Abstract

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 $V_{ab}=V_a{W}_a+V_b{W}_b$, with $W_a\text{=}{E}_a/\left(E_a\text{+}{E}_b\right)$ and $W_b=1-W_a$. In the result, the overall reproduction exactness of $V_{ab}$ is expected to outperform that of $V_a$, or $V_b$, or $\left(V_a+V_b\right)/2$. In principle, this volume-fusion scheme is applicable for general cone-beam tomography with multiple nonorthogonal and noncircular orbits.

© 2006 Optical Society of America

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