Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
  • A61B6/48—Diagnostic techniques
  • A61B6/482—Diagnostic techniques involving multiple energy imaging
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
  • A61B6/54—Control of apparatus or devices for radiation diagnosis
  • A61B6/542—Control of apparatus or devices for radiation diagnosis involving control of exposure
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
  • A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
  • A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
  • A61B6/4208—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
  • A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
  • A61B6/4266—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a plurality of detector units
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05G—X-RAY TECHNIQUE
  • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
  • H05G1/08—Electrical details
  • H05G1/26—Measuring, controlling or protecting
  • H05G1/30—Controlling
  • H05G1/38—Exposure time
  • H05G1/42—Exposure time using arrangements for switching when a predetermined dose of radiation has been applied, e.g. in which the switching instant is determined by measuring the electrical energy supplied to the tube
  • H05G1/44—Exposure time using arrangements for switching when a predetermined dose of radiation has been applied, e.g. in which the switching instant is determined by measuring the electrical energy supplied to the tube in which the switching instant is determined by measuring the amount of radiation directly

Definitions

• This disclosure relates to a radiography control device, method, and program.
• a radiation detector such as an FPD (Flat Panel Detector) to obtain a radiation image for diagnosis.
• FPD Fluor Panel Detector
• a radiography system has been proposed that is equipped with an AEC (Auto Exposure Control) mechanism that detects the amount of radiation that reaches the radiation detector and stops irradiating radiation when a certain amount of radiation is reached (see, for example, JP 2013-233420 A).
• AEC Automatic Exposure Control
• energy subtraction processing which utilizes the fact that the attenuation of transmitted radiation differs depending on the material that makes up the subject, and uses two radiation images obtained by irradiating the subject with two types of radiation with different energy distributions.
• a layered detector has been proposed as a radiation detector for performing this type of energy subtraction processing.
• a layered detector is constructed, for example, by stacking two radiation detectors in a layered configuration. By using such a layered detector, it is possible to perform energy subtraction imaging with a single irradiation of radiation. In addition, by acquiring a radiation image using only the radiation detector closest to the radiation source, it is also possible to perform simple imaging in the same way as when only one radiation detector is used.
• the amount of radiation irradiated to the radiation detector farther from the radiation source is smaller than the amount of radiation irradiated to the radiation detector closer to the radiation source. Therefore, if the dose is not set appropriately when performing energy subtraction processing, the amount of radiation irradiated to the radiation detector farther from the radiation source will be too small, reducing the signal-to-noise ratio (S/N), and as a result, the image quality of the radiation image acquired by energy subtraction processing will be reduced.
• S/N signal-to-noise ratio
• This disclosure has been made in consideration of the above circumstances, and aims to make it possible to obtain high-quality radiation images when performing radiation imaging using a layer structure detector.
• a radiography control device is a radiography control device that controls radiography of an object by irradiating the object with radiation emitted from a radiation source, a layered structure detector including a plurality of radiation detectors stacked together, each having a plurality of dose detection pixels for detecting a dose during radiation imaging; at least one processor; The processor Obtain the purpose of the shoot, determining at least one radiation detector to be used for controlling a dose of radiation during radiation imaging among the plurality of radiation detectors according to an imaging purpose; Dose control is performed according to the determined dose detected by the dose detection pixels of the radiation detector.
• the processor may determine that, among multiple radiation detectors, the radiation detector closest to the radiation source is the radiation detector that performs dose control.
• the processor may determine that, among the multiple radiation detectors, a radiation detector other than the radiation detector closest to the radiation source is the radiation detector that performs dose control.
• the processor may determine that all of the multiple radiation detectors are radiation detectors that perform dose control.
• the processor determines a target dose for performing radiation imaging in accordance with an imaging purpose; When the determined dose detected by the dose detection pixels of the radiation detector reaches the target dose, the driving of the radiation source may be stopped.
• the processor identifies a region of interest in the imaging target according to the imaging purpose.
• the dose control may be performed according to the dose detected by at least a dose detection pixel located at a position corresponding to the region of interest.
• a radiation imaging control method is a radiation imaging control device that controls radiation imaging of an object by irradiating the object with radiation emitted from a radiation source, the radiation imaging control method being in a radiation imaging control device that has a layered detector configured by stacking a plurality of radiation detectors, each having a plurality of dose detection pixels that detect a dose during radiation imaging, the method comprising: Obtain the purpose of the shoot, determining at least one radiation detector to be used for controlling a dose of radiation during radiation imaging among the plurality of radiation detectors according to an imaging purpose; Dose control is performed according to the determined dose detected by the dose detection pixels of the radiation detector.
• a radiography control program is a radiography control device that controls radiography of an object by irradiating the object with radiation emitted from a radiation source, the radiography control program being a radiography control program that causes a computer to execute a radiography control method in a radiography control device that is equipped with a layered detector configured by stacking a plurality of radiation detectors, each of which has a plurality of dose detection pixels that detect a dose during radiography, the program comprising: The procedure for obtaining the purpose of photography; A step of determining at least one radiation detector to be used for controlling a dose of radiation during radiation imaging, among the plurality of radiation detectors, according to an imaging purpose; The computer is caused to execute a procedure for performing dose control in accordance with the determined dose detected by the dose detection pixels of the radiation detector.
• radiography when performing radiography using a layer structure detector, high-quality radiographic images can be obtained.
• FIG. 1 is a schematic block diagram showing a configuration of a radiation image capturing system to which a radiation image capturing control device according to an embodiment of the present disclosure is applied;
• FIG. 1 is a diagram showing a schematic configuration of a radiation detector;
• FIG. 1 is a diagram for explaining the distribution of dose detection pixels.
• FIG. 1 is a diagram showing a schematic configuration of a radiation imaging control device according to an embodiment of the present invention;
• FIG. 2 is a diagram showing the functional configuration of a radiation imaging control device according to the present embodiment. Diagram for explaining the region of interest in the chest A flowchart showing the processing performed in this embodiment. A flowchart showing the process performed in another embodiment.
• FIG. 1 is a schematic block diagram showing the configuration of a radiographic imaging system to which a radiographic imaging control device according to this embodiment of the present disclosure is applied.
• the radiographic imaging system according to this embodiment includes an imaging device 1 and a radiographic imaging control device 10 according to this embodiment.
• the imaging device 1 includes a radiation source 3 and a layered detector 4.
• the layered detector 4 is constructed by stacking, from the side closest to the radiation source 3, a first radiation detector 5, a radiation energy conversion filter 7 made of a copper plate or the like, and a second radiation detector 6.
• the imaging device 1 can perform energy subtraction using a so-called one-shot method in which radiation such as X-rays emitted from the radiation source 3 and transmitted through the subject H to be imaged is irradiated at different energies to the first radiation detector 5 and the second radiation detector 6.
• radiation such as X-rays emitted from the radiation source 3 and transmitted through the subject H to be imaged is irradiated at different energies to the first radiation detector 5 and the second radiation detector 6.
• the first radiation detector 5 of the layered detector 4 it is possible to obtain a radiation image by simply imaging the subject H.
• energy subtraction is a process that takes advantage of the fact that the amount of attenuation of transmitted radiation differs depending on the material that makes up the subject, and uses two radiological images obtained by irradiating the subject with two types of radiation with different energy distributions to generate images that extract different tissues within the subject (e.g. soft tissue and bone).
• FIG. 2 is a diagram showing the schematic configuration of the first and second radiation detectors. Note that when there is no need to distinguish between the first and second radiation detectors, they may simply be referred to as radiation detectors. As shown in FIG. 2, the radiation detectors 5 and 6 have a pixel region 30, a gate driver 31, a signal processing circuit 32, a control unit 34, and a communication interface (I/F) 35.
• I/F communication interface
• the pixel region 30 has a plurality of normal pixels 40A arranged in a matrix along the mutually orthogonal X and Y directions.
• the normal pixels 40A are pixels for image generation that detect radiation and generate a radiological image.
• the pixel region 30 also has a plurality of dose detection pixels 40B.
• the dose detection pixels 40B are pixels for detecting the dose of radiation irradiated to the radiation detectors 5 and 6.
• Normal pixel 40A has a photoelectric conversion unit 41 that generates and accumulates electric charges by photoelectrically converting visible light converted by the scintillator, and a TFT 42 that serves as a switching element.
• the photoelectric conversion unit 41 has, for example, a PIN (p-intrinsic-n) type semiconductor layer, an upper electrode arranged on the upper side of the semiconductor layer, and a lower electrode arranged on the lower side of the semiconductor layer. A bias voltage is applied to the upper electrode.
• the lower electrode is connected to a TFT (Thin Film Transistor) 42.
• the dose detection pixel 40B has a photoelectric conversion unit 41 and a TFT 42, similar to the normal pixel 40A. However, in the dose detection pixel 40B, the source electrode and drain electrode of the TFT 42 are shorted.
• the dose detection pixel 40B is a pixel used to detect the amount of radiation that passes through the subject H and enters the imaging surfaces of the radiation detectors 5 and 6, and functions as an AEC sensor for stopping the irradiation of radiation, as described below.
• the dose detection pixels 40B account for approximately a few percent of the pixels contained in the imaging surface of the radiation detectors 5 and 6.
• the dose detection pixels 40B are preferably arranged so as to be evenly scattered across the imaging surface without being locally biased within the imaging surface.
• the dose detection pixels 40B are preferably arranged so as to be evenly distributed within the imaging surface at intervals of several pixels.
• the positions of the dose detection pixels 40B are known when the radiation detectors 5 and 6 are manufactured, and are preferably stored in advance in a non-volatile memory, which will be described later.
• the dose detection pixels 40B may be arranged in a locally concentrated manner, and the arrangement of the dose detection pixels 40B can be changed as appropriate.
• pixels 40 when there is no need to distinguish between the normal pixels 40A and the dose detection pixels 40B, these will be simply referred to as pixels 40.
• the dose detection pixels 40B are arranged vertically and horizontally at intervals of several pixels in place of the normal pixels for image detection of the radiation detectors 5 and 6, but this is not limited thereto and they may be arranged in the gaps between the normal pixels 40A. In this case, since it is not necessary to use the positions of the normal pixels as the dose detection pixels 40B, the pixel density can be increased accordingly.
• the pixel region 30 has a plurality of scanning lines 43 extending in the X direction and a plurality of signal lines 44 extending in the Y direction.
• the scanning lines 43 and the signal lines 44 are wired in a grid pattern.
• Each pixel 40 is connected to an intersection of the scanning line 43 and the signal line 44.
• the gate electrode of the TFT 42 is connected to the scanning line 43
• the source electrode of the TFT 42 is connected to the signal line 44.
• the drain electrode of the TFT 42 is connected to the photoelectric conversion unit 41.
• Each scanning line 43 is commonly connected to one pixel row's worth of pixels 40.
• Each signal line 44 is commonly connected to one pixel column's worth of pixels 40.
• Each scanning line 43 is connected to a gate driver 31.
• Each signal line 44 is connected to a signal processing circuit 32.
• the gate driver 31 sequentially supplies gate pulses as scanning signals to each scanning line 43.
• the gate pulses supplied to the scanning line 43 are applied to the gate electrodes of the TFTs 42 included in the pixels 40 connected to the scanning line 43.
• the charge stored in the photoelectric conversion unit 41 of the normal pixel 40A is output to the signal line 44 when the TFT 42 is turned on.
• the source electrode and drain electrode of the TFT 42 are shorted, so the charge generated in the photoelectric conversion unit 41 of the dose detection pixel 40B is output to the signal line 44 regardless of the switching state of the TFT 42.
• the signal processing circuit 32 has an integrator as a charge amplifier, a CDS (correlated double sampling) circuit, and an analog/digital (A/D) converter.
• the signal processing circuit 32 accumulates the charge input from each pixel 40 via the signal line 44 using an integrator, and then performs correlated double sampling using a CDS circuit.
• the signal processing circuit 32 then converts the pixel signal, from which the reset noise components have been removed by correlated double sampling, into a digital signal using an A/D converter.
• the signal processing circuit 32 generates image data for a radiation image based on pixel signals read out from each normal pixel 40A in the pixel region 30. Meanwhile, charge generated in the dose detection pixel 40B constantly flows into an integrator on a signal line to which the dose detection pixel 40B in the signal processing circuit 32 is connected. The signal processing circuit 32 generates dose data for performing dose control, as described below, based on the pixel signals read out from the dose detection pixel 40B.
• the control unit 34 is configured with a microcomputer and includes a CPU (Central Processing Unit), a memory, and a storage device.
• the control unit 34 performs control for radiographic image capture by executing a program stored in the memory with the CPU.
• the control unit 34 controls each part of the gate driver 31, the signal processing circuit 32, and the communication I/F 35.
• the control unit 34 controls the gate driver 31 and signal processing circuit 32 to perform a reset operation of the charge accumulated in the normal pixels 40A. Specifically, the control unit 34 causes the gate driver 31 to supply a gate pulse to each scanning line 43, thereby outputting the accumulated charge of each normal pixel 40A to the signal line 44, and the signal processing circuit 32 discards the charge. After the reset operation is completed, the control unit 34 turns off all TFTs 42, thereby putting the normal pixels 40A into a charge accumulation state.
• the control unit 34 puts the normal pixels 40A into a charge accumulation state, and after the irradiation of radiation is stopped as described below, controls the gate driver 31 to read out pixel signals from the normal pixels 40A to the signal processing circuit 32, thereby generating image data for the radiation image. Furthermore, when imaging is started, the control unit 34 controls the signal processing circuit 32 to generate dose data from the charges generated in the dose detection pixels 40B. The control unit 34 outputs the radiation image and dose data to the radiation imaging control device 10 via the communication I/F 35.
• the first and second radiation detectors 5, 6 included in the layer structure detector 4 described above are switched and used depending on the imaging purpose. That is, when the imaging purpose is simple imaging to obtain one radiation image of the subject H, only the first radiation detector 5, which is closer to the radiation source 3, is used. On the other hand, when the imaging purpose is energy subtraction imaging, both the first radiation detector 5 and the second radiation detector 6 are used.
• the radiography control device 10 is a computer such as a workstation, a server computer, or a personal computer, and includes a CPU (Central Processing Unit) 11, a non-volatile storage 13, and a memory 16 as a temporary storage area.
• the radiography control device 10 also includes a display 14 such as a liquid crystal display, an input device 15 such as a keyboard and a mouse, and a network I/F (InterFace) 17 connected to a network (not shown).
• the radiography control device 10 also includes a high-voltage generator 18 and an exposure switch 19 connected to the radiation source 3.
• the CPU 11, the storage 13, the display 14, the input device 15, the memory 16, the network I/F 17, the high-voltage generator 18, and the exposure switch 19 are connected to a bus 20.
• the radiation detectors 5 and 6 are also connected to the bus 20.
• the CPU 11 is an example of a processor in this disclosure.
• the storage 13 is realized by a HDD (Hard Disk Drive), SSD (Solid State Drive), flash memory, etc.
• the storage 13 as a storage medium stores the radiation imaging control program 12 installed in the radiation imaging control device 10.
• the CPU 11 reads out the radiation imaging control program 12 from the storage 13, expands it into the memory 16, and executes the expanded radiation imaging control program 12.
• the high-voltage generator 18 uses a transformer to boost the input voltage to generate a high-voltage tube voltage, which is then supplied to the radiation source 3 via a high-voltage cable.
• the irradiation switch 19 is, for example, a two-stage switch operated by an operator such as a radiologist. When pressed in the first stage, it generates a warm-up start signal to start warming up the radiation source 3, and when pressed in the second stage, it generates an irradiation start signal to start irradiation with the radiation source 3.
• the radiation imaging control program 12 is stored in a storage device of a server computer connected to the network or in a network storage in a state accessible from the outside, and is downloaded and installed in response to a request into a computer constituting the radiation imaging control device 10.
• the program is recorded on a recording medium such as a DVD (Digital Versatile Disc) or a CD-ROM (Compact Disc Read Only Memory) and distributed, and is installed into the computer constituting the radiation imaging control device 10 from the recording medium.
• FIG. 5 is a diagram showing the functional configuration of the radiation imaging control device according to this embodiment.
• the radiation imaging control device 10 includes a dose control unit 21, a device control unit 22, a subtraction unit 23, and a display control unit 24.
• the CPU 11 executes the radiation imaging control program 12 to function as the dose control unit 21, the device control unit 22, the subtraction unit 23, and the display control unit 24.
• the dose control unit 21 controls radiography by irradiating the subject H with radiation. Specifically, it drives the radiation source 3 by controlling the tube voltage that determines the energy spectrum of the radiation emitted by the radiation source 3, the tube current that determines the irradiation dose per unit time, the start, stop or end of irradiation by the radiation source 3, and the irradiation time of the radiation. That is, the dose control unit 21 starts the power supply from the high voltage generator 18 to the radiation source 3 when it receives an irradiation start signal from the irradiation switch 19, and stops the power supply from the high voltage generator 18 to the radiation source 3 when the irradiated dose reaches the target dose, thereby stopping the irradiation of radiation by the radiation source 3.
• the storage 13 stores several types of imaging conditions, such as tube voltage and tube current, in advance according to the imaging region, etc.
• the imaging conditions are manually set by the operator through the input device 15.
• the dose control unit 21 irradiates radiation with the tube voltage and tube current irradiation time product of the set imaging conditions.
• the dose control unit 21 functions to stop the irradiation of radiation even if it is below the tube current irradiation time product (irradiation time) that was intended to be irradiated based on the imaging conditions.
• the maximum value of the tube current irradiation time product (or irradiation time) is set as the imaging condition of the radiation source 3.
• the set tube current irradiation time product be a value according to the imaging region.
• the dose control unit 21 acquires the imaging purpose for dose control.
• Imaging purposes include, for example, simple imaging for acquiring one radiation image of the subject H, and energy subtraction imaging.
• the imaging purpose is set by the operator through the input device 15.
• the imaging purpose is simple imaging, only the first radiation detector 5 on the side closer to the radiation source 3 in the layered structure detector 4 is used to acquire a radiation image.
• the imaging purpose is energy subtraction imaging, both the first radiation detector 5 and the second radiation detector 6 are used, and the first radiation detector 5 acquires a first radiation image G1, and the second radiation detector 6 acquires a second radiation image G2.
• the dose control unit 21 determines the radiation detector to be used for dose control depending on the imaging purpose. If the imaging purpose is simple imaging, the first radiation detector 5 is determined to be the radiation detector to be used for dose control. If the imaging purpose is energy subtraction imaging, the dose control unit 21 determines the second radiation detector 6 to be the radiation detector to be used for dose control so that a sufficient dose of radiation is irradiated to the second radiation detector 6, which is farther from the radiation source 3.
• a target dose for radiation imaging may be determined, and dose control may be performed so that the subject H is irradiated with the target dose of radiation.
• the target dose is determined so that the lung field has the desired image quality in the radiation image obtained by simple imaging. This results in the generation of a radiation image in which the lung field has high image quality.
• the target dose can be set as follows. That is, chest phantoms of various thicknesses, formed from materials such as acrylic that have a similar radiation attenuation coefficient to the human body, are photographed while changing the dose. Then, when the lung field has the desired image quality in the radiation image acquired by the first radiation detector 5, the average delivered dose in the lung field region is set as the target dose and saved in storage 13. When actually photographing, the target dose according to the purpose of photographing that has been saved in storage 13 can be read from storage 13 and used.
• the target dose is determined so that the lung field, which is the region of interest, has the desired image quality in the radiation image acquired by the second radiation detector 6 farther from the radiation source 3. This ensures the image quality of the lung field in the radiation images acquired by both the first radiation detector 5 and the second radiation detector 6. Therefore, by the energy subtraction process, it is possible to derive a bone image in which soft tissue has been sufficiently removed in the lung field, and a soft tissue image in which bone has been sufficiently removed in the lung field.
• the target dose can be set as follows. That is, chest phantoms of various thicknesses are imaged while changing the dose, and when the lung field has the desired image quality in the radiation image acquired by the second radiation detector 6, the average delivered dose in the lung field region is set as the target dose and saved in storage 13.
• the target dose according to the imaging purpose that has been saved in storage 13 can be read from storage 13 and used.
• the imaging purpose is energy subtraction imaging
• the dose may be insufficient in the mediastinum and under the diaphragm.
• a bone image is derived by energy subtraction processing, it is not possible to accurately separate the vertebrae and soft tissue present in the mediastinum and under the diaphragm.
• the mediastinum and under the diaphragm other than the lung field may be used as the region of interest in the radiographic image acquired by the second radiation detector 6 farther from the radiation source 3, and a target dose may be determined so that the mediastinum and under the diaphragm have a desired image quality. This ensures the image quality of the entire image in the radiographic images acquired by both the first radiation detector 5 and the second radiation detector 6.
• whether the lung field or the mediastinum and subdiaphragm are to be the regions of interest can be set based on input from the operator via the input device 15.
• a region of interest in the subject H may be specified depending on the purpose of imaging, and in the radiation detector used for dose control, dose control may be performed according to the dose detected by the dose detection pixel 40B located at a position corresponding to the region of interest.
• dose control is performed in the radiation detectors 5 and 6 according to the dose detected by the dose detection pixel 40B located in a region 51 in the radiation image corresponding to the lung field.
• dose control is performed in accordance with the dose detected by the dose detection pixel 40B located in the region 52 in the radiation detectors 5, 6 that corresponds to the mediastinum and below the diaphragm in the radiation image.
• the dose control unit 21 derives a cumulative histogram of dose data for each dose detection pixel 40B and identifies the subject area based on the cumulative histogram. Then, when using the dose detection pixel 40B corresponding to the lung field, the dose control unit 21 derives a cumulative histogram of dose data for each dose detection pixel 40B in the identified subject area, and performs dose control using the dose data acquired by the dose detection pixel 40B on the high dose side, which is 80-90% in the cumulative histogram.
• a cumulative histogram of dose data is derived for each dose detection pixel 40B in the identified subject region, and dose control can be performed using the dose data acquired by the dose detection pixels 40B on the low dose side, which is 20-40% of the cumulative histogram.
• the dose detection pixels 40B corresponding to the lung field or the mediastinum and below the diaphragm may be specified in advance, and dose control may be performed using the dose detection pixels 40B specified according to the region of interest.
• the imaging part is an extremity or the like
• the first radiation detector 5 is determined to be the radiation detector for dose control
• the imaging purpose is energy subtraction imaging
• the second radiation detector 6 is determined to be the radiation detector for dose control.
• the region of interest is often the bone.
• the subject region is identified based on the cumulative histogram of the dose data, and in the identified subject region, a cumulative histogram of the dose data is derived for each dose detection pixel 40B, and dose control is performed using the dose data acquired by the dose detection pixel 40B on the low dose side, which is 20-40% on the cumulative histogram.
• the device control unit 22 controls the operations of the first and second radiation detectors 5, 6 in response to input operations from an operator via the input device 15. Specifically, the device control unit 22 performs various controls such as turning on and off the power of the radiation detectors 5, 6 and switching between standby mode and imaging mode. In addition, the device control unit 22 preferably has a function of performing various image processing such as offset correction, sensitivity correction, and defect correction on the radiation images acquired by the first and second radiation detectors 5, 6.
• the subtraction unit 23 performs weighted subtraction between corresponding pixels on the first radiographic image G1 acquired by the first radiation detector 5 and the second radiographic image G2 acquired by the second radiation detector 6, as shown in the following equations (1) and (2), to derive a bone image Gb from which only the bones of the subject H contained in the first radiographic image G1 and the second radiographic image G2 have been extracted, and a soft tissue image Gs from which only the soft tissue has been extracted.
• ⁇ 1 and ⁇ 2 in the following equations (1) and (2) are weighting coefficients, which are derived based on attenuation coefficients corresponding to the radiation energy of the soft tissue and bones of the subject H.
• Gb(x,y) G1(x,y) ⁇ 1 ⁇ G2(x,y) (1)
• Gs (x, y) G2 (x, y) - ⁇ 2 ⁇ G1 (x, y) (2)
• the display control unit 24 displays the acquired radiographic image on the display 14. That is, when the purpose of imaging is simple imaging, the display control unit 24 displays the radiographic image acquired by the first radiation detector 5 on the display 14. When the purpose of imaging is energy subtraction imaging, the display control unit 24 displays the bone image Gb and the soft tissue image Gs on the display 14.
• FIG. 7 is a flowchart showing the processing performed in this embodiment.
• the dose control unit 21 acquires the imaging purpose input by the operator through the input device 15 (step ST1), and identifies at least one radiation detector to be used for dose control (step ST2).
• the dose control unit 21 also determines the target dose to be irradiated to the subject H according to the imaging purpose (step ST3), and identifies the region of interest in the subject H according to the imaging purpose (step ST4).
• the exposure switch 19 is operated, and the dose control unit 21 drives the radiation source 3 to start irradiating radiation (step ST5).
• the dose control unit 21 determines whether the dose during imaging has reached the target dose based on the dose data detected by the dose detection pixel 40B located at a position corresponding to the region of interest in the radiation detector for dose control (step ST6).
• step ST6 If step ST6 is negative, radiation irradiation continues. If step ST6 is positive, the dose control unit 21 stops the irradiation of radiation by the radiation source 3 (step ST7).
• the device control unit 22 acquires a radiological image from the radiation detector according to the purpose of imaging, and performs energy subtraction processing if necessary.
• the display control unit 24 displays the acquired radiological image or bone image and soft tissue image on the display 14 (image display: step ST8), and the process ends.
• the multiple radiation detectors 5, 6 included in the layered structure detector 4 at least one radiation detector is determined to be used for radiation dose control according to the imaging purpose, and dose control is performed according to the dose detected by the dose detection pixel 40B of the determined radiation detector. Therefore, when performing radiation imaging using the layered structure detector 4, high-quality plain radiation images, bone images, or soft tissue images can be obtained. Note that in the following, when there is no need to distinguish between plain radiation images, bone images, and soft tissue images, they may simply be referred to as radiation test images.
• a high-quality simple radiation image can be obtained by determining, of the multiple radiation detectors 5 and 6, the first radiation detector 5 that is closest to the radiation source 3 as the radiation detector that performs radiation dose control.
• the purpose of imaging is energy subtraction imaging
• the second radiation detector 6, other than the first radiation detector 5 closest to the radiation source 3, among the multiple radiation detectors 5, 6 as the radiation detector that performs radiation dose control it is possible to irradiate the second radiation detector 6, which is farther from the radiation source 3, with a sufficient dose of radiation. Therefore, it is possible to obtain high-quality bone and soft tissue images.
• a radiological image with high image quality for the region of interest can be obtained.
• the second radiation detector 6, which is farther from the radiation source 3 is determined to be the radiation detector to be used for radiation source control, but this is not limited to this. Both the first radiation detector 5 and the second radiation detector 6 may be determined to be the radiation detectors to be used for radiation source control. This will be described below as another embodiment.
• the first radiation detector 5, which is closer to the radiation source 3, receives a larger dose than the second radiation detector 6, so there is a possibility that pixel values on the high density side will saturate in the radiation image acquired by the first radiation detector 5.
• the S/N ratio will deteriorate in the radiation image acquired by the second radiation detector 6 due to an insufficient dose.
• the dose control unit 21 may determine both the first radiation detector 5 and the second radiation detector 6 as radiation detectors for dose control.
• the dose control unit 21 when the imaging site of the subject H is the chest and the region of interest is the lung field, the dose control unit 21 performs dose control according to the dose detected by the dose detection pixel 40B located in a region corresponding to the lung field in the first radiation detector 5. Also, the dose control unit 21 performs dose control according to the dose detected by the dose detection pixel 40B located in a region corresponding to the mediastinum and below the diaphragm in the second radiation detector 6.
• the dose control unit 21 presets an upper limit dose, which is the upper limit at which the pixel values of the radiation image do not become saturated, and controls the driving of the radiation source 3 to stop irradiating radiation when the dose detected by the dose detection pixels 40B corresponding to the lung field region in the first radiation detector 5 reaches the upper limit dose, or when the dose detected by the dose detection pixels 40B corresponding to the mediastinum and subdiaphragm in the second radiation detector 6 reaches the target dose.
• an upper limit dose which is the upper limit at which the pixel values of the radiation image do not become saturated
• FIG. 8 is a flowchart showing the processing performed in another embodiment.
• the dose control unit 21 acquires the imaging purpose input by the operator through the input device 15 (step ST11), and identifies at least one radiation detector to be used for dose control (step ST12).
• the imaging purpose is energy subtraction imaging
• both the first radiation detector 5 and the second radiation detector 6 are identified as the radiation detectors to be used for dose control.
• the dose control unit 21 determines a target dose to be irradiated to the subject H according to the imaging purpose (step ST13), and identifies a region of interest in the subject H according to the imaging purpose (step ST14).
• the region of interest is the lung field.
• the exposure switch 19 is operated, causing the dose control unit 21 to drive the radiation source 3 to start irradiating radiation (step ST15).
• the dose control unit 21 determines whether the dose irradiated to the subject H has reached the upper dose limit based on the dose data detected by the dose detection pixels 40B located in the first radiation detector 5 at positions corresponding to the region of interest (step ST16). If step ST16 is negative, the dose control unit 21 determines whether the dose during imaging has reached the target dose based on the dose data detected by the dose detection pixels 40B located in the second radiation detector 6 at positions corresponding to the mediastinum and below the diaphragm (step ST17).
• step ST17 If step ST17 is negative, the process returns to step ST16 and radiation irradiation continues. If steps ST16 and ST17 are positive, the dose control unit 21 stops the irradiation of radiation by the radiation source 3 (step ST18).
• the device control unit 22 acquires a radiological image from the radiation detector according to the purpose of imaging, and the subtraction unit 23 performs energy subtraction processing.
• the display control unit 24 displays the bone image and soft tissue image derived by the energy subtraction processing on the display 14 (image display: step ST19), and the processing ends.
• the dose can be controlled so that areas of high density in the radiation image do not become saturated, as occurs when the region of interest is the lung field. This makes it possible to obtain high-quality radiation images.
• the radiation in the above embodiment is not particularly limited, and in addition to X-rays, alpha rays, gamma rays, etc. can be used.
• the various processors shown below can be used as the hardware structure of the processing unit that executes various processes, such as the dose control unit 21, device control unit 22, subtraction unit 23, and display control unit 24.
• the various processors include a CPU, which is a general-purpose processor that executes software (programs) and functions as various processing units, as well as a programmable logic device (PLD), which is a processor whose circuit configuration can be changed after manufacture, such as an FPGA (Field Programmable Gate Array), and a dedicated electrical circuit, such as an ASIC (Application Specific Integrated Circuit), which is a processor with a circuit configuration designed specifically to execute specific processes.
• a CPU which is a general-purpose processor that executes software (programs) and functions as various processing units
• PLD programmable logic device
• FPGA Field Programmable Gate Array
• ASIC Application Specific Integrated Circuit
• a single processing unit may be configured with one of these various processors, or may be configured with a combination of two or more processors of the same or different types (e.g., a combination of multiple FPGAs or a combination of a CPU and an FPGA). Also, multiple processing units may be configured with a single processor.
• processors As an example of configuring multiple processing units with one processor, first, as represented by computers such as a client and a server, one processor is configured with a combination of one or more CPUs and software, and this processor functions as multiple processing units. Second, as represented by a system on chip (SoC), a processor is used that realizes the functions of the entire system including multiple processing units with one IC (Integrated Circuit) chip. In this way, various processing units are configured using one or more of the above various processors as a hardware structure.
• SoC system on chip
• the hardware structure of these various processors can be an electrical circuit that combines circuit elements such as semiconductor elements.
• a radiography control device that controls radiography of an object by irradiating the object with radiation emitted from a radiation source, comprising: a layered detector including a plurality of radiation detectors stacked together, each having a plurality of dose detection pixels for detecting a dose during radiation imaging; at least one processor; The processor, Obtain the purpose of the shoot, determining at least one radiation detector to be used for controlling a dose of the radiation during the radiation imaging, among the plurality of radiation detectors, according to the imaging purpose; a radiation imaging control device that performs the dose control in accordance with the determined dose detected by the dose detection pixels of the radiation detector.
• the radiation imaging control device according to claim 1, wherein, when the imaging purpose is simple imaging, the processor determines, among the plurality of radiation detectors, the radiation detector closest to the radiation source as the radiation detector that will perform the dose control. (Additional Note 3) 2. The radiation imaging control device according to claim 1, wherein, when the imaging purpose is energy subtraction imaging, the processor determines, among the plurality of radiation detectors, a radiation detector other than a radiation detector closest to the radiation source as the radiation detector that will perform the dose control. (Additional Note 4) 2. The radiation imaging control device according to claim 1, wherein the processor determines, when the imaging purpose is energy subtraction imaging, that all of the plurality of radiation detectors are to be the radiation detectors that perform the dose control.
• the processor determines a target dose when performing the radiation imaging in accordance with the imaging purpose; 5.
• the radiation imaging control device according to claim 1, wherein when the determined dose detected by the dose detection pixels of the radiation detector reaches the target dose, driving of the radiation source is stopped.
• the processor identifies a region of interest in the subject according to the imaging purpose; 6.
• a radiation imaging control device according to claim 1, wherein the radiation detector that is determined to be the radiation detector for controlling the dose of radiation performs the dose control in accordance with the dose detected by the dose detection pixel that is at least located at a position corresponding to the region of interest.
• a radiation imaging control method for a radiation imaging control device that controls radiation imaging of an object by irradiating the object with radiation emitted from a radiation source, the radiation imaging control device including a layered detector configured by stacking a plurality of radiation detectors, each having a plurality of dose detection pixels that detect a dose during radiation imaging, the method comprising: Get the purpose of the shoot, determining at least one radiation detector to be used for controlling a dose of the radiation during the radiation imaging, among the plurality of radiation detectors, according to the imaging purpose; A radiation imaging control method for performing the dose control in accordance with the determined dose detected by the dose detection pixels of the radiation detector.
• a radiation imaging control method for a radiation imaging control device that controls radiation imaging of an object by irradiating the object with radiation emitted from a radiation source, the radiation imaging control device including a layered detector configured by stacking a plurality of radiation detectors, each having a plurality of dose detection pixels that detect a dose during radiation imaging, the method comprising: The procedure for obtaining the purpose of photography; determining at least one radiation detector to be used for controlling a dose of the radiation during the radiation imaging, among the plurality of radiation detectors, according to the imaging purpose; and a procedure for performing the dose control in accordance with the determined dose detected by the dose detection pixels of the radiation detector.
• Imaging device 3 Radiation source 4 Layer structure detector 5, 6 Radiation detector 7 Radiation energy conversion filter 10 Radiation imaging control device 11 CPU 12 Radiography control processing program 13 Storage 14 Display 15 Input device 16 Memory 17 Network I/F 18 High voltage generator 19 Exposure switch 20 Bus 21 Radiation source control unit 22 Device control unit 23 Subtraction unit 24 Display control unit 30 Pixel area 31 Gate driver 32 Signal processing circuit 34 Control unit 35 Communication I/F 40 Pixel 40A Normal pixel 40B Detection pixel 41 Photoelectric conversion unit 42 TFT 43 Scanning line 44 Signal line 51 Region corresponding to lung field 52 Region corresponding to mediastinum and subdiaphragm G1, G2 Radiation image Gb Bone image Gs Soft tissue image H Subject

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