JP4016580B2 - Radiography equipment - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention particularly relates to a radiographic apparatus that captures a medical radiographic image, and more particularly to a radiographic apparatus that can obtain a high-quality radiographic image.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in the medical field or the like, a radiation image is transferred onto a film using radiation that has passed through a subject. On the other hand, in recent years, an apparatus capable of directly capturing a radiographic image as a digital image has been developed. For example, in an apparatus that detects a radiation dose irradiated to a subject and obtains a radiographic image formed corresponding to the detected dose as an electrical signal, a method using a detector using a stimulable phosphor is disclosed in Japanese Patent Laid-Open No. Sho 55. A large number are disclosed in JP-A-12429, JP-A-63-189853, and the like.
[0003]
In such an apparatus, a stimulable phosphor is applied to a sheet-like substrate or fixed to the detector by vapor deposition or the like, and once irradiated with radiation transmitted through the subject, the stimulable phosphor absorbs the radiation. Thereafter, the stimulable phosphor is excited by light or thermal energy, and the radiation energy accumulated by the absorption of the stimulable phosphor is emitted as fluorescence, and the fluorescence is photoelectrically converted to an image. To get a signal.
[0004]
On the other hand, a charge corresponding to the intensity of the irradiated radiation is generated in the photoconductive layer, the generated charge is accumulated in a plurality of capacitors (pixels) arranged two-dimensionally, and the accumulated charges are taken out. A radiological image detection apparatus obtained by the above has been proposed. Such a radiation image forming apparatus is called a flat panel detector (FPD).
[0005]
As this FPD, as described in JP-A-7-6228, JP-A-9-90048, etc., a scintillator that emits fluorescence corresponding to the intensity of irradiated radiation, and fluorescence emitted from the scintillator directly or directly What is realized by a combination (area sensor) of a photoelectric conversion element such as a photodiode or CCD that receives light through a lens unit and performs photoelectric conversion is known. In addition, as disclosed in Japanese Patent Application Laid-Open No. 6-342098, a device that directly converts irradiated radiation into electric charge is also known.
[0006]
Since these devices can obtain image data as digital data, they have an advantage that image processing such as frequency enhancement processing and gradation conversion processing can be easily performed. Therefore, it is possible to easily create an image suitable for diagnosis under a wide range of imaging conditions, and therefore, it is used as a medical radiographic imaging device. Further, the FPD is particularly attracting attention because of its good image quality such as sharpness and the fact that the entire apparatus can be miniaturized.
[0007]
[Problems to be solved by the invention]
By the way, one problem when using the FPD is that manufacturing an area sensor large enough to cover the entire scintillator is costly. Therefore, instead of a large area sensor, a relatively small general-purpose area sensor that is relatively inexpensive is used in a two-dimensional array.
[0008]
However, in order to collect light from the scintillator for a small area sensor, the same number of lens units must be arranged. Here, in order to efficiently collect the light from the scintillator, the F number of the lens unit needs to be small (that is, the lens is bright), but the focal depth d on the area sensor side is
d = F × δ (δ is the minimum circle of confusion)
As the lens becomes smaller according to the F number, the focal depth becomes smaller as the lens becomes brighter, and image blurring tends to occur.
[0009]
Therefore, it is difficult to incorporate the light receiving surface of the area sensor within the focal depth of the lens unit only by strictly managing the dimensional tolerance of the component, and some focus adjustment work is required. However, as described above, after a plurality of lens units are arranged two-dimensionally, in order to perform focusing adjustment individually, the lens unit or area sensor is parallel to the optical axis direction from the back side, that is, from the area sensor side. It is necessary to move it, and the apparatus becomes complicated and adjustment takes time.
[0010]
On the other hand, the depth of field D on the scintillator side is D = d / M ² when the lateral magnification is M, according to optical theory. For example, when 1 <M, it becomes larger than d. Accordingly, the allowable error condition is actually relaxed. This indicates that if the distance between the lens unit and the area sensor is set and fixed by adjustment, the distance between these and the scintillator can be managed by the component accuracy.
[0011]
In view of the problems of the prior art, an object of the present invention is to provide a radiation imaging apparatus that can efficiently perform focus adjustment and can form a high-quality image.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the radiation imaging apparatus of the present invention provides:
Subject information obtained by the radiation generated by the radiation generating means passing through the subject is converted into visible light by a scintillator, and the converted visible light is passed through a plurality of lens units arranged two-dimensionally. , acquired as an electrical signal by an area sensor comprising a plurality of sensors disposed respectively in correspondence with the lens unit, the radiation imaging apparatus for forming a radiation image,
And characterized in that it has a frame to keep the lens sensor unit to the lens unit and the front xenon capacitors and focusable constructed plurality supports, the distance between the scintillator and the plurality of said lens-sensor unit constant To do.
[0013]
[Action]
The radiation imaging apparatus of the present invention converts subject information obtained by the radiation generated by the radiation generating means passing through the subject into visible light by a scintillator, and the converted visible light is two-dimensionally arranged. In a radiation imaging apparatus that forms a radiographic image by obtaining an electrical signal by an area sensor arranged in association with the lens unit via a plurality of lens units, the lens unit and the area sensor are integrated. Since it is configured as a lens / sensor unit, the distance between each lens unit and the corresponding area sensor can be easily managed, and the model of the main body of the device can be simplified. Can be formed. Here, the radiation includes α rays, β rays, positron rays, gamma rays, X rays, proton rays, deuteron rays, heavy ion rays, neutron rays, meson rays, etc., but not visible light. .
[0014]
Furthermore, since the distance between the lens unit and the area sensor is variable, for example, if they are integrated after adjusting the focus on an external jig in advance, the accuracy of the assembly will be sufficient for the subsequent assembly. It is possible to cover and prevent blurring of the image due to out of focus.
[0015]
In addition, it is preferable if there is a fixing means for fixing the lens unit to the lens / sensor unit.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to embodiments. In the present embodiment, a CCD sensor is used as the area sensor provided in the radiation image detector, but a C-Mos sensor can be used in the same manner. Further, the signal value of each pixel will be described below as being higher as the radiation dose is higher and lower as the radiation dose is lower.
[0017]
FIG. 1 is a schematic configuration diagram of a radiation imaging apparatus according to the present embodiment. In FIG. 1, X-rays generated by X-ray generation means 101, which is radiation generation means, pass through a subject 102, which is a human body, for example, thereby causing differences in X-ray absorption in structures such as bones and meat in the subject. As a result, the intensity varies from place to place. This X-ray is detected by the radiation image detector 103. The radiation image detector 103 outputs an electrical signal (image data) based on the received light intensity of X-rays. Based on such image data, a radiation image having a contrast (gradation) based on the subject structure is generated.
[0018]
The output image data is sent to the image processing unit 104 and subjected to processing such as gradation conversion and frequency enhancement. The image data relating to the processed image that has been processed is sent to the network 105 and displayed on the image diagnostic monitor 106 or printed by the imager 107 or the like for diagnosis.
[0019]
Next, an aspect of generating image data related to a radiographic image will be described. FIG. 2 is a diagram illustrating a configuration of the radiation image detector 103. The radiographic image detector 103 generates image data related to the radiographic image as follows.
[0020]
i) First, X-rays are received by the scintillator 103a. The scintillator 103a emits fluorescence with higher emission intensity as the intensity of received X-rays is higher.
ii) Light emitted by the scintillator 103a is imaged on a light receiving surface of a CCD sensor 103c arranged corresponding to each lens unit 103b via a plurality of lens units 103b arranged in a two-dimensional manner (array). The In the present embodiment, as will be described later, the lens unit 103b and the CCD sensor 103c integrally form a lens / sensor unit.
iii) The CCD sensor 103c photoelectrically converts the fluorescent light received on its light receiving surface and outputs it as an electrical signal.
iv) The electrical signal obtained from the CCD sensor 103c is constructed as digital image data in an image construction circuit 103d having position correction means 103da, saturation pixel detection means 103db, pixel interpolation means 103dc, and signal level correction means 103dd. A radiographic image can be obtained based on the above.
v) In the image construction circuit 103d, the position correction means 103da corrects the pixel position error due to the displacement of the CCD sensor 103c, the distortion of the lens unit 103b, and the like, and obtains an image using the plurality of CCD sensors 103c. In this case, partial images obtained from the individual CCD sensors 103c are synthesized.
vi) Further, the saturated pixel detecting unit 103db corrects the pixel saturated by direct X-ray incidence on the CCD sensor 103c, and the pixel interpolating unit 103dc applies to the pixel detected by the saturated pixel detecting unit 103db. Then, the signal value of the pixel is interpolated from the signal value of the pixel existing in the vicinity thereof.
vii) Finally, the signal level correcting means 103dd corrects signal level unevenness due to unevenness of the scintillator 103a, sensitivity variation between the CCD sensors 103c, and the like. After correction is performed by each of these correction means, image data is finally output from the radiation image detector 103.
[0021]
FIG. 3 is a perspective view showing the lens / sensor unit of the present embodiment. In FIG. 3A, a lens unit 103b including a lens group and a CCD sensor 103c are integrated via a lens support 110 serving as a fixing unit. More specifically, the rectangular thick plate-like lens support 110 has a circular opening 110a on one side and a rectangular opening 110b on the other side so as to communicate with the circular opening 110a. Yes. A sensor / lens unit 111 as shown in FIG. 3B can be obtained by inserting the lens unit 103b into the circular opening 110a and inserting the CCD sensor 103c into the rectangular opening 110b.
[0022]
The lens unit 103b can be attached to the lens support 110 by forming a female screw (not shown) in the back of the circular opening 110a, forming a male screw 103ba on the outer periphery of the insertion end of the lens unit 103b, and screwing both screws together. . At this time, the lens unit 103b can be positioned by screwing the screw 110d from the side of the lens support 110 and pressing the tip of the screw 110d against the side surface of the inserted lens unit 103b. For individual focus adjustment, the screw 110d is loosened and the lens unit 103b is rotated to appropriately move in the optical axis direction, and after confirming the focus in a state equivalent to the actual device, the screw 110d is tightened again. You can do it. The CCD sensor 103c may be attached using an adhesive.
[0023]
The lens unit 103b can be attached using an adhesive, but in this case, focus adjustment cannot be performed by moving the lens unit 103b. In such a case, it is conceivable that the distance between the lens unit 103b and the CCD sensor 103c is made variable by inserting a shim 112 between the rectangular opening 110b and the CCD sensor 103c, thereby adjusting the focus. .
[0024]
A plurality of sensor / lens units 111 are formed and individually adjusted in focus, and then inserted into a plurality of rectangular openings 113a formed two-dimensionally in the frame 113 as shown in FIG. . A scintillator 103 a is disposed on the opposite side of the frame 113. At this time, the stepped portion 110c formed on the outer periphery of the lens support 110 abuts against the edge of the opening 113 so that it does not penetrate further into the back, so that the scintillator 103a and the sensor lens unit 111 are The distance is kept constant. Since the depth of field D on the scintillator 103a side is relaxed in terms of the allowable error condition as described above, appropriate image formation can be achieved without sacrificing assembly by managing only the part manufacturing error. Can be secured.
[0025]
The inventors of the present invention produced a radiation image detector 103 in which the frame 113 has a size of 43 cm × 43 cm. In this apparatus, the focal length of the lens unit 103b was 8 mm, the lateral magnification was -1/6, the F number was 1.4, and the area sensor used was a 1/2 inch CCD. Here, if the minimum circle of confusion of the lens unit 103b is 0.01 mm, the depth of focus is about ± 0.014 mm, and the depth of field is ± 0.50 mm. The number of sensor / lens units 111 used was 12 × 16 = 196. According to the radiation image detector 103, it was confirmed that a sharp image having no deviation from the pin could be obtained from all the sensor / lens units 111.
[0026]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a radiation imaging apparatus that can perform focus adjustment efficiently and can form a high-quality image.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a radiation imaging apparatus according to an embodiment.
FIG. 2 is a diagram showing a configuration of a radiation image detector 103. FIG.
FIG. 3 is a perspective view showing a lens / sensor unit of the present embodiment.
[Explanation of symbols]
101 X-ray generation means 102 Subject 103 Radiation image detector 103a Scintillator 103b Lens unit 103c CCD sensor 103d Image construction circuit 104 Image processing unit 105 Network 106 Monitor 107 Imager 110 Lens support 111 Lens / sensor unit 113 Frame

Claims (2)

Subject information obtained by the radiation generated by the radiation generating means passing through the subject is converted into visible light by a scintillator, and the converted visible light is passed through a plurality of lens units arranged two-dimensionally. , acquired as an electrical signal by an area sensor comprising a plurality of sensors disposed respectively in correspondence with the lens unit, the radiation imaging apparatus for forming a radiation image,
And characterized in that it has a frame to keep the lens sensor unit to the lens unit and the front xenon capacitors and focusable constructed plurality supports, the distance between the scintillator and the plurality of said lens-sensor unit constant Radiography equipment. The radiation imaging apparatus according to claim 1, further comprising a fixing unit that supports the lens unit and the sensor so as to be adjustable in focus.

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