Method and apparatus for calibration and correction of gray levels in images

a gray level and image technology, applied in the field of methods and apparatus for calibrating and correcting gray levels in images, can solve the problems of not always available or accessible devices, the inability to and the inability to accurately correct the variation in gray level in successive images. , to achieve the effect of eliminating the utilization of black measurement devices

US20050031180A1Inactive Publication Date: 2005-02-10GE MEDICAL SYST GLOBAL TECH CO LLC
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Patent Information

Authority / Receiving Office
US · United States
Patent Type
Applications(United States)
Current Assignee / Owner
Publication Date
2005-02-10
Estimated Expiration
Not applicable · inactive patent

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Abstract

A method and apparatus for calibrating an apparatus that acquires a sequence of radiographic images and correcting images of an object under observation. For each image of a sequence acquired by the apparatus and for a given frequency of acquisition of the sequence, the apparatus is calibrated by determining the value of the variation of a mean of gray levels in at least one zone of interest of the current image of at least one calibration device, the variation being determined relative to the mean gray level of the first image of the sequence in each zone of interest. The determination of the variation is reiterated for a series of images sequences acquired using calibration devices resulting in first images of mean gray levels different from one sequence to another. Each image of an image sequence of the object under observation is corrected, comprising zones of observation having different gray levels by subtracting from the current image the variation of one gray level relative to the first image of the object, the subtraction being a function of the gray level considered from each zone of observation.
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Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of a priority under 35 USC 119(a)-(d) to French Patent Application No. 03 01797 filed Feb. 14, 2003, the entire contents of which are hereby incorporated by reference. BACKGROUND OF THE INVENTION The present invention relates to a method apparatus for calibrating and correction of gray levels in images. In particular, the present invention is directed to acquiring a sequence of radiographic images and correction images of an object under observation. More particularly, the present invention relates to a method and apparatus for an acquiring sequence of radiographic images and calibration and correction of images of an object under observation by subtracting from each image of the sequence the spurious variation of a gray level between the images of the same sequence. The present invention can be particularly used in the medical field, such as, for example, in mammography and in the detection of cancerous t...

Examples

Embodiment Construction

An example of a known radiographic apparatus is represented schematically in FIG. 1. In Figure, an apparatus 1 comprises a console 5 (having a substantially vertical extension) and means for providing a radiographic beam emitter 4 facing in the direction of a plate 7 comprising means for detection 2. The means for detection 2 may comprise a photodiode matrix. The means for detection 2 collects the radiation, for example, X-rays, after passing through an object under observation placed in the observation space 6 arranged in the beam 4, between on the one hand the emitter 3 and on the other hand the detector 2 of the apparatus 1. The extensions of the emitter 3 and the detector 2 can be, for example, horizontal and perpendicular to the console 5 but any observation direction is possible, especially due to the fact of the possible rotation of the assembly formed by the emitter 3 and the detector 2 about a substantially horizontal axis of extension. The apparatus 1 may also comprise me...