Image reconstruction in regions-of-interest from truncated projections in a reduced fan-beam scan.

In a reduced fan-beam scan, the scanned angular range is smaller than that in a short scan (i.e., a half-scan). In this work, we have developed a new algorithm, which is referred to as the backprojection-filtration (BPF) algorithm, for exact image reconstruction within ROIs from reduced-scan data containing truncations. Explicit conditions on data acquisition have also been derived for exact image reconstruction within an ROI. We have performed a preliminary quantitative study whose results demonstrated and verified the proposed fan-beam BPF algorithm and the derived conditions on data acquisition. The proposed BPF algorithm can have significant implications for clinical and animal CT imaging, therapy imaging, electron paramagnetic resonance imaging and other tomographic imaging because it allows for reconstruction from truncated data and for a potentially drastic reduction of radiation dose and/or of imaging time.