Enhancement of in-plane spatial resolution in volumetric computed
tomography with focal spot wobbling – Overcoming the constraint on number of
projection views per gantry rotation
Affiliations: Department of Radiology, Emory University School of
Medicine, 1701 Uppergate Dr., C5018, Atlanta, GA, USA | Molecular Imaging & Computed Tomography, GE
Healthcare, PO Box 414, W1190, Milwaukee, WI, USA | CT & X-ray Systems, Global Research Center, GE,
One Research Circle, KW-C1309, Niskayuna, NY, USA
Abstract: The spatial resolution of diagnostic Computed Tomography (CT) has
increased substantially, and 3D isotropic sub-millimeter spatial resolution in
both axial and helical scan modes is routinely available in the clinic.
However, driven by advanced clinical applications, the pursuit for higher
spatial resolution and free of aliasing artifacts in diagnostic CT has never
stopped. A method to accommodate focal spot wobbling at an arbitrary number of
projection views per gantry rotation in CT is presented and evaluated here. The
method employs a beta-correction scheme in the row-wise fan-to-parallel
rebinning to transform the native cone beam geometry into the cone-parallel
geometry under which existing 3D weighted cone beam filtered backprojection
algorithms can be utilized for image reconstruction. The experimental
evaluation shows that the row-wise fan-to-parallel rebinning with the
beta-correction can increase the quantitative in-plane spatial resolution
(Modulation Transfer Function) substantially, while the visual spatial
resolution can be enhanced significantly. Consequently, the architectural
designers of CT scanners are no longer constrained to choosing the number of
projection views per rotation determined by gantry geometry. Instead, they can
choose the number of projection views per rotation to optimize the trade-offs
between in-plane spatial resolution and noise characteristics. Therefore, the
presented method is of practical relevance in the architectural design of
state-of-the-art diagnostic CT.
