US4720843A
Expired / Lapsed
US
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Method for separating moving structures from a fixed background in a sequence of X-ray projection images and equipment for implementing this method
Assignee: US Philips Corp
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Filing: 1986-04-17
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Granted: 1988-01-19
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Expires: 2006-04-17
Abstract
Abstract The invention relates to an X-ray subtraction method, and equipment for implementing this method, in which a moving structure is subtracted from the fixed background. The picture values corresponding to the minimum absorption are used as the mask image for each picture element from the projection images.
Inventors
- 👤 Paul R. Haaker
- 👤 Erhard P. A. Klotz
- 👤 Reiner H. Koppe
- 👤 Rolf E. Linde
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 08:33
CPC Classifications
G; G06; G06T; G06T5/00; G06T5/50
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
93 words
A method for X-ray examination comprising the steps of: obtaining a sequence of X-ray projection images of an area of a patient which depict moving structures against a fixed background; deriving a mask image from said sequence of images by comparing a group of images in said sequence, on a picture element-by-picture element basis, and choosing for each picture element in the mask image a corresponding picture element value from the plurality of images which represents a minimum absorption value; and subtracting the mask image from one or more images in said sequence.
Claim 2
Independent Claim
93 words
A method for X-ray examination comprising the steps of: obtaining a sequence of X-ray projection images of an area of a patient which depict moving structures against a fixed background; deriving a mask image from said sequence of images by comparing a group of images in said sequence, on a picture element-by-picture element basis, and choosing for each picture element in the mask image a corresponding picture element value from the plurality of images which represents a minimum absorption value; and subtracting the mask image from one or more images in said sequence.
Claim 3
Dependent Claim
63 words
A method as claimed in claim 1 for angiographic examination of coronary vessels further comprising disposing a contrast medium into a coronary vessel of said patient, where said area contains said coronary vessel, and wherein the step of obtaining a sequence of X-ray projection images comprising obtaining the images during a rapid cardiac phase under the control of EKG signals from said patient.
Claim 4
Dependent Claim
54 words
A method as claimed in claim 1 for angiographic examination of coronary vessels further comprising disposing a contrast medium into a coronary vessel of said patient, where said area contains said coronary vessel, and wherein the step of deriving the mask image is repeated several times using different groups of images in the sequence.
Claim 5
Independent Claim
37 words
A method as claimed in ay of claims 1, 2, wherein a mask image derived from projection images obtained during a first cardiac cycle is subtracted from projection images obtained during subsequent cardiac cycles of said patient.
Claim 6
Independent Claim
45 words
A method as claimed in any of claims 1, 2 or 3 wherein the mask image is derived from projection images in a single cardiac cycle of said patient and is subsequently subtracted from stored projection images which were obtained during the same cardiac cycle.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-01-18 | 1991-07-20 | 1992-01-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-01-18 | 1995-07-20 | 1996-01-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-01-18 | 1999-07-20 | 2000-01-19 | $7700.00 | Window Closed / Lapsed |