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Dual Energy XRAY Absorptiometry

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Dual Energy XRAY Absorptiometry, DEXA Scan, DEXA

  • See Also
  1. Osteoporosis
  2. Bone Mineral Density
  1. See Bone Mineral Density
  2. Gold standard Osteoporosis Screening and monitoring
  • Protocol
  • Sites for measuring bone mass
  1. Lumbar Vertebrae
    1. Assess risk of Vertebral Compression Fractures
    2. Screening younger patients without Osteoarthritis
  2. Femoral Neck
    1. Assess risk of Hip Fractures
    2. Screening older patients with Osteoarthritis
  3. Other locations
    1. Wrist (Distal Radius)
    2. Calcaneus
  4. References
    1. Cummings (1993) Lancet 341:72 [PubMed]
    2. Marshall (1996) BMJ 312:1254 [PubMed]
  • Advantages
  1. Negligible radiation
  2. Accurate, reproducible predictor osteoporotic Fracture
  3. Excellent measure of treatment response
  • Disadvantages
  1. Moderate cost
  2. Osteoarthritis interferes with Spine DEXA Scan reading
    1. False elevated BMD on PA Spine views in elderly
    2. In elderly, use hip or lateral spine views
  • Scoring
  1. See Bone Mineral Density (T-Score and Z-Score)
  1. Recheck DEXA Scan
    1. Normal or only mild Osteopenia of femoral neck: Recheck DEXA in 15 years
    2. Moderate Osteopenia: Recheck DEXA in 5 years
    3. Severe Osteopenia: Recheck DEXA Scan in 1 year
    4. Osteoporosis: Recheck DEXA every 2 years or less
    5. Gourlay (2012) N Engl J Med 366(3): 225-33 [PubMed]
  2. Monitoring for change
    1. Use absolute value in grams per cm^2 from now and prior DEXA Scan (not the T-Score)
    2. Use Least Significant Change defined for the particular scanner used
      1. Calculate the difference in absolute values (g/cm^2) between now and prior DEXA Scan
      2. Significant difference if change in absolute value exceeds Least Significant Change
  • References
  1. Blake (1998) Endocrinol Metab Clin North Am 27:267-88 [PubMed]
  2. Bracker (1998) Postgrad Med 104(4):77-86 [PubMed]
  3. Genant (1998) Radiographics 18:913-8 [PubMed]