U.S. patent application number 14/502690 was filed with the patent office on 2015-04-23 for ceramic scintillator body and scintillation device.
The applicant listed for this patent is Centre National de la Recherche Scientifique, Saint-Gobain Ceramics & Plastics, Inc.. Invention is credited to Qiwei Chen, Anne B. Hardy, Brian C. LaCourse, Xiaofeng Peng, Helene Laetitia Retot, Bruno Viana, Morteza Zandi.
Application Number | 20150108404 14/502690 |
Document ID | / |
Family ID | 42310565 |
Filed Date | 2015-04-23 |
United States Patent
Application |
20150108404 |
Kind Code |
A1 |
LaCourse; Brian C. ; et
al. |
April 23, 2015 |
Ceramic Scintillator Body and Scintillation Device
Abstract
A polycrystalline ceramic scintillator body includes a ceramic
scintillating material comprising an oxide of gadolinium (Gd) and a
second rare earth element (Re). The ceramic scintillating material
has a composition, expressed in terms of molar percentage of oxide
constituents, that includes greater than fifty-five percent (55%)
Gd.sub.2O.sub.3 and a minority percentage of Re.sub.2O.sub.3. The
ceramic scintillating material includes an activator.
Inventors: |
LaCourse; Brian C.;
(Pepperell, MA) ; Hardy; Anne B.; (Acton, MA)
; Retot; Helene Laetitia; (Avignon, FR) ; Chen;
Qiwei; (Shanghai, CN) ; Peng; Xiaofeng;
(Shanghai, CN) ; Viana; Bruno; (Montgeron, FR)
; Zandi; Morteza; (Webster, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Saint-Gobain Ceramics & Plastics, Inc.
Centre National de la Recherche Scientifique |
Worcester
Paris |
MA |
US
FR |
|
|
Family ID: |
42310565 |
Appl. No.: |
14/502690 |
Filed: |
September 30, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13142756 |
Nov 9, 2011 |
8877093 |
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PCT/US2009/069538 |
Dec 24, 2009 |
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14502690 |
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61141564 |
Dec 30, 2008 |
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Current U.S.
Class: |
252/301.4R |
Current CPC
Class: |
C09K 11/7766 20130101;
C04B 2235/3224 20130101; C04B 2235/9653 20130101; C04B 2235/3227
20130101; C09K 11/7769 20130101; C04B 35/6455 20130101; C04B
2235/77 20130101; C04B 35/50 20130101; C04B 2235/658 20130101; C04B
2235/6567 20130101; B82Y 30/00 20130101; C04B 2235/3225 20130101;
C04B 2235/5454 20130101 |
Class at
Publication: |
252/301.4R |
International
Class: |
C09K 11/77 20060101
C09K011/77 |
Claims
1. A scintillation device comprising: a polycrystalline ceramic
scintillator body, comprising: a ceramic scintillating material
comprising Gd.sub.2O.sub.3 and Re.sub.2O.sub.3, where Re is a
second rare earth element distinct from Gd, the ceramic
scintillating material having a composition, expressed in terms of
molar percentage of oxide constituents, including greater than
sixty-six percent (66%) Gd.sub.2O.sub.3 and a minority percentage
of Re.sub.2O.sub.3, wherein the ceramic scintillating material
includes an activator.
2. The scintillation device of claim 1, wherein Re.sub.2O.sub.3
comprises Lu.sub.2O.sub.3, Y.sub.2O.sub.3, or La.sub.2O.sub.3.
3. The scintillation device of claim 1, wherein the activator
includes a rare earth element.
4. The scintillation device of claim 1, wherein the activator
comprises less than or equal to five percent of the composition
based on molar percentage.
5. The scintillation device of claim 4, wherein the activator
comprises less than or equal to two percent of the composition
based on molar percentage.
6. The scintillation device of claim 1, wherein the ceramic
scintillating material includes more than one second rare earth
elements that are distinct from Gd.
7. The scintillation device of claim 1 wherein the scintillator
body is characterized by a decay time of less than 1 ms.
8. The scintillation device of claim 7, wherein the scintillator
body is characterized by a decay time of less than or equal to
approximately 0.5 ms.
9. The scintillation device of claim 8, wherein the scintillator
body is characterized by a decay time of less than or equal to
approximately 0.1 ms.
10. The scintillation device of claim 1, wherein the scintillator
body is characterized by a density of at least 99.9% of theoretical
density.
11. The scintillation device of claim 1, wherein the composition of
the ceramic scintillating material, expressed in terms of molar
percentage of oxide constituents, includes at least five percent
(5%) Re.sub.2O.sub.3.
12. A ceramic scintillating powder comprising a ceramic
scintillating material comprising Gd.sub.2O.sub.3 and
Re.sub.2O.sub.3, where Re is a second rare earth element distinct
from Gd, the ceramic scintillating material having a composition
including, expressed in terms of molar percentage of oxide
constituents, greater than sixty-six percent (66%) Gd.sub.2O.sub.3
and a minority percentage of Re.sub.2O.sub.3, wherein the ceramic
scintillating material includes an activator.
13. The ceramic scintillating powder of claim 12, wherein the
activator comprises a rare earth element.
14. The ceramic scintillating powder of claim 12, wherein the
ceramic scintillating material comprises a plurality of
substantially spherical particles and wherein at least ninety
percent of the particles are characterized by a particle size of
from approximately 50 nm to approximately 250 nm.
15. The ceramic scintillating powder of claim 14, wherein at least
ninety percent of the particles are characterized by a particle
size of from approximately 66 nm to approximately 220 nm.
16. A computed-tomography (CT) apparatus comprising: an array of
scintillating devices, wherein each of the scintillating devices
includes a polycrystalline ceramic scintillator body comprising: a
ceramic scintillating material comprising Gd.sub.2O.sub.3 and
Re.sub.2O.sub.3, where Re is a second rare earth element distinct
from Gd, the ceramic scintillating material having a composition,
expressed in terms of molar percentage of oxide constituents,
including greater than sixty-six percent (66%) Gd.sub.2O.sub.3 and
a minority percentage of Re.sub.2O.sub.3; wherein the ceramic
scintillating material includes an activator.
17. The CT apparatus of claim 16, wherein the activator comprises a
rare earth element.
18. The CT apparatus of claim 16, wherein the scintillator body is
characterized by a decay time of less than or equal to
approximately 1 ms.
19. The CT apparatus of claim 16, wherein the scintillator body is
characterized by a decay time of less than or equal to
approximately 0.1 ms.
20. The CT apparatus of claim 16, wherein the scintillator body has
a density of at least 99.9% of theoretical density.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation application of and claims
priority under 35 U.S.C. .sctn.120 to U.S. patent application Ser.
No. 13/142,756, filed Nov. 9, 2011, entitled "CERAMIC SCINTILLATOR
BODY AND SCINTILLATION DEVICE" by LaCourse et al, which is the
National Stage of and claims priority to International Application
No. PCT/US09/69538, filed Dec. 24, 2009, entitled "CERAMIC
SCINTILLATOR BODY AND SCINTILLATION DEVICE" by LaCourse et al,
which claims priority under 35 U.S.C. .sctn.119(e) to U.S. Patent
Application No. 61/141,564 entitled "CERAMIC SCINTILLATOR BODY AND
SCINTILLATION DEVICE", by LaCourse et al., filed Dec. 30, 2008, all
of which are assigned to the current assignee hereof and
incorporated herein by reference in their entirety.
FIELD OF THE DISCLOSURE
[0002] The present disclosure is directed to scintillation devices,
particularly scintillation devices for industrial applications, and
to ceramic scintillator bodies.
BACKGROUND
[0003] Scintillation devices are used in a variety of industrial
applications. For example, scintillation devices are used for well
logging in the oil and gas industry and for imaging scans in the
medical field. Typically, scintillation devices include
scintillator bodies, such as a scintillator crystal, produced from
a material that is effective to detect gamma rays, x-rays,
ultraviolet radiation or other radiation. The scintillator bodies
can absorb x-rays or other radiation and emit light. The emitted
light can sometimes be recorded on film. Generally, the
scintillator bodies are enclosed in casings or sleeves that include
a window to permit radiation-induced scintillation light to pass
out of the crystal package. The light passes to a light-sensing
device such as a photomultiplier tube, a photodiode, or another
photosensor that converts the light emitted from the scintillator
body into electrical pulses. In other applications, multiple
scintillator bodies can be used in imaging arrays for medical
imaging equipment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The present disclosure may be better understood, and its
numerous features and advantages made apparent to those skilled in
the art by referencing the accompanying drawings.
[0005] FIG. 1 is a block diagram illustrating a particular
embodiment of a radiation detector device;
[0006] FIG. 2 is a block diagram illustrating a particular
embodiment of x-ray computed tomography scanning equipment; and
[0007] FIG. 3 is a flow diagram illustrating a method of producing
a ceramic scintillator body.
[0008] The use of the same reference symbols in different drawings
indicates similar or identical items.
DETAILED DESCRIPTION
[0009] Numerous innovative teachings of the present application
will be described with particular reference to exemplary
embodiments. However, it should be understood that this class of
embodiments provides only a few examples of the many advantageous
uses of the innovative teachings herein. In general, statements
made in the specification of the present application do not
necessarily limit any of the various claimed articles, systems, or
methods. Moreover, some statements may apply to some inventive
features but not to others.
[0010] The demands of well logging and medical imaging benefit from
scintillation devices that are accurate under harsh and fast
conditions. Various classes of scintillating materials can be used
to produce scintillator bodies depending on intended applications.
For example, single crystal oxyorthosilicates, such as lutetium
yttrium oxyorthosilicate (LYSO), are often used in medical imaging
applications, such as positron emission tomography (PET). These
materials are typically characterized by relatively high stopping
power and fast decay times. Nonetheless, LYSO is often
characterized by low light output, and performance in PET scan
applications can suffer from electron emission resulting from the
.beta..sup.- decay of lutetium.
[0011] Another class of scintillating materials includes ceramic
rare earth sulfoxylates, such as gadolinium oxysulfide (GOS).
Ceramic materials such as GOS can be less costly than single
crystal materials, such as LYSO. However, the hexagonal structure
of ceramic rare earth sulfoxylates often causes "birefringence," or
light scattering at grain boundaries. As a result, such materials
are less transparent and exhibit less light output or brightness
than many single crystal materials. Consequently, improvements in
scintillator efficiency and brightness that might be caused by the
compatibility of ceramic rare earth sulfoxylates with certain
activators are typically diminished by the reduced transparency
that results from their hexagonal structures.
[0012] FIG. 1 shows a particular embodiment of a radiation detector
device 100. The radiation detector device 100 includes a
photosensor 101, a light pipe 103, and a scintillation device 105.
Though the photosensor 101, the light pipe 103, and the
scintillation device 105 are illustrated separately from each
other, it is to be understood that the photosensor 101 and the
scintillation device 105 are adapted to be coupled to each other
via the light pipe 103.
[0013] In one embodiment, the photosensor 101 includes a device
capable of spectral detection and resolution. For example, the
photosensor 101 can comprise a conventional photomultiplier tube
(PMT), a hybrid photodetector, or a photodiode. The photosensor 101
is adapted to receive photons emitted by the scintillation device
105 after absorbing x-rays or other radiation, and the photosensor
101 is adapted to produce electrical pulses or imaging signals from
photons that it receives.
[0014] The electronics 130 can include one or more electronic
devices, such as an amplifier, a pre-amplifier, a discriminator, an
analog-to-digital signal converter, a photon counter, another
electronic device, or any combination thereof. The photosensor 101
can be housed within a tube or housing made of a material capable
of protecting electronics associated with the photosensor 101, such
as a metal, metal alloy, other material, or any combination
thereof.
[0015] As illustrated, the light pipe 103 is disposed between the
photosensor 101 and the scintillation device 105 and facilitates
optical coupling between the photosensor 101 and the scintillation
device 105. In one embodiment, the light pipe 103 can include a
quartz light pipe, plastic light pipe, or another light pipe. In
another embodiment, the light pipe 103 can comprise a silicone
rubber interface that optically couples an output window 119 of the
scintillation device 105 with an input window of the photosensor
101. In some embodiments, multiple light pipes can be disposed
between the photosensor 101 and the scintillation device 105.
[0016] The scintillation device 105 includes a scintillator body
107 housed within a casing 115. The scintillator body 107 can have
various shapes, such as a rectangular shape, or a cylindrical
surface including flat end faces. It will be appreciated that the
surface finish of the scintillator body 107 can be sanded,
polished, ground, etc., as desired.
[0017] The scintillator body 107 has a length that extends from a
first end that is proximal to the photosensor 101 and a second end
that is distal from the photosensor 101. The scintillation device
105 also includes a reflector 109 substantially surrounding the
scintillator body 107. In addition, the scintillation device 105
can include a boot 111 that acts as a shock absorber to prevent
damage to the scintillator body 107. The boot 111 can comprise a
polymer, such as silicone rubber, another material, or a
combination thereof. Further, the scintillation device 105 can also
include a casing 113.
[0018] In a particular embodiment, the scintillator body 107 is a
polycrystalline ceramic scintillator body that includes a ceramic
scintillating material that comprises an oxide of gadolinium and a
second rare earth element. Expressed in terms of oxide
constituents, gadolinium oxide (Gd.sub.2O.sub.3) is a primary
component of the composition and comprises greater than fifty-five
percent of the composition based on molar percentage. For instance,
gadolinium oxide can comprise at least fifty-seven percent (57%) of
the composition based on molar percentage, such as greater than or
equal to approximately sixty percent (60%) of the composition based
on molar percentage, or greater than or equal to approximately
two-thirds of the composition based on molar percentage.
[0019] Expressed in terms of oxide constituents, a second rare
earth oxide (Re.sub.2O.sub.3) is a secondary component of the
composition and comprises a minority percentage of the composition
based on molar percentage. The second rare earth oxide has a
distinct composition from gadolinium oxide (Gd.sub.2O.sub.3). For
example, the second rare earth oxide can include lutetium oxide
(Lu.sub.2O.sub.3), yttrium oxide (Y.sub.2O.sub.3), lanthanum oxide
(La.sub.2O.sub.3), or another rare earth oxide distinct from
gadolinium oxide. In another example, the scintillating material
can include multiple second compounds, such as a combination of
second rare earth oxides. In one embodiment, the composition of the
ceramic scintillating material includes at least five percent (5%)
Re.sub.2O.sub.3.
[0020] In a particular embodiment, the composition also includes an
activator. The activator causes the scintillator body 107 to emit
visible light after absorbing gamma radiation, x-rays, ultraviolet
radiation, or other radiation. The activator can include a rare
earth element, such as a lanthanide element. For example, the
activator can include praseodymium. In an illustrative embodiment,
the activator can comprise less than ten percent (10%) of the
composition, such as less than or equal to approximately five
percent (5%) or less than or equal to approximately two percent
(2%) of the composition based on molar percentage. In a particular
embodiment, the scintillator body is characterized by a decay time
of less than 1 ms, such as less than or equal to approximately 0.5
ms or less than or equal to approximately 0.1 ms.
[0021] The scintillator body 107 can be characterized by a density
of at least 99.9% of theoretical density. In addition, the
scintillator body 107 can be characterized by a scintillating
efficiency of at least eight percent.
[0022] FIG. 2 illustrates a particular embodiment of x-ray
equipment 200, such as x-ray computed tomography (CT) equipment.
The x-ray scanning equipment 200 includes an array 202 of
scintillator devices, or pixels, and a segmented photodetector 210.
The x-ray scanning equipment 200 also includes an x-ray source 206
adapted to emit x-rays 204, e.g., in a fan-shaped or cone-shaped
pattern. The x-ray source 206 and the array 202 of scintillator
devices may be adapted to rotate about an object 208. For example,
the x-ray source 206 and the array 202 may be adapted to rotate
opposite each other substantially along a circle centered about the
object 208 and at substantially equal rates.
[0023] In a particular embodiment, each pixel in the array 202 can
include a scintillator body. Each scintillator body is adapted to
absorb x-rays 204 emitted by the x-ray source 206 and to emit
scintillation light 214 that feeds into the segmented photodetector
210. The segmented photodetector 210 is adapted to measure
scintillation light 214 received from each pixel and to determine
from which pixel the particular scintillation light is received.
The segmented photodetector 210 is adapted to produce signals based
on the amount of scintillation light emitted by each scintillation
device in the array 202 from various angles and to send the signals
to the computing device 212. The computing device 212 is adapted to
construct an image of the object 208 based on the signals received
from the segmented photodetector 210.
[0024] In a particular embodiment, each scintillator body is a
polycrystalline ceramic scintillator body formed from a composition
that includes a ceramic scintillating material that comprises an
oxide of gadolinium and a second rare earth element. Expressed in
terms of oxide constituents, gadolinium oxide (Gd.sub.2O.sub.3) is
a primary component of the composition and comprises greater than
fifty-five percent of the composition based on molar percentage.
For instance, gadolinium oxide can comprise at least fifty-seven
percent (57%) of the composition based on molar percentage, such as
greater than or equal to approximately sixty percent (60%) of the
composition based on molar percentage, or greater than or equal to
approximately two-thirds of the composition based on molar
percentage.
[0025] Expressed in terms of oxide constituents, a second rare
earth oxide (Re.sub.2O.sub.3) is a secondary component of the
composition and comprises a minority percentage of the composition
based on molar percentage. The second rare earth oxide has a
distinct composition from gadolinium oxide (Gd.sub.2O.sub.3). For
example, the second rare earth oxide can include lutetium oxide
(Lu.sub.2O.sub.3), yttrium oxide (Y.sub.2O.sub.3), lanthanum oxide
(La.sub.2O.sub.3), or another rare earth oxide distinct from
gadolinium oxide. In another example, the scintillating material
can include multiple second compounds, such as a combination of
second rare earth oxides. In one embodiment, the composition of the
ceramic scintillating material includes at least five percent (5%)
Re.sub.2O.sub.3.
[0026] In a particular embodiment, the composition also includes an
activator. The activator can include a rare earth element, such as
a lanthanide element. For example, the activator can include
praseodymium. In an illustrative embodiment, the activator can
comprise less than ten percent (10%) of the composition, such as
less than or equal to approximately five percent (5%) or less than
or equal to approximately two percent (2%) of the composition based
on molar percentage. In a particular embodiment, the scintillator
body is characterized by a decay time of less than 1 ms, such as
less than or equal to approximately 0.5 ms or less than or equal to
approximately 0.1 ms. Each scintillator body can be characterized
by a density of at least 99.9% of theoretical density.
[0027] FIG. 3 illustrates a particular embodiment of a method of
producing a ceramic scintillator body. At block 300, a precipitant
solution of ammonium hydroxide and ammonium bicarbonate is
prepared. Moving to block 302, a precursor solution of lutetium
nitrate, gadolinium nitrate and praseodymium nitrate is prepared.
Proceeding to block 304, the precursor solution is titrated into
the precipitant solution to form a precipitate. Continuing to block
306, the precipitate is filtered and washed, and a precipitate wet
cake is obtained. For example, the precipitate can be washed using
deionized water until a desired conductivity value of residual ions
is reached. In another example, the precipitate can also be washed
with ethanol to prevent agglomeration during drying.
[0028] Advancing to block 308, the precipitate wet cake is dried to
obtain a precipitate dry cake. At block 310, the precipitate dry
cake is calcined to obtain a scintillating powder having a
composition represented by the general formula La.sub.2O.sub.3:Pr.
Moving to block 312, the calcined powder can be formed into ceramic
scintillator bodies by first die pressing the powder into pellets
and then cold isostatic pressing the pellets. Proceeding to block
314, the pressed pellets are sintered to obtain sintered samples,
and each sintered sample is hot isostatic pressed. Advancing to
block 316, in a particular embodiment, each sample is air annealed
to improve transparency. The method terminates at 318.
EXAMPLE
[0029] In one example, a precipitant solution of ammonium hydroxide
(NH4OH) and ammonium bicarbonate (NH4HCO3) was prepared by adding
3M NH4OH and 1M NH4HCO3 to a beaker and mixing to form a uniform
complex precipitant solution, diluted to approximately 500 ml.
Next, a solution of precursor nitrates was prepared by mixing
correct proportions of Gd(NO.sub.3).sub.3, Lu(NO.sub.3).sub.3 and
Pr(NO.sub.3).sub.3, diluted to 1.5 L. The precursor solution was
titrated into the precipitant solution to form a precipitate. The
precipitate was filtered from solution and washed with deionized
water and Ethanol.
[0030] The precipitate wet cake was dried in an oven at
approximately 60.degree. C., and the dried cake was calcined at
850.degree. C. for 2 hrs in order to form a scintillating material
having a composition of Gd.sub.2O.sub.3 and Lu.sub.2O.sub.3 doped
with Pr.
[0031] The calcined powder can be formed into ceramic scintillator
bodies by first die pressing the powder into approximately 12 mm
diameter pellets and then cold isostatic pressing the pellets to 30
ksi (2.07.times.10.sup.8 Pa). The pressed pellets were then
sintered in air at between 1500.degree. C. and 1600.degree. C. for
3 hrs. Each sintered sample was then hot isostatic pressed at
between 1400.degree. C. and 1600.degree. C. for 1 hr in Argon at 30
ksi to produce a ceramic scintillator body.
[0032] It is found that characteristics of the powder scintillating
material can affect density and transparency of the resulting
scintillator body. Some prior methods aim to produce powders having
a uniform distribution of extremely small particles one the order
of 1-5 nm in diameter, while other prior methods mix large (e.g.,
greater than 500 nm) and small (1-5 nm) sizes to attempt to fill
any gaps between particles. However, it is found that a powder
having substantially spherical particles between 10 nm and 500 nm,
with a narrow particle size distribution is advantageous. For
instance, a powder scintillating material having substantially
spherical particles, where at least ninety percent of the particles
have a size between approximately 50 nm and approximately 250 nm,
such as approximately 66 nm to approximately 220 nm, can be used to
produce a scintillator body having increased density and
transparency.
[0033] In accordance with the embodiments described herein, a
polycrystalline ceramic scintillator body includes a ceramic
scintillating material comprising an oxide of gadolinium (Gd) and a
second rare earth element (Re). The ceramic scintillating material
has a composition including, expressed in terms of molar percentage
of oxide constituents, greater than fifty-five percent (55%)
Gd.sub.2O.sub.3 and a minority percentage of Re.sub.2O.sub.3. The
ceramic scintillating material includes an activator. In a
particular embodiment, the activator can include praseodymium.
[0034] Praseodymium is not equally compatible with all scintillator
bodies. For example, praseodymium often suffers from performance
drawbacks when used with rare earth scintillating materials having
short atomic distances. These short atomic distances can cause
non-radiative relaxation of praseodymium, thereby reducing light
output and scintillator efficiency. The presence of sulfur in
gadolinium sulfoxylate (GOS) and other rare earth sulfoxylates
increases atomic distances and prevents non-radiative relaxation of
praseodymium. However, the hexagonal structure of rare earth
sulfoxylates tends to reduce transparency and, hence, brightness
and scintillator efficiency. In addition, GOS and other rare earth
sulfoxylates can be more expensive to produce than gadolinium
oxide, for example.
[0035] Scintillating materials produced from many rare earth oxides
exhibit cubic lattice structures. These cubic structures contribute
to greater transparency in corresponding scintillator bodies and
reduce or eliminate birefringence. However, while some rare earth
oxides, such as gadolinium oxide, exhibit more cubic lattice
structures than rare earth sulfoxylates, their shorter atomic
distances contribute to non-radiative relaxation of praseodymium.
Hence, these rare earth oxides are typically considered less
compatible with praseodymium for scintillating purposes and are
typically used with more compatible activators, such as europium.
Gadolinium oxide is considered by the prior art to be particularly
undesirable. For example, the prior art suggests that
yttria-gadolinia scintillator bodies having mole ratios above fifty
percent (50%) of gadolinium oxide exhibit poor light output and
grain boundary cracking, because gadolinium oxide is not cubic at
room temperature. Preferred mole ratios of gadolinium oxide in the
prior art are between thirty and forty percent.
[0036] Nonetheless, it is found that scintillator bodies comprising
rare earth oxides doped with praseodymium exhibit a shorter decay
time than scintillator bodies comprising rare earth oxides doped
with other rare earth activator elements, such as europium. For
instance, decay time in rare earth oxides, such as yttria-gadolinia
oxides, doped with europium is typically on the order of 1 ms. On
the other hand, decay time in scintillator bodies produced from
materials containing a majority of gadolinium oxide and using
praseodymium as an activator can be on the order of 0.1 ms. This
faster decay time contributes to faster scan rates in medical
applications, such as computed tomography (CT).
[0037] Additionally, scintillator bodies comprising rare earth
oxides doped with praseodymium exhibit lower afterglow and residual
light than scintillator bodies comprising rare earth oxides doped
with other rare earth activators elements, such as europium.
Residual light, also known as "persistence" can affect resolution
in applications such as medical imaging by producing a "bleeding"
effect on images. The use of praseodymium as an activator can
reduce such bleeding and image artifacts and improve image
resolution in such medical applications.
[0038] Ceramic processes are preferably used to produce
scintillator bodies formed from compositions disclosed herein,
rather than traditional single crystal growth methods. Such
processes and the raw materials used enable these scintillator
bodies to be produced at lower cost than rare earth sulfoxylate
materials, such as GOS:Pr.
[0039] The illustrations of the embodiments described herein are
intended to provide a general understanding of the structure of the
various embodiments. The illustrations are not intended to serve as
a complete description of all of the elements and features of the
compositions, apparatuses, systems, or methods described herein.
Many other embodiments may be apparent to those of skill in the art
upon reviewing the disclosure. Other embodiments may be utilized
and derived from the disclosure, such that structural and logical
substitutions and changes may be made without departing from the
scope of the disclosure. Additionally, the illustrations are merely
representational and may not be drawn to scale. Certain proportions
within the illustrations may be exaggerated, while other
proportions may be minimized. Accordingly, the disclosure and the
Figures are to be regarded as illustrative rather than
restrictive.
[0040] According to a first aspect, a polycrystalline ceramic
scintillator body includes a ceramic scintillating material
comprising an oxide of gadolinium (Gd) and a second rare earth
element (Re). The ceramic scintillating material has a composition,
expressed in terms of molar percentage of oxide constituents, that
includes greater than fifty-five percent (55%) Gd.sub.2O.sub.3 and
a minority percentage of Re.sub.2O.sub.3. The ceramic scintillating
material includes an activator.
[0041] In one embodiment of the first aspect, Re.sub.2O.sub.3
comprises lutetium oxide (Lu.sub.2O.sub.3). In another embodiment
of the first aspect, Re.sub.2O.sub.3 comprises yttrium oxide
(Y.sub.2O.sub.3). In a further embodiment of the first aspect,
Re.sub.2O.sub.3 comprises lanthanum oxide (La.sub.2O.sub.3).
[0042] The activator can comprise a rare earth element, such as a
lanthanide element. For instance, the activator can include
praseodymium. In an illustrative embodiment, the activator can
comprise less than five percent of the composition based on molar
percentage, such as less than or equal to two percent of the
composition based on molar percentage.
[0043] According to a second aspect, a scintillation device
includes a polycrystalline ceramic scintillator body that includes
a ceramic scintillating material comprising an oxide of gadolinium
(Gd) and a second rare earth element (Re). The ceramic
scintillating material has a composition, expressed in terms of
molar percentage of oxide constituents, that includes greater than
fifty-five percent (55%) Gd.sub.2O.sub.3 and a minority percentage
of Re.sub.2O.sub.3 a first rare earth oxide. The ceramic
scintillating material includes an activator.
[0044] In one embodiment of the second aspect, the ceramic
scintillating material has a composition including, expressed in
terms of molar percentage of oxide constituents, at least
fifty-seven percent (57%) Gd.sub.2O.sub.3, such as at least sixty
percent (60%) Gd.sub.2O.sub.3 or at least sixty-six percent (66%)
Gd.sub.2O.sub.3.
[0045] In another embodiment of the second aspect, the activator
includes praseodymium. In yet another embodiment of the second
aspect, the scintillator body is characterized by a decay time of
less than 1 ms, such as less than or equal to approximately 0.5 ms
or less than or equal to approximately 0.1 ms.
[0046] In a further embodiment of the second aspect, the
scintillation body can be characterized by a density of at least
99.9% of theoretical density.
[0047] In a third aspect, a computed-tomography (CT) apparatus
includes an array of scintillating devices. Each of the
scintillating devices includes a polycrystalline ceramic
scintillator body comprising a ceramic scintillating material
comprising an oxide of gadolinium (Gd) and a second rare earth
element (Re). The ceramic scintillating material has a composition,
expressed in terms of molar percentage of oxide constituents, that
includes greater than fifty-five percent (55%) Gd.sub.2O.sub.3 and
a minority percentage of Re.sub.2O.sub.3. In one embodiment, the
composition of the ceramic scintillating material, expressed in
terms of molar percentage of oxide constituents, includes at least
five percent (5%) Re.sub.2O.sub.3.
[0048] According to a fourth aspect, a ceramic scintillating powder
includes a ceramic scintillating material comprising an oxide of
gadolinium (Gd) and a second rare earth element (Re). The ceramic
scintillating material has a composition including, expressed in
terms of molar percentage of oxide constituents, greater than
fifty-five percent (55%) Gd.sub.2O.sub.3 and a minority percentage
of Re.sub.2O.sub.3. The ceramic scintillating material includes an
activator.
[0049] In one embodiment of the fourth aspect, the ceramic
scintillating material comprises a plurality of substantially
spherical particles and wherein at least ninety percent of the
particles are characterized by a particle size of from
approximately 50 nm to approximately 250 nm. For example, at least
ninety percent of the particles can be characterized by a particle
size of from approximately 66 nm to approximately 220 nm.
[0050] In the foregoing Detailed Description of the Drawings,
various features may be grouped together or described in a single
embodiment for the purpose of streamlining the disclosure. This
disclosure is not to be interpreted as reflecting an intention that
the claimed embodiments require more features than are expressly
recited in each claim. Rather, as the following claims reflect,
inventive subject matter may be directed to less than all features
of any of the disclosed embodiments. Thus, the following claims are
incorporated into the Detailed Description of the Drawings, with
each claim standing on its own as defining separately claimed
subject matter.
[0051] The above disclosed subject matter is to be considered
illustrative, and not restrictive, and the appended claims are
intended to cover all such modifications, enhancements, and other
embodiments which fall within the true spirit and scope of the
present disclosed subject matter. Thus, to the maximum extent
allowed by law, the scope of the present disclosed subject matter
is to be determined by the broadest permissible interpretation of
the following claims and their equivalents, and shall not be
restricted or limited by the foregoing detailed description.
* * * * *