started.

The radiation source control apparatus receives an input of a drive instruction by the first-stage pressing operation by the irradiation switch, for example, and then releases the radiation source to the initial stage before the warm-up starts when the first-stage pressing operation is cancelled. Return to state. Alternatively, the radiation source control device does not cancel the first-step pressing operation after receiving the input of the driving instruction by the first-step pressing operation by the irradiation switch, and the driving instruction by the second-step and subsequent pressing operations When the state where there is no input continues for a predetermined time, the radiation source may be returned to the state before the start of the warm-up.

The radiation imaging apparatus includes, for example, a radiation image detection apparatus, a dose detection sensor, a timer, a main imaging condition determination unit, and a communication unit. The radiation image detection apparatus has a sensor panel having an imaging area in which pixels storing charge corresponding to the dose of radiation transmitted through an object are arranged in a matrix, and detects a radiation image. The dose detection sensor detects the dose of radiation due to the first irradiation in the pre-shooting. The timer counts the irradiation time of the first irradiation until the integrated value of the dose detected by the dose detection sensor reaches the preset target dose in the preliminary imaging. The main photographing condition determination unit determines the photographing conditions of the main photographing based on the irradiation time counted by the timer and the dose necessary for the second irradiation in the main photographing. The communication unit transmits the determined imaging conditions for the main imaging to the radiation generating apparatus.

The main imaging condition determination unit determines, for example, the imaging condition of the main imaging based on a dose obtained by subtracting the dose of the first irradiation in the preliminary imaging from the dose necessary for the second irradiation in the main imaging.

The radiation image detection apparatus preferably includes an AEC unit that outputs an irradiation stop signal for stopping the first irradiation to the radiation generation apparatus when the integrated value reaches the target dose in the pre-imaging.

The radiation image detecting apparatus preferably executes an accumulation operation of accumulating charges corresponding to the dose of the first irradiation in the image during the pre-imaging, and shifts to the main imaging without sweeping out the accumulated charges.

Preferably, the radiation image detection apparatus is an electronic cassette in which a sensor panel, a dose detection sensor, and a main imaging condition determination unit are housed in a portable case. Moreover, it is preferable that the dose detection sensor be disposed in the imaging region. In this case, the radiation image detection apparatus outputs, as a preview image, image information based on the integrated value of the dose detected by the dose detection sensor in the preliminary imaging.

The radiation generating apparatus according to the present invention is a single imaging operation for applying radiation to a subject and capturing a radiographic image of the subject, and a pre-shooting for determining imaging conditions for the main imaging prior to the main imaging. It is used in a radiation imaging system that performs imaging. The radiation generator comprises a radiation source, an irradiation switch, and a source controller. The radiation source performs a first irradiation for pre-imaging and a second irradiation for main imaging. The irradiation switch can perform at least two steps of pressing operation, and inputs a drive instruction by the pressing operation. The radiation source control device controls the drive of the radiation source based on the drive instruction. Furthermore, the radiation source control device receives an input of a drive instruction by the first pressing operation of the irradiation switch, and causes the radiation source to start warm-up before the first irradiation, and after the completion of the warm-up While the first-step pressing operation is not released, the warm-up is maintained, and the driving instruction by the pressing operation after the second step of the irradiation switch is input without releasing the first-step pressing operation. In the case, the second irradiation is started without warming up.

Further, according to the operation method of the radiation generating apparatus of the present invention, the main imaging for capturing the radiation image of the subject by irradiating the radiation to the subject and the pre-imaging for determining the imaging condition of the main imaging prior to the main imaging And a method of operating a radiation generating apparatus used in a radiation imaging system that performs imaging once. The method of operation of the radiation generator comprises: Having the radiation source execute a first irradiation for pre-imaging and a second irradiation for main imaging. At least two steps of pressing operation are possible, and from the irradiation switch for inputting the driving instruction by the pressing operation, the input of the driving instruction by the pressing operation of the first stage is received, and before the first irradiation to the radiation source. To start a warm up. After completion of the warm-up, while the first-step pressing operation is not released, the state where the warm-up is completed is maintained, and the pressing operation of the first step is not canceled When the drive instruction is input, start the second irradiation without warming up.

According to the present invention, in the case of performing one radiation imaging in a set of pre-imaging and main imaging, after the pre-imaging, since the main imaging is performed without performing the warm-up of the radiation source, it takes one radiation imaging The time can be shortened and the diagnostic efficiency can be improved.

FIG. 1 is a schematic view of an X-ray imaging system. It is a graph showing the relation between the dose of X-rays and the time. It is a figure which shows the internal structure of a radiation source control apparatus. It is an appearance perspective view showing an electronic cassette. It is a block diagram which shows the internal structure of an electronic cassette. It is explanatory drawing of AEC and this imaging | photography condition determination processing. It is a timing chart which shows the procedure of radiography. It is a timing chart which shows the procedure of the radiography of another mode. It is a timing chart which shows the procedure of X-ray imaging at the time of using the irradiation switch of 3 steps of push.

First Embodiment
In FIG. 1, the X-ray imaging system 2 instructs the X-ray source 10, the radiation source control device 11 for controlling the operation of the X-ray source 10, and the warm-up start and X-ray irradiation start to the X-ray source 10. Switch 12 for controlling the electronic cassette 13, an electronic cassette 13 for detecting X-rays transmitted through the subject (patient) and outputting an X-ray image, and a console 14 for controlling the operation of the electronic cassette 13 and displaying the X-ray image. The camera comprises a standing shooting stand 15 for shooting a subject in a standing posture, and a lying shooting stand 16 for shooting in a lying posture. The X-ray source 10, the radiation source control device 11, and the irradiation switch 12 constitute an X-ray generator 2a, and the electronic cassette 13 and the console 14 constitute an X-ray imaging device 2b. In addition to this, a source moving device (not shown) for setting the X-ray source 10 in a desired direction and position is provided. Shared by

The X-ray source 10 has an X-ray tube and a field limiter (collimator) that limits the X-ray radiation field emitted by the X-ray tube. The X-ray tube has a cathode, which is a filament that emits thermal electrons, and an anode (target), which the thermal electrons emitted from the cathode collide to emit X-rays. The anode starts to rotate when instructed to start the warm-up, and the warm-up is ended when the rotational speed reaches a specified value. The irradiation field limiter has, for example, four lead plates for shielding X-rays arranged on each side of a square, and a rectangular irradiation opening for transmitting X-rays formed at the center, By moving the position, the size of the irradiation opening is changed to limit the irradiation field.

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 in accordance with an input operation from an operator via the input device 14 a such as a keyboard. The X-ray image from the electronic cassette 13 is displayed on the display 14 b of the console 14, and the data is stored in the storage device 14 c or memory (not shown) in the console 14 or an image storage server etc. Stored in the data storage of

The console 14 receives the input of the examination order including the information such as the sex, the age, the imaging region, and the imaging purpose of the subject, and displays the examination order on the display 14 b. The examination order is input from an external system that manages patient information such as HIS (hospital information system) or RIS (radiation information system) or examination information related to a radiological examination, or is manually input by an operator such as a radiologist. The examination order includes items of imaging sites such as the head, chest, abdomen, hands, and fingers. The imaging site also includes imaging directions such as front, side, oblique position, PA (irradiating X-rays from the back of the subject), AP (irradiating X-rays from the front of the subject), and the like. The operator confirms the contents of the inspection order on the display 14b, and inputs imaging conditions according to the contents on the input device 14a through the operation screen displayed on the display 14b.

The imaging conditions include the tube voltage (unit: kV) that determines the energy spectrum of the X-ray irradiated by the X-ray source 10, the tube current (unit; mA) that determines the irradiation amount per unit time, and the X-ray source 10 Line irradiation time (unit; s) etc. are included. Since the cumulative irradiation dose of X-rays is determined by the product of the tube current and the irradiation time, the tube current time product, which is the product of the two, instead of individually inputting the values of the tube current and the irradiation time as imaging conditions The value of (mAs value) may be input. However, as described later, in this example, AEC is performed to determine the irradiation time. Therefore, the irradiation time determined by the X-ray imaging system 2 is applied prior to the irradiation time input from the console 14.

In the X-ray imaging system 2, one set of X-ray imaging for acquiring one X-ray image to be provided for diagnosis is performed as a set of pre-imaging and main imaging. The pre-shooting is performed in order to determine the shooting conditions of the main shooting necessary for the subject in order to obtain an X-ray image of appropriate image quality in the main shooting. For this reason, in the pre-imaging, the subject is irradiated with an X-ray having a dose smaller than that of the main imaging. In the main imaging, X-rays are irradiated under imaging conditions determined by the pre-imaging.

As shown in FIG. 2, when X-rays are irradiated with the same tube voltage and tube current, that is, even if the irradiation amount of X-rays emitted by the X-ray source 10 is the same, X-rays according to the physique of the subject Because the transmittances of X.sub.x and H.sub.x are different, the reaching dose to reach the electronic cassette 13 changes. For example, when the subject thickness is relatively thick, as shown by the solid line graph, the required dose of X-rays per unit time which passes through the subject and reaches the electronic cassette 13 decreases, so the required cumulative dose is reached. The irradiation time Ta for the purpose becomes longer, and conversely, when the subject thickness is thin, it becomes shorter as shown by the dotted line graph (irradiation time Tb). In addition, even when the density of internal tissue is relatively high, the X-ray transmittance decreases, so the irradiation time becomes long, and when it is low, the irradiation time becomes short.

Since the necessary cumulative dose for obtaining a good quality X-ray image is fixed, the X-ray imaging system 2 performs AEC so that the necessary cumulative dose can be obtained even if the physical size of the subject is different. Specifically, the irradiation time is adjusted so that the cumulative dose of X-rays, which is the area of a trapezoid shown by the solid or dotted line graph, becomes the same as the required cumulative dose. The X-ray imaging system 2 measures the irradiation time until the accumulated dose reaches a predetermined threshold in the pre-imaging. Although the irradiation amount of X-rays is smaller in the pre-imaging than in the main imaging, the measured irradiation time is a value reflecting the X-ray transmittance according to the physical size of the subject. The X-ray imaging system 2 determines the irradiation time of the main imaging to obtain the accumulated dose necessary for the main imaging as the main imaging condition based on the irradiation time of the pre-imaging, and performs the main imaging under the condition.

As shown in FIG. 3, the source controller 11 boosts the input voltage with a transformer to generate a high tube voltage, and supplies the high voltage generator 20 to the X-ray source 10 through a high voltage cable; The tube voltage and tube current given to the source 10, the control unit 21 for controlling the X-ray irradiation time, the main information with the console 14, the communication I / F 22 for mediating transmission and reception of the signal, and the signal of the electronic cassette 13 And a memory 23, and a touch panel 24.

The irradiation switch 12, the memory 23, and the touch panel 24 are connected to the control unit 21. The irradiation switch 12 is a switch for inputting a drive instruction to the control unit 21. The irradiation switch 12 is a general two-step push switch capable of two-step pressing operation as an irradiation switch. The operation buttons SW1 and SW2 have a nested structure, and can not turn on SW2 unless the user presses SW1. With such a structure, a two-step pressing operation of half-pressing (SW1 on) which is a first-step pressing operation and full-pressing (SW2 on) which is a second-step pressing operation is performed. When the irradiation switch 12 is half-pressed (SW1 on), a signal indicating that the SW1 is turned on is input to the control unit 21 as a drive instruction by the half-press. Similarly, when full-pressed (SW2), a signal indicating that SW2 is turned on is input as a drive instruction by full-press.

The control unit 21 generates a control signal for controlling the drive of the X-ray source 10 in response to the input of the drive instruction from the irradiation switch 12. The control signals include a warm-up start signal for starting the warm-up of the X-ray source 10, a first irradiation start signal for starting the irradiation for pre-imaging, and the irradiation for the main imaging. There are a second irradiation start signal and an initialization signal for returning the X-ray source 10 to an initial state.

When the irradiation switch 12 is half-depressed, the control unit 21 issues a warm-up start signal to the high voltage generator 20 to cause the X-ray source 10 to start warm-up. If the half depression of the irradiation switch 12 is not released after the warm-up is completed, the control unit 21 performs synchronization control by transmitting and receiving synchronization signals with the X-ray imaging apparatus 2b, and then performs pre-imaging A first irradiation start signal is issued to the high voltage generator 20 to cause the X-ray source 10 to start X-ray irradiation for pre-imaging.

When the irradiation switch 12 is further pressed from the half-pressed state and fully pressed, the control unit 21 performs the synchronization control with the X-ray imaging apparatus 2b as in the pre-imaging, and then starts the second irradiation A signal is emitted to the high voltage generator 20 to cause the X-ray source 10 to start X-ray irradiation for main imaging.

The control unit 21 generates an initialization signal when the half-pressing is released after the irradiation switch 12 is once-half-pressed. After the irradiation switch 12 is half-pressed and warm-up of the X-ray source 10 is started, the control unit 21 half-pushes the irradiation switch 12 until the irradiation for pre-imaging and the irradiation for the main imaging are completed. Is released, an initialization signal is issued to the high voltage generator 20 to stop the rotation of the rotary anode of the X-ray source 10, and the X-ray source 10 is returned to the initial state before the start of the warm-up. These signals are input from the source controller 11 to the X-ray source 10 through the signal cable.

Further, the control unit 21 maintains the warm-up completed state without returning the X-ray source 10 to the initial state while the half depression of the irradiation switch 12 is not released even after the X-ray irradiation of the pre-imaging is stopped. Do. Therefore, when the irradiation switch 12 is fully pressed following the half-press, the X-ray source 10 can immediately start X-ray irradiation for main imaging without performing warm-up.

The memory 23 stores several types of imaging conditions such as tube voltage and tube current in advance. The imaging conditions are manually set by the operator through the touch panel 24. A plurality of types of imaging conditions read from the memory 23 are displayed on the touch panel 24. Among the displayed imaging conditions, the operator selects the same imaging conditions as the imaging conditions input to the console 14, whereby the imaging conditions are set for the radiation source control device 11. Of course, it is also possible to finely adjust the values of imaging conditions prepared in advance. The setting of the imaging conditions of the source control apparatus 11 may be automated by transmitting the imaging conditions input to the console 14 to the source control apparatus 11.

For tube voltage and tube current set as imaging conditions, the same values are used for pre-imaging and main imaging. As for the irradiation time, in the pre-imaging, as described later, since the irradiation time until AEC is performed in the X-ray imaging apparatus 2b and the target dose is measured, a margin is provided so that the irradiation does not stop during measurement. The value you set is set. In this value, the irradiation time in the pre-photographing is very short compared to the main photographing, and the irradiation time until the reaching dose to the electronic cassette 13 reaches the target dose changes according to the tube current and the photographing site It is set in consideration of things. The maximum value of the irradiation time set in the safety regulation in the X-ray source 10 may be set.

As the irradiation time of the main imaging, a value obtained by calculation in the X-ray imaging apparatus 2b is set based on the result of the pre-imaging. The control unit 21 is provided with a timer 25. The timer 25 measures the irradiation time of X-rays determined based on the result of the preliminary imaging in the main imaging. In the main imaging, when the control unit 21 measures the irradiation time set by the timer 25, the control unit 21 issues an irradiation stop signal to the high voltage generator 20 to stop the X-ray irradiation.

The irradiation signal I / F 26 mediates transmission and reception of synchronization signals in synchronization control performed by the radiation source control device 11 with the X-ray imaging device 2b. The control unit 21 transmits an irradiation start request signal which is a synchronous signal inquiring whether the X-ray imaging apparatus 2b may start the X-ray irradiation before starting the X-ray irradiation in the pre-imaging and the main imaging. Do. Then, as a response to the irradiation start request signal, the X-ray imaging apparatus 2b receives an irradiation permission signal, which is a synchronous signal indicating that preparation for receiving irradiation has been completed. The irradiation signal I / F 26 receives an irradiation stop signal emitted by the X-ray imaging apparatus 2 b when the X-ray imaging apparatus 2 b executes AEC in the pre-imaging.

The communication I / F 22 receives the imaging condition of the main imaging calculated in the X-ray imaging apparatus 2b based on the result of the preliminary imaging. The irradiation signal I / F 26 and the communication I / F 22 may be wired or wireless.

In FIG. 4, the electronic cassette 13 is configured of a sensor panel 30 and a flat box-shaped portable case 31 for housing the sensor panel 30. The housing 31 is formed of, for example, a conductive resin. A rectangular opening is formed on the front surface 31a of the housing 31 on which the X-rays are incident, and the transmission plate 32 is attached to the opening as a top plate. The transmission plate 32 is formed of a carbon material that is lightweight, has high rigidity, and has high X-ray transparency. The housing 31 also functions as an electromagnetic shield that prevents the penetration of electromagnetic noise into the electronic cassette 13 and the emission of electromagnetic noise from the electronic cassette 13 to the outside. In the housing 31, a battery (secondary battery) for supplying power of a predetermined voltage to each part of the electronic cassette 13, and an antenna for performing wireless communication of data such as an X-ray image with the console 14 are provided. It is built in other than sensor panel 30.

The housing 31 has a size in conformity with the international standard ISO 4090: 2001 substantially the same as a film cassette or an IP cassette. The electronic cassette 13 is detachably set on the

holders

15a and 16a (see FIG. 1) of the imaging bases 15 and 16 so that the front surface 31a of the housing 31 is held in a posture to face the X-ray source 10. Then, the X-ray source 10 is moved by the radiation source moving device according to the imaging table to be used. Further, the electronic cassette 13 may be placed on a bed on which the subject lies or held by the subject itself and used alone, in addition to being set on each of the

imaging platforms

15 and 16. The electronic cassette 13 has a size substantially the same as that of a film cassette and an IP cassette, and therefore can be attached to an existing photographing table for a film cassette and an IP cassette.

In FIG. 5, the sensor panel 30 has a TFT active matrix substrate, and an imaging region 40 is formed on this substrate. In the imaging region 40, a plurality of pixels 41 for accumulating charges according to the X-ray arrival dose are arranged in a matrix of n rows (x direction) x m columns (Y direction) at a predetermined pitch. Note that n and m are integers of 2 or more.

The sensor panel 30 has 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 41. The scintillator is made of CsI: Tl (thallium activated cesium iodide), GOS (Gd ₂ O ₂ S: Tb, terbium activated gadolium oxysulfide) or the like, and faces the entire surface of the imaging region 40 in which the pixels 41 are arrayed. Is located in The scintillator and the TFT active matrix substrate may be a PSS (Penetration Side Sampling) method in which the scintillator and the substrate are arranged in order of the X-ray incident side, or conversely, the ISS (irradiation) is arranged in the substrate and the scintillator in order. It may be a side sampling method. Alternatively, a direct conversion type sensor panel may be used which uses a conversion layer (amorphous selenium or the like) for converting X-rays directly into electric charge without using a scintillator.

As well known, the pixel 41 includes a photoelectric conversion unit 42 which generates a charge (electron-hole pair) upon incidence of visible light and stores the generated charge, and a first TFT 43 which is a switching element. Note that a capacitor for storing charge may be provided separately from the photoelectric conversion unit 42.

The photoelectric conversion unit 42 has a structure in which an upper electrode and a lower electrode are disposed above and below a semiconductor layer (for example, a PIN type) that generates an electric charge. In the photoelectric conversion unit 42, the first TFT 43 is connected to the lower electrode, and a bias line is connected to the upper electrode. The bias lines are provided for the number of rows of the pixels 41 (n rows) and connected to one bus. The bus bar is connected to a bias power supply. A bias voltage is applied from the bias power supply to the upper electrode of the photoelectric conversion unit 42 through the bias line of the bus bar and its daughter line. An electric field is generated in the semiconductor layer by application of a bias voltage, and charges (electron-hole pairs) generated in the semiconductor layer by photoelectric conversion move to the upper electrode and the lower electrode having one plus polarity and the other minus polarity. Thus, charge is accumulated in the photoelectric conversion unit 42.

In the first TFT 43, the gate electrode is connected to the first scanning line 44, the source electrode is connected to the signal line 45, and the drain electrode is connected to the photoelectric conversion unit 42. The first scanning line 44 and the signal line 45 are wired in a grid, and the first scanning line 44 is common to one row of pixels 41, one for each row of pixels 41 (n rows) It is provided. Further, one signal line 45 is provided in common to the pixels 41 for one column, the number of which is equal to the number of columns of the pixels 41 (m columns). The first scan line 44 is connected to the first gate driver 46, and the signal line 45 is connected to the signal processing circuit 47.

The first gate driver 46 drives the first TFT 43 under the control of the control unit 48 to accumulate signal charges corresponding to the X-ray arrival dose in the pixel 41, and the signal accumulated from the pixel 41. The sensor panel 30 is caused to perform the read operation for reading out the charge and the reset operation. In the accumulation operation, the first TFT 43 is turned off, while the signal charge is accumulated in the pixel 41. In the read operation, gate pulses G1 to Gn for driving the first TFTs 43 in the same row are sequentially generated at a predetermined interval from the first gate driver 46 to activate the first scanning lines 44 one row at a time, The first TFTs 43 connected to the scanning line 44 are turned on one row at a time. The charge accumulated in the photoelectric conversion unit 42 of the pixel 41 is read out to the signal line 45 when the first TFT 43 is turned on, and is input to the signal processing circuit 47.

Dark charges are generated in the semiconductor layer of the photoelectric conversion unit 42 regardless of the presence or absence of X-rays. The dark charge is accumulated in the photoelectric conversion unit 42 of the pixel 41 because a bias voltage is applied. Since the dark charge generated in the pixel 41 becomes a noise component for the image data, the reset operation is performed at predetermined time intervals before the X-ray irradiation to remove the dark charge. The reset operation is an operation of sweeping the dark charge generated in the pixel 41 through the signal line 45.

The reset operation is performed, for example, by a sequential reset method in which the pixels 41 are reset row by row. In the sequential reset method, gate pulses G1 to Gn are sequentially generated at predetermined intervals from the first gate driver 46 to the first scanning line 44 similarly to the readout operation of signal charges, and the first TFTs 43 are turned on one row at a time Make it

Instead of the sequential reset method, multiple rows of arrayed pixels are set as one group to sequentially reset within the group, and the parallel reset method that sweeps out the dark charges of the number of rows simultaneously or gate pulse is applied to all the rows. An all pixel reset method may be used which simultaneously sweeps out the dark charge of. The reset operation can be speeded up by the parallel reset method or the all pixel reset method.

The signal processing circuit 47 includes an integration amplifier 49, a CDS circuit (CDS) 50, a multiplexer (MUX) 51, an A / D converter (A / D) 52, and the like. The integration amplifier 49 is individually connected to each signal line 45. The integral amplifier 49 includes an operational amplifier 49a and a capacitor 49b connected between the input and output terminals of the operational amplifier 49a. The signal line 45 is connected to one input terminal of the operational amplifier 49a. The other input terminal of the operational amplifier 49a is connected to the ground (GND). A reset switch 49c is connected in parallel to the capacitor 49b. The integrating amplifier 49 integrates the charges input from the signal line 45, converts it into analog voltage signals V1 to Vm, and outputs the voltage signals. The MUX 51 is connected to the output terminal of the operational amplifier 49a of each column via the amplifier 53 and the CDS 50. The A / D 52 is connected to the output side of the MUX 51.

The CDS 50 has a sample and hold circuit, performs correlated double sampling on the output voltage signal of the integration amplifier 49 to remove noise, and holds the output voltage signal of the integration amplifier 49 for a predetermined period (sample and hold ). The MUX 51 selects one CDS 50 in order from the CDS 50 of each column connected in parallel with an electronic switch based on the operation control signal from the shift register (not shown), and outputs the voltage signal V1 ̃ output from the selected CDS 50 Input Vm to A / D 52 serially. An amplifier may be connected between the MUX 51 and the A / D 52.

The A / D 52 converts the input analog voltage signals V1 to Vm for one row into digital values, and outputs the digital values to the memory 54 incorporated in the electronic cassette 13. In the memory 54, digital values for one row are associated with the coordinates of the respective pixels 41 and recorded as image data representing an X-ray image for one row. Thus, reading of one row is completed.

When the voltage signals V1 to Vm for one row from the integration amplifier 49 are read out by the MUX 51, the control unit 48 outputs a reset pulse RST to the integration amplifier 49 and turns on the reset switch 49c. Thereby, the signal charges for one row accumulated in the capacitor 49b are discharged and reset. After the integration amplifier 49 is reset, the reset switch 49 c is turned off again, and after a predetermined time has elapsed, one of the sample hold circuits of the CDS 50 is held, and the kTC noise component of the integration amplifier 49 is sampled. Thereafter, the gate pulse of the next row is output from the first gate driver 46, and readout of the signal charge of the pixels 41 of the next row is started. Further, a gate pulse is output, and after a predetermined time has elapsed, the signal charge of the pixel 41 of the next row is held by another sample hold circuit of the CDS 50. These operations are sequentially repeated to read out the signal charges of the pixels 41 of all the rows.

When the reading of all the rows is completed, image data representing one X-ray image is recorded in the memory 54. The image data is read from the memory 54, subjected to various image processing by the control unit 48, and then output to the console 14 through the communication I / F 55. Thus, the X-ray image of the subject is detected.

In the reset operation, dark charge flows from the pixel 41 to the capacitor 49 b of the integration amplifier 49 through the signal line 45 while the first TFT 43 is in the on state. Unlike the read operation, the charge stored in the capacitor 49b is not read out by the MUX 51. The reset pulse RST is output from the control unit 48 in synchronization with the generation of the gate pulses G1 to Gn, and the reset switch 49c is turned on. The charge stored in the capacitor 49b is discharged, and the integration amplifier 49 is reset.

The control unit 48 is provided with a circuit (not shown) that performs various image processing of offset correction, sensitivity correction, and defect correction on the X-ray image data of the memory 54. The offset correction circuit subtracts the offset correction image acquired from the sensor panel 30 from the X-ray image in pixel units from the X-ray image without irradiating the X-rays, thereby fixing pattern noise caused by individual differences of the signal processing circuit 47 and the imaging environment. Remove. The sensitivity correction circuit is also referred to as a gain correction circuit, and corrects variations in sensitivity of the photoelectric conversion unit 42 of each pixel 41, variations in output characteristics of the signal processing circuit 47, and the like. The defect correction circuit linearly interpolates the pixel value of the defective pixel with the pixel value of the surrounding normal pixel based on the defective pixel information generated at the time of shipping or periodic inspection. Further, the defect correction circuit similarly interpolates the pixel value of the detection pixel 41b used for AEC, which will be described later. The various image processing circuits described above may be provided in the console 14 and the various image processing may be performed by the console 14.

The pixel 41 includes a normal pixel 41 a and a detection pixel 41 b. The normal pixel 41a is used to generate an X-ray image. On the other hand, the detection pixel 41 b functions as a dose detection sensor that detects an arrival dose of X-rays to the imaging region 40. The detection pixel 41 b is used for AEC to stop the irradiation of the X-ray by the X-ray source 10 when the ultimate dose of the X-ray reaches a predetermined value. In the drawing, the detection pixel 41b is hatched to distinguish it from the normal pixel 41a.

The detection pixels 41 b are disposed so as to be uniformly scattered in the imaging region 40 without being locally biased in the imaging region 40. It is preferable that the ratio of the detection pixel 41b to all the pixels 41 is about 0.01%. For example, a plurality of detection pixels 41b (every three rows in this example) are provided in the column of the pixels 41 to which the same signal line 41 is connected, and no detection pixel 41b is provided in the column where the detection pixels 41b are provided. A plurality of rows are provided. If the pixels 41 are arranged in a matrix of 1024 rows and 1024 columns, for example, if 16 detection pixels 41 b are equally arranged for eight signal lines 41 in 128 columns, the ratio of the detection pixels 41 b is It becomes about 0.01%. The position of the detection pixel 41b is known at the time of manufacture of the sensor panel 30, and the sensor panel 30 previously stores the position (coordinates) of all the detection pixels 41b in a non-volatile memory (not shown).

The above example is one example, and the arrangement, the number, and the ratio of the detection pixels 41 b can be changed as appropriate. For example, with regard to the arrangement, the detection pixels 41b may be concentrated and arranged locally, contrary to the present embodiment. For example, in a mammography apparatus for imaging a breast, the detection pixels 41b may be arranged concentrated on the chest wall side.

The basic configuration of the photoelectric conversion unit 42 and the like of the normal pixel 41a and the detection pixel 41b is completely the same, but a second TFT 57 is connected to the detection pixel 41b in addition to the first TFT 43. The second TFT 57 is driven by a second scan line 58 and a second gate driver 59 which are different from the first scan line 44 and the first gate driver 46 for driving the first TFT 43. Since the second TFT 57 is connected to the detection pixel 41b, the normal pixel 41a in the same row turns off the first TFT 43, and it is possible to read out the charge even during the accumulation operation of accumulating the signal charge.

Since the pre-shooting and the main shooting are continuously performed, the sensor panel 30 starts the pre-shooting in order to reflect the X-ray irradiated in the pre-shooting on the X-ray image read out after the end of the main shooting. In addition, the accumulation operation of the normal pixel 41a is started, and thereafter, the accumulation operation is continued until the main photographing is completed. On the other hand, in the pre-shooting, the sensor panel 30 performs a dose detection operation using the detection pixel 41b for AEC. Since the second TFT 57 is connected to the detection pixel 41b, the sensor panel 30 turns the first TFT 43 to which the normal pixel 41a is connected to the OFF state and performs the accumulation operation of the normal pixel 41a in the pre-photographing. Then, the dose detection operation can be performed by turning on and off the second TFT 57.

In the dose detection operation performed at the time of pre-shooting, the second gate driver 59 performs gate pulses g1, g4, g7,..., Gk for simultaneously driving the second TFTs 57 in the same row under the control of the control unit 48. By sequentially generating k = 1 + 3 (n-1) at predetermined intervals, the second scanning lines 58 are activated sequentially by one row, and the second TFTs 57 connected to the second scanning lines 58 are sequentially turned on by one row. It will be in the state. The time for the on state is defined by the pulse width of the gate pulses g1, g4, g7,... The second TFT 57 returns to the off state when the time defined by the pulse width elapses. The charge generated in the photoelectric conversion unit 42 of the detection pixel 41 b flows into the capacitor 49 b of the integration amplifier 49 via the signal line 45 while the second TFT 57 is on regardless of whether the first TFT 43 is on or off. The charge from the detection pixel 41b accumulated in the integrating amplifier 49 is output to the A / D 52, and is converted into a digital voltage signal (hereinafter referred to as a dose signal) by the A / D 52. The dose signal is output to the memory 54. A dose signal is recorded in the memory 54 in association with coordinate information of each detection pixel 41 b in the imaging region 40. The sensor panel 30 repeats such dose detection operation a plurality of times at a predetermined sampling rate.

In FIG. 6, the AEC unit 60 is drive-controlled by the control unit 48. The AEC unit 60 reads out from the memory 54 the dose signal acquired a plurality of times at a predetermined sampling rate in the pre-shooting, and performs AEC based on the read dose signal.

The AEC unit 60 measures the accumulated dose of X-rays reaching the imaging region 40 by sequentially adding, for each coordinate, dose signals read from the memory 54 by a plurality of dose detection operations. More specifically, the AEC unit 60 obtains an accumulated dose for each divided area obtained by equally dividing the imaging area 40 into areas of a predetermined size. The accumulated dose of each divided area is obtained, for example, by calculating the integrated value of the dose signal of each of a plurality of detection pixels 41b present in each divided area, and adding the integrated value of each detected pixel 41b to the number of detected pixels 41b. The divided average value is used. The AEC unit 60 defines, for example, the divided area having the lowest accumulated dose among the divided areas as a light collection area which is a determination target area of the AEC.

Note that how to determine the light collection area is an example, and the light collection area may be determined according to the imaging region, or an arbitrary area may be designated as the light collection area by user setting. The accumulated dose of each divided area may not be an average value, and may be the maximum value, the mode value, or the total value among the integrated values of the dose signal of each detection pixel 41b in each divided area.

The AEC unit 60 compares the accumulated dose of the light collection area with the preset irradiation stop threshold (target dose) to determine whether the accumulated dose has reached the irradiation stop threshold. The AEC unit 60 outputs an irradiation stop signal to the control unit 48 when it is determined that the accumulated dose in the light receiving area exceeds the irradiation stop threshold and the accumulated dose of X-rays has reached the target dose.

The irradiation signal I / F 26 of the radiation source control device 11 is connected to the irradiation signal I / F 61 in a wired or wireless manner. The irradiation signal I / F 61 is a synchronization signal transmitted / received during synchronization control with the radiation source control device 11, specifically, reception of an irradiation start request signal from the radiation source control device 11, and an irradiation start request It mediates the transmission to the source controller 11 of the exposure signal, which is the response to the signal. Besides, the irradiation stop signal output from the AEC unit 60 is received through the control unit 48 and transmitted to the radiation source control device 11.

The communication I / F 55 is connected by wire or wirelessly to each of the console 14 and the radiation source control device 11, and mediates transmission and reception of information between the console 14 and the radiation source control device 11. The communication I / F 55 receives the imaging conditions input by the operator and the determination conditions to be described later with the console 14, and inputs the information to the control unit 48. Between the radiation source control apparatus 11 and the communication I / F 22, the main imaging conditions determined by the control unit 48 are transmitted to the radiation source control apparatus 11.

The storage device 14 c of the console 14 stores a determination condition table 62 in which a plurality of determination conditions are recorded in advance for each imaging condition. The determination conditions include the irradiation stop threshold and the required dose. As described above, the irradiation stop threshold is information for the AEC unit 60 to determine the irradiation stop of the X-ray in comparison with the integrated value of the dose signal at the time of preliminary imaging. Since a small amount of X-rays is irradiated at the time of pre-imaging, if the irradiation stop threshold is too low, it will be affected by noise superimposed on the dose signal, which will cause an erroneous determination. Therefore, the irradiation stop threshold is set to a value that is not affected by noise. The necessary dose is used when the control unit 48 determines the imaging conditions for the main imaging. The required dose is the cumulative dose of X-rays required for the main imaging, and is set to a value that makes the X-ray image obtained for the main imaging have a good image quality for diagnosis.

When the imaging condition is input by the operator, the console 14 reads out from the determination condition table 62 the determination conditions corresponding to the imaging region, the tube voltage and the tube current included in the imaging condition. The console 14 transmits the read determination condition to the electronic cassette 13 together with the imaging condition. The electronic cassette 13 receives the imaging condition and the determination condition through the communication I / F 55 and inputs the same to the control unit 48. The control unit 48 provides the AEC unit 60 with the irradiation stop threshold among the determination conditions.

The control unit 48 is provided with a timer 63. The timer 63 is a time taken from the transmission of the irradiation permission signal to the radiation source control device 11 until the AEC unit 60 outputs the irradiation stop signal in the AEC executed at the time of pre-photographing, that is, the accumulated dose in the light collection area The irradiation time until reaching the irradiation stop threshold is counted.

The control unit 48 uses the X-ray irradiation time (time to reach the irradiation stop threshold) in the pre-shooting timed by the timer 63 and the necessary dose and the irradiation stop threshold input from the console 14 under the imaging conditions of the main imaging Determine a certain irradiation time. The irradiation time for main imaging is the time until the required dose is obtained in main imaging with the same tube current as in preliminary imaging, so it can be determined by proportional calculation from the irradiation time taken to reach the irradiation stop threshold in preliminary imaging . Assuming that the irradiation time of the main imaging to be obtained is T2, the required dose is D2, the irradiation time of the preliminary imaging is T1, and the irradiation stop threshold (the cumulative dose in the preliminary imaging) is D1, the irradiation time T2 can be obtained by the following equation (1) .
T2 = T1 · D2 / D1 (1)

However, as described above, since the accumulation operation of the normal pixel 41a is continued without interruption from the pre-shooting to the main shooting, the signal charge corresponding to the dose irradiated in the pre-shooting is also stored in the normal pixel 41a. It is done. Therefore, the required dose in the main imaging can be a value obtained by subtracting the dose already irradiated in the preliminary imaging. In this case, the irradiation time T2 of the main imaging can be obtained by the following equation (2).
T2 = T1 · (D2-D1) / D1 (2)

The control unit 48 transmits the irradiation time T2 for the main imaging thus determined to the radiation source control apparatus 11 via the communication I / F 55 as the main imaging condition. Although the irradiation time T2 is transmitted as the main imaging condition, a tube current time product, which is the product of the irradiation time T2 and the tube current, may be transmitted.

Next, with reference to the timing chart of FIG. 7, a procedure in the case of performing one X-ray imaging in which the pre-imaging and the main imaging are set in the X-ray imaging system 2 will be described.

When performing X-ray imaging in the X-ray imaging system 2, first, the subject is set to a predetermined imaging position of either the standing position or the photographing

position

15 or 16 of the recumbent position, and the height and horizontal position of the electronic cassette 13 Adjust the position of the subject with the subject. Then, the height and horizontal position of the X-ray source 10 and the size of the irradiation field are adjusted in accordance with the position of the electronic cassette 13 and the size of the imaging region. Next, imaging conditions (imaging region, tube current, tube voltage) are set in the radiation source control device 11 and the console 14. The imaging conditions set by the console 14 are provided to the electronic cassette 13. Further, as shown in FIG. 6, the determination conditions (irradiation stop threshold value, necessary dose) according to the imaging conditions are read out on the console 14 and provided to the electronic cassette 13 together with the imaging conditions.

When the preparation for imaging is completed, the irradiation switch 12 is half-pressed (SW1 ON) by the operator. When the irradiation switch 12 is pressed halfway, the radiation source control device 11 of the X-ray generator 2a issues a warm-up start signal to the high voltage generator 20 to cause the X-ray source 10 to start warming up. Further, when the warm-up of the X-ray source 10 is completed, the radiation source control device 11 transmits an irradiation start request signal (request) to the electronic cassette 13.

In the standby mode before X-ray imaging, the sensor panel 30 of the electronic cassette 13 repeatedly performs the reset operation and waits for an irradiation start request signal. When receiving the irradiation start request signal from the radiation source control device 11, the sensor panel 30 transmits a radiation permission signal (permission) to the radiation source control device 11 after performing a state check. At the same time, the sensor panel 30 finishes the reset operation, starts the accumulation operation and the dose detection operation, and switches from the standby mode to the imaging mode. Also, measurement of the X-ray irradiation time T1 of the pre-imaging by the timer 63 is started.

When the radiation source control device 11 receives the radiation permission signal from the sensor panel 30, the radiation source control device 11 issues a first radiation start signal to the high voltage generator 20 to cause the X-ray source 10 to start pre-imaging X-ray radiation. The X-rays emitted from the X-ray source 10 pass through the subject and enter the sensor panel 30.

In the dose detection operation, the sensor panel 30 repeatedly reads out the charge generated in the detection pixel 41b at a predetermined sampling rate. The AEC unit 60 calculates the accumulated dose for each divided area based on the dose signal from the detection pixel 41b read out at a predetermined sampling rate, and determines the divided area indicating the accumulated dose of the minimum value as the lighting area . Then, the AEC unit 60 compares the cumulative dose of the light collection area with the irradiation stop threshold to determine whether the cumulative dose has reached the irradiation stop threshold.

The AEC unit 60 outputs an irradiation stop signal when the accumulated dose in the light receiving area reaches the irradiation stop threshold. At the same time, the timer 63 stops measuring the X-ray irradiation time T1 of the pre-imaging. The irradiation stop signal is transmitted to the radiation source control device 11. The radiation source control device 11 receives the radiation stop signal and stops the radiation of the X-ray by the X-ray source 10. The radiation source control device 11 continues the warm-up completion state without returning the X-ray source 10 to the initial state even after the X-ray irradiation by the X-ray source 10 is stopped.

The sensor panel 30 continues the accumulation operation even after the AEC unit 60 outputs the irradiation stop signal. After the irradiation stop signal is transmitted, the control unit 48 executes the main imaging condition determination process. In the main imaging condition determination process, the control unit 48 determines the main exposure X-ray irradiation time T2 based on the irradiation time T1 counted by the timer 63 and the irradiation stop threshold set as the determination condition and the required dose. . Information on the determined irradiation time T2 is transmitted to the radiation source control device 11. In the radiation source control device 11, the received irradiation time T2 is set in the timer 25.

After pressing the irradiation switch 12 halfway, the operator fully presses the irradiation switch 12 in anticipation of the time required for warm-up and pre-shooting. When the irradiation switch 12 is fully pressed, the radiation source control device 11 transmits an irradiation start request signal (start) to the electronic cassette 13 to perform synchronous control before starting irradiation of the main imaging. In the electronic cassette 13, since the sensor panel 30 continues the accumulation operation from the pre-shooting, when the electronic cassette 13 receives the irradiation start request signal, it immediately transmits the irradiation permission signal (permission) to the radiation source control device 11. Send.

When the radiation source control device 11 receives the radiation permission signal, the radiation source control device 11 issues a second radiation start signal to the high voltage generator 20 to cause the X-ray source 10 to start X-ray radiation for the main imaging. Since the X-ray source 10 continues to be warmed up even after the pre-imaging, the X-ray irradiation of the main imaging can be immediately started without performing the warm-up before the main imaging. The radiation source control device 11 counts the irradiation time by the timer 25 and stops the X-ray irradiation when the counted irradiation time reaches the irradiation time T2.

In the sensor panel 30, the accumulation operation of the normal pixel 41a is performed subsequently to the pre-photographing. The timer 63 of the control unit 48 also counts the elapsed time since the second transmission of the irradiation permission signal. Then, when the elapsed time reaches the irradiation time T2, the operation of the sensor panel 30 is shifted from the accumulation operation to the read operation. As a result, image data representing one X-ray image is output to the memory 54. After the read operation, the sensor panel 30 returns to the standby mode in which the reset operation is performed.

The various image processing circuits of the control unit 48 perform various image processing on the X-ray image output to the memory 54 in the reading operation. The image-processed X-ray image is transmitted to the console 14 and displayed on the display 14 b for diagnosis. This completes one X-ray imaging for setting the pre-imaging and the main imaging.

As described above, in the X-ray imaging system 2, the warm-up of the X-ray source 10 is performed before the irradiation of the pre-imaging, and the warm-up is completed without returning the X-ray source 10 to the initial state even after the irradiation of the pre-imaging Keep in state. As a result, it is possible to omit the warm-up before the irradiation of the main imaging, and it takes time for one X-ray imaging to be performed as compared to the conventional case where warm-up is performed twice before the pre-imaging and the main imaging irradiation. Can be shortened. This improves the diagnostic efficiency and is particularly effective in mass screening where it is necessary to crawl many patients within a limited time.

Pre-imaging is performed until the cumulative dose necessary to determine the imaging conditions for the actual imaging is irradiated, and the irradiation time T1 of the pre-imaging measured by the timer 63 and the irradiation stop threshold set as the determination condition and the required dose Since the irradiation time T2, which is the imaging condition of the main imaging, is determined based on the above, the main imaging can be always performed under the appropriate imaging condition regardless of the individual differences such as the body type of the subject and the density of internal tissues. As compared with the case where the operator adjusts the imaging condition according to the individual difference of the subject, accurate and easy imaging can be performed.

Also, AEC is performed only at the time of pre-imaging where the amount of X-ray irradiation is small. This has the following merits compared with the case of performing AEC in real shooting. When AEC is performed, the irradiation stop signal is transmitted from the electronic cassette 13 to the radiation source control device 11. However, when a communication delay or the like occurs, the irradiation stop signal is delayed to be appropriate. In some cases, X-ray irradiation can not be stopped at the timing. When the irradiation stop signal is delayed, X-rays more than necessary are irradiated, so the exposure dose of the subject increases. If AEC is performed in pre-imaging with a small amount of X-ray irradiation, even if a delay occurs in the irradiation stop signal, an increase in unnecessary exposure can be suppressed as compared with the case of performing actual imaging.

In the above example, the same tube current is set for the pre-shooting and the main shooting, but for example, in the pre-shooting, the tube current may be smaller than that for the main shooting. In this way, even when the irradiation stop signal is delayed in the pre-imaging, an increase in the unnecessary dose can be further suppressed because the tube current that determines the dose of X-rays per unit time is small. However, in this case, in the main photographing condition determination process, the irradiation time of the main photographing is calculated in consideration of the difference in tube current between the preliminary photographing and the main photographing.

Since the readout operation is not performed in the pre-imaging and the accumulation operation of the normal pixel 41a is continued from the start of the pre-imaging to the end of the main imaging, the X-rays irradiated in the pre-imaging can be prevented from being wasted. The amount of exposure to the subject can be reduced accordingly. In addition, when the irradiation of the pre-imaging is reflected on the X-ray image to be used for diagnosis in this way, the image quality of the X-ray image may be degraded due to the body movement of the subject between the pre-imaging and the main imaging. However, in the present invention, since the radiation for the main imaging is immediately performed without warm-up, and the radiation for the pre-imaging and the main imaging is performed without a gap, the influence of the body movement on the X-ray image can be reduced. .

Note that the reset operation may be performed at the time of stopping the X-ray irradiation in the pre-imaging, the charges accumulated in the pre-imaging may be discarded, and the accumulation operation may be restarted at the start of the X-ray irradiation in the main imaging. In this case, the exposure time T2 of the main imaging is determined without subtracting the cumulative dose (D1) in the pre-exposure corresponding to the irradiation stop threshold from the required dose (D2) using the equation (1) in the main imaging condition determination process Ask.

Further, in the above example, with regard to synchronous control at the time of preliminary imaging of the radiation source control device 11 and the electronic cassette 13, as shown in FIG. 7, when warm-up of the X-ray source 10 is completed Although the irradiation start request signal (request) is transmitted to the cassette 13, the irradiation start request signal may be transmitted when the irradiation switch 12 is pressed halfway or may be transmitted during warm-up. However, since the electronic cassette 13 transmits the irradiation permission signal which is a response to the irradiation start request signal and then starts counting the irradiation time T1, if there is an interval between the transmission timing of the irradiation permission signal and the irradiation start timing of the pre-shooting The accuracy of the irradiation time T1 is lost. Therefore, it is preferable to transmit the irradiation start request signal when the warm-up is completed as shown in the above example.

In the above example, the dose signal read from the detection pixel 41b is used only for AEC in the dose detection operation during pre-shooting, but image information based on the dose signal is transmitted from the electronic cassette 13 to the console 14 as a preview image. And may be previewed on the display 14b. In the above example, the detection pixels 41b are distributed throughout the entire imaging area 40, and the dose signal from each detection pixel 41b is recorded in the memory 54 in association with the coordinates of each detection pixel 41b. Be done. Therefore, although the image information recorded in the memory 54 has low resolution and can not be used for diagnosis, it can be used to confirm the position of the subject and the imaging region. Therefore, if the image information based on the dose signal is displayed as a preview, the operator can confirm that the position of the subject or the region to be imaged is not appropriate due to movement of the subject at the time of pre-imaging.

As described above, if image information based on the dose signal at the time of pre-shooting is used as a preview image to perform preview display before main shooting, the main shooting may be stopped if it is clearly found that shooting failed during pre-shooting. it can. In order to stop the main photographing at the time of the preview display, half-pressing of the irradiation switch 12 may be released. When the half depression of the irradiation switch 12 is released, an initialization signal is issued from the control unit 21 and the X-ray source 10 is returned to the initial state. Further, the operator operates the console 14 to return the electronic cassette 13 to the standby mode in which the sensor panel 30 repeats the reset operation. Then, after correcting the subject's positioning, start shooting again from the beginning.

Even if the preview image can not be confirmed, the operator usually monitors during shooting whether or not the subject's body movement occurs through the glass in the shooting room, so when the body movement is noticed visually, the irradiation is performed. By releasing the switch 12 half-pressed, the real shooting can be stopped.

In the above embodiment, the X-ray source 10 is returned to the initial state before the start of warmup when the half-pressing of the irradiation switch 12 is released, but instead, the X-ray source 10 is half-pressed after the irradiation switch 12 is half-pressed The elapsed time may be measured, and if the next operation is not performed even if the elapsed time passes a preset threshold, it may be determined that the main imaging has been canceled and the X-ray source 10 may be returned to the initial state. The electronic cassette 13 may shift the sensor panel 30 from the accumulation operation to the reset operation, judging that the main imaging has been stopped when the dose signal is approximately 0 in the predetermined sampling.

Second Embodiment
In the first embodiment, warm-up and pre-shooting irradiation are performed by half-pressing the switch 12 (SW1 on) and full-shooting (SW2 on) is performed for the main-shooting irradiation. It is not limited and may be an embodiment shown in FIG. In the second embodiment shown in FIG. 8, warm-up is performed by half-pressing the irradiation switch 12, and irradiation of pre-shooting is performed by the subsequent full-press. After the pre-shooting irradiation, the irradiation switch 12 is returned to a half-pushed state (SW1 is turned on and SW2 is turned off) so as to be surrounded by a dot-dash circle and full-exposure is performed by fully pressing again.

In this case, the source control device 11 issues a warm-up start signal to the X-ray source 10 to start the warm-up when the irradiation switch 12 is half-pressed, as in the first embodiment. It is. In the first embodiment, if the irradiation switch 12 is half-pressed, X-ray irradiation of the pre-shooting is started after the warm-up is completed, but in the second embodiment, after the warm-up is completed, the irradiation switch 12 is all When pressed, the radiation source controller 11 issues a first radiation start signal, and the X-ray source 10 starts X-ray radiation for preliminary imaging. Before X-ray irradiation in pre-imaging, synchronous control is performed between the radiation source control device 11 and the electronic cassette 13 by transmitting and receiving an irradiation start request signal and an irradiation permission signal. Then, the irradiation switch 12 is once returned from the fully-pressed state to the half-pressed state by the operator. After that, when fully pressed again, the radiation source control device 11 performs synchronous control with the electronic cassette 13 and issues a second radiation start signal to the X-ray source 10 to irradiate the X-ray source 10 with the main imaging. To start. The operation of the electronic cassette 13 during the pre-imaging X-ray irradiation is the same as that of the first embodiment, such as measurement of the irradiation time T1 and determination of the irradiation time T2.

Third Embodiment
The irradiation switch is not limited to the two-step push, and a three-step push irradiation switch may be used. In the case of the three-step push irradiation switch, as in the third embodiment shown in FIG. 9, warm-up is performed by one-step push (SW1 on), and then pre-shooting irradiation is performed by the next push (SW2 on). The full shooting may be performed by fully pressing (SW3 on). When the radiation switch is pressed one step, the radiation source control device 11 issues a warm-up start signal to the X-ray source 10 to start the warm-up, and when the radiation switch is pressed halfway, it issues a first radiation start signal. The radiation source 10 is caused to start irradiation for pre-imaging, and when it is fully pressed, a second irradiation start signal is issued to cause the X-ray source 10 to start irradiation for main imaging. In addition, since the conventional irradiation switch mainly uses two-step pressing, it is better to use the two-step pressing irradiation switch according to the first and second embodiments than the three-step pressing according to the present embodiment because the operation feeling is used. More preferable.

Alternatively, warm-up may be performed simply by pressing the irradiation switch 12 halfway, and irradiation of the pre-photographing and the main photographing may be automatically and continuously performed by full-pressing. However, if the pre-shooting and the main shooting are automatically performed without the operation of the radiation switch 12 before the main shooting as described above, the subject may move during the pre-shooting, and the shooting may be clearly identified as a shooting failure. Since it is not possible to cope with the case where the user wants to stop the shooting, it is better to start the irradiation of the main photographing after putting in one action as in the first to third embodiments. By putting one action before the start of the main exposure, the operator can recognize the boundary between the pre exposure and the main exposure by his / her operation, and stop the main exposure by looking at the result of the pre exposure, positioning the subject, The shooting conditions can also be corrected.

The information on the irradiation time T2 is transmitted from the electronic cassette 13 to the console 14 instead of the information on the irradiation time T2, which is the main imaging condition, directly transmitted from the electronic cassette 13 to the radiation source control device 11. Information on the irradiation time T2 may be transmitted to the radiation source control device 11.

Although the detection pixel 41b provided with the second TFT 57 driven separately from the first TFT 43 is illustrated in the above embodiment, the pixel in which the source electrode and the drain electrode of the first TFT 43 are shorted, or the first TFT 43 does not exist. A pixel in which 42 is directly connected to the signal line 45 may be used as a detection pixel.

In addition, even if the current value based on the charge generated in the pixel flows in the bias line that supplies the bias voltage to each pixel, the dose value can be detected by monitoring the current value of the bias line connected to a specific pixel. Good. In this case, a pixel for monitoring the current value is a detection pixel. Similarly, the leak current flowing out of the pixel may be monitored to detect the dose, and in this case as well, the pixel for monitoring the leak current is the detection pixel. Furthermore, a dose detection sensor having a different configuration and an independent output separately from the pixels may be provided in the imaging region. The form of the dose detection sensor for performing these AECs may be any other form.

Furthermore, in the above embodiment, in the pre-shooting, whether the accumulated dose reaches the irradiation stop threshold or not by comparing the accumulated dose in the daylight area with the preset irradiation stop threshold (target dose) in the AEC unit 60 Although the example which determines irradiation and stops irradiation of X-ray was described, the irradiation time of pre imaging | photography may be fixed. In this case, the detection pixel 41b may be present, but if the image information of the pre-photographing is read out from the normal pixel 41a and the condition of the main photographing is determined based on the value, the AEC It can be carried out. As the irradiation time of the pre-photographing, a value sufficiently smaller than the irradiation time of the main photographing is preset as a setting value.

In the above embodiment, the irradiation stop signal is output when the accumulated dose of X-rays in the pre-imaging reaches the irradiation stop threshold, but it is predicted that the accumulated dose of X-rays reaches the irradiation stop threshold based on the integrated value of the dose signal. The calculated time may be calculated, and the irradiation stop signal may be transmitted to the radiation source control device when the calculated prediction time is reached, or information of the prediction time itself may be transmitted to the radiation source control device. Further, the integrated value is not limited to the average value of the dose signal in the above embodiment, but may be the maximum value, the mode or the total value of the dose signal of the detection pixel 41b in each divided area.

In the above embodiment, the console 14 and the electronic cassette 13 are described as being separate, but the console 14 does not have to be an independent device, and the electronic cassette 13 may have the function of the console 14. In addition, part of the functions of the electronic cassette 13, for example, a processing unit for determining the main imaging conditions may be provided on the console 14. In addition to the electronic cassette 13 and the console 14, a photographing control device may be provided which executes part of the function of controlling the electronic cassette 13 of the console 14.

Although the TFT type sensor panel is illustrated in the above embodiment, a CMOS type sensor panel may be used. Further, the present invention is not limited to the electronic cassette which is a portable X-ray image detection device, and may be applied to an X-ray image detection device of a type installed on a photographing table. Furthermore, the present invention can be applied not only to X-rays but also to other radiations such as γ-rays as imaging targets.

Claims

A radiation generating apparatus for emitting radiation toward a subject, and a radiation imaging apparatus for capturing a radiation image by receiving radiation transmitted through the subject, a main imaging for capturing a radiographic image, and prior to the main imaging In a radiation imaging system that performs one imaging by pre-imaging to determine imaging conditions for the main imaging,
The radiation generator
A radiation source for performing the first radiation for the pre-shooting and the second radiation for the main shooting;
An irradiation switch capable of at least two steps of pressing operation, and inputting a drive instruction by the pressing operation;
In response to the input of the drive instruction by the first stage pressing operation of the irradiation switch, the radiation source is started to warm up before the first irradiation, and after the warm up is completed, the first stage is performed In the case where the warm-up is completed while the pressing operation is not released, and the driving instruction by the pressing operation of the second and subsequent stages of the irradiation switch is input without releasing the first pressing operation. And a radiation source control apparatus for starting the second irradiation without warm-up.
The radiography system according to claim 1, wherein the first irradiation is performed after the completion of the warm-up and before the second irradiation is started.
The radiation imaging system according to claim 1, wherein the irradiation switch is a two-step push switch capable of full-pressing as a first-step pressing operation and full-pressing as a second-step pressing operation.
The radiation source control device receives the input of the drive instruction by the half press to start the warm-up, and further starts the first irradiation following the warm-up, and receives the input of the drive instruction by the full press. The radiography system according to claim 3, wherein the second irradiation is started.
The radiation source control device receives the input of the drive instruction by the half press to start the warm-up, and further receives the input of the drive instruction by the first full press to start the first irradiation, and thereafter The radiation imaging system according to claim 3, wherein the second irradiation is started upon receiving an input of a drive instruction by a second full-press after returning to the half-press.
The irradiation switch is a three-step push switch capable of full-pressing, which is a first-step pressing operation, a first-step pressing, a second-step pressing operation, and a third-step pressing operation,
The radiation source control device receives an input of a drive instruction by one-step push to start the warm-up, receives an input of a drive instruction by middle push, starts the first irradiation, and inputs a drive instruction by full-press. The radiation imaging system according to claim 1, wherein the second radiation is received to start the second radiation.
The radiation source control apparatus transmits, to the radiation imaging apparatus, an irradiation start request signal for requesting permission to start irradiation before performing each of the first irradiation and the second irradiation;
The radiation imaging system according to claim 1, wherein each of the first irradiation and the second irradiation is started when an irradiation permission signal is received from the radiation imaging apparatus as a response to the irradiation start request signal.
The radiation source control apparatus warms up the radiation source when the first-step pressing operation is canceled after receiving an input of a drive instruction by the first-step pressing operation by the irradiation switch. The radiography system according to claim 1, wherein the radiography system is returned to the initial state before the start.
After the radiation source control device receives an input of a drive instruction by the first stage pressing operation by the irradiation switch, the first stage pressing operation is not canceled, and the radiation source control apparatus is operated by the second and subsequent stage pressing operations. The radiation imaging system according to claim 1, wherein the radiation source is returned to a state before the start of the warm-up when a state where there is no input of a drive instruction continues for a predetermined time.
The radiation imaging apparatus
A radiation image detection apparatus having a sensor panel having an imaging area in which pixels storing charge corresponding to a dose of radiation transmitted through an object are arranged in a matrix, and detecting the radiation image;
A dose detection sensor that detects a dose of the radiation by the first irradiation in the pre-shooting;
A timer for counting the irradiation time of the first irradiation until the integrated value of the dose detected by the dose detection sensor reaches a preset target dose in the pre-shooting;
A main imaging condition determination unit that determines an imaging condition for the main imaging based on the irradiation time counted by the timer and a dose necessary for the second irradiation in the main imaging;
The radiation imaging system according to claim 1, further comprising: a communication unit that transmits the determined imaging conditions for the main imaging to the radiation generating apparatus.
The main imaging condition determining unit determines the imaging condition for the main imaging based on a dose obtained by subtracting the dose of the first irradiation in the pre-imaging from the dose necessary for the second irradiation in the main imaging. The radiation imaging system according to claim 10 in range.
The radiation image detection apparatus includes an AEC unit that outputs an irradiation stop signal for stopping the first irradiation to the radiation generator when the integrated value reaches the target dose in the pre-imaging. The radiography system of Claim 10.
The radiation image detection apparatus executes an accumulation operation for accumulating charges corresponding to the dose of the first irradiation in the image during the pre-shooting, and shifts to the main shooting without sweeping out the accumulated charges. The radiography system of Claim 10.
11. The radiation imaging system according to claim 10, wherein the radiation image detection apparatus is an electronic cassette in which the sensor panel, the dose detection sensor, and the main imaging condition determination unit are housed in a portable case.
The radiation imaging system according to claim 10, wherein the dose detection sensor is disposed in the imaging region.
The radiation imaging system according to claim 15, wherein the radiation image detection apparatus outputs, as a preview image, image information based on an integrated value of the dose detected by the dose detection sensor in the preliminary imaging.
A radiation imaging system that performs one imaging by a main imaging for imaging a radiation image of a subject by irradiating radiation to the object and a pre-imaging for determining imaging conditions for the main imaging prior to the main imaging Radiation generator used for
A radiation source for performing the first radiation for the pre-shooting and the second radiation for the main shooting;
An irradiation switch capable of at least two steps of pressing operation, and inputting a drive instruction by the pressing operation;
In response to the input of the drive instruction by the first stage pressing operation of the irradiation switch, the radiation source is started to warm up before the first irradiation, and after the warm up is completed, the first stage is performed In the case where the warm-up is completed while the pressing operation is not released, and the driving instruction by the pressing operation of the second and subsequent stages of the irradiation switch is input without releasing the first pressing operation. And a radiation source control device for starting the second irradiation without warm-up.
A radiation imaging system that performs one imaging by a main imaging for imaging a radiation image of a subject by irradiating radiation to the object and a pre-imaging for determining imaging conditions for the main imaging prior to the main imaging In the method of operating the radiation generator used in
Causing the radiation source to execute the first irradiation for the pre-imaging and the second irradiation for the main imaging;
At least two steps of pressing operations are possible, and from the irradiation switch for inputting a driving instruction by the pressing operation, the input of the driving instruction by the pressing operation of the first step is received, and the first radiation source is received. Start warming up before irradiation,
After completion of the warm-up, the state where the warm-up is completed is maintained while the first-step pressing operation is not released.
Radiation generation that causes the second irradiation to be started without performing warm-up when a drive instruction is input by pressing operation after the second stage of the irradiation switch without releasing the first stage pressing operation. Method of operation of the device.