Title: Scintillator coatings having barrier protection, light transmission, and light reflection properties
Abstract: Scintillator coatings having predetermined barrier protection, light transmission, and light reflection properties are described. These scintillators comprise: a scintillator material comprising a barrier coating disposed thereon, wherein the barrier coating: (1) provides barrier protection to the scintillator material, (2) is capable of transmitting light therethrough, and (3) is capable of reflecting light back into the scintillator material. The barrier coating may comprise a material that has been modified to have light transmissive and reflective properties in addition to protective properties, or it may comprise a protective material and a reflective material that have been co-deposited onto the scintillator material. The barrier coating is a single coating overlying the scintillator material in a substantially conformal manner.
Patent Number: 6,996,209 Issued on 02/07/2006 to Marek
| Inventors:
|
Marek; Henry Samuel (Clifton Park, NY)
|
| Assignee:
|
GE Medical Systems Global Technology Company, LLC (Waukesha, WI)
|
| Appl. No.:
|
694271 |
| Filed:
|
October 27, 2003 |
| Current U.S. Class: |
378/98.8; 250/370.11 |
| Current Intern'l Class: |
H05G 1/64 (20060101) |
| Field of Search: |
378/988
250/370.11,368
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Church; Craig E.
Assistant Examiner: Yun; Jurie
Attorney, Agent or Firm: Dougherty Clements, Bernard; Christopher L., Vogel; Peter J.
Claims
What is claimed is:
1. A scintillator comprising:
a scintillator material comprising a single-layer barrier coating disposed thereon,
wherein the barrier coating: (1) provides barrier protection to the scintillator
material, (2) is capable of transmitting light therethrough, and (3) is capable
of reflecting light back into the scintillator material, and wherein the barrier
coating is disposed on top portions and interstitially on partial side portions
of the scintillator material, the barrier coating defining one or more voids adjacent
to other partial side portions of the scintillator material.
2. The scintillator of claim 1, wherein the barrier coating comprises a material
that has been modified to have light transmissive and reflective properties in
addition to protective properties.
3. The scintillator of claim 2, wherein the material comprises Parylene.
4. The scintillator of claim 1, wherein the barrier coating comprises a protective
material and a reflective material that have been co-deposited onto the scintillator material.
5. The scintillator of claim 4, wherein the protective material comprises Parylene.
6. The scintillator of claim 4, wherein the reflective material comprises a light
reflective material that can be co-deposited with Parylene.
7. The scintillator of claim 4, wherein the reflective material comprises at
least one of: a metal, a metal compound, a metal oxide, and a metal halide.
8. The scintillator of claim 1, wherein the scintillator material comprises at
least one of: cesium iodide, cesium iodide doped with thallium, cesium iodide doped
with sodium, sodium iodide, sodium iodide dope with thallium, lithium iodide, lithium
iodide doped with europium, zinc sulphide, zinc sulphide doped with silver, calcium
fluoride, calcium fluoride doped with europium, bismuth germinate, cesium fluoride,
anthracene, stelbene, and a silicate glass containing lithium activated with cerium.
9. The scintillator of claim 1, wherein the barrier coating is a single coating
overlying the scintillator material.
10. The scintillator of claim 1, wherein the barrier coating is disposed in a
substantially conformal manner on the scintillator material.
11. The scintillator of claim 1, wherein the barrier coating is applied overlying
the scintillator material via at least one of: chemical vapor deposition, metal
organic chemical vapor deposition, thermal evaporation, electron beam evaporation,
molecular beam evaporation, and sputtering.
12. The scintillator of claim 1, wherein the scintillator is used for at least
one of: medical imaging, nondestructive testing of parts, and detecting contraband.
13. A scintillator comprising a single-layer coating thereon that protects the
scintillator from ambient conditions, transmits light therethrough, and reflects
light back into the scintillator, wherein the coating is disposed on top portions
and interstitially on partial side portions of the scintillator, the barrier coating
defining one or more voids adjacent to other partial side portions of the scintillator.
14. The scintillator of claim 13, wherein the coating comprises at least one
of Parylene, Parylene-N, Parylene-C, Parylene-D, a metal, a metal compound, a metal
oxide, and a metal halide.
15. The scintillator of claim 13, wherein the coating is a single layer overlying
the scintillator.
16. The scintillator of claim 13, wherein the coating is disposed in a substantially
conformal manner on the scintillator.
17. The scintillator of claim 13, wherein the scintillator is used for at least
one of: medical imaging, nondestmctive testing of parts, and detecting contraband.
18. A radiation imaging system comprising:
an x-ray source;
an x-ray detector comprising:
a scintillator comprising:
a scintillator material comprising a single-layer barrier coating disposed thereon,
wherein the barrier coating: (1) provides barrier protection to the scintillator
material, (2) is capable of transmitting light therethrough, and (3) is capable
of reflecting light back into the scintillator material, and wherein the barrier
coating is disposed on top portions and interstitially on partial side portions
of the scintillator material, the barrier coating defining one or more voids adjacent
to other partial side portions of the scintillator material; and
an amorphous silicon array optically coupled to the scintillator;
wherein the x-ray source is capable of projecting a beam of x-rays towards the
x-ray detector, the x-ray detector is capable of detecting the x-rays, and an image
can be created therefrom.
19. A method for making a scintillator having a single-layer barrier coating
thereon that has both protective properties and light reflective and light transmissive
properties, the method comprising:
disposing an amorphous silicon array on a detector substrate;
disposing a scintillator material on the amorphous silicon array;
forming a single-layer barrier coating on the scintillator material;
wherein the barrier coating: (1) provides barrier protection to the scintillator
material, (2) is capable of transmitting light therethrough, and (3) is capable
of reflecting light back into the scintillator material, and wherein the barrier
coating is disposed on top portions and interstitially on partial side portions
of the scintillator material, the barrier coating defining one or more voids adjacent
to other partial side portions of the scintillator material.
20. The method of claim 19, wherein disposing the scintillator material on the
amorphous silicon array comprises growing the scintillator material directly on
the amorphous silicon array.
21. The method of claim 19, wherein forming the barrier coating on the scintillator
material comprises depositing the barrier coating onto the scintillator material
via at least one of: chemical vapor deposition, metal organic chemical vapor deposition,
thermal evaporation, electron beam evaporation, molecular beam evaporation, and sputtering.
22. The method of claim 21, wherein the barrier coating is deposited onto the
scintillator material in a substantially conformal manner.
Description
FIELD OF THE INVENTION
The present invention relates generally to radiation imaging. More specifically,
the present invention relates to scintillators with coatings having barrier protection,
light transmission, and light reflection properties, wherein the scintillators
are useful for radiation imaging.
BACKGROUND OF THE INVENTION
With applications ranging from diagnostic procedures to radiation therapy, the
importance of high-performance medical imaging is immeasurable. As such, new advanced
medical imaging technologies continue to be developed. Some such imaging systems
utilize amorphous silicon flat panel x-ray detectors.
Generally, in amorphous silicon flat panel x-ray detectors, an amorphous
silicon array is disposed on a glass substrate, and a scintillator is disposed
over, and is optically coupled to, the amorphous silicon array. An x-ray source
emits a beam of x-rays towards the scintillator, which absorbs the x-ray photons
and converts them to visible light. The amorphous silicon array then detects the
visible light and converts it into electrical charge. The electrical charge at
each pixel on the amorphous silicon array is read out digitally by low-noise electronics,
and is then sent to an image processor. Thereafter, the image is displayed on a
display, and may also be stored in memory for later retrieval.
Scintillators generally comprise materials that are matched to the
type of radiation being used. Cesium iodide is one typical material that medical
radiation imaging scintillators may comprise. Cesium iodide is an inorganic compound
that is grown on the device, in the form of needles, by chemical vapor deposition.
Cesium iodide is a hygroscopic, air sensitive, oxidizing material, and therefore,
requires a protective barrier coating thereon to prevent the cesium iodide from
deteriorating upon contact with ambient conditions. Typically, this protective
barrier coating comprises a transparent non-reflective material, such as, for example,
Parylene-N, Parylene-C, or Parylene-D. Additionally, a reflective layer is also
generally required on top of the coated cesium iodide needles, to improve the light
reflection and/or light conducting properties of the cesium iodide needles, and
to reflect the light back into the needles and prevent it from scattering out therefrom,
thereby improving the device performance. Typically, this reflective layer comprises
a sheet of material, such as Opticlad; a white colored, highly reflective plastic
material that is placed on top of the coated cesium iodide layer.
Since existing scintillators require both a protective barrier coating and
a reflective layer of some sort, it would be desirable to have protective barrier
coatings that are also reflective coatings, so that a single coating or layer could
be used as both a protector and a reflector. It would also be desirable to co-deposit
a protective barrier coating and a reflective coating at the same time, so as to
minimize the number of processing steps that are required to manufacture the scintillators,
thereby resulting in a single coating or layer that acts as both a protector and
a reflector.
SUMMARY OF THE INVENTION
Accordingly, the above-identified shortcomings of existing scintillators
are overcome by embodiments of the present invention, which relates to scintillators
that have coatings having combination barrier protection, light transmission, and
light reflection properties, wherein the scintillators are useful for radiation
imaging. Embodiments of this invention allow a single coating layer to act as both
a protective barrier layer and a light transmissive and reflective layer so as
to minimize the number of processing steps that are required to manufacture the
scintillators. Embodiments of this invention reduce light scattering along the
scintillator needles, thereby improving the device's performance.
Embodiments of this invention comprise scintillators. These scintillators
comprise: a scintillator material comprising a barrier coating disposed thereon,
wherein the barrier coating: (1) provides barrier protection to the scintillator
material, (2) is capable of transmitting light therethrough, and (3) is capable
of reflecting light back into the scintillator material. These coatings protect
the scintillator from ambient conditions, transmit light therethrough, and reflect
light back into the scintillator.
These coatings may comprise a material that has been modified to have light
transmissive and reflective properties in addition to protective properties, such
as Parylene (i.e., Parylene-N, Parylene-C or Parylene-D), or it may comprise a
protective material and a reflective material that have been co-deposited onto
the scintillator material. The reflective material may comprise any light reflective
material that can be co-deposited with Parylene or one of its derivatives, such
as for example, a metal, a metal compound, a metal oxide, or a metal halide.
The scintillator material may comprise: cesium iodide, cesium iodide doped with
thallium, cesium iodide doped with sodium, sodium iodide, sodium iodide dope with
thallium, lithium iodide, lithium iodide doped with europium, zinc sulphide, zinc
sulphide doped with silver, calcium fluoride, calcium fluoride doped with europium,
bismuth germinate, cesium fluoride, anthracene, stelbene, and/or a silicate glass
containing lithium activated with cerium.
These coatings comprise a single coating that overlies the scintillator material
in a substantially conformal manner, both on top of the needles and around the
sides or edges of the needles.
These coatings may be applied to the scintillators in any suitable manner,
such as for example, by chemical vapor deposition, metal organic chemical vapor
deposition, thermal evaporation, electron beam evaporation, molecular beam evaporation,
and/or sputtering.
These scintillators may be used for medical imaging, nondestructive testing
of parts, and/or detecting contraband.
Embodiments of this invention also comprise radiation imaging systems.
These systems comprise: an x-ray source; an x-ray detector comprising: a scintillator
comprising: a scintillator material comprising a barrier coating disposed thereon,
wherein the barrier coating: (1) provides barrier protection to the scintillator
material, (2) is capable of transmitting light therethrough, and (3) is capable
of reflecting light back into the scintillator material; and an amorphous silicon
array optically coupled to the scintillator; wherein the x-ray source is capable
of projecting a beam of x-rays towards the x-ray detector, the x-ray detector is
capable of detecting the x-rays, and an image can be created therefrom.
Embodiments of this invention also comprise methods for making a scintillator
having a barrier coating thereon that has both protective properties and light
reflective and light transmissive properties. These methods comprise: disposing
an amorphous silicon array on a detector substrate; disposing a scintillator material
on the amorphous silicon array; forming a barrier coating on the scintillator material;
wherein the barrier coating: (1) provides barrier protection to the scintillator
material, (2) is capable of transmitting light therethrough, and (3) is capable
of reflecting light back into the scintillator material. Disposing the scintillator
material on the amorphous silicon array may comprise growing the scintillator material
directly on the amorphous silicon array in a substantially conformal manner.
Further features, aspects and advantages of the present invention will be
more readily apparent to those skilled in the art during the course of the following
description, wherein references are made to the accompanying figures which illustrate
some preferred forms of the present invention, and wherein like characters of reference
designate like parts throughout the drawings.
DESCRIPTION OF THE DRAWINGS
The systems and methods of the present invention are described herein below with
reference to various figures, in which:
FIG. 1 is a schematic diagram showing the components of a single piece amorphous
silicon flat panel, as utilized in embodiments of this invention;
FIG. 2 is a schematic diagram showing the architecture of an x-ray system, as
utilized in embodiments of this invention; and
FIG. 3 is a schematic drawing showing cesium iodide needles coated with a protective/reflective
coating, as utilized in embodiments of this invention.
DETAILED DESCRIPTION OF THE INVENTION
For the purposes of promoting an understanding of the invention, reference will
now be made to some preferred embodiments of the present invention as illustrated
in FIGS. 1-3 and specific language used to describe the same. The terminology used
herein is for the purpose of description, not limitation. Specific structural and
functional details disclosed herein are not to be interpreted as limiting, but
merely as a basis for the claims as a representative basis for teaching one skilled
in the art to variously employ the present invention. Any modifications or variations
in the depicted structures and methods, and such further applications of the principles
of the invention as illustrated herein, as would normally occur to one skilled
in the art, are considered to be within the spirit and scope of this invention.
This invention relates to scintillators that have a coating thereon, wherein
the coating acts as both a protective barrier layer and as a light reflective layer.
This coating may comprise a protective barrier coating that has been modified to
also be a reflective coating, or it may comprise simultaneously co-depositing a
protective barrier coating with a reflective coating, thereby minimizing the number
of processing steps that are required to manufacture the scintillators. These scintillators
may be used in radiation imaging in, for example, amorphous silicon flat panel
x-ray detectors.
Referring now to FIG. 1, there is shown an exemplary amorphous silicon
flat panel x-ray detector
22, as utilized in embodiments of this invention.
Generally, column electrodes
68 and row electrodes
70 are disposed
on a single piece glass substrate
76, and an amorphous silicon array
78
is defined thereby. The amorphous silicon array
78 comprises an array of
photodiodes
41 and field effect transistors (FETs)
42. A scintillator
80 is disposed over the amorphous silicon array
78, and is optically
coupled thereto. The scintillator
80, which may comprise a dose-efficient
cesium iodide scintillator, receives and absorbs x-ray radiation during operation,
and converts the x-ray photons therein to visible light. The high fill factor amorphous
silicon array
78, wherein each photodiode
41 therein represents a
pixel, converts the detected visible light into an electrical charge. The charge
at each pixel is then read out digitally by low-noise electronics (via contact
fingers
82 and contact leads
84), and is thereafter sent to an image
processor
28.
Referring now to FIG. 2, there is shown a schematic diagram showing the
architecture of an x-ray system
20, as utilized in embodiments of this invention.
The x-ray system
20 generally comprises an x-ray source
15, an x-ray
detector
22, and an x-ray detector controller
27 that contains electronics
for operating the x-ray detector
22. During operation, x-rays
17
are directed from the x-ray source
15 towards the x-ray detector
22,
which comprises a scintillator
80 and an amorphous silicon array
78
(which comprises photodiodes
41 and field effect transistors (FETs)
42).
After passing through an object being imaged (i.e., a patient
19), the x-rays
17 fall upon scintillator
80, which converts the x-ray photons therein
to visible light. The visible light is then converted to an electrical charge by
the array of photodiodes
41 in the amorphous silicon array
78. Each
photodiode
41 is of large enough area to ensure it will intercept a sizeable
portion of the visible light produced by the scintillator
80. Each photodiode
41 also has a relatively large capacitance that allows it to store the electrical
charge that results from the photon excitation. The electrical charge is then sent
to an image processor
28, where the image signal is processed and enhanced.
The processed image may then be displayed on a cathode ray tube display
32,
or other suitable display, and/or the image can be stored in mass storage
30
for later retrieval. The image processor
28 can also produce a brightness
control signal which can be applied to an exposure control circuit
34 to
regulate the power supply
16, which can thereby regulate the x-ray source
15. The overall operation of the x-ray system may be governed by a system
controller
36, which may receive commands from operator interface
38.
Operator interface
38 may comprise a keyboard, touchpad, or other suitable
input device. An associated cathode ray tube display
32 (or other suitable
display) may allow the operator to view the reconstructed image and other data
from the image processor
28. The operator supplied commands and parameters
may be used by the system controller
36 to provide control signals and information
to the image processor
28, the x-ray detector controller
27, and/or
the exposure control circuit
34.
Embodiments of the present invention may make use of software or firmware
running on the system controller
36 to carry out the processing of data
in the methods and systems of this invention. A mouse, pointing device, or other
suitable input device may be employed to facilitate the entry of data and/or image
locations. Other embodiments of this invention may utilize a general purpose computer
or workstation having a memory and/or printing capability for storing or printing
images. Suitable memory devices are well known and include, but are not limited
to, RAM, diskettes, hard drives, optical media, etc. Embodiments using stand-alone
computers or workstations may receive data therefrom via conventional electronic
storage media and/or via a conventional communications link, and images may then
be reconstructed therefrom.
Generally, for medical applications, cesium iodide doped with about 0.05
to about 10 weight percent thallium is often used as the scintillator material.
However, any suitable phosphorescent material that produces flashes of light when
struck by particles or photons may be used as the scintillator material. For example,
the scintillators may comprise inorganic materials such as: cesium iodide, cesium
iodide doped with thallium, cesium iodide doped with sodium, sodium iodide, sodium
iodide dope with thallium, lithium iodide, lithium iodide doped with europium,
zinc sulphide, zinc sulphide doped with silver, calcium fluoride, calcium fluoride
doped with europium, bismuth germinate, and cesium fluoride. The scintillators
may also comprise organic crystals such as anthracene or stelbene, or glasses such
as silicate glasses containing lithium activated with cerium.
Any suitable method of optically coupling the scintillator material to the amorphous
silicon array can be used. Generally, the scintillator material is deposited, or
grown, directly on the amorphous silicon array via chemical vapor deposition. Chemical
vapor deposition generally involves utilizing a vacuum system and heating the scintillator
material to a high temperature to liquefy it. Thereafter, vapor comes off the liquid
and settles onto the surface of the comparatively cold amorphous silicon array
on the glass substrate. In this manner, needles of cesium iodide can be grown directly
on the amorphous silicon array on the scintillator device. The cesium iodide forms
a layer of needles about 0.1 to about 1.0 mm thick on the device.
Each needle is typically several microns in diameter (i.e., about 5-10 μm)
and several hundred microns long (i.e., about 100-1000 μm). Having such an
aspect ratio, where the needles have a relatively long length compared to a relatively
short diameter, allows most, but not all, of the visible light that is created
by the scintillator to emerge from the bottom of the scintillator and be directed
towards the corresponding pixel on the amorphous silicon array directly underlying
the location where the incident radiation was absorbed by the scintillator. In
uncoated needles, a significant amount of light can be lost due to light scattering
at the needles' interface with the ambient environment, and therefore, that portion
of the light that is lost will not reach the amorphous silicon array. Coating the
needles with a reflective coating, both on top of the needles and along the edges
or sides thereof, prevents the light from scattering out from the needles, thereby
allowing more of the light to reach the amorphous silicon array.
During operation, transport or storage, these scintillators can be exposed
to harsh, adverse environmental conditions, such as moisture, gases, extreme temperature
variations, contamination, etc., which can potentially result in damage to the
scintillators. Therefore, these scintillators generally comprise a barrier coating
thereon that acts as a protective layer to prevent the scintillator from deteriorating
when exposed to such ambient conditions. Members of the xylylene polymer family
(i.e., Parylene-C, Parylene-N and Parylene-D) are commonly used as protective layers
in scintillators.
Parylene is a conformal protective polymer coating material that has superior
corrosion resistance and dielectric protection, and that can be used to uniformly
protect various component configurations on a variety of substrates. Because of
its unique properties, Parylene conforms to virtually any shape, including flat
surfaces, sharp edges, and even crevices. Generally, Parylene is applied via specialized
vacuum deposition equipment at ambient temperatures. The Parylene, in dimer form,
is converted under heat and vacuum to a dimeric gas, which is then pyrolized to
cleave the dimer, and then the results thereof are deposited, in a substantially
conformal manner, as a clear, transparent, optical quality polymer film on the
scintillator needles. While Parylene is an effective protective barrier coating,
it has no reflective properties.
Key performance characteristics of radiation imaging devices, such as the modulation
transfer function (MTF), the conversion factor (CF), and the detective quantum
efficiency (DQE), are greatly dependent upon the light conduction and transmission
efficiency of the scintillator. Light scattering at the interface of the needles
with the atmosphere surrounding the needles can lead to a significant reduction
in the device performance. Ideally, you want the x-ray photons that strike the
scintillators to be converted to visible light therein, and be directed out towards
the corresponding pixels on the amorphous silicon array therebelow, without losing
a significant amount of light along the way. The needle-like shape of the scintillator
material itself helps, by tending to collimate the light towards the corresponding
pixels on the amorphous silicon array disposed therebelow. Additionally, a reflective
layer is commonly used to reflect the light back into the needles and prevent it
from scattering out therefrom, thereby improving the light conduction and transmission
efficiency of the scintillator. In existing scintillators, this reflective layer
is a layer that is placed only over the top of the needles; it does not cover the
sides of the needles and therefore, light can scatter out from the sides of the
needles. In this invention, the reflective layer is deposited in a substantially
conformal manner all around the needles, both on top and on the sides, thereby
allowing more light to be reflected back into the needles.
As described above, existing scintillators utilize a barrier coating or protective
layer on the scintillator material, and then utilize a separate reflective layer
over, above, or on top of, the scintillator material. This invention combines the
protective layer with the reflective layer, using a single layer or coating on
the scintillator material to act as both a protector and a reflector. Additionally,
this invention deposits this single layer or coating all around the scintillator
needles, not just on top of them, as shown in FIG. 3.
Referring now to FIG. 3, there is shown a schematic drawing showing cesium
iodide needles coated with a protective/reflective coating, as utilized in embodiments
of this invention. As shown, an amorphous silicon array
78 is disposed on
a glass substrate
76. The scintillator needles
90 are then grown
on the amorphous silicon array
78. Thereafter, a protective/reflective coating
92 is deposited to cover the needles, both the tops of the needles
90
and along at least a portion of the edges thereof. As shown herein, the protective/reflective
coating
92 generally forms an essentially solid uninterrupted layer on top
of the needles, while leaving space
94 in between the needles. This protective/reflective
coating
92 allows much more light to be reflected back into the scintillator
needles
90, thereby improving the performance of the device these scintillators
are used in.
In embodiments, Parylene may be used to form the combination protection/reflection
layer
92 on the scintillator material. In embodiments, the Parylene may
be modified as necessary so as to also have reflective properties, in addition
to its existing protective properties. In other embodiments, the Parylene may be
co-deposited with another material that has reflective properties, so that, together,
the two materials form a combination protective/reflective layer
92 surrounding
the scintillator needle material
90.
The Parylene may be modified so as to have reflective properties as well as protective
properties by modifying the deposition conditions. Samples of Parylene film were
deposited on glass substrates under the following exemplary conditions:
|
| |
Deposition |
Sublimation |
Pyrolysis |
Deposition |
Film |
| Sample |
Pressure |
Temperature |
Temperature |
Rate |
Thickness |
| # |
(Torr) |
(° C.) |
(° C.) |
(μm/hour) |
(μm) |
|
| |
| 1 |
0.4-0.5 |
120-125 |
680 |
0.3 |
4 |
| 2 |
0.7-0.8 |
127-132 |
680 |
0.9 |
10 |
|
Sample #2, which was deposited at higher pressure and deposition rates, produced
a film that was opaque white in color, while sample #1, which was deposited at
lower pressure and deposition rates, produced a film that was transparent. Therefore,
Parylene deposited under the conditions of sample #2 could be used by itself to
act as a combination protective/reflective layer on scintillator materials. There
are also numerous other conditions under which predetermined materials could be
deposited in order to produce the desired protective/reflective layer on scintillator
materials. Additionally, there are numerous other materials that could be used
instead of Parylene, such as organic polymers and/or silicon-based coatings.
Alternatively, the Parylene, or other suitable material, may be co-deposited,
via a method such as chemical vapor deposition (CVD), metal organic chemical vapor
deposition (MOCVD) or the like, with a reflective material such as, but not limited
to, metals, metal oxides, or other metallic compounds that naturally form mirror-like
surfaces. These metals, metallic oxides, and metallic compounds may comprise any
suitable metal, such as for example, one or more of the following metals: Ag, Al,
Ti, Cr, Sn, Zr, Au, Mo, etc. Co-depositing these materials yields a highly reflective
layer
92 on top of and around the scintillator needles
90, while
preserving the protective properties of the Parylene. This layer
92 reflects
the light back into the needles
90, thereby improving the light transmission
of the needles by minimizing the light that scatters out therefrom.
The scintillators described herein may be used in numerous radiation imaging
applications, such as, but not limited to, medical imaging (i.e., x-ray, computed
tomography, volume computed tomography, etc.), nondestructive imaging and/or testing
of parts, and for detecting contraband (i.e., weapons, explosives, etc.).
As described above, this invention provides a scintillator having an improved
protective barrier coating
92, wherein the protective barrier coating also
has light transmission and light reflection properties, all in a single coating.
Advantageously, this invention utilizes a combination of protective and light transmissive
and reflective materials in a single coating so as to minimize the processing steps
that are required to manufacture these scintillators, which can ideally be utilized
in radiation imaging systems. This invention may comprise a protective barrier
coating that has been modified to also comprise light transmissive and light reflective
properties. This invention may also comprise co-depositing a protective barrier
coating with a light transmissive/reflective coating. The scintillator coatings
of this invention allow improved scintillators to be produced, which can consequently
improve the performance of the radiation imaging devices they are utilized in.
Many other advantages will also be apparent to those skilled in the relevant art.
Various embodiments of this invention have been described in fulfillment
of the various needs that the invention meets. It should be recognized that these
embodiments are merely illustrative of the principles of various embodiments of
the present invention. Numerous modifications and adaptations thereof will be apparent
to those skilled in the art without departing from the spirit and scope of the
present invention. For example, while the embodiments shown and described herein
are commonly utilized in medical imaging, this invention may be utilized for other
types of radiation imaging without deviating from the spirit and scope of this
invention, and all such variations are intended to be covered herein. Furthermore,
while cesium iodide needles have been described herein, any suitable phosphorescent
material that produces flashes of light when struck by particles or photons may
be used. Additionally, while Parylene coatings have been described herein, other
suitable materials may be used in these coatings. Thus, it is intended that the
present invention cover all suitable modifications and variations as come within
the scope of the appended claims and their equivalents.
*
