JP4465915B2 - Radiographic imaging method and radiographic imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiographic image capturing method and a radiographic image capturing apparatus used for capturing a medical image.
[0002]
[Prior art]
Radiation images using X-rays and the like are often used as medical images for disease diagnosis and the like. In order to obtain this radiation image, the phosphor layer (phosphor screen) was irradiated with X-rays that passed through the subject, thereby generating visible light, and using this visible light in the same manner as in ordinary photographs, a silver salt was used. So-called radiographs developed by irradiating a film have been widely used.
[0003]
However, in recent years, a method for taking out an image directly from a phosphor layer without using a film coated with silver salt has been devised. In this method, the radiation transmitted through the subject is absorbed by the phosphor, and then the phosphor is excited by light or thermal energy, for example, so that the phosphor accumulates the radiation energy accumulated by the absorption. The image signal is obtained by photoelectrically converting this fluorescence. That is, this phosphor is used as a radiation image conversion plate.
[0004]
Specifically, for example, US Pat. No. 3,859,527 and JP-A-55-12144 disclose a radiation image conversion method using a stimulable phosphor and using visible light or infrared light as stimulating light. This method uses a radiation image conversion plate in which a photostimulable phosphor layer is formed on a support. The radiation transmitted through the subject is applied to the photostimulable phosphor layer of the radiation image conversion plate, and the object is covered. A latent image is formed by accumulating radiation energy corresponding to the radiation transmittance of each part of the specimen, and then the accumulated radiation energy is radiated by scanning the stimulable phosphor layer with stimulated excitation light. This is converted into light, and this optical signal is photoelectrically converted to obtain radiographic image data.
[0005]
The radiographic image capturing data obtained in this way is subjected to various image processing such as frequency processing and gradation processing, and is output as radiographic image capturing data to a silver salt film, CRT, etc. Filed in a filing device.
[0006]
Also, instead of the radiation image conversion plate as described above, an FPD (Flat Panel Detector) that is a radiation image detector that directly outputs an electrical signal corresponding to the dose of irradiated radiation, a phosphor and a lens (or taper) A thing using CCD etc. may be used.
[0007]
[Problems to be solved by the invention]
Based on the radiographic imaging data obtained by radiographic imaging as described above, the laser imager forms an image with a laser beam on a silver salt photosensitive material or the like and outputs it as a hard copy.
[0008]
In normal radiographic imaging, the radiation diffusing from the X-ray tube passes through the subject and reaches the detector. Therefore, when the distance between the subject and the detector is increased, the radiographic imaging data is larger than the subject. Become.
[0009]
In the past, enlarged radiation images were often output in the same size, but for the reason that it is easier to diagnose if they are the same size as the subject, the output device such as a laser imager is the same size as the subject. It is also necessary to output an image at the same magnification.
[0010]
On the other hand, because there are combinations of input devices and output devices with various sampling pitches, the pixel sampling pitch at the time of radiographic imaging device imaging is not necessarily an integer multiple of the pixel sampling pitch at the time of image formation of an output device such as a laser imager. It is not.
[0011]
Therefore, when trying to obtain an image formation output that is the same magnification as the subject with a laser imager, interpolation may be performed in a state other than simple interpolation (ratio other than integer multiples), and image deterioration is likely to occur. It was.
[0012]
The present invention has been made in view of the above problems. When an image formation output is obtained by a laser imager, image deterioration caused by interpolation performed in a state other than simple interpolation (ratio other than an integer multiple) is achieved. An object is to realize a radiographic imaging method and a radiographic imaging device that can be prevented.
[0013]
[Means for Solving the Problems]
  The present invention for solving the above problems is as follows..
[0029]
  (1) According to the first aspect of the present invention, the radiation that has passed through the subject is received by the radiation detector, the imaging data is output from the radiation image reading means, and the imaging data is subjected to image processing by the image processing means to obtain the radiation image data. A radiographic imaging method for generating and performing phase contrast imaging, wherein the radiation is determined by an output sampling pitch L of an image output unit that forms and outputs an image based on radiographic image data, and an input sampling pitch S of the radiographic image reading unit. Enlarged shooting rate β = S / L when using the image reading means to zoom in larger than the subjectC (where C is a constant that is a positive integer),Adjusting at least one of the position of the radiation source, the position of the subject, or the position of the radiation detector so as to satisfy the above condition, and forming and outputting an image at the same magnification as the subject during the phase contrast imagingIn order to perform image processing for reducing at a reduction ratio α (where α <1 and β = 1 / α).The radiation image capturing method is characterized in that the control is performed by a control means.
[0030]
  According to a second aspect of the present invention, there is provided a radiographic image capturing apparatus that performs phase contrast imaging of a radiographic image, wherein the radiographic image reading unit receives radiation transmitted through a subject by a radiation detector and outputs imaging data; Image processing means for generating radiographic image data by performing image processing on imaging data obtained by the image reading means, output sampling pitch L of the image output means for image formation output based on the radiographic image data, the radiographic image reading means With the input sampling pitch S, the magnification ratio β = S / L when the radiographic image reading means performs magnified imaging larger than the subject.C (where C is a constant that is a positive integer),Adjusting at least one of the position of the radiation source, the position of the subject, or the position of the radiation detector so as to satisfy the above, and outputting the image at the same magnification as the subject at the time of the phase contrast imagingIn order to perform image processing for reducing at a reduction ratio α (where α <1 and β = 1 / α).And a control means for performing the control.
[0031]
  In these inventions, when imaging data obtained from radiation that has passed through a subject is subjected to image processing to generate radiation image data and output to form an image, the output of the image output means that outputs an image based on the radiation image data Based on the sampling pitch L and the input sampling pitch S of the radiographic image reading means, β = 1 / α = S / L with respect to the enlargement photographing rate β when the radiographic image reading means performs enlargement photographing larger than the subject.C (where C is a constant that is a positive integer),To adjust the position of the radiation tube, subject, or radiation detector so as to satisfyIn order to perform image processing for reducing at a reduction ratio α (where α <1 and β = 1 / α).Control.
[0032]
  As a result, when the image formation output is obtained by the laser imager,It is possible to prevent image degradation due to interpolation performed in a state other than simple interpolation.
[0037]
DETAILED DESCRIPTION OF THE INVENTION
First, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of a radiographic image capturing apparatus 200 according to the first embodiment of the present invention. The radiographic image capturing apparatus 200 is connected to the network 100.
[0038]
In FIG. 1, 300 is an image server capable of storing a large number of radiation image data from the radiation image capturing apparatus 200 and the like, and 400 is a hard copy of radiation image data from the radiation image capturing apparatus 200 and the image server 300. It is a laser imager that outputs an image.
[0039]
In the first embodiment, a radiation image detector that directly outputs an electrical signal corresponding to the dose of irradiated radiation is used as an imaging panel.
In FIG. 1, in the controller 210, a control unit 211 for controlling the operation of each unit based on a control program, and an image processing unit for generating radiographic image data by performing image processing on imaging data from the radiographic image reader 240. 212, a display unit 213 for displaying radiation image data and various types of information is connected to the system bus.
[0040]
In the image processing unit 212, irradiation field recognition processing, region-of-interest setting, normalization processing and gradation processing of imaging data DT supplied from the radiation image reader 240, quality determination processing of these processing, frequency enhancement processing, dynamic A range compression process, a reduction process, and the like are performed.
[0041]
As shown in FIG. 1, in the radiographic imaging apparatus 200, the radiation generator 230 is controlled by a controller 210, and the radiation emitted from the X-ray tube 231 in the radiation generator 230 passes through the subject 5 and is a radiographic image. Irradiation is performed on the imaging panel 241 mounted on the X-ray tube side of the reader 240. In this case, since the X-ray tube 231 is diffusely irradiated and passes through the subject 5 and reaches the imaging panel 241, the enlarged imaging with the enlarged imaging rate β is executed when the distance between the subject and the detector is increased. This magnified imaging rate β is determined by the positions of the radiation generator 230, the subject 5, and the imaging panel 241.
[0042]
FIG. 2 is a configuration diagram showing the configuration of the imaging panel 241 used in the radiation image reader of FIG.
Here, the configuration of the imaging panel 241 provided in the radiation image reader 240 will be described with reference to FIG. The imaging panel 241 has a substrate having a thickness sufficient to obtain a predetermined rigidity, and a detection element 2413- (1,1) that outputs an electrical signal on the substrate in accordance with the dose of irradiated radiation. ) To 2413- (m, n) are two-dimensionally arranged in a matrix. Further, the scanning lines 2411-1 to 2411 -m and the signal lines 2412-1 to 2412 -n are arranged so as to be orthogonal to each other, for example.
[0043]
The scanning lines 2411-1 to 2411 -m of the imaging panel 241 are connected to the scanning driving unit 2414. When the readout signal RS is supplied from the scanning drive unit 2414 to one of the scanning lines 2411-1 to 2411 -m, the scanning line 2411 -p (p is any value from 1 to m). -p outputs electrical signals SV-1 to SV-n corresponding to the dose of radiation emitted from the detection element connected to -p, and outputs them to the imaging data generation circuit 2415 via signal lines 2412-1 to 2412-n. Supplied.
[0044]
The detection element 2413 may be any element that outputs an electrical signal corresponding to the dose of irradiated radiation. For example, when a detection element is formed using a photoconductive layer in which electron-hole pairs are generated and change in resistance when irradiated with radiation, the detection element is in accordance with the amount of radiation generated in the photoconductive layer. An amount of charge is stored in the charge storage capacitor, and the charge stored in the charge storage capacitor is supplied to the imaging data generation circuit 2415 as an electrical signal. It is desirable that the photoconductive layer has a high dark resistance value, such as amorphous selenium, lead oxide, cadmium sulfide, mercuric iodide, or an organic material exhibiting photoconductivity (photoconductivity to which an X-ray absorption compound is added. In particular, amorphous selenium is desirable.
[0045]
Further, when the detection element 2413 is formed by using, for example, a scintillator that generates fluorescence when irradiated with radiation, an electrical signal based on the fluorescence intensity generated by the scintillator is generated by a photodiode to generate imaging data. It may be supplied to the circuit 2415.
[0046]
The photographing data generation circuit 2415 sequentially selects the electrical signal SV supplied based on an output control signal SC from a reading circuit 242 described later, and converts it into digital photographing data DT. The photographing data DT is supplied to the reading circuit 242.
[0047]
The reading circuit 242 is connected to the controller 210, and generates the scanning control signal RC and the output control signal SC based on the control signal CTD supplied from the controller 210. This scanning control signal RC is supplied to the scanning drive unit 2414, and the reading signal RS is supplied to the scanning lines 241-1 to 2411-m based on the scanning control signal RC.
[0048]
Further, the output control signal SC is supplied to the photographing data generation circuit 2415. For example, when the imaging panel 41 includes (m × n) detection elements 2413 as described above by the scanning control signal RC and the output control signal SC from the reading circuit 242, the detection element 2413- ( 1,1) to 2413- (m, n), the data DP (1,1) to DP (m, n) is data DP (1,1), DP (1,1). 2)... DP (1, n), DP (2,1),..., DP (m, n) are generated in this order, and this shooting data DT is generated from the shooting data generation circuit 2415. This is supplied to the reading circuit 242. In addition, the reading circuit 242 also performs processing for sending the photographing data DT to the controller 210.
[0049]
Imaging data DT obtained by the radiation image reader 240 is supplied to the controller 210 via the reading circuit 242. If the image data obtained by logarithmic conversion processing is supplied when the image data obtained by the radiation image reader 240 is supplied to the controller 210, the processing of the radiation image data in the controller 210 can be simplified.
[0050]
Note that, by the control of the control unit 211, the scan driving circuit 2414 and the imaging data generation circuit 2415 add the detection results of the plurality of adjacent detection elements 2413, thereby changing the input sampling pitch S in the reading of the radiation image. It becomes possible.
[0051]
Further, when the photostimulable phosphor plate 241B is used for reading as shown in FIG. 3, by changing the beam diameter of the excitation light, the scanning density, and the data reading time interval according to the instruction of the control unit 211, the input for reading is performed. It is possible to change the sampling pitch S as well.
[0052]
FIG. 3 shows a mechanical part of a configuration example of a radiation image reader 240 using a stimulable phosphor plate. First, the radiation image reader 240 will be described. The photostimulable phosphor plate 241B is fixed to the left side wall and is used repeatedly. The reading unit 243 moves along the guide shaft 244B by scanning the ball screw 244A by the sub-scanning motor 244M configured by a stepping motor or the like, and scans the scanning line (light beam) 245 in the sub-scanning direction.
[0053]
Scanning in the main scanning direction is performed by the polygon scanning mechanism 243A. Polygon scanning mechanism 243A includes a polygon and a mechanism for rotating the polygon. The operation of the sub-scanning motor 244M is controlled by the sub-scanning motor control mechanism 244C. The fluorescence is condensed by a condenser 243B and converted into an electric signal by a photomultiplier 243C.
[0054]
LD1 is a laser light source, PD1 is a photo sensor, and constitutes an origin position detection sensor. This origin position detection sensor detects the origin position of the reading unit 243 in the sub-scanning direction. The output of the photosensor PD1 is input to the sub-scanning motor control mechanism 244C, and the sub-scanning motor control mechanism 244C controls the stop position of the reading unit 243.
[0055]
In this example, the reading unit 243 is moved by driving the ball screw 244A, but the stimulable phosphor plate 241B may be moved in the sub-scanning direction.
FIG. 4 is a perspective view schematically showing a schematic configuration of a laser imager 400 as an image output device constituted by a scanning laser exposure apparatus. Here, although a laser imager is used as an example of an image output device, various other output devices can be used.
[0056]
Here, an LD (laser diode) that has received the light emission drive signal generated according to the radiation image data emits light according to the signal value of the pixel, and the laser beam from this LD 410 is scanned in the main scanning direction by the polygon mirror 420. Then, it is exposed to a recording medium 430 such as a silver salt photosensitive material. Note that scanning in the sub-scanning direction is performed by moving either the optical system of the LD 410 and the polygon mirror 420 or the recording medium 430, and an image is formed on the recording medium 430 according to the radiation image data.
[0057]
That is, in the laser imager 400 of this scanning laser exposure apparatus, the laser beam intensity is modulated by the image data, and the conventional silver halide photographic light-sensitive material or the heat phenomenon silver halide photographic light-sensitive material is exposed and then subjected to appropriate development processing. By doing so, a hard copy of the radiographic image can be obtained.
[0058]
In this laser imager 400, it is desirable that the thickness of the laser beam and the density of main scanning and sub-scanning are variable, and the image forming density is variable. Alternatively, it is also desirable that a plurality of laser imagers 400 having different image formation densities be arranged. That is, it is desirable that the output sampling pitch L of the image output means for forming and outputting an image based on the radiation image data can be adjusted.
[0059]
Here, the overall operation of the first embodiment will be described.
In this embodiment, the imaging panel 241 receives the radiation irradiated from the X-ray tube 231 and transmitted through the subject 5, and outputs an electrical signal corresponding to the radiation dose irradiated. Then, the reading circuit 242 that has received the electrical signal from the imaging panel 241 generates shooting data.
[0060]
Further, the image processing unit 212 that receives the imaging data from the reading circuit 242 performs irradiation field recognition processing, region-of-interest setting, normalization processing, and gradation processing for the imaging data supplied from the radiation image reader 240, and The quality determination processing, frequency enhancement processing, dynamic range compression processing, reduction processing, and the like of these processes are performed to generate radiation image data.
[0061]
The radiation image data is supplied to the image server 300 and stored, or supplied to the laser imager 400 to form an image and output as a hard copy.
[0062]
Here, when the radiation image data is processed by the image processing unit 212 in the controller 210 and image formation is output by the imager 400, the following controls (1-1) to (1-3) are performed. To do.
[0063]
Here, the input sampling pitch in the imaging panel 241 is S, the output sampling pitch of the imager 400 is L, and the reduction rate of the radiation image data (ratio of the size of the output image to the image incident on the detector) is α (α < 1) Let C be a constant that is a positive integer.
[0064]
(1-1) Control of input sampling pitch S:
Here, the control unit 211 performs control for adjusting the input sampling pitch S so as to satisfy S = (L · C) / α. In this case, under the control of the control unit 211, the scanning drive circuit 2414 and the imaging data generation circuit 2415 add the detection results of the plurality of adjacent detection elements 2413, thereby changing the input sampling pitch S in reading the radiation image. Is possible. For example, in FIG. 2, the input sampling pitch S can be doubled by outputting imaging data for each 2 × 2 detection elements instead of outputting imaging data for each detection element. That is, the input sampling pitch S can be increased by a factor of n by outputting shooting data for each n × n detection element.
[0065]
Further, when the photostimulable phosphor plate 241B is used for reading as shown in FIG. 3, by changing the beam diameter or scanning density of the excitation light and changing the data reading time interval according to the instruction of the control unit 211, Similarly, it is possible to change the input sampling pitch S in reading.
[0066]
As a result, the input sampling pitch S may deviate from the minimum sampling pitch of the imaging panel 241. However, when an image forming output is obtained by a laser imager, simple interpolation is performed with a positive integer C. It is possible to prevent image degradation due to interpolation performed in a state other than interpolation.
[0067]
(1-2) Control of reduction rate α:
Here, the control unit 211 performs control for adjusting (determining α) the reduction rate α (α <1) so as to satisfy α = (L · C) / S. In this case, α is determined so as to satisfy the above expression under the control of the control unit 211, and then the reduction processing in the image processing unit 212 is executed based on α. If a plurality of constants C can be selected, it is desirable to select C to be a large numerical value from the viewpoint of outputting the signal as close to the subject as possible.
[0068]
As a result, there is a possibility that the reduction ratio α deviates from a predetermined value (for example, α for image formation output at the same magnification). However, when an image formation output is obtained by a laser imager, a simple integer C is used. Interpolation is performed, and it is possible to prevent image degradation due to interpolation performed in a state other than simple interpolation.
[0069]
In addition to executing the reduction process in the image processing unit 212 based on α determined by the control unit 211, a similar reduction process based on α may be executed on the imager 400 side.
[0070]
(1-3) Control of output sampling pitch L:
Here, the control unit 211 performs control for adjusting the output sampling pitch L so as to satisfy L = (α · S) / C. In this case, the output sampling pitch L in the imager 400 can be changed by giving a command for changing the output sampling pitch L from the control unit 211 to the imager 400.
[0071]
For example, in the laser imager 400 of FIG. 4, when the thickness of the laser beam and the density of main scanning and sub-scanning are variable, and the image forming density is variable, the control unit 211 in the controller 210 The image formation density is changed by the output sampling pitch L change command.
[0072]
When a plurality of laser imagers 400 having different image formation densities are arranged in the network 100, a suitable imager having the output sampling pitch L obtained by the above formula is selected as a control unit 211 in the controller 210. Then, the radiographic image data is transmitted to the selected imager to form an image.
[0073]
As a result, there is a possibility that the output sampling pitch L becomes larger than the minimum sampling pitch of the imager. However, when an image forming output is obtained by a laser imager, simple interpolation is performed with a positive integer C, and not simple interpolation. Thus, it is possible to prevent image degradation due to interpolation.
[0074]
(2-1) Control on the magnification ratio β:
FIG. 5 is a block diagram showing the configuration of the radiographic image capturing apparatus 200 according to the second embodiment of the present invention. The same components as those in the radiation image capturing apparatus 200 of the first embodiment shown in FIG.
[0075]
The radiographic image capturing apparatus 200 of FIG. 5 is configured to be able to adjust the magnification ratio β. That is, as shown in FIG. 5, the radiation diffused from the X-ray tube 231 passes through the subject 5 and reaches the imaging panel 241. Therefore, when the distance between the subject and the detector is increased, the magnification ratio β is increased. Shooting is executed.
[0076]
The magnification ratio β is β = (a + b) / a where the distance from the X-ray tube 231 irradiation position to the subject 5 center is a and the distance from the subject 5 center to the imaging panel 241 is b. It is determined by the respective positions of the radiation generator 230, the subject 5, and the imaging panel 241.
[0077]
For this reason, in the radiographic imaging apparatus 200 of the second embodiment, the position of the radiation generator 230 and the moving mechanism 233 for changing the distance a and the position of the imaging panel 241 are changed. And a moving mechanism 243 for changing the distance b. Then, under the control of the control unit 211 in the controller 210, the moving mechanism 233 moves the position of the X-ray tube 231 and the moving mechanism 243 moves the position of the imaging panel 241.
[0078]
In this case as well, the input sampling pitch in the imaging panel 241 is S, the output sampling pitch of the imager 400 is L, the reduction rate of the radiation image data is α (α <1), a positive integer constant is C, and is larger than the subject. It is assumed that the enlargement shooting rate β at the time of enlargement shooting in the state.
[0079]
In this case, at least one of the position of the radiation tube, the position of the subject, or the position of the radiation detector is adjusted so as to satisfy β = 1 / α = S / (L · C), and the image is the same size as the subject. The control unit 211 performs control for forming and outputting.
[0080]
Then, after the image processor 212 reduces the image by the inverse α of β, the imager 400 forms and outputs an image, thereby obtaining an equal-magnification hard copy. For example, if β = 2, an equal hard copy can be obtained by setting α to 0.5.
[0081]
In this case, the control unit 211 executes the following control (1), (2), or (3).
(1) Without changing the standing position of the subject 5, either one or both of the position of the X-ray tube 231 by the moving mechanism 233 and the position of the imaging panel 241 by the moving mechanism 243 are moved. Therefore, the control unit 211 gives a command for movement (movement on / off, movement direction, movement amount) to the movement mechanism 233 or the movement mechanism 243.
(2) The position of the subject 5 is moved without changing the positions of the X-ray tube 231 and the imaging panel 241. Therefore, the control unit 211 displays the standing position of the subject 5 on the floor using a laser beam from a standing position display unit (not shown).
(3) The above (1) and (2) above are combined, and all the positions of the X-ray tube 231, the imaging panel 241, and the subject 5 are changed and finely controlled so as to obtain the optimum magnified imaging rate β. To do.
[0082]
As a result, there is a possibility that the magnified shooting rate β may deviate from a desired value. However, when an image formation output is obtained by a laser imager, simple interpolation is performed with a positive integer C, and interpolation is performed in a state that is not simple interpolation. It is possible to prevent the image from being deteriorated by being performed.
[0083]
(3) Phase contrast photography:
According to the control that matches each of the expressions described above, when an image forming output is obtained by a laser imager, simple interpolation is performed with a positive integer C, so that deterioration of the image can be prevented. Suitable for outputting sharp hard copies of contrast radiation images.
[0084]
That is, the imaging data output from the radiation image reading means applied in this embodiment is phase contrast radiation image data that is digital data. The digital data may be imaging data obtained directly as digital data as described above, or may be obtained by digitizing data obtained as analog image data.
[0085]
<Description of the principle of phase contrast radiographic images>
This phase contrast radiation image is taken with an apparatus disclosed in Japanese Patent Application Laid-Open No. 2001-91479, an apparatus described in Japanese Patent Application Laid-Open No. 2001-92055, an apparatus described in Japanese Patent Application No. 2000-44381, an apparatus described in Japanese Patent Application No. 2000-53562, and the like. Images obtained by photographing methods such as the method described in Japanese Patent Application Laid-Open No. 2001-91479, the method described in Japanese Patent Application Laid-Open No. 2001-92055, and the method described in Japanese Patent Application No. 2000-44381. .
[0086]
(3-1) An apparatus described in Japanese Patent Application Laid-Open No. 2001-91479 has an X-ray tube having a focal size (D μm) of 30 μm or more, a fixing unit that fixes a subject position, and an X-ray image transmitted through the subject. And the fixing means detects the distance R1 (m) from the X-ray tube to the subject fixed by the fixing means within the range of the formula R1 ≧ (D-7) / 200 (m) In addition, the X-ray imaging apparatus is configured such that the distance R2 from the subject fixed by the fixing means to the X-ray detector can be set to 0.15 m or more.
[0087]
Further, the method described in Japanese Patent Application Laid-Open No. 2001-91479 detects an X-ray image irradiated from an X-ray tube and transmitted through a subject with an X-ray detector, and reduces sharpness that is deteriorated by a penumbra. An X-ray image capturing method enhanced by image edge enhancement by the above, and an X-ray image capturing method using an X-ray tube having a focal spot size (D μm) of 30 μm or more, the distance R1 from the X-ray tube to the subject This is an X-ray imaging method in which (m) is set within the range of the equation R1 ≧ (D−7) / 200 (m), and the distance R2 from the subject to the X-ray detector is set to 0.15 m or more.
[0088]
(3-2) For the apparatus and method described in Japanese Patent Laid-Open No. 2001-91479, the distance R1 is 10> R1 ≧ (D-7) / 200 (m), and further 0.7 ≦ R1 ≦ 5 (m), the focus size of the X-ray tube is 30 μm or more and 1000 μm or less, the focus size of the X-ray tube is 50 μm or more and 500 μm or less, and the X-rays irradiated to the subject In a more preferable aspect, the energy of the emission line spectrum is 10 keV or more and 60 keV or less, the anode of the X-ray tube has molybdenum or rhodium, and the pixel size of the X-ray detector is 1 μm or more and 200 μm or less. is there.
[0089]
(3-3) An apparatus described in Japanese Patent Application No. 2000-44381 includes an X-ray tube that emits diverging X-rays, a subject holder that fixes the subject to the X-ray tube, and an X that passes through the subject. X-ray tube having an X-ray image detector for detecting a line image, where B (μm) is a blur width due to a penumbra of the X-ray image and E (μm) is an edge enhancement width due to X-ray diffraction contrast This is an X-ray imaging apparatus in which an object holder and an X-ray image detector can be installed so that 9E ≧ B when X-ray enlarged imaging is performed by transmitting more irradiated X-rays to the object.
[0090]
The method described in Japanese Patent Application No. 2000-44381 uses an X-ray tube that emits divergent X-rays, transmits X-rays radiated from the X-ray tube to the subject, and performs X-ray enlargement imaging. X-ray image shooting in which 9E ≧ B is satisfied, where B (μm) is the blur width due to the penumbra of the X-ray image obtained by X-ray enlargement imaging, and E (μm) is the edge enhancement width due to X-ray refraction contrast Is the method.
[0091]
Regarding the apparatus and method described in Japanese Patent Application No. 2000-44381, the distance R1 between the X-ray tube and the subject is separated by 0.5 m or more, the distance R2 between the subject and the X-ray image detector is separated by 1 m or more, Furthermore, the R1 + R2 is 5 m or less, the X-ray magnified imaging is 1.0 to 10 times, the focal size of the X-ray tube is 10 μm or more and 1000 μm or less, and the focal size of the X-ray tube Is 30 μm or more and 300 μm or less, the set tube voltage of X-rays irradiated to the subject is 50 to 150 kVp, the X-ray tube is a tungsten rotating anode X-ray tube, and the pixel of the X-ray detector It is a more preferable embodiment that the size is 1 μm or more and 200 μm or less.
[0092]
The edge emphasis width E can be expressed by the following three expressions, for example. Here, R1: X-ray source-subject distance (m), R2: Subject-X-ray image detector (m), λ: wavelength of maximum X-ray dose (10^-Tenm), A: diameter (mm) of the circle of the cross section when the subject is a cylinder, δ: difference in refractive index between the object and air.
[0093]
E = 39 × R2 (1 + 0.045 / R1) × λ²× √A,
E = 27 × (1 + R2 / R1)^1/3× (λ²× R2 × √A)^2/3,
E = 2.3 × (1 + R2 / R1)^1/3× (R2 × δ × √A)^2/3,
It becomes.
[0094]
(3-4) An apparatus described in Japanese Patent Application No. 11-266605 includes an object support device and a film cassette holder that can be moved and temporarily fixed on a support member, and a cooling X-ray tube; The distance between the film cassette holder and the screen / film system can be 70 cm or more, and the distance between the object of the object support device and the screen / film system of the film cassette holder can be 20 cm or more. , An X-ray image capturing apparatus for capturing an X-ray refraction contrast image.
[0095]
In addition, the method described in Japanese Patent Application No. 11-266605 includes a subject support device and a film cassette holder that are movable on a support member and can be temporarily fixed, and hold a cooling X-ray tube and a film cassette. X-ray imaging that captures X-ray refraction contrast images with a distance of 70 cm or more between the screen and film system of the tool, and a distance of 20 cm or more between the subject of the object support device and the screen and film system of the film cassette holder Is the method.
[0096]
(3-5) An apparatus described in Japanese Patent Application No. 2000-53562 includes a small-focus radiation source that irradiates a subject with radiation, a holding member that holds the subject, and reading means that reads radiation image information based on the radiation that has passed through the subject. And a distance changing means for changing a first distance between the small focus radiation source and the holding member or a second distance between the holding member and the reading means, and a control for controlling the radiation conditions of the small focus radiation source And a control means for controlling the radiation condition of the small focus radiation source according to at least distance information relating to the first distance or the second distance, and a radiation image capturing apparatus for irradiating the subject with radiation. A focus radiation source, a holding member for holding a subject, a reading means for reading radiation image information based on radiation transmitted through the subject, and an image display means for displaying radiation image information. Or an image output means for outputting radiation image information, and a radiation means having a control means for changing the image enlargement ratio at the time of radiographic imaging and displaying the radiation image information by the image display means or outputting by the image output means An image capturing device.
[0097]
Absorption contrast radiography refers to imaging a subject in close contact with a detector and optionally via a grid. Absorption contrast radiographic images are images obtained by absorption contrast radiography.
[0098]
A phase contrast radiographic image capturing apparatus capable of obtaining a phase contrast radiographic image is an apparatus capable of capturing a phase contrast radiographic image as well as absorption contrast radiographic image capturing (general image capturing normally performed).
[0099]
(3-6) In addition, the same image processing is performed on the image obtained by phase contrast imaging. The phase-contrast image has better granularity than an image obtained by a general grid-based image capture method (although it is a reduced output at the same magnification). It is preferable to perform a process (to add contrast). Further, it is preferable that the frequency processing and the dynamic range compression processing are also subjected to strong processing.
[0100]
(3-7) Note that the phase contrast imaging methods described in this application and applications such as Japanese Patent Application No. 2001-91479 and Japanese Patent Application No. 2000-44381 do not require high spatial coherence in the X-ray source. The degree of spatial coherence can be expressed by degree of coherence | μ |. | μ | takes a value from 0 to 1, with 0 being completely incoherent and 1 being completely coherent. From equation (28) of Tokai University Press “Principle of Optical III” P766,
| μ | = 2J1 (v) / v.
[0101]
Here, J1 is the first type first-order Bessel function, parameter v is the center wavelength of the X-ray source λ, the focal diameter is ρ, the distance between the X-ray source and the object is R, and the size of the target object is As d, v = 2πρd / (λR).
[0102]
As a typical condition of this shooting method, λ = 0.7 × 10^-TenWhen m, ρ = 100 μm, R = 1 m, and d = 100 μm, v≈900. J1 (v) is a function that takes the first zero point at v = 3.83, so | v | ≈0 when v = 900. The argument of degree of coherence is meaningful only up to v <3.83 up to the first zero, so that even if the conditions change somewhat, | μ | ≈0 remains the same. Therefore, this imaging method is performed by an incoherent system, and is different from a method that requires high spatial coherence using X-ray interference or diffraction.
[0103]
(4) Other embodiment examples:
In the description of the above embodiment, when the input sampling pitch S of the imaging panel 241 is large, or when S · α multiplied by the reduction ratio α is large, the pixel is visually observed in a hard copy state. It is desirable to output a hard copy from the imager 400 after performing a smoothing process in the image processing unit 212 so that the image becomes inconspicuous.
[0104]
When α is adjusted in the above (1-2), since the hard copy from the imager 400 is not the same size, the exact size of the original subject 5 may not be known. Therefore, it is desirable to output a hard copy in a state where a scale or an enlarged imaging rate β and a reduction rate α are put in a portion around the subject 5.
[0105]
The focal diameter of the X-ray tube 231 is desirably increased to 30 μm or more in order to obtain a high output.
Further, in order to eliminate out-of-focus blur, it is desirable to reduce it to 1200 μm or less, preferably 600 μm or less. In the case of magnified shooting, it is desirable to reduce it to 300 μm or less in order to eliminate out-of-focus blur. Furthermore, in order to obtain a phase-contrast radiographic image by phase contrast imaging, it is preferable to make it smaller than 200 μm, more preferably smaller than 100 μm.
[0106]
【The invention's effect】
As described in detail above, according to the radiographic image capturing method and radiographic image capturing apparatus of the present invention, when image formation output is obtained by a laser imager, interpolation is performed in a state other than simple interpolation (ratio other than integer multiple). It is possible to prevent the deterioration of the image due to being broken.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a system configuration of a radiographic imaging apparatus according to a first embodiment of the present invention.
FIG. 2 is a configuration diagram showing a configuration of a radiation image reader according to a first embodiment of the present invention.
FIG. 3 is a configuration diagram showing another configuration of the radiation image reader according to the first exemplary embodiment of the present invention.
FIG. 4 is a perspective view showing a schematic configuration of an imager used in the first embodiment of the present invention.
FIG. 5 is a configuration diagram showing a system configuration of a radiographic imaging device according to a second exemplary embodiment of the present invention.
[Explanation of symbols]
100 network
210 controller
211 Control unit
212 Image processing unit
213 Display
230 Radiation generator
231 X-ray tube
240 Radiation image reader
241 Imaging panel
242 Reading circuit
300 Image server
400 imager
500 Image output device

Claims (2)

Radiation imaging that receives radiation transmitted through an object by a radiation detector, outputs imaging data from a radiation image reading means, performs image processing on the imaging data by an image processing means to generate radiation image data, and performs phase contrast imaging A method,
Based on the output sampling pitch L of the image output means for forming and outputting an image based on the radiographic image data and the input sampling pitch S of the radiographic image reading means, the magnified photographing at the time of the magnified photographing in a state larger than the subject by the radiation image reading means Adjusting at least one of the position of the radiation source, the position of the subject, or the position of the radiation detector so as to satisfy the ratio β = S / L · C (where C is a constant that is a positive integer) , Control means for performing image processing for reduction at a reduction ratio α (where α <1 and β = 1 / α) in order to form and output an image at the same magnification as the subject at the time of phase contrast imaging. Do in,
The radiographic imaging method characterized by the above-mentioned. A radiographic imaging apparatus that performs phase contrast imaging of radiographic images,
Radiation image reading means for receiving radiation transmitted through the subject by a radiation detector and outputting imaging data;
Image processing means for generating radiation image data by performing image processing on imaging data obtained by the radiation image reading means;
Based on the output sampling pitch L of the image output means for forming and outputting an image based on the radiographic image data and the input sampling pitch S of the radiographic image reading means, the magnified photographing at the time of the magnified photographing in a state larger than the subject by the radiation image reading means Adjusting at least one of the position of the radiation source, the position of the subject, or the position of the radiation detector so as to satisfy the ratio β = S / L · C (where C is a positive integer). Control means for performing control for performing image processing for reduction at a reduction ratio α (where α <1 and β = 1 / α) in order to form and output an image at the same magnification as that of a subject at the time of contrast photographing; ,
A radiographic imaging apparatus comprising:

Images