US4769756A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Systematic method for matching existing radiographic projections with radiographs to be produced from a specified region of interest in cancellous bone
Assignee: United States Department of Health and Human Services
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Filing: 1986-08-07
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Granted: 1988-09-06
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Expires: 2006-08-07
Abstract
Abstract A method to synthesize arbitrary projection images from a basis set of projections bearing a known geometric relationship to each other. In order to determine retrospectively the projection angle of a radiograph of interest with repect to the set of basis projections, similarity measures based on the gray-level standard deviations in corresponding images are used. An iterative coordinate estimation procedure is implemented incorporating these methods with radiographs obtained from dry skull specimens.
Inventors
- 👤 Richard L. Webber
- 👤 Urs E. Ruttimann
- 👤 Paul F. Van Der Stelt
- 👤 Paul Edholm
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 11:26
CPC Classifications
G; G06; G06T; G06T12/00; G06T12/10; G06T2211/00; G06T2211/40; G06T2211/436
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
143 words
A method of reconstructing a projection of an object produced from an unknown position in space from a series of projections bearing a known geometric relationship to each other comprising the steps of making a set of basis projections characterized by gray-level distributions, said basis projections bearing known geometric relationship with each other such that the positions of the sources used to produce the basis projections circumscribe the position of the source from which the unknown projection was made; comparing each known basis projection with the projection to be reconstructed using an appropriate measure of image similarity; establishing respective estimates of the angles characterizing the unknown projection relative to each of the known basis projection angles; using these estimates of unknown projection angles, to weight and geometrically shift the known basis projections and average them to synthesize an approximation of the desired projection.
Claim 2
Independent Claim
143 words
A method of reconstructing a projection of an object produced from an unknown position in space from a series of projections bearing a known geometric relationship to each other comprising the steps of making a set of basis projections characterized by gray-level distributions, said basis projections bearing known geometric relationship with each other such that the positions of the sources used to produce the basis projections circumscribe the position of the source from which the unknown projection was made; comparing each known basis projection with the projection to be reconstructed using an appropriate measure of image similarity; establishing respective estimates of the angles characterizing the unknown projection relative to each of the known basis projection angles; using these estimates of unknown projection angles, to weight and geometrically shift the known basis projections and average them to synthesize an approximation of the desired projection.
Claim 3
Dependent Claim
37 words
The method of claim 1 further comprising the steps of using an iteration scheme to achieve successively better estimates of the relative projection angles of the unknown projection relative to each of the known basis projection angles.
Claim 4
Dependent Claim
40 words
The method of claim 1 further characterized by the sources of the said basis projections being distributed on the circumference of the base of a right circular cone with its apex in the object from which the projections are created.
Claim 5
Dependent Claim
72 words
The method of claim 1 further characterized by using parameters derived from an analysis of the statistics underlying the gray-level distributions produced from the basis projections when compared with the unknown projection to determine the relative projection angles defined by lines connecting said sources associated with the basis set and the center of the object, and the line connecting the source associated with the unknown projection and the center of the object.
Claim 6
Dependent Claim
27 words
The method of claim 4 further characterized by said statistics including anisotropic measures of angular disparity to produce image similarity measures having different values in different directions.
Claim 7
Dependent Claim
30 words
The method of claim 4 further characterized by establishing a functional relationship between said similarity measure and the angular relationship between the known projection angles underlying the basis projection set.
Claim 8
Dependent Claim
32 words
The method of claim 6 further characterized by using said functional relationship to estimate the said positions in space of the source used to produce the unknown projection in an iterative manner.
Claim 9
Dependent Claim
29 words
The method of claim 1 further characterized by using the principle of back projection to reconstruct a three-dimensional representation of the object to facilitate synthesis of said desired projection.
Claim 10
Dependent Claim
59 words
The method of claim 8 further characterized by using circular tomosynthetic methods and spatial-frequency filtering techniques to produce a three dimensional representation of the object through a plurality of individual slices which are stacked in a skewed manner and averaged in a direction orthogonal to the plane of the said slices to yield an approximation to the unknown projection.
Claim 11
Dependent Claim
35 words
The method of claim 9 further characterized by using selective weighting of individual basis projections consistent with the proximity of the associated source positions relative to that of the unknown projection prior to tomosynthetic reconstruction.
Claim 12
Dependent Claim
32 words
The method of claim 10 further characterized by using selected weights inversely proportional to the distance of said source positions of the basis set from the source position of the unknown projection.
Claim 13
Independent Claim
131 words
A method of selecting a single projection from a first series of projections bearing a known geometric relationship to each other which lies within a predetermined minimum distance from another single projection from an independent second series of projections bearing the same geometric relationship to each other comprising the steps of positioning the sources of said projections on the circumference of the base of a right circular cone with its apex in the object from which the projections are created; equally distributing the source positions on the circumference of the base of said cone such that the distance between adjacent source positions is not more than twice the said predetermined minimum distance; constraining the said circular distributions to overlap; and selecting the two projections from both distributions that are closest together.
Claim 14
Independent Claim
131 words
A method of selecting a single projection from a first series of projections bearing a known geometric relationship to each other which lies within a predetermined minimum distance from another single projection from an independent second series of projections bearing the same geometric relationship to each other comprising the steps of positioning the sources of said projections on the circumference of the base of a right circular cone with its apex in the object from which the projections are created; equally distributing the source positions on the circumference of the base of said cone such that the distance between adjacent source positions is not more than twice the said predetermined minimum distance; constraining the said circular distributions to overlap; and selecting the two projections from both distributions that are closest together.
Claim 15
Dependent Claim
19 words
The method of claim 12 further characterized by using gray level distributions in the projections to measure image similarity.
Claim 16
Dependent Claim
26 words
The method of claim 12 further characterized by shifting one projection with respect to the other until image similarity is maximized and recording absolute shift distance.
Claim 17
Dependent Claim
16 words
The method of claim 14 further characterized by choosing an arbitrary projection from said first series.
Claim 18
Dependent Claim
27 words
The method of claim 15 further characterized by using image similarity to select a projection from said second series nearest the selected projection from said first series.
Claim 19
Dependent Claim
47 words
The method of claim 16 further characterized by using image similarity to select a projection from said first series nearest the projection selected from said second series in said previous step of selecting a projection from said second series nearest the selected projection from said first series.
Claim 20
Dependent Claim
33 words
The method of claim 17 further characterized by iterating said steps of selecting a projection from said second and said first series until the selections of the projections converge to a repeating pattern.
References Cited (Backward Citations)
US4247780A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-09-06 | 1992-03-07 | 1992-09-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-09-06 | 1996-03-07 | 1996-09-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-09-06 | 2000-03-07 | 2000-09-06 | $7700.00 | Window Closed / Lapsed |