Figure 2. Standard versus displacement field‐based measures for the phantom experiment for phantom inserts mimicking tumor shrinkage (upper row) or artifacts (lower row). Superimposed images of the input datasets are shown in (a) and (d), while results assessed with standard evaluation tools are shown in (b) and (e). Complementing the standard image‐based assessment, measures derived from the displacement field provide additional information on the nature of the resulting solution. Discontinuities in the displacement field are identified by the CURL operator in (c) and (f). See for a detailed comparison of field and measure features.