An instance or labels segmentation was then carried out. This separated the particles in the image and assigned a unique 16-bit label to each particle instance. In this case it was critical that the same label was assigned to corresponding particles in each tomogram so that they could be tracked across different SoC. Instance segmentation of particles was performed using the watershed segmentation method from scikit-image on a smoothed distance map of the binary segmentation. A set of seeds were created at the centre of each particle with the 16-bit label value assigned to each particle being assigned to its corresponding seed. These seeds were then used to label the particle instances in the succeeding tomogram, thereby enforcing the same labels across all the tomograms (at different SoC). This method relied on good registration between tomograms and minimal particle movement.