Projection domain reconstruction method for helical scanning computed tomography apparatus with multi-column detector array employing overlapping beams

Claim 1

A computed tomography apparatus producing images of an imaged object having voxels, the apparatus comprising: an x-ray source directing a beam of x-rays along a beam axis with rotation of the beam axis throughout a plurality of beam angles about a translation axis, the beam including a plurality of rays along paths diverging across the translation axis about a central cone axis at ray angles; an array of detector elements each receiving a ray after it passes through the imaged object, the elements each producing an intensity signal dependant on the attenuation of the ray associated with that element; a translator for moving the imaged object along the translation axis with respect to the x-ray source through a plurality of translation positions during the rotation of the beam axis through the plurality of beam angles so that some voxels of the imaged object are illuminated by a first ray at a first beam angle and a second ray at a second beam angle, the first ray and the second ray being associated with beam angles differing by an integer multiple of 2π radians; a weighting means for weighting the intensity signals associated with the first and second ray prior to reconstruction of a tomographic image to produce weighted intensity signals; a reconstructor receiving the weighted intensity signals and reconstructing a tomographic image from the weighted intensity signals; and a display for displaying the tomographic image.

Claim 6

A method of generating images of an imaged object comprising the steps of: generating an x-ray beam along a beam axis, the beam including a plurality of rays along paths diverging across a translation axis about a central cone axis at ray angles; rotating the beam axis throughout a plurality of beam angles about the translation axis; receiving the rays of the x-ray beam after they pass through the imaged object to produce an intensity signal associated with each ray; translating the imaged object along the translation axis with respect to the x-ray source during the rotation of the beam axis throughout the plurality of beam angles to obtain a projection set so that at least one voxel of the imaged object is illuminated by a first ray at a first beam angle and a second ray at a second beam angle, the first ray and the second ray being associated with beam angles differing by an integer multiple of 2π radians; weighting the intensity signals associated with the first and second ray prior to reconstruction; reconstructing a tomographic image from the weighted intensity signals from the first and second rays; and displaying an image of the tomographic image.

Claim 7

A method of generating images of an imaged object comprising the steps of: generating an x-ray beam along a beam axis, the beam including a plurality of rays along paths diverging across a translation axis about a central cone axis at ray angles; rotating the beam axis throughout a plurality of beam angles about the translation axis; receiving the rays of the x-ray beam after they pass through the imaged object to produce an intensity signal associated with each ray; translating the imaged object along the translation axis with respect to the x-ray source during the rotation of the beam axis throughout the plurality of beam angles to obtain a projection set so that at least one voxel of the imaged object is illuminated by a first ray at a first beam angle and a second ray at a second beam angle, the first ray and the second ray being associated with beam angles differing by an integer multiple of 2π radians; weighting the intensity signals associated with the first and second ray prior to reconstruction; reconstructing a tomographic image from the weighted intensity signals from the first and second rays; and displaying an image of the tomographic image.