Threshold segmentation not captures the areas I intended

[mina.dehghan (Mina)]

Hello,

I have a cubic shape of Al and Zn (High difference in density). Within the cubic there are some voids that I’m not able to capture them using the threshold segmentation for volume measurements. Is there a way I can make a segmentation selecting the voids all at once other than thresholding? Or is there a more accurate thresholding approach I can use?

Thanks a lot,

Mina