JP2009254657A - Radiographic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiographic device capable of stereoscopically capturing an object in a simple configuration without the need of complicated control. <P>SOLUTION: An irradiating part 2 is provided with a switching part 14 for switching a focus F to a small focus and a big focus, a radiation detection part 3 acquires a first image which is a projection image when it is the small focus and a second image which is a projection image when it is the big focus, and an image processing part 4 specifies a difference between the blurring degree of the first image and the blurring degree of the second image from a difference between the second image and the first image, performs image processing of emphasizing and gradation or the like correspondingly to the difference of the blurring degree to the object part of the first image to generate a third image. Thus, a distance between the irradiating part 2 and the object S is estimated, and the anteroposterior relation of the plurality of objects which are imaged simultaneously is specified. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radiation imaging apparatus that obtains a projected image of a subject by irradiating radiation, and more particularly, to a radiation imaging apparatus that can easily specify the relative positional relationship of a plurality of subjects that are simultaneously captured.

  In recent years, various types of radiation imaging apparatuses have been developed for each imaging target and imaging purpose. Radiation imaging apparatuses are roughly classified into a type that irradiates a subject with radiation from one direction and a type that performs tomographic imaging by irradiating radiation from a plurality of directions. Among these, the latter type of radiation imaging apparatus (for example, CT) is capable of observing a subject three-dimensionally, and in particular in the medical field, in order to grasp the detailed state of the affected area and perform an accurate diagnosis It has become indispensable.

  However, the latter type of radiation imaging apparatus is generally expensive and difficult to introduce into a small medical institution or the like.

Therefore, as one of attempts to stereoscopically view a subject using a simpler method than the latter type, a radiation imaging apparatus shown in FIG. 6 has been studied (for example, see Patent Document 1).
This radiation imaging apparatus is based on a so-called stereo system and includes radiation irradiation units 32R and 32R corresponding to the left and right eyes. When the subject S placed on the support base 31 is irradiated with radiation by the radiation irradiators 32R and 32R, the radiation transmitted through the subject S is detected by the radiation detector 33.
The radiation detection unit 33 includes, for example, an image intensifier (I.I.), a TV camera, and an A / D converter. The projection image by the radiation irradiation unit 32R and the projection image by the radiation irradiation unit 32L are respectively digitalized. The data is converted into data and stored in the storage unit 34.

  The left / right switching unit 35 alternately outputs the two projection images stored in the storage unit 34 to the monitor 36 with a predetermined time. The left / right switching unit 35 alternately opens and closes the shutters 30R and 30L in synchronization with the monitor output. That is, when the projection image by the radiation irradiation unit 32R is displayed on the monitor 36, the shutter 30R is opened and the shutter 30L is closed. On the contrary, when the projection image by the radiation irradiation unit 32L is displayed on the monitor 36, the shutter 30R is closed and the shutter 30L is opened.

As a result, the observer X can fuse the two projected images displayed alternately and recognize it as one image viewed with the right eye and the left eye, and can pseudo-stereoscopically view the subject S.
JP-A-9-31471

  However, as described above, the conventional radiation imaging apparatus shown in FIG. 6 needs to accurately synchronize the shutters 30R and 30L and the monitor output, and the control is complicated. Further, if the screen of the monitor 36 is continuously viewed through the shutters 30R and 30L for a long time, there is a problem that the eyes of the observer X tend to get tired.

  Therefore, the present invention provides a radiation imaging apparatus capable of capturing a subject in three dimensions by generating an image with a simple configuration and capable of estimating the distance between the subject and the radiation irradiation unit without requiring complicated control. The issue is to provide.

In order to solve the above problems, a radiation imaging apparatus according to the present invention provides:
A radiation irradiating unit disposed on one side of the subject and irradiating the subject with radiation having a predetermined focus, and a radiation disposed on the opposite side of the radiation irradiating unit with respect to the subject and transmitted through the subject A radiation detection unit that acquires a projection image of the subject and an image processing unit that appropriately processes the projection image, wherein the radiation irradiation unit includes the focus At least a first focus and a second focus having a dimension larger than the first focus, and the radiation detection unit includes a first image that is the projection image when the first focus is selected, A second image that is the projection image at the time of selecting a second focus is acquired, and the image processing unit calculates a degree of blur of the subject in the first image from a difference between the second image and the first image, and Second A difference in degree of blur of the subject in the image is specified, a third image is generated by performing image processing according to the difference in degree of blur on the subject portion of the first image or the second image, and The distance between the radiation irradiation unit and the subject can be estimated from three images.

  The image processing in the radiation imaging apparatus preferably increases the degree of blurring of the contour portion of the subject as the distance between the radiation irradiation unit and the subject increases.

  Further, in the image processing in the radiation imaging apparatus, the image processing is to color a contour portion of the subject using a color selected according to a distance between the radiation irradiation unit and the subject. Is preferred.

  In this specification, the term “focal point” means the cross-sectional area of the radiation bundle at the irradiation port of the radiation irradiating unit, and “large focus” means that the cross-sectional area of the radiation bundle is wide.

  According to the present invention, a projection image captured at a different focus is compared by paying attention to the degree of blur of the contour portion of the subject, so that the subject and the radiation irradiation can be performed with a simple configuration without requiring complicated control. It is possible to provide a radiation imaging apparatus capable of estimating the distance between the two parts and capturing the subject in three dimensions.

First, the basic principle of the radiation imaging apparatus according to the present invention will be described with reference to FIG.
FIG. 1A is a diagram illustrating the relationship between the subject S and the projection image I ′ detected by the radiation detection unit 3 when the focal point F of the irradiated radiation is “point”. In this case, “blurring” described later does not occur in the projection image I ′.

As shown in FIG. 1B, when the focal point F ₁ has the dimension f ₁ , there is a region around the projection image I ′ where the radiation dose is larger than that of the projection image I ′. For this reason, the projection image of the subject S obtained by the radiation detection unit 3 becomes “blurred” due to the extended outline of the projection image I ′.
Hereinafter, in this specification, the projected image including the blurred area is referred to as “projected blurred image I”, and the blurred area around the projected image I ′ is referred to as “projected blurred area”.

In FIG. 1B, the degree of blur of the projected image I ′ can be expressed by a blur width W ₁ of a projected blur area having a donut shape. The blur width W ₁ can be calculated by the geometric arrangement of the focal point F ₁ , the subject S, and the radiation detection unit 3. That is, the blur width W ₁ can be calculated by the following equation.

W ₁ = f ₁ × (b / a) (1)

Here, the variable a is the distance between the focal point F ₁ and the subject S, and the variable b is the distance between the subject S and the radiation detector 3. As is clear from the equation (1), the blur width W ₁ is proportional to the focal spot size f ₁ .

FIG. 1C is a diagram illustrating a case where the focal point F ₂ has a dimension f ₂ (where f ₂ > f ₁ ). In this case, the degree of blur of the projection image I ′, that is, the blur width W ₂ can be calculated by the following equation as in the case of FIG.

W ₂ = f ₂ × (b / a) (2)

As above, the dimensions _{f 2} is larger than the dimension _{f 1.} Therefore, the blur width W ₂ which is calculated by the equation (2) is larger than the blur width W ₁ calculated by equation (1). The blur width difference ΔW when the focal spot size is changed can be calculated by the following equation from the equations (1) and (2).

ΔW = W ₂ −W ₁ = (f ₂ −f ₁ ) × (b / a) (3)

In other words, if the dimensions f ₁ and f ₂ and the focus-radiation detection unit distance (a + b) are known, the blur-width difference ΔW is calculated, so that the focus-subject distance a and the subject-radiation detection unit distance b are calculated. Can be identified respectively.

Specifically, in FIGS. 1B and 1C, it is known in advance that f ₁ = 10 mm, f ₂ = 20 mm, and a + b = 500 mm, and when the calculated blur width difference ΔW is 10 mm, From formula (3), it can be specified that the distances a and b are both 250 mm. In FIGS. 1D and 1E, it is known in advance that f ₁ = 10 mm, f ₂ = 20 mm, and a + b = 500 mm. When the calculated blur width difference ΔW is 2.5 mm, the distance a Can be specified to be 400 mm and the distance b is 100 mm.
Further, by comparing the blur width difference ΔW (= 10 mm) in the cases of FIGS. 1B and 1C with the blur width difference ΔW (= 2.5 mm) in the cases of FIGS. The anteroposterior relationship of the subject viewed from the focal point side can be specified.

  Subsequently, a preferred embodiment of a radiation imaging apparatus according to the present invention using the above basic principle will be described with reference to FIGS.

The radiation imaging apparatus according to the first embodiment illustrated in FIG. 2 mainly detects a radiation irradiation unit 2 that emits radiation toward the subject S placed on the support 1 and the radiation transmitted through the subject S. A radiation detection unit 3 that outputs a projection image as digital data, an image processing unit 4 that performs appropriate processing on the projection image data, and a monitor 5 that displays the processed projection image.
Various types of radiation detectors 3 are known, but it is preferable to apply a flat panel detector (FPD) that can directly output detected information as digital data. I. I. Is applied, the detected information is converted into digital data and output by combining a TV camera and an A / D converter.

  The radiation irradiating unit 2 includes a first filament 10a and a second filament 10b connected in series. The switching unit 14 uses only the first filament 10a or the first filament 10a and the second filament 10b. It is possible to switch between using both. When the switching unit 14 is set to the state shown in FIG. 2, the filament current supplied from the filament power supply 13 flows to the first filament 10a and the second filament 10b, and thermoelectrons are emitted from both filaments. The emitted thermoelectrons are accelerated by the electric field generated by the high voltage power supply 12 and collide with the target 11. The radiation generated from the target 11 is emitted toward the subject S.

As shown in FIG. 2, the radiation bundle (focal point F) of the radiation emitted from the radiation irradiation unit 2 depends on the size of the filament. That is, in the radiation imaging apparatus according to the present invention, the switching unit 14 can select the size of the focal point F (large focal point (dimension f ₂ ) / small focal point (dimension f ₁ )).

  The focus switching unit 6 controls the operation of the switching unit 14 and transmits to the storage unit 20 of the image processing unit 4 the setting state of the switching unit 14, that is, which side of the large focus / small focus is selected. When the large focal point is selected (state in FIG. 2), the projection image data output from the radiation detection unit 3 is stored in the second storage unit 20 b of the storage unit 20. On the other hand, when the small focus is selected, the data of the projection image is stored in the first storage unit 20a.

As shown in FIG. 3, when the subject S (see FIG. 2) consists of two object S _F and S _B, it is displaced the x, y, and z directions, the first memory unit 20a, data in Figure 4 the image _{P 1} shown in (a) is stored. The second storage section 20b, the data of the image _{P 2} shown in FIG. 4 (B) is stored.
The subjects S _F and S _B schematically represent, for example, two blood vessels that appear to partially overlap when viewed from the focal side. When the deviations of the subjects S _F and S _{B in} the z direction (see FIG. 3) are a slight difference, it is difficult to determine the front-rear relationship of the subjects S _F and S _B only from the image P ₁ or the image P _2. is there.

Since the image _{P 2} is imaged by a large focus, projection blurred image _{I F2, I B2} of the image _{P 2} is projected blurred image _I F1 of the image _{P 1} taken in a small _focus, blurring degree than _{I B1} large. Also, as viewed from the focus side, since the subject S _B is located on the far side of the subject S _F (rear), projected blurred image I _B2 is larger blur degree than the projected blurred image I _F2.

In the first storage unit 20a and the second storage unit 20b, respectively, after the data of the image _{P 1} and the image _{P 2} is stored, the difference between the image _{P 1} and the image _{P 2} is determined by the comparator 21, FIG. 4 ( data of the image P ₃ shown in C) is generated. That is, the image _{P 3} is projected blurred image _{I F1,} and so by extracting the difference _{I B1} and projection blurred image _{I F2, I B2,} the blur width difference [Delta] W _F of the object, may specify [Delta] W _B Is. In the image P _3, the blur width difference [Delta] W _F of the subject S _F which is located on the front side (front side) is smaller than the blur width difference [Delta] W _B of the subject S _B, which is located on the back side (rear side) .

After the data of the image P ₃ is generated by the image combining unit 22, data of the image P ₄ is generated from the data of the image P ₃ and the image P _1. In this embodiment, among the two of the object displayed on the image P _1, the contour portion of the subject S _B of the contour portion of the subject S _F which is located on the front side while being emphasized, it is located on the rear side Will be blurred. The degree of enhancement and blur, blur width difference [Delta] W _B, is determined according to the amount of [Delta] W _F.
Although the data of the image P ₃ and the image P ₂ can also generate the data of the image P _4, since the image P ₂ has a large degree of blur than the image P _1, it is preferably used an image P _1.

Thereafter, the monitor 5 receives data of the image P ₄ from the image synthesizing unit 22 displays an image P ₄ on the screen. Then, the viewer X, the degree of emphasis of the contour portion of the image P ₄ on the displayed object S _F and the subject S _B, and the degree of blurring, the subject S _F and the subject S _B is how far from the focal point, respectively guess whether there's, it is possible to identify the context of the subject S _F and the subject S _B.

  The image composition unit 22 may express the subject's context by a method other than the enhancement and blurring of the contour portion. In this embodiment, the subject's context is represented by changing the color of the contour portion.

  FIG. 5A is an example of a graph used for associating the blur width difference ΔW of the subject with the color of the contour portion to be selected. Various methods are known for expressing colors numerically. In this embodiment, an HSV space in which colors are expressed by three elements of hue, saturation, and brightness is shown. Use. When the hue is changed from 0 ° to 360 ° while keeping the saturation and lightness at the maximum values, the color gradually changes from red → yellowish green → light blue → purple.

Image synthesizing unit 22 according to this embodiment, the image P _{3 (Fig.} 4 (C) refer) from each subject blur width difference [Delta] W _F, as well as identify the [Delta] W _B, with reference to the correspondence shown in FIG. 5 (A) Te, blur width difference [Delta] W _F, determines the color corresponding to each of the [Delta] W _B. In this embodiment, the blur width difference [Delta] W _F, aqua is selected as the color of the outline of the object S _F. Further, from the blur width difference [Delta] W _B, purple is selected as the color of the outline of the object S _B.
Thereafter, the image combining unit 22, together with coloring the contour portion of the subject S _F light blue in the image P _1, the data of the image P ₅ of the contour portion was colored purple subject S _{B (see} FIG. 5 (B)) Generate. Then, the image P ₅ is displayed on the screen of the monitor 5.

As mentioned above, although preferable embodiment of the radiation imaging device which concerns on this invention was described, this invention is not limited to the said structure.
For example, in the radiation imaging apparatus shown in FIG. 2, two filaments 10 a and 10 b connected in series and a switching unit 14 are provided as means for switching the focal dimension. The dimensions may be switched.

Further, a predetermined interval (e.g., 1/15 seconds) captured per a projected image due to small focus (image P ₁₎ of the projected image with a large focus (image P ₂₎ in each high-speed, image processing a captured image The image P ₄ or P ₅ may be generated by sequentially processing in the unit 4. As a result, it is possible to handle the imaging result of the moving subject S that is continuously captured as a moving image.

It is a schematic diagram which shows the basic principle of the radiation imaging device which concerns on this invention. 1 is a block diagram of a radiation imaging apparatus according to the present invention. 6 is a schematic diagram illustrating a positional relationship between two subjects imaged in Embodiments 1 and 2. FIG. 3A and 3B are images obtained when the subject illustrated in FIG. 3 is captured by the radiation imaging apparatus according to the first embodiment, where FIG. 3A is a projection image at a small focus, FIG. 3B is a projection image at a large focus, and FIG. ) Is an image obtained by comparing projection images at the time of small focus and large focus, and (D) is a processed image displayed on the monitor. FIG. 10 is a diagram according to the second embodiment, where (A) is a graph showing the relationship between the color of a contour portion and a difference in blur width, and (B) is an image after processing displayed on a monitor. It is a block diagram of the conventional radiation imaging device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support stand 2 Radiation irradiation part 3 Radiation detection part 4 Image processing part 5 Monitor 6 Focus switching control part 10a First filament 10b Second filament 11 Target 12 High voltage power supply 13 Filament power supply 14 Switching part 20 Storage part 20a First storage part 20b Second storage unit 21 Comparison unit 22 Image composition unit 30R Shutter (right eye)
30L shutter (left eye)
31 Support stand 32R Radiation irradiation part (right eye)
32L Radiation irradiation part (left eye)
33 Radiation detection unit 34 Storage unit 35 Left / right switching unit 36 Monitor F Focus f Focus size S Subject W Blur width (degree of blur)
ΔW Blur width difference X Observer

Claims (3)

A radiation irradiating unit disposed on one side of the subject and irradiating the subject with radiation having a predetermined focus, and a radiation disposed on the opposite side of the radiation irradiating unit with respect to the subject and transmitted through the subject A radiation imaging apparatus comprising: a radiation detection unit that detects a projection image of the subject and an image processing unit that appropriately processes the projection image;
The radiation irradiator includes means for switching the focal point to at least a first focal point and a second focal point having a size larger than the first focal point,
The radiation detection unit acquires a first image that is the projection image when the first focus is selected and a second image that is the projection image when the second focus is selected,
The image processing unit specifies a difference between the degree of blur of the subject in the first image and the degree of blur of the subject in the second image from the difference between the second image and the first image. A third image is generated by performing image processing according to the difference in the degree of blur on the subject portion of one image or the second image,
A radiation imaging apparatus, wherein a distance between the radiation irradiation unit and the subject can be estimated from the third image.   The radiation imaging apparatus according to claim 1, wherein the image processing increases a degree of blurring of a contour portion of the subject as the distance between the radiation irradiation unit and the subject increases. .   The radiographic imaging according to claim 1, wherein the image processing is to color a contour portion of the subject using a color selected according to a distance between the radiation irradiating unit and the subject. apparatus.

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