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. The bone mineral density is used to determine if osteopenia or osteoporosis are present.
Radiographic features
Bone mineral density can be measured by various methods, with DEXA being the most prevalent in modern clinical practice:
X-ray
- single-energy x-ray absorptiometry
- dual-energy x-ray absorptiometry (DEXA)
- quantitative computed tomography (QCT)
- radiogrammetry
Ultrasound
- calcaneal ultrasonography: determines bone mineral density and bone strength
- speed of 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 enough yet 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
- MR spectroscopy (MRS)
- quantitative magnetic resonance imaging: depicts changes in the trabecular structures at several sites of the peripheral skeleton
Nuclear medicine
-
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- single-energy photon absorptiometry (SPA) was superseded by the introduction of single x-ray absorptiometry; both methods measure density at peripheral sites in the skeleton (e.g. distal radius, calcaneus), but the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- dual-energy photon absorptiometry (DPA) also has been replaced by dual-energy x-ray absorptiometry (DEXA)
Unable to process the form. Check for errors and try again.