Extrapolative reconstruction method for helical scanning

Claim 1

A method of producing a tomographic image of an image object from data acquired in a helical scan, the data collected in a series of fan beam projections at a plurality of gantry angles θ about a z axis and within an image plane, the fan beam projections including a plurality of data at fan beam angles φ, comprising the steps of: a) identifying a slice plane z sp relative to the imaged object and parallel to he image plane; b) moving the imaged object along the z-axis and rotating the gantry so that the imaging plane crosses the slice plane at a gantry angle of π; c) acquiring a first partial projection set of data for π radians of gantry rotation prior to the imaging plane crossing the slice plane; d) acquiring a second partial projection set of data for π radians of gantry rotation subsequent to the imaging plane crossing the slice plane; e) dividing the data of the first and second partial projection sets into a first and second half scan projection set each half scan projection set including projection data on both sides of the imaging plane; f) extrapolating and interpolating the data of the first and second half scan data to data at the slice plane; and g) reconstructing a tomographic image from the slice plane data.

Claim 2

A method of producing a tomographic image of an image object from data acquired in a helical scan, the data collected in a series of fan beam projections at a plurality of gantry angles θ about a z axis and within an image plane, the fan beam projections including a plurality of data at fan beam angles φ, comprising the steps of: a) identifying a slice plane z sp relative to the imaged object and parallel to he image plane; b) moving the imaged object along the z-axis and rotating the gantry so that the imaging plane crosses the slice plane at a gantry angle of π; c) acquiring a first partial projection set of data for π radians of gantry rotation prior to the imaging plane crossing the slice plane; d) acquiring a second partial projection set of data for π radians of gantry rotation subsequent to the imaging plane crossing the slice plane; e) dividing the data of the first and second partial projection sets into a first and second half scan projection set each half scan projection set including projection data on both sides of the imaging plane; f) extrapolating and interpolating the data of the first and second half scan data to data at the slice plane; and g) reconstructing a tomographic image from the slice plane data.