Spindle Pole Position Refinement

The spindle pole refinement algorithm takes initial (x,y,z) spindle pole predictions as an input. The spindle boundary coordinates are obtained by taking the maximum projection of the spindle mask. Then, 3D coordinates are extracted along the spindle length axis (pole-to-pole axis) to obtain the corresponding pixel values. The true spindle pole is defined as the first and last occurrence of positive values in the resulting 1D array. Finally, the new position of spindle poles was updated across all data frames for further calculations (Table 1). Manual analysis used for evaluating the performance of SpinX’s pole position recording was performed on Fiji (ImageJ) software (Schindelin et al., 2012 (link)).