Image analysis – Image enhancement or restoration – Edge or contour enhancement
Reexamination Certificate
1998-07-10
2001-01-16
Lee, Thomas D. (Department: 2724)
Image analysis
Image enhancement or restoration
Edge or contour enhancement
C382S132000, C382S140000, C382S160000
Reexamination Certificate
active
06175658
ABSTRACT:
TECHNICAL FIELD
The present invention relates to digital imaging techniques and, more particularly, to techniques for enhancement of discrete pixel images, such as those produced in medical imaging systems.
BACKGROUND ART
A wide range of systems have been proposed and are currently in use for producing discrete pixel images. In such systems, data is gathered representative of characteristics of a large number of picture elements or pixels arranged in an array or matrix. For example, in digital radiography systems, signals are produced which are representative of a level or intensity of radiation received within each pixel region during an exposure. The signals are processed and filtered to provide consistent and meaningful information over the matrix of pixels. Following such processing, the data is used to reconstruct a useful composite image made up of the pixels. The particular filtering and processing of the signals may be adapted to various modalities and features of interest, so as to provide a user with meaningful information in their reconstructed image. In many medical applications, an attending physician or radiologist will consult the composite image for identification of internal features within a subject as defined by edges, textural regions, contrasted regions, and so forth.
Algorithms have been developed for digitally processing discrete pixel image data to enhance diagnostic portions of the image while suppressing noise. For example, in one known method pixel data is filtered through progressive low pass filtering steps. The original image data is thus decomposed into a sequence of images having known frequency bands. Gain values are applied to the resulting decomposed images for enhancement of image features, such as edges. Additional filtering, contrast equalization, and gradation steps may be employed for further enhancement of the image.
While such techniques provide useful mechanisms for certain types of image enhancement, they are not without drawbacks. For example, gains applied to decomposed images can result in inadvertent enhancement of noise present in the discrete pixel data. Such noise, when enhanced, renders the reconstructed image difficult to interpret, and may produce visual artifacts which reduce the utility of the reconstructed image, such as by rendering features of interest difficult to discern or to distinguish from non-relevant information.
There is a need, therefore, for an improved technique for discrete pixel image enhancement. In particular, there is a need for a technique which is capable of enhancing features of interest in such images, such as edges of structures, without enhancement of noise or other artifacts. There is also a particular need for an image enhancement technique which can be employed in existing systems, and which can be adjusted by users for various situations, depending upon the type of subject being imaged, the features of interest, and so forth.
DISCLOSURE OF THE INVENTION
The present invention provides a technique for enhancing digital pixel images designed to respond to these needs. The technique affords enhancement of particular features in the image as defined by the digital pixel data, while avoiding enhancement of noise and other artifacts. The technique applies feature enhancement gain factors which are based upon the level of an enhanced image in a decomposition pyramid. Gains employed for different levels in the decomposed images can be adjusted, with lower gains being employed for decomposed images at lower spatial frequency levels. The technique may be applied to images acquired through a range of imaging modalities. The technique is particularly well suited to enhancement of images acquired through digital X-ray systems.
In accordance with certain aspects of the technique, processed acquired pixel data for an image is filtered to decompose the image into a series of spatial frequency level images. The series of images includes images at progressively lower spatial frequency levels. A gain image for at least one of the spatial frequency images is derived from image data from a lower spatial frequency level. This gain is applied to the higher spatial frequency image to obtain an enhanced image for that spatial frequency level. Such gains may be derived for and applied to a series of the decomposed spatial frequency level images. Such spatial frequency-based gain images may be employed for spatial frequency level images at which valuable information, such as edge information, is expected to be found. Other lower spatial frequency level images may be processed by applying gains equal to unity or gains higher than or less than unity. The resulting images are then recombined to arrive at an enhanced image. The decomposition, enhancement, and reconstruction phases of the technique preferably produce an enhanced image of equal dimensions to the input image.
REFERENCES:
patent: 5461655 (1995-10-01), Vuylsteke et al.
patent: 5467404 (1995-11-01), Vuylsteke et al.
patent: 5546473 (1996-08-01), Buytaert et al.
patent: 5644662 (1997-07-01), Vuylsteke
patent: 5739922 (1998-04-01), Matama
patent: 6018596 (2000-01-01), Wilkinson
patent: 0 368 162 A2 (1989-11-01), None
patent: 0 444 874 A3 (1991-02-01), None
patent: 0 527 525 A2 (1992-07-01), None
patent: WO 98/55916 (1998-12-01), None
Aufrichtig Richard
Kump Kenneth S.
Cabou Christian G.
Fletcher Yoder
General Electric Company
Lee Thomas D.
Price Phyllis Y.
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