General Electric Company

The University of North Carolina at Chapel Hill

Frank A DiBianca

Dominic A Cusano

Charles D Greskovich

Stephen J Riederer

Thomas E Peterson

Dennis H Pritzkow

Jean-Pierre J Georges

Edmund R Steinike

A detection medium for a kinestatic charge detector is a mixture of gases, typically including at least one noble gas such as zenon or krypton. The medium can be pressurized to improve resolution and temperature can also be applied to the medium for improving resolution. Various additive or dopant gases can also be introduced to improve resolution.

Mixed media for kinestatic charge detectors

A kinestatic charge detector having a chamber, which includes a front wall through which propagating energy enters and first and second electrodes disposed opposite to each other on walls substantially perpendicular to the front wall, also includes a device disposed on the front wall for maintaining the electric field generated by the electrode constant and uniform close to the front wall. The device includes a resistive wire zig-zagged across the front wall and connected between the electrodes.

Continuous-resistance field shaping element for a kinestatic charge

A kinestatic charge detector includes a feedback control system for beam equalizing the radiation flux incident on patients of varying thickness. The control system can be an analog or digital type and controls the intensity of the radiation source or the opening of a collimator through which radiation is directed to the patient.

Beam equalization method and apparatus for a kinestatic charge detector

A kinestatic charge detector, which detects propagating energy includes a gas ionization chamber with an angled window, between top and bottom surfaces of the chamber, for receiving the propagating energy therethrough. A medium is contained within the chamber for interacting with the incident energy to produce secondary energy. The chamber also includes a device for changing the position of the secondary energy relative to the medium and a detecting device for detecting the secondary energy in the chamber.

High performance front window for a kinestatic charge detector

Rare-earth-doped, polycrystalline yttria-gadolinia ceramic scintillators with high density, optical clarity, uniformity, cubic structure and which are useful in the detection of x-rays, include one or more of the oxides of rare earth elements Eu, Nd, Yb, Dy, Tb, and Pr as activators. The ceramic scintillator may also include CaO, SrO, and Yb.sub.2 O.sub.3 as afterglow reducers. Sintering, sintering combined with gas hot isostatic pressing, and hot pressing methods for preparing the ceramic scintillators are also described.

Rare-earth-doped yttria-gadolina ceramic scintillators

A technique for detecting the spatial distribution of propagating energy induces secondary energy produced in a detector to drift in a predetermined direction at a predetermined velocity and synchronously moves the detector in a direction opposite to the direction of drift of the secondary energy at a velocity equal in magnitude to the magnitude of the velocity of drift of the secondary energy. Although the secondary energy is drifting with respect to the detector, the synchronous detector movement causes the secondary energy to appear stationary with respect to a source of radiation, resulting in 'kinestatis' of the secondary energy. The secondary energy resulting from the radiation integrates along stationary paths in the detector (operated as a 'kinestatic detector') and is subsequently detected when a collection volume of the detector sweeps through the stationary secondary energy. Signal integration can occur over long periods of time while resolution in the direction of movement of the detector is determined by the detector output sampling rate. A detector having n-by-l detecting elements can simulate the operation of an n-by-m element detector for use in digital radiography and computed tomography and other imaging and non-imaging sensing techniques. The detector may take the form of a xenon gas ionization chamber. Field distortion eliminating techniques are used to eliminate variations in charge carrier drift velocity in such an ionization chamber. Charge carrier mobility and drift velocity are adjusted to synchronize charge carrier movement with detector movement.

Kinestatic charge detection using synchronous displacement of detecting

An improved scintillator for a solid state radiation detector useful in CT (computed tomography), DR (digital radiography), and related technologies. The scintillator, rather than being grown as a single crystal, is formed by means of hot pressing or sintering, as a polycrystalline ceramic. Rare earth oxides doped with rare earth activators are selected to yield a cubic crystal structure of high density and transmittance, which satisfies radiation detector requirements better than crystals utilized heretofore.

Rare earth ceramic scintillator

A method for preparing high density yttria-gadolinia ceramic scintillators by cold-pressing multicomponent powder to form powder compacts and then sintering the compacts to form transparent-to-translucent ceramic scintillator bodies. The powder compacts are formed by either die pressing or die pressing followed by isostatic pressing to further increase green density. The powder compacts are sintered in vacuum or a reducing atmosphere at a temperatue of between 1800.degree. C. and 2100.degree. C. The preferred heating sequence includes a holding period at a temperature lower than the final sintering temperature. The finished scintillator includes Y.sub.2 O.sub.3, Gd.sub.2 O.sub.3, and one or more of Eu.sub.2 O.sub.3, Nd.sub.2 O.sub.3, Yb.sub.2 O.sub.3, Dy.sub.2 O.sub.3, Pr.sub.2 O.sub.3, and Tb.sub.2 O.sub.3 rare earth activator oxides. At least one of the oxides of elements Zr, Th, and Ta is included as a transparency promoting densifying agent. At least one of CaO and SrO may be included as a light output restorer.

Method for sintering high density yttria-gadolinia ceramic scintillators

Sintering and gas hot isostatic pressing are used to prepare polycrystalline yttria-gadolinia ceramic scintillator bodies. Multi-component powder compacts, formed by cold pressing cold isostatic pressing, are sintered to the closed porosity stage. The density of the sintered compacts is then increased by gas hot isostatic pressing. The finished scintillator includes Y.sub.2 O.sub.3, Gd.sub.2 O.sub.3, and one or more of Eu.sub.2 O.sub.3, Nd.sub.2 O.sub.3, Yb.sub.2 O.sub.3, Dy.sub.2 O.sub.3, Pr.sub.2 O.sub.3, and Tb.sub.2 O.sub.3 rare earth activator oxides. The finished scintillator may also include at least one of SrO and CaO as afterglow reducers.

Preparation of yttria-gadolinia ceramic scintillators by sintering and

A method for preparing high density yttria-gadolinia ceramic scintillators includes cold-pressing a multicomponent powder to form powder compacts and then sintering the compacts to form transparent-to-translucent ceramic scintillator bodies. The powder compacts are formed by either die pressing or die pressing followed by isostatic pressing to further increase green density. The powder compacts are sintered in vacuum or a reducing atmosphere at a temperature of between 1800.degree. C. and 2100.degree. C. The preferred heating sequence includes a holding period at a temperature lower than the final sintering temperature. The finished scintillator includes Y.sub.2 O.sub.3, Gd.sub.2 O.sub.3, and one or more of Eu.sub.2 O.sub.3, Nd.sub.2 O.sub.3, Yb.sub.2 O.sub.3, Pr.sub.2 O.sub.3, Dy.sub.2 O.sub.3, and Tb.sub.2 O.sub.3 rare earth activator oxides. The finished scintillator may also include at least one of SrO and CaO as afterglow reducers.

A radiographic phantom is comprised of only two materials, a non-iodinated material composing the base and an iodinated material disposed in a channel simulating a blood vessel, thus providing for a resultant signal attributable only to the iodinated material when a radiographic subtraction process is conducted to test an apparatus for contrast sensitivity. The phantom is fabricated by forming the base of a plastic material, forming a channel in the base, and then filling in the channel with the same kind of plastic material but with minute amounts of iodine suspended uniformly therein.

Radiographic phantom with iodinated channels

Polycrystalline ceramic scintillators are prepared by a vacuum hot-pressing method. The process includes pressing a multi-component powder at high temperature under vacuum. Following a holding period, the pressure and temperature are increased and maintained for a predetermined length of time. The finished scintillator includes Y.sub.2 O.sub.3, Gd.sub.2 O.sub.3, and one or more of Eu.sub.2 O.sub.3, Nd.sub.2 O.sub.3, Yb.sub.2 O.sub.3, DY.sub.2 O.sub.3, Pr.sub.2 O.sub.3, and Tb.sub.2 O.sub.3 rare earth activator oxides. The finished scintillator may also include at least one of SrO and CaO as afterglow reducers.

Preparation of yttria-gadolinia ceramic scintillators by vacuum hot

Polycrystalline ceramic scintillators are prepared by a vacuum hot-pressing method. The process includes pressing a multicomponent powder at high temperature under vacuum. Following a holding period, the pressure and temperature are increased and maintained for a predetermined length of time. The finished scintillator includes Y.sub.2 O.sub.3, Gd.sub.2 O.sub.3, and one or more of Eu.sub.2 O.sub.3, Nd.sub.2 O.sub.3, Yb.sub.2 O.sub.3, Dy.sub.2 O.sub.3, Pr.sub.2 O.sub.3, and Tb.sub.2 O.sub.3 rare earth activator oxides. At least one of the oxides of elements Zr, Th, and Ta is included as a transparency promoting densifying agent. At least one of CaO and SrO may be included as a light output restorer.

A modular solid state x-radiation detector. A detector array is made up of a plurality of collimator plates having pockets formed in the planar surfaces thereof to carry scintillator bars, and dimensioned so that the edges of the scintillators are shielded by the pockets, yielding several advantages. Wider scintillator bars are thus possible, increasing quantum detection efficiency while guarding against energy dependent punch through at the edges of the scintillator, thereby to enhance spectral linearity. The arrangement also prevents x-rays from bypassing the scintillator, thus protecting the adhesive which bonds the scintillator to the plate and the photodiodes mounted behind the scintillator. A further benefit is an increase in optical transfer of light to the rear of the scintillator where the diode is mounted since there is a less severe aspect ratio of depth to width, reducing the number of reflections encountered by light travelling to the photodiode. The collimator plates are also provided with opposed legs which engage slots in a photosensor assembly to accurately align the photosensor and scintillator.

Solid state detector for CT comprising improvements in collimator plates

Rare-earth-doped, polycrystalline yttria-gadolinia ceramic scintillators with high density, optical clarity, uniformity, cubic structure and which are useful in the detection of X-rays, include one or more of the oxides of rare-earth elements Eu, Nd, Yb, Dy, Tb, and Pr as activators. The oxides of elements Zr, Th, and Ta are included as transparency-promoting densifying agents. Any decrease in scintillator light output, due to the addition of transparency promoting additives, may be partially restored by the addition of either calcium oxide (CaO) or strontium oxide (SrO). Sintering, sintering combined with gas hot isostatic pressing, and hot pressing methods for preparing the ceramic scintillators are also described.

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Chapel Hill, NC, United States of America

Frank A DiBianca