X-ray or gamma ray systems or devices – Beam control – Antiscatter grid
Reexamination Certificate
1999-10-12
2001-10-16
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Beam control
Antiscatter grid
Reexamination Certificate
active
06304632
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to improvement of the quality of a radiographic image of an object obtained by a radiographic X-ray unit containing an anti-diffusion or anti-scatter grid.
The invention applies advantageously but not exclusively to mammography examinations for the detection of micro-calcifications inside a breast.
A radiographic X-ray unit, used in particular in mammography, is equipped with an anti-diffusion grid arranged between the object to be radiographed, in this case a breast, and a receiver of radiographic images, for example a CCD (charge-coupled) receiver. In conventional fashion, the anti-diffusion grid is composed of a series of plates that are all directed toward the focal point of X-ray radiation emitted in the direction of the object and of the image receiver. Thus, the anti-diffusion grid allows the undiffused direct beams to pass, while the diffused beams are absorbed by the plates.
This being so, the resolution of the image receiver is generally finer than the space between two plates, which typically is of the order of 0.3 mm. The result of this is that the plates are visualized on the radiographic image obtained, which is particularly troubling in mammography because it makes detection of micro-calcifications more difficult.
One solution of this problem consists of displacing the grid during exposure, in rectilinear translation in its plane, i.e., substantially perpendicular to the plates of the anti-diffusion grid. Such translation may be effected only in one direction or, in alternating fashion, in both directions.
The quality of the image is thus improved but nevertheless remains inadequate. In addition, generation of an alternating movement is a mechanically more complicated solution.
BRIEF DESCRIPTION OF THE INVENTION
An embodiment of the invention eliminates, insofar as possible, the visible traces of the plates of the anti-diffusion grid on the radiographic film.
An embodiment of the invention obtains an improvement in the quality of the images by a mechanically simple solution for displacement of the anti-diffusion grid.
An embodiment of the invention makes it possible to obtain improved quality images by a particular displacement profile of a anti-diffusion grid.
More precisely, the invention is a method of improvement of the quality of a radiographic image of an object obtained by an X-ray unit containing an anti-diffusion grid, arranged between the object and a receiver of radiographic images, which grid is displaced in rectilinear translation in its plane, at the time that the image is taken, between a starting position and an ending position and according to a predetermined temporal law of displacement.
REFERENCES:
patent: 4803716 (1989-02-01), Ammann et al.
patent: 5357554 (1994-10-01), Schneiderman et al.
Baudry Jean-Luc
Muller Serge
Rick Andreas
Chaskin Jay L.
Church Craig E.
GE Medical Systems S.A.
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