Abstract: An apparatus and method for reconstructing image data for a region are described. A radiation source and an array of detectors located on opposed sides of a region are used to generate scan data for the region from a plurality of diverging radiation beams, i.e., a cone beam. The cone beam scan data for the region are converted into parallel beam scan data. The reordered parallel beam scan data are used to generate projection data related to a set of oblique slices for the region, wherein the oblique slices form a non-perpendicular angle with the longitudinal axis of the region. Convolution is applied to the projection data related to each oblique slice. The image data for the region are then generated by three-dimensional back projection of the convoluted projection data along the paths of the interpolated rays.

Abstract: In an improved computed tomography data acquisition sequence, fan-beam or cone-beam projection data are collected in a manner which avoids the need for interpolation during reordering to parallel-beam projections. Rather than sampling all channels in a detector array as a whole at each rotation angle, the channels are sampled sequentially in a predetermined number of groups. A first group is sampled, and following a delay, subsequent groups are sampled. The delay is determined by the angular spacing of the detectors and the gantry rotation speed. The projections within a group can be sampled either simultaneously or successively. The invention is applicable to medical and material imaging systems.

Abstract: In an improved method and apparatus for cone-beam reconstruction, an improved detector array is provided in an asymmetric shape with respect to the translation axis. In a first embodiment, a standard symmetric array is rotated by a tilt angle .alpha. about the beam axis. In a second embodiment, the array is formed to have a substantially helical contour. In this manner, efficient use of detector elements is achieved, system pitch is increased, and image quality is enhanced.

Abstract: In a method and apparatus for progressive correction of ring artifacts in a computed tomography system, multiple-channel ring artifacts are mitigated or eliminated along with single-channel ring artifacts. Detector channels are iteratively grouped into various size groupings, for example, pairs, and the offset error values of each detector channel grouping are determined. The error values corresponding to each detector channel are accumulated at each iteration, and the final accumulated values are applied to captured projection data. In this manner, ring artifacts can be eliminated from the image in just a few iterations.

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: A CT scanner includes support means for supporting a radiation source and a detection system in a predetermined spatial relationship and for rotation about a rotation axis, and means for providing relative translation between an object being scanned and the support means as the radiation source and detection system rotate about said rotation axis so as to provide a scan through a predetermined volume of said object. The detection system comprises a plurality of detectors which are offset from a center line passing from the radiation source through the rotation axis, or includes a detection system which is asymmetrically arranged relative to that center line. In the latter case the detectors can be offset or not. Using acquired data, additional projection data is generated preferably through interpolation techniques so as to provide a complete set of data for a predefined slice plane within the scanned volume, which can be subsequently used to back project a tomogram of the object.

Abstract: In an improved method and apparatus for cone-beam reconstruction, a technique for mitigating reconstruction error, referred to herein as successive approximation, incrementally improves the quality of the resultant image, with an exponential decrease in error at each succession. Projection data are collected and reconstructed to form a first reconstructed image containing error due to imprecision in reconstruction. The first reconstructed image is forward projected to generate intermediate projection data which are in turn compared to the collected projection data to generate error projection data. The error projection data are reconstructed to form an error image which is, in turn, used to correct the first reconstructed image . The result is a second image which is improved in image quality. The invention is applicable to a range of computed tomography applications, including medical scanning, baggage scanning, and industrial product scanning applications.

Abstract: An an aluminum mesh with interlaced hollow and solid ribs. The hollow ribs thereof define large open spaces of the aluminum mesh and the solid ribs thereof further define small open spaces within each large open space, providing the aluminum mesh with varied patterns formed from the interlaced hollow and the solid ribs in only one single stretching operation.

Abstract: An aluminum extruding die comprising a mother die unit having a plurality of tooth-form holes at the middle respectively connected with one another forming into an extruding outlet, and a daughter die unit having a plurality of raised blocks respectively fastened in the tooth-form holes with gaps respectively maintained therebetween for the extrusion therethrough of aluminum material form a hollow, panel-like aluminum workpiece having a plurality of elongated, hollow ribs and a plurality of connecting strips alternatively connected therebetween is disclosed. The hollow, panel-like aluminum workpiece is further stretched into an aluminum mesh having a plurality of hollow ribs with a plurality of open spaces defined therein.

Abstract: An improved shelf structure has a peripheral frame with side frame members. A pair of opposed side frame members carry respective slides which can be adjusted for positioning lengthwise along the side frame members. The slides carry a bracing assembly having pivoted U-shaped braces which can be crossed over and held in place by pegs on one of the braces. Adjustment of the cross-over point of the braces and adjustment of the slides along the side frame members allows the bracing assembly to be suitably adjusted to support the shelf in a horizontal plane.