U.S. patent application number 10/920464 was filed with the patent office on 2006-02-23 for light detector, radiation detector and radiation tomography apparatus.
Invention is credited to Masahiro Moritake, George Edward Possin, Gregory Scott Zeman.
Application Number | 20060039528 10/920464 |
Document ID | / |
Family ID | 35909632 |
Filed Date | 2006-02-23 |
United States Patent
Application |
20060039528 |
Kind Code |
A1 |
Moritake; Masahiro ; et
al. |
February 23, 2006 |
LIGHT DETECTOR, RADIATION DETECTOR AND RADIATION TOMOGRAPHY
APPARATUS
Abstract
A light detector includes a plurality of light receiving
sections which are formed in a substrate and generate signal
charges corresponding to the amount of incident light, and a
plurality of wirings which are formed on the substrate and fetch
the signal charges from the light receiving sections, wherein at
least some of the plurality of wirings are disposed so as to
overlap with other light receiving sections different from the
light receiving sections connected to fetch the signal charges.
Inventors: |
Moritake; Masahiro; (Tokyo,
JP) ; Possin; George Edward; (Niskayuna, NY) ;
Zeman; Gregory Scott; (Waukesha, WI) |
Correspondence
Address: |
PATRICK W. RASCHE;ARMSTRONG TEASDALE LLP
ONE METROPOLITAN SQUARE, SUITE 2600
ST. LOUIS
MO
63102-2740
US
|
Family ID: |
35909632 |
Appl. No.: |
10/920464 |
Filed: |
August 18, 2004 |
Current U.S.
Class: |
378/19 ;
250/208.1; 250/370.11 |
Current CPC
Class: |
G01T 1/2985 20130101;
G01T 1/1644 20130101; A61B 6/032 20130101 |
Class at
Publication: |
378/019 ;
250/370.11; 250/208.1 |
International
Class: |
G01N 23/00 20060101
G01N023/00 |
Claims
1. A light detector comprising: a plurality of light receiving
sections which are formed in a substrate and generate signal
charges corresponding to the amount of incident light; and a
plurality of wirings which are formed on the substrate and fetch
the signal charges from the light receiving sections, wherein some
of the plurality of wirings are disposed so as to overlap with
other light receiving sections different from the light receiving
sections connected to fetch the signal charges.
2. The light detector according to claim 1, wherein the light
receiving sections are arranged in matrix form.
3. The light detector according to claim 2, wherein other wirings
of the plurality of wirings are respectively disposed among the
light receiving sections arranged in matrix form.
4. The light detector according to claim 3, wherein the wirings
connected to the light receiving sections are drawn to one end or
the other end of the substrate with a central portion of a matrix
as a boundary.
5. The light detector according to claim 4, wherein the wirings
connected to the light receiving sections located on the center
side of the matrix are drawn to the end of the substrate so as to
extend among the light receiving sections, and wherein the wirings
connected to the light receiving sections located on the end side
of the matrix are drawn to the end of the substrate in an extended
form so as to overlap with other light receiving sections.
6. A radiation detector comprising: a plurality of light receiving
sections which are formed in a substrate and generate signal
charges corresponding to the amount of incident light; a plurality
of wirings which are formed on the substrate and fetch the signal
charges from the light receiving sections; and scintillators which
are provided on the light receiving sections of the substrate and
emit lights each having a wavelength longer than that of radiation
in accordance with the incidence of the radiation, wherein some of
the plurality of wirings are disposed so as to overlap with other
light receiving sections different from the light receiving
sections connected to fetch the signal charges.
7. The radiation detector according to claim 6, wherein the light
receiving sections are arranged in matrix form.
8. The radiation detector according to claim 7, wherein other
wirings of the plurality of wirings are respectively disposed among
the light receiving sections arranged in matrix form.
9. The radiation detector according to claim 8, wherein the wirings
connected to the light receiving sections are drawn to one end or
the other end of the substrate with a central portion of a matrix
as a boundary.
10. The radiation detector according to claim 9, wherein the
wirings connected to the light receiving sections located on the
center side of the matrix are drawn to the end of the substrate so
as to extend among the light receiving sections, and wherein the
wirings connected to the light receiving sections located on the
end side of the matrix are drawn to the end of the substrate in an
extended form so as to overlap with other light receiving
sections.
11. The radiation detector according to claim 6, further comprising
a reflection layer which covers the scintillators and reflects the
lights emitted from the scintillators to the light receiving
sections.
12. A radiation tomography apparatus comprising: a radiation
irradiating device which irradiates a subject with radiation; and a
radiation detector which detects the radiation transmitted through
the subject, said radiation detector including, a plurality of
light receiving sections which are formed in a substrate and
generate signal charges corresponding to the amount of incident
light; a plurality of wirings which are formed on the substrate and
fetch the signal charges from the light receiving sections; and
scintillators which are provided on the light receiving sections of
the substrate and emit lights each having a wavelength longer than
that of the radiation in accordance with the incidence of the
radiation, wherein some of the plurality of wirings are disposed so
as to overlap with other light receiving sections different from
the light receiving sections connected to fetch the signal
charges.
13. The radiation tomography apparatus according to claim 12,
wherein the light receiving sections are arranged in matrix
form.
14. The radiation tomography apparatus according to claim 13,
wherein other wirings of the plurality of wirings are respectively
disposed among the light receiving sections arranged in matrix
form.
15. The radiation tomography apparatus according to claim 14,
wherein the wirings connected to the light receiving sections are
drawn to one end or the other end of the substrate with a central
portion of a matrix as a boundary.
16. The radiation tomography apparatus according to claim 15,
wherein the wirings connected to the light receiving sections
located on the center side of the matrix are drawn to the end of
the substrate so as to extend among the light receiving sections,
and wherein the wirings connected to the light receiving sections
located on the end side of the matrix are drawn to the end of the
substrate in an extended form so as to overlap with other light
receiving sections.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a light detector, a
radiation detector and a radiation tomography apparatus.
[0002] An X-ray detector wherein X-ray detection modules each
formed with a plurality of photodiodes are provided side by side in
plural form in a channel direction, has been used in a multi-slice
type X-ray CT apparatus (refer to, for example, the following
patent document 1).
[0003] FIG. 7 is a fragmentary plan view of a conventional X-ray
detector. As shown in FIG. 7, a plurality of photodiodes 243 are
disposed in matrix form in the X-ray detector, more specifically,
one X-ray detection module of the X-ray detector. In the drawing, a
z direction corresponds to a slice direction (body axial direction)
and an x direction corresponds to a channel direction,
respectively.
[0004] Since wirings (signal lines) 245 for fetching signal charges
generated in the photodiodes 243 hardly pass light, they have
heretofore been disposed in regions among the photodiodes 243
respectively.
[0005] [Patent Document 1] Japanese Unexamined Patent Publication
No. 2000-60840
[0006] However, the multi-slice type X-ray CT apparatus is
accompanied by the problem that as the number of the photodiodes
243 in the slice direction (z direction) increases, the number of
the wirings 245 that pass through the regions among the photodiodes
arranged in the x direction increases, and there is hence a need to
form fine wirings in the regions among the photodiodes 243, thereby
causing a difficulty in its fabrication and a rise in its
manufacturing cost.
[0007] Here, it is also considered that in view of a limit of
wiring miniaturization or scale-down, as shown in FIG. 8, the
interval d defined between adjacent photodiodes 243 arranged in an
x direction is made wide and the width w of each photodiode 243 is
made small. A problem, however, arises in that since the area of
the photodiode 243 becomes small correspondingly, light detection
efficiency is reduced.
SUMMARY OF THE INVENTION
[0008] Therefore, a first object of the present invention is to
provide a light detector capable of suppressing a decrease in the
area of a light receiving section with an increase in the number of
wirings and thereby suppressing a reduction in light detection
efficiency.
[0009] A second object of the present invention is to provide a
radiation detector capable of suppressing a decrease in the area of
a light receiving section with an increase in the number of wirings
and thereby suppressing a reduction in radiation detection
efficiency.
[0010] A third object of the present invention is to provide a
radiation tomography apparatus capable of suppressing a decrease in
the area of a light receiving section with an increase in the
number of wirings and thereby suppressing a reduction in radiation
detection efficiency.
[0011] In order to achieve the above objects, a light detector of
the present invention comprises a plurality of light receiving
sections which are formed in a substrate and generate signal
charges corresponding to the amount of incident light, and a
plurality of wirings which are formed on the substrate and fetch
the signal charges from the light receiving sections. Some of the
plurality of wirings are disposed so as to overlap with other light
receiving sections different from the light receiving sections
connected to fetch the signal charges.
[0012] In the light detector of the present invention, some of the
plurality of wirings are disposed so as to overlap with other light
receiving sections different from the light receiving sections
connected to fetch the signal charges. The area of each light
receiving section formed in the substrate is not limited by the
wirings. Although the wirings shields the light from entering the
light receiving sections, the light reaches the light receiving
sections in regions other than the wirings, and thereby the signal
charges corresponding to the amount of the incident light are
generated by the light receiving units.
[0013] In order to achieve the above objects, a radiation detector
of the present invention comprises a plurality of light receiving
sections which are formed in a substrate and generate signal
charges corresponding to the amount of incident light, a plurality
of wirings which are formed on the substrate and fetch the signal
charges from the light receiving sections, and scintillators which
are provided on the light receiving sections of the substrate and
emit lights each having a wavelength longer than that of radiation
in accordance with the incidence of the radiation. Some of the
plurality of wirings are disposed so as to overlap with other light
receiving sections different from the light receiving sections
connected to fetch the signal charges.
[0014] In the radiation detector of the present invention, some of
the plurality of wirings are disposed so as to overlap with other
light receiving sections different from the light receiving
sections connected to fetch the signal charges. The area of each
light receiving section formed in the substrate is not limited by
the wirings. Although the wirings shields the lights emitted from
the scintillators in accordance with the incidence of the radiation
from entering the light receiving sections, the lights reach the
light receiving sections in regions other than the wirings and
thereby the signal charges corresponding to the amount of the
incident light are generated by the light receiving sections.
[0015] In order to achieve the above objects, a radiation
tomography apparatus of the present invention comprises radiation
irradiating means which irradiates a subject with radiation, and a
radiation detector which detects the radiation transmitted through
the subject. The radiation detector includes a plurality of light
receiving sections which are formed in a substrate and generate
signal charges corresponding to the amount of incident light, a
plurality of wirings which are formed on the substrate and fetch
the signal charges from the light receiving sections, and
scintillators which are provided on the light receiving sections of
the substrate and emit lights each having a wavelength longer than
that of the radiation in accordance with the incidence of the
radiation. Some of the plurality of wirings are disposed so as to
overlap with other light receiving sections different from the
light receiving sections connected to fetch the signal charges.
[0016] In the radiation tomography apparatus of the present
invention, some of the plurality of wirings connected to the light
receiving sections of the radiation detector are disposed so as to
overlap with other light receiving sections different from the
light receiving sections connected to fetch the signal charges, and
the area of each light receiving section formed in the substrate is
not limited by the wirings. The radiation is launched into the
subject by the radiation irradiating means. The radiation
transmitted through the subject is launched into the scintillators
of the radiation detector. Although the wirings shields the lights
emitted from the scintillators in accordance with the incidence of
the radiation from entering into the light receiving sections, the
lights reach the light receiving sections in regions other than the
wirings, and thereby the signal charges corresponding to the amount
of the incident light are generated by the light receiving
sections.
[0017] According to the light detector of the present invention, it
is possible to suppress a decrease in the area of each of light
receiving sections with an increase in the number of wirings and
thereby suppress a reduction in light detection efficiency.
According to the radiation detector of the present invention, it is
possible to suppress a decrease in the area of each of light
receiving sections with an increase in the number of wirings and
thereby suppress a reduction in radiation detection efficiency.
According to the radiation tomography apparatus of the present
invention, it is possible to suppress a decrease in the area of
each of light receiving sections with an increase in the number of
wirings and thereby suppress a reduction in radiation detection
efficiency. Further objects and advantages of the present invention
will be apparent from the following description of the preferred
embodiments of the invention as illustrated in the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a schematic configurational view of a radiation
tomography apparatus according to the present embodiment.
[0019] FIG. 2 is a view showing detailed configurations of an X-ray
tube and an X-ray detector.
[0020] FIG. 3(a) is a cross-sectional view of one X-ray detection
module as view in a y-z plane, and FIG. 3(b) is a plan view of the
X-ray detection module, respectively.
[0021] FIG. 4 is a plan view for describing the layout of
photodiodes and wirings formed in a substrate.
[0022] FIG. 5 is a cross-sectional view corresponding to line A-A'
of FIG. 4.
[0023] FIG. 6(a) is a fragmentary plan view for describing
connections of wirings and photodiodes, and FIG. 6(b) is a
cross-sectional view taken along line B-B' of FIG. 6(a),
respectively.
[0024] FIG. 7 is a fragmentary plan view of a conventional X-ray
detector.
[0025] FIG. 8 is a fragmentary plan view for describing problems of
the conventional X-ray detector with an increase in the number of
wirings.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Embodiments of the present invention will hereinafter be
described with reference to the accompanying drawings.
[0027] FIG. 1 is a schematic configurational view of a radiation
tomography apparatus (X-ray CT apparatus) according to an
embodiment. The X-ray CT apparatus 100 according to the present
embodiment is equipped with an operating console 1, an imaging
table 10 and a scanning gantry 20.
[0028] The operating console 1 is provided with an input device 2
which receives an input from an operator, a central processing unit
3 which executes an image reconstructing process or the like, a
data acquisition buffer 5 which collects projection data obtained
by the scanning gantry 20, a CRT 6 which displays a CT image
reconstructed from the projection data, and a memory device 7 which
stores programs, data and an X-ray CT image therein.
[0029] The imaging table 10 includes a cradle 12 which carries a
subject placed thereon in a bore (cavity portion) of the scanning
gantry 20 and carries out it therefrom. The cradle 12 is elevated
by a motor built in the imaging table 10 and moves linearly along
the table.
[0030] The scanning gantry 20 is provided with an X-ray tube (X-ray
irradiating means) 21, an X-ray controller 22, a collimator 23, an
X-ray detector (radiation detector) 24, a data acquisition system
(DAS) 25, a rotating section controller 26 which rotates the X-ray
tube 21 or the like about a body axis of the subject, and a control
controller 29 which performs a transfer of a control signal or the
like between the operating console 1 and the imaging table 10.
[0031] A configuration of the X-ray CT apparatus according to the
present embodiment is generally as described above. In the X-ray CT
apparatus having the above configuration, the collection of
projection data is performed in the following manner, for
example.
[0032] The position of the subject as viewed in a z-axis direction
is fixed in a state in which the subject is placed in the cavity
portion of a rotating section 15 of the scanning gantry 20. An
X-ray beam from the X-ray tube 21 is applied to the subject
(projection of X-rays), and the X-rays transmitted through the
subject are detected by the X-ray detector 24. Then, the detection
of the transmitted X-rays is performed such that data corresponding
to 360.degree. are collected in directions of plural N (e.g.,
N=1,000) views while the X-ray tube 21 and the X-ray detector 24
are being rotated about the subject (i.e., a projection angle (view
angle) is being changed).
[0033] The detected respective transmitted X-rays are converted
into digital values by the DAS (Data Acquisition System) 25, which
in turn are transferred to the operating console 1 via the data
acquisition buffer 5 as projection data. This operation is called
"one scan". A scan position is sequentially moved a predetermined
amount in the z-axis direction (slice direction and body axial
direction) and the next scan is performed. Such a scan system is
called a conventional scan system (or axial scan system). However,
a system for moving the imaging table 10 at a predetermined speed
in synchronization with a change in the projection angle and
collecting projection data while a scan position is being moved
(the X-ray tube 21 and the X-ray detector 24 helically orbit around
the subject), is referred to as a so-called helical scan system.
The present invention can be applied even to both of the
conventional scan system and the helical scan system.
[0034] The operating console 1 stores the projection data
transferred from the scanning gantry 20 in the memory device 7.
Further, the operating console 1 performs, for example, a
predetermined reconstruction function and a superposition
arithmetic operation and thereby reconstructs a tomographic image
according to a back projection process. Here, the operating console
1 is capable of reconstructing a tomographic image in real time on
the basis of the projection data sequentially transferred from the
scanning gantry 20 during scan processing and always displaying the
latest tomographic image on the CRT 6. Further, the operating
console 1 invokes the projection data stored in the memory device 7
to thereby enable an image reconstruction anew.
[0035] FIG. 2 is a diagram showing detained configurations of the
X-ray tube 21 and the X-ray detector 24.
[0036] As shown in FIG. 2, the X-ray detector 24 is configured in
such a manner that a plurality of X-ray detection modules 240 are
arranged on a circular arc with the X-ray tube 21 as the center. As
described above, the X-ray tube 21 and the X-ray detector 24 rotate
around the subject within an x-y plane, for example. In the
specification of the present application, the positional
relationship between the X-ray detection modules 240 at the central
portion of the X-ray detector 24 is used to refer to an arcuate
direction, i.e., an x direction of the X-ray detector 24 as a
channel direction. Incidentally, the z direction corresponds to the
slice direction (body axial direction).
[0037] FIG. 3(a) is a cross-sectional view of one X-ray detection
module 240 as viewed in a y-z plane, and FIG. 3(b) is a plan view
of the X-ray detection module 240, respectively.
[0038] As shown in FIG. 3, the X-ray detection module 240 is
configured in such a manner that a substrate 242 made up of silicon
or the like is attached onto a central portion of a circuit board
241 comprising a ceramic board formed with wirings, for
example.
[0039] The substrate 242 is formed with photodiodes 243 in matrix
form. Each of the photodiodes 243 comprises a p type impurity
region formed in an n-type substrate 242, for example. A signal
charge corresponding to the amount of incident light is generated
within the substrate and captured by the corresponding photodiode
243.
[0040] Scintillators 246 fixed to the substrate 242 with an
unillustrated transparent adhesive interposed therebetween are
provided over the substrate 242 so as to correspond to the
photodiodes 243 respectively. Each of the scintillators 246
comprises a fluorescent material which reacts with an incident
X-ray and thereby generates light having a wavelength longer than
that of an X-ray, i.e., light in a substantially visible region
which enables the generation of a signal charge by the
photodiode.
[0041] A reflection layer 247 is formed so as to cover the
scintillators 246 on the X-ray incident side from above and between
the scintillators 246. The reflection layer 247 is made up of, for
example, TiO.sub.2 which causes the X-rays to pass therethrough and
reflects lights emitted from the scintillators 246.
[0042] Interconnections or wirings to be described later formed in
the substrate 242 are drawn out to both ends of the substrate 242
and connected to their corresponding circuits of the circuit board
241 at both ends by wires.
[0043] FIG. 4 is a plan view for describing the layout of the
photodiodes 243 and wirings 245 formed in the substrate 242.
[0044] As shown in FIG. 4, the wirings 245 made of aluminum or the
like are connected to their corresponding photodiodes 243 to fetch
signal charges from the photodiodes 243 arranged in matrix form.
The wirings 245 are formed between the photodiodes 243 and the
scintillators 246 respectively. Although only one side, i.e., the
left side of a boundary line M at the central portion of a matrix
of the photodiodes 243 is illustrated in FIG. 4, photodiodes 243
are arranged even on the right side in a manner similar to it.
[0045] On the one side (left side) of the boundary line M, the
wirings 245 respectively connected to the photodiodes 243, which
have been arranged in matrix form, are drawn to the left end (one
end) of the substrate 242. The wirings 245 are roughly divided into
wirings 245a disposed between the photodiodes 243 and wirings 245b
disposed so as to overlap with other photodiodes 243. Incidentally,
particularly when it is not necessary to distinguish between the
wirings 245a and the wirings 245b, they are simply called the
wirings 245.
[0046] In the present embodiment, the wirings connected to the
photodiodes 243 on the center side (side close to the boundary line
M) of the matrix extend in a z direction among the photodiodes 243
arranged in a column direction (x direction) and are drawn to the
end of the substrate 242.
[0047] The wirings 245b connected to the photodiodes 243 on the end
side of the matrix extend in the z direction so as to overlap with
the photodiodes 243 adjacent to one another in the z direction and
are drawn to the end of the substrate 242.
[0048] Incidentally, although not shown in the drawing, wirings 245
respectively connected to the photodiodes 243 are drawn to the
other end (right end) of the substrate in like manner even on the
other side, i.e., right side of the boundary line M at the central
portion of the matrix.
[0049] FIG. 5 is a cross-sectional view corresponding to line A-A'
of FIG. 4.
[0050] As shown in FIG. 5, photodiodes 243 each comprising a p-type
impurity region are formed in a substrate 242 on a circuit board
241, which is made of n-type silicon, for example. Incidentally,
described more specifically, a region with a pn junction as the
center serves as a photodiode.
[0051] An insulating film 244 made of, for example, silicon oxide
or the like is formed over the photodiodes 243, and wirings 245 are
formed over the insulating film 244. The insulating film 244 holds
insulation between the photodiodes 243 other than those intended
for connection and the wirings 245.
[0052] Scintillators 246 are fixed onto the substrate 242 formed
with the wirings 245 with a transparent adhesive 248 interposed
therebetween, and a reflection layer 247 is formed so as to cover
the scintillators 246.
[0053] As shown in FIG. 5, some wirings 245b of the wirings 245,
which are respectively located between the photodiodes 243 and the
scintillators 246, are formed over the photodiodes 243, whereas the
other wirings 245a thereof are formed over a region between the
adjacent photodiodes 243 and 243.
[0054] FIG. 6(a) is a fragmentary plan view for describing
connections between wirings and photodiodes, and FIG. 6(b) is a
cross-sectional view taken along line B-B' of FIG. 6(a),
respectively.
[0055] As shown in FIG. 6, connecting holes are defined in an
insulating film 244 lying over photodiodes 243, and a wiring
material such as aluminum is embedded into each of the connecting
holes, whereby connecting portions 245c for connecting wirings 245
and their corresponding photodiodes 243 are formed.
[0056] The connecting portions 245c may be configured integrally
with the wirings 245b made of aluminum or the like. Alternatively,
the connecting portions 245c may be constituted of a material
different from the wiring material so as to be embedded into the
connecting holes. Incidentally, the connections of wirings 245a and
their corresponding photodiodes 243 are also similar to the
above.
[0057] The operation of the X-ray detector 24 will be
explained.
[0058] X-rays, which pass through a subject and are thereby
decayed, are launched into their corresponding scintillators 246,
so lights are emitted from the scintillators 246. The lights
emitted from the scintillators 246 enter the photodiodes 243.
[0059] When the lights enter into the photodiodes 243, signal
charges are produced, which in turn are captured by the photodiodes
243. The signal charges captured by the photodiodes 243 are fetched
out to the end of the substrate 242 through the wirings 245,
followed by being transmitted to a detection circuit of the circuit
board 241 via the wires.
[0060] Since the X-ray detection modules 240 are arranged in large
numbers adjacent to one another in the channel direction (x
direction) as shown in FIG. 2, the signal charges are taken out
every channels in the z direction (slice direction) different from
their arrangement or layout direction (x direction).
[0061] Since the light input is smaller because of structure of
scintillator 246 and reflector 247 and also the probability that
the signal charge will reach the region of each photodiode 243 is
low even if the signal charge occurs, in the region between the
photodiode 243 and the photodiode 243 upon the operation of the
X-ray detector 24, light is not detected very efficiently. Thus,
the area of the photodiode 243 may preferably be wide to capture
the signal charge produced in the photodiode 243 with
efficiency.
[0062] When it is necessary to form the number of wirings larger
than the number of wirings reasonably formable in the regions among
the photodiodes 243, the wirings are caused to lead so as to
overlap with the peripheral photodiodes 243 and configured so as to
take out the signal charges in the z direction (slice
direction).
[0063] Thus, since the photodiodes 243 exist among the wirings,
although the light is cut off by the wirings per se, the detection
of light at their portions is ensured. Therefore, fine or narrow
wirings are no longer used at random and a reduction in light
detection efficiency can be suppressed to the minimum.
[0064] The reflection layer 247 is formed so as to cover the
scintillators 246. Therefore, if the light is reflected by each of
the wirings 245b on the photodiodes 243, the light is reflected by
the reflection layer 247 and enters each photodiode 243. Thus, it
is possible to prevent a reduction in light detection efficiency
due to the existence of the wirings 245b on the photodiodes
243.
[0065] As shown in FIG. 4, the wirings connected to the photodiodes
243 on the center side (side close to the boundary line M) of the
matrix are placed so as to extend in the z direction among the
photodiodes 243 by priority. Further, the wirings 245b connected to
the photodiodes 243 on the end side of the matrix are disposed in
the form extended in the z direction so as to overlap with the
photodiodes 243 adjacent to one another in the z direction, whereby
the number of the photodiodes 243 on which the wirings 245b are
superimposed, can be suppressed as much as possible. Therefore, it
is possible to suppress a reduction in light detection efficiency
due to the wirings 245b.
[0066] According to a radiation detector according to the present
embodiment, as described above, it is possible to suppress a
reduction in the area of a light receiving section with an increase
in the number of wirings and suppress a decrease in radiation
detection efficiency. Thus, according to a radiation tomography
apparatus that adopts the radiation detector according to the
present embodiment, it is possible to suppress a reduction in the
area of a light receiving section with an increase in the number of
wirings and suppress a decrease in radiation detection
efficiency.
[0067] The present invention is not limited to the description of
the present embodiment. Although the present embodiment has
explained the radiation detector and the radiation tomography
apparatus, the present invention is applicable even to a light
detector free of scintillators. Even in this case, it is possible
to suppress a decrease in the area of a light receiving section
with an increase in the number of wirings and suppress a reduction
in light detection efficiency. Numerical values and materials
mentioned in the present embodiment are illustrated by way of
example. They are not necessarily limited to the illustrated ones.
Many widely different embodiments of the invention may be
configured without departing from the spirit and the scope of the
present invention. It should be understood that the present
invention is not limited to the specific embodiments described in
the specification, except as defined in the appended claims.
* * * * *