Image analysis – Image enhancement or restoration
Reexamination Certificate
1998-04-08
2001-03-27
Rogers, Scott (Department: 2724)
Image analysis
Image enhancement or restoration
C382S305000, C382S307000
Reexamination Certificate
active
06208762
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains in general to digital image processing and in particular to a method and system for enhancing digital X-ray images.
2. Description of Background Art
Modern X-ray systems digitally capture X-ray images with a solid state sensor plate. The images are typically high resolution, e.g. 2688×2688 pixels, and have thousands of levels of gray scale. The images are usually previewed on a monitor associated with the X-ray system and then stored in an image archive for later retrieval and analysis with a more sophisticated viewing system.
The monitor provides a user with a real-time view of the X-ray image received by the sensor plate. A general preference among radiologists is to have a patient's spine aligned with the vertical axis of the image. In emergency room situations, however, the X-rays must be taken immediately and under desperate circumstances. Accordingly, X-rays are often misaligned with respect to the preferred axis. The real-time view in the monitor can be used by the X-ray system operator to correct this misalignment.
When the X-rays are later retrieved with the more sophisticated viewing system, the doctor or other viewer can re-align or otherwise enhance the image by performing one or more digital image manipulations. These manipulations include, for example, rotating, scaling, thresholding, and filtering. Some of the manipulations are lossless, meaning that all information in the original image is retained after manipulation, while others are lossy, meaning that information about the original image is lost during manipulation.
When a manipulation is performed on an image, the most recent, modified, version of the image is stored in the archive for later retrieval. If multiple lossy digital manipulations are performed on the image, the amount of information lost may become substantial. For example, the digital rotation manipulation is generally lossy and the amount of information lost with each rotation is not dependent on the magnitude of the rotation displacement. In use, a first radiologist in the emergency room may make a hasty rotation of an image. Then, at a later date, a second radiologist may desire a more precise alignment and introduce a second, very small, image rotation. Even though the second rotation involves a small angle, the amount of additional information loss is generally the same as for the first, larger, rotation.
Since each enhanced image becomes the latest enhanced image and displaces the previous enhanced image in the cache, the image stored in the cache progressively deteriorates with each lossy digital manipulation. Since the cached image is the only copy of the image, the information lost through lossy digital manipulation cannot be recovered.
Accordingly, there is a need for an image manipulation and enhancement system that optimizes the order, kind, and number of manipulations performed on an image in order to minimize the amount of deterioration suffered by an image after multiple manipulations.
SUMMARY OF THE INVENTION
The above needs are met by a method and system for enhancing a digital image that stores the original image and a series of codes describing the manipulations performed on the image. Each time the image is retrieved from memory (
110
) for viewing on a display (
120
), the codes are applied to the image to regenerate the enhanced image.
Images are preferably stored in an original image archive (
110
) associated with an image processing system (
108
). Image enhancement codes, in contrast, are preferably stored in an original sequence archive (
122
) also associated with the image processing system (
108
).
When an image not presently being displayed is retrieved from the image processing system (
108
), the original image is retrieved from the original image archive (
110
), and the associated original image enhancement code sequence is also retrieved from the original sequence archive (
122
). The codes are received by an optimizer (
126
) associated with the image processing system (
108
). If the image enhancement codes have not been previously optimized, the optimizer (
126
) combines, changes and reorders the image enhancement codes in light of certain criteria. One criterion is typically minimizing information loss caused by unintentionally lossy image manipulations. Accordingly, the optimizer (
126
) combines, changes, and reorders the codes to minimize unintentional information loss in the transformation of the original image to the enhanced image.
Once the optimizer (
126
) has combined, changed and reordered the codes, it stores the optimized code sequence in the alternate sequence cache memory (
124
), and marks it as “optimized.” Image processing system (
108
) applies the manipulations specified by the optimized codes to the original image and produces an enhanced image. The enhanced image is stored in enhanced image cache (
114
) and marked as “optimized.” The enhanced image (
114
) is retrieved by the image processing system (
108
) and displayed on the display (
120
).
When additional manipulations are applied to the displayed image, an embodiment of the present invention optimizes the codes each time new codes are applied. The new codes are appended to the end of the sequence of codes already stored in both the original sequence archive memory (
122
) and the alternate sequence caches (
124
) and the codes in the alternate sequence cache memory (
124
) are remarked as “not optimized.” The optimizer (
126
) updates the codes in alternate sequence cache memory (
124
), which are remarked as “optimized.” Then the image data in enhanced image cache (
114
) is updated using the reoptimized codes in alternate sequence cache memory (
124
), and the updated image is forwarded to the display (
120
). An alternative embodiment of the present invention applies the added codes to the image data in the enhanced image cache (
114
) immediately, without optimization of the sub-sequence of newly added codes or the whole sequence.
The optimizer (
126
) initially uses the mutual independence of certain code types to optimize the codes. Image enhancement codes can describe geometric, palette, or mixed manipulations. Mixed manipulations involve a coupling of geometric and palette transformations, so are neither purely geometric nor purely palette. For example, a palette adjustment that is applied to only a selected portion of an image is a mixed transform. Often, consecutive codes of these three types can be commuted, swapped in the sequence, or merged into a single code for a simple or compound transform, depending on the specifics of the two codes. The optimizer
126
takes advantage of commutation properties to adjust the code sequence in preparation for code merging. Reducing the number of codes in the sequence is generally beneficial to the preservation of information. For example, after processing allowed commutations, consecutive rotation codes are combined into a single rotation equal to the sum of the individual rotations. More generally, consecutive geometric transforms can often be combined into a single compound geometric transform represented by a single geometric code. Likewise, consecutive palette transforms can often be combined into a single compound palette transform represented by a single palette code.
The optimizer (
126
) may also use heuristics to optimize the codes. Consecutive mixed transforms may be combined, if their coupled processes are mutually compatible, a determination that is made on an individual basis given explicit knowledge of the specific mixed transforms involved. The same restriction holds for combining two consecutive transforms when one is mixed and the other is either pure geometric or pure palette.
REFERENCES:
patent: 4833625 (1989-05-01), Fisher et al.
patent: 5694484 (1997-12-01), Cottrell et al.
patent: 5740267 (1998-04-01), Escherer et al.
patent: 5835627 (1998-11-01), Higgins et al.
patent: 5838837 (1998-11-01), Hirosawa et al.
patent: 5881178 (1999-03-01), Tsykalov et al.
Garland Harry T.
Roberts Michael G.
Canon Kabushiki Kaisha
Fenwick & West LLP
Rogers Scott
LandOfFree
Optimized enhancement of digital images does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optimized enhancement of digital images, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optimized enhancement of digital images will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2470595