Comparison of Lumbar Spine Bone Mineral Density Values by Dual-Energy X-Ray Absorptiometry with Quantitative Computed Tomography: Preliminary Results

Purpose: Quantitative computed tomography (QCT) may represent an opportunity for bone mineral density (BMD) screening in patients performing computed tomography (CT) of the abdomen. We retrospectively compared lumbar spine QCT BMD values with BMD by dual-energy X-ray absorptiometry (DXA) using a retrospective asynchronous calibration of QCT scans.

Methods and Materials: We selected 62 subjects that had a CT of the abdomen and a lumbar spine DXA performed during the previous year. CT scans were performed using the Siemens Somatom Definition AS scanner; DXA examinations were performed using Hologic QDR Discovery W densitometer. Volumetric BMD (vBMD) was measured from the lumbar spine using Mindways QCT Pro software with asynchronous calibration. Analysis included the first three lumbar vertebrae. T-score values were used for DXA diagnosis according to World Health Organization criteria. For QCT, American College of Radiology ranges for trabecular spine BMD were used as follows: normal, BMD > 120 mg/cm³; osteopenia, BMD from 120 mg/cm³ to 80^;mg/cm³; and osteoporosis, BMD < 80 mg/cm³.

Results: We studied 56 women and 6 men aged 68 ± 15 years. QCT diagnosis was osteoporosis, 37; osteopenia, 19; and normal status, 6. DXA diagnosis was osteoporosis, 24; osteopenia, 18; and normal status, 20. All subjects classified as osteoporotic at DXA were correctly classified at QCT, except for three individuals in whom QCT showed osteopenic values, still very close to the osteoporosis threshold (vBMD, 82.8, 84.2, and 87.9 mg/cm³, respectively). In four individuals, DXA was normal, but QCT showed vBMD in the range of osteoporosis, due to severe osteoarthrosis producing a fictitious increase of DXA BMD values.

Conclusion: Our results showed that QCT with asynchronous calibration can provide vBMD values comparable with DXA in osteoporotic patients, allowing their opportunistic identification. In addition, QCT permitted the diagnosis of osteoporosis in subjects in whom DXA was limited by osteoarthrosis.

Publication History

Article published online:
17 December 2020