Measuring bone density and ratio of new bone formation, by microCT TIFF images

[dbgt]

I am learning to use imageJ and BoneJ, but i need desperately help

I did some experiments in a rabbit mandible by cutting and elevating the cortical bone to create new bone formation, I have now the CT but dont know how to measure the new bone formation.. I just need to measure a specific area, not the whole CT, I understand this is done by ROI, right?

I import the image sequence (TIFF images,) then I select the area i want to measure, then I add it to the ROI, after that I use BoneJ "Volume fraction" option, but it doesnt seem to work,

I get the same results with every area, if I select in the same image sequence another area (to compare to the new bone formation), after applying the "Volume fraction" to this new area, i get the exact same result as the "new bone formation area".

Is this the correct way to measure the bone density and ratio? Could you please give me any suggestion or advice?

Thank you very much, I am really looking forward to your comments.