Imaging of pixel defects in digital detectors

Details Imaging of pixel defects in digital detectors Imaging of pixel defects in digital detectors

1999-04-30

2003-12-09

Christensen, Andrew (Department: 2615)

Television

Camera, system and detail

Combined image signal generator and general image signal...

C378S098800, C378S098110, C378S098120, C378S004000, C600S425000

Reexamination Certificate

active

06661456

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to imaging systems. More particularly, the present invention relates to a digital imaging system equipped to detect and display defects contained within the imaging detector.
Imaging systems include systems where images are generated by, x-ray, magnetic resonance imaging (MRI), ultrasound, computerized tomography (CT), or such nuclear medicine techniques as positron emission tomography (PET) or single photon emission computerized tomography (SPECT). In each system, a source of electromagnetic radiation (e.g., x-rays) emits radiation which passes through a body of interest and is detected by some kind of detector. Various structures of various densities in the body of interest absorb the radiation differently, such that the radiation detected by the detector provides information on the structures.
Imaging systems are often used to provide detailed information on structures inside the human body. For example, CT scans of the head are useful for evaluation of head injury and detection of tumor, stroke, or infection. Imaging devices are also useful for the detection of pathologies, or manifestations of diseases such as cancer.
Conventional digital image detectors are, nevertheless, known to lose image information at locations in the detected image which contain a detector defect. These defects are typically called “bad pixels.” In general, bad pixels are image elements which either do not respond electrically or have a behavior that is statistically different from surrounding pixels in the detector array.
Generally, detection of bad pixels in an imaging system is accomplished by imaging a standard set of test phantoms, such as flat fields, with predetermined imaging techniques. Depending on the number of bad pixels and their proximity to other bad pixels in the detected image, clusters of bad pixels may result and clinically relevant information may be lost.
Thus, there is a need to alert the user of imaging systems as to the location of bad pixels and/or clusters of bad pixels in the displayed image. Further, there is a need to avoid medical misdiagnosis caused by unawareness of detector defects. Even further, there is a need to provide critical information to algorithms which are used to detect local statistical image variations which may mistakenly quantify detector defects as pathologies.
BRIEF SUMMARY OF THE INVENTION
One embodiment of the invention relates to a method for displaying an image generated by at least one detector of an imaging unit. The method includes creating a pixel map identifying locations of bad pixels in an array of pixels in the image detected by the at least one detector, linking the pixel map to the image, and providing for selective display of the pixel map. Bad pixels include pixels which do not respond electrically and/or pixels which are statistically different from surrounding pixels in the array of pixels.
Another embodiment of the invention relates to an apparatus for displaying an image generated by at least one detector of an imaging unit. The apparatus includes means for creating a pixel map identifying locations of bad pixels in an array of pixels in the image detected by the at least one detector, means for linking the pixel map to the image, and means for providing for selective display of the pixel map. Bad pixels include pixels which do not respond electrically and/or pixels which are statistically different from surrounding pixels in the array of pixels.
Another embodiment of the invention relates to an apparatus for displaying an image. The apparatus includes an imaging unit, at least one detector unit, a processing unit, and a display. The imaging unit generates x-rays which pass through a body of interest having a structure. The at least one detector unit detects the x-rays which pass through the body of interest to form an image. The image includes an array of pixels which contain information on the structure. The processing unit is coupled to the at least one detector unit and identifies bad pixels within the array of pixels in the image formed by the at least one detector unit. Bad pixels include pixels which do not respond electrically and/or pixels which are statistically different from surrounding pixels in an array of pixels. The display is coupled to the processing unit and provides visual display of the image and selectively displays the bad pixels.


REFERENCES:
patent: 5047863 (1991-09-01), Pape et al.
patent: 5272536 (1993-12-01), Sudo et al.
patent: 5657400 (1997-08-01), Granfors et al.
patent: 5854655 (1998-12-01), Watanabe et al.

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