Reconstruction of the barium grains in a three-dimensional volume. (a) Iterative reconstruction (low-pass filtered) of a single frame as shown in Fig. 6. (b) Binary image using a threshold of −0.22 rad. Black regions indicate phases smaller than the threshold value. The three largest connected components in the binary image are tracked in all frames. (c, d) Tracked y- and z- position of the barium grains throughout the scan. Note that all frames are shown in Fig. 6 and used for iterative reconstruction of the three-dimensional volume. (e) Volume rendering of the reconstructed 3D phase. Reconstruction was achieved using 50 iterations of the SIRT algorithm implemented in the ASTRA toolbox. Prior to reconstruction, the data had been corrected for shifts along the y-axis and the rotation axis was placed manually into the center of rotation. Markers are used to indicate identical barium grains. Scale bar: 2.5 µm.