X-ray or gamma ray systems or devices – Electronic circuit – With display or signaling
Reexamination Certificate
2000-05-10
2003-04-08
Porta, David P. (Department: 2882)
X-ray or gamma ray systems or devices
Electronic circuit
With display or signaling
C378S098900, C258S005000
Reexamination Certificate
active
06546075
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to novel X-ray or gamma-ray systems capable of detecting and resolving X-rays or gamma-rays of different energy levels.
BACKGROUND OF THE INVENTION
X-ray and gamma-ray systems have been widely used over the last several decades in the industry and in medicine. Conventional radiography systems include an X-ray source (or a gamma-ray source) for producing a beam of X-rays (or gamma-rays) transmitted through an object, and an X-ray detector (or a gamma-ray detector) for detecting the transmitted radiation on a film or electronically. Alternatively, an X-ray detector may be located relative to the X-ray source to detect scattered X-rays. Electronic X-ray detectors directly convert X-rays to electrical signals, or indirectly detect X-rays by first converting them to secondary optical radiation and then detecting the secondary optical radiation. The electrical signals are then digitized and processed. Digital radiography provides numerous advantages over conventional radiography. The digital data is immediately available and can be processed and enhanced depending on the information to be extrapolated. Furthermore, the digital data may provide quantitative attenuation of the object when the data is calibrated and interpreted in absolute units.
An X-ray source can emit a broad spectrum of X-rays generated by a high-energy electron beam striking a metallic target. X-rays emitted from such polychromatic source are collimated to form a stationary or scanning pencil beam, a fan beam, or a wide area beam. Alternatively, an X-ray source can emit X-rays having two or several energy bands, wherein each energy band of X-rays may be quite narrow and thus considered mono-energetic.
Attenuation of X-rays depends on the thickness of the examined object, its density and its components. Different elements exhibit different relative attenuation of X-rays depending on their atomic number (Z). In the range of about 30 keV to 150 keV, the X-ray attenuation is characterized by three effects: Compton scattering, photoelectric absorption, and coherent scattering. Each material can be identified (i.e., atomic number Z can be calculated) based on its X-ray attenuation arising from Compton scattering and photoelectric absorption. Specifically, Compton scattering is dominant for the low atomic number materials and relatively small for high atomic number materials. Photoelectric absorption is more prevalent for high atomic number materials. Therefore, some medical or industrial applications may need multiple X-ray energy data.
X-ray imaging has been widely used for industrial testing and detection. A conventional X-ray image records the transmission of an object to a broad spectrum of X-rays. An X-ray inspection device uses an X-ray source emitting X-rays collimated relative to an X-ray detector, and a processor for analyzing the detected data and creating an image. X-rays examine or scan an object by a relative movement of the X-ray beam and the object. An X-ray inspection device may use line scanning for inspecting moving objects. Such inspection device uses a conveyor for moving an object, an X-ray source emitting a fan beam of X-rays directed toward an X-ray line detector. An object, usually moving at a constant speed on a conveyor, crosses the fan beam and thus causes X-ray flux variation at the detector. The detector provides successive lines of X-ray data used to create an image.
X-ray imaging has also been widely used in medicine. X-ray based systems are widely used for imaging and for bone densitometry. A conventional X-ray system transmits a wide-area X-ray beam through a patient and the transmitted x-rays are detected by a film or by a detector plate to obtain an image (for example, a chest X-ray). Other medical systems may collimate the generated X-rays into a pencil beam or a fan beam to scan a patient. An X-ray bone densitometer can use a scanning pencil beam or a fan beam directed to a point detector or a linear array of detectors, respectively. The detected radiation depends on the bone density, which is measured to evaluate and/or monitor osteoporosis.
In a CT system a thin fan beam of X-rays is directed through a patient's body and detected by a line detector, usually including a line of individual sensors aligned along an arcuate or linear path. The examined patient is movably interposed between the source and the detector, which are always aligned with respect to the X-ray beam. For each position of the examined patient, the detector detects a fan beam of transmitted X-rays and produces a row of analog signals. The analog signals are digitized and provided to a processing unit that processes the data and provides an image to a display.
Dual energy radiography has been successfully used for medical applications and for detection and characterization of materials. A dual-energy X-ray system uses a single energy, a dual-energy or a multiple-energy X-ray source and at least two energy discriminant detectors. (Alternatively, a dual-energy X-ray system may use a source providing dual energy X-ray pulses and a single detector.) A first and a second energy detector may include a scintillating layer or material (e.g., a scintillating crystal) and optical detector (e.g., a photo diode or a phototransistor) located adjacent to the scintillating material. The two X-ray sensitive layers are aligned serially with respect to the direction of the X-rays. Low energy X-rays are more absorbed in the first sensitive area, while high energy X-rays are more absorbed in the subsequent X-ray sensitive layer. Thus, the first detector is frequently called a “thin” detector and the second detector is called a “thick” detector due to its ability to detect higher energy (harder) X-ray radiation. The individual detectors can be calibrated using two reference materials. The first reference material is usually a plastic such as Plexiglass™ and the second is aluminum. The detector detects high energy and low energy values for known material thickness. Only two basic materials are required to determine the thickness-signal relationship for any other material.
Dual-energy X-ray detectors detect separately X-rays penetrating to different depth ranges based on their energies. Such X-ray detector includes a first strip of crystalline amorphous silicon (or another X-ray sensitive material) having a first surface in which X-rays of a first energy are absorbed. The first surface is disposed substantially perpendicularly to the incident X-rays. A second strip of crystalline or amorphous silicon has a surface in which X-rays of a second energy are absorbed. The second surface is again disposed substantially perpendicularly to the incident X-rays. The X-ray detector may also include an absorber (for example, an X-ray absorbing foil) stacked upstream from the first detector surface. The two X-ray detectors are stacked perpendicularly relative to the direction of X-rays and detect discrete X-ray energies (or energy bands), but cannot detect a continuum of X-ray energies.
Recently, new types of X-ray detectors have been using wide-area X-ray sensitive layers for direct or indirect detection of X-rays. A typical detector may include a two-dimensional, X-ray sensitive area with a plurality of individual sensors oriented substantially perpendicularly to incoming X-rays. These sensors provide again analog signals that are digitized and provided to a processing unit. However, these X-ray detectors cannot discriminate a spectrum or a continuum of X-ray energies.
Two-dimensional X-ray detectors may in the future replace X-ray films. A two-dimensional X-ray detector includes a two-dimensional array of sensors connected to a switching and addressing circuitry. The individual sensors typically include a pair of generally co-planar conductive microplates separated by a dielectric layer forming a charge storage capacitor. A photoconductive layer extends over all the sensors above the microplates. The X-ray detector also includes a top electrode placed over the photoconductive layer. A charg
Chartier Yves
Lippens Francois
EPSIRAD Inc.
Porta David P.
LandOfFree
Energy sensitive detection systems does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Energy sensitive detection systems, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Energy sensitive detection systems will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3101039