US 5,812,629 AGranted

Ultrahigh resolution interferometric x-ray imaging

OwnerJohn F. Clauserinventor

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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.apprxeq.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.

Claims100

Dependent claims

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 a.sub.1x and a.sub.2x, 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 R.sub.1 and the perpendicular distance between slab-volume SV2 and slab-volume SV3 is R.sub.2 ;
and
wherein b, q, and p are positive integers;
and
wherein a.sub.1x is accurately related to a.sub.2x by
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 a.sub.Px and has a substantial spatial intensity variation;
and
wherein when the greatest common integer divisor of b and q is 1, then the period a.sub.Px is accurately related to a.sub.2x by
a.sub.Px =a.sub.2x (R.sub.1 +R.sub.2)(q p R.sub.1).sup.-1.

19 more elements

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.

9 more elements

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.

12 more elements

Dependencies are inferred from the claim text.