Figure 5.

Comparison of image reconstruction results obtained for the realistic (first column) and simplified (second column) phantoms using 4D algorithms based on the (a) and (b) cubic splines, (c) and (d) spectral and (e) and (f) spline-residue models with different temporal roughness penalties. The plots show image noise (weighted standard deviation, σ_w) versus bias at each reconstruction iteration, and have different scales to allow clear visualisation of performance differences between the different penalty functions.