JP7392478B2 - Magnification calculation device, long-length photographing system, program, and magnification calculation method - Google Patents

Description

The present invention relates to an enlargement factor calculation device, a long photographing system, a program, and an enlargement factor calculation method.

A radiation detector and a radiation source (tube) are moved in the direction of the body axis, which is the extension of the body axis of the subject, and are repeatedly photographed to generate multiple radiographic images. There is an imaging method called elongated imaging (parallel method) that generates a radiation image (elongated image) of an area larger than the size of one radiation detector by connecting images.
The long image obtained by this long-length imaging is used in diagnosis in the field of orthopedic surgery, for example, to measure the size of a region of interest (for example, a bone) or the distance between the regions of interest.

By the way, when radiographic imaging including long-length imaging is performed, the imaging surface of the radiation detector is farther away from the radiation source than the patient's region of interest. Furthermore, the radiation (X-rays) used for imaging is generally synchrotron radiation. For this reason, the region of interest in the radiographic image will appear more enlarged than the actual region of interest.
In order to accurately measure the size of a region of interest or the distance between regions of interest from a radiographic image, it is necessary to know the magnification of the radiographic image relative to the subject. Therefore, the enlargement magnification has conventionally been calculated using the following method.
- With the distance SID between the radiation source and the imaging plane as a known value, the distance SOD between the radiation source and the region of interest of the subject is measured, and the magnification factor (SID/SOD) is calculated.
・Indicators (scale, etc.) are placed on the surface of the screen that is in contact with the subject, and the magnification factor is calculated based on the indicators shown in the radiographic image.
However, it is difficult to accurately measure SOD using such conventional magnification factor calculation methods. Furthermore, the magnification cannot be made accurate unless the position of the region of interest and the position of the index match, but it is also difficult to make them match.

Therefore, in recent years, a technique has been proposed that calculates the magnification factor from the amount of movement of the region of interest.
For example, Patent Document 1 describes an X-ray fluoroscopic image of a sample obtained in a first state and a second state in which the stage is moved by a known amount in the direction of the X-ray optical axis from the first state. The distance SOD between the X-ray source and the sample in the first state is calculated from each dimension information of the X-ray fluoroscopic image and the known movement amount of the stage, and the dimensions of the X-ray fluoroscopic image obtained in the first state are calculated. information, dimension information of an X-ray fluoroscopic image of the sample obtained in a third state in which the X-ray detector is moved by a known amount in the direction of the X-ray optical axis from the first state, and known dimensions of the X-ray detector. This document describes an X-ray imaging apparatus that calculates the distance SID between the X-ray source and the X-ray detector in the first state from the amount of movement, and calculates the fluoroscopic magnification in the first state from the SID and SOD. .
Furthermore, in Patent Document 2, a region of interest on an X-ray fluoroscopic image displayed on a display is specified, the amount of movement of the designated region on the screen of the display is calculated, and the sample table is Using the amount of movement of the sample table when it is moved in a direction perpendicular to the line connecting the generator and the X-ray detector, and the amount of movement on the screen of interest at that time, the vicinity of the region of interest is determined. This document describes an X-ray fluoroscope that calculates the imaging magnification of .

Japanese Patent Application Publication No. 2007-064906 Japanese Patent Application Publication No. 2002-243663

However, in the conventional techniques described in Patent Documents 1 and 2 mentioned above, it is necessary to move the sample to obtain a perspective image for calculating the magnification factor. For this reason, it becomes necessary to provide the apparatus with a mechanism for moving the sample, and the work during imaging increases by the amount of movement of the sample.
Particularly, when the sample is a person (subject), the subject must be moved, so there is a risk that the subject will collide with or be caught in the apparatus.
Furthermore, with the conventional technology, it was not possible to automatically determine which part of interest was the target part (the user had to specify it).

The present invention has been made in view of the above-mentioned problems, and it is possible to accurately calculate the magnification of the target area of a subject in a radiographic image relative to the actual object without complicating the device or increasing the number of steps during imaging. The purpose is to do so.

In order to solve the above problems, an enlargement factor calculation device according to the present invention includes:
an acquisition means for acquiring a plurality of radiographic images each having different geometric imaging conditions and each having an image overlap region in which a region of interest of a subject is commonly captured;
Calculation means for calculating an enlargement magnification of the radiographic image of the target region of the subject relative to the actual object , based on the plurality of image overlapping regions in the plurality of radiographic images acquired by the acquisition means;
and output means for performing a predetermined output based on the magnification factor calculated by the calculation means.

Moreover, the long photographing system according to the present invention includes:
a radiation source;
an aperture that changes the width of an irradiation field, which is a range in which radiation emitted from the radiation source is irradiated onto an imaging surface;
a first movement mechanism that moves the radiation source and the aperture in a body axis direction that is an extension direction of the subject's body axis;
a radiation detector that generates a radiation image according to radiation received on the imaging surface;
a second movement mechanism that moves the radiation detector in the body axis direction;
A long image generating means that generates a long image by overlapping and connecting image overlapping regions generated by repeatedly photographing the subject while the radiation source and the radiation detector move in the body axis direction. and,
Calculating means for calculating an enlargement magnification of the radiographic image of the target region of the subject relative to the actual object based on the plurality of image overlapping regions in the plurality of radiographic images generated by the radiation detector;
and output means for performing a predetermined output based on the magnification factor calculated by the calculation means.

Further, the program according to the present invention is
to the computer,
an acquisition process of acquiring a plurality of radiographic images each having different geometric imaging conditions and each having an image overlap region in which a region of interest of a subject is commonly captured;
a calculation process of calculating an enlargement magnification of the radiographic image of the target region of the subject relative to the actual object , based on the plurality of image overlapping regions in the plurality of radiographic images acquired in the acquisition process;
An output process of performing a predetermined output based on the magnification factor calculated in the calculation process is executed.

Furthermore, the magnification factor calculation method according to the present invention is as follows:
an imaging step of generating a plurality of radiographic images each having different geometric imaging conditions and each having an image overlap region in which a region of interest of a subject is commonly captured;
a calculation step of calculating an enlargement magnification of the radiographic image of the target region of the subject relative to the actual object based on the plurality of image overlapping regions in the plurality of radiographic images generated in the imaging step;
and an output step of performing a predetermined output based on the magnification factor calculated in the calculation step.

According to the present invention, it is possible to accurately calculate the magnification of a target region of a subject in a radiation image relative to the actual object without complicating the device or increasing the number of steps during imaging.

FIG. 2 is a side view of the elongated photographing system according to the first and second embodiments. FIG. 7 is a side view of another elongated photographing system according to the first and second embodiments. FIG. 2 is a block diagram showing an enlargement factor calculation device (console) included in the long photographing system of FIGS. 1 and 2. FIG. 4 is a flowchart showing the flow of an enlargement factor calculation process executed by the enlargement factor calculation device of FIG. 3. FIG. FIG. 2 is a diagram showing the positional relationship between each device, radiation, and a region of interest of a subject when performing long-length imaging using the long-length imaging system of FIG. 1; 5 is a flowchart showing the flow of calculation processing executed by the enlargement factor calculation device according to the second embodiment in the enlargement factor calculation process of FIG. 4. FIG.

Embodiments of the present invention will be described below with reference to the drawings. However, the scope of the present invention is not limited to what is described in the following embodiments and drawings.

<1. First embodiment>
First, a first embodiment of the present invention will be described with reference to the drawings.

[1-1. Long-length photography system (1)]
First, a schematic configuration of a long length photographing system according to this embodiment will be described.
FIG. 1 is a side view of a long length photographing system 100 according to this embodiment, and FIG. 2 is a side view of another long length photographing system 100A according to this embodiment.

The long-length imaging system 100 includes a radiation imaging system 110 and a console 120, as shown in FIG.
The radiography system 110 and the console 120 are capable of communicating with each other via the communication network NW.
The long imaging system 100 includes a hospital information system (HIS), a radiology information system (RIS), a picture archiving and communication system (PACS), and an image storage system (not shown). It may be connected to an analysis device or the like.

(1-1-1. Radiography system)
The radiography system 110 includes a radiation output device (hereinafter referred to as output device 1), a radiation detector (hereinafter referred to as detector 2), and an imaging table 3.
The devices 1 to 3 are capable of communicating with each other via the communication network NW.

The output device 1 includes a generator 11, a radiation source 12 (tube), an aperture 13, a first moving mechanism 14, and a third moving mechanism 15.
The output device 1 is configured to generate radiation R (for example, X-rays) in a manner that corresponds to a radiographic image to be photographed (a photographed image (including a long image) or a continuously photographed image).

The generator 11 generates preset imaging conditions based on the operation of the imaging instruction switch (for example, conditions related to the subject S such as the imaging region, imaging direction, and physique, tube voltage, tube current, irradiation time, and current duration). A load is applied to the radiation source 12 according to the radiation irradiation conditions (such as the product (mAs value)).
The generator 11 also includes a photographing instruction switch (not shown).

The radiation source 12 is configured to generate radiation R at a dose corresponding to the load from the generator 11.
The radiation source 12 according to this embodiment is configured to emit radiation R in the horizontal direction via an aperture 13.
Further, the radiation source 12 can be rotated about a rotation axis extending in the vertical direction and in a direction perpendicular to the radiation irradiation direction (direction perpendicular to the plane of the paper in FIG. 1).
Therefore, the radiation source 12 can irradiate the radiation R vertically downward, for example.

The aperture 13 controls the width of the rectangular aperture it forms in the body axis direction based on the control from the console 120, so that the radiation emitted by the radiation source 12 is applied to the imaging surface 22, which will be described later. It is configured such that the width of the irradiation field in the body axis direction can be changed.
This "body axis direction" refers to the direction in which the body axis of the subject S extends.
The elongated photographing system 100 shown in FIG. 1 is for photographing a subject S in a standing position. Therefore, in the elongated imaging system 100 shown in FIG. 1, the vertical direction (the up-down direction in FIG. 1) is the body axis direction.
Note that the diaphragm 13 may be configured to be able to change the width of the opening in the direction perpendicular to the body axis direction.
Further, the diaphragm 13 includes a width sensor 13a that detects the width of the aperture formed by the diaphragm 13 in at least the body axis direction.
In addition, the aperture 13 emits visible light in the same direction as the irradiation direction of the radiation R in a range equal to the irradiation field of the radiation R, thereby making it possible for the user to recognize the width of the irradiation field in the body axis direction. It has become.

The first moving mechanism 14 is configured to be able to move the radiation source 12 and the aperture 13 in the body axis direction.
Note that the first movement mechanism 14 may be configured to move the radiation source 12 and the aperture 13 manually by a user's operation, or automatically based on control from the console 120. It's okay.
The first moving mechanism 14 also includes a first position sensor 14a that detects the position (distance and height from the starting point of movement) of the radiation source 12.

The third moving mechanism 15 is configured to be able to move the radiation source 12 and the aperture 13 in a direction (horizontal direction) perpendicular to the radiation entrance surface 21 of the detector 2 .
Note that the third movement mechanism 15 may be configured to move the radiation source 12 and the aperture 13 manually by a user's operation, or automatically based on control from the console 120. It's okay.
Further, the third movement mechanism 15 includes a third position sensor 15a that detects the position of the radiation source 12 (distance from the starting point of movement).

The detector 2 includes a sensor section (not shown), a scanning drive section, a reading section, a control section, and an output section.

The sensor section includes a substrate (not shown), a plurality of semiconductor elements, a plurality of scanning lines (not shown), a plurality of signal lines, and a plurality of switch elements.
The plurality of scanning lines are provided on the surface of the substrate so as to extend parallel to each other at predetermined intervals.
The plurality of signal lines are provided on the surface of the substrate so as to extend parallel to each other at predetermined intervals in a direction perpendicular to the direction in which the scanning lines extend.
That is, the plurality of scanning lines and the plurality of signal lines form a grid.

The plurality of semiconductor elements are respectively provided in a plurality of rectangular regions partitioned by a plurality of scanning lines and a plurality of signal lines on the surface of the substrate.
As described above, since the plurality of scanning lines and the plurality of signal lines form a grid, the plurality of semiconductor elements are arranged in a matrix.
Each semiconductor element is designed to generate an electric charge depending on the dose of radiation received.
The plurality of switch elements are provided near each semiconductor element.
Each switch element can be switched to an on state in which charge can be released from the semiconductor element to the signal line, or an off state in which charge cannot be released from the semiconductor element to the signal line, depending on the voltage applied to the scanning line. It has become.
Hereinafter, the surface of this substrate on which the semiconductor elements are formed will be referred to as the imaging surface 22, and the area on the imaging surface 22 where the semiconductor elements are arranged will be referred to as the radiation detection area 22a.

The scan drive unit is configured to be able to turn on/off each switch element.
The readout section is configured to read out the amount of charge released from each pixel as a signal value.
The control section is configured to control each section of the detector 2 and generate image data of a radiation image from the plurality of signal values read out by the reading section.
The output unit is configured to be able to output generated image data and the like to other devices (such as the console 120).
The detector 2 configured in this manner generates a radiation image according to the radiation received on the imaging surface 22 (radiation detection area 22a) in synchronization with the timing at which radiation is irradiated from the output device 1. ing.

The photographing stand 3 includes a support 31, a second moving mechanism 32, a loading section 33 (buckie), and a screen 34.

The support column 31 is provided so as to extend in the vertical direction.
Note that when the long-length imaging system 100 is installed in a photography room, a wall of the photography room may be used instead of the support 31.
The second moving mechanism 32 is provided on the support column 31 and is configured to be able to move the loading section 33 in the body axis direction.
Note that the second moving mechanism 32 may be configured to move the loading section 33 manually by a user's operation, or may be configured to move the loading unit 33 automatically based on control from the console 120. .
Further, the second moving mechanism 32 includes a second position sensor 32a that detects the position of the detector 2 (distance and height from the starting point of movement).
Further, the second moving mechanism 32 may be configured to be able to move the detector 2 in a direction perpendicular to the radiation entrance surface 21 or in a direction perpendicular to the plane of FIG. 1 .
The loading section 33 holds the detector 2 so that the radiation entrance surface 21 faces the radiation source 12 . That is, the second moving mechanism 32 moves the detector 2 in the body axis direction via the loading section 33.
The screen 34 is provided at a position where the subject S stands between the radiation source 12 and the detector 2 so as to extend vertically and spread parallel to the radiation entrance surface 21 of the detector 2 .

(1-1-2. Console)
The console 120 serves as an enlargement factor calculation device, and is composed of a PC or a dedicated device.
The console 120 is capable of stitching together a plurality of radiographic images generated by the radiography system 110 to generate a long image.
Details of this console 120 will be described later.

Although FIG. 1 illustrates the console 120 that also serves as an enlargement factor calculation device, the enlargement factor calculation device may be another device independent from the console.
Further, although FIG. 1 illustrates the long-length imaging system 100 that includes one console 120, the long-length imaging system 100 includes a console for controlling each device, and various types of radiographic images generated by the detector 2. The image forming apparatus may include a console for performing processing (including generation of a long image).

(1-1-3. Operation)
The elongated image capturing system 100 according to the present embodiment configured as described above is capable of performing elongated image capturing.
Specifically, by repeatedly photographing the subject S while moving the radiation source 12 and the detector 2 in the body axis direction, a plurality of radiation images each having an image overlapping area necessary to obtain a long image are obtained. generate.
The console 120 then generates a long image from the plurality of radiographic images.

[1-2. Long-length photography system (2)]
Another long-length photographing system 100A is different from the above-described long-length photographing system 100 in the configuration of the photographing table 3A.
Specifically, as shown in FIG. 2, the imaging platform 3A in the other long imaging system 100A includes a support section 35, a top plate 36, a fourth moving mechanism 37, and a loading section 38. There is.

The support part 35 is placed on the floor.
The top plate 36 is arranged so as to extend horizontally above the support part 35.
The fourth moving mechanism 37 is provided inside the support section 35 (below the top plate 36) and is configured to be able to move the loading section 38 in the body axis direction.
Another long photographing system 100A shown in FIG. 2 is for photographing a subject S in a supine position. Therefore, in the elongated imaging system 100 shown in FIG. 2, the horizontal direction (the left-right direction in FIG. 2) is the body axis direction.
Note that the fourth movement mechanism 37 may be configured to move the loading unit 38 manually by a user's operation, or may be configured to move the loading unit 38 automatically based on control from the console 120. .
Further, the fourth moving mechanism 37 includes a fourth position sensor 37a that detects the position of the detector 2 (distance and height from the starting point of movement).
The loading section 38 holds the detector 2 so that the radiation entrance surface 21 faces the radiation source 12 . That is, the fourth moving mechanism 37 moves the detector 2 in the body axis direction via the loading section 38.

Due to this difference in the configuration of the imaging table 3A, the radiation source 12 according to this embodiment emits the radiation R vertically downward via the aperture 13.

Moreover, the roles of the first moving mechanism 14 and the third moving mechanism 15 are reversed.
That is, the first moving mechanism 14 is configured to be able to move the radiation source 12 and the aperture 13 in a direction (vertical direction) orthogonal to the radiation entrance surface 21 of the detector 2.
Further, the third moving mechanism 15 is configured to be able to move the radiation source 12 and the aperture 13 in the body axis direction.

[1-3. console〕
Next, details of the console 120 included in the long image capturing system 100, 100A will be described.
FIG. 3 is a block diagram showing the console 120, FIG. 4 is a flowchart showing the flow of magnification calculation processing executed by the console 120, and FIG. 5 is each device used when performing long length imaging using the long length imaging systems 100 and 100A. , is a diagram showing the positional relationship between radiation and a region of interest of a subject.
Note that the symbols in parentheses in FIGS. 3 and 4 refer to the second embodiment described later.

(1-3-1. Configuration)
As shown in FIG. 3, the console 120 includes a control section 121, a communication section 122, a storage section 123, a display section 124, and an operation section 125.
Each part 121 to 125 is electrically connected by a bus or the like.

The control unit 121 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), and the like.
The CPU of the control unit 121 reads various programs stored in the storage unit 123, expands them into the RAM, executes various processes according to the expanded programs, and centrally controls the operations of each part of the console 120. It has become.

The communication unit 122 is composed of a communication module and the like.
The communication unit 122 transmits various signals and data to other devices connected via a communication network NW (LAN (Local Area Network), WAN (Wide Area Network), Internet, etc.) via wired or It is designed to transmit and receive wirelessly.

The storage unit 123 includes a nonvolatile semi-dynamic memory, a hard disk, and the like.
Furthermore, the storage unit 123 stores various programs executed by the control unit 121 and parameters necessary for executing the programs.
Note that the storage unit 123 may be capable of storing image data of radiographic images (including long images).

The display unit 124 is composed of a monitor such as an LCD (Liquid Crystal Display) or a CRT (Cathode Ray Tube) that displays images.
The display unit 124 is configured to display various images and the like based on control signals input from the control unit 121.
Note that, as described above, when the console 120 is divided into a console for controlling each device and a console for performing various processes on the radiation image generated by the detector 2, each console has a display section. Alternatively, one of the consoles may include a display unit, and this display unit may display information for both consoles.

The operation unit 125 according to the present embodiment can be operated by the user using a keyboard equipped with cursor keys, numeric input keys, various function keys, etc., a pointing device such as a mouse, a touch panel laminated on the surface of the display unit 124, etc. It is composed of
The operation unit 125 is configured to output a control signal to the control unit 121 according to an operation performed by the user.
Note that, as described above, when the console 120 is divided into a console for controlling each device and a console for performing various processes on the radiation image generated by the detector 2, each console has an operation section. Alternatively, one of the consoles may be provided with an operation section, and both consoles may be operated using this operation section.

(1-3-2. Operation)
The control unit 121 of the console 120 configured in this manner has a function of accepting a user's selection of an imaging mode (type of radiographic image to be imaged).
Specifically, a list screen of shooting modes is displayed on the display section 124, and one of the shooting modes displayed on the display section 124 can be selected using the operation section 125.

Further, the control unit 121 has a function of acquiring information on the height and position of the radiation source 12 from the first and third position sensors 14a and 15a of the output device 1.
Further, the control unit 121 has a function of acquiring information on the height of the detector 2 from the second position sensor 32a of the photographing table 3 or the fourth position sensor 37a of the photographing table 3A.
The control unit 121 also has a function of acquiring the width of the aperture of the aperture 13 at least in the body axis direction from the width sensor 13a of the aperture 13.
Further, the control unit 121 controls the aperture of the aperture emitted from the radiation source 12 based on the aperture of the aperture 13, the distance between the focus F of the radiation in the radiation source 12, and the radiation detection area 22a of the detector 2 (hereinafter referred to as SID). It has a function of calculating which range on a plane that coincides with the imaging surface 22 is irradiated with the radiation focused by 13.

Further, the control unit 121 has a function of controlling the operation of the first moving mechanism 14 to move the radiation source 12 to an arbitrary height.
Further, the control unit 121 has a function of controlling the operation of the third moving mechanism 15 to move the radiation source 12 to an arbitrary position.
Further, the control unit 121 has a function of controlling the operation of the second moving mechanism 32 to move the detector 2 to an arbitrary height.
Further, the control unit 121 has a function of controlling the operation of the diaphragm 13 and changing the aperture of the diaphragm 13 to an arbitrary opening direction.

Furthermore, when performing long length imaging, the control unit 121 controls the first moving mechanism 14 and the second moving mechanism 3 so that the width of the area where the irradiation field overlaps between one imaging and another imaging is 80 mm or less. It has the function of controlling the operation of the
When performing long-length imaging, the control unit 121 according to the present embodiment controls the width of the irradiation field in the body axis direction in one imaging to be different from the width in the body axis direction of the irradiation field in other imaging. It has a function of controlling the operations of the first moving mechanism 14 and the second moving mechanism 32.

The control unit 121 thus functions as an operation control means by controlling the height of the detector 2, the height of the radiation source 12, the position of the radiation source 12, and the operation of the aperture of the diaphragm 13.
Then, the user operates the irradiation instruction switch while the height of the radiation source 12, the position of the radiation source 12, the height of the detector 2, and the opening of the aperture 13 are controlled to the user's desired state. , the radiation source 12 generates radiation and the detector 2 generates a radiation image, allowing the user to obtain a radiation image of any region at any position.

Furthermore, the control unit 121 has a function of generating a long image from a plurality of radiographic images.
This "long image" is an image obtained by overlapping and connecting image overlapping areas of a plurality of radiation images, each of which has an image overlapping area.
In order to generate a long image, whether automatically or manually, a region in which the region of interest Sa of the subject S is commonly captured is required in both radiographic images to be combined. This area is the image overlap area.
The control unit 121 forms a long image generation means by generating the long image in this way.
Further, generating a radiographic image having an image overlap region corresponds to an imaging step in the magnification calculation method.

In addition, the control unit 121 determines that a predetermined condition is satisfied (for example, that a predetermined operation is performed on the operation unit 125, that a predetermined control signal is received from another device, that the detector 2 starts generating a radiation image). It has a function of executing the enlargement magnification calculation process shown in FIG.
In this enlargement magnification calculation process, the control unit 121 first executes an acquisition process (step S1).
In this acquisition process, the control unit 121 acquires a plurality of radiation images.
The plurality of radiation images have different geometric imaging conditions, and each has an image overlapping area in which the region of interest Sa of the subject S is commonly captured.
The control unit 121 according to the present embodiment is configured to acquire a plurality of radiographic images, each having an image overlap region necessary to obtain a long image, from the radiographic system 110.
That is, the geometric imaging conditions according to this embodiment are the height of the focal point of radiation, the SID, the irradiation angle, and the height of the detector 2.

As for the geometric photographing conditions, it is good to have information on the focal point height, SID, and irradiation angle, and it is even better to have information on the height of the detector 2. Further, the relationship between the height of the focal point and the height of the detector 2 is often known, and furthermore, the SID and the irradiation angle are also often constant. In such cases, the height of the focal point alone is sufficient. That is, the conditions that need to be acquired differ depending on the details of device control.
Furthermore, as long as the radiographic images to be acquired have a common image overlap region, they do not need to be for obtaining long images; for example, even if they are radiographic images for use in tomosynthesis. good.
The control unit 121 functions as an acquisition means by executing the acquisition processing described above.

After acquiring a plurality of radiation images, the control unit 121 according to the present embodiment executes region determination processing (step S2).
In this area determination process, the control unit 121 determines image overlapping areas in the plurality of radiographic images.
The control unit 121 according to the present embodiment is configured to perform similarity judgment on a plurality of acquired radiographic images by image processing, and determine image overlapping regions in each of the plurality of radiographic images.

Note that the control unit 121 may be configured to determine image overlap regions in each of the plurality of radiographic images based on the operation performed on the operation unit 125, or to determine the image overlap area in each of the plurality of radiographic images based on the operation performed on the operation unit 125. The image overlapping area in the radiation image of the eye may be determined, and the position of the image overlapping area in the second radiation image may be determined based on the determined image overlapping area in the first radiation image. .
In this way, since the region of interest can be selected, the magnification of the region of interest that is automatically determined by the control unit 121 in the depth direction of the subject (direction perpendicular to the height direction and the direction of radiation irradiation) is different from the magnification of the region of interest. Magnification can be calculated.
Moreover, the control unit 121 may not determine the entire area determined to be similar as the image overlapping area as a result of the similarity determination, but may determine only a part of the area as the image overlapping area.
The control unit 121 functions as a region determining means by executing this region determining process.

After determining the image overlap area, the control unit 121 executes calculation processing (step S3).
In this calculation process, the control unit 121 calculates the enlargement magnification of the radiographic image for the subject based on the plurality of image overlapping regions in the plurality of acquired radiographic images.
The control unit 121 according to the present embodiment calculates the magnification based on the width of the image overlapping area in the body axis direction, the height of the focal point in each imaging, the SID, the irradiation angle, and the height of the detector 2. It has become.

Hereinafter, a specific method for calculating the enlargement magnification will be explained using FIG. 5. Note that each point shown in FIG. 5 is a point in space. Specifically, first, the positions of point F and point H shown in FIG. 5 are calculated.
Point F is the point where the upper end of the image overlap area, determined by similarity judgment or specified by the user, is obtained in the second imaging, so It can be calculated based on the position of the detector 2 at the time of photographing.
Point H is the point where the upper end of the image overlap area, determined by similarity judgment or specified by the user, was obtained in the first image, so It can be calculated from the position of the detector 2 at the time of photographing.

Since the heights and SIDs of points E and M are known values (values that can be obtained from each sensor), the heights of points A and A', which are at the same height as points E and M, are also known values. be.
Therefore, the angle between the line segment a' and the optical axis (line segment c') can be calculated based on the distance between the points M and F and the SID. Hereinafter, the angle between the calculated line segment a' and the optical axis will be referred to as α.
Similarly, the angle between the line segment q and the optical axis (line segment c) can also be calculated based on the distance between points E and H and the SID. Hereinafter, the angle between the calculated line segment q and the optical axis will be referred to as β.

The SID in the first photograph and the SID in the second photograph may be the same or different, but if they are equal, Γ is the distance between points F and G, Ζ is the distance between points G and H, and Φ When is the distance between point B and point G, the following formulas (a) to (c) hold true.
Γ+Ζ=distance between point F and point H...(a)
Γ=Φtanα・・(b)
Ζ= Φtanβ・・(c)
Note that since the heights of points F and H are known values, the distance between points F and H is also a known value.

Φ (distance between point B and point G) calculated by solving simultaneous equations of these equations (a) to (c) is OID.
OID is the distance between the subject S and the detector 2, more specifically, the distance between the target part Sa of the subject S (for example, the spine) and the imaging surface 22 of the detector 2 (Object to Image-receptor Distance). .
Then, an enlargement magnification (SID/(SID-OID)) is calculated based on the SID and the calculated OID.
Note that here, the control unit 121 uses the upper end of the image overlap area for calculation, but may use any arbitrary point within the image overlap area. Alternatively, OIDs can be obtained from a plurality of points, and the average value or median value of the plurality of OIDs obtained can be used as the OID.
The control unit 121 functions as a calculation means by executing the calculation processing described above.
Further, calculating the magnification factor corresponds to a calculation step in the magnification factor calculation method.

After calculating the enlargement magnification, the control unit 121 executes output processing (step S4).
In this output process, the control unit 121 performs a predetermined output based on the calculated magnification factor.
Examples of the predetermined output include the following.
・Display the image of the area of interest in actual size.
・Convert the index (scale) that appears with the area of interest.
・Move the images and display the combined image.
The control unit 121 functions as an output means by executing the output processing described above.
Moreover, performing a predetermined output corresponds to an output step in the enlargement factor calculation method.

[1-4. effect〕
The elongated imaging system 100, 100A equipped with the console 120 (magnification factor calculation device) described above calculates the magnification factor based on a plurality of image overlapping areas in a plurality of radiographic images, so the magnification factor can be determined more accurately than before. It can be calculated as follows.
Furthermore, the radiographic image used for calculating the magnification factor is obtained by performing normal long-length imaging. The long photographing systems 100 and 100A according to the present embodiment do not move the subject when performing long photographing, so there is no need to provide the device with a mechanism for moving the subject, and the work during photographing increases. Not at all.
Furthermore, since the subject does not need to be moved, photography can be carried out safely.
Therefore, according to the console 120 or the long imaging system 100, 100A, the magnification of the target part of the subject in the radiographic image relative to the actual object can be accurately adjusted without complicating the device or increasing the number of steps during imaging. It can be calculated as follows.

This method also has the ability to follow changes in the part of interest.
For example, the magnification is different when the target region is the spine and when the target region is the ribs.
However, by specifying the region of interest in advance, accurate enlargement magnification correction can be performed.
Furthermore, even if the part of interest is changed after imaging, it can be followed.

Furthermore, the results of the image combination process may be modified by the user.
This occurs due to the difference between the image overlap area determined by image processing and the image overlap area desired by the user. That is, the difference is the same as the difference between the requested OID and the OID intended by the user.
According to this method, it is also possible to change the enlargement magnification according to the amount of correction (that is, the amount by which the image has been moved).

<2. Second embodiment>
Next, a second embodiment of the present invention will be described.
Note that, here, the same components as in the first embodiment are given the same reference numerals, and the explanation thereof will be omitted.

[2-1. Long photography system〕
In order to distinguish from the first embodiment, they will be described as long image capturing systems 100B, 100C (see FIGS. 1 to 3) and console 120A (see FIGS. 1 and 4).

[2-2. console〕
The control unit 121 of the console 120A according to the present embodiment has a function of executing an enlargement magnification calculation process different from that of the first embodiment.
Specifically, the enlargement magnification calculation process according to this embodiment differs in the content of the calculation process (step S3A).
In the calculation process according to the present embodiment, a temporary magnification is estimated (step S31), the radiation images are combined using the estimated magnification, and the positional shift of the region of interest on the combined images is evaluated. Then, the tentative magnification is gradually changed, and the tentative magnification that minimizes the positional shift of the region of interest on the combined image is set as the magnification.
Various methods are possible for the initial tentative magnification, such as a preset value, a measured value of the position of the screen 34, and a measured value of the patient's position.
If the initial tentative magnification is significantly different from the desired magnification, it will take time to determine the final magnification. For this reason, in this embodiment, the value is determined by a method other than the preset value, the measured value of the position of the screen 34, and the measured value of the patient's position.

Hereinafter, a specific method for calculating the initial temporary enlargement magnification will be described using FIG. 5.
Note that in order to simplify control, triangle ADL and triangle A'FN in FIG. 5 are congruent, and the distance between points E and M is the same as the focus of the radiation and the amount of movement of the detector 2. I will explain it assuming that it exists.

The region between point B and point C in FIG. 5 is the part of interest of the subject, and the distance between point B and point C (hereinafter referred to as distance BC) is the length of the part of interest.
At this time, the area between points H and L (hereinafter referred to as area HL) is an enlarged image of the region of interest shown in the first radiographic image, and the area between points F and J (hereinafter referred to as area FJ) is an enlarged image of the region of interest shown in the second radiographic image.
In other words, the region HL and the region FJ are image overlapping regions, and these regions are overlapped when generating a long image.

Furthermore, line segment aa is obtained by moving line segment a in parallel so that it passes through point C.
The point where the line segment aa intersects the imaging plane 22 is a point I.
Note that the distance between point A and point E or the distance between point A' and point M is SID, which is a known value obtained from a sensor.
Here, since the triangle CIL is similar to the triangle A'FN, the magnification factor can be calculated if the ratio between the distance FN and the distance IL is known. However, for point I, it is necessary to accurately know the line segment aa, and for this purpose it is necessary to accurately estimate the image overlap area.
Since it is sometimes difficult to accurately estimate the image overlap area, in this embodiment, the distance JL, whose size relationship with the distance IL is known and is easy to obtain, is used, and a temporary magnification factor is determined and recursively performed. Find the magnification factor.

Distance JL can be determined by subtracting distance FJ from distance FL. The distance FL can be easily obtained by subtracting the amount of movement of the detector 2 from the size of the imaging surface 22 of the detector 2, and since the distance FJ is the size of an arbitrary image overlap area, the distance JL can be easily obtained. You can ask for it.
The distance JL is always smaller than the distance IL.
The initial magnification in this embodiment is determined using a triangle similar to triangle A'FN whose base is the distance JL.

After calculating the provisional magnification, the control unit 121 calculates the first and second radiation images based on the provisional magnification, centering on the respective optical axes (points E and M). The image is reduced and the position of one or more points within the image overlap area is determined (step S32).

Next, it is determined whether or not there is a shift in the position of each point in the image overlap region in each of the reduced radiation images (step S33).
Here, if it is determined that there is a shift (step S33; Yes), the control unit 121 proceeds to the process of step S34.
If each radiation image is reduced based on an accurate magnification while keeping the distance of each intersection equal to the amount of movement, the image overlapping regions of each radiation image will overlap exactly. However, in the first step S33, it is determined that there is a deviation because it is based on a triangle similar to the triangle A'FN whose base is the distance JL.

If it is determined that there is a shift in the process of step S33, the control unit 121 executes a temporary enlargement magnification change process (step S34), and returns to the process of step S32.
In this temporary enlargement magnification changing process, the control unit 121 changes the temporary enlargement magnification so that there is no shift in the position of each point in the plurality of reduced radiation images. Specifically, the temporary distance JL is changed and the temporary magnification is recalculated.
That is, the control unit 121 repeats steps S32 and S33 while changing the temporary enlargement magnification until it is determined that there is no deviation in the process of step S33.

If it is determined that there is no deviation in the process of step S33 (step S33; Yes), the control unit 121 executes the determination process (step S35) and ends the calculation process (step S3A) (output in the enlargement magnification calculation process). Proceed to processing (step S4)).
In this determination process, the control unit 121 determines the temporary magnification magnification when the deviation of each point is eliminated as the final magnification magnification.

Note that the distance (interval) between points used for calculation may be small.
Alternatively, the median value or average value of a plurality of sections may be used. In that case, the plurality of sections used are on the same plane parallel to the imaging surface 22 (a region considered to be the same position). It is preferable to choose from among them.
In addition, the control unit 121 uses a human body model or the like to create a shape corresponding to a region that is considered to be on the same plane (for example, it is preferable to focus on one of the spine and ribs) for the image overlap region used for calculation. Good to use.

In addition, since the present embodiment calculates the temporary magnification magnification recursively, the control unit 121 can cause the display unit 124 to display the position of the point while the calculation process is being executed. It may be.
Further, the control unit 121 may have a function of stopping the calculation process midway based on an operation performed on the operation unit 125.
In this case, the control unit 121 serves as a calculation stopping means, and can stop the process at the most preferable stage while displaying the regression process. This is effective because the attention area does not necessarily reflect the user's intention.
Furthermore, the control unit 121 may have a function of changing the enlargement magnification instead of moving the radiation image and displaying a combined image that is synchronized with the change. This is easy to use because it does not require the user to move the radiographic image, which is a complicated task.

Further, the control unit 121 can also set the region of interest used when determining whether there is a shift (step S33) to be different from the region of interest used to obtain the initial tentative enlargement magnification.
For example, when determining the initial magnification, a region close to the detector 2 (if the patient faces the detector 2 and is photographed, the ribs) is set as the region of interest. On the other hand, the region of interest used when determining whether there is a shift (step S33) is a part far from the detector 2 (in the case where the patient is photographed facing the detector 2, the region is the spine).
By doing the above, it is possible to reliably display the attention area intended by the user during the regression process.
Note that since the orientation of the patient at the time of imaging is generally specified in advance as an imaging condition, it is possible to use this to determine each region of interest. Alternatively, it may be determined based on image similarity judgment.

[2-3. effect〕
According to the console 120A described above or the long image capturing systems 100B and 100C equipped with this console 120A, as in the first embodiment described above, without complicating the device or increasing the number of steps during image capturing, It is possible to accurately calculate the magnification of the part of interest of a subject in a radiographic image relative to the real thing.

<3. Others＞
Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the spirit of the present invention.

For example, the control unit 121 according to the present embodiment has a second function of determining the magnification magnification recursively, but calculates the magnification magnification using the method executed by the console according to the first embodiment. It may further have the first function.
If it is difficult to calculate the magnification using one of the first function and the second function, the magnification may be calculated using the other function.

Furthermore, in the description of the above embodiment, the case where the enlargement magnification is calculated based on two radiographic images has been described, but when the number of radiographic images acquired in the above acquisition process is three or more, the control unit 121, for example, The first magnification factor may be calculated based on the first and second radiation images, and the second magnification factor may be calculated based on the second and third radiation images.
Then, the control unit 121 compares the calculated first magnification magnification and the second magnification magnification, and if the two values are different, the control unit 121 sets at least one of the calculated first magnification magnification and the second magnification magnification. Interpolation may be performed for each pixel.
Interpolation may be performed linearly or nonlinearly using a human body model.

1 and 2 illustrate the long imaging systems 100 and 100A installed in the imaging room, but the long imaging systems 100 and 100A are movable systems called rounds. It's okay.
Further, the elongated imaging system 100, 100A may be capable of continuously capturing images in which the generation of radiation and the generation of a radiation image are repeated multiple times in a short period of time.

Further, in the description of the above embodiments, an example is disclosed in which a hard disk, a semiconductor nonvolatile memory, etc. are used as a computer-readable medium for the program according to the present invention, but the present invention is not limited to this example. As other computer-readable media, it is possible to apply a portable recording medium such as a CD-ROM. Further, a carrier wave is also applied as a medium for providing data of the program according to the present invention via a communication line.

100, 100A, 100B, 100C Long imaging system 110 Radiography system 1 Radiation output device 11 Generator 12 Radiation source 13 Aperture 13a Width sensor 14 First moving mechanism 14a First position sensor 15 Third moving mechanism 15a Third position sensor 2 Radiation detector 21 Radiation entrance surface 22 Imaging surface 22a Radiation detection area 3, 3A Imaging table 31 Support column 32 Second moving mechanism 32a Second position sensor 33 Loading section 34 Screen 35 Support section 36 Top plate 37 Fourth moving mechanism 37a Fourth Position sensor 38 Loading section 120, 120A Console (magnification calculation device)
121 Control unit 122 Communication unit 123, 123A Storage unit 124 Display unit 125 Operation unit

Claims (18)

an acquisition means for acquiring a plurality of radiographic images each having different geometric imaging conditions and each having an image overlap region in which a region of interest of a subject is commonly captured;
Calculation means for calculating an enlargement magnification of the radiographic image of the target region of the subject relative to the actual object, based on the plurality of image overlapping regions in the plurality of radiographic images acquired by the acquisition means;
An enlargement magnification calculation device comprising: an output means that performs a predetermined output based on the enlargement magnification calculated by the calculation means. The acquisition means includes a radiation source and a radiation detector that generates the radiation image according to the radiation received on the imaging surface, and the radiation imaging system capable of photographing the subject includes the radiation source and the radiation detection device. A plurality of images each having the image overlapping area necessary to obtain a long image generated by repeatedly photographing the subject while moving a device in the body axis direction, which is an extension direction of the body axis of the subject. acquiring the radiographic image;
The calculation means calculates the width of the image overlapping region in the body axis direction, the height of the focal point of the radiation in each imaging of the irradiation field, which is the range in which the radiation emitted by the radiation source is irradiated onto the imaging surface, and the height of the focal point of the radiation. The magnification factor calculation device according to claim 1, wherein the magnification factor is calculated based on a distance between a focal point and a radiation detection area of the radiation detector, an irradiation angle of radiation, and a height of the radiation detector. The acquisition means includes a radiation source and a radiation detector that generates the radiation image according to the radiation received on the imaging surface, and the radiation imaging system capable of photographing the subject includes the radiation source and the radiation detection device. A plurality of images each having the image overlapping area necessary to obtain a long image generated by repeatedly photographing the subject while moving a device in the body axis direction, which is an extension direction of the body axis of the subject. acquiring the radiographic image;
The calculation means is
Estimate the temporary magnification factor,
Reducing the plurality of radiographic images based on the temporary magnification factor around each optical axis, and determining the position of one or more points within the image overlap region;
repeating the reduction of the radiation image and the determination of the position of the point by changing the provisional enlargement magnification so that there is no deviation in the position of each point in the plurality of reduced radiation images;
2. The enlargement magnification calculation device according to claim 1, wherein the tentative enlargement magnification at which the deviation of each point is eliminated is determined as the enlargement magnification. The magnification factor according to claim 3, wherein the calculation means estimates the initial tentative magnification factor based on at least one of a preset value, a measured value of the position of the screen, and a measured value of the position of the subject. Calculation device. 5. The calculating means uses, as the image overlapping region used for calculation, a part of the human body model that is considered to be on a plane at the same distance as the part of interest in the optical axis direction. Magnification calculation device. The magnification calculation device according to any one of claims 1 to 5, wherein the output means moves the radiation image and displays a combined image as the predetermined output. The output means changes the magnification of at least one of the plurality of radiographic images, synchronizes the magnification of another radiographic image with the change, and combines the plurality of radiographic images as the predetermined output. The enlargement magnification calculation device according to any one of claims 1 to 5, which displays an image. 6. The magnification factor calculation device according to claim 3, wherein the output means is capable of displaying the position of the point while the calculation means is executing the process. Equipped with a control panel that can be operated by the user,
9. The enlargement magnification calculation device according to claim 8, further comprising calculation stop means for stopping midway through the process executed by said calculation means based on an operation performed on said operation unit. The calculation means is
The magnification factor is based on the width in the body axis direction, the width in the body axis direction in each imaging of the irradiation field, the amount of movement of the radiation source, and the distance between the focal point of radiation and the radiation detection area of the radiation detector. The first function is to calculate
estimating a provisional magnification, reducing the plurality of radiographic images around their respective optical axes based on the provisional magnification, and determining the position of one or more points within the image overlap region; In order to eliminate any deviation in the position of each point in the plurality of reduced radiographic images, the provisional enlargement magnification is changed and the reduction of the radiographic image and the determination of the position of the point are repeated, so that the deviation in each point is eliminated. a second function of determining the temporary magnification magnification when the magnification magnification is the magnification magnification;
Enlargement according to claim 2, wherein when it is difficult to calculate the enlargement factor using one of the first function and the second function, the enlargement factor is calculated using the other function. Magnification calculation device. 9. Any one of claims 1 to 8, further comprising region determining means for determining the image overlap region in each of the plurality of radiographic images by performing a similarity judgment by image processing on the plurality of radiographic images obtained by the obtaining means. The magnification factor calculation device according to item (1). An operation section that can be operated by the user;
The enlargement magnification calculation device according to any one of claims 1 to 8, further comprising: area determining means for determining each of the image overlapping areas in the plurality of radiographic images based on an operation performed on the operation unit. . An operation section that can be operated by the user;
The image overlapping area in the first radiation image is determined based on the operation performed on the operation unit, and the image overlapping area in the second radiation image is determined based on the determined image overlapping area in the first radiation image. The enlargement magnification calculation device according to any one of claims 1 to 10, further comprising area determining means for determining the position of the image overlapping area in an image. a radiation source;
an aperture that changes the width of an irradiation field, which is a range in which radiation emitted from the radiation source is irradiated onto an imaging surface;
a first movement mechanism that moves the radiation source and the aperture in a body axis direction that is an extension direction of the subject's body axis;
a radiation detector that generates a radiation image according to radiation received on the imaging surface;
a second movement mechanism that moves the radiation detector in the body axis direction;
A long image generating means that generates a long image by overlapping and connecting image overlapping regions generated by repeatedly photographing the subject while the radiation source and the radiation detector move in the body axis direction. and,
Calculating means for calculating an enlargement magnification of the radiographic image of the target region of the subject relative to the actual object based on the plurality of image overlapping regions in the plurality of radiographic images generated by the radiation detector;
An elongated photographing system comprising: an output means that performs a predetermined output based on the magnification factor calculated by the calculation means. The first moving mechanism and the second The elongated photographing system according to claim 14, further comprising an operation control means for controlling the operation of the moving mechanism. The operation control means controls the first movement mechanism and the second movement mechanism so that the width of the irradiation field in the body axis direction in one imaging is different from the width of the irradiation field in the body axis direction in another imaging. The elongated photographing system according to claim 15, wherein the operation of the moving mechanism can be controlled. to the computer,
an acquisition process of acquiring a plurality of radiographic images each having different geometric imaging conditions and each having an image overlap region in which a region of interest of a subject is commonly captured;
a calculation process of calculating an enlargement magnification of the radiographic image of the target region of the subject relative to the actual object, based on the plurality of image overlapping regions in the plurality of radiographic images acquired in the acquisition process;
A program that executes an output process of performing a predetermined output based on the magnification factor calculated in the calculation process. an imaging step of generating a plurality of radiographic images each having different geometric imaging conditions and each having an image overlap region in which a region of interest of a subject is commonly captured;
a calculation step of calculating an enlargement magnification of the radiographic image of the target region of the subject relative to the actual object based on the plurality of image overlapping regions in the plurality of radiographic images generated in the imaging step;
An enlargement magnification calculation method comprising: an output step of performing a predetermined output based on the enlargement magnification calculated in the calculation step.

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