Favorable noise uniformity properties of Fourier-based approaches to interpolation in helical CT with implications for 3D visualization

This paper describes and evaluates two new approaches to longitudinal interpolation in single-slice helical CT that represent a step toward the goal of achieving essentially isotropic resolution and noise properties in reconstructed helical CT volumes. Both approaches exploit the fast Fourier transform and the Fourier shift theorem to generate from the helical projection data a set of fan-beam sinograms corresponding to equispaced transverse slices. Slice-by-slice reconstruction is then performed by use of two-dimensional fan-beam algorithms. The first approach, called 360FT, makes use only of the directly measured projection data, but the second approach, called 180FT, exploits the redundancy of fan-beam data acquired over 360° to generate a second set of longitudinal samples at each projection angle and bin. These approaches, and particularly the 180FT approach, have been shown under certain conditions to produce reconstructed volumes with more isotropic resolution and aliasing properties than do existing approaches based on the use of linear interpolation. We present evidence that the approaches also have favorable noise uniformity properties relative to currently used approaches