Image reconstruction from truncated fan-beam projections along a circular trajectory using the virtual fan-beam method.

In this paper, we present five 2D reconstruction formulas, based on the virtual fan-beam (VFB) method, which perform region-of-interest (ROI) reconstruction using truncated fan-beam projections acquired on a circular scan. These formulas can be classified according to the geometry for the backprojection. Two of them do it in a virtual parallel geometry and one in a virtual fan-beam geometry while the last two, which we believe to be new, do it in the fan-beam acquisition geometry. Numerical simulations, using the Forbild head and thorax phantoms, demonstrate the efficacy of our formulas. Spatial resolution analysis and a variance study indicate minor differences between these five VFB formulas.