Volume fusion for two-circular-orbit cone-beam tomography

摘要

By using the Feldkamp-Davis-Kress (FDK) algorithm, we can efficiently produce a digital volume, called the FDK volume, from cone-beam data acquired along a circular scan orbit. Due to the insufficiency of the cone-beam data set, the FDK volume suffers from nonuniform reproduction exactness. Specifically, the midplane (on the scan-orbit plane) can be exactly reproduced, and the reproduction exactness of off-midplanes decreases as the distance from the midplane increases. We describe the longitudinal falling-off degradation by a hatlike function and the spatial distribution over the object domain by an exactness volume. With two orthogonal circular scan orbits, we can reconstruct two FDK volumes and generate two exactness volumes. We propose a volume fusion scheme to combine the two FDK volumes into a single volume. Let V_(a) and V_(b) denote the two FDK volumes, let E_(a) and E_(b) denote the exactness volumes for orbits (GAMMA)_(a) and (GAMMA)_(b), respectively, then the volume fusion is defined by V_(ab) velence V_(a)W_(a) + V_(b)W_(b), with W_(a) velence E_(a)/(E_(a) + E_(b)) and W_(b) velence 1 - W_(a). In the result, the overall reproduction exactness of V_(ab) is expected to outperform that of V_(a), or V_(b), or (V_(a) + V_(b))/2. In principle, this volume-fusion scheme is applicable for general cone-beam tomography with multiple nonorthogonal and noncircular orbits.