Method for reducing skew image artifacts in helical projection imaging

Claim 1

A method of acquiring projection data on a tomographic imaging system including a means for acquiring a series of projections of an imaged object within an imaging plane at a plurality of angles about a z axis, and a table for translating the imaged object along said z axis with respect to the imaging plane, comprising the steps of: identifying a slice plane at a position relative to the imaged object; translating the table along the z-axis to move the slice plane through the imaging plane; acquiring a tomographic projection set comprised of a plurality of projections of the imaged object; and decreasing the translational velocity of the imaged object during a first period of the acquisition of the tomographic projection set prior to the slice plane crossing the imaging plane and increasing the translational velocity of the imaged object during a second period of acquisition of the tomographic projection set subsequent to the slice plane crossing the imaging plane.

Claim 2

A method of acquiring projection data on a tomographic imaging system including a means for acquiring a series of projections of an imaged object within an imaging plane at a plurality of angles about a z axis, and a table for translating the imaged object along said z axis with respect to the imaging plane, comprising the steps of: identifying a slice plane at a position relative to the imaged object; translating the table along the z-axis to move the slice plane through the imaging plane; acquiring a tomographic projection set comprised of a plurality of projections of the imaged object; and decreasing the translational velocity of the imaged object during a first period of the acquisition of the tomographic projection set prior to the slice plane crossing the imaging plane and increasing the translational velocity of the imaged object during a second period of acquisition of the tomographic projection set subsequent to the slice plane crossing the imaging plane.

Claim 5

The method of acquiring projection data of claim wherein the translational velocity is decreased linearly with respect to time during the beginning projections of the tomographic projection set and increased linearly with respect to time for the end projections of the tomographic projection set.

Claim 6

The method of acquiring projection data of claim wherein the translational velocity varies sinusoidally about a constant average velocity and where the period of the sinusoidal variation is equal to the time required to acquire a projection set.

Claim 8

A method of acquiring projection intensity data I(θ i , φ j ) on a tomographic imaging system including a detector rotatable about a z axis to receive radiation along an imaging plane and a table for translating an imaged object along said z axis comprising the steps of: identifying a slice plane at a z value z sp at a position relative to the imaged object; translating the table along the z-axis to move the slice plane through the imaging plane; acquiring a first tomographic projection set at a first set of z valves comprised of intensity data I 1 (θi 1 , φ j ) of the imaged object; decreasing the translational velocity of the imaged object during a first period of the acquisition of the tomographic projection set prior to the slice plane crossing the imaging plane and increasing the translational velocity of the imaged object during a second period of acquisition of the tomographic projection set subsequent to the slice plane crossing the imaging plane; acquiring a second tomographic projection set at a second set of z values comprised of intensity data I 2 (θi 2 , φ j ) of the imaged object; interpolating with respect to z a tomographic projection set of intensity data I 3 (θi 3 , φ j ) from I 1 (θi 1 , θ j ) and I 2 (θi 2 , θ j ) where the θi 1 and θi 2 differ by an integer multiple of 360°; reconstructing the tomographic projection set I 3 to produce a tomographic image.

Claim 9

A method of acquiring projection intensity data I(θ i , φ j ) on a tomographic imaging system including a detector rotatable about a z axis to receive radiation along an imaging plane and a table for translating an imaged object along said z axis comprising the steps of: identifying a slice plane at a z value z sp at a position relative to the imaged object; translating the table along the z-axis to move the slice plane through the imaging plane; acquiring a first tomographic projection set at a first set of z valves comprised of intensity data I 1 (θi 1 , φ j ) of the imaged object; decreasing the translational velocity of the imaged object during a first period of the acquisition of the tomographic projection set prior to the slice plane crossing the imaging plane and increasing the translational velocity of the imaged object during a second period of acquisition of the tomographic projection set subsequent to the slice plane crossing the imaging plane; acquiring a second tomographic projection set at a second set of z values comprised of intensity data I 2 (θi 2 , φ j ) of the imaged object; interpolating with respect to z a tomographic projection set of intensity data I 3 (θi 3 , φ j ) from I 1 (θi 1 , θ j ) and I 2 (θi 2 , θ j ) where the θi 1 and θi 2 differ by an integer multiple of 360°; reconstructing the tomographic projection set I 3 to produce a tomographic image.