Cone-beam CT with a modified reverse helical trajectory for long object problem

We have applied two algorithms - chord-based backprojection-filtration (BPF) algorithm and Pack-Noo formula- based filtered-backprojection (FBP) algorithm - to reconstructing exact images from data acquired by a reverse helical CBCT. To achieve exact image reconstruction of a long object in a reverse helical CBCT, we have proposed an additional line scan with the chord-based algorithm. The added line scan yields additional chords that can completely fill the reconstructed the volume, thus avoiding the reconstruction gap when only a reverse helical trajectory is used. Numerical examples demonstrate the validity of the proposed method.