(a) Estimated mean pressure value (left) and the corresponding standard error (right) of an exemplary U87 spheroid, 3 h after the experiment started, as a function of the window size and the signal-to-noise threshold used in the PIV-analysis. (b) Mean estimated pressure as a function of the window size, for a signal-to-noise threshold of 1.0, that is without any filtering of the estimated deformations. (c) The 99th percentile of all measured absolute displacements during the first two hours of the experiment, , for all individual spheroids. The dashed red line represents the upper boundary of for a window size of 40 px, according to the one-quarter-rule. The dot-dashed line and the dotted line correspond to the upper boundary for a window size of 30 px and 50 px, respectively.