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Bone mineral density

Dr Henry Knipe and Dr Ayush Goel et al.

Bone mineral density (BMD) is defined as the amount of mineral (calcium hydroxyapatite) per unit of bone and can be used as an indirect indicator of bone strength. 

Radiographic features

BMD can be measured by various methods with DEXA the most prevalent:

  • gamma rays (gamma decay): replaced by radiographic methods
    • single-energy photon absorptiometry (SPA) was superseded by the introduction of single x-ray absorptiometry; both methods measure density at peripheral sites in the skeleton (e.g. distal radius, calcaneus), but the disadvantage is that it cannot measure trabecular and cortical bone separately
    • dual-energy photon absorptiometry (DPA) also has been replaced by dual-energy x-ray absorptiometry (DEXA)
  • x-ray
  • ultrasound
    • calcaneal ultrasonography: determines bone mineral density and bone strength
    • speed sound (SOS): measures velocity in the bone
    • broadband ultrasound attenuation (BUA): measures the frequency in the bone
  • CT
    • advantageous for opportunistic screening but research not advanced for implementation into clinical practice 4
    • HU measurements vary on anatomic site including by individual vertebra 4
    • scanner variability is also a significant factor with HU threshold for diagnosis of osteoporosis varying between 99 and 136 HU 4
  • MRI
    • spectroscopy
    • quantitative magnetic resonance imaging: depicts changes in the trabecular structures at several sites of the peripheral skeleton

Article information

rID: 31432
Section: Gamuts
Synonyms or Alternate Spellings:
  • Bone mineral density (BMD)
  • BMD

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Cases and figures

  • Case 1: DEXA showing osteopaenia
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