Abstract: The present invention, in one form, is an apparatus for performing image reconstruction using data obtained by a helical scan. In reconstructing an image in accordance with the present invention, projection data arrays corresponding to data planes associated with the slice to be imaged are generated. Weighting factors are then applied to the data arrays to assign a weight to each particular data element thereby creating a weighted projection data array. The weighted projection data array is then filtered and back projected to create an image data array from which an image slice is generated. In accordance with the present invention, the weighting function used in creating the weighted projection data array is based upon a plane of reconstruction which is not necessarily perpendicular to the z-axis.

Abstract: A frit-sealed x-ray tube includes a glass bulb that supports metallic parts including an anode with a target and a beryllium window. Joint materials are provided of metal with thermal expansion coefficients that approximate the thermal expansion coefficient of the glass bulb. Frit materials having compositions of primarily zinc oxide and lead oxide are used and also have a thermal expansion coefficient that approximates the thermal expansion coefficients of the glass bulb and the joint materials. The frit materials allow a heat resistant and vacuum resistant welding between the glass bulb and the joint materials.

Abstract: The present invention, in one form, is an apparatus for performing image reconstruction using data obtained by a dual beam helical scan. In reconstructing an image in accordance with the present invention, projection data from each fan beam measurement is weighted by weighting factors to obtain a reconstructed slice. The data arrays selected and weighting factors applied vary depending on the table speed and the detector spacing measured at the axis of gantry rotation, i.e., the detector z spacing.

Abstract: This invention relates to the automatic determination of beam parameters and other criteria to determine a dose plan of radiation on a target volume. The method involves determination of geometric and other radiation involvement criteria, with search of a phase space on the incoming direction of the irradiation beam ports. The evaluation of the goodness of fit, based on parameter thresholds and other considerations, makes it possible to search on the entire phase space of possible beam directions towards the target volume so as to improve the treatment planning dosimetry. The invention applies to circular or non-circular collimator shapes, and can be illustrated by use with a linear accelerator (LINAC) as a means for X-ray delivery to a target volume such as a tumor within a patient's body.

Abstract: The sample stage is scanned in a grid pattern with a feed pitch finer than the width of the primary beams, and with X-ray intensities at each point as values, primary and secondary mapping data are prepared. In order to convert the shape and size of the primary beam into a size of each of the mapping data, a beam template is prepared in which portions irradiated with primary beam being"1" and portions not irradiated being "0". The background intensity is determined as a threshold value, and at the positions where the value of the primary mapping data is below the threshold value, beam template is overlaid on the secondary mapping data. Those values in the secondary mapping data corresponding to "1" portions of the beam template are replaced with "0", and this is performed over all the measured points, thereby data closely approximating the actual boundary of the element concerned is obtained on the secondary mapping data.

Abstract: A method and apparatus for identifying an unknown gas by generating an infrared spectrum of the unknown gas using an infrared spectrophotometer that includes a circular variable interference filter, compressing the infrared spectrum of the unknown gas, and comparing the compressed infrared spectrum of the unknown gas to a library of compressed infrared spectra of reference compounds. After comparison, the compressed spectra that most closely match the unknown gas are decompressed and displayed. Because frequency characteristics of circular variable interference filters vary from filter to filter, information designating these frequency characteristics for the particular filter employed are used in generating the infrared spectrum of the unknown gas.

Abstract: An x-ray system and method capable of producing very accurate RTR images corrected for x-ray system inhomogeneities. A three-dimensional correction memory is used to store deviation information relating to system inhomogeneities. The three-dimensional correction memory is indexed by x and y coordinates of the image plane and an attenuation coordinate associated with a plurality of standard samples. The standard samples are exposed in turn, and deviations between the measured attenuation and the nominal attenuation are noted and stored at the x and y coordinates in the attenuation plane for the sample then exposed. The procedure is repeated for a plurality of samples to create a three-dimensional correction array. An object to be imaged creates a set of raw intensity information. The raw information is corrected by accessing the correction memory at the x and y coordinates of each pixel to be corrected and the attenuation coordinate associated with the raw measurement.

Abstract: A mobile x-ray apparatus has a support stand for an x-ray radiator which is mounted together with a control panel to form a unit. This unit is connected to a wheeled carriage so as to be pivotable around a vertical axis as a unit. This results in approximately the same weight distribution being present regardless of the angle at which the x-ray radiator is pivoted with respect to the supporting stand.

Abstract: The present invention discloses a method and system for generating Radon derivative data in a cone beam computerized tomography implementation. Radon derivative data is computed by using a plurality of processors that partition the Radon space among the processors in a manner wherein the totality of the support of the Radon space handled by each processor is approximately equal. More specifically, each processor handles a number of vertical planes in the Radon space which are equally spaced within 180.degree. in the .phi..sub.k orientation. This procedure enables the plurality of processor to equalize the workload in computing the Radon derivative data and to perform the computations in a timely and efficient manner.

Abstract: A calibration system having a radiation source that generates the beam of radiation along the angular directions .theta., .phi.. A first reference element which is separated from the radiation source by a distance of approximately Z.sub.1 is then exposed to the beam of radiation. A second reference element is also present which is separated from the first reference element by a predetermined distance H and is exposed to the beam of radiation. An image detector produces images of the first and second reference elements, wherein the images are separated from each other by a distance R and angle .phi.. The device further includes an angle measurement device that calculates .theta. from the values of Z.sub.1 and H. A position measurement device having first and second sources of radiation that generate respective first and second beams of radiation directed at angles .theta..sub.1, .phi..sub.1, and .theta..sub.2, .phi..sub.2 respectively, toward an object of interest.

Abstract: Methods for making pulsed and continuous discharge plasma light sources for extreme ultraviolet(EUV) projection lithography and soft-x-ray microscopy as well as other applications are disclosed. A first light source of doubly ionized lithium ions emits over a narrow bandwidth of approximately 13.5 nm. A second light source of beryllium ions radiates at approximately 7.60 nm. A third light source of boron ions radiates at approximately 4.86 nm, and a fourth light source of carbon ions radiates at approximately 3.38 nm. Preferred embodiments of apparatus for generating pulsed and continuous discharge sources are disclosed.

Abstract: A fluoroscopic imager for observing a living creature with reduced x-ray dosage uses a video monitor for displaying frames of image samples received during respective ones of frame scan intervals that regularly and successively occur at a display frame rate sufficiently high that brightness flicker is acceptably low to a human observer; an x-ray source that can be gated on for intervals not as long as a display frame; and a fluoroscopic camera, including a raster-scanning video camera and x-ray-to-light conversion apparatus with persistence not appreciably longer than a display frame and frame-filling apparatus. Especially during purely diagnostic procedures, the frame-filling apparatus generates a continuous succession of frames of image samples at the display frame rate by interpolating between successively grabbed frames of image samples.

Abstract: According to the present invention, a material handling system for transporting a device to or from a radiation chamber in which the device is inspected is provided. The system includes a shuttle carriage having a base and two opposing walls, a conveyor mounted between the two opposing walls of the shuttle carriage, and means for moving the shuttle carriage along a path between a loading position and an unloading position. The system also includes a housing that encloses the shuttle carriage and the moving means. The housing has an internal cavity that is fitted to the two opposing walls. The housing also has a first opening coincident with the loading position and a second opening coincident with the unloading position. Further, a drive mechanism is provided for extending the conveyor partially through the first opening and the second opening.

Abstract: The present invention, in one form, utilizes a region of reconstruction ROR in reconstructing an image from projection data. Particularly, once the region of reconstruction is established, a weighting function which is either a linear interpolation or a non-interpolation can be used. If 3.pi. of projection data is used, the weighting function can be divided into three parts. Each part corresponds to .pi. projection views. For a 50% overlapped reconstruction, the entire weighting functions advance .pi. degrees at a time, which synchronizes very well with the boundaries of the weighting functions. Section 1(S.sub.1) will contain projection views from 0 to .pi., section 2 (S.sub.2) contains views from .pi. to 2.pi., and section 3 (S.sub.3) contains views from 2.pi. to 3.pi.. In section S.sub.1, the weighting function is a ramp-up function, in section S.sub.2 the weighting function is a constant, and in section S.sub.3 the weighting function is ramped down.

Abstract: The invention relates to forming an image from a random particle flux. Particles of the flux are detected by a discrete-cell detector having a cell size finer than conventionally used. Preferably, the cell size is sufficiently small that almost all cells of the detector count at most one particle during the image acquisition time. The count data are filtered through a band-limiting filter whose bandwidth lies between a bandwidth corresponding to the detector cell size and the flux bandwidth of interest. Outliers may be flattened before filtering. Neighborhoods around each cell are evaluated to differentiate stationary regions (where neighboring data are relatively similar) from edge regions (where neighboring data are relatively dissimilar). In stationary regions, a revised estimate for a cell is computed as an average over a relatively large neighborhood around the cell. In edge regions, a revised estimate is computed as an average over a relatively small neighborhood.

Abstract: Computer control of a multi-axis radiographic instrument is utilized to prevent contact between moving surfaces of the instrument based on soft limits. The soft limits are established from a legal state table incorporating all combinations of axis movement of the equipment and relating those combinations to contacting or non-contacting states. The legal state table may be used to map efficient paths between a start and ending position and may be augmented with non-contacting transducers which may sense patient movement not incorporated into the legal state table.

Abstract: Tomographic data acquired in a polar reference frame is rapidly converted into data arranged in a Cartesian system suitable for processing and/or display by a program that may operate efficiently on an electronic computer. The program identifies each polar voxel, defining the region of the polar data, to one or more Cartesian voxels that overlap with it. Truncation techniques developed for use with computer graphics are used to determine an area of overlap between the voxels. Areas of overlap are indexed in a conversion table which may be used for rapid conversion between data acquired under these two coordinate systems.

Abstract: X-ray detectors (24) of a CT scanner (10) generate data values which are preprocessed and assembled (26) into binary data lines. The binary data lines are convolved by a convolver (30) which convolves a plurality of data lines concurrently. A backprojector (32) includes a parametric cubic spline preinterpolator (40) which performs a high order interpolation on the convolved data lines and a linear interpolator (42) which performs a linear interpolation on the high order preinterpolated data lines. The interpolated data lines are backprojected into an image memory (34). Data from the image memory (34) is converted (36) to appropriate format for display on a video monitor (38). The parametric cubic spline preinterpolator (40) includes a first adder (52) which adds most adjacent data lines and a second adder (54) which adds next most adjacent data lines. A first barrel shifter (58) shifts the binary sum of the most adjacent data lines by 1-N spaces, where N is an integer, 4 in the preferred embodiment.

Abstract: Modulated light from a light source is incident on the surface of a scattering medium, and light passing through this scattering medium is externally detected. Components having a plurality of angular frequencies .omega..sub.1 and .omega..sub.2 corresponding to photon density waves propagating in the scattering medium are extracted from this detection signal. The extracted signals corresponding to these waves are compared with a signal of original modulated light to be incident on the scattering medium to detect a quantitatively measurable predetermined parameter such as a phase difference at a detection point for each angular frequency. The detected predetermined parameters have a predetermined relationship with absorptive and scattering constituents of the scattering medium. A pair of predetermined parameters are appropriately arithmetically calculated to eliminate the scattering coefficient, so that only the absorption coefficient can be independently calculated.

Abstract: An intelligent automatic gain stabilization method and apparatus for a radiation detection instrument automatically locate the position of a predetermined characteristic within an energy spectrum, automatically determine whether the characteristic is properly located, and automatically provide gain adjustment to the output of the radiation detection instrument to maintain measurement accuracy of the system.