U.S. patent application number 13/027857 was filed with the patent office on 2011-06-09 for apparatus and method for reconstruction of volumetric images in a divergent scanning computed tomography system.
Invention is credited to Richard K. Grant, Eugene A. Gregerson, Norbert J. Johnson.
Application Number | 20110135054 13/027857 |
Document ID | / |
Family ID | 31946812 |
Filed Date | 2011-06-09 |
United States Patent
Application |
20110135054 |
Kind Code |
A1 |
Gregerson; Eugene A. ; et
al. |
June 9, 2011 |
APPARATUS AND METHOD FOR RECONSTRUCTION OF VOLUMETRIC IMAGES IN A
DIVERGENT SCANNING COMPUTED TOMOGRAPHY SYSTEM
Abstract
An apparatus and method for reconstructing image data for a
region are described. A radiation source and multiple
one-dimensional linear or two-dimensional planar area detector
arrays located on opposed sides of a region angled generally along
a circle centered at the radiation source are used to generate scan
data for the region from a plurality of diverging radiation beams,
i.e., a fan beam or cone beam. Individual pixels on the discreet
detector arrays from the scan data for the region are reprojected
onto a new single virtual detector array along a continuous
equiangular arc or cylinder or equilinear line or plane prior to
filtering and backprojecting to reconstruct the image data.
Inventors: |
Gregerson; Eugene A.;
(Bolton, MA) ; Grant; Richard K.; (Sudbury,
MA) ; Johnson; Norbert J.; (North Andover,
MA) |
Family ID: |
31946812 |
Appl. No.: |
13/027857 |
Filed: |
February 15, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11514727 |
Aug 31, 2006 |
7903779 |
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13027857 |
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10645323 |
Aug 21, 2003 |
7106825 |
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11514727 |
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60405096 |
Aug 21, 2002 |
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Current U.S.
Class: |
378/19 |
Current CPC
Class: |
Y10S 378/901 20130101;
G06T 11/005 20130101 |
Class at
Publication: |
378/19 |
International
Class: |
H05G 1/60 20060101
H05G001/60; H05G 1/64 20060101 H05G001/64 |
Claims
1. A method of imaging an object using radiation, comprising:
obtaining projection data from at least one real detector array,
the at least one real detector array obtaining projection data at
two or more positions on a gantry, and having a geometry that is
neither equilinear nor equiangular; reprojecting the projection
data from at least one real detector array onto a virtual detector
having virtual pixels that are spaced either equilinearly or
equiangularly; and reconstructing the reprojected data from the
virtual detector array.
2. The method of claim 1, wherein the at least one real detector
array comprises two or more detectors configured to obtain
projection data at two or more positions.
3. The method of claim 1, wherein the at least one real detector
array comprises at least one detector that is movable to obtain
projection data at two or more positions.
4. The method of claim 1, further comprising: projecting radiation
from a source onto the at least one real detector array.
5. The method of claim 4, wherein the radiation comprises x-ray
radiation.
6. The method of claim 1, wherein the virtual detector array is
equilinear.
7. The method of claim 1, wherein the virtual detector array is
equiangular.
8. The method of claim 1, wherein reprojecting the projection data
onto a virtual array comprises: for each virtual pixel, determining
a corresponding real detector pixel in a real detector array that
is intersected by a line connecting the virtual pixel to the source
of projected radiation; and using a radiation amplitude value
detected at the corresponding real detector pixel to determine a
radiation amplitude value for the virtual pixel.
9. The method of claim 8, wherein determining a radiation amplitude
value for the virtual pixel comprises interpolating a value from
the radiation amplitude values of the corresponding real detector
pixel and neighboring real detector pixels.
10. The method of claim 1, further comprising: filtering data from
the virtual detector array; and backprojecting data from the
virtual detector array.
11. The method of claim 1, wherein the at least one real detector
array comprises at least one one-dimensional line detector.
12. The method of claim 1, wherein the at least one real detector
array comprises at least one two-dimensional flat panel
detector.
13. A system for imaging an object using radiation, comprising: a
source of radiation; at least one real detector array that obtains
projection data at two or more positions on a gantry, and has a
geometry that is neither equilinear nor equiangular; and a data
process for reprojecting the projection data from the at least one
real detector array onto a virtual detector array having virtual
pixels that are spaced either equilinearly or equiangularly, and
for reconstructing the reprojected data from the virtual detector
array.
14. The system of claim 13, wherein the source comprises an x-ray
source.
15. The system of claim 13, wherein the at least one real detector
array comprises at least one one-dimensional line detector.
16. The system of claim 13, wherein the at least one real detector
array comprises at least one two-dimensional flat panel
detector.
17. The system of claim 13, wherein the virtual detector array is
equilinear.
18. The system of claim 13, wherein the virtual detector array is
equiangular.
19. The system of claim 13, wherein the at least one real detector
array comprises at least two detectors configured to obtain
projection data at two or more positions.
20. The system of claim 19, wherein the at least two detectors are
disposed end-to-end, and angled relative to one another to
approximate an arc having a radius centered at a focal spot of the
source.
21. The system of claim 13, wherein the at least one real detector
array comprises at least one detector movable to two or more
positions to obtain projection data.
22. The system of claim 13, wherein the data process reprojects
data by assigning a radiation amplitude value to each virtual pixel
based upon a measured radiation amplitude value of a corresponding
real pixel that intersects a line between the virtual pixel and the
radiation source.
Description
RELATED APPLICATIONS
[0001] This application is a continuation U.S. application Ser. No.
11/514,727, filed Aug. 31, 2006, which is a continuation of U.S.
application Ser. No. 10/645,323, filed Aug. 21, 2003, now U.S. Pat.
No. 7,106,825, which claims the benefit of U.S. Provisional
Application No. 60/405,096, filed Aug. 21, 2002. The entire
teachings of the above applications are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to 2D and 3D
computerized tomography (CT). In particular this invention relates
to methods and systems for reconstructing projection data which are
neither equilinear or equiangular in nature.
[0003] In conventional computerized tomography for both medical and
industrial applications, an x-ray fan beam and an equilinear or
equiangular array detector are employed. Two-dimensional (2D) axial
imaging is achieved. While the data set is complete and image
quality is correspondingly high, only a single slice of an object
is imaged at a time. When a 3D image is acquired, a "stack of
slices" approach is employed. Acquiring a 3D data set one slice at
a time is inherently slow. Moreover, in medical applications,
motion artifacts occur because adjacent slices are not imaged
simultaneously. Also, dose utilization is less than optimal,
because the distance between slices is typically less than the
x-ray collimator aperture, resulting in double exposure to many
parts of the body.
[0004] In a system employing true cone-beam geometry, a cone-beam
x-ray source and a flat 2D equilinear or curved 2D equiangular area
detector are employed. An object is scanned, preferably over a
360-degree range, either by moving the x-ray source in a scanning
circle around the object while keeping the 2D area detector fixed
with reference to the source, or by rotating the object while the
source and detector remain stationary. In either case, it is the
relative movement between the source and object which affects
scanning Compared to the 2D "stack of slices" approach for 3D
imaging, the cone-beam geometry has the potential to achieve rapid
3D imaging of both medical and industrial objects, with improved
dose utilization.
[0005] The cone-beam geometry for 3D imaging has been discussed
extensively in the literature, as represented by the following: M.
Schlindwein, "Interactive Three-Dimensional Reconstruction from
Twin Cone-Beam Projections", IEEE Trans Nucl. Sci., Vol. NS-25, No.
5, pp. 1135-1143 (October 1978); Gerald N. Minerbo, "Convolutional
Reconstruction from Cone-Beam Projection Data", IEEE Trans. Nucl.
Sci., Vol. NS-26, No. 2, pp. 2682-2684 (April 1979); Heang K. Tuy,
"An Inversion Formula for Cone-Beam Reconstruction", SIAM J. Math,
Vol. 43, No. 3, pp. 546-552 (June 1983); L. A. Feldkamp, L. C.
Davis, and J. W. Kress, "Practical Cone-Beam Algorithm", J. Opt.
Soc. Am. A., Vol. 1, No. 6, pp. 612-619, (June 1984); Bruce D.
Smith, "Image Reconstruction from Cone-Beam Projections: Necessary
and Sufficient Conditions and Reconstruction Methods", IEEE Trans.
Med. Imag., Vol. MI-44, pp. 14-24 (March 1985); and Hui Hu, Robert
A. Kruger, and Grant T. Gullberg, "Quantitative Cone-Beam
Construction", SPIE Medical Imaging III: Image Processing, Vol.
1092, pp. 492-501 (1989).
[0006] Several methods for collecting cone beam data have been
developed. One technique involves acquiring volumetric image data
using a flat panel matrix image receptor, as described in U.S. Pat.
No. 6,041,097 to Roos, et al. Another method uses image
intensifier-based fluoroscopic cameras mounted on a CT-gantry type
frame. Such a system is described in a paper presented at SPIE
Medical Imaging Conference on Feb. 24 1997, by R. Ning, X. Wang,
and D. L. Conover of Univ. of Rochester Medical Center.
[0007] U.S. Pat. No. 5,319,693 to Eberhard, et al. discusses
simulating a relatively large area detector using a relatively
small area detector by either moving the actual area detector
relative to the source, or moving the object relative to the
detector.
[0008] However, there is a significant limitation of cone-beam
reconstruction when individual flat detectors are reconstructed
independently. Simply combining separate reconstructed portions of
the object from independently processed projections results in an
image characterized by discontinuous jumps between the various
projections. Alternatively, one could first combine the discreet
data sets from each detector into a new single data set that is
then reconstructed. However, by simply combining the data into a
larger data array and performing standard reconstruction
techniques, the data elements in the new data set are not equally
spaced. Thus, the resultant images will be distorted geometrically,
or the dynamic range of the reconstructed data set will not
represent the true transmission values of the object being
imaged.
SUMMARY OF THE INVENTION
[0009] The deficiencies in existing methods for combining image
data from multiple flat panel detector arrays result from the fact
that these detector arrays have neither equilinear nor equiangular
geometries. The present invention relates to improved systems and
methods for reconstructing projection data, including x-ray
projection data for two-dimensional (2D) fan-beam and
three-dimensional (3D) cone beam CT imaging, in which the geometry
of the detectors is neither equilinear or equiangular, by
reprojecting the actual measured data into a new virtual data
array, which has an equilinear or equiangular geometry. In one
aspect, multiple discreet projection data sets, which, when
combined, are neither equilinear or equiangular, are reprojected
into a new virtual data set on an equilinear spaced detector on a
line or plane, or an equiangular spaced detector array on an arc or
cylinder. The resulting virtual projection data set can then be
reconstructed using standard backprojection techniques and generate
images which are geometrically correct, and represent the true
x-ray transmission properties of the object being imaged.
[0010] In one embodiment, the projection data from two or more 1D
linear or 2D flat detector arrays are reprojected onto a single
equilinear or equiangular virtual detector array prior to filtering
and backprojecting the projection data.
[0011] In another embodiment, the projection data from two or more
discrete detector positions are reprojected onto a virtual detector
array having an equilinear or equilangular configuration, and the
reprojected data is reconstructed to provide an image.
[0012] The "virtual" detector array of the present invention is a
data array comprising a plurality of pixels, having an equilinear
or equiangular geometry, where the data values assigned to each
pixel in the virtual array is based upon data from an actual
detector or set of detectors having a non-equilinear and
non-equiangular geometry.
[0013] The present invention advantageously allows for the 2D and
3D tomographic reconstruction of objects. This invention enables
divergent x-ray 2D fan beam or 3D cone beam tomographic
reconstruction using a discrete number of 1D linear or 2D flat
detectors angled relative to one another by using a novel rebinning
and reprojection technique onto virtual equilinear or equiangular
detector arrays prior to performing standard filtered
backprojection tomographic reconstruction techniques.
[0014] The present invention is particularly useful for medical
imaging applications, as well as numerous industrial applications,
such as testing and analysis of materials, inspection of
containers, and imaging of large objects.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The foregoing and other objects, features and advantages of
the invention will be apparent from the following more particular
description of preferred embodiments of the invention, as
illustrated in the accompanying drawings in which like reference
characters refer to the same parts throughout the different views.
The drawings are not necessarily to scale, emphasis instead being
placed upon illustrating the principles of the invention.
[0016] FIG. 1 shows standard equilinear and equiangular geometries
used in various generations of CT scanners;
[0017] FIG. 2 shows a standard equilinear detector geometry in
which the detectors are arranged with constant spacing along a line
or plane;
[0018] FIG. 3 shows the radiation profile of an imaged object
defined by an equilinear arrangement of detectors;
[0019] FIG. 4 shows a standard equiangular detector geometry in
which the detectors are arranged with constant angular spacing
along an arc or cylindrical surface;
[0020] FIG. 5 shows the radiation profile of an imaged object
defined by an equiangular arrangement of detectors;
[0021] FIG. 6 shows three equilinear-spaced detector arrays
positioned and angled relative to one another, resulting in a
geometry that is neither equilinear nor equiangular;
[0022] FIG. 7 shows the predicted radius of reconstructed object
with three detector arrays generally positioned along an arc having
a radius centered at the x-ray focal spot;
[0023] FIG. 8 shows the predicted radius of reconstructed object
with three 1D linear or 2D flat plate detector arrays positioned
along a straight line in an equilinear arrangement;
[0024] FIG. 9 is a flow chart diagram of the rebinning algorithm
for reconstructing 1D fan beam or 2D cone beam projection data
which is neither equilinear or equiangular;
[0025] FIG. 10 shows the projection of multiple angled detector
array positions onto a single virtual flat equilinear detector
array;
[0026] FIG. 11 shows the projection of multiple angled detector
array positions onto a single virtual curved equiangular detector
array; and
[0027] FIG. 12 is a schematic diagram of an x-ray scanning system
having a gantry positioning apparatus mounted to a cantilevered
O-shaped gantry and a mobile cart.
DETAILED DESCRIPTION OF THE INVENTION
[0028] A description of preferred embodiments of the invention
follows.
[0029] Referring to FIG. 1, equilinear and equiangular detector
geometries are depicted. A radiation source 13 projects radiation
onto multiple one-dimensional linear or two-dimensional planar area
detector arrays 14 that are angled generally along line or a
circle. The detector arrays generate scan data from a plurality of
diverging radiation beams, i.e., a fan beam or cone beam. The
source and detectors are rotated around the object to be imaged,
and a plurality of projection images is captured to computer memory
for tomographic projection image processing.
[0030] In the case of an equilinear geometry, a single source
produces a fan or cone beam which is read by a linear 1D or 2D
array of detectors, as shown on the left. In the case of an
equiangular geometry, such as shown on the right, the detectors
occupy a 1D arc to image fan beam data, or a 2D cylindrical surface
to image cone beam data.
[0031] Referring to FIGS. 2-3, an equilinear detector geometry is
more clearly defined. As shown in FIG. 2, the detector elements in
an array are arranged with constant spacing along a straight line
or a flat plane. The angle between rays connecting the x-ray source
point and the detector elements does not remain constant. A
radiation absorption profile, or image, is generated with varying
amplitudes for a region between the bank of detectors and the x-ray
source, as shown in FIG. 3. Each ray is identified by its distance,
s, from the projection of the central ray (s=0), and the absorption
profile is denoted by the function Rb(s).
[0032] FIGS. 4-5 illustrate an equiangular detector geometry. As
illustrated in FIG. 4, the detector elements in an equiangular
array are arranged with constant angular spacing along a circle or
cylinder. In an equiangular geometry, in contrast to equilinear
geometry, the angle between rays connecting the x-ray source point
and the detector elements remains constant, but the distance
between detectors may change. FIG. 5 shows the radiation absorption
profile for the region between the bank of detectors and the x-ray
source. Each ray is identified by its angle, g, from the central
ray, and the absorption profile is denoted by the function
Rb(g).
[0033] In many radiation imaging applications, it is desirable to
image objects that are wider than the field-of-view of the detector
array. One method for achieving a wide field-of-view is to use
multiple 1D or 2D detectors, arranged end-to-end and angled
relative to one another, as shown in FIG. 6. Another technique is
to use a single array, translated to discrete positions along an
arc opposite the x-ray source, to obtain a large "effective" field
of view. In either case, when one or more equilinear 1D linear fan
beam or 2D planar cone beam detector arrays are positioned and
angled along an arc opposite the x-ray source, the resulting
geometry is neither equilinear or equiangular. As illustrated in
FIG. 6, the projection of equally spaced detector elements, dj, on
the angled arrays do not project onto equally spaced detectors, pj,
located on lines, planes, or arcs. For example, assuming the
detector elements on the tilted arrays are equally spaced, the
process of reprojecting these elements onto a new virtual detector
array which is coincident or parallel to the central detector array
will result in projections that are not equidistant. Hence,
assuming the Fourier transform filtering is performed continuously
along the axes of the angled arrays without resampling, the spacing
of detector arrays cannot be assumed to be equal.
[0034] FIG. 7 shows in more detail the result of filtering on
non-equally spaced detectors. The predicted radius of a
reconstructed object, Rr, is calculated on an angled detector
geometry, assuming filtering is performed without resampling onto
an equilinear array. If we assume that the scanner focal length,
FL, is 1000 mm, and the length of the detectors, L, is 400 mm, then
qr=2*arctan((L/2)/FL)=0.395 rad=22.632 deg., and Rr=(FL/2)*sin
qr=192.31 mm.
[0035] FIG. 8 illustrates this same calculation of the predicted
radius of the reconstructed object assuming the same input
parameters of focal length and detector length, but where the
detector arrays are arranged in a plane to provide equilinear
geometry. Here, qa=arctan(L/FL)=0.3804 rad=21.795 deg., and
Ra=(FL/2)*sin qa=185.695 mm. The predicted radius of the angled
detector geometry is larger than that of the equilinear detector
geometry, and the resultant images with the angled detector
geometry will be distorted geometrically.
[0036] This problem can be overcome by reprojecting and resampling
the data from the angled detector arrays onto a "virtual"
equilinear or equiangular array. The algorithm shown in FIG. 9
describes a method of reconstructing fan beam or cone beam x-ray
projection data of an object, where the detector configuration is
neither equilinear or equiangular. In particular, the algorithm
describes a method for generating a new virtual equilinear or
equiangular fan beam or cone beam detector array which is defined
along a straight line or generally along an arc. For every pixel
defined in the virtual detector array, the projection point in the
original projection data is determined and the x-ray absorption
amplitude for that point is calculated by interpolating the nearest
neighbor pixels. Once resampling is completed, standard filtered
backprojection and algebraic reconstruction techniques may be
performed to generate image data.
[0037] The method consists of creating a single virtual detector
array for each projection position, which is defined as being
equilinear or equiangular, and reprojecting two more real detector
arrays onto the virtual array. Once the real projection data is
reprojected onto the virtual detector, the data is filtered and
backprojected using standard tomographic reconstruction
techniques;
[0038] As shown in step 101 of FIG. 9, the projection angle index,
iproj, is first assigned the value 1. At step 102, the x-ray source
and detector array(s) are moved to a projection angle relative to
the object being imaged. This can be accomplished by either moving
the source and detector relative to a stationary object (preferably
by moving the source and detector in a circle or arc around the
object), or by keeping the source and detector stationary and
rotating the object to the desired projection angle.
[0039] The projection data can obtained for a plurality of
projection angles (1 . . . nproj), preferably at a plurality of
equally spaced angles as the source/detector and object are rotated
360 degrees with respect to each other.
[0040] At step 103, a new virtual equilinear or equiangular array,
P, is allocated. The virtual array, P, includes virtual pixels
which are equally spaced in distance along a line or plane in the
case of a virtual equilinear array, or equally spaced in angle
along an arc or curved plane in the case of a virtual equiangular
array.
[0041] At step 104, the real projection data, D, from each real
detector array (1 . . . ndet) is acquired for the given projection
angle, iproj.
[0042] For each real detector array, D, the real projection data is
then reprojected onto the virtual array, P, at step 107.
[0043] As shown at steps 108-115, the reprojection subroutine
includes looping through each virtual pixel in the virtual array,
P, (step 109), and for each virtual pixel, determining the real
detector pixel, d, that is intersected by the line connecting the
virtual pixel and the x-ray source (step 111).
[0044] Once this actual pixel, d, is determined, an interpolation
technique then is applied to d and its nearest neighbors on the
real detector array to compute an x-ray absorption amplitude value
to be assigned to the virtual pixel, p (step 112). This process is
repeated until absorption amplitude values have been assigned to
each of the virtual pixels in the virtual array.
[0045] Once each of the real detector arrays has been projected
onto a virtual equilinear or equiangular array, data from the
virtual detector array is then filtered at step 117 and
backprojected at step 118. As the name implies, there are two steps
to the filtered backprojection algorithm: the filtering step, which
can be visualized as a simple weighting of each Fourier transformed
projection in the frequency domain, and the backprojection step,
which can be seen as the dual, or in a more strict mathematical
sense, the adjoint, of projection. Instead of projecting density
values to a projection value, a projection value is backprojected,
or smeared out, over the image points along the ray. This entire
process is then repeated for each of the projection angles.
[0046] Referring to FIGS. 10 and 11, the process of reprojecting
x-rays onto virtual equilinear and equiangular detector arrays is
schematically illustrated. In FIG. 10, once actual projection
images are captured, a new equilinear virtual detector is allocated
and defined along a one-dimensional line in the case that a fan
beam geometry, or along a two-dimensional flat plane in the case of
a cone beam geometry. In FIG. 11, the images are captured by the
actual three-panel detector array, and then a new equiangular
virtual detector is allocated. The equiangular virtual detector is
an arc in the case of a fan beam geometry, and a curved cylindrical
surface in the case of a cone beam geometry. In all of these
embodiments, the new virtual array assumes that detector elements
are equally spaced in distance or angle, respectively. For each
detector element in the virtual array, the projected position in
the real detector arrays is computed and an interpolation technique
is applied to nearest neighbors on the real array to compute the
correct x-ray absorption amplitude of the object to be
reconstructed. Once the real detector arrays have been projected
onto the virtual detector array, standard filtered backprojection,
algebraic reconstruction techniques, and other tomographic imaging
algorithms may be applied to generate image data of an object.
[0047] In the examples shown here, the real detector array
comprises three flat panel detectors arranged end-to-end, and
angled to approximate an arc having a radius centered on the focal
spot of the radiation source. It will be understood, however, that
the principles of the invention can be used with actual detectors
having any number of detector elements, including both 1D line
detectors and 2D panel detectors, where the geometry of the actual
detector is neither equilinear or equiangular. In addition, the
principles of the present invention can be advantageously employed
in a system where one or more detectors are movable to various
discrete positions along a line or arc relative to the x-ray
source, such as described in co-pending U.S. patent application
Ser. No. 10/392,365, filed on Mar. 18, 2003, the entire teachings
of which are incorporated herein by reference. The principles of
the present can also be used in a system in which the source and
detector are tiltable about the focal spot of the source to obtain
a larger field-of-view in the axial direction, such as described in
co-pending U.S. application entitled "Cantilevered Gantry
Positioning Apparatus for X-Ray Imaging System"(U.S. patent
application Ser. No. 10/645,322), filed on even date herewith, the
entire teachings of which are incorporated herein by reference.
FIG. 12 is a schematic diagram showing an x-ray scanning system 10
described in U.S. patent application Ser. No. 10/645,322. The x-ray
scanning system 10 includes a gantry 11 secured to a support
structure, which could be a mobile or stationary cart, a patient
table, a wall, a floor, or a ceiling. The x-ray scanning system 10
can be used to obtain two-dimensional planar or three-dimensional
computerized tomographic (CT) x-ray images of an object, such as a
patient. In the embodiment shown in FIG. 12, the gantry 11 is a
generally circular, or "0-shaped," housing having a central opening
into which an object being imaged is placed. It will be understood
that various other gantry configurations, such as a "C-shaped"
gantry, can also be employed. In one embodiment, the gantry 11
contains an x-ray source (such as a rotating anode pulsed x-ray
source) that projects a beam of x-ray radiation into the central
opening of the gantry, through the object being imaged, and onto a
detector array (such as a flat panel digital detector array)
located on the opposite side of the gantry. The x-rays received at
the detector can then be used to produce a two-dimensional or
three-dimensional image of the object using well-known techniques.
The x-ray source is able to rotate around the interior of the
gantry 11 in a continuous or step-wise manner so that the x-ray
beam can be projected through the object, and through a common
isocenter, at various angles over a partial or full 360 degree
rotation. The detector array is also rotated around the interior of
the gantry, in coordination with the rotation of the x-ray source,
so that for each projection angle of the x-ray source, the detector
array is positioned opposite the x-ray source on the gantry. The
apparatus is thus able to obtain high-quality x-ray images of the
targeted object in any projection plane over a partial or full 360
degree rotation.
[0048] While this invention has been particularly shown and
described with references to preferred embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
scope of the invention encompassed by the appended claims.
[0049] Also, while the embodiments shown and described here relate
in general to medical imaging, it will be understood that the
invention may be used for numerous other applications, including
industrial applications, such as testing and analysis of materials,
inspection of containers, and imaging of large objects.
[0050] While this invention has been particularly shown and
described with references to example embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
scope of the invention encompassed by the appended claims.
* * * * *