Bone changes in oophorectomized monkeys: CT findings.

Single and dual energy CT (75 and 125 kVp) measurements of density were made on the excised lumbar vertebrae (L5) of oophorectomized (n = 17) and control (n = 19) monkeys. The single-energy results at 75 and 125 kVp indicated an annual bone diminution of 9.1 and 10.9%, respectively, but the dual-energy determination showed only a 6.6%/year loss. The difference between single- and dual-energy results could be explained by a putative increase in marrow fat of slightly greater than 100 mg/cm3. Changes in single-energy CT density with oophorectomy and aging may be substantially overestimated.