Real-time digital X-ray subtraction imaging
Patent 4204225 Issued on May 20, 1980. Estimated Expiration Date: 
November 15, 1998. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
November 15, 1998. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3668396 3854049 3894181 Differential X-ray method and apparatus Video display arrangements Patent #: 4125858 InventorAssigneeApplicationNo. 05/960830 filed on 11/15/1978US Classes:378/98.12, With image subtraction or addition378/98.2, Televison600/508HeartExaminersPrimary: Griffin, Robert L.Assistant: Coles, Edward L. Attorney, Agent or FirmInternational ClassesA61B 6/00 (20060101)H04N 5/32 (20060101) H05G 1/64 (20060101) H05G 1/00 (20060101) AbstractDifference images, derived from an X-ray image of an anatomical subject, are produced in real time by directing X-rays through the anatomical subject to produce an X-ray image, converting the X-ray image into television fields comprising trains of analog video signals, converting the analog video signals into digital video signals, producing integrated mask digital video signals by integrating the digital video signals over a mask time interval, subtracting the integrated mask digital video signals from corresponding digital video signals of television fields subsequent to the mask time interval and thereby producing digital difference video signals, converting the digital difference video signals into analog difference video signals, and converting the analog difference video signals into a series of visible television difference images representing changes in the X-ray image subsequent to the mask time interval. The mask time interval preferably corresponds generally to at least one complete cardiac cycle of the anatomical subject. An X-ray contrast medium is preferably injected into a peripheral blood vessel of the anatomical subject, with a timing such that the contrast medium appears in the X-ray image subsequent to the mask time interval. In another embodiment, the integrated mask digital video signals are reconverted to analog form and are subtracted on an analog basis from the analog video signals produced subsequent to the mask time interval, to produce the analog difference video signals.Other References
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