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
  • A61B6/42—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
  • A61B6/4233—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector using matrix detectors
• • 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
  • A61B6/4241—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector using energy resolving detectors, e.g. photon counting
• • 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
  • A61B6/54—Control of apparatus or devices for radiation diagnosis
  • A61B6/545—Control of apparatus or devices for radiation diagnosis involving automatic set-up of acquisition parameters
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
  • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
  • G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2223/00—Investigating materials by wave or particle radiation
  • G01N2223/30—Accessories, mechanical or electrical features
  • G01N2223/306—Accessories, mechanical or electrical features computer control
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2223/00—Investigating materials by wave or particle radiation
  • G01N2223/40—Imaging
  • G01N2223/401—Imaging image processing

Definitions

• This disclosure relates to a radiography control device, method, and program.
• JP 2019-058608 A proposes a method of deriving the amount of signal contained in a radiographic image based on the distribution of primary rays in the radiographic image based on the capture conditions, or based on the capture conditions and the body thickness distribution of the subject of the radiographic image, outputting the ratio of the derived signal amount to the amount of noise contained in the radiographic image as an index value for the dose of radiation irradiated in capturing the radiographic image, and determining whether the dose of radiation irradiated in capturing the radiographic image is excessive or insufficient based on the index value and a predetermined target value, and outputting the determination result.
• 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. For this reason, 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, reducing the image quality of the radiation image acquired by the energy subtraction processing.
• 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 layered structure detector.
• a radiography control device includes at least one processor, The processor performs radiography by irradiating a layered detector formed by stacking a plurality of radiation detectors with radiation emitted from a radiation source and transmitted through a subject to be imaged, thereby acquiring a plurality of radiographic images using the plurality of radiation detectors; determining whether radiation was excessive or insufficient during radiography by using at least one of the plurality of radiographic images as a determination radiographic image; The result of the excess or shortage determination will be notified.
• the processor may determine whether radiation is excessive or insufficient by using a radiation image acquired by one of the multiple radiation detectors other than the radiation detector closest to the radiation source as a determination radiation image.
• the processor identifies a subject area of the determination radiographic image, If the pixel value of at least a part of the subject area is less than a reference pixel value, or the amount of granular noise in at least a part of the subject area exceeds a reference amount, it may be determined that the dose of radiation irradiated to one radiation detector is insufficient.
• the processor detects an artifact region included in the determination radiographic image,
• the area excluding the artificial object area may be specified as the subject area.
• the processor derives a reduced image of the determination radiographic image, It may be possible to determine whether or not the pixel value of at least a part of the subject area is less than a reference pixel value based on the reduced image.
• the processor may determine whether or not the amount of granular noise in at least a portion of the subject area exceeds a reference amount based on the high-frequency components of the determination radiographic image.
• the processor may determine whether the radiation is excessive or insufficient by using a radiographic image acquired by the radiation detector that is closest to the radiation source among the multiple radiation detectors as an additional radiographic image for determination.
• the processor may determine that the dose is excessive if at least a portion of the pixel values in an area corresponding to the subject area in the further determination radiographic image are saturated.
• the processor when it is determined that the radiation dose is excessive or insufficient, the processor derives a dose setting value for setting the pixel value of the object region to a target value; It may also notify the dose setting value.
• a radiography control method includes performing radiography by irradiating a layered detector formed by stacking a plurality of radiation detectors with radiation emitted from a radiation source and transmitted through an object to be imaged, thereby obtaining a plurality of radiographic images using the plurality of radiation detectors; determining whether radiation was excessive or insufficient during radiography by using at least one of the plurality of radiographic images as a determination radiographic image; The result of the excess or shortage determination will be notified.
• a radiography control program includes a step of performing radiography in which radiation emitted from a radiation source and transmitted through an object to be imaged is irradiated onto a layered detector formed by stacking a plurality of radiation detectors, thereby acquiring a plurality of radiographic images using the plurality of radiation detectors; a step of determining whether radiation is excessive or insufficient during radiation imaging by using at least one of the plurality of radiation images as a determination radiation image; The computer is caused to execute a procedure of notifying the result of the determination of whether the amount is insufficient or excessive.
• 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 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.
• FIG. 13 is a histogram for explaining subject region specification.
• a diagram for explaining identification of a subject region is a diagram for explaining acquisition of a pixel value profile.
• FIG. 1 is a diagram for explaining derivation of a dose setting value in the case of insufficient dose.
• a diagram for explaining the derivation of the dose setting value in the case of an excessive dose A diagram showing the display screen when the dose is appropriate
• a diagram showing the display screen when the dose is insufficient Diagram showing the display screen in case of excessive radiation exposure
• 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).
• the first and second radiation detectors 5, 6 are capable of repeatedly recording and reading out radiation images, and may be so-called direct type radiation detectors that generate electric charges by directly receiving radiation, or so-called indirect type radiation detectors that first convert radiation into visible light and then convert the visible light into an electric charge signal.
• a method for reading out the radiation image signal it is preferable to use a so-called TFT readout method in which the radiation image signal is read out by turning a TFT (thin film transistor) switch on and off, or a so-called optical readout method in which the radiation image signal is read out by irradiating it with readout light, but this is not limiting and other methods may also be used.
• 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 boosts the input voltage using a transformer to generate a high 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 radiography control program 12 is stored in a state accessible from the outside in the storage device of a server computer connected to the network or in network storage, and is downloaded and installed on the computer that constitutes the radiography control device 10 upon request. Alternatively, it is recorded on a recording medium such as a DVD (Digital Versatile Disc) or CD-ROM (Compact Disc Read Only Memory) and distributed, and is installed from the recording medium on the computer that constitutes the radiography control device 10.
• a recording medium such as a DVD (Digital Versatile Disc) or CD-ROM (Compact Disc Read Only Memory) and distributed, and is installed from the recording medium on the computer that constitutes the radiography control device 10.
• FIG. 3 is a diagram showing the functional configuration of the radiation imaging control device according to this embodiment.
• the radiation imaging control device 10 includes an imaging control unit 21, a device control unit 22, a determination unit 23, a dose setting unit 24, a subtraction unit 25, and a display control unit 26.
• the CPU 11 executes the radiation imaging control program 12 to function as the imaging control unit 21, the device control unit 22, the determination unit 23, the dose setting unit 24, the subtraction unit 25, and the display control unit 26.
• the imaging 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 radiation. That is, the imaging 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 based on the imaging conditions, 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 area, etc.
• the imaging conditions are manually set by the operator via the input device 15.
• the imaging control unit 21 irradiates radiation with the tube voltage and tube current irradiation time product of the imaging conditions that have been set.
• the imaging control unit 21 acquires the imaging purpose.
• Imaging purposes include, for example, simple imaging for acquiring one radiation image of the subject H, and energy subtraction imaging.
• the imaging purpose is input by the operator through the input device 15.
• the imaging purpose is simple imaging, only the first radiation detector 5, which is closer to the radiation source 3 in the layered structure detector 4, is used to acquire a radiation image (hereinafter referred to as simple radiation image G0).
• 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 device control unit 22 controls the operation of the first and second radiation detectors 5, 6 in response to input operations from the operator via the input device 15. Specifically, the device control unit 22 performs various controls such as turning the power of the radiation detectors 5, 6 on and off, 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 determination unit 23 uses at least one of the first radiographic image G1 acquired by the first radiation detector 5 and the second radiographic image G2 acquired by the second radiation detector as a determination radiographic image to determine whether the radiation dose during radiography is excessive or insufficient, and derives a determination result of whether the radiation dose is excessive or insufficient.
• the judgment unit 23 judges whether the dose is excessive or insufficient by using the simple radiographic image G0 acquired by the first radiation detector 5 as the judgment radiographic image.
• the judgment unit 23 judges whether the dose is excessive or insufficient by using the first radiographic image G1 acquired by the first radiation detector 5 and the second radiographic image G2 acquired by the second radiation detector 5 as judgment radiographic images.
• the method described in JP 2019-058608 A may be used to determine whether the dose is excessive or insufficient. That is, the determination unit 23 derives the amount of signals contained in the simple radiographic image G0 based on the distribution of primary rays in the simple radiographic image G0 based on the imaging conditions, or based on the imaging conditions and the body thickness distribution of the subject H in the simple radiographic image G0, outputs the ratio of the derived signal amount to the amount of noise contained in the simple radiographic image G0 as an index value for the dose of radiation irradiated in simple radiography, and determines whether the dose of radiation is excessive or insufficient based on the index value and the target dose based on the imaging conditions.
• the determination unit 23 identifies the subject area of the second radiation image G2, which is acquired by the second radiation detector 6 on the side farther from the radiation source 3, from among the radiation images for determination.
• the determination unit 23 identifies the subject area of the second radiation image G2 based on the histogram of the second radiation image G2.
• FIG. 4 is a diagram showing a histogram for explaining the identification of the subject area. As shown in FIG. 4, in the histogram 40, the horizontal axis represents the signal value of the radiation image, and the vertical axis represents the frequency of the signal value.
• the area in the radiation image where the radiation is directly irradiated to the radiation detector without passing through the subject H has a high density in the radiation image. Furthermore, when imaging is performed using an irradiation field aperture, radiation is not irradiated to areas other than the irradiation field in the radiation detector, and the pixel value of the radiation image is 0. Furthermore, if an artificial object made of metal such as a screw is included in the subject H, the artificial object has a high brightness in the radiation image because it is difficult for radiation to pass through the artificial object.
• the determination unit 23 sets a minimum density value Dmin that is, for example, 10-20% from the low density (high luminance) side in the histogram 40, and sets a maximum density value Dmax that is 10-20% from the high density (low luminance) side.
• the determination unit 23 then identifies, as the subject region, an area in the second radiographic image G2 that has a density in the range from the minimum density value Dmin to the maximum density value Dmax.
• FIG. 5 is a diagram for explaining the determination of the subject region. As shown in FIG. 5, the region excluding the direct radiation region 41 and the region 42 of artificial objects such as screws embedded in the vertebrae in the second radiographic image G2 is determined as the subject region GH2. Note that no irradiation field aperture was used when acquiring the second radiographic image G2 shown in FIG. 5.
• a machine-learned discriminator may be used to discriminate the direct radiation region and the irradiation field region in the radiographic image and identify the subject region.
• the discriminator is generated by machine learning using a large number of radiographic images including the irradiation field region and the direct radiation region.
• a discriminator that has been machine-learned to discriminate artifact regions may be used to discriminate artifact regions in the radiographic image, and the subject region may be identified by excluding the artifact regions from the radiographic image.
• the second radiation detector 6 is located on the side of the layered detector 4 farther from the radiation source 3, the amount of radiation irradiated is smaller than that of the first radiation detector 5. For this reason, when the imaging site is the chest, even if the dose in the lung field is sufficient, the dose may be insufficient in the mediastinum and below the diaphragm. When the dose is insufficient, the pixel values in the area where the dose is insufficient will be smaller than in an area where the dose is appropriate. Also, when the dose is insufficient, the granular noise will be greater in the area where the dose is insufficient than in an area where the dose is appropriate.
• the determination unit 23 determines whether the pixel values of at least a portion of the subject area GH2 of the second radiation image G2 are less than the reference pixel value, or whether the amount of granular noise in the subject area GH2 exceeds the reference amount.
• the determination unit 23 calculates the minimum pixel value of the reduced subject region GH2, and determines that there is an insufficient dose if the minimum pixel value is less than the reference value. Note that the region for which the insufficient dose is determined may be only the mediastinum and subdiaphragm regions in the subject region GH2 where the dose is small.
• the high frequency components are, for example, frequency components equal to or greater than half the Nyquist frequency of the original image (i.e., the second radiographic image G2), but are not limited to this.
• the high frequency components can be derived, for example, by reducing the second radiographic image G2 to half, enlarging the reduced image to the original size, and subtracting the enlarged image from the second radiographic image G2.
• the determination unit 23 determines that the dose is insufficient, it outputs the determination result of the dose deficiency to the dose setting unit 24 and the display control unit 26.
• the determination unit 23 determines that the dose is not insufficient, it identifies an area GH1 (not shown) corresponding to the subject area GH2 in the first radiation image G1. Then, the determination unit 23 determines whether or not at least a part of the pixel values in the area GH1 are saturated.
• the determination unit 23 determines that the dose is excessive, and outputs the determination result to the dose setting unit 24 and the display control unit 26.
• the area for which the dose is excessive may be only the lung field in the area GH1.
• the pixel values being saturated refers to a state in which the pixel values do not increase any more even if the radiation dose is increased.
• the pixel value of a saturated pixel (saturated pixel value) may be smaller than the maximum value that a radiological image can have.
• the judgment unit 23 may output information to the display control unit 26 indicating that the dose is appropriate.
• the dose setting unit 24 derives a dose setting value for setting the pixel value of the subject area to a target value.
• FIG. 6 shows profiles P1 and P2 of pixel values obtained in the first radiation detector 5 and the second radiation detector 6.
• a reference value A1 of pixel values is set in the profile P2 of pixel values obtained in the second radiation detector 6.
• the dose setting unit 24 derives a dose setting value such that the pixel value Bmin becomes the reference value A1.
• the reached dose R1 for the reference value A1 is derived by solving the reached dose in equation (1) with the pixel value as the reference value A1.
• the reached dose R2 for the minimum value Bmin is derived by solving the reached dose in equation (1) with the pixel value as the minimum value Bmin.
• the dose setting value is derived by multiplying the dose value X set at the time of shooting by (R1/R2).
• the saturated pixel value which is the pixel value of the saturated pixel in the first radiation image G1
• the minimum pixel value of the region in the second radiation image G2 corresponding to the region consisting of saturated pixels in the first radiation image G1 is set as G2min
• the maximum pixel value of the second radiation image G2 is set as G2max in the first profile P1 and the second profile P2 as shown in FIG. 9.
• the difference ⁇ B2 Bmax-G2min.
• the pixel value expected when the pixel corresponding to the pixel value G2max in the first radiation image G1 is not saturated is G2max+ ⁇ B2. If G2max+ ⁇ B2 does not exceed the saturated pixel value Bmax, the region GH1 corresponding to the subject region GH2 in the first radiation detector 5 will not be saturated.
• the dose setting unit 24 derives the dose setting value so that G2max + ⁇ B2 becomes Bmax. That is, by solving the reached dose in equation (1) with the pixel value set to G2max + ⁇ B2, the reached dose R3 for G2max + ⁇ B2 is derived. Also, by solving the reached dose in equation (1) with the pixel value set to Bmax, the reached dose R4 for Bmax is derived. Then, the dose setting value is derived by multiplying the dose value X set at the time of shooting by (R4/R3).
• the first radiographic image G1 and the second radiographic image G2 acquired by the first radiation detector 5 and the second radiation detector 6 have neither an excess nor a deficiency of dose in the subject region. Therefore, the pixel value of the subject region can be set as a target value, and as a result, the first and second radiographic images G1 and G2 can be acquired without an increase in noise and saturation of pixel values due to an insufficient dose.
• the dose setting unit 24 outputs the set dose setting value to the display control unit 26.
• the subtraction unit 25 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 (2) and (3), 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 (2) and (3) 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) (2)
• Gs (x, y) G2 (x, y) - ⁇ 2 ⁇ G1 (x, y) (3)
• the display control unit 26 displays the acquired radiation image on the display 14. That is, when the purpose of imaging is simple imaging, the display control unit 26 displays the simple radiation image G0 acquired by the first radiation detector 5 on the display 14. When the purpose of imaging is energy subtraction imaging, the display control unit 26 displays the bone image Gb and the soft tissue image Gs on the display 14. In this embodiment, the display control unit 26 notifies the user of the result of the dose determination by displaying it on the display 14.
• FIG. 10 shows the display screen when the dose is appropriate.
• the display screen 50 displays a bone image Gb and a soft tissue image Gs, as well as information 51 indicating that the dose at the time of imaging was appropriate.
• FIG. 11 shows the display screen when the dose is insufficient.
• the display screen 50 displays a bone image Gb and a soft tissue image Gs, as well as information 52 indicating that the dose was insufficient at the time of imaging and information 53 indicating the dose setting value for the next imaging derived by the dose setting unit 24.
• FIG. 12 shows the display screen in the case of an excessive dose.
• the display screen 50 displays a bone image Gb and a soft tissue image Gs, as well as information 54 indicating that an excessive dose occurred at the time of imaging and information 55 indicating the dose setting value for the next imaging derived by the dose setting unit 24.
• the display screen 50 displays a simple radiographic image G0 acquired by the simple radiography and information indicating whether the dose is excessive or insufficient.
• the excess or deficiency of the dose is notified by displaying it on the display screen 50, but this is not limited to this.
• the notification may be by voice, or by both voice and display.
• FIG. 13 is a flowchart showing the processing performed in this embodiment. Note that the processing when the purpose of shooting is energy subtraction shooting will be described here, and the processing when the purpose of shooting is simple shooting is the same as the processing described in Patent Document 1 above, so a detailed description will be omitted here.
• the imaging 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 imaging (step ST2).
• the imaging purpose is energy subtraction imaging
• the first and second radiation detectors 5 and 6 included in the layered structure detector 4 are identified as the radiation detectors to be used for imaging.
• the imaging control unit 21 drives the radiation source 3 under predetermined imaging conditions to perform radiography of the subject H and obtain a first radiographic image G1 and a second radiographic image G2 (step ST3).
• the subtraction unit 25 then performs energy subtraction processing using the first and second radiographic images G1 and G2 (step ST4). As a result, a bone image Gb and a soft tissue image Gs of the subject H are derived.
• the determination unit 23 identifies the subject region GH2 in the second radiographic image G2 acquired by the second radiation detector 6 (step ST5) and determines whether or not the radiation dose is insufficient in at least some of the pixels in the subject region GH2 (step ST6). If step ST6 is negative, the determination unit 23 determines whether or not the radiation dose is excessive due to saturation in at least some of the regions GH1 in the first radiographic image G1 acquired by the first radiation detector 5 (step ST7).
• the dose setting unit 24 derives a dose setting value for setting the pixel value of the subject region to a target value (step ST8).
• step ST9 the display control unit 26 displays the bone image Gb and the soft tissue image Gs, notifies the result of the dose determination (notification of the determination result: step ST9), and ends the process. Also, if step ST7 is negative, the display control unit 26 displays the bone image Gb and the soft tissue image Gs, notifies information that the dose was appropriate (step ST10), and ends the process.
• the excess or deficiency of radiation during radiography is determined based on at least one of the first and second radiographic images G1, G2 acquired by the first and second radiation detectors 5, 6 included in the layered structure detector 4, and the determination result is output. Therefore, by performing radiography again depending on the result of the excess or deficiency of the dose, a high-quality radiographic image can be obtained when performing radiography using the layered structure detector 4.
• the second radiation detector 6 is located on the far side of the layered detector 4 from the radiation source 3, and is therefore irradiated with a smaller amount of radiation than the first radiation detector 5. For this reason, when the imaging site is the chest, even if the dose in the lung field is sufficient, the dose may be insufficient in the mediastinum and below the diaphragm.
• the second radiation image G2 acquired by the second radiation detector 6 is used as a determination radiation image for determining whether the radiation is excessive or insufficient, to determine whether the dose is excessive or insufficient. For this reason, it is possible to accurately determine whether the second radiation detector 6 is insufficient.
• the system derives a set dose value and notifies the user. If the next image is taken using the notified set dose value, a high-quality radiological image with no dose excess or deficiency, i.e., little granular noise and no saturated pixel values, can be obtained.
• both the first radiographic image G1 and the second radiographic image G2 are used to determine whether the dose is excessive or insufficient, but this is not limited to the above. Only the first radiographic image G1 may be used to determine whether the dose is excessive or insufficient. Also, only the second radiographic image G2 may be used to determine whether the dose is insufficient or not.
• 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 imaging control unit 21, device control unit 22, judgment unit 23, dose setting unit 24, subtraction unit 25, and display control unit 26.
• 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), such as an FPGA (Field Programmable Gate Array), whose circuit configuration can be changed after manufacture, 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, as well as a programmable logic device (PLD), such as an FPGA (Field Programmable Gate Array), whose circuit configuration can be changed after manufacture, and a dedicated electrical circuit, such as an ASIC (Application Specific Integrated Circuit), which is a
• 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.
• Examples of configuring multiple processing units with a single processor include, first, a form in which one processor is configured with a combination of one or more CPUs and software, as typified by client and server computers, and this processor functions as multiple processing units. Secondly, a form in which a processor is used to realize the functions of the entire system, including multiple processing units, with a single IC (Integrated Circuit) chip, as typified by System On Chip (SoC). In this way, the various processing units are configured as a hardware structure using one or more of the various processors listed above.
• SoC System On Chip
• the hardware structure of these various processors can be an electrical circuit that combines circuit elements such as semiconductor elements.
• At least one processor At least one processor; The processor, performing radiography by irradiating a layered detector formed by stacking a plurality of radiation detectors with radiation emitted from a radiation source and transmitted through a subject to be photographed, thereby obtaining a plurality of radiographic images using the plurality of radiation detectors; determining whether the radiation was excessive or insufficient during the radiation imaging by using at least one of the plurality of radiation images as a determination radiation image; a radiation imaging control device that notifies the result of the excess or deficiency determination; (Additional Note 2) The processor determines whether the radiation is excessive or insufficient by using, as the determination radiographic image, a radiographic image acquired by one of the plurality of radiation detectors other than a radiation detector that is closest to the radiation source.
• the processor identifies a subject region of the determination radiographic image, The radiation imaging control device according to claim 2, wherein if a pixel value of at least a portion of the subject region is less than a reference pixel value, or if an amount of granular noise in at least a portion of the subject region exceeds a reference amount, it is determined that the radiation irradiated to the one radiation detector is insufficient in dose.
• the processor detects an artifact region included in the determination radiographic image, 4.
• the radiation imaging control device according to claim 3 wherein an area excluding the artifact area is specified as the subject area.
• the processor derives a reduced image of the determination radiographic image, 5.
• the radiation imaging control device further comprising: a determination as to whether or not pixel values of at least a portion of the subject region are less than a reference pixel value based on the reduced image.
• the processor determines whether or not an amount of granular noise in at least a part of the subject region exceeds a reference amount based on high frequency components of the determination-use radiographic image.
• Additional Note 7 7.
• the radiation imaging control device wherein, when it is determined that the radiation irradiated to the one radiation detector is not insufficient in dose, the processor determines whether the radiation is excessive or insufficient by using a radiation image acquired by a radiation detector among the plurality of radiation detectors that is closest to the radiation source as a further determination radiation image.
• the processor determines that the dose is excessive if pixel values of at least a portion of a region in the further determination radiographic image corresponding to the subject region are saturated.
• the processor determines that the radiation dose is excessive or insufficient, the processor derives a dose setting value for setting the pixel values of the object region to a target value; 9.
• the radiation imaging control device which notifies the dose setting value.
• (Additional Item 10) performing radiography in which radiation emitted from a radiation source and transmitted through a subject to be imaged is irradiated onto a layered detector formed by stacking a plurality of radiation detectors, thereby obtaining a plurality of radiographic images using the plurality of radiation detectors; determining whether the radiation was excessive or insufficient during the radiation imaging by using at least one of the plurality of radiation images as a determination radiation image; A radiation imaging control method for notifying the result of the excess or deficiency determination.
• (Additional Item 11) a step of performing radiography in which radiation emitted from a radiation source and transmitted through a subject to be imaged is irradiated onto a layered detector formed by stacking a plurality of radiation detectors, thereby obtaining a plurality of radiographic images using the plurality of radiation detectors; a step of determining whether the radiation was excessive or insufficient during the radiation imaging by using at least one radiation image of the plurality of radiation images as a determination radiation image; and notifying the result of the excess or deficiency determination.

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• 2023
  • 2023-11-29 JP JP2024574284A patent/JPWO2024161772A1/ja active Pending
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