U.S. patent application number 12/418309 was filed with the patent office on 2009-09-10 for x-ray ct apparatus collimator, method of manufacturing the x-ray ct apparatus collimator, and x-ray ct apparatus.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Ryuhachiro Doji, Hideki Ide, Kenji Igarashi, Machiko Iso, Tsuguo Kishi, Masaru Kitamura, Yasutada Nakagawa, Shuya Nambu, Yasuo Saito, Shigeru Sakuta, Masaharu Shimizu, Akiji Wakabayashi, Katsuya Yamada, Masahiko Yamazaki.
Application Number | 20090225955 12/418309 |
Document ID | / |
Family ID | 36698842 |
Filed Date | 2009-09-10 |
United States Patent
Application |
20090225955 |
Kind Code |
A1 |
Igarashi; Kenji ; et
al. |
September 10, 2009 |
X-RAY CT APPARATUS COLLIMATOR, METHOD OF MANUFACTURING THE X-RAY CT
APPARATUS COLLIMATOR, AND X-RAY CT APPARATUS
Abstract
The angle of each collimator plate with respect to an X-ray
focal point is determined by fitting the collimator plate in
grooves formed in upper and lower supports each having an integral
structure. In addition, the warpage of each collimator plate is
corrected and its flatness is maintained by fitting the periphery
of the collimator plate which is on the X-ray detector side in a
corresponding groove of an abutment plate provided on the X-ray
detection surface side of the upper and lower supports.
Furthermore, each collimator plate is supported by the
corresponding grooves of the upper and lower supports and the
corresponding groove of the abutment plate at least three
sides.
Inventors: |
Igarashi; Kenji;
(Utsunomiya-shi, JP) ; Shimizu; Masaharu;
(Nasushiobara-shi, JP) ; Wakabayashi; Akiji;
(Otawara-shi, JP) ; Saito; Yasuo;
(Nasushiobara-shi, JP) ; Iso; Machiko;
(Nasushiobara-shi, JP) ; Kishi; Tsuguo;
(Yokohama-shi, JP) ; Sakuta; Shigeru;
(Urayasu-shi, JP) ; Kitamura; Masaru;
(Yokohama-shi, JP) ; Doji; Ryuhachiro;
(Yokohama-shi, JP) ; Ide; Hideki; (Yokohama-shi,
JP) ; Nambu; Shuya; (Nasushiobara-shi, JP) ;
Yamazaki; Masahiko; (Utsunomiya-shi, JP) ; Yamada;
Katsuya; (Kamakura-shi, JP) ; Nakagawa; Yasutada;
(Yokohama-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Minato-ku
JP
TOSHIBA MEDICAL SYSTEMS CORPORATION
Otawara-Shi
JP
|
Family ID: |
36698842 |
Appl. No.: |
12/418309 |
Filed: |
April 3, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11403813 |
Apr 14, 2006 |
7526070 |
|
|
12418309 |
|
|
|
|
Current U.S.
Class: |
378/149 |
Current CPC
Class: |
A61B 6/032 20130101;
G21K 1/025 20130101 |
Class at
Publication: |
378/149 |
International
Class: |
G21K 1/02 20060101
G21K001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 15, 2005 |
JP |
2005-118772 |
Claims
1. An X-ray computer tomography apparatus comprising: an X-ray
exposing unit which exposes X-rays; an X-ray detection unit which
is placed to face the X-ray exposing unit through a subject and
detects X-rays incident to a detection surface; a collimator unit
which is placed on the X-ray incident side of an X-ray detector to
remove scattered X-rays and includes a plurality of collimator
plates and a support unit, the plurality of collimator plates being
arranged along a predetermined direction, and the support unit
supporting at least three sides of each of the collimator plates
such a manner that a surface of each of the collimator plates is
substantially parallel to an X-ray incident direction from the
X-ray exposing unit to the detection surface; wherein the support
unit includes: a first support member which includes a plurality of
first grooves provided along the predetermined direction, each of
the first grooves being formed along the X-ray incident direction;
a second support member which is placed parallel to the first
support unit and includes a plurality of second grooves provided
along the predetermined direction so as to correspond to said
plurality of first grooves, each of the second grooves being formed
along the X-ray incident direction; a third support member which
includes a plurality of third grooves for fitting of detection
surface side peripheries of the collimator plates fitted in the
first grooves and the second grooves, and is provided on the
detection surface side of the plurality of collimator plates; and
wherein the support unit includes the third support members which
are modularized.
2. An X-ray computer tomography apparatus according to claim 1,
wherein the support unit further comprises a fourth support member
which includes a plurality of fourth grooves for fitting of X-ray
exposing unit side peripheries of the collimator plates fitted in
the first grooves and the second grooves, and is provided on the
X-ray exposing unit side of the plurality of collimator plates.
3. An X-ray computer tomography apparatus according to claim 1,
wherein each of the third support members further includes a fifth
groove which form the third groove for inserting the collimator
plate between the neighboring the third support members when the
third support members are arrayed along the predetermined
direction.
4. An X-ray computer tomography apparatus according to claim 1,
wherein the support unit further comprises a fourth support member
which supports the plurality of the plates by pressing X-ray
exposing unit side peripheries of the collimator plates fitted in
the first grooves and the second grooves, and is provided on the
X-ray exposing unit side of the plurality of collimator plates.
5. An X-ray computer tomography apparatus according to claim 1,
wherein the support unit includes the third support members which
are modularized.
6. An X-ray computer tomography apparatus according to claim 1,
wherein each of the third support members further includes a fifth
groove which form the third groove between the neighboring the
third support members for inserting the collimator plate when the
third support members are arrayed along the predetermined
direction.
7. An X-ray computer tomography apparatus according to claim 1,
wherein the support unit further comprises a fourth support member
which includes a plurality of fourth grooves for fitting of X-ray
exposing unit side peripheries of the collimator plates fitted in
the first grooves and the second grooves, and is provided on the
X-ray exposing unit side of the plurality of collimator plates.
8. An X-ray computer tomography apparatus according to claim 1,
wherein each of the fourth support members further includes a sixth
groove which form the fourth groove between the neighboring the
fourth support members for inserting the collimator plate when the
fourth support members are arrayed along the predetermined
direction.
9. An X-ray computer tomography apparatus according to claim 1,
wherein the support unit further comprises a fourth support member
which supports the plurality of the plates by pressing the X-ray
exposing unit side peripheries of the collimator plates fitted in
the first grooves and the second grooves, are modularized and are
provided on the X-ray exposing unit side of the plurality of
collimator plates.
10. An X-ray computer tomography apparatus according to claim 1,
wherein the support unit further includes: a fifth support member
which includes a plurality of seventh grooves for fitting of the
X-ray exposing unit side peripheries of the collimator plates
fitted in the first grooves, and is provided on the X-ray exposing
unit side of the plurality of collimator plates; and a sixth
support member which includes a plurality of eighth grooves for
fitting of the X-ray exposing unit side peripheries of the
collimator plates fitted in the second grooves, and is provided on
the X-ray exposing unit side of the plurality of collimator
plates.
11. An X-ray computer tomography apparatus according to claim 1,
wherein the support unit further includes: a fifth support member
which supports the plurality of the plates by pressing the X-ray
exposing unit side peripheries of the collimator plates fitted in
the first grooves, and is provided on the X-ray exposing unit side
of the plurality of collimator plates and along the first
supporting member; and a sixth support member which supports the
plurality of the plates by pressing the X-ray exposing unit side
peripheries of the collimator plates fitted in the second grooves,
and is provided on the X-ray exposing unit side of the plurality of
collimator plates along the second supporting member.
12. An apparatus according to claim 1, further comprising a fourth
support unit which includes slits which support peripheries of the
collimator plates on the X-ray exposing unit side and allow the
collimator plates fitted in the first grooves and the second
grooves which face each other to pass through and is provided on
the X-ray exposing unit side of the collimator.
13. An apparatus according to claim 1, wherein the X-ray detection
unit includes an arcuated shape, and the collimator unit includes
the arcuated shape corresponding to the X-ray detection unit.
14. An apparatus according to claim 1, wherein a groove width on
the X-ray exposing unit side on which an opening portion for each
of said plurality of third grooves is formed is substantially not
less than a groove width on the X-ray detection unit side on which
an abutment surface for the collimator plate is formed.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application a divisional of application Ser. No.
11/403,813, filed Apr. 14, 2006, and is based upon and claims the
benefit of priority from prior Japanese Patent Application No.
2005-118772, filed Apr. 15, 2005, the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a collimator used for an
X-ray CT (Computer Tomography) apparatus, a method of manufacturing
the collimator, and an X-ray CT apparatus having the
collimator.
[0004] 2. Description of the Related Art
[0005] As is well known, an X-ray CT apparatus is designed to
obtain an image (tomographic image) by calculating (reconstructing)
the X-ray absorptance of tissue such as an organ as an index called
a CT value with reference to the X-ray absorptance of water on the
basis of the amount of X-rays absorbed by a subject.
[0006] This X-ray CT apparatus is provided with a collimator on,
for example, the X-ray incident side of an X-ray detector to
reshape the shape of an X-ray beam striking each X-ray detection
element and to remove scattered X-rays. FIG. 1A shows an example of
the arrangement of a conventional collimator having an integral
structure (to be referred to as an "integral collimator"
hereinafter). As shown in FIG. 1A, the integral collimator has
upper and lower arcuated supports arranged side by side in the
slice direction along the body axis of a subject. Pairs of upper
and lower grooves are formed in the upper and lower supports so as
to allow the insertion of collimator plates therein such that the
respective plates face an X-ray focal point (which is assumed to be
the emission point of an X-ray source). Flattened collimator plates
are inserted in these grooves. An adhesive is then applied to the
portions of the plates which are inserted in the grooves and is
cured, thereby forming a collimator as an integral structure. The
collimator plates are supported by the grooves of the upper and
lower supports, and reshape incident X-rays without degrading the
warpage of each plate owing to its rigidity.
[0007] Assume that such an integral collimator comprises, for
example, collimator plates each having a length of less than 100 mm
in the slide direction in an X-ray CT apparatus. In this case, if
flattening processing is performed for each collimator plate in
advance, a collimator with little warpage on the 20 .mu.m order can
be formed with only the rigidity of each collimator plate.
[0008] The recent trend is to develop X-ray CT apparatuses with
wider detection ranges in the slice direction. In an X-ray CT
apparatus having 256 rows of multi-slice detectors which has
currently been developed, the detection range in the slice
direction is assumed to be about four times that in existing X-ray
CT apparatuses. For this reason, according to the arrangement of a
conventional integral collimator, it is difficult to maintain the
flatness and warpage of each collimator plate with only the
rigidity of each collimator plate. As a consequence, when each
detector (detector unit) is to be mounted, alignment cannot be
performed, and the solid angle of an X-ray beam striking each X-ray
detection element cannot be properly limited, resulting in failure
to acquire an appropriate tomographic image.
[0009] In order to solve this problem, for example, as shown in
FIG. 1B, there has been proposed a collimator having a module
structure (to be referred to as a "module type collimator"
hereinafter) which covers about 20 channels of a detector. As shown
in FIG. 1B, a plurality of such module type collimators are
arranged to cover the entire detection surface of the X-ray
detector along the channel direction. The module type collimator
has front and rear supports, in each of which grooves in which
collimator plates are to be inserted are formed. These grooves are
formed in the front and rear supports at different pitches because
collimator plates need to face the X-ray focal point. By inserting
collimator plates in the pairs of grooves in the front and rear
supports, the collimator plates form an arrangement widening toward
the end. As a result, all the collimator plates are formed to face
the X-ray focal point.
[0010] Such a module type collimator is assembled while adjusting
the squareness with respect to an end face of each support or the
reference surface of the central plate, thereby forming a module
type collimator set at a correct position opposing the X-ray focal
point. It has been confirmed that in even a region where the
detection range of each collimator plate in the slice direction is
about 200 mm or more and hence it is difficult to flatten
collimator plates, warpage is corrected by inserting plates in the
grooves formed in the front and rear supports in the slice
direction, and a collimator which maintains flatness as in existing
collimators can be formed. As a consequence, alignment with the
detector can be done.
[0011] In the above module type collimator as well, for example,
the following problem arises.
[0012] In the module type collimator, factors that unstabilize the
mount surface of the detector module on which the collimator is
mounted cannot be eliminated. Even if, for example, a dust particle
on the 10 .mu.m order exists on the mount surface, the X-ray focal
point at the position about 10 .mu.m ahead of the dust particle is
enlarged and shifted. Therefore, steps are produced in continuity
that connects the X-ray focal point at the joint portions between
the module type collimators. As a consequence, when the polar
response characteristic, i.e., the X-ray foal point, shifts over
time, an impermissible unbalance amount, which cannot be neglected,
is produced in variation components of shadow on the detector,
resulting in the production of artifacts in an image.
BRIEF SUMMARY OF THE INVENTION
[0013] The present invention has been made in consideration of the
above situation, and has as its object to provide an X-ray CT
apparatus collimator, a method of manufacturing the collimator, and
an X-ray CT apparatus which can realize proper X-ray collimation by
maintaining the flatness of each collimator plate without losing
the continuity of the X-ray focal point.
[0014] According to an aspect of the present invention, there is
provided an X-ray CT apparatus which comprises: an X-ray exposing
unit which exposes X-rays; an X-ray detection unit which is placed
to face the X-ray exposing unit through a subject and detects
X-rays incident to a detection surface; and a collimator unit (50)
which is placed on the X-ray incident side of an X-ray detector to
remove scattered X-rays and includes a plurality of collimator
plates and a support unit, the plurality of collimator plates being
arranged along a predetermined direction, and the support unit
supporting at least three sides of each of the collimator plates
such a manner that a surface of each of the collimator plates is
substantially parallel to an X-ray incident direction from the
X-ray exposing unit to the detection surface.
[0015] According to another aspect of the present invention, there
is provided an X-ray CT apparatus collimator manufacturing method
of manufacturing a collimator which is used for an X-ray CT
apparatus comprising an X-ray exposing unit which exposes X-rays
and an X-ray detection unit which is placed to face the X-ray
exposing unit through a subject and detects X-rays striking a
detection surface, and is provided on the detection surface to
remove scattered X-rays, which comprises: assembling, by using side
surface members, a first support unit including a plurality of
first grooves formed along an X-ray incident direction from the
X-ray exposing unit to the detection surface and a second support
unit including a plurality of second grooves formed along the X-ray
incident direction from the X-ray exposing unit to the detection
surface so as to correspond to said plurality of first grooves;
fixing, to the detection surface side of the first support unit and
second support unit, a first support unit including a plurality of
third grooves for fitting of peripheries of the collimator plates
fitted in the first grooves and the second grooves which face each
other which are located on the detection surface side; fitting
collimator plates in the first grooves, the second grooves, and the
third grooves which face each other; and bonding said each
collimator plate to the first groove, the second groove, and the
third groove which correspond to said each collimator plate.
[0016] According to yet another aspect of the present invention,
there is provided an X-ray CT apparatus collimator manufacturing
method of manufacturing a collimator which is used for an X-ray CT
apparatus comprising an X-ray exposing unit which exposes X-rays
and an X-ray detection unit which is placed to face the X-ray
exposing unit through a subject and detects X-rays striking a
detection surface, and is provided on the detection surface to
remove scattered X-rays, which comprises: assembling, by using side
surface members, a first support unit including a plurality of
first grooves formed along an X-ray incident direction from the
X-ray exposing unit to the detection surface and a second support
unit including a plurality of second grooves formed along the X-ray
incident direction from the X-ray exposing unit to the detection
surface so as to correspond to said plurality of first grooves;
fixing, to the detection surface side of the first support unit and
second support unit, a first support unit including a plurality of
third grooves for fitting of peripheries of the collimator plates
fitted in the first grooves and the second grooves corresponding to
each other which are located on the detection surface side; fixing
the second support including slits which allow the collimator
plates fitted in the first grooves and the second grooves which
face each other to pass through the slits and support peripheries
of the collimator plates which are on an X-ray incident side to the
X-ray incident side of the first support unit and the second
support unit; fitting collimator plates in the first grooves, the
second grooves, and the third grooves which face each other upon
making the collimator plates pass through the slits; and bonding
the collimator plates to the first grooves, the second grooves, the
third grooves, and the slits which correspond to each other.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0017] FIG. 1A is a view for explaining the arrangement of a
conventional integral collimator;
[0018] FIG. 1B is a view for explaining the arrangement of a module
type collimator;
[0019] FIG. 2A is a block diagram showing the arrangement of an
X-ray CT apparatus 10 according to an embodiment;
[0020] FIG. 2B is a schematic view for explaining the layout of a
detector-side collimator 50;
[0021] FIG. 3 is a view for explaining the arrangement of the
detector-side collimator 50;
[0022] FIG. 4 is a view showing a form of supporting collimator
plates 504 by using grooves 505 of upper and lower supports 500 and
501 and an abutment plate 503;
[0023] FIG. 5 is a view for explaining a method of forming grooves
506 in the abutment plate 503;
[0024] FIG. 6 is a view for explaining the shape of each groove 506
in a manufacturing process for the abutment plate 503;
[0025] FIG. 7 is a view for explaining the shape of each groove 506
at the time of assembly of the abutment plate 503 to the upper and
lower supports 500 and 501;
[0026] FIG. 8 is a flowchart showing the flow of a manufacturing
process for the detector-side collimator 50;
[0027] FIG. 9 is a view showing the arrangement of a detector-side
collimator 50 according to the second embodiment;
[0028] FIG. 10A is a perspective view showing the detector-side
collimator 50 according to the second embodiment when viewed from
the inner arcuated side, FIG. 10B is a view for explaining a method
of manufacturing a guide plate 510, and FIG. 10C is a sectional
view of the flat guide plate 510 along slits 511;
[0029] FIG. 11 is a flowchart showing the flow of a manufacturing
process for the detector-side collimator 50;
[0030] FIG. 12 is a view showing the arrangement of a detector-side
collimator 50 possessed by an X-ray CT apparatus 10 according to
the third embodiment;
[0031] FIG. 13 is a view for explaining a method of forming grooves
521 of internal diameter cover 520;
[0032] FIG. 14 is a view for explaining a method of forming grooves
521 of internal diameter cover 520;
[0033] FIG. 15 is a view for explaining a method of forming grooves
521 of internal diameter cover 520;
[0034] FIG. 16 is a flow chart showing the flow of a manufacturing
process for the detector-side collimator 50 according to the third
embodiment;
[0035] FIG. 17 is a view showing the arrangement of the
detector-side collimator 50 according to a modified example of the
third embodiment;
[0036] FIG. 18 is a view showing the arrangement of the
detector-side collimator 50 according to a modified example of the
third embodiment;
[0037] FIG. 19 is a flow chart showing the flow of a manufacturing
process for the detector-side collimator 50 according to a modified
example of the third embodiment;
[0038] FIG. 20A is a view showing the arrangement of the
detector-side collimator 50 possessed by the X-ray CT apparatus 10
according to a fourth embodiment;
[0039] FIG. 20B is a view showing the arrangement of the
detector-side collimator 50 possessed by the X-ray CT apparatus 10
according to the fourth embodiment;
[0040] FIG. 20C is a view showing the arrangement of the
detector-side collimator 50 possessed by the X-ray CT apparatus 10
according to the fourth embodiment;
[0041] FIG. 20D is a view showing a modified example of the
detector-side collimator 50 (detail description of the joint part
between the neighboring internal diameter covers 530) according to
the fourth embodiment;
[0042] FIG. 21 is a flow chart showing the flow of a manufacturing
process for the detector-side collimator 50 according to the fourth
embodiment;
[0043] FIG. 22 is a view showing the arrangement of the
detector-side collimator 50 according to a modified example of the
fourth embodiment;
[0044] FIG. 23 is a flow chart showing the flow of a manufacturing
process for the detector-side collimator 50 according to a modified
example of the fourth embodiment;
[0045] FIG. 24 is a view showing the arrangement of the
detector-side collimator 50 possessed by the X-ray CT apparatus 10
according to a fifth embodiment;
[0046] FIG. 25A is a view showing an aspect of an abutment plate
540 of the detector-side collimator 50 according to the fifth
embodiment;
[0047] FIG. 25B is a view showing an aspect of an abutment plate
540 of the detector-side collimator 50 according to the fifth
embodiment;
[0048] FIG. 25C is a view showing an aspect of an abutment plate
540 of the detector-side collimator 50 according to the fifth
embodiment;
[0049] FIG. 26 is a flow chart showing the flow of a manufacturing
process for the detector-side collimator 50 according to the fifth
embodiment;
[0050] FIG. 27 is a view showing the arrangement of the
detector-side collimator 50 according to a modified example of the
fifth embodiment;
[0051] FIG. 28 is a flow chart showing the flow of a manufacturing
process for the detector-side collimator 50 according to the
modified example of the fifth embodiment;
[0052] FIG. 29 is a view showing the arrangement of the
detector-side collimator 50 possessed by the X-ray CT apparatus 10
according to a sixth embodiment;
[0053] FIG. 30 is a flow chart showing the flow of a manufacturing
process for the detector-side collimator 50 according to the sixth
embodiment;
[0054] FIG. 31 is a view showing the arrangement of the
detector-side collimator 50 according to a modified example of the
sixth embodiment;
[0055] FIG. 32 is a view showing the arrangement of the
detector-side collimator 50 according to the modified example of
the sixth embodiment;
[0056] FIG. 33 is a flow chart showing the flow of a manufacturing
process for the detector-side collimator 50 according to the
modified example of the sixth embodiment; and
[0057] FIG. 34 is a view showing the arrangement of the
detector-side collimator 50 according to another modified example
of the sixth embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0058] The first and second embodiments of the present invention
will be described below with reference to the views of the
accompanying drawing. Note that the same reference numerals in the
following description denote constituent elements having
substantially the same functions and arrangements, and a repetitive
description thereof will be made only when required.
First Embodiment
[0059] FIG. 2A is a block diagram showing the arrangement of an
X-ray CT apparatus 10 according to this embodiment. As shown in
FIG. 2A, the X-ray CT apparatus 10 comprises an imaging system A
and a processing/display system B. The constituent elements of
these systems will be described below.
[0060] The imaging system A acquires projection data (or raw data)
by applying X-rays to a subject and detecting X-rays transmitted
through the subject. Note that the imaging systems of X-ray CT
apparatuses include various types, e.g., a rotate/rotate type in
which an X-ray tube and a two-dimensional detector system rotate
together around a subject, a stationary/rotate type in which many
detection elements are arrayed in the form of a ring, and only an
X-ray tube rotates around a subject, and a type which
electronically moves the position of an X-ray source onto a target
by deflecting an electron beam. The present invention can be
applied to all types. In this case, the rotate/rotate type X-ray CT
apparatus, which is currently the mainstream, will be
exemplified.
[0061] As shown in FIG. 2A, the imaging system A has an X-ray tube
101, rotating ring 102, two-dimensional detector system 103, data
acquisition circuit (DAS) 104, non-contact data transmission device
105, gantry driving unit 107, slip ring 108, X-ray tube side
collimator (not shown in FIG. 2A), and X-ray detector-side
collimator (not shown in FIG. 1).
[0062] The X-ray tube 101 is a vacuum tube which generates X-rays,
and is amounted on the rotating ring 102. Power (a tube current or
tube voltage) required for the emission of X-rays is supplied from
a high voltage generator 109 to the X-ray tube 101 through the slip
ring 108. The X-ray tube 101 exposes X-rays to a subject placed in
an effective field of view FOV by accelerating electrons using the
applied high voltage and making them collide with the target.
[0063] An X-ray tube side collimator (not shown) which reshapes an
X-ray beam exposed from the X-ray tube 101 into a cone shape
(quadrangular pyramidal shape) or a fan beam shape is provided
between the X-ray tube 101 and the subject.
[0064] The two-dimensional detector system 103 is a detector system
which detects X-rays transmitted through the subject, and is
mounted on the rotating ring 102 to face the X-ray tube 101. In the
two-dimensional detector system 103, a plurality of detection
elements comprising combinations of scintillators and photodiodes
form a detection surface, and are arrayed in the form of a matrix
in the body axis direction of the subject (slice direction) and the
channel direction perpendicular thereto.
[0065] As schemes of converting incident X-rays into electric
charges in each detection element, a direct conversion scheme and
an indirect conversion scheme are available. This embodiment is not
limited to either of the schemes.
[0066] The X-ray tube 101 and the detector system 103 are mounted
on the rotating ring 102. The rotating ring 102 is driven by the
gantry driving unit 107 and rotates around the subject at a high
speed of one rotation per second.
[0067] The data acquisition circuit (DAS) 104 has a plurality of
data acquisition element rows on which DAS chips are arrayed. The
data acquisition circuit (DAS) 104 receives an enormous amount of
data (M.times.N-channel data per view will be referred to as "raw
data" hereinafter) associated with all M.times.N channels, which
are detected by the two-dimensional detector system 103, performs
amplification processing, A/D conversion processing, and the like,
and transmits the resultant data altogether to a data processing
unit on the fixed side through the non-contact data transmission
device 105 using optical communication.
[0068] The X-ray detector-side collimator reshapes an X-ray beam
striking each detection element of the two-dimensional detector
system 103, and is provided on the X-ray incident side of the
two-dimensional detector system 103.
[0069] The processing/display system B will be described next. The
processing/display system B comprises a pre-processing device 106,
the high voltage generator 109, a host controller 110, a storage
device 111, a reconstruction device 114, an input device 115, a
display device 116, an image processing unit 118, a network
communication device 119, and a data/control bus 300.
[0070] The pre-processing device 106 receives raw data from the DAS
104 through the non-contact data transmission device 105, and
executes sensitivity correction and X-ray intensity correction.
Note that the raw data pre-processed by the pre-processing device
106 will be referred to as "projection data".
[0071] The gantry driving unit 107 performs, for example, driving
control to rotate the X-ray tube 101 and the two-dimensional
detector system 103 together around a central axis parallel to the
body axis direction of the subject inserted in the opening for
diagnosis.
[0072] The high voltage generator 109 is a device which supplies
power necessary for the emission of X-rays to the X-ray tube 101
through the slip ring 108, and comprises a high voltage
transformer, filament heating converter, rectifier, high voltage
switch, and the like. The high voltage generator 109 applies a high
voltage to the X-ray tube 101 through the slip ring 108.
[0073] The host controller 110 performs overall control associated
with various kinds of processing, e.g., imaging processing, data
processing, and image processing.
[0074] The storage device 111 stores image data such as acquired
raw data, projection data, and CT image data.
[0075] The reconstruction device 114 generates reconstructed image
data corresponding to a predetermined number of slices by
performing reconstruction processing for projection data on the
basis of predetermined reconstruction parameters (e.g., a
reconstruction area size, a reconstruction matrix size, and a
threshold for the extraction of a region of interest). In general,
reconstruction processing includes cone beam reconstruction (the
Feldkamp method, ASSR method, and the like) and fan beam
reconstruction. Any technique can be implemented.
[0076] The input device 115 is a device which comprises a keyboard,
various kinds of switches, a mouse, and the like, and can input
various kinds of scan conditions such as a slice thickness and the
number of slices through an operator.
[0077] The image processing unit 118 performs image processing for
display, e.g., window conversion and RGB processing, for the
reconstructed image data generated by the reconstruction device
114, and outputs the resultant data to the display device 116. The
image processing unit 118 generates a so-called pseudo
three-dimensional image such as a tomographic image of an arbitrary
slice, a projection image from an arbitrary direction, or a
three-dimensional surface image on the basis of an instruction from
the operator, and outputs the generated image data to the display
device 116. The output image data is displayed as an X-ray CT image
on the display device 116.
[0078] The network communication device 119 transmits/receives
various kinds of data to/from another device or a network system
such as an RIS (Radiology Information System) through a
network.
[0079] The data/control bus 300 is a signal line for connecting the
respective units to each other and transmitting/receiving various
kinds of data, control signals, address information, and the
like.
(Collimator)
[0080] The details of the X-ray detector-side collimator will be
described next. This X-ray detector-side collimator has a structure
which ensures to maintain the continuity of an X-ray focal point
and the flatness of each collimator plate even if the detection
range is relatively large in the slice direction.
[0081] FIG. 2B is a view for explaining an outline of a form of
installing an X-ray detector-side collimator 50. As shown in FIG.
2B, the X-ray detector-side collimator 50 is installed along the
shape of the two-dimensional detector system 103 (i.e., in an
arcuated shape) on the X-ray incident side of the two-dimensional
detector system 103.
[0082] FIG. 3 is a view for explaining the arrangement of the X-ray
detector-side collimator 50. As shown in FIG. 3, the X-ray
detector-side collimator 50 has an upper support 500, a lower
support 501, side surface members 502, an abutment plate 503, and
collimator plates 504. Note that with regard to the supports 500
and 501, the terms "upper" and "lower" are defined with reference
to the upper and lower sides of a subject placed along the slice
direction. These terms are defined for the sake of convenience, and
hence the distinction between the terms "upper" and "lower"
concerning the supports is not essential.
[0083] The upper support 500 and the lower support 501 each are
formed into an arcuated shape corresponding to the shape of the
two-dimensional detector system 103, and have grooves 505 for the
insertion of the collimator plates 504. The grooves 505 are formed
at the same pitch along the X-ray incident direction such that an
X-ray focal point exists in a plane including the inserted
collimator plates. The upper support 500 and the lower support 501
are fixed side by side with the side surface members 502 so as to
make the corresponding grooves 505 face each other.
[0084] Note that each of the grooves 505, as shown in FIG. 4, is
triangular shape in the view of y-direction (channel direction).
Each groove is formed in this shape in consideration of convenience
in inserting the collimator plate 504 into the groove 505. However,
the shape of each groove 505 is not limited to this and may have
any shape as long as it can support the collimator plate 504.
[0085] The abutment plate 503 is a plate formed into an arcuated
shape corresponding to the shape of the two-dimensional detector
system 103 (i.e., the shapes of the upper support 500 and lower
support 501), and has grooves 506 formed at the same pitch as that
of the grooves 505 which the upper support 500 and the lower
support 501 have. The abutment plate 503 is made of a material
exhibiting high X-ray resistance, processability, X-ray
transparency, and mechanical structural strength, e.g.,
polyethylene terephthalate, an epoxy resin, or a carbon fiber
resin. The abutment plate 503 is fixed to the arcuated outside
portions of the upper support 500 and lower support 501 (on the
outside arcuated side, i.e., the detection surface side of the
X-ray detector) such that the grooves 506 correspond to the grooves
505 of the upper support 500 and lower support 501.
[0086] The collimator plate 504 is made of a metal exhibiting
excellent rigidity, X-ray shielding property, and mechanical
structure strength, e.g., tungsten or molybdenum. As shown in FIG.
4, the collimator plates 504 are inserted into the grooves 505 of
the upper support 500 and lower support 501 and the grooves 506 of
the abutment plate 503, with each being supported at its three
sides, and are arranged along a direction almost perpendicular to
the slice direction. Note that the collimator plates 504 are fixed
in the grooves 505 and 506 with an adhesive.
(Method of Forming Grooves in Abutment Plate)
[0087] A method of forming the grooves 506 in the abutment plate
503 will be described next.
[0088] FIG. 5 is a view for explaining the method of forming the
grooves 506 in the abutment plate 503. Referring to FIG. 5, first
of all, a CFRP plate 51 having the same shape and size as those of
the abutment plate 503 (without any groove 506) by using a material
exhibiting a high X-ray transmittance such as carbon fiber
reinforced plastic (CFRP resin) with a thickness of about 2 to 3
mm.
[0089] The grooves 506 are then formed in the CFRP plate 51 along
the slice direction by using a blade 52 having a thickness
equivalent to the width of the groove 506 in the channel direction.
At this time, as shown in FIG. 6, each groove 506 is tapered in the
thickness direction of the CFRP plate 51 so as to satisfy A>a
where A is the groove width on the insertion side (X-ray tube side)
of the collimator plate 504 and a is the groove width on the
abutment side (X-ray detector side) of the collimator plate 504.
Each groove 506 is formed in such a shape so as to make the groove
width A almost equal to the groove width a and set the collimator
plate 504 to be almost perpendicular to the abutment plate 503 when
the abutment plate 503 is deformed into an arcuated shape to be
fixed on the arcuated surfaces of the upper support 500 and lower
support 501, as shown in FIG. 7.
[0090] In order to make the groove width A almost equal to the
groove width a in a state wherein the abutment plate 503 is fixed
to the upper support 500 and the lower support 501 (i.e., the state
shown in FIG. 7), the value of the groove width A is preferably
determined on the basis of the curvature of the abutment plate 503
and the groove width a in the fixed state.
[0091] Alternatively, this apparatus may have an arrangement in
which each groove 506 is formed to satisfy groove width A
>>groove width a (i.e., the groove width A is clearly larger
than the groove width a) in the state shown in FIG. 6 so as to
satisfy groove width A>groove width a while the abutment plate
503 is fixed to the upper support 500 and lower support 501. With
this arrangement, the groove 506 has a tapered shape even in the
state wherein the abutment plate 503 is fixed to the upper support
500 and the lower support 501. This makes it easy to insert each
collimator plate 504 and makes it possible to realize
self-alignment of each collimator plate.
[0092] In this embodiment, the abutment plate 503 is formed as an
integral part which covers the upper support 500 and the lower
support 501 (see FIG. 3). However, the present invention is not
limited to this. In consideration of, for example, limitations in
terms of groove processing, this apparatus may have a split
structure which covers the upper support 500 and the lower support
501 with a plurality of abutment plates. If a split arrangement is
to be used, the joint portions are preferably tapered to overlap
each other or placed at the shadows of the collimator plates. This
makes it possible to avoid the influence of the joint portions.
(Collimator Manufacturing Method)
[0093] A method of manufacturing the X-ray detector-side collimator
50 according to the first embodiment will be described next.
[0094] FIG. 8 is a flowchart showing the flow of a manufacturing
process for the X-ray detector-side collimator 50. As shown in FIG.
8, first of all, the upper support 500, lower support 501, and side
surface member 502 are assembled together to form the outer frame
of the X-ray detector-side collimator 50 (step S1).
[0095] An adhesive is applied to the grooves 505 formed in the
upper support 500 and lower support 501 (step S2). The abutment
plate 503 is then elastically deformed into an arcuated shape and
fixed to the arcuated side surfaces on the outer periphery sides of
the upper support 500 and lower support 501 with screws or the like
(step S3).
[0096] An adhesive is applied to the grooves 506 of the abutment
plate 503 (step S4). The collimator plates 504 are then inserted
into the grooves 505 of the upper support 500 and lower support 501
and the grooves 506 of the abutment plate 503 (step S5).
[0097] The resultant structure is then placed in a curing oven to
cure the adhesive to complete the X-ray detector-side collimator 50
with the three sides of each collimator plate 504 being supported
by the grooves 505 and 506 (step S6).
[0098] According to the above arrangement, the following effects
can be obtained.
[0099] This detector-side collimator has an integral structure, and
the angle of each collimator plate with respect to the X-ray focal
point is determined by the corresponding grooves formed in the
upper and lower supports. This prevents the occurrence of deviation
of the X-ray focal point among a plurality of modules as in
conventional module type collimators, and makes it possible to
ensure the continuity of the X-ray focal point. As a consequence,
proper X-ray collimation can be realized.
[0100] In addition, since this detector-side collimator has an
integral structure, no alignment is required between a plurality of
models as in conventional module type collimators. This makes it
possible to reduce work load in installing and maintaining the
X-ray CT apparatus.
[0101] Furthermore, this detector-side collimator is configured to
support each collimator plate at three sides. Therefore, as
compared with a collimator configured to support each collimator
plate at two sides, the flatness of each collimator plate can be
properly maintained. As a consequence, there is no need to perform
maintenance for correcting the warpage of each collimator plate.
This makes it possible to reduce the work load and realize proper
X-ray collimation in imaging operation for X-ray CT images.
Second Embodiment
[0102] A detector-side collimator 50 according to the second
embodiment of the present invention will be described next. The
second embodiment is directed to further ensure the maintenance of
the flatness of each collimator plate as compared with the first
embodiment.
[0103] FIG. 9 is a view showing the arrangement of the
detector-side collimator 50 which an X-ray CT apparatus 10
according to the second embodiment has. As shown in FIG. 9, the
detector-side collimator 50 according to this embodiment further
comprises a guide plate 510 on the arcuated side surfaces on the
inner periphery side in addition to the arrangement shown in FIG.
3.
[0104] The guide plate 510 is a plate formed into an arcuated shape
corresponding to the shape of the detector-side collimator 50
(i.e., the shapes of an upper support 500 and lower support 501),
and has slits 511 formed at the same pitch as that of grooves 505
and 506. Each slit 511 has a width and height that at least allow a
corresponding collimator plate 504 to pass through the slit.
[0105] Like the abutment plate 503, the guide plate 510 is made of
a material exhibiting high X-ray resistance, processability, X-ray
transparency, and mechanical structural strength, e.g.,
polyethylene terephthalate, an epoxy resin, or a carbon fiber
resin. The guide plate 510 is fixed to the arcuated inside portions
(inner arcuated sides) of the upper support 500 and lower support
501 such that the slits 511 correspond to the grooves 505 and 506,
as shown in FIG. 10A.
[0106] The guide plate 510 can be manufactured as follows. As shown
in FIG. 10B, a CFRP plate 53 having the same shape and size as
those of the guide plate 510 (without any slit 511) is formed by
using a material having a high X-ray transmittance such as carbon
fiber reinforced plastic (CFRP resin).
[0107] The slits 511 are then formed in the CFRP plate 53 along the
slice direction by using a blade 54 having a thickness equivalent
to the width of the slits 511 in the channel direction, thereby
manufacturing the guide plate 510. Note that FIG. 10C is a
sectional view of the guide plate 510 in a plane along the slits
511.
(Collimator Manufacturing Method)
[0108] A method of manufacturing the detector-side collimator 50
according to the second embodiment will be described next.
[0109] FIG. 11 is a flowchart showing the flow of a manufacturing
process for the detector-side collimator 50. The process from steps
S11 to S14 in FIG. 11 is the same as the process from steps S1 to
S4 shown in FIG. 8, and hence a description thereof will be
omitted.
[0110] After an adhesive is applied to the grooves 506 of the
abutment plate 503, the guide plate 510 with slits is assembled to
the upper support 500 and the lower support 501 (step S15). After
this assembly, the collimator plates 504 are inserted into the
grooves 505 of the upper support 500 and lower support 501 and the
grooves 506 of the abutment plate 503 through the slits 511 of the
guide plate 510 (step S16).
[0111] After an adhesive is applied to the slits 511 (step S17),
the resultant structure is placed in a curing oven to cure the
adhesive, thereby completing the detector-side collimator 50 with
the four sides of each collimator plate 504 being supported by the
groove 505, groove 506, and slit 511 (step S18).
[0112] According to the above arrangement, in addition to the
effects described in the first embodiment, the flatness of each
collimator plate can be maintained with higher accuracy. Even if,
therefore, the detection range in the slice direction is wider, the
flatness of each collimator plate can be properly maintained.
Third Embodiment
[0113] A detector-side collimator according to the third embodiment
of the present invention, and an X-ray CT apparatus comprising such
collimator will be described. The present detector-side collimator
has a structure in which each collimator plate is supported by four
sides, with an upper support, a lower support, an integral abutment
plate and an integral internal diameter cover.
[0114] FIG. 12 is a view showing the arrangement of a detector-side
collimator 50 possessed by an X-ray CT apparatus 10 according to
the third embodiment. As illustrated, the detector-side collimator
50 according to the present embodiment comprises an upper support
500, a lower support 501, side surface members 502, an abutment
plate 503, an integral internal diameter cover 520 and a plurality
of collimator plates 504.
[0115] The abutment plate 503 is in an integral structure and has
grooves 506 so as to insert one side of the collimator plate
504.
[0116] The internal diameter cover 520 is a plate formed in a shape
of the upper support 500 and the lower support 501 (i.e. in an
arcuated shape). The internal diameter cover 520 which is a cover
to support the collimator plate 504 from the internal diameter-side
of the upper support 500 and the lower support 501 has grooves 521
to insert one side of each collimator plate 504. Likewise the
abutment plate 503, this internal diameter cover 520 is made of a
material exhibiting high X-ray resistance, processability, X-ray
transparency, and mechanical structural strength, e.g.,
polyethylene terephthalate, an epoxy resin, or a carbon fiber
resin.
[0117] FIG. 13 is a view for explaining a method of forming grooves
521 of the internal diameter cover 520. As illustrated, first, a
CFRP plate 55 bearing the shape and size of the internal diameter
cover 520 (without any groove 521) is formed by using a material
having a high X-ray transmittance such as carbon fiber reinforced
plastic (CFRP resin) in the thickness of about 2 to 3 mm.
[0118] The grooves 521 are then formed on the CFRP plate 55 along
the slice direction by using a blade 52 having a thickness
equivalent to the width of the grooves 521 in the channel
direction. At this time, as shown in FIG. 14, each groove 521 is
tapered in the thickness direction of the CFRP plate 55 so as to
satisfy groove widths B>b where B is the groove width on the
insertion side (X-ray detector-side) of the collimator plate 504
and b is the groove width on the abutment side (X-ray tube-side) of
the collimator plate 504. Each groove 521 is formed in such a shape
so as to make the groove width B almost equal to the groove width b
and set the collimator plate 504 almost perpendicular to the
internal diameter cover 520 when deforming the internal diameter
cover 520 into an arcuated shape to be fixed along the arcuated
surfaces of the upper support 500 and lower support 501, as shown
in FIG. 15.
[0119] In order to make the groove width B almost equal to the
groove width b in a state where the internal diameter cover 520 is
fixed to the upper support 500 and the lower support 501 (i.e., the
state shown in FIG. 15), the value of the groove width B is
preferably determined on the basis of the curvature of the internal
diameter cover 520 and the groove width b in such fixed state.
(Collimator Manufacturing Method)
[0120] A method of manufacturing the detector-side collimator 50
according to the present embodiment will be described next.
[0121] FIG. 16 is a flowchart showing the flow of a manufacturing
process for the detector-side collimator 50. The process from steps
S21 to S24 in FIG. 16 is approximately the same as the process from
steps S1 to S4 shown in FIG. 8, and hence a description thereof
will be omitted.
[0122] After an adhesive is applied to grooves 506 of the abutment
plate 503, the collimator plates 504 are inserted in grooves 505 of
the upper support 500 and the lower support 501 and the grooves 506
of the abutment plate 503 (step S25).
[0123] Then, after an adhesive is applied to the grooves 521 of the
internal diameter cover 520 (step S26), the internal diameter cover
520 is fixed on the upper support 500, the lower support 501, and
the side surface members 502 while inserting each collimator plate
504 into each groove 521, (step S27). In addition, when inserting
each collimator plate 504 into each groove 521, the internal
diameter cover 520 may also be pressed along the inserting
direction, or may be pressed while causing either one of the
collimator plate 504-side and the internal diameter cover 520 to
vibrate, if needed.
[0124] The collimator 50 is then placed in a curing oven to cure
the adhesive (step S28). As a result of each process above, the
detector-side collimator 50 in which the four sides of each
collimator plate 504 are supported by the grooves 505, 506 and 521
is completed.
[0125] Further, the adhesive for grooves 505, 506 and 521 is not
mandatory. For example, if each collimator plate 504 can be
supported sufficiently without an adhesive, it is fine to omit the
application of adhesives on at least one or all grooves. The same
applies to other embodiments in this regard.
(Modified Examples)
[0126] Next, modified examples of the present embodiment will be
explained. A detector-side collimator 50 according to the present
modified example supports one side among the four sides of a
collimator signal plate 504 by an internal diameter cover which
does not have groove 521.
[0127] FIG. 17 is a view showing the arrangement of a detector-side
collimator 50 according to the present modified example. As
illustrated, the detector-side collimator 50 is provided with an
internal diameter cover 525, which is integral and does not have
grooves for inserting the collimator plates 504.
[0128] Except for the point that there is no groove 521 formed on
the internal diameter cover 525, it has the same structure as the
internal diameter cover 520. As shown in FIG. 18, this internal
diameter cover 525 is fixed on the upper support 500, lower support
501 and side surface members 502 in a manner that would press one
side of each collimator plate 504 (i.e., one side of the X-ray tube
101-side). Pressed by the internal diameter cover 525, the
collimator plate 504 is supported by one side.
(Collimator Manufacturing Method)
[0129] A method of manufacturing the detector-side collimator 50
according to the present modified example will be described
next.
[0130] FIG. 19 is a flowchart showing the flow of a manufacturing
process for the detector-side collimator 50. The process from steps
S31 to S35 shown in FIG. 19 is basically the same as the process
from steps S21 to S25 shown in FIG. 16, and hence a description
thereof will be omitted.
[0131] After inserting the collimator plates 504, the internal
diameter cover 525 is fixed on the upper support 500, lower support
501 and side surface members 502 in a manner that would press one
side of the X-ray tube 101-side of each collimator plate 504 (step
S36).
[0132] The collimator 50 is then placed in a curing oven to cure
the adhesive (step S37). As a result of each process above, the
detector-side collimator 50 in which the four sides of each
collimator plate 504 are supported by the grooves 505 and 506 and
the internal diameter 525 is completed.
[0133] According to the above arrangement, in addition to the
effects described in the first embodiment, a next new effect can be
realized.
[0134] In the present detector-side collimator, each collimator
plate is supported by four sides. Accordingly, in comparison to the
case of the conventional two sides support and the three sides
support, it is possible to realize a detector-side collimator with
high flatness in the collimator plates. As a result, it is possible
to realize an ideal collimation. Particularly, even if the
detection range in the slice direction is wider, the flatness of
each collimator plate can be properly maintained.
[0135] Further, as the collimator plates are supported equally by
four sides. For this reason, the collimator plates can maintain
high rigidity even when the detector side collimator is rotated
with a central focus on the body axis of a subject at a high speed
of one second or less per rotation. As a result, the operation of
restoring flatness of the collimator plates upon maintenance can be
reduced.
Fourth Embodiment
[0136] A detector-side collimator according to the fourth
embodiment of the present invention, and an X-ray CT apparatus
comprising such collimator will be described. The present
detector-side collimator has a structure in which each collimator
plate is supported by four sides, with an upper support, a lower
support, an integral abutment plate and a module type internal
diameter cover.
[0137] FIG. 20A is a view showing the arrangement of a
detector-side collimator 50 possessed by an X-ray CT apparatus 10
according to the fourth embodiment. As illustrated, the
detector-side collimator 50 according to the present embodiment
comprises an upper support 500, a lower support 501, side surface
members 502, an abutment plate 503, a module type internal diameter
cover 530 and a plurality of collimator plates 504.
[0138] The abutment plate 503 is in an integral structure and has
grooves 506 so as to insert one side of the collimator plate
504.
[0139] The internal diameter cover 530 is a plate bearing an
arcuated shape corresponding to the curvature (i.e., the curvature
of an arc) of the upper support 500 and the lower support 501 in
the channel direction, and is arranged plurally along the channel
direction. The internal diameter cover 530 is a cover that supports
the collimator plate 504 from the internal diameter-side of the
upper support 500 and the lower support 501, and has a groove 531
for inserting one side of the collimator plate 504. Likewise the
abutment plate 503, this internal diameter cover 530 is made of a
material exhibiting high X-ray resistance, processability, X-ray
transparency, and mechanical structural strength, such as
polyethylene terephthalate, an epoxy resin, or a carbon fiber
resin.
[0140] Further, the internal diameter cover 530 has groove 532,
which is different from groove 531. When arranging a plurality of
internal diameter covers 530 along the channel direction, the
grooves 532 of the neighboring internal diameter covers 530 form a
groove 531 for inserting the collimator plate 504 as shown in FIGS.
20B and 20C. By inserting the collimator plates 504 in the grooves
531 formed by the grooves 532 of the neighboring internal diameter
covers 530 in this manner, an effect on the X-ray detection caused
by the joint of the internal diameter cover 530 can be
circumvented.
[0141] In addition, the internal diameter cover 530 can be arranged
either in the channel direction with a certain space d as in FIG.
20B or in the channel direction that enables the neighbors to come
in contact as in FIG. 20D. In either arrangement, the width of
groove 532 in the channel direction is designed to form a groove
533 by the grooves 532 of the neighboring internal diameter covers
530.
[0142] Such internal diameter cover 530 can be produced by the
means almost similar to the internal diameter cover 520 according
to the third embodiment.
(Collimator Manufacturing Method)
[0143] A method of manufacturing the detector-side collimator 50
according to the present embodiment will be described next.
[0144] FIG. 21 is a flowchart showing the flow of a manufacturing
process for the detector-side collimator 50. The process from steps
S41 to S45 shown in FIG. 21 is basically the same as the process
from steps S31 to S35 shown in FIG. 19, and hence a description
thereof will be omitted.
[0145] After inserting the collimator plates 504, an adhesive is
applied to the grooves 531 and the grooves 532 of each modularized
internal diameter cover 530 (step S46), which is then fixed on the
upper support 500, lower support 501 and side surface members 502
while inserting each collimator plate 504 in each groove 531 (step
S47). Meanwhile, when inserting each collimator plate 504 in each
groove 531 and groove 532, the internal diameter cover 530 may be
pressed along the inserting direction, or may be pressed while
causing at least either one of the collimator plate 504-side and
the internal diameter cover 530 to vibrate, according to need.
[0146] The collimator 50 is then placed in a curing oven to cure
the adhesive (step S48). As a result of each process above, the
detector-side collimator 50 in which the four sides of each
collimator plate 504 is being supported by the grooves 505, 506 and
521 is completed.
(Modified Example)
[0147] Next, modified examples of the present embodiment will be
explained. A detector-side collimator 50 according to the present
modified example supports one side among the four sides of a
collimator signal plate 504 by a modularized internal diameter
cover, which does not have grooves 532.
[0148] FIG. 22 is a view showing the arrangement of the
detector-side collimator 50 according to the present modified
example. As illustrated, the detector-side collimator 50 comprises
an internal diameter cover 533, which is modularized and does not
have grooves for inserting collimator plates 504.
[0149] Except for the point that there is no groove 531 formed on
the internal diameter cover 533, it has the same arrangement as the
internal diameter cover 530. Likewise the example shown in FIG. 18,
each internal diameter cover 533 is fixed on the upper support 500,
lower support 501 and side surface members 502 in a manner that
presses one side of each collimator plate 504 (i.e., one side of
the X-ray tube 101-side). Pressed by the internal diameter cover
533, the collimator plate 504 is supported by one side.
(Collimator Manufacturing Method)
[0150] A method of manufacturing the detector-side collimator 50
according to the present modified example will be described
next.
[0151] FIG. 23 is a flowchart showing the flow of a manufacturing
process for the detector-side collimator 50. Since the process from
steps S51 to S55 is basically the same as the process from steps
S41 to S45 shown in FIG. 21, description thereof will be
omitted.
[0152] After inserting the collimator plates 504, the internal
diameter cover 533 is fixed on the upper support 500, lower support
501 and side surface members 502 in a manner that presses one side
of the X-ray tube 101-side of each collimator plate 504 (step
S56).
[0153] The collimator 50 is then placed in a curing oven to cure
the adhesive (step S57). As a result of each process above, the
detector-side collimator 50 in which the four sides of each
collimator plate 504 is being supported by the grooves 505 and 506
and the internal diameter cover 533 is completed.
[0154] According to the above arrangement, the next new effect can
be realized in addition to the effect described in the third
embodiment. In other words, being modularized, the internal
diameter cover supporting one side of the collimator plate can be
partially disassembled. Accordingly, when there is need to, for
example, adjust or change a portion of the collimator plate, this
may be done by simply removing the internal diameter cover
supporting such collimator plate. Consequently, this can reduce
operation loads and expenses upon maintenance.
Fifth Embodiment
[0155] A detector-side collimator according to the fifth embodiment
of the present invention, and an X-ray CT apparatus comprising such
collimator will be described. The present detector-side collimator
has a structure in which each collimator plate is supported by four
sides, with an upper support, a lower support, an integral internal
diameter cover and a module type abutment plate.
[0156] FIG. 24 is a view showing the arrangement of a detector-side
collimator 50 possessed by an X-ray CT apparatus 10 according to
the fifth embodiment. As illustrated, the detector-side collimator
50 according to the present embodiment comprises an upper support
500, a lower support 501, side surface members 502, a modularized
abutment plate 540, an integral internal diameter cover 520 and a
plurality of collimator plates 504.
[0157] FIG. 25A is a view showing an aspect of an abutment plate
540. As illustrated, a plurality of abutment plates 540 is arranged
along the channel direction. The abutment plate 540 has a groove
541 to insert one side of the collimator plate 504. Likewise the
abutment plate 503, this abutment plate 540 is made of a material
exhibiting high X-ray resistance, processability, X-ray
transparency, and mechanical structural strength, e.g.,
polyethylene terephthalate, an epoxy resin, or a carbon fiber
resin. Again, the abutment plate 540 can be made by almost the same
method as for the abutment plate 503 (see FIGS. 13, 14 and 15).
[0158] Further, the abutment plate 540 has a groove 542, which is
different from the groove 541. As illustrated in FIGS. 25A and 25B,
when arranging a plurality of abutment plates 540 in a channel
direction, the grooves 542 of the neighboring abutment plates 540
form a groove 543 for inserting the collimator plate 504. By
inserting the collimator plates 504 in the grooves 543 formed by
the grooves 542 of the neighboring abutment plates 540 in this
manner, an effect on the X-ray detection caused by the joint of the
abutment plate 540 can be circumvented.
[0159] In addition, the abutment plate 540 can be arranged either
in the channel direction with a certain space d as in FIG. 25A or
in the channel direction which the neighbors come in contact as in
FIG. 25C. In either arrangement, the width of the groove 542 in the
channel direction is designed to form a groove 543 by the grooves
542 of the neighboring abutment plates 540.
(Collimator Manufacturing Method)
[0160] A method of manufacturing the detector-side collimator 50
according to the present embodiment will be described next.
[0161] FIG. 26 is a flowchart showing the flow of a manufacturing
process for the detector-side collimator 50. As illustrated, first,
the upper support 500, lower support 501 and side surface members
502 are assembled to form an outer frame of the X-ray detector-side
collimator 50 (step S61). Then, an adhesive is applied to grooves
505 formed respectively on the upper support 500 and lower support
501 (step S62), and each modularized abutment plate 540 is
resiliently deformed in a circular arc shape and assembled by, for
example, a screw clamp on the arcuated side surface of the
circumference-side of the upper support 500 and the lower support
501 (step S63).
[0162] An adhesive is then applied to the grooves 541 and 542 of
each abutment plate 540 (step S64), and the collimator plates 504
are inserted in the grooves 505 of the upper support 500 and the
lower support 501 and the grooves 541 of each abutment plate 540
(step S65).
[0163] Then, after an adhesive is applied to the grooves 521 of the
internal diameter cover 520 (step S66), the internal diameter cover
520 is fixed on the upper support 500, the lower support 501 and
the side surface members 502 while inserting each collimator plate
504 into each groove 521 (step S67). In addition, when inserting
each collimator plate 504 into each groove 521, the internal
diameter cover 520 may be pressed along the inserting direction, or
may be pressed while causing at least either one of the collimator
plate 504-side and the internal diameter cover 520 to vibrate,
according to need.
[0164] The collimator 50 is then placed in a curing oven to cure
the adhesive (step S68). As a result of each process above, the
detector-side collimator 50 in which the four sides of each
collimator plate 504 is being supported by the grooves 505, 521,
541 and 542 is completed.
(Modified Examples)
[0165] Next, modified examples of the present embodiment will be
explained. A detector-side collimator 50 according to the present
modified example supports one side among the four sides of a
collimator signal plate 504 by an internal diameter cover 525,
which does not have grooves 521.
[0166] FIG. 27 is a view showing the arrangement of the
detector-side collimator 50 according to the present modified
example. As illustrated, the detector-side collimator 50 comprises
a modularized abutment plate 540 and an internal diameter cover
525, which is integral and does not have grooves for inserting
collimator plates 504.
(Collimator Manufacturing Method)
[0167] A method of manufacturing the detector-side collimator 50
according to the present modified example will be described
next.
[0168] FIG. 28 is a flowchart showing the flow of a manufacturing
process for the detector-side collimator 50. Since the process from
steps S71 to S75 is basically the same as the process from steps
S61 to S65 shown in FIG. 26, description thereof will be
omitted.
[0169] After the collimator plates 504 are inserted, the internal
diameter cover 525 is fixed on the upper support 500, lower support
501 and side surface members 502 in a manner which presses one side
of the X-ray tube 101-side of each collimator plate 504 (step
S76).
[0170] The collimator 50 is then placed in a curing oven to cure
the adhesive (step S77). As a result of each process above, the
detector-side collimator 50 in which the four sides of each
collimator plate 504 is being supported by the grooves 505 and 541
and the internal diameter cover 525 is completed.
[0171] According to the above arrangement, the next new effect can
be realized in addition to the effect described in the third
embodiment. In other words, being modularized, the abutment plate
supporting one side of the collimator plate can be partially
disassembled. Accordingly, when there is need to, for example,
adjust or change a portion of the collimator plate, this may be
done by only removing the abutment plate supporting such collimator
plate. Consequently, this can reduce operation loads and expenses
upon maintenance.
Sixth Embodiment
[0172] A detector-side collimator according to the sixth embodiment
of the present invention, and an X-ray CT apparatus comprising such
collimator will be described. The present detector-side collimator
has a structure in which each collimator plate is supported by four
sides, with an upper support, a lower support, an abutment plate
and upper and lower internal diameter covers.
[0173] FIG. 29 is a view showing the arrangement of a detector-side
collimator 50 possessed by an X-ray CT apparatus 10 according to
the sixth embodiment. As illustrated, the detector-side collimator
50 according to the present embodiment comprises an upper support
500, a lower support 501, side surface members 502, an abutment
plate 503, an integral upper internal diameter cover 550, an
integral lower internal diameter cover 551 and a plurality of
collimator plates 504.
[0174] The upper internal diameter cover 550 and the lower internal
diameter cover 551 are plates which each bears an arcuated shape
corresponding to the curvature (i.e., the curvature of an arc) of
the upper support 500 and the lower support 501 in the channel
direction. The upper internal diameter cover 550 is a cover that
supports the collimator plate 504 from the internal diameter side
of the upper support 500 and has a groove 552 to insert one side of
the collimator plate 504. Likewise the abutment plate 503, the
upper internal diameter cover 550 and lower internal diameter cover
551 are made of a material exhibiting high X-ray resistance,
processability, X-ray transparency, and mechanical structural
strength, such as polyethylene terephthalate, an epoxy resin, or a
carbon fiber resin.
[0175] In addition, the upper internal diameter cover 550 and the
lower internal diameter cover 551 can be made by basically the same
method as for making the internal diameter cover 520 according to
the third embodiment.
(Collimator Manufacturing Method)
[0176] A method of manufacturing the detector-side collimator 50
according to the present embodiment will be described next.
[0177] FIG. 30 is a flowchart showing the flow of a manufacturing
process for the detector-side collimator 50. The process from steps
S81 to S85 is basically the same as the process from steps S21 to
S25 shown in FIG. 16, and hence a description thereof will be
omitted.
[0178] After inserting the collimator plates 504, an adhesive is
applied to grooves 552 on the upper internal diameter cover 550
(step S86), which is then fixed on the upper support 500 and side
surface members 502 while inserting each collimator plate 504 in
each groove 552. Further, an adhesive is applied to grooves 552 on
the lower internal diameter cover 551, which is then fixed on the
lower support 501 and side surface members 502 while inserting each
collimator plate 504 in each groove 552 (step S87). Meanwhile, when
inserting each collimator plate 504 in each groove 552, the upper
internal diameter cover 550 (lower internal diameter cover 551) may
be pressed along the inserting direction or may be pressed while
causing at least either one of the collimator plate 504-side and
the internal diameter cover 550 to vibrate, according to need.
[0179] The collimator 50 is then placed in a curing oven to cure
the adhesive (step S88). As a result of each process above, the
detector-side collimator 50 in which the four sides of each
collimator plate 504 is supported by the grooves 505, 506 and 552
is completed.
(Modified Examples)
[0180] Next, modified examples of the present embodiment will be
explained. A detector-side collimator 50 according to the present
modified example supports one side among the four sides of a
collimator signal plate 504 by an upper internal diameter cover 555
and a lower internal diameter cover 556 which do not have grooves
552.
[0181] FIG. 31 is a view showing the arrangement of the
detector-side collimator 50 according to the present modified
example. As illustrated, the detector-side collimator 50 comprises
an upper internal diameter cover 555 and lower internal diameter
cover 556, which do not have grooves for inserting collimator
plates 504.
[0182] Except for the point that there are no grooves 552 formed on
the upper internal diameter cover 555 and lower internal diameter
cover 556, they have the same structures as the upper internal
diameter cover 550 and the lower internal diameter cover 551.
Likewise the example shown in FIG. 32, the upper internal diameter
cover 555 and lower internal diameter cover 556 are fixed on the
upper support 500 and so forth in a manner that presses one side of
each collimator plate 504 (i.e., one side of the X-ray tube
101-side). Pressed by the upper internal diameter cover 555 and the
lower internal diameter cover 556, the collimator plate 504 has the
one side supported.
(Collimator Manufacturing Method)
[0183] A method of manufacturing the detector-side collimator 50
according to the present modified example will be described
next.
[0184] FIG. 33 is a flowchart showing the flow of a manufacturing
process for the detector-side collimator 50. Since the process from
steps S91 to S95 is basically the same as the process from steps
S81 to S85 shown in FIG. 30, description thereof will be
omitted.
[0185] After inserting the collimator plates 504, the upper
internal diameter cover 555 is fixed on the upper support 500 and
side surface members 502 so as to press one side of the X-ray tube
101-side of each collimator plate 504. Further, the lower internal
diameter cover 556 is fixed on the lower support 501 and side
surface members 502 so as to press one side of the X-ray tube
101-side of each collimator plate 504 (step S96).
[0186] The collimator 50 is then placed in a curing oven to cure
the adhesive (step S97). As a result of each process above, the
detector-side collimator 50 in which the four sides of each
collimator plate 504 is supported by the grooves 505 and 506, the
upper internal diameter cover 555 and lower internal diameter cover
556 is completed.
[0187] According to the above arrangement, an effect equivalent to
the third embodiment can be realized.
[0188] Note that the present invention is not limited to the above
embodiments, and constituent elements can be modified and embodied
in the execution stage within the spirit and scope of the
invention.
[0189] (1) The guide plate 510 described in the second embodiment
comprises the integral member which covers the upper support 500
and the lower support 501 (see FIGS. 9 and 10). However, the
present invention is not limited to this. In consideration of, for
example, limitations in terms of groove processing, this guide
plate may have a split structure which covers the upper support 500
and the lower support 501 with a plurality of plates. If a split
arrangement is to be used, the joint portions are preferably
tapered to overlap each other or placed at the shadows of the
collimator plates as in the case of the abutment plate 503.
[0190] (2) The abutment plate 503 and guide plate 510 described in
each embodiment may be applied to a module type collimator. This
makes it possible to maintain the flatness of each collimator plate
in a module type collimator with higher accuracy than in the prior
art.
[0191] (3) The detector-side collimator described in each
embodiment may comprise a plurality of (e.g., three or four)
collimator units (50) coupled to each other instead of a completely
integral structure. In this case, the arrangements described in the
respective embodiments and modifications (1) and (2) can be applied
to each collimator unit (50).
[0192] (4) The detector-side collimator according to the sixth
embodiment may be arranged to modularize at least either one of the
upper internal diameter cover and the lower internal diameter cover
as shown, for example, in FIG. 34.
[0193] In addition, various inventions can be formed by proper
combinations of a plurality of constituent elements disclosed in
the above embodiments. For example, several constituent elements
may be omitted from all the constituent elements disclosed in the
above embodiments. Furthermore, constituent elements in the
different embodiments may be properly combined.
* * * * *