Abstract: The present invention, in one form, is an apparatus for performing image reconstruction using data obtained by a four beam helical scan. In reconstructing an image, projection data arrays are generated. Such projection data is then weighted by weighting factors to generate a weighted projection data array. The weighted projection data array is filtered and back projected to generate an image data array. The image data arrays for the beams are then summed to generate a slice image data array.

Abstract: An improved tissue imaging system is provided, in which tissue can be sheared without direct manual manipulation, so that different perspective images of the tissue can be determined, preferably in a single compression cycle. In one aspect of the invention, a traction system is provided, comprising at least a layer of a radiolucent material dimensioned and constructed such that the layer can pass between tissue and a surface of a tissue imaging device. The radiolucent material has sufficient tensile strength that the layer can slide without tearing against the surface of the tissue imaging device when tension is exerted on the layer, the sliding resulting in movement of the tissue relative to the surface of the tissue imaging device. A method of moving tissue relative to at least one surface of a tissue imaging device is also provided.

Abstract: The present invention, in one form, is a system for producing incremental tomographic images of an object from projection data acquired in a helical scan. The system creates base image data arrays from the projection data. An interpolation algorithm is then applied to the base image data arrays to generate overlapped, or incremental, tomographic images.

Abstract: An x-ray source (12) is mounted to a rotatable gantry (16). The x-ray source irradiates an examination region (14) with penetrating radiation as (i) the x-ray source rotates around the examination region and (ii) a patient coach (30) moves a patient axially through the examination region. Detectors (24) positioned on an opposite side of the examination region converts radiation which has traversed the examination region along spiral paths (80). Data from the detectors are collected and stored (40) in spiral data sets. In the prior art spiral data on either side of a thin slice central plane was interpolated into a thin slice data set, each thin slice data set was reconstructed into a thin slice image, and several thin slice images were combined to make a thick slice image with significant partial volume artifacts. By distinction, an integrating interpolator (42) weights (88) data values in several spiral sets in accordance with a weighting values W.sub.1, W.sub.2, . . .

Abstract: An algorithm for creating a normalization data array to use in generating a three-dimensional image is described. In one embodiment, the algorithm includes performing the steps of acquiring geometric factors from a two-dimensional normalization scan, determining the three-dimensional crystal sensitivities from a three-dimensional phantom acquisition scan, and using such geometric factors and crystal sensitivities, creating a three-dimensional normalization data array.

Abstract: A circuit for performing digital dynamic compression wherein the circuit is readily modifiable to accept different compression procedures and the input and output signals are in digital form. The system utilizes a memory unit (e.g., a random access memory or other form of programmable memory, such as EEPROM) to contain a procedure utilized to transform digital input channel signal to an offset digital value which is determined based on the total energy of a gamma interaction. This offset digital value is then subtracted from the digital input channel data to arrive at the output dynamically compressed value. However, given sufficient memory size, the memory circuit may be implemented to directly output the compressed value. Since a programmable memory look up table is utilized to contain the dynamic compression procedure, different dynamic compression procedures may be readily loaded into the memory from a computer system.

Abstract: A borehole logging tool having a pair of spaced-apart detectors records intensity signals representing the die-away of nuclear radiation in a subsurface formation. Weighted moments of the intensity signals as well as of a model are produced. Corresponding weighted intensity and model moments are equated and simultaneously solved to obtain values for a borehole decay constant, a formation decay constant, and a formation-to-borehole amplitude ratio for each of the pair of detectors. From these values a trained neural network produces intrinsic values of a formation macroscopic thermal neutron absorption cross section, a formation porosity, and a borehole fluid cross section. A log is generated of these intrinsic values versus depth as the logging tool traverses the borehole.

Abstract: A method and system for identifying end systole and end diastole frames within an angiography sequence. A plurality of images produced during an angiography sequence are digitized, producing digital image data in which gray scale values for each of the pixels in the images are represented. The digital image data are input to a computer (48) to determine the frames in which the coronary arteries are most visible. The coronary arteries are made visible in the images by injecting a radio-opaque contrast substance into the arteries. The frames that occur a end diastole are preferred for diagnostic analysis because the arteries are distended, spread apart from each other, and moving very slowly. To identify such frames for further analysis, the total length of edges within a centered window covering approximately one-fourth of each image is determined. The edges represent spatial transitions between relatively light and dark areas in the image that occur across the borders of the coronary arteries.

Abstract: A present invention, in one form, is a method for removing artifacts from image data due to detector degradation. Particularly, data is obtained from a CT system including a detector and an x-ray source. The detector is formed from a plurality of detector cells. In accordance with one form of the invention, a detector degradation signature (S(i)) vector is generated prior to scanning a patient. Subsequent to scanning the patient, if the image data contains a ring error, a detector cell contributing to the error is identified using the detector degradation signature vector. The system then determines if the cell a degraded cell. If such cell is a degraded cell, ring error correction processing is then performed on the image data.

Abstract: A computed tomography method and apparatus conduct a spiral scan of a subject wherein non-uniformities of noise and topical resolution are greatly reduced. A power spectrum S.sub.o for interpolated projections is identified, from which a frequency characteristic H(f,.theta.), of an optimum filter for the projections interpolated from complementary data is determined, with ##EQU1## with .sigma..sub.o.sup.2 being the variance of the quantum noise associated with a projection and w(.theta.) being the spiral weighting.

Abstract: A system for recording fewer of the events that are caused by unwanted photons with greater stability. The system locally determines the energy spectrum and fits for each pixel of the image the determined energy spectrum with a modified trial function composed of: a photopeak component of known energy shape, Compton scatter components having theoretically derived energy shapes and, when applicable, also measured or calculated energy spectra of other unwanted photons. The modified trial function also takes into consideration unknown local deviations in the outputs of electronic components. The amplitude of the photopeak distribution resulting from the fit is used to obtain the local content of wanted interactions in the image. This enables removal of Compton contamination and also the contamination caused by interaction of the gamma photons with lead components.

Abstract: A radiation therapy apparatus includes a compensator having a plurality of leaves to divide the radiation beam into rays each of which may be effectively and individually attenuated over a range of attenuations by controlling the duty cycle of the leaves position between the open and closed states. An apparatus for controlling the compensator accounts for scattering of radiation through the deconvolution of a terma map and calculates a sinogram for controlling the compensator at a variety of angles about a patient using iterated forward and back projections efficiently calculated in frequency space.

Abstract: In an X-ray CT scanner, a first field of view corresponding to a reconstructed area of an image to be displayed is set. An original image data are reconstructed on the basis of a plurality of projection data in a patient in response to the first field of view. Whether or not an imaged region in the patient is larger than the first field of view is judged according to referring the original image data. A second field of view including the imaged region wholly is set in case that the imaged region is larger in area than the first field of view. Beam hardening correction data are produced on the basis of the projection data in the second field of view. The projection data are processed into the image corresponding to the first field of view with an aid of the correction data.

Abstract: The invention provides a polarizing device and a method for producing and utilizing the device. The device produces a modification in radiation flux and provides a bias toward photons approaching a target's face at more or less right angles. Accordingly, the radiation flux polarizing device reduces the number of photons that are not traveling at near right angle to the face of a "target" being irradiated, without significantly reducing photons approaching, or reaching the minimum base point in the target. In a sense, the invention converts a normal isotropic radiation source to one that is anisotropic.

Abstract: To simulate radiation intensity distribution of a radiation beam having a field region, a penumbra region, and a scatter tail region changes in radiation intensity distribution of a reference radiation beam in the penumbra region at a reference distance from the radiation source are determined. Next, radiation intensity distribution, at the reference distance, of a radiation beam of arbitrary shape, in the field and tail regions is determined. The radiation intensity distribution of the radiation beam of arbitrary shape is simulated by superimposing the changes in radiation intensity of the reference radiation beam in the penumbra region on to the radiation intensity of the radiation beam of arbitrary shape in the field region and the tail region.

Abstract: A tomographic image at a given slice position is normally reconstructed by executing convolution and back projection calculations of virtual view data obtained by interpolating projection data in a range of 360.degree.+a double fan angle before and after the slice position, and their reflection beam data. A tomographic image at a slice position adjacent to the given position is calculated in such a manner that the convolution and back projection calculations of the difference between data used in reconstruction of the tomographic image at the first slice position, and data necessary for normally reconstructing a tomographic image to be reconstructed at a current slice position are executed, and the calculation result is added to the already reconstructed tomographic image.

Abstract: A system is provided for improving the operation of a computed tomography system in forming an image of an object, wherein a cone-beam source is employed to project an image of the object onto a detector plane to provide a set of cone-beam projection data, and such data is to be converted into a set of Radon data for use in constructing the desired image. In the invention, a line L' is rotated in the detector plane from a line L about a center of rotation which lies on the line L, so that L' lies at a small angle with respect to line L. Data from the cone-beam projection data set is respectively integrated along the first and second lines to generate first and second weighted line integrals respectively corresponding to the lines L and L' The two weighted line integrals are then employed to find the derivative of one of the data points in the Radon data set.

Abstract: A method for quantitatively determining bone mineral mass by a CT system, comprising scanning an objective region together with a plurality of samples produced by mixing a water equivalent material with various ratios of a standard material equivalent to bone mineral mass and determining the bone mineral density of the objective region with reference to the CT numbers of the samples, wherein a plurality of samples are scanned together with the objective region at one or multiple levels of tube voltage and a corrected CT number of each sample is calculated by substituting the CT number of each of the samples with the CT number of blood or a standard material equivalent to blood. By scanning at a single level of tube voltage, bone mineral density is determined, on the basis of the CT number of the objective region and with reference to the corrected CT numbers.

Abstract: A method of and device for forming X-ray images in which a charge pattern corresponding to the X-ray intensity generated on the surface of a photoconductor is line-wise scanned by a number of probes which detect the charge in respective adjoining scanning zones of the photoconductor containing a plurality of lines eliminates stripes occurring in the line direction in the image. This is accomplished by: a) formation of correction values (K.sub.n (x,y.sub.o)) for the pixels of the image line (y.sub.o) at the edges of the scanning zones of the probes (41), the absolute value and sign of the correction values being such that corrected image values (B.sub.kn (x,y.sub.o)) of the individual probes, resulting from the superposition of the correction values and image values (B.sub.n (x,y.sub.o)), correspond to the corrected image values of the respective neighboring probes; b) formation of intermediate values (Z.sub.

Abstract: A medical X-ray image processing apparatus, comprising an X-ray sensor which converts an image of X-rays penetrated an object into an electric signal using a solid-state image sensor and a data processor which processes the electric signal to generate an electric image signal corresponding to the X-ray image, compares the data of each picture element derived from the above-mentioned solid-state image sensor with the data of picture elements being adjacent to the picture element and present within a certain region, and corrects the data of the picture element referring to the data of the above-mentioned adjacent picture elements only when the data of the picture element is exceptionally different from the data of the adjacent picture elements by a predetermined reference value or more.