X-ray or gamma ray systems or devices – Specific application – Tomography
Reexamination Certificate
2000-12-01
2002-11-19
Porta, David P. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Tomography
C378S010000, C378S098120, C378S137000
Reexamination Certificate
active
06483890
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the diagnostic imaging arts. It finds particular application in conjunction with digital x-ray imaging and will be described with particular reference thereto. However, it is to be appreciated that the present invention also has application in conjunction with computed tomography (CT) scanning and nuclear cameras and is not limited to the aforementioned application.
The most prominent difference between digital x-ray scanning and classical plane film x-ray is the x-ray detection system. An array of digital detectors replaces the sheet of photosensitive film. Each individual detector within the array detects the intensity of the radiation incident upon its face during the scan and converts that information into an electrical signal. The combined signals are processed and ordered by a computer and converted into a visible display.
Each individual detector reports only one intensity value, the average intensity along a path with about the same cross-section as the individual detector. However, the data is typically treated as if intensity variations are due solely to the x-ray from the source to the center of the detector. In this manner, the detectors can be thought of as individual pixels of a larger image. The smaller the pixels are, the finer the resolution and the more precise the resulting image. Conversely, if the individual detectors are too small, only a small amount of radiation strikes each detector during a sampling interval. Low amounts of received radiation are sensitive to statistical fluctuation and sampling errors.
In a more complex solution, the paths of the central rays are shifted half a pixel and the detectors sampled again. In this manner, the effective number of pixels is doubled. However, mechanically shifting the detector array rapidly and precisely is difficult. Often, vibration occurs providing uncertainty and inaccuracy in the true path of the central rays, which blurs the resultant image.
U.S. Pat. No. 4,637,040 to Sohval and Freundlich alternates between the two x-ray sources. The patent also suggests physically shifting a single x-ray rouse during rotation of a CT scanner, such as with a pair of x-ray tubes or a single tube with two distinct focal spots.
The present invention contemplates a new method and apparatus for increasing the spatial resolution in two dimensions of a digital x-ray system that overcomes the above-referenced problems and others.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a diagnostic imaging apparatus emits a beam of radiation into an imaging region where it penetrates a subject and is detected on the other side by an array of detectors, and processed into a visual representation of the interior of the subject.
In accordance with another aspect of the present invention, the imaging apparatus emits multiple beams of radiation, each time from a different source point, and combines the detected information into a higher resolution representation of the interior of the subject.
According to a more limited aspect of the present invention, the imaging apparatus uses an x-ray that generates electrons with a cathode and accelerates them towards an anode where they are converted into x-rays, steering the electrons along the way with a plurality of deflectors.
According to a more limited aspect of the present invention, the electrons are moved continuously or incrementally around a closed path on the anode.
According to another aspect of the present invention, a method is provided wherein the resolution of a digital x-ray apparatus is improved by using a plurality of point sources of x-rays, detecting the x-rays after passage through a subject, and combining multiple images into one, higher resolution image.
One advantage of the present invention is that it increases the spatial resolution of a digital x-ray scanning system.
Another advantage of the present invention is that it requires no moving parts to be added to the system.
Another advantage of the present invention is that it increases digital sampling density.
Yet another advantage of the present invention is that it is cost-effective.
Still further benefits and advantages of the present invention will become apparent to those skilled in the art upon a reading and understanding of the preferred embodiments.
REFERENCES:
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patent: 6222902 (2001-04-01), Lin et al.
patent: 6324249 (2001-11-01), Fazzio
Fay Sharpe Fagan Minnich & McKee LLP
Ho Allen C
Koninklijke Philips Electronics , N.V.
Porta David P.
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