X-ray or gamma ray systems or devices – Electronic circuit – With display or signaling
Reexamination Certificate
1999-12-21
2001-09-18
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Electronic circuit
With display or signaling
C382S254000, C378S062000
Reexamination Certificate
active
06292535
ABSTRACT:
TECHNICAL FIELD
This invention relates to digital X-ray imaging, and more particularly to such imaging which provides an enhanced greyscale digital display image from a digital camera image.
BACKGROUND
Heretofore, radiologists manually adjusted the brightness and contrast of the display image to suit the radiologists visual preference, and to accommodate the nature of the internal structure being examined. Variation in X-ray intensity at the detector camera varied due to such factors as manufacturing tolerances, tube aging, detector position, and patient body type. This radiation variation caused shifts in the greyscale of the camera image. An increase in radiation promoted an over exposed light images, and a decrease in radiation promoted an under exposed dark image.
A calibrating wedge of known attenuation was imaged permitting the radiologist to manually calibrate the display image. The calibrating wedge had a thick high attenuation end simulating bone structure which attenuated radiation producing an under exposed light image. The calibrating wedge also had a thin low attenuation end simulating soft tissue which readily passed radiation producing an over exposed dark image. The radiologists used these light and dark images (and the greyscale tones therebetween) as a guide to adjusting the display image.
SUMMARY
It is therefore an object of this invention to provide a digital X-ray imaging system and method which automatically compensates for light and dark images to provide an enhanced digital display image formed by display greyscale from a digital camera image formed by camera greyscale.
It is another object of this invention to provide such a system and method which automatically selects a dynamic range from the camera image to conform to the display dynamic range available on the display monitor. The dynamic range of any particular camera image is usually much less than the full greyscale range of the camera. The camera has unused light greyscale levels above the opaqueness of interest, and unused dark greyscale levels below the transparency of interest. This underemployment of greyscale levels is not passed on the display image. Every greyscale level of the display image is employed as a greyscale level within the selected dynamic range. None of the display greyscale levels are wasted on these opaque and near opaque light tones, and on transparent and near transparent dark tones. All of the display image greyscale levels are in the range of the internal structure of interest.
It is a further object of this invention to provide such a system and method which automatically enhances the display image in response to the highest and lowest calibrated attenuator.
It is a further object of this invention to provide such a system and method which automatically enhances the display image in response to calibrated attenuators dedicated to various body types.
It is a further object of this invention to provide such a system and method which locates the collection of pixels forming each calibrated attenuator image within the digital camera image for identifying the particular calibrated greyscale level exhibited by that calibrated attenuator. The camera image address of each pixel collection is determined from the location, permitting the collection to be retrieved for analysis.
It is a further object of this invention to provide such a system and method which eliminates irregular boundary effects along the edge of the attenuator pixel collection. A peripheral region of suspect outer pixels is discarded leaving a main region of reliable inner pixels.
It is a further object of this invention to provide such a system and method which corrects camera greyscale distortion. A series of calibrated attenuator with known attenuations exhibits a corresponding series of greyscale levels. The greyscale intervals between the greyscale levels can be corrected to match the attenuation intervals between the calibrated attenuators.
Briefly, these and other objects of the present invention are accomplished by automatically enhancing a digital display image formed by display greyscale from a digital camera image formed by camera greyscale showing internal structure of interest within a subject. A plurality of calibrated attenuators are provided each having an attenuation which has been calibrated against a known reference attenuation. X-ray radiations are generated at least some of which are calibratedly attenuated within the interior of the calibrated attenuators, and other of which are differentially attenuated within the interior of the subject to reveal internal structure thereof. The plurality of calibrated attenuators and the subject are exposed to the generated X-ray radiations to effect the calibrated attenuated radiations within the calibrated attenuators, and to produce the differentially attenuated radiations within the subject. Detection of the calibrated attenuated radiations provides a plurality of calibrated greyscale levels. Detection of the differentially attenuated radiations provides the digital camera image of internal structure of the subject formed by pixels at greyscale levels within the camera greyscale. Each calibrated attenuator appears in the digital camera image as a collection of adjacent camera pixels exhibiting one of the plurality of calibrated greyscale levels within the camera greyscale. A calibrated greyscale level is retrieved from the digital camera image for each of the attenuator pixel collections. The greyscale is coordinated in response to the retrieved calibrated greyscale levels for determining mapping assignments defining the relationship between the camera greyscale and the display greyscale. The greyscale is mapped in response to the mapping assignments from the coordinator for mapping the camera greyscale levels of the camera pixels forming the digital camera image into display greyscale levels of display pixels forming the enhanced display image. The enhanced display image is displayed employing the display greyscale showing the internal structure of interest within the subject.
REFERENCES:
patent: 6108453 (2000-08-01), Acharya
May Gerald A.
Williams Neil A.
Canon Kabushiki Kaisha
Hentzel Paul
Kim Robert H.
Thomas Courtney
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