CellFIT is a package of force-inference solvers and assessment tools. It takes a segmented image of cells as input and first constructs equilibrium equations for the cell edge tensions at each cellular triple junction — based solely on the limiting angles at which cell edges enter the junction. Solving these equations yields a set of relative edge tensions; absolute scaling must be determined from other data. Secondly, if intracellular pressures are also sought, Laplace equations are written for each edge to relate its tension, curvature and pressure difference. Their solution yields a set of gauge pressures, with scaling determined by the edge tensions. These pressures can be offset by reference to surrounding medium, an open wound, or information external to the image. Confidence in forces inferred from experimental images can be assessed using graphical display tools as well as equation outputs such as condition numbers, singular value decomposition, residual analyses and standard errors. Details of the method are described in:

G.W. Brodland, J.H. Veldhuis, S. Kim, M. Perrone, D. Mashburn and M.S. Hutson (2014) “CellFIT: a cellular force-inference toolkit using curvilinear cell boundaries”PLoS ONE 9(6): e99116 (DOI: 10.1371/journal.pone.0099116).

Download a .zip file with a Windows version of Zazu (a 2D version of CellFIT), a User’s Guide and sample data.
This software was written with care and was tested on dozens of data sets; however, it is supplied “AS IS” without any warranties or support. Additional details on cellular force inference are available from Prof. Wayne Brodland’s site at the University of Waterloo.