General Electric Company

Albert H Lonn

Kevin Franklin King

Carl R Crawford

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.

Computed tomographic image reconstruction method for helical scanning

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.

Computed tomography system with translatable focal spot

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. The flexibility of the reference phantom and the stiffness of the resilient cushion are matched so that the reference phantom is deformed as it is urged into contact with the lumber region of a patient whereby substantially continuous contact is achieved with the reference phantom along substantially the entire contiguous length of the lumbar region. The resilient cushion and reference phantom may be enclosed in a flexible container. A partially curved reference phantom is a slot in a resilient cushion is also contemplated.

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Wauwatosa, WI, United States of America

Albert H Lonn