X-ray or gamma ray systems or devices – Beam control – Antiscatter grid
Reexamination Certificate
1999-08-30
2002-08-13
Dunn, Drew A. (Department: 2882)
X-ray or gamma ray systems or devices
Beam control
Antiscatter grid
C378S154000, C378S098800
Reexamination Certificate
active
06434218
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a radiation photographing apparatus for obtaining a radiation image of an object to which radiation such as X-rays is applied.
2. Related Background Art
The radiation photographing apparatus of this kind has heretofore been used in various fields and particularly, in radiation photographing directed to the medical diagnosis of human bodies and the non-destruction inspection of substances, a so-called radiation photographic method using a combination of an intensifying screen and radiation photographic film has been utilized. In the radiation photographing apparatus adopting this radiation photographic method, when radiation is transmitted through an object and is incident on the intensifying screen, a fluorescent material contained in the intensifying screen absorbs the incident radiation energy and emits fluorescence. Thereby, the radiation photographic film which is in close contact with the intensifying screen is sensitized and a radiation image appears as a visible image on the radiation photographic film.
Also, there has been devised a radiation image recording-reproducing system utilizing an accumulative fluorescent material. The accumulative fluorescent material accumulates part of radiation energy therein when the radiation is applied thereto, and produces accelerated emitted light conforming to the accumulated radiation energy when exciting light such as visible light is applied. In such a radiation image recording-reproducing system, the radiation image information of an object such as a human body is once recorded on an accumulative fluorescent material sheet and exciting light such as a laser beam is scanned on the accumulative fluorescent material sheet by image reading means to thereby produce accelerated emitted light. The accelerated emitted light is then photoelectrically read, and the radiation information of the object based on this read image signal is outputted as a visible image to a recording material such as a photographic photosensitive material or a CRT or the like.
Also, a radiation image digital detector for digital-outputting a radiation image in real time is disclosed, for example, in Japanese Patent Application Laid-Open No. 8-116044. The manufacture of this radiation image digital detector has become possible by the advance of the semiconductor process technique, and it comprises a solid state photodetector and a scintillator laminated one upon the other. The solid state photodetector comprises solid state photodetection elements comprising transparent electrically conductive film and electrically conductive film and they are arranged in the form of a matrix at the opposite sides of amorphous semiconductor film on a substrate formed of quartz glass, and the scintillator converts the radiation into visible light.
The construction in which this radiation image digital detector outputs a digital image is very simple, and when the radiation transmitted through the object is incident on the radiation image digital detector, the scintillator converts the radiation into visible light, and the photoelectric converting portions of the solid state photodetection elements detect the visible light as an electrical signal. This electrical signal is read from each solid state photodetection element by a predetermined reading method, and is A/D-converted. Signal processing means processes the A/D-converted radiation image signal, whereafter image reproducing means such as a CRT reproduces it as a radiation image, which is used for diagnosis by a medical doctor. In this case, the signal processing means can also reproduce a radiation image excellent in contrast or sharpness.
Such a radiation image digital detector is a flat panel having a thickness of several millimeters and therefore can very easily contribute to making the radiation photographing apparatus thin and light in weight. For example,
FIG. 1
of the accompanying drawings shows a radiation photographing apparatus using a radiation image digital detector for upright photographing such as the simple photographing of the breast or the simple photographing of the abdomen, and the main body
2
of the apparatus is disposed forwardly of an X-ray generating portion
1
, and the main body
2
of the apparatus is supported by the movable portion
3
a
of a stand
3
. The main body
2
of the apparatus and a control portion
4
are connected together through a flexible cable
5
protected by a cover
5
a,
and the main body
2
of the apparatus is vertically moved in accordance with the height of an object and is fixed at an optimum position.
A grid
7
and an X-ray image receiving portion
8
are disposed in the housing
6
of the main body
2
of the apparatus in succession from the X-ray generating portion
1
side, and the X-ray image receiving portion
8
is comprised of a radiation image digital detector
9
and a reading circuit
10
. The grid
7
removes the scattered rays from an object, not shown, and the reading circuit
10
reads a signal from the radiation image digital detector
9
.
An image processing portion
12
and a power source portion
13
are disposed in the housing
11
of the control portion
4
, and a display portion
14
such as a monitor is connected to the image processing portion
12
. This display portion
14
is sometimes incorporated in the control portion
4
. The image processing portion
12
effects a filtering process such as the noise reduction or edge emphasis of a digital signal supplied from the reading circuit
10
, and the power source portion
13
supplies a power source to the radiation image digital detector
9
, the reading circuit
10
and the image processing portion
12
.
Sometimes an X-ray detector, not shown, is incorporated instead of the grid
7
, or is incorporated between the grid
7
and the X-ray image receiving portion
8
. This X-ray detector is generally called a phototimer and is connected to an X-ray automatic exposure control device, not shown, which is discretely installed. Since the exposure time of X-rays is automatically controlled by the X-ray automatic exposure control device even when the thickness or desired region of the object differs, an X-ray image receiving portion can always obtain an image of predetermined density. As a typical X-ray detector, there is known so-called photomultiplier using a photomultiplier tube, a semiconductor detector utilizing a semiconductor element, an ion chamber utilizing the electrolytic dissociation action of air by X-rays, or the like.
A radiation photographing apparatus which does not use the radiation image digital detector
9
is designed such that a cassette containing a sheet of radiation photographic film or an accumulative fluorescent material sheet therein is mounted on the X-ray image receiving portion
8
and X-rays are emitted from the X-ray generating portion
1
to thereby photograph the object, whereafter the cassette is taken out and is developed. In contrast, in a radiation photographing apparatus using the radiation image digital detector
9
, the cumbersome work of mounting the cassette and taking out and developing the cassette can be eliminated and moreover, a photographed image can be displayed on the display portion
14
immediately after photographing, and even rare re-photographing can be coped with in a moment.
In contrast, when the above-described radiation photographing apparatus is used for the upright photographing of the breast or the abdomen, it is necessary to use the grid
7
to remove scattered rays, but when the radiation photographing apparatus is used for the photographing of a body portion such as the head or the limb, it is often the case that the grid
7
is not used because scattered rays are relatively few. Also, a good image free of spatial blur can be obtained if the radiation photographic film, the accumulative fluorescent material sheet and the radiation image digital detector
9
are brought into the closest possible contact with the object.
Therefore, a radiation photographing a
Canon Kabushiki Kaisha
Dunn Drew A.
Fitzpatrick ,Cella, Harper & Scinto
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