U.S. patent application number 12/016101 was filed with the patent office on 2008-05-15 for self-alignment of radiographic imaging system.
This patent application is currently assigned to Varian Medical Systems Technologies, Inc.. Invention is credited to Daniel M. Hardesty.
Application Number | 20080112541 12/016101 |
Document ID | / |
Family ID | 37524114 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080112541 |
Kind Code |
A1 |
Hardesty; Daniel M. |
May 15, 2008 |
SELF-ALIGNMENT OF RADIOGRAPHIC IMAGING SYSTEM
Abstract
An imaging system 10 is provided comprising an x-ray source 12,
a detector 14, and an alignment device 38 adapted to align the
detector 14 with the x-ray source 12 using an x-ray beam
transmitted from the x-ray source 12. A method of positioning and
aligning an imaging system is also provided.
Inventors: |
Hardesty; Daniel M.;
(Lincoln, CA) |
Correspondence
Address: |
FOLEY & LARDNER LLP
975 PAGE MILL ROAD
PALO ALTO
CA
94304
US
|
Assignee: |
Varian Medical Systems
Technologies, Inc.
|
Family ID: |
37524114 |
Appl. No.: |
12/016101 |
Filed: |
January 17, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11153001 |
Jun 14, 2005 |
7344304 |
|
|
12016101 |
Jan 17, 2008 |
|
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Current U.S.
Class: |
378/205 |
Current CPC
Class: |
A61B 6/08 20130101; G01N
23/04 20130101; A61B 6/4233 20130101; A61B 6/548 20130101; A61B
6/587 20130101 |
Class at
Publication: |
378/205 |
International
Class: |
A61B 6/08 20060101
A61B006/08 |
Claims
1. An imaging system comprising an x-ray source, a detector, and an
alignment device adapted to align the detector with the x-ray
source using an x-ray beam transmitted from the x-ray source,
wherein the x-ray source and the detector are not mechanically
connected during at least a portion of an alignment method.
2. The imaging system of claim 1 wherein said x-ray source and/or
detector are movable relative to each other.
3. The imaging system of claim 1 wherein said alignment device
comprises a reticle having an opening therein, said reticle is
adapted to be positioned between the x-ray source and the detector
to allow a portion of an x-ray beam passing therethrough.
4. The imaging system of claim 1 wherein said imaging system is a
fluoroscopic imaging system.
5. The imaging system of claim 1, further comprising a positioning
device coupled to said x-ray source, said positioning device is
adapted to center said detector in an x-ray field.
6. The imaging system of claim 5 wherein said positioning device
comprises a reticle having an opening adapted to allowing a portion
of an x-ray beam passing through.
7. The imaging system of claim 1 wherein the detector and the x-ray
source are electronically connected to each other.
8. The imaging system of claim 1 wherein the detector and the x-ray
source are separately moveable.
9. The imaging system of claim 1 wherein the detector and the x-ray
source are synchronically moveable.
10. An imaging system comprising an x-ray source and a detector
movable relative to each other, and an alignment device adapted to
align the detector with the x-ray source using an x-ray beam
transmitted from the x-ray source, wherein said imaging system is
portable.
11. The portable imaging system of claim 10 wherein the alignment
device comprises a reticle having an opening therein, said reticle
is adapted to be positioned between the x-ray source and the
detector to allow a portion of an x-ray beam passing
therethrough.
12. A method of aligning an imaging system including an x-ray
source and a detector moveable relative to each other, the x-ray
source and the detector being not mechanically connected during at
least a portion of said method, said method comprising the steps
of: providing an alignment device between the x-ray source and the
detector; transmitting an x-ray beam from the x-ray source to the
alignment device which passes a portion of the x-ray beam;
detecting the portion of the x-ray beam by the detector to generate
an image; and determining the image formed on a display.
13. The method of claim 12 wherein said alignment device comprises
a reticle having an opening, and said determining step comprises
measuring a distance between an edge of the image and an edge of
the display.
14. The method of claim 12, further comprising the step of
adjusting the detector and/or the x-ray source based on the
determining step.
15. An imaging system comprising an x-ray source, a detector, and
an alignment device to align the detector with the x-ray source
using an x-ray beam transmitted from the x-ray source, wherein the
x-ray source and/or the detector are adapted to be independently
freely moveable relative to an object to be examined to position
the detector relative to the x-ray source during at least a portion
of a positioning and/or an alignment process.
16. The imaging system of claim 15 wherein the detector and x-ray
source are adapted to be moveable together after the detector and
x-ray source are aligned.
17. A method of aligning an imaging system including an x-ray
source and a detector moveable relative to each other, comprising
the steps of: positioning a detector relative to an x-ray field by
independently freely moving said detector and/or x-ray source
relative to an object to be examined; and aligning the detector
with the x-ray source using an alignment device.
18. The method of claim 17 wherein said alignment device is adapted
to allow a portion of an x-ray beam passing through to generate an
image on a display.
19. The method of claim 17 wherein in the positioning step a
positioning device is used to allow a portion of an x-ray beam
passing through to generate an image on a display.
20. The method of claim 17 further comprising the step of moving
the detector and the x-ray source together after the detector and
the x-ray source are aligned.
21. The method of claim 17 wherein said imaging system is a
fluoroscopic imaging system.
Description
CROSS REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application is a continuation application of U.S.
application Ser. No. 11/153,001, filed Jun. 14, 2005, the
disclosure of which is incorporated herein by reference in its
entirety.
FIELD OF THE INVENTION
[0002] This invention relates generally to radiographic imaging
systems and methods, and in particular, to systems and methods for
automatically positioning and aligning radiographic imaging
systems.
BACKGROUND
[0003] Radiographic imaging such as X-ray imaging has been used for
a wide variety of applications in various fields. A typical x-ray
imaging system includes an x-ray source generating x-ray beams to
irradiate a region of interest (ROI), and an x-ray detector
detecting the x-ray beams passing through the ROI. To achieve an
x-ray image with sufficient information, precise positioning and
alignment of the imaging system, especially between the x-ray
source and detector, is required. In prior art imaging systems, the
x-ray source and detector are physically attached to each other in
a rigid and bulky structure such as an enclosed housing. In such
imaging systems, the x-ray source and detector are aligned in fixed
positions and typically not moveable relative to each other or able
to repositioned and/or realigned.
[0004] U.S. Pat. No. 6,282,264 describes a method of positioning a
digital flat panel in an x-ray imaging system. While the x-ray
source and detector are moveable relative to each other, the
detector is mechanically connected with an x-ray tube and the
alignment of the imager with the x-ray tube is achieved by moving
the imager through pre-defined ranges of motion in a known
coordinate system physically installed in an examination room.
[0005] There are instances that it is necessary to examine or
inspect objects such as a suspicious container in a non-destructive
way to not trigger, for example, an explosive that might be
concealed inside the container. There are also instances that it is
impractical to move objects such as a pipeline in use to an
examination room for inspection. It is desirable to have a portable
x-ray imaging system in these instances so that an x-ray source and
a detector can be conveniently positioned, readily moveable and
adjusted. Accordingly, there is a need to automatically align an
x-ray source and a detector without mechanical linkage for optimum
performance of an imaging system.
SUMMARY OF THE INVENTION
[0006] An imaging system is provided comprising an x-ray source, a
detector, and an alignment device adapted to align the detector
with the x-ray source using an x-ray beam transmitted from the
x-ray source. A method of positioning and aligning an imaging
system is also provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and various other features and advantages of the
present invention will become better understood upon reading of the
following detailed description in conjunction with the accompanying
drawings and the appended claims provided below, where:
[0008] FIG. 1 is a schematic illustrating a properly positioned and
aligned detector, an improperly positioned detector, and a
misaligned detector in an x-ray imaging system;
[0009] FIG. 2 is a schematic illustrating an x-ray imaging system
in accordance with an embodiment of the present invention;
[0010] FIG. 3 is a schematic illustrating an x-ray imaging system
including a reticle in accordance with an embodiment of the present
invention;
[0011] FIG. 4 is a schematic illustrating a reticle used in
aligning a detector with an x-ray source in accordance with an
embodiment of the present invention;
[0012] FIG. 5 is a schematic illustrating an x-ray imaging system
including a radio frequency modulator in accordance with an
embodiment of the present invention;
[0013] FIG. 6 is a schematic illustrating a reticle used in
positioning a detector in accordance with an embodiment of the
present invention;
[0014] FIG. 7 is a block diagram illustrating a method of
positioning a detector with an x-ray source in accordance with an
embodiment of the present invention;
[0015] FIG. 8 is a block diagram illustrating a method of aligning
a detector with an x-ray source in accordance with an embodiment of
the present invention; and
[0016] FIG. 9 is a block diagram illustrating a method of aligning
a detector with an x-ray source in accordance with another
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Various embodiments of the present invention are described
hereinafter with reference to the figures. It should be noted that
the figures are not drawn to scale and elements of similar
structures or functions are represented by like reference numerals
throughout the figures. It should also be noted that the figures
are only intended to facilitate the description of specific
embodiments of the invention. They are not intended as an
exhaustive description of the invention or as a limitation on the
scope of the invention. In addition, an aspect described in
conjunction with a particular embodiment of the present invention
is not necessarily limited to that embodiment and can be practiced
in any other embodiments of the present invention. For instance, in
the following description, the present invention is described with
embodiments of an x-ray imaging system. It will be appreciated that
the claimed invention can be used not only for x-ray imaging
systems, but also for any other type of radiographic imaging
systems such as infrared ray, visible ray, and ultraviolet ray
imaging systems. Further, in the following description, the present
invention is described with embodiments of two-dimensional images
shown on a display. It will be appreciated that the claimed
invention can be used in an imaging system where three- or
four-dimensional images are formed, for instance, using a cone beam
technology.
[0018] The present invention provides a method of positioning
and/or aligning an imaging system. As used herein, the term
"positioning" refers to an act of adjusting the location of an
x-ray source and/or a detector in an x-ray field. The term
"aligning" refers to an act of adjusting the orientation of a
detector and/or an x-ray source so that the x-ray source is normal
to the surface of the detector. FIG. 1 schematically illustrates an
imaging system 1 including an x-ray source 2 and a detector 3 with
a position error 3A, a misalignment 3B, and a proper position and
alignment 3C. An image 6 of an object 4 is shown on a display
5.
[0019] An imaging system 10 in accordance with an embodiment of the
present invention is illustrated in FIG. 2. The imaging system 10
is a portable, self-contained x-ray imaging system that can
digitally process, display, store and/or transmit electronic x-ray
images of a region of interest in an object in real time. The x-ray
imaging system 10 includes an x-ray source 12, a detector 14, and a
control station 16. Between the spaced apart x-ray source 12 and
detector 14 is an object 18 to be examined or inspected. By way of
example, the object 18 can be any object such as a patient,
container, pipe, and any other item or region of interest to be
investigated.
[0020] The x-ray source 12 generates and transmits an x-ray beam 13
to a region of interest 17 in the object 18. The x-ray detector 14
receives and detects the x-ray beam passing through the region of
interest 17. The detector 14 can be a two-dimensional flat panel
imager. The x-ray beam 13 is converted to electrical signals
representing the intensity of the x-ray beams passing through the
region of interest 17. The electrical signals are transmitted to
the control station 16 via a signal cable 20, or alternatively, via
wireless means (not shown). The electrical signals are processed in
a process unit 22 in the control station 16 to form an image, which
is displayed on a display 24. The imaging system 10 of the present
invention can be a fluoroscopic imaging system, in which the x-ray
source 12 scans any regions of interest 17 in the object 18 and the
detector 14 detects the x-ray beams 13 and converts them to
electrical signals to form and display images in real time.
[0021] The x-ray source 12 and detector 14 are supported in
supporting structures such as articulated arms 26 and 28,
respectively. Both the x-ray source 12 and the detector 14 can be
translated, rotated, and/or tilted in any directions with manual
and/or robotic motion control. In an embodiment of the present
invention, the x-ray source 12 and detector 14 are independently
controlled and not physically or mechanically connected to each
other. In an alternative embodiment, the x-ray source 12 and the
detector 14 are electronically connected and moved together after
they are properly positioned and aligned.
[0022] The control station 16 can include a control unit 30 for
actuating and/or controlling the detector 14 and/or x-ray source
12, a process unit 22 for processing the electrical signals
transmitted from the detector 14, and a display unit 24 for
displaying images formed. A power supply 32 can be included in the
control station 16 for supplying power to the imaging system 10.
Peripheral component interconnect (PCI) card bus 34 is included in
the control station 16 for interfacing with the detector 14 and
power supply 32. The control station 16 can be portable and
self-contained in a suitcase.
[0023] FIG. 3 schematically illustrates an imaging system 10 in
accordance with an embodiment of the present invention that can be
used for inspecting, for example, the integrity of a plastic or
metal pipe 36. The detector 14 is placed inside an enclosed area
such as a pipe as illustrated. In this embodiment, the detector 14
is not physically and/or mechanically connected with the x-ray
source 12. An alignment device 38 is used to align the detector 14
with the x-ray source 12.
[0024] FIG. 4 schematically illustrates an alignment device 38 in
accordance with an embodiment of the present invention. The
alignment device 38 can be in the form of a reticle, which can be
made of a heavy metal such as tungsten, or lead. An opening 40 is
provided in the reticle 38. By way of example, the opening 38 shown
in FIG. 4 is in the shape of a square and a square image 42 is
formed on the display 24. Other shapes suitable for forming a
unique and readily recognizable image such as a circle or star can
also be used. For instance, the opening 40 in the reticle 38 can be
an elongated slot, which allows the x-ray beam passing through to
form an elongated band image on the display. Alternatively, the
reticle can be a block having a plurality of small holes or
openings forming a specific configuration, such as a square or
circle.
[0025] The alignment reticle 38 can be attached to the x-ray source
12 at a distance from the focal point 44 of the x-ray source 12. In
use, the x-ray source 12 transmits an x-ray beam 13 to the
alignment reticle 38. A portion 48 of the x-ray beam 13 passes
through the opening(s) 40 and irradiates the object 18 to be
examined. The rest of the x-ray beam is blocked by the alignment
reticle 38. The portion 48 of the x-ray beam passing through the
opening(s) 40 and the object 18 is projected onto the detector 14,
which converts the x-ray beam into electrical signals to form an
image 42 on a display 24.
[0026] FIG. 4 illustrates an example of a misaligned detector 14a,
which is tilted, with the upper portion of the detector closer to
the x-ray source 12 and the lower portion farther from the x-ray
source 12. The portion 48 of x-ray beam 48 passing through the
alignment reticle 38 and object 18 is projected onto the misaligned
detector 14a asymmetrically with respect to a pre-defined position,
e.g., the center of the detector 14a due to magnification of the
x-ray beam. For example, as shown in FIG. 4, the x-ray beam is
projected closer to the upper edge and farther from lower edge of
the detector 14a. The image 42a generated by the misaligned
detector 14a is reflected on the display 24a, which is closer to an
upper edge and farther from the lower edge of the display 24a.
[0027] The misaligned detector 14a can be then adjusted either
manually or by remote control. For example, the detector 14a can be
translated, rotated, and/or tilted during the adjustment.
Alternatively, the x-ray source 12 can be independently translated,
rotated, and/or tilted during the adjustment. The fluoroscopic
imaging system makes possible of real-time display of images during
the adjustment of the x-ray source 12 and/or the detector 14 in
various orientations. By adjusting the orientation of the detector
and/or the x-ray source, and determining the images shown on the
display in real time, the detector can be properly aligned. Once
the detector 14 is precisely aligned with the x-ray source 12, the
projection of the x-ray beam 48 is on a pre-defined position, e.g.,
the center of the detector 14, which is reflected by an image 42 on
a pre-defined position, e.g., the center of the display 24, as
determined by for example, an equal distance of the image 42 to
each side of the display 24.
[0028] FIG. 5 illustrates an imaging system including a radio
frequency (RF) modulator 50, which can be used to align the
detector 14a with the x-ray source 12. As shown in FIG. 5, a
modulator 50 is coupled to the x-ray source 12. The modulator 50
transmits a RF base wave having a frequency such as 5-10 gHz which
modulates the voltage of an x-ray beam 13 generated by the x-ray
source 12. The modulated x-ray beam passes through the object 18
and is received in the detector 14a. Two or more RF receivers 52
are coupled to the detector 14a to detect the phase angles of the
RF base wave. FIG. 5 shows an example in which four RF receivers 52
are coupled to each of the four corners of the detector 14a.
Alternatively, two or more RF receivers 52 can be coupled to each
side of the detector 14a. In some embodiments, the RF receivers 52
can be integrated into the sensors and electronics of the detector
14a. The RF receivers 52 detect the phase angles of the base wave
arrived at the RF receivers 52. If the detector is misaligned, as
detector 14a illustrated in FIG. 5, the phase angles of the RF base
wave arrived at different RF receivers 52 differ. Thus, by
determining the phase angles of the RF base wave arrived at
different spots on the detector, the alignment of the detector can
be determined. For example, in the embodiment illustrated in FIG.
5, the phase angle of the base wave arrived at point A in the
detector 14a is detected as .theta.1, indicating a distance between
the x-ray source 12 and point A of 17 cm. The phase angle of the
base wave arrived at point B is detected as .theta.2, indicating a
distance between the x-ray source 12 and point B of 16.2 cm. Thus,
the difference in phase angles between point A and B indicates the
differences in distances between the x-ray source 12 and point A
and between the x-ray source 12 and point B respectively, which in
turns indicates a misalignment between the detector 14 and the
x-ray source 12.
[0029] The misaligned detector 14a is then adjusted as described
above, by translating, rotating, and/or tilting the detector.
Alternatively, the x-ray source 12 can be independently translated,
rotated, and/or tilted. Once the detector 14 is precisely aligned
with the x-ray source 12, the phases angles of the RF base wave
arrived at different spots in the detector 14 are equal, indicating
equal distance between the x-ray source 12 and the different spots
in the detector 14, which in turn indicates proper alignment of the
detector 14 and the x-ray source 12.
[0030] FIG. 6 illustrates an embodiment of the present invention
for positioning a detector in an x-ray field. As shown in FIG. 6,
detector 14b is not properly positioned in an x-ray field. As a
result of the improper positioning, detector 14b does not receive
all of the x-ray beams passing through the region of interest in
the object 18 and the image formed does not include sufficient
information about the region of interest.
[0031] To properly position a detector 14 within an x-ray field, a
positioning reticle 56 can be used. A small opening 52 is provided
in the positioning reticle 56. The opening 52 is substantially
smaller than the size of the detector 14. The opening 52 can be in
any unique shape that can form an image readily recognizable in the
display. The reticle 56 is placed at a distance from the focal
point 44 and blocks all x-ray beam transmitted from the x-ray
source 12 except a small portion 15 through the small opening 52 in
the reticle 56.
[0032] When the detector 14b is not properly positioned in an x-ray
field, the projection of the x-ray beam passing through the small
reticle is off a pre-defined position, e.g., the center of the
detector 14b. This can be readily recognized by an image off a
pre-defined position, e.g., an off-center image 60b formed on the
display 24b. The detector 14b is then adjusted either manually or
by remote control, for example, by translating the detector in a
plane. Alternatively, the x-ray source 44 can be independently
translated in a plane in a search mode. The fluoroscopic imaging
system used in the present invention makes possible of real-time
display of images generated during the adjustment of the detector
14 and/or x-ray source 12 in various positions. By adjusting the
detector and/or the x-ray source, and determining the images shown
on the display, the detector can be properly positioned in the
x-ray field. Once the detector 14 is properly positioned in the
x-ray field, the projection of the x-ray beam 15 is on the
pre-defined position, e.g., the center of the detector 14, which is
indicated by an image 60 in the pre-defined position, e.g., the
center of the display 24.
[0033] FIG. 7 illustrates a block diagram showing a method of
positioning an imaging system in accordance with one embodiment of
the present invention. At step 100, a positioning reticle is
provided in front of an x-ray source. The positioning reticle is
provided with an opening that is substantially smaller than the
size of the detector so that only a small portion of an x-ray beam
passes through the positioning reticle. The size of the opening can
be selected based on specific applications. At step 110, the x-ray
source is actuated and transmits an x-ray beam to the positioning
reticle. The x-ray beam is blocked by the positioning reticle
except for a small portion of the beam, which passes through the
opening in the reticle to a region of interest. The portion of the
x-ray beam is received and detected in the detector as shown in
step 120, which converts the x-ray beam to electrical signals
representing the intensity of the x-ray beam passing through the
object of the interest. At step 130, the image formed by the
electrical signals is determined as to its position or location on
the display. If the image is not in the pre-defined position, e.g.,
center of the display, the detector and/or the x-ray source is
adjusted by for example translating the detector and/or x-ray
source in a plane. Then steps 100-130 are repeated until the image
is in the pre-defined position, e.g., the center of the
display.
[0034] FIG. 8 illustrates a block diagram showing a method of
aligning a detector with an x-ray source in accordance with an
embodiment of the present invention. At step 200, an alignment
reticle is provided in front of an x-ray source. The alignment
reticle is provided with an opening to allow a portion of an x-ray
beam passing therethrough. The opening can be in the shape of a
square, an elongated slot, a circle etc. Alternative, the alignment
reticle is a block having a plurality of holes or openings forming
a readily determinable configuration such as a square or circle. At
step 210, the x-ray source is actuated and transmits an x-ray beam
to the alignment reticle. A portion of the x-ray beam passes
through the opening in the reticle to a region of interest. The
x-ray beam passing through the region of interest is received and
detected in the detector as shown at step 220, which converts the
x-ray beam to electrical signals representing the intensity of the
x-ray beam passing through the object of the interest. At step 230,
the image formed by the electrical signals is determined as to its
location on the display. If the image is not at the pre-defined
position, e.g., the center of the display, the detector and/or the
x-ray source are adjusted by for example translating, rotating
and/or tilting. Then steps 200-230 are repeated until the image is
on the pre-defined position, e.g., the center of the display.
[0035] FIG. 9 illustrates a block diagram showing a method of
aligning an imaging system in accordance with another embodiment of
the present invention. At step 300, an x-ray beam is modulated by a
radio frequency base wave. At step 310, the phase angles of the
modulated beam are detected by two or more RF receivers provided in
the detector.
[0036] If the phase angles of the RF base wave arrived at the two
or more RF receivers are different, the detector and/or x-ray
source are adjusted by translating, rotating and/or tilting. The
steps 300-310 are repeated until the phase angles are equal.
[0037] From the foregoing it will be appreciated that, although
specific embodiments of the invention have been described herein
for purposes of illustration, various modifications may be made
without deviating from the spirit and scope of the invention.
* * * * *