The torsion distribution of cell paths in two-phase flow of a cell suspension through a porous medium is an important quantity for chromatographic processes. It can be estimated from cell tracking in sequences of three-dimensional images of a suspension pumped through the medium, where the images are acquired by in-situ time-resolved microtomography using synchrotron radiation and inline phase contrast modus. This contribution presents a new method for estimating path torsion from discrete positions, where the estimation is based on an appropriate discretization of the differential-geometric formula of the torsion of a space curve. Investigations performed for an alcoholic suspension of silica gel particles pumped through a partially open polyurethane foam show that the shape of the inner surface of the foam has a considerable impact on the particle paths. It turns out that the variance of the torsion for slow particle moving close to the surface is a half order of magnitude smaller than that of fast particles, which underlines the importance of torsion for filter efficiency. Lay Description Torsion estimation of particle paths through porous media observed by in-situ time-resolved microtomography Chromatographic processes are used to separate cells of specific type out of a suspension of a mixture of cells. Many chromatographic processes are based on filtering of the suspension, where the inner surface of the filter medium is modified in such a way that specific cells interact with the surface. The design of the filter is important for increasing the efficiency of chromatographic processes. For this reason we observe the flow of cell suspensions through the pore space of the filter based on fast micro-computer-tomography. The torsion distribution (i.e. the distribution of second curvature) of cell paths in the flow of a cell suspension through the pore space is an important quantity for chromatographic processes. It can be estimated from cell tracking in sequences of three-dimensional images taken by time-resolved microtomography using synchrotron radiation. Because of the low absorption contrast between the solid matter of the filter and the suspension, the flow of the cell suspension is observed under phase contrast. The experimental conditions for image acquisition as well as the technique of torsion estimation are described in detail.