Abstract: In an improved Cartesian to polar coordinate transformation, a Cartesian system of discrete data elements is converted to a polar system of discrete data elements. Each Cartesian element is divided into subelements and one of the subelements is designated as the polar system origin. A polar system comprising an intersecting plurality of radial sector lines and a plurality of confocal arcs formed of the subelements is defined about the origin. The lines and arcs define boundaries of polar data elements. The subelements lying within the polar element boundaries are identified and their respective data values are derived from the data values of corresponding Cartesian elements. Polar element data values are calculated based on the data values of the subelements contributing to the polar element. The present transformation technique offers the advantage of few floating point operations and provides a computationally efficient conversion system readily adaptive to changes in system parameters.

Abstract: In an improved method and apparatus for cone-beam reconstruction, a helical cone-beam system is provided, operable in a half-scan configuration, offering volumetric imaging results superior to conventional scanning techniques at double the pitch. The projection data of successive rotation angles are sorted into reordered parallel projections having different spatial positions with respect to the rotating axis. The reordered projections are interpolated to generate interpolated projections having a common spatial position along the rotation axis. The interpolated projections are convolved and backprojected to provide a volumetric image of the object. The invention is applicable to a range of computed tomography applications, including medical scanning, baggage scanning, and industrial product scanning applications.

Abstract: An isolation amplifier circuit with hook switch control includes first and second amplifier stages optically isolated from and coupled to each other. A biasing circuit is optically coupled to the amplifier to provide a switchable prebias to the amplifier to allow the amplifier to process bipolar voltage input signals. A hook switch circuit is coupled to the biasing circuit such that as the bias condition is switched, the hook switch is opened or closed. The same optical coupling circuitry can be used to couple the first and second amplifier stages and to couple the biasing circuit to the hook switch circuit such that savings in circuit space and cost are realized.

Abstract: A rotary heat regenerator wheel in which one or more performance characteristics, such as heat exchange efficiency and air flow rate, can be adjusted during manufacturing, during or after installation and/or after use of the regenerator. The wheel comprises removable segments having differing performance characteristics. One embodiment of the regenerator wheel includes segments containing both latent and sensible heat exchange material. Latent heat transfer efficiencies between those provided by heat regenerators having segments made only of sensible heat exchange material, and by regenerators having segments made only of latent heat exchange material, are achieved by adjusting the ratio of segments with exposed surface area of latent heat exchange material relative to segments having exposed surface area of the sensible heat exchange material. In another embodiment the air flow, pressure drop or surface area density of the wheel can be adjusted by using segments having different surface area densities.

Abstract: The disclosed pressure transducer assembly includes an external enclosure, a thermal shell disposed within the external enclosure, and a pressure sensor disposed within the thermal shell. The pressure sensor senses the gas or vapor pressure present in a tube coupling the sensor to a source of pressurized gas or vapor. The assembly includes a device for heating the thermal shell, and thermal insulation is disposed between the thermal shell and the external enclosure. The thermal insulation includes a plurality of metalized high temperature films stacked one on top of another and a plurality of spacer layers, each of the spacer layers being disposed between adjacent ones of the metalized high temperature films.

Abstract: Heat transfer catheter apparatus and methods of making and using same are disclosed wherein a fluid connection is provided between the distal portions of two adjacent, thin-walled, high strength fluid lumens to define a closed loop fluid circulation system capable of controlled delivery of thermal energy to or withdrawal of thermal energy from remote internal body locations.

Abstract: A nutating slice CT image reconstruction apparatus and method generates a set of projection data using helical cone-beam scanning. The three-dimensional projection data is used to reconstruct a series of planar image slices. The slices are selected such that they define a tilt angle and a rotation angle with respect to the longitudinal axes of the object being scanned. Successive slices have equal tilt angles but changing rotation angles such that normal axes of successive slices define a nutation and precession about the longitudinal axis of the object. Projection data for the tilted slices are formed of selected one-dimensional fan-beam data. As such, the projection data can be applied to conventional two-dimensional reconstruction approaches to generate an image. The projection data can also be used to generate two-dimensional projection images at one or more stationary projection angles through an object being scanned.

Abstract: The disclosed CT scanner includes an X-ray source and an array of X-ray detectors fixed to a reduced geometry disk which is supported for rotation about an isocenter of the disk. The X-ray source is a reduced power source and a beam hardening filter of reduced size is positioned proximal to the X-ray source so the scanner uses a relatively soft X-ray beam. The scanner further includes circuitry for compensating for non-linearities and channel-to-channel variation in the X-ray detectors.

Abstract: An improved data acquisition system filter, optimized for the time domain and for use in a computed tomography scanner of the type using x-ray focal spot wobble, includes a filter time response F(t) which is a function of the waveform w(t) used to drive the focal spot from one position to the other.

Abstract: A system for and method of generating a reconstructed tomographic image is described using an asymmetric detector array during a helical scan. An improved helical weighting system applies a helical halfscan technique to data collected by a symmetric portion of an asymmetric detector system and applies a helical fullscan technique to data collected by an asymmetric portion of the asymmetric detector system. The preferred system comprises an equi-angle interpolator, a streak artifact suppression filter, and an isocenter interpolator that preserve the distinction between even and odd data points in parallel beam projection data.

Abstract: The disclosed detector system includes a two dimensional array of detectors for use in generating a volumetric scan of objects moving through a scanner. The array can comprise rows and columns of square detectors, or alternatively at least two types of detectors, one for providing high image resolution in a direction parallel to or within a plane containing the X- and Y-axes of a CT scanner, and the other for providing high image resolution e direction of the Z-axis of the scanner. Preferably, a first set of detectors is oriented in one direction and a second set of detectors is oriented in a different direction. The disclosed detector system may be used in connection with CT scanners and, in particular, with CT baggage scanners and is particularly useful for detecting the presence of thin objects such as sheet explosives within scanned baggage.

Abstract: A nutating slice CT image reconstruction apparatus and method generates a set of projection data using helical cone-beam scanning. The three-dimensional projection data is used to reconstruct a series of planar image slices. The slices are selected such that they define a tilt angle and a rotation angle with respect to the longitudinal axes of the object being scanned. Successive slices have equal tilt angles but changing rotation angles such that normal axes of successive slices define a nutation and precession about the longitudinal axis of the object. Projection data for the tilted slices are formed of selected one-dimensional fan-beam data. As such, the projection data can be applied to conventional two-dimensional reconstruction approaches to generate an image.

Abstract: Variable-response photodetectors adapted to compensate for nonuniformity along an axis of a scintillating crystal by means of multi-element photodiodes and systems for selectively activating different photodiode sub-elements are disclosed, together with arrays of such photodetectors and X-ray detection systems utilizing such photodetectors.

Abstract: A method and apparatus for identifying an object having an identifying feature includes a two step process for detecting the identifying feature. The process involves locating the feature based upon a first characteristic of the feature and then verifying that feature is the identifying feature based upon a second characteristic of the feature. Preferably, the first step of the process is less discriminating and substantially faster than the second step. This permits the process to be performed rapidly without reducing accuracy.

Abstract: The present invention is directed to an x-ray source for irradiating a surface defining a body cavity in accordance with a predetermined dose distribution. The source comprises a housing, an elongated tubular probe, a target assembly, and an inflatable balloon. The housing encloses an electron beam source and includes elements for generating an electron beam along a beam path. The tubular probe extends along a central axis from the housing about the beam path. The target assembly extends along the central axis and is coupled to the end of the probe distal from the housing. The target assembly includes a target element is positioned in the beam path. The target element is adapted to emit x-rays in response to electrons incident thereon from the beam. The probe tip assembly and associated control electronics include elements for positioning the target element in the beam path, and is substantially x-ray transparent.

Abstract: An apparatus is disclosed for measuring the pressure of a liquid column enclosed within a pressurized tank or cell, and for deriving the height and/or density of the liquid column based on the measured pressure. The apparatus includes a first pressure sensor for differentially measuring the pressure within the cell relative to a reference pressure at a first height, and further includes a second pressure sensor for differentially measuring the pressure within the cell relative to a reference pressure at a second height. A feedback network is operative to match the reference pressure to the pressure within the cell at one of the first and second heights. The feedback network ensures that the sensor detecting the one region is maintained at a zero or null differential pressure condition, enabling the use of a small dynamic range sensor.

Abstract: Layered carbon-carbon composites having improved interlaminar tensile strength are disclosed together with a process for making such composites. A metal catalyst is first deposited on a panel comprising a plurality of layers of carbon fiber cloth. The panel is then exposed to a gaseous hydrocarbon in an inert atmosphere at elevated temperature in order to promote the growth of graphite whiskers between the carbon cloth layers.

Abstract: Disclosed are methods and kits for screening for compounds which bind to a target RNA, for isolating a target RNA from a sample, and for determining the presence and serum level of an aminoglycoside antibiotic in a subject. Also disclosed are kits for diagnosing the presence and identity of a bacterium or virus, and methods of increasing the potency of the binding interaction between an aminoglycoside antibiotic and a target RNA.

Abstract: An apparatus for measuring the angle of flexure between an elongated body limb and the portion of the body to which the limb is affected. The apparatus can be used to monitor flexure between a thigh and lower portion of a human leg. The apparatus is useful during the performance of rehabilitative knee-bends includes means for coupling the apparatus to the thigh, and two gravity actuated switches for monitoring the angle between a long axis of the thigh and vertical axis. The apparatus indicates when the extreme points of the knee-bend have been crossed.

Abstract: A coplanar photodiode construction is disclosed having particular utility in X-ray detection applications in which alternating P-doped and N-doped regions, separated by undoped material, are located in relatively shallow depth under and along the surface between the photodiode and an associated X-ray scintillating crystal.