Radiant energy – Invisible radiant energy responsive electric signalling – Semiconductor system
Reexamination Certificate
1999-04-15
2001-12-04
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Semiconductor system
C250S370080, C250S580000
Reexamination Certificate
active
06326625
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to apparatus and methods for detecting ionizing radiation images and more specifically relates to apparatus and methods for digital detection of X-ray images.
BACKGROUND OF THE INVENTION
There are described in the patent literature numerous systems and methods for the recording of X-ray images. Conventional X-ray imaging systems use an X-ray sensitive phosphor screen and a photosensitive film to form visible analog representations of modulated X-ray patterns. The phosphor screen absorbs X-ray radiation and is stimulated to emit visible light. The visible light exposes photosensitive film to form a latent image of the X-ray pattern. The film is then chemically processed to transform the latent image into a visible analog representation of the X-ray pattern.
Recently, there have been proposed systems and methods for detection of X-ray images in which the X-ray image is directly recorded as readable electrical signals, thus obviating the need for film in the imaging process.
For example, U.S. Pat. No. 4,961,209 to Rowlands et al. describes a method for employing a transparent sensor electrode positioned over a photoconductive layer and a pulsed laser that scans the photoconductive layer through the transparent sensor electrode.
U.S. Pat. No. 5,268,569 to Nelson et al. describes an imaging system having a photoconductive material which is capable of bearing a latent photostatic image, a plurality of elongate parallel strips adjacent the photoconductive material, and a pixel source of scanning radiation.
U.S. Pat. No. 5,652,430 to Lee describes a radiation detection panel for X-ray imaging systems which is made up of a matrix assembly of radiation detection sensors arrayed in rows and columns to record static or dynamic images.
Examples of commercially available systems in which X-ray images are directly recorded as readable electrical signals include the Direct Radiography line of detector arrays offered by Sterling Diagnostic Imaging (formerly DuPont) of Delaware, USA, the Pixium line of flat panel X-ray detectors for radiography offered by Trixell of Moirans, France; the Digital Imaging Center offered by Swissray Medical AG of Switzerland, and the Canon Digital Radiography System offered by the Canon Medical Division of Canon U.S.A.
In addition, digital mammographic X-ray systems are commercially available. For example, the Opdima system offered by Siemens Medical Systems, Inc. of New Jersey, USA.
SUMMARY OF THE INVENTION
The present invention seeks to provide an improved X-ray imaging system and method.
There is thus provided in accordance with a preferred embodiment of the present invention a radiation image detector including an ionizing radiation sensing element which is operative to present an imagewise electrostatic charge distribution in response to imagewise ionizing radiation exposure thereof, a charge generator, in non-contact proximity with the radiation sensing element, which is operative to inject charge onto the radiation sensing element, an optical radiation source which projects visible radiation onto the radiation sensing element; and read circuitry, which detects information-bearing signals, representing the imagewise electrostatic charge distribution, with the signals being created when the charge generator and the optical radiation source are concurrently activated in generally mutual registration.
Further in accordance with a preferred embodiment of the present invention, the imagewise ionizing radiation is imagewise X-ray radiation.
Still further in accordance with a preferred embodiment of the present invention, the ionizing radiation sensing element is a layered stack with the following order: an optically transparent support substrate; an optically transparent conductive layer; an optically transparent dielectric layer; and a photoconductor.
Additionally in accordance with a preferred embodiment of the present invention, the ionizing radiation sensing element is a layered stack with the following order: an optically transparent support substrate; an optically transparent conductive layer; a first dielectric layer; a photoconductor; and a second dielectric layer.
In yet farther accordance with a preferred embodiment of the present invention, the second dielectric layer acts as an optical filter which tailors a radiation spectrum of optical radiation which penetrates into the photoconductor.
Still in further accordance with a preferred embodiment of the present invention, the photoconductor is amorphous selenium or a selenium alloy.
Additionally in accordance with a preferred embodiment of the present invention, the photoconductor is a material selected from the group consisting of lead oxide, thallium bromide, cadmium telluride, cadmium zinc telluride, cadmium sulfide, and mercury iodide.
Preferably, the charge generator of the radiation image detector scans the radiation sensing element.
In further accordance with a preferred embodiment of the present invention, the charge generator includes at least one embedded electrode; at least one exposed screen electrode; with the at least one embedded electrode and the at least one exposed screen electrode separated at a region of proximity by a dielectric medium; an electrical driver which provides an AC voltage between the at least one embedded electrode and the at least one screen electrode causing air discharge at the region of proximity, thus generating positive and negative charges; and a voltage source which provides a DC bias voltage in the range of zero to several thousand volts to the at least one screen electrode, providing the driving force for charge injection.
Additionally, in accordance with a preferred embodiment of the present invention, the DC bias voltage can be selected such that the DC component associated with the Fourier spectrum of spatial frequencies of an image to be detected is reduced.
Preferably, the optical radiation source of the radiation image detector scans the radiation sensing element.
Moreover, in accordance with a preferred embodiment of the present invention, the optical radiation source includes at least one first source of visible radiation which is mainly absorbed at the surface of the photoconductor of the radiation sensing element.
Additionally, in accordance with a preferred embodiment of the present invention, the optical radiation source also includes at least one second source of optical radiation which generally penetrates deeply into the photoconductor of the radiation sensing element.
In further accordance with a preferred embodiment of the present invention, the optical radiation source includes a generally linear array of light emitting diodes.
Still in further accordance with a preferred embodiment of the present invention, the optical radiation source also includes elongate converging optics, and an optical beam shaping enclosure having an elongate opening through which a generally elongate beam of optical radiation may be projected.
Preferably, the generally elongate beam of optical radiation has at least one well-defined elongate edge.
In accordance with a preferred embodiment of the present invention, the read circuitry is removably coupled to the radiation sensing element. Alternately, in accordance with a preferred embodiment of the present invention, the read circuitry is permanently coupled to the radiation sensing element.
There is also provided in accordance with a preferred embodiment of the present invention a module for detection of ionizing radiation images, the module including an ionizing radiation responsive layered substrate arranged to respond to an ionizing radiation image, which includes at least one layer which is segmented into a plurality of parallel strips, and at least one non-segmented layer; and an elongate charge generator operative in association with the ionizing radiation responsive layered substrate to inject charge thereto, transversing at least part of the plurality of parallel strips, and scanning the ionizing radiation responsive layered substrate along a scanning axis w
Edge Medical Devices Ltd.
Hannaher Constantine
Israel Andrew
Pillsbury & Winthrop LLP
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