we do quite frequently such measurements, but I can’t unfortunately comment on how to do that in ImageJ (hopefully someone can add that later, I wish to see that myself ).
The general strategy is the following:
- use any suitable method to segment the object of interest
- count the number of voxels that form the segmented object (= N)
- multiply this number by the physical size (in um) of voxels (= N * x * y * z)
Alternative solution is to use the the segmented model (step 1) to generate a triangular surface of the object and measure the volume occupied by that surface (many programs that can generate the surface are also capable of doing such calculation). The surfaces are used for visualization but as additional benefit can also be measured.