Values are calculated for the lumbar vertebrae and femur preferentially, and if one of those sites is not suitable (e.g. artifact, patient mobility, history of hyperparathyroidism) the forearm can be used 1.
Bone mineral density is calculated in g/cm2, and then compared against two reference population giving two scores 1-3:
T-score: comparison by standard deviation (SD) to a young adult population, matched for sex and ethnicity (used for postmenopausal women and men >50 years)
- ≥-1.0: normal
- <-1.0 to <-2.5: osteopenia
- ≤-2.5: osteoporosis
- ≤-2.5 plus fragility fracture: severe osteoporosis
Z-score: compared by SD to an age, sex, and ethnicity population (used for premenopausal women, men <50 years, and children)
- <-2.0: below expected range, and a cause should be sought
- if automatic segmentation is performed, ensure that it has been performed correctly (i.e. not including ilium on lumbar spine or ischium on hip calculations)
- scores in the lumbar spine can be increased in the setting of degenerative sclerotic change, ankylosing spondylitis, etc.
- 1. Lorente-Ramos R, Azpeitia-Armán J, Muñoz-Hernández A et-al. Dual-energy x-ray absorptiometry in the diagnosis of osteoporosis: a practical guide. AJR Am J Roentgenol. 2011;196 (4): 897-904. doi:10.2214/AJR.10.5416 - Pubmed citation
- 2. El Maghraoui A, Roux C. DXA scanning in clinical practice. QJM. 2008;101 (8): 605-17. doi:10.1093/qjmed/hcn022 - Pubmed citation
- 3. Guglielmi G, Muscarella S, Bazzocchi A. Integrated imaging approach to osteoporosis: state-of-the-art review and update. Radiographics. 2011;31 (5): 1343-64. doi:10.1148/rg.315105712 - Pubmed citation