Shape analysis interpretation

Dear SlicerSALT team,

Currently using SPHARM-PDM analysis, I wonder what interpretation could be given when there are surface differences between two groups but no volume differences (assessed with 2 different methods). It seems quite difficult to use the term “atrophy”… Moreover, the displacements are generally both inward and outward. What is the current physiopathological interpretation of this?

Best regards,


  • Displacement differences locally can be due to local atrophy or growth, even if there is no global volume difference as small local size/volume differences may not rise to significant global size/volume differences.

  • Alternatively, there may be growth in one section and atrophy in another, thus you have local size differences that even out for a global analysis

  • Finally, you can also a local surface deformation differences without local volumetric differences, that usually then indicates that the surrounding of the structure is changing (e.g. a larger neighboring structure)

The visualizations of shape differences should provide insight to which situation you have, though we are aware that we need better & more intuitive visualizations