Fig. 12

Illustration of the LUT-based point-projector. To determine which points are projected on position \(k \in [0, N_s]\) of the sinogram, the matrix \(\mathrm {Pos}\) (bottom) is accessed at index k, and contains the value \(\mathrm {Pos}[k] = p_k\). This value \(p_k\) is a position in LUT J (middle), so that \(J[p_k] = i_1\) is the index of one coefficient being projected at index k in sinogram. The process is repeated for \(p_k +1\), until \(p_{k+1}-1\). The corresponding range in J (shaded orange) indicates coefficient indexes that all are projected on sinogram index k.