U.S. patent application number 14/272405 was filed with the patent office on 2017-02-23 for crystal block array and method of manufacture.
This patent application is currently assigned to Zecotek Imaging Systems Singapore Pte Ltd. The applicant listed for this patent is Zecotek Imaging Systems Singapore Pte Ltd.. Invention is credited to Azman Mohd Ariffin, Mohammad Naim bin Mohammad Hakim, Abdelmounaime Faouzi Zerrouk.
Application Number | 20170052262 14/272405 |
Document ID | / |
Family ID | 52809916 |
Filed Date | 2017-02-23 |
United States Patent
Application |
20170052262 |
Kind Code |
A9 |
Zerrouk; Abdelmounaime Faouzi ;
et al. |
February 23, 2017 |
CRYSTAL BLOCK ARRAY AND METHOD OF MANUFACTURE
Abstract
A novel method of making a crystal block array (configured for
coupling with photodetectors as part of an integrated detector
module useful in advanced PET scanner systems) is disclosed herein.
The novel method comprises a series of cutting, polishing, and
assembling steps that utilize reflective sheet material. The
crystal block arrays disclosed herein may be of various dimensions
and geometries and are amenable to mass production.
Inventors: |
Zerrouk; Abdelmounaime Faouzi;
(Lausanne, CH) ; Ariffin; Azman Mohd; (Singapore,
SG) ; Hakim; Mohammad Naim bin Mohammad; (Singapore,
SG) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zecotek Imaging Systems Singapore Pte Ltd. |
Singapore |
|
SG |
|
|
Assignee: |
Zecotek Imaging Systems Singapore
Pte Ltd
Singapore
SG
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20150104602 A1 |
April 16, 2015 |
|
|
Family ID: |
52809916 |
Appl. No.: |
14/272405 |
Filed: |
May 7, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14051328 |
Oct 10, 2013 |
9310493 |
|
|
14272405 |
|
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61712181 |
Oct 10, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B32B 37/02 20130101;
B32B 38/0004 20130101; Y10T 156/1062 20150115; G01T 1/202 20130101;
G01T 1/2002 20130101; Y10T 156/1075 20150115; Y10T 156/1059
20150115; B32B 37/12 20130101; B32B 37/14 20130101; Y10T 428/16
20150115; B32B 2038/045 20130101 |
International
Class: |
G01T 1/202 20060101
G01T001/202 |
Claims
1. A method of making a crystal block array, comprising at least
the steps of: providing a selected crystal having a generally
cylindrical form; cutting the selected crystal crosswise a
plurality of times to yield a plurality of crystal pucks, with each
crystal puck having a selected height; cutting at least one of the
plurality of crystal pucks along a heightwise direction a plurality
of times to yield a plurality of first crystal slabs; polishing the
flat surfaces of at least two of the plurality of first crystal
slabs to an optical finish; applying a first reflective sheet
material on at least one face of the at least two of the plurality
of first crystal slabs, thereby defining a first layered optical
block assembly; cutting the first layered optical block assembly
along a lengthwise direction a plurality of times to yield a
plurality of second crystal slabs of sandwich construction;
polishing the flat surfaces of at least two of the plurality of
second crystal slabs of sandwich construction to an optical finish;
and applying a second reflective sheet material on at least one
face of the at least two of the plurality of second crystal slabs
of sandwich construction, thereby defining a crystal block
array.
2. The method of claim 1 wherein the selected crystal is a boule of
a scintillation substance.
3. The method of claim 1, wherein applying the first reflective
sheet material between the at least two of the plurality of first
crystal slabs comprises applying a first adhesive between
respective first reflective sheet material and first crystal
slabs.
4. The method of claim 3, further comprising curing the first
adhesive.
5. The method of claim 4, wherein curing the first adhesive
comprises exposure to ultraviolet light.
6. The method of claim 3, wherein applying the second reflective
sheet material between the at least two of the plurality of second
crystal slabs of sandwich construction comprises applying a second
adhesive between respective second reflective sheet material and
second crystal slabs.
7. The method of claim 6, wherein the first and second adhesive are
the same adhesive.
8. The method of claim 1 wherein the first and second reflective
sheet materials are the same material.
9. The method of claim 1 wherein the first and second reflective
sheet material are composed of 3M Radiant Mirror Film VM 2000.
10. A crystal block array made in accordance with the method of
claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 14/051,328 filed Oct. 10, 2013, which claims
the benefit of priority to U.S. Provisional Application No.
61/712,181 filed on Oct. 10, 2012. These applications are
incorporated herein by reference in their entireties for all
purposes.
TECHNICAL FIELD
[0002] The present invention relates generally to scintillation
crystals and related crystal block assemblies used in Positron
Emission Tomography (PET) scanners and, more particularly, to
scintillation crystal block arrays (configured for coupling with
photodetectors as part of an integrated detector module useful in
advanced PET scanner systems), as well as to methods of making and
using high performance scintillation crystal block arrays.
BACKGROUND
[0003] In nuclear medicine, scintillation crystals have become
important components of medical imaging devices. The performance of
these medical imaging devices, including Positron Emission
Tomography (PET) scanners, largely depends on the quality and
uniformity of scintillation crystals and on related crystal block
array assemblies. The cost of making such medical imaging devices
is generally expensive. Thus, there is a need to reduce
manufacturing costs by simplifying the procedures for making
scintillation crystal block arrays.
[0004] In a general sense, positron emission tomography is a
medical imaging technique in which a patient ingests a
radioactively tagged compound that mimics a naturally occurring
compound. For reasons relating to the body's metabolism, the
compound tends to accumulate in tumors. The radioactively tagged
compounds tend to emit gamma rays. The gamma rays can be detected
outside of the patient's body. In particular, when the
scintillation crystals are struck by a gamma ray, they are likely
to emit a photon ("scintillation"). The photon is in turn
recognized by a photodetector, which generates an electronic
signal. Various hardware and software components use the electronic
signal to reconstruct the likely position (within a known
tolerance) of the original gamma ray emission.
[0005] In accordance with known methods of making a crystal block
array, a scintillation crystal boule may be cut and polished to
generate a plurality of individual scintillation crystal pixels
that are then each surrounded by Teflon tape and grouped into a
crystal block array. In accordance with other known methods, a
reflective sheet material matrix may be defined, and individual
scintillation crystal pixels can be disposed within slots defined
by the sheet material matrix. However, these methods produce
crystal block arrays that include gaps and inconsistently packed
pixels.
[0006] Better crystals and more uniform crystal block arrays
provide better information about the gamma rays and thus provide a
better image, and help lead to a better diagnosis, and potentially
better medical treatment. Accordingly, and although some progress
has made with respect to the development of crystal block arrays,
there is still a need in the art for new crystal block arrays and
related methods of manufacture to overcome the deficiencies and
obstacles discussed above.
SUMMARY
[0007] The present invention in an embodiment is directed to a
novel method of making a crystal block array. The inventive method
comprises at least the steps of: providing a selected crystal
having a generally cylindrical form; cutting the selected crystal
crosswise a plurality of times to yield a plurality of crystal
pucks, with each crystal puck having a selected height; cutting at
least one of the plurality of crystal pucks along a heightwise
direction a plurality of times to yield a plurality of first
crystal slabs; polishing the flat surfaces of at least two of the
plurality of first crystal slabs to an optical finish; applying a
first reflective sheet material on at least one face of the at
least two of the plurality of first crystal slabs, thereby defining
a first layered optical block assembly; cutting the first layered
optical block assembly along a lengthwise direction a plurality of
times to yield a plurality of second crystal slabs of sandwich
construction; polishing the flat surfaces of at least two of the
plurality of second crystal slabs of sandwich construction to an
optical finish; and applying a second reflective sheet material on
at least one face of the at least two of the plurality of second
crystal slabs of sandwich construction, thereby defining a crystal
block array.
[0008] These and other aspects of the present invention will become
more evident upon reference to the following detailed description
and accompanying drawings. It is to be understood, however, that
various changes, alterations, and substitutions may be made to the
specific embodiments disclosed herein without departing from their
essential spirit and scope.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The drawings are intended to be illustrative and symbolic
representations of certain exemplary embodiments of the present
invention (namely, the manufacture of an exemplary 4.times.4
pixelated crystal block array useful for operations within a PET
scanner) and as such are not necessarily drawn to scale. In
addition, the relative dimensions and distances depicted in the
drawings are exemplary and may be varied in numerous ways. Finally,
like reference numerals have been used to designate like features
throughout the views of the drawings.
[0010] FIG. 1A is a perspective view of a selected crystal
boule.
[0011] FIG. 1B is a perspective exploded view of the crystal boule
shown in FIG. 1A, but wherein the crystal boule has had its top and
bottom portions cut-off and removed.
[0012] FIG. 1C is a perspective view of one of the crystal pucks
shown in FIG. 1B, but wherein the crystal puck has been cut
lengthwise a plurality of times to yield a plurality of crystal
slabs in accordance with an embodiment of the present
invention.
[0013] FIG. 2 is a top plan view of the sliced crystal puck shown
in FIG. 1C.
[0014] FIG. 3 is a top plan view of the sliced crystal puck shown
in FIGS. 1C and 2, but wherein the two outermost crescent-shaped
slabs have been removed and a plurality of first wires (spacers)
have been placed between the slabs and at their outer edges in
accordance with an embodiment of the present invention.
[0015] FIG. 4 is a top plan view of the sliced and spaced apart
slabs shown in FIG. 3, but wherein a bonding agent has been placed
in between each of the slabs, and between first and second glass
end plates positioned adjacent to the outermost slabs to form a
"sandwich" block in accordance with an embodiment of the present
invention.
[0016] FIG. 5 is a top plan view of the bonded together slabs and
glass end plates shown in FIG. 4, but wherein UV light is being
applied to facilitate curing of the bonding agent in accordance
with an embodiment of the present invention.
[0017] FIG. 6 is a top plan view of the bonded together slabs and
glass end plates shown in FIG. 5, but after exposure to UV light
and wherein the slabs have been cut lengthwise a plurality of times
and in a transverse direction to the first plurality of lengthwise
cuts to yield a plurality of crystal pixels (second slabs of
sandwich construction) and a pair of outer pixel end pieces in
accordance with an embodiment of the present invention.
[0018] FIG. 7 is a top plan view of the plurality of crystal pixels
(second slabs of sandwich construction) shown in FIG. 6, but
wherein a plurality of second wires (spacers) have been placed
between the second segmented slabs of sandwich construction and at
their outer edges in accordance with an embodiment of the present
invention.
[0019] FIG. 8 is a top plan view of the unfinished crystal block
array of FIG. 7, but wherein opposing third and fourth protective
glass plates have been added and further bonding agent has been
added.
[0020] FIG. 9 is a top plan view of a crystal block array in
accordance with an embodiment of the present invention.
[0021] FIG. 10 is a perspective view of the crystal block array
shown in FIG. 9.
[0022] FIG. 11 is a top plan view of the sliced crystal puck shown
in FIGS. 1C and 2, but wherein the two outermost crescent-shaped
slabs have been removed.
[0023] FIG. 12 is a top plan view of reflective sheet material
stacked between crystal slabs of FIG. 11.
[0024] FIG. 13 is a top plan view of the stack of FIG. 12 that has
been cut lengthwise a plurality of times and in a transverse
direction to the first plurality of lengthwise cuts to yield a
plurality of crystal pixels (second slabs of sandwich
construction).
[0025] FIG. 14 is a top plan view of the second slabs of sandwich
construction of FIG. 13 with crescent-shaped slabs removed.
[0026] FIG. 15 is a top plan view of a crystal block array in
accordance with an embodiment of the present invention where
reflective sheet material is stacked between the second slabs of
sandwich construction of FIG. 14 to define the crystal block
array.
[0027] FIG. 16 is a perspective view of the crystal block array
shown in FIG. 15.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Referring now to the drawings where like numerals have been
used to designate like features throughout the views, and more
specifically to FIGS. 1A through 10, the present invention in an
embodiment is directed to a novel method of making a scintillation
crystal block array 10 (as shown in Figures and 9 and 10) adapted
for coupling with a planar photodetector array (not shown) as part
of an integrated detector module useful in an advanced PET scanner
system (not shown). In the inventive method and as an initial step,
a crystal boule 7 (FIG. 1A) of an appropriately grown and sized
scintillation crystal (such as, for example, a cerium-activated
lutetium-based oxyorthosilicate scintillation crystal boule (Ce:LSO
and/or Ce:LYSO) grown by the Czochralski method) is first
selectively sliced (cut) into a plurality of "pucks" (FIG. 1B). In
other words, a selected scintillation crystal boule 7 of a
generally cylindrical form is cut a plurality of times along its
width (perpendicular to its longitudinal axis) to yield a plurality
of pucks 12. The plurality of pucks 12 that are cut (sliced) from
the selected cylindrical crystal boule 7 may or may not be of the
same height. The cutting or slicing of the crystal boule 7 may be
carried out with the aid of an appropriate cutting tool such as,
for example, a diamond hardened saw. In addition, the height of
each puck 12 is typically selected to be equal to the length of the
individual scintillation crystal pixels 11 (utilized in a
particular PET scanner) plus a minor allowance for
grinding/polishing. Scintillation crystal pixels utilized in
advanced PET scanners generally have dimensions of about
4.times.4.times.20 millimeters (mm) or about 4.times.4.times.22
millimeters (mm) or about 4.7.times.6.3.times.30 millimeters (mm),
but are not limited to those exemplary dimensions. Accordingly, the
present invention is not limited to any particular crystal or pixel
dimension or range of dimensions and is applicable to the
manufacture of scintillation crystal block arrays of various sizes
and dimensions. For example, the inventive method is useful for
making all types arrays having any number of rows and columns
(2.times.2, 3.times.3, 4.times.4, 4.times.6, et cetera).
[0029] As best shown in FIGS. 1C and 2, a puck 12 having a selected
height (h) is further sliced (cut) along its height (parallel to
its longitudinal axis) to yield a plurality of inner "slabs" 14
positioned between a pair of opposing end slab pieces 16. The pair
of opposing end slab pieces 16 are removed and set aside for other
applications. The remaining inner slabs 14 are each further lapped
and polished on all of their flat surfaces (preferably to at least
an optical finish of it/8 or better) and readied for further
assembly.
[0030] As best shown in FIG. 3, the inner slabs 14 are reassembled
back into the shape of the puck 12 (less the removed pair of
opposing end slab pieces 16), but spaced apart from each other by
means of first height-wise wires 18 selectively positioned between
the slabs 14 and along their outer edges as shown. The first wires
18 are of a selected diameter that preferably ranges from about 0.1
mm to 1.0 mm, or preferably from about 0.5 mm to 0.6 mm. The
diameter of the wires 18 corresponds to the distance between
adjacent pixels 11 of the final crystal block array 10. The wires
18 may be metallic or polymeric, and in some embodiments are
composed of nylon.
[0031] Next and as shown in FIG. 4, a curable liquid or semi-liquid
bonding agent 19 (such as, for example, an optical cement made of a
barium sulphate composition) is applied between each of the spaced
apart slabs 14 and between first and second glass end plates 20, 22
that have been positioned adjacent to the two outermost slabs 14,
all of which together form a "sandwich" block. As shown in FIG. 5,
the bonding agent (cement) 19 positioned within the sandwich block
is subsequently cured (hardened) by exposure to UV light for a
selected period of time. In this regard, curing times are generally
a function of at least the type of bonding agent used, its applied
thickness, and on the intensity of the light source. Accordingly,
curing times may be as short as five minutes or as long as several
hours.
[0032] Next and as shown in FIG. 6, the cured sandwich block 24 is
selectively sliced (cut) a plurality of times perpendicular to the
first and second protective glass end plates 20, 22 (as well as to
the inner bonded together first slabs 14) to yield a plurality of
second slabs of sandwich construction 24, and a pair of opposing
end second slab pieces 26. The pair of opposing end second slab
pieces 26 are removed and set aside for other applications. The
remaining inner second slabs of sandwich construction 24 are each
further lapped and polished on all of their flat surfaces
(preferably to at least an optical finish of A/8 or better) and
readied for further assembly.
[0033] As shown in FIG. 7, the inner second slabs of sandwich
construction 24 are reassembled back into the shape of an
unfinished crystal block array (less the removed pair of opposing
end second slab pieces 26), but spaced apart from each other by
means of second height-wise wires 28 selectively positioned between
the second slabs of sandwich construction 24 and along their outer
edges (and adjacent to the first and second glass end plates 20,
22, which have now been cut as described above) as shown. The
plurality of second wires 28 may or may not be the same diameter as
the plurality of first wires 18.
[0034] Next and as shown in FIG. 8, a pair of opposing third and
fourth protective glass end plates 30, 32 are similarly positioned
adjacent to and spaced apart from the unfinished crystal block
array, and thereafter additional bonding agent 19 is poured into
the space therebetween and subsequently cured as before. The first,
second, third, and fourth protective glass end plates 20, 22, 30,
32 are all removed by use a diamond plate tool, for example, and
all of the surfaces are cleaned to thereby yield (as shown in FIGS.
9 and 10) a crystal block array 10 having highly uniform and
controlled spacing between individual pixels 11.
[0035] In some embodiments, alternative materials may be used to
surround individual pixels 11 instead of bonding agent 19. For
example, pixels 11 may be surrounded by a reflective sheet material
such as a film or tape. In one preferred embodiment, 3M Radiant
Mirror Film VM 2000 (3M Company, Minnesota) is used. Manufacturing
steps including the use of spacers or wires 18 may be absent in
various embodiments where a reflective sheet material is used.
[0036] Accordingly, referring to FIG. 11 crescent-shaped slabs 16
can be removed from the sliced crystal puck 12 shown in FIGS. 1C
and 2. As shown in FIG. 12, the remaining slabs 14 may be stacked
with first reflective sheet material 42 between each of the slabs
14. and with first reflective sheet material 40 at the ends of the
stack. In various embodiments, an adhesive may be applied between
respective faces of reflective sheet material 40, 42, and
respective faces of the slabs 14 so that the slabs 14 and
reflective sheet material 40, 42 are rigidly coupled. Such a stack
may be cut into second slabs of sandwich construction 44, 46 as
depicted in FIG. 13. Crescent-shaped second slabs of sandwich
construction 46 may be removed as shown in FIG. 14 and cut faces of
the second slabs of sandwich construction 44 may be polished to an
optical finish.
[0037] The second slabs of sandwich construction 44 may be further
stacked with a second reflective sheet material 46 between each of
the second slabs of sandwich construction 44 and with second
reflective sheet material 48 at the ends of the stack to yield a
crystal block array 10 as depicted in FIGS. 15 and 16. The first
and second reflective sheet materials may be the same or different
in some embodiments.
[0038] In various embodiments, an adhesive may be applied between
respective faces of reflective sheet material 46, 48, and
respective faces of the second slabs of sandwich construction 44 so
that the second slabs of sandwich construction 44 and reflective
sheet material 46, 48 are rigidly coupled. An optical adhesive may
be selected having desirable qualities. In some embodiments, an
adhesive may require curing or other treatment, which may include
heating, drying, or exposure to light, including ultraviolet light.
Accordingly, in some embodiments, a production method may include
one or more step of curing or treating an applied adhesive.
[0039] While the present invention has been described in the
context of the embodiments illustrated and described herein, the
invention may be embodied in other specific ways or in other
specific forms without departing from its spirit or essential
characteristics. Therefore, the described embodiments are to be
considered in all respects as illustrative and not restrictive. The
scope of the invention is, therefore, indicated by the appended
claims rather than by the foregoing description, and all changes
that come within the meaning and range of equivalency of the claims
are to be embraced within their scope.
* * * * *