U.S. patent application number 13/413022 was filed with the patent office on 2012-06-28 for radiation imaging apparatus.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Tetsuo Watanabe.
Application Number | 20120163555 13/413022 |
Document ID | / |
Family ID | 42826187 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120163555 |
Kind Code |
A1 |
Watanabe; Tetsuo |
June 28, 2012 |
RADIATION IMAGING APPARATUS
Abstract
A radiation imaging apparatus comprising a detection unit for
detecting a radiation distribution transmitted through an object,
an imaging unit which includes the detection unit, and a grid for
suppressing scattered light which is detachably mounted on an
outside of the imaging unit, wherein the imaging unit includes a
buffer member on a side surface facing a surface side which
radiation strikes, the grid includes a grid body placed on the
surface side which the radiation strikes, and a fixing unit for
fixing the grid body to the imaging unit, and sides constituting
the fixing unit include a side which does not protrude from an
outer shape of the imaging unit when viewed from the surface side
which the radiation strikes.
Inventors: |
Watanabe; Tetsuo;
(Utsunomiya-shi, JP) |
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
42826187 |
Appl. No.: |
13/413022 |
Filed: |
March 6, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12725544 |
Mar 17, 2010 |
8160207 |
|
|
13413022 |
|
|
|
|
Current U.S.
Class: |
378/154 |
Current CPC
Class: |
A61B 6/501 20130101;
A61B 6/06 20130101; G03B 42/04 20130101; A61B 6/4233 20130101; A61B
6/4291 20130101 |
Class at
Publication: |
378/154 |
International
Class: |
G21K 1/10 20060101
G21K001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 2, 2009 |
JP |
2009-090486 |
Claims
1. A radiation imaging apparatus comprising: a detection unit for
detecting a radiation distribution transmitted through an object;
an imaging unit which includes said detection unit; and a grid for
suppressing scattered light which is detachably mounted on an
outside of said imaging unit, wherein said imaging unit includes a
buffer member on a side surface facing a surface side which
radiation strikes, said grid includes a grid body placed on the
surface side which the radiation strikes, and a fixing unit for
fixing the grid body to said imaging unit, and sides constituting
the fixing unit include a side which does not protrude from an
outer shape of said imaging unit when viewed from the surface side
which the radiation strikes.
Description
RELATED APPLICATIONS
[0001] The present application is a continuation of application
Ser. No. 12/725,544, filed Mar. 17, 2010. The present application
claims benefit of parent application Ser. No. 12/725,544 under 35
U.S.C. .sctn.120, and claims priority benefit under 35 U.S.C.
.sctn.119 of Japanese Patent Application 2009-090486, filed Apr. 2,
2009. The entire contents of each of the mentioned prior
applications are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a radiation imaging
apparatus using a portable solid-state imaging device configured to
allow a grid to be mounted outside the housing.
[0004] 2. Description of the Related Art
[0005] Conventionally, apparatuses which obtain radiographic images
of objects by irradiating the objects with radiation and detecting
the intensity distributions of radiation transmitted through the
objects have been widely and generally used in the fields of
industrial nondestructive testing and medical diagnosis. As a
general method for such radiography, a film/screen method using
radiation is available. This is the method of performing
radiography by using a combination of a photosensitive film and a
fluorescent having sensitivity to radiation.
[0006] In this method, rare-earth fluorescent sheets which emit
light upon application of radiation are held in tight contact with
the two surfaces of a photosensitive film. The fluorescent converts
radiation transmitted through an object into visible light. The
method then develops, by chemical treatment, the latent image
formed on the photosensitive film by making it capture this visible
light, thereby visualizing the image.
[0007] The recent advances in digital technology have popularized
the scheme of obtaining high-quality radiographic images by
converting radiographic images into electrical signals, performing
image processing for the obtained electrical signals, and then
reproducing the resultant information as visible images on a CRT or
the like. As such a method, there has been proposed a radiographic
image recording/reproduction system which temporarily stores a
transmission image of radiation as a latent image in a fluorescent,
photoelectrically reads out the latent image by irradiating the
fluorescent with exciting light such as a laser beam, and then
outputs the readout image as a visible image. In addition, with the
recent advances in semiconductor process technology, there has been
developed an apparatus for capturing a radiographic image in the
same manner as described above by using a semiconductor sensor.
[0008] These systems have very wide dynamic ranges as compared with
conventional radiographic systems using photosensitive films, and
can obtain radiographic images which are robust against the
influences of variations in the amount of radiation exposure. At
the same time, unlike the conventional photosensitive film scheme,
this method need not perform any chemical treatment and can
instantly obtain an output image.
[0009] FIG. 7 is a view showing the arrangement of a radiation
imaging system using the above semiconductor sensor. A radiation
imaging apparatus 103 mounted on a radiographic stand 106 includes
a solid-state imaging device 104 having a detection surface on
which a plurality of photoelectric conversion elements are
two-dimensionally arranged.
[0010] A radiation generator (X-ray tube) 101 emits radiation to
irradiate an object 102. The solid-state imaging device 104 then
images the radiation transmitted through the object 102, and
converts it into visible light through the fluorescent. A control
unit 107 reads out the electrical signal output from the
solid-state imaging device 104, performs digital image processing
for the signal, and then displays the resultant information as a
radiographic image of the object 102 on a monitor 108.
[0011] The radiation imaging apparatus 103 as an imaging unit
incorporates an anti-scatter grid (to be referred to as a grid
hereinafter) 105. The grid is designed to remove scattered X-rays
generated inside the object (e.g., a human body) 102 upon X-ray
irradiation, and is used to improve the contrast of an X-ray image.
This apparatus performs radiography with the grid 105 being
disposed between the X-ray tube 101 and a detector such as a film.
Such grids are defined as JIS Z 4910 anti-scatter grids, which will
be briefly described below.
[0012] FIG. 8 is a schematic sectional view of the grid described
above. X-rays are applied from a direction A on the left side of
FIG. 8. The grid is formed by alternately stacking foils 201 made
of a material having a high X-ray absorptance and intermediate
materials 202 having a low X-ray absorptance. In general, lead is
used for the foils 201 having a high absorptance, and aluminum,
paper, wood, synthetic resin, carbon fiber reinforced resin, or the
like is used for the intermediate materials 202 having a low X-ray
absorptance. The outer surface of this multilayered structure is
covered by, for example, an aluminum or carbon fiber reinforced
resin cover.
[0013] In many cases, the above grid is a focused grid including a
foil represented by a foil 201a which is located at a central
portion immediately below the X-ray source and is perpendicular to
the cover and foils 201b which gradually tilt in the direction of
the light source toward the fringes. When a focused grid is to be
used, it is necessary to perform radiography upon adjusting the
distance between the grid and the light source and their centers. A
grid without any tilting of foils is also available, which is
called a parallel grid. Such grids differ in the property of
attenuating transmitted X-rays depending on the density or
geometrical shape of foils. A grid with optimal specifications is
selected in accordance with radiography. In particular, the
solid-state imaging device 104 described above is generally
selected so as to prevent the pixel size from interfering with the
intervals between grid foils in terms of frequency.
[0014] An imaging apparatus of this type has been installed and
used in a radiation room. Recently, a portable imaging apparatus
(also called an electronic cassette) has also been provided to
allow quicker radiography of regions in a wider range.
[0015] Such an electronic cassette is required to be low in profile
and lightweight and have high mechanical strength. In cassette
radiography, a person as an object may be rested on the cassette.
In addition, since the electronic cassette is portable, a shock may
act on the cassette if it is dropped or collides with something. As
compared with conventional stationary imaging units, therefore, it
is necessary to greatly improve the resistance of such electronic
cassettes in terms of mechanical strength.
[0016] A cassette can be applied to various regions, and hence the
grid is preferably configured to be easily attached/detached
depending on a region to be radiographed. Therefore, a grid which
can be mounted outside an imaging unit has been proposed as
disclosed in Japanese Patent Laid-Open No. 2004-177251. This grid
is mounted on a metal frame component to secure its mechanical
strength.
[0017] As a grid mounted outside an imaging unit like that
described above, a grid having the following characteristics has
been provided. The first characteristic is that a metal frame
member is mounted on the grid body to protect it in terms of
mechanical strength. The second characteristic is associated with
the pixel array of the imaging unit and the relative angle of the
grid lattice.
[0018] Unlike film radiography, digital imaging has the merit of
reducing, by image processing, streaks appearing on an image when
the foils of the grid are captured on it. For this reason, the
relative angle preferably falls within the computational tolerance
of image processing. Therefore, in order to make the relative angle
fall within the tolerance range, the grid is mounted on the imaging
unit with a side wall being provided on a frame member for
positional restriction for the imaging unit. In addition, some
grids have a buffer member mounted on a side wall to prevent the
operator from being injured if the grid is accidentally dropped or
to prevent the grid from being damaged during transport.
[0019] Consider a case in which a portable X-ray imaging apparatus
111 is used to radiograph a side surface of a head portion 110 on a
table 114, as shown in FIG. 9. In this case, since a distance L
from the outer shape of a grid fixing frame 113 to an effective
imaging area 112 of the imaging unit 111 is large, it is necessary
to use a tool for applying some correction for an offset relative
to an object. That is, such radiography accompanies cumbersome
operation.
[0020] Studies have been focused on the imaging unit to meet the
requirement for a reduction in weight. In practice, however, it is
necessary to implement weight reduction, including a reduction in
the weight of the grid.
SUMMARY OF THE INVENTION
[0021] The present invention provides a radiation imaging apparatus
including a grid unit which makes improvements in the distance to
an effective imaging area and the mass, which contradict the
implementation of required relative angle restriction, the
securement of mechanical strength, and protection against a
shock.
[0022] According to one aspect of embodiments, the present
invention relates to a radiation imaging apparatus comprising a
detection unit for detecting a radiation distribution transmitted
through an object, an imaging unit which includes the detection
unit, and a grid for suppressing scattered light which is
detachably mounted on an outside of the imaging unit, wherein the
imaging unit includes a buffer member on a side surface facing a
surface side which radiation strikes, the grid includes a grid body
placed on the surface side which the radiation strikes, and a
fixing unit for fixing the grid body to the imaging unit, and sides
constituting the fixing unit include a side which does not protrude
from an outer shape of the imaging unit when viewed from the
surface side which the radiation strikes.
[0023] Further features of the present invention will become
apparent from the following description of exemplary embodiments
(with reference to the attached drawings).
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a front view of a radiation imaging unit according
to the first embodiment;
[0025] FIG. 2 is a front view showing the imaging unit according to
the first embodiment when a grid unit is mounted on it;
[0026] FIG. 3 is a side sectional view taken along a line A-A of
the imaging unit according to the first embodiment with the grid
unit being mounted on it;
[0027] FIG. 4 is a side sectional view taken along a line B-B of
the imaging unit according to the first embodiment with the grid
unit being mounted on it;
[0028] FIG. 5 is a front view showing an imaging unit according to
the second embodiment when a grid unit is mounted on it;
[0029] FIG. 6 is a front view showing an imaging unit according to
the third embodiment when a grid unit is mounted on it;
[0030] FIG. 7 is a view showing the arrangement of a conventional
radiation imaging system;
[0031] FIG. 8 is a view for explaining a grid; and
[0032] FIG. 9 is a view for explaining how a head portion is placed
in radiography of a side surface of the head portion.
DESCRIPTION OF THE EMBODIMENTS
[0033] The embodiments of the present invention will be described
in detail with reference to the accompanying drawings.
[0034] FIGS. 1 to 4 show an X-ray imaging apparatus according to an
embodiment of the present invention. FIG. 1 is a front view showing
an imaging unit alone when viewed from the X-ray incident surface.
FIG. 2 is a front view showing the imaging unit when a grid unit is
mounted on it. Referring to FIG. 2, reference numeral 1 denotes an
imaging unit; and 10, an anti-scatter grid unit.
[0035] FIG. 3 is a side sectional view taken along a line A-A in
FIG. 2. FIG. 4 is a side sectional view taken along a line B-B in
FIG. 2.
[0036] FIG. 1 is a front view showing the radiation imaging unit 1
alone when viewed from the X-ray incident surface side. An X-ray
detection unit which receives X-rays and detects a radiation
distribution is rectangular. A housing lid 2b is placed on the
X-ray incident surface side so as to cover an image-receiving area.
The housing lid 2b is made of a material having a high X-ray
transmittance. The housing lid 2b is combined with a housing body
2a to form a closed type housing 2 having a rectangular shape
(almost a quadrangle).
[0037] The radiation imaging unit 1 described above is used singly
as a cassette or used in combination with various gantries.
Requirements for transportation in changing the state of use are
that the imaging unit 1 is lightweight, and has mechanical strength
sufficient to maintain functionality even if it is dropped. In
addition, when the imaging unit 1 is to be used as a cassette, the
unit must be made low in profile to prevent a person as an object
from feeling pain even if the unit is placed under him/her, and
needs to have mechanical strength high enough to allow him/her to
directly rest upon it.
[0038] For this purpose, a material such as aluminum or magnesium
is used for the housing body 2a to achieve a reduction in weight.
In addition, to prevent accidents during transportation like those
described above, the imaging unit 1 has a handle and a buffer
function. The imaging unit 1 has a hole 9 as a handle which extends
through part of the housing. This allows stable gripping of the
imaging unit 1 during transportation. A buffer member 8 is placed
around the side surfaces of the imaging unit 1 when viewed from the
X-ray irradiation surface side.
[0039] The buffer member 8 is placed on the imaging unit 1 as shown
in FIG. 1 because the three sides other than one side (near the
handle) where the handle is formed tend to sustain damage due to
collisions with other objects or due to dropping when the operator
carries the unit while gripping the handle. The buffer member 8 is
made of a shock absorbing material such as rubber or an elastomer,
and is aimed at protecting an operator as well as other people from
injury to themselves as well as at reducing the shock absorbed by
the imaging unit 1.
[0040] The imaging unit 1 described above is used in combination
with a detachable grid for suppressing scattered light to improve
the contrast of an X-ray image by removing scattered X-rays
generated inside an object (e.g., a human body) upon X-ray
irradiation. Since grids having different X-ray shielding
characteristics are selectively used in accordance with the region
to be radiographed, the grid unit is designed to be externally
attached/detached to/from the housing 2 so as to be easily
attached/detached to/from the imaging unit, as shown in FIG. 2.
[0041] Referring to the side sectional view shown in FIG. 3, a
metal base 4 is fixed in the housing 2 through a support portion 3,
and an X-ray image detection panel 5 formed by stacking a substrate
5a, photoelectric conversion elements 5b, and a fluorescent plate
5c is placed on the base 4. As the substrate 5a, a glass plate is
often used because, for example, it must not have any chemical
action with a semiconductor element and needs to endure the
semiconductor process temperature and have dimensional
stability.
[0042] The photoelectric conversion elements 5b are formed on the
substrate 5a in a two-dimensional array by a semiconductor process.
The fluorescent plate 5c used is one that is formed by coating a
resin plate with a metal compound fluorescent. They are integrated
with each other with an adhesive. In addition, the photoelectric
conversion elements 5b are connected, through a flexible circuit
board 6 connected to their side surfaces, to a circuit board 7
which is placed on the lower surface of the base 4 and on which
electronic parts for processing electrical signals having undergone
photoelectric conversion are mounted. The circuit board 7 is
connected to an external control unit (not shown) to, for example,
supply power and transfer signals.
[0043] The radiation imaging unit 1 described above can perform
radiography by being used in combination with an X-ray tube which
emits X-rays. When the X-rays emitted by the X-ray tube positioned
above the imaging unit 1 are transmitted through an object and
strike the radiation imaging unit 1, the fluorescent plate 5c of
the X-ray image detection panel 5 emits light. The
two-dimensionally arrayed photoelectric conversion elements 5b
convert the light into electrical signals, thereby obtaining a
digital image. This digital image is further transferred to the
external control unit. This allows the operator to observe the
image on a monitor (not shown) in real time.
[0044] The grid unit 10 includes a grid body 11 and a metal frame
12. As described above, the grid body 11 has a layer structure
constituted by an X-ray shield member and an intermediate material
having small X-ray absorption, and hence is low in mechanical
strength. The grid body 11 is therefore attached with the frame 12
as a reinforced frame which has an X-ray transmission opening
portion 12a. The grid body 11 is held on the surface of the imaging
unit 1 on the incident surface side in tight contact with it.
[0045] The frame 12 shown in FIG. 3 has a cross-section in a
direction parallel to the side having the handle. This frame has
two side portions 12b which are bent by the thickness of the grid.
This shape can make the edge of the frame end portion difficult to
come into contact with an object and can increase the mechanical
strength of the frame 12, as compared with the simple planar shape
like that denoted by reference symbol E in FIG. 3. In addition,
this frame can achieve a great reduction in weight as compared with
a conventional frame covering the entire side surfaces.
[0046] Furthermore, the distal ends of the bent portions 12b do not
protrude outside the buffer member 8 on the side surfaces of the
imaging unit. This shape allows the buffer member 8 of the imaging
unit 1, which is placed outside, to receive a shock first, thus
reducing the shock directly acting on the grid frame 12. Even if
the grid unit 10 is attached to the imaging unit 1, the distance
from the outermost shape to the effective imaging area does not
change. This makes it possible to perform positioning in the same
manner and eliminate the necessity to use any tool to newly correct
an offset relative to an object.
[0047] A means for attaching the grid unit 10 to the imaging unit 1
will be described with reference to FIG. 4. The frame 12 is bent in
an almost U shape to have bent portions 12c and 12d so as to hold,
between them, the side having the handle and its opposite side. A
stepped portion 2c is formed on the housing 2 so as to lock a bent
portion 12e of the frame. The frame 12 is mounted on the housing 2
while a side surface wall 2d of the stepped portion 2c restricts
the movement of the frame 12 in the horizontal direction (the
vertical direction in FIG. 4).
[0048] On the other hand, a stepped portion is also provided on the
side on the handle side so as to lock a hook 13d of a slide member
13 provided on the bent portion 12c of the frame 12. A guide member
13c is mounted on the slide member 13 so as to be slidable on guide
grooves 12f formed in the bent portion 12c. Simple operation can
detachably mount the grid unit 10 on the imaging unit 1.
[0049] This lock mechanism allows to safely carry the imaging unit
1 even while the grid unit 10 is mounted on it. The bent portion
12d of the frame 12 and the slide member 13 hold the imaging unit 1
between them. This structure therefore restricts the rotation of
the grid unit 10 so as to make the relative angle of the grid unit
10 with respect to the imaging unit 1 fall within a predetermined
angle.
[0050] FIG. 5 shows an X-ray imaging apparatus according to another
embodiment of the present invention, which is a modification of the
above embodiment. According to the above embodiment, the frame of
the grid unit is formed to expose the buffer member provided on the
side surfaces of the imaging unit on the two sides perpendicular to
the side where the handle is formed, and the grip unit defines the
outermost shape on the side on which the handle is formed and its
opposite side. If an imaging area is rectangular, it is necessary
to select the portrait orientation or the landscape orientation as
the suitable posture of the imaging unit. If radiography is
performed with the long side being the bottom, the distance from
the outermost shape to the effective imaging area undesirably
increases.
[0051] In order to cope with this problem, in this embodiment, a
buffer member is partly notched to be divided into parts 22, 23,
and 24. Bent portions 32a and 32b for locking which are provided on
a frame member 32 on which a grid 31 is to be mounted are placed in
the gaps between the respective parts. With this arrangement, the
buffer members 22, 23, and 24 of an imaging unit 21 on the sides
other than the side where a handle 29 is formed each define the
outermost shape. That is, the three sides have the same effect as
that described in the first embodiment. Setting the width of the
bent portions 32a and 32b to reduce backlash in the gaps between
the respective parts of the buffer member can manage the relative
position accuracy of the grid 31 with respect to the imaging unit
21 within a predetermined range.
[0052] FIG. 6 shows an X-ray imaging apparatus according to still
another embodiment of the present invention, which is a
modification of the embodiment shown in FIG. 5.
[0053] In the embodiment shown in FIG. 5, the outer shape of the
imaging unit defines the outermost shape at the three sides. In
this embodiment, however, a grid unit is formed such that the outer
shape of an imaging unit at the four sides including the side where
a handle is formed defines the outermost shape. Buffer members 42
and 43 are placed on the entire side surfaces of an imaging unit
41. This arrangement allows the effect of reducing shock even when
the imaging unit 41 is accidentally dropped as well as when a shock
acts on the imaging unit 41 while the operator is gripping the
handle and transporting the imaging unit 41. A grid unit 50
includes a lock portion 53 which is locked in a through hole 49
formed as a handle. The grid unit 50 is mounted on the imaging unit
41 by holding it with bent portions 52a and 52b and the lock
portion 53.
[0054] As described above, a grid frame 52 does not completely
protrude from the outer shape of the imaging unit 41 when viewed
from the incident surface side. This makes it possible to maintain
the same effect against a shock from the side surface direction as
that obtained when the imaging unit is used singly, even in a state
in which the grid unit 50 is mounted on the imaging unit.
[0055] The embodiments of the present invention have been described
above. Obviously, however, the present invention is not limited to
these embodiments. Various modifications and changes of the
embodiments can be made within the spirit and scope of the present
invention.
Other Embodiments
[0056] Aspects of the present invention can also be realized by a
computer of a system or apparatus (or devices such as a CPU or MPU)
that reads out and executes a program recorded on a memory device
to perform the functions of the above-described embodiment(s), and
by a method, the steps of which are performed by a computer of a
system or apparatus by, for example, reading out and executing a
program recorded on a memory device to perform the functions of the
above-described embodiment(s). For this purpose, the program is
provided to the computer for example via a network or from a
recording medium of various types serving as the memory device
(e.g., computer-readable medium).
[0057] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
* * * * *