Ultrahigh resolution interferometric x-ray imaging
First Claim
1. Apparatus for producing an image that describes the internal structure of an object, comprisinga source of x-rays,an x-ray image detector;
- improved by its further comprisingthree very-thin slab-shaped volumes, SV1, SV2, and SV3, each with substantially-planar slab faces oriented relative to each other to be substantially-mutually-parallel, and each containing an associated very-thin material structure that interacts with x-rays, andmeans for limiting the energy-bandwidth of detected x-rays;
wherein said three contained structures are positioned between said source and said detector so that x-rays from said source propagate in the sequential order, first through said structure within slab-volume SV1, next through said structure within slab-volume SV2, next through said object, next into slab-volume SV3, and then are detected; and
wherein the directions x and y are both parallel to the substantially-parallel faces of said three slab-volumes; and
wherein said material structures within slab-volumes SV1, and SV2 are fabricated to be spatially-periodic within their associated useful x-direction widths, respectively with associated spatial periods a1x and a2x, and oriented within the apparatus so that each structure'"'"'s respective periodicity-direction that is associated with said respective period lies in the direction x; and
wherein the perpendicular distance between slab-volume SV1 and slab-volume SV2 is R1 and the perpendicular distance between slab-volume SV2 and slab-volume SV3 is R2 ; and
wherein b, q, and p are positive integers; and
wherein a1x is accurately related to a2x by
space="preserve" listing-type="equation">a.sub.1x =b a.sub.2x (R.sub.1 +R.sub.2)(q p R.sub.2).sup.-1 ;
andwherein, when said object is absent, and for x-rays with at least one specific energy value that lies within said energy-bandwidth, and throughout the associated useful x-direction width of said material structure within slab-volume SV3, then the two structures respectively within slab-volumes SV1 and SV2 acting together but not separately project onto slab-volume SV3 an x-ray intensity distribution that is substantially spatially-periodic in direction x with the spatial period aPx and has a substantial spatial intensity variation; and
wherein when the greatest common integer divisor of b and q is 1, then the period aPx is accurately related to a2x by
space="preserve" listing-type="equation">a.sub.Px =a.sub.2x (R.sub.1 +R.sub.2)(q p R.sub.1).sup.-1.
0 Assignments
0 Petitions
Accused Products
Abstract
The Invention provides practical apparatus and methods for significant improvements to conventional radiography practice. It can image objects having negligible x-ray absorption contrast e.g. otherwise x-ray transparent low-Z artifacts such as human soft-tissue, by obtaining edge-enhanced contrast from an object'"'"'s (BDY) x-ray refractive-index gradients. In mammography, the contrast of small micro-calcifications is increased typically 4-fold, or more. It can be "tuned" to obtain element-selective refractive-index enhanced contrast to resonantly image minute quantities of a specific element with Z≈35-56 and only that element. With only a single brief x-ray exposure it can produce two independent images, e.g. of the object'"'"'s x-ray absorption and refractive-index distributions. It virtually eliminates the blurring and contrast reducing effects of x-ray scatter, especially of very small-angle scatter. It does not use a Bucky grid, and the associated increase in effective detector quantum efficiency results in a significant decrease in image quantum mottle. It can produce CT scan 3D images with a much reduced scanning time. The Invention provides radiograms with greatly improved resolution, contrast and versatility, and edge-enhanced features. It operates via the fractional Talbot effect using two pre-object microfabricated gratings (G1, G2) and a detector (D) preferably containing a periodic pixel array. It further includes an in-situ laser interferometer for aligning the gratings (G1, G2) to the detector (D). While the Invention has a wide range of application, it is ideally suited for medical imaging of biological soft-tissue, and especially for mammography, angiography, and CT (or CAT) scans.
-
Citations
100 Claims
-
1. Apparatus for producing an image that describes the internal structure of an object, comprising
a source of x-rays, an x-ray image detector; improved by its further comprising three very-thin slab-shaped volumes, SV1, SV2, and SV3, each with substantially-planar slab faces oriented relative to each other to be substantially-mutually-parallel, and each containing an associated very-thin material structure that interacts with x-rays, and means for limiting the energy-bandwidth of detected x-rays; wherein said three contained structures are positioned between said source and said detector so that x-rays from said source propagate in the sequential order, first through said structure within slab-volume SV1, next through said structure within slab-volume SV2, next through said object, next into slab-volume SV3, and then are detected; and wherein the directions x and y are both parallel to the substantially-parallel faces of said three slab-volumes; and wherein said material structures within slab-volumes SV1, and SV2 are fabricated to be spatially-periodic within their associated useful x-direction widths, respectively with associated spatial periods a1x and a2x, and oriented within the apparatus so that each structure'"'"'s respective periodicity-direction that is associated with said respective period lies in the direction x; and wherein the perpendicular distance between slab-volume SV1 and slab-volume SV2 is R1 and the perpendicular distance between slab-volume SV2 and slab-volume SV3 is R2 ; and wherein b, q, and p are positive integers; and wherein a1x is accurately related to a2x by
space="preserve" listing-type="equation">a.sub.1x =b a.sub.2x (R.sub.1 +R.sub.2)(q p R.sub.2).sup.-1 ;and wherein, when said object is absent, and for x-rays with at least one specific energy value that lies within said energy-bandwidth, and throughout the associated useful x-direction width of said material structure within slab-volume SV3, then the two structures respectively within slab-volumes SV1 and SV2 acting together but not separately project onto slab-volume SV3 an x-ray intensity distribution that is substantially spatially-periodic in direction x with the spatial period aPx and has a substantial spatial intensity variation; and wherein when the greatest common integer divisor of b and q is 1, then the period aPx is accurately related to a2x by
space="preserve" listing-type="equation">a.sub.Px =a.sub.2x (R.sub.1 +R.sub.2)(q p R.sub.1).sup.-1.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59)
- 29. Apparatus of claim 24 wherein n is a positive integer, and wherein a2x is approximately equal to
- space="preserve" listing-type="equation">(m.sub.* /n).sup.1/2 (hc R.sub.1 R.sub.2 /E.sub.X).sup.1/2 (R.sub.1 +R.sub.2).sup.-1/2.
30.
- 30. Apparatus of claim 24 wherein n is a positive integer, and wherein a2x is approximately equal to
- space="preserve" listing-type="equation">(2/n).sup.1/2 (hc R.sub.1 R.sub.2 /E.sub.X).sup.1/2 (R.sub.1 +R.sub.2).sup.-1/2.
- and
wherein there is an imaginary line-segment with the length a2y oriented in the direction y on slab-volume SV2 that thereby spans one y-direction period of said structure within slab-volume SV2; and wherein said y-directed line-segment starts and ends on boundaries of said surface-projected areas; and wherein said y-directed line-segment crosses through m* of said surface-projected areas; and wherein, in crossing surface-projected area boundaries between associated discrete portions, said y-directed line-segment is divided approximately equally into m* y-directed line-segment fractions by said area boundaries; and wherein each said y-directed line-segment fraction has approximately the length a2y /m* ; and wherein said crossed associated discrete portions are numbered sequentially and monotonically starting with the value 0 by the associated integer index jy in passing from one end of said y-directed line-segment to the other end; and wherein said indices jy form a monotonic integer sequence starting the value 0 and ending with the value m* -1; and wherein index jy assumes only discrete values that are greater than -1 and are less than m* ; and wherein index jy assumes any one such discrete value once and only once in said sequence; and wherein each value of index jy has an associated accompanying index ky ; and wherein said association of index jy with index ky associates index ky with said numbered discrete portion; and wherein said accompanying index ky also has only m* possible discrete values; and wherein said sequence of values for index jy and said association of each index jy with index jy provides an associated sequence of values for ky ; and wherein the set of discrete values assumed by the index ky is the same set of discrete values assumed by the integer jy so that index ky assumes only discrete values that are greater than -1 and are less than m*, and so that index ky assumes any one value within said set once and only once; and wherein the relationship between ky and jy is jy = (n* ky) modulo m* !; and wherein said relationship between ky and jy provides that said sequence of values for jy and said associated sequence of values for ky are either the same sequence as each other or are a permutation of each other; and wherein each and every discrete portion of said structure within slab-volume SV2 each has an additional associated pair of indices jy and ky so that each and every discrete portion of said structure within slab-volume SV2 thereby has four associated indices jx, kx, jy, and ky ; and wherein the indices jy and ky are arranged so that the values of the indices jy and ky are associated with said discrete portions in a spatially periodic arrangement, and so that the associated sequences of jy and ky values, encountered on any two such y-directed imaginary line-segments that are each of length a2y and are each starting and ending on boundaries of said surface-projected areas, are the same as each other when said two y-directed line-segments are aligned on the same straight line and spaced from each other by a distance that is an integral multiple of a2y ; and wherein, when x-rays with the approximate energy E* propagate along a single very thin path through slab-volume SV2, and when said very thin path is through a surface-projected area with associated indices kx and ky, then said x-rays obtain a value for said refraction-induced phase shift that occurs in addition to the phase shift experienced in vacuum has a value that is approximately equal to the value given in radians by
space="preserve" listing-type="equation">π
n.sub.* r.sub.* k.sub.x -(k.sub.x.sup.2 m.sub.*.sup.-1)+k.sub.y -(k.sub.y.sup.2 m.sub.*.sup.-1)!-2φ
.sub.*.
- and
wherein the detector-pixel front surfaces interact with x-rays in a manner that results in the detection and measurement of the spatial distribution of the intensity of said x-rays incident on said image detector; and wherein said array of detector-pixels is spatially periodic in direction x so that centroids of the front surfaces of adjacent detector-pixels within said spatially-periodic array are periodically spaced from each other in the direction y by the distance aDx ; and wherein u is a positive even integer.
- and
wherein the spatial phase of said spatially periodic x-ray intensity distribution projected, when said object is absent, onto slab-volume SV3 with period aPx is carefully aligned with the phase of said detector-pixel array.
- and
wherein, when said object is absent, and for x-rays with at least one energy value that lies within said energy-bandwidth and throughout the associated useful y-direction width of said material structure within slab-volume SV3, then the structures within slab-volumes SV1 and SV2 acting together but not separately project onto slab-volume SV3 an x-ray intensity distribution that is additionally substantially spatially-periodic in direction y with the spatial period aPy ; and wherein when the greatest common integer divisor of b and q is 1, then the period aPy is accurately related to a2y by
space="preserve" listing-type="equation">a.sub.Py =a.sub.2y (R.sub.1 +R.sub.2)(q p R.sub.1).sup.-1,and wherein aDy is accurately related to aPy by aDy =(v/u) aPy ; and wherein the spatial phase of said spatially periodic x-ray intensity distribution projected when said object is absent onto slab-volume SV3 with period aPy is carefully aligned with the phase of said detector-pixel array.
- and
wherein said structure is oriented within the apparatus so that the periodicity-direction associated with spatial period a3x lies in the direction x; and wherein a is accurately related to aPx by a3x =v aPx ; and wherein the spatial phase of said spatially periodic x-ray intensity distribution projected when said object is absent onto slab-volume SV3 with period aPx is carefully aligned with the phase of said spatially-periodic structure within slab-volume SV3; and wherein a3y is a distance measured in direction y.
- and
wherein the spatial profile of the intensity distribution of x-rays projected onto slab-volume SV3 is masked by said structure within slab-volume SV3; and
wherein said x-ray image-detector measures said masked profile.
- and
wherein said x-ray image detector images the spatial profile of the distribution of light emission by said fluor material.
- and
wherein, when said object is absent, and for x-rays with at least one specific energy value that lies within said energy-bandwidth, and throughout the associated useful x-direction width of said material structure within slab-volume SV3, then the two structures respectively within slab-volumes SV1 and SV2 acting together but not separately project onto slab-volume SV3 an x-ray intensity distribution that is substantially spatially-periodic in direction y with the spatial period aPy ; and wherein a3y is accurately related to aPy by a3y =v aPy ; and wherein the spatial phase of said spatially periodic x-ray intensity distribution projected when said object is absent onto slab-volume SV3 with period aPy is carefully aligned with the phase of said detector-pixel array.
- and
wherein each image-pixel has an associated gray-scale for any produced image; and wherein the quantity w is a positive integer; and wherein aRx is accurately related to a3x by aRx =w a3x ; and wherein aRy is accurately related to a3y by aRy =w a3y ; and wherein each image-pixel is associated with an aRx -by-aRy area on a slab face of slab-volume SV3; and wherein each image-pixel has dimensions scaled similarly in directions x and y, and has a width and height that are scaled similarly from the associated distances aRx and aRy ; and wherein each image-pixel-associated aRx -by-aRy area on said slab face of slab-volume SV3 is subdivided into a multiplicity of labeled component areas that includes at least one associated b-labeled area and that includes at least one associated d-labeled area, and also may include other labeled component areas; and wherein said specific names for said labels are inconsequential, as long as they are applied consistently to produce the same apparatus; and wherein said other component areas may include one associated c-labeled area, and also may include additional associated b-labeled, c-labeled, and d-labeled areas; and wherein the b-labels, c-labels, and d-labels within any two aRx -by-aRy areas on said slab face of slab-volume SV3 are configured to have the same geometric arrangement of said component area labels as each other when the centroids of the two aRx -by-aRy areas are spaced from each other in the direction x by a distance that is an integral multiple of a3x ; and wherein said x-ray image detector is segmented into detector-pixels; and wherein said x-ray image detector measures simultaneously and independently the intensity of x-rays incident on each detector-pixel; and wherein said x-ray image detector is segmented and positioned so that simultaneously and independently some of its various detector-pixels measure the intensities of x-rays incident only on associated b-labeled areas and some of its various detector-pixels measure the intensities of x-rays incident only on associated d-labeled areas; and wherein each of said gray-scales is computed as a function of the measured intensity of x-rays incident on at least one associated b-labeled area and of the measured intensity of x-rays incident on at least one associated d-labeled area; and wherein said gray-scale computation function also may depend on measured intensities of x-rays incident on additional associated b-labeled areas and also may depend on measured intensities incident on additional associated d-labeled areas; and wherein said apparatus further includes means for performing said computation.
- and
wherein at least one weight factor in said linear combination is negative.
-
wherein said two different images display different physical properties of said object; and wherein said x-ray image detector is segmented and positioned so that simultaneously and independently some of its various detector-pixels measure the intensities of x-rays incident only on b-labeled areas and some of its various detector-pixels measure the intensities of x-rays incident only on c-labeled areas and some of its various detector-pixels measure the intensities of x-rays incident only on d-labeled areas; and wherein each gray-scale for each image-pixel for the first of said two different images is computed as a function of the measured intensity of x-rays incident on at least one associated b-labeled area, and of the measured intensity of x-rays incident on at least one associated c-labeled area, and of of the measured intensity of x-rays incident on at least one associated d-labeled area; and wherein each gray-scale for each image-pixel for the second of said two different images is computed as a function of the measured intensity of x-rays incident on at least one associated b-labeled area, and of the measured intensity of x-rays incident on at least one associated c-labeled area, and of the measured intensity of x-rays incident on at least one associated d-labeled area; and wherein the function used for the first of said two different images is different from the function used for the second of said two images.
-
wherein said refractive-index-gradient structure of said object induces a significant change to the intensity distribution of x-rays projected onto slab-volume SV3, relative to said distribution projected when said object is absent; and wherein the distance a3x has a sufficiently small value that the interaction of x-rays with said spatially-periodic structure within slab-volume SV3 provides, at least in part, means for detecting said significant change.
- wherein said means for adjusting the relative alignment of the spatially-periodic material structures within slab-volumes SV1, SV2, and SV3 comprises
means for moving at least two of the three structures within slab-volumes SV1, SV2, and SV3, a laser that emits light, a telescope, a mirror, and an optical image detector; wherein said telescope focuses said laser-emitted light; and wherein the focusing of said telescope is adjustable; and wherein said mirror transmits x-rays; and wherein said mirror reflects at least some of said laser-emitted light; and wherein said optical image detector detects and thereby measures the spatial profile of the intensity distribution of laser-emitted telescope-focused light that is incident upon it; and wherein said x-ray image detector may serve as said optical image detector; and wherein said mirror, said laser, and said telescope are positioned so that with appropriate focusing of said telescope said laser-emitted telescope-focused light propagates in the sequential order, first through said structure within slab-volume SV1, next through said structure within slab-volume SV2, next into slab-volume SV3, and then is detected; and wherein said spatially-periodic structures within slab-volumes SV1, SV2, and SV3 are each made from a material that also interacts with said laser-emitted telescope-focused light; and wherein with appropriate focusing of said telescope said propagation of laser-emitted telescope-focused light through said spatially-periodic material structure within slab-volume SV1 generates by diffraction Fraunhofer diffraction orders; and wherein laser-emitted telescope-focused light propagating in at least two of said Fraunhofer diffraction orders that are generated by diffraction of laser-emitted telescope-focused light by material within slab-volume SV1 is incident on said structure within slab-volume SV2; and wherein the propagation of the laser-emitted telescope-focused light in each of said at least two Fraunhofer diffraction orders through said spatially-periodic material structure within slab-volume SV2 generates by diffraction more Fraunhofer diffraction orders; and wherein laser-emitted telescope-focused light propagating in one of said Fraunhofer diffraction orders that is generated by diffraction of laser-emitted telescope-focused light by said structure within slab-volume SV2 is incident on a first incidence area on said structure within slab-volume SV3; and wherein laser-emitted telescope-focused light propagating in a second one of said Fraunhofer diffraction orders that is generated by diffraction of laser-emitted telescope-focused light by said structure within slab-volume SV2 is incident on a second incidence area on said structure within slab-volume SV3; and wherein said first and second incidence areas overlap; and wherein by said overlap said laser-emitted telescope-focused light incident within said overlap-area forms a spatially-periodic optical interference pattern on said structure within slab-volume SV3; and wherein said spatial periodicities of said optical interference pattern and of said spatially-periodic material structure within slab-volume SV3 together create a spatially-periodic moire pattern, if and when their two associated spatial periods are incommensurate; and wherein said moire pattern is imaged by said optical image detector; and wherein observations of said moire pattern can be used to guide said relative alignment adjustments.
- and
wherein said first, second, and third incidence areas all overlap on a common three-way overlap-area; and wherein by said overlap said laser-emitted telescope-focused light incident within said common three-way overlap-area forms said spatially-periodic optical interference pattern on slab-volume SV3.
-
wherein said plurality of small x-ray image detectors can acquire simultaneously a plurality of small images; and wherein said apparatus is further comprised of means for combining said plurality of small images to form said image that describes the internal structure of said object.
-
wherein said replication provides a plurality of x-ray image detectors; and wherein said replication excludes replication of said object; and wherein said replication excludes replication of said x-ray source; and wherein said replication includes, as needed, said contents of slab-volumes SV1, SV2, and SV3; and wherein said replication of an apparatus component is performed in such a manner that may result simply in the spatial extension of said apparatus component; and wherein said x-ray source provides a common source of x-ray illumination for said replicated apparatus components; and wherein each of said sets of replicated components acquires a small image that is descriptive of a portion of the internal structure of said object; and wherein said sets of replicated components can acquire a plurality of small images simultaneously with each other; and wherein said apparatus is further comprised of means for combining said plurality of small images to form said image that describes the internal structure of said object.
-
9. Apparatus of 8 wherein said source emits x-rays dominantly from a spatially small but finite-size spatial region S, and
wherein WS is the approximate x-direction width of said finite-size spatial region S within which said dominant emission of x-rays occurs, and wherein the distance a1x is substantially smaller than the distance WS.
-
60. Apparatus for producing an image that describes the internal structure of an object, comprising
a source of x-rays, an x-ray image detector; -
improved by its further comprising three very-thin slab-shaped volumes, SV1, SV2, and SV3, each with substantially-planar slab faces oriented relative to each other to be substantially-mutually-parallel, and each containing an associated very-thin material structure that interacts with x-rays, and means for limiting the energy-bandwidth of detected x-rays; wherein said three contained structures are positioned between said source and said detector so that x-rays from said source propagate in the sequential, order first through said structure within slab-volume SV1, next through said structure within slab-volume SV2, next through said object, next into slab-volume SV3, and then are detected; and wherein, when said object is absent, and for x-rays with at least one specific energy value that lies within said energy-bandwidth, and throughout the associated useful x-direction width of said material structure within slab-volume SV3, then the two structures respectively within slab-volumes SV1 and SV2 acting together but not separately project onto slab-volume SV3 an x-ray intensity distribution that is substantially spatially-periodic and has a substantial spatial intensity variation; and wherein, when said object is absent, and for said x-rays with said specific energy value that lies within said energy-bandwidth, then each of the two structures respectively within slab-volumes SV1 and SV2, acting alone with the other absent, projects onto slab-volume SV3 an x-ray intensity distribution that is different from said spatial distribution projected by said two structures acting together; and wherein any associated residual spatial periodicity of either of said two distributions projected by said two structures acting alone has a diminished spatial intensity variation relative to said spatial distribution projected by said two structures acting together, and/or has a dominant spatial period that is different from that projected by said two structures acting together.
-
-
61. Method for producing an image that describes the internal structure of an object, comprising
providing a source of x-rays, and providing an x-ray image detector; -
wherein said method is improved by its further comprising providing three very-thin slab-shaped volumes, SV1, SV2, and SV3, each with substantially-planar slab faces oriented relative to each other to be substantially-mutually-parallel, and with each slab-volume containing an associated very-thin material structure that interacts with x-rays; and positioning said three contained structures between said source and said detector; and propagating x-rays from said source in the sequential order, first through said structure within slab-volume SV1, next through said structure within slab-volume SV2, next through said object, next into slab-volume SV3, and then detecting the x-rays; and limiting the energy-bandwidth of the energy spectrum of x-rays that are detected; and configuring and further positioning the two spatially-periodic structures respectively within slab-volumes SV1 and SV2 so that when said object is absent, and for x-rays with at least one specific energy value that lies within said energy-bandwidth, and throughout the associated useful x-direction width of said material structure within slab-volume SV3, then the two structures respectively within slab-volumes SV1 and SV2 acting together but not separately project onto slab-volume SV3 an x-ray intensity distribution that is substantially spatially-periodic, and so that when said object is absent, and for said x-rays with said specific energy value that lies within said energy-bandwidth, then each of the two structures respectively within slab-volumes SV1 and SV2, acting alone with the other absent, projects onto slab-volume SV3 an x-ray intensity distribution that is different from said spatial distribution projected by said two structures acting together, and so that any associated residual spatial periodicity of either of said two distributions projected by said two structures acting alone has a diminished spatial intensity variation relative to said spatial distribution projected by said two structures acting together, and/or has a dominant spatial period that is different from that projected by said two structures acting together. - View Dependent Claims (62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100)
-
Specification