Abstract: A method for correcting emission data from Positron Emission Tomography (PET) or SPECT includes generating a plurality of computed tomography (CT) image data, selecting a portion of the CT image data, processing the selected CT data to generate a plurality of attenuation correction (CTAC) factors at the appropriate energy of the emission data, weighting the CTAC factors to generate an emission attenuation correction map wherein the weights are determined based on the axial location and the slice thickness of the CT data and the axial location and the slice thickness of the PET or SPECT data, and utilizing the generated attenuation correction map to generate an attenuation corrected PET image.

Abstract: An imaging system for generating SPECT images wherein first and second cameras are mounted to a gantry for rotation about an imaging axis, the cameras are positionible in an L configuration wherein their camera axis intersect at an intersection point, the cameras are mounted such that when in the L position the intersection point is further away from each of the cameras than is the rotation axis allowing the cameras to be moved radially inward with respect to the rotation axis thus reducing the degree of table movement within the imaging area required to position an object to be imaged adjacent the cameras.

Abstract: A method of reducing image artifacts in images acquired with fan beam, helical scanning, tomographic imaging systems uses half scans of less than 360.degree. of projection data of an imaged object on each side of the slice plane being imaged. The half scans are weighted with half scan weighting factors to compensate for redundant data and are weighted with helical scanning weighting factors to interpolate the half scans projection data to projection data at the slice plane. The imaged object may be moved one slice thickness for each 360.degree. of scanning so that the half scans are concentrated closer to the slice plane thereby reducing interpolation errors. Alternatively, for a series of slice images, the imaged object may be moved one slice thickness for each half scan to reduce average slice acquisition time.

Abstract: An x-ray CT system includes an array of detector elements which measure the attenuation values of a fan beam. Each detector element is comprised of a set of sub-elements disposed in the slice thickness direction. Attenuation signals from the sub-elements are separately preprocessed and summed together to measure the selected slice thickness and avoid partial volume artifacts in the reconstructed image.

Abstract: A CT apparatus for reducing aliasing in reconstructed images uses an x-ray tube with a translatable focal spot to double the spatial sampling rate, over that achieved by a conventional CT machine, by acquiring a first and second projection corresponding to two different focal spot positions. The amount of gantry rotation and the translation distance of the focal spot are coordinated so that the projections are interlaced and the resulting combined projection is geometrically indistinguishable from a conventional projection with twice the spatial sampling rate. The distance the focal spot is translated is further adjusted to eliminate redundant projections and provide adequate data acquisition time.

Abstract: A reference phantom system for quantitative computer tomography employs a flexible reference phantom with means for urging the flexible reference phantom into contact along the curved surface of the lumbar region of a human patient. In one embodiment, the reference phantom is pre-curved in an arc greater than required. Pressure from the weight of a patient laying upon the reference phantom is effective for straightening out the curvature sufficiently to achieve substantial contact along the lumbar region. The curvature of the reference phantom may be additionally distorted by a resilient pad between the resilient phantom and a table for urging it into contact with the lumbar region. In a second embodiment of the invention, a flexible reference phantom is disposed in a slot in the top of a resilient cushion.

Abstract: A test body or phantom for use in checking the performance of apparatus which detects the emission of radiations from a body includes an element of predetermined shape which incorporates a material having a known level of radiation intensity.