How Is Bone Density Measured?
Bone density can be measured using a simple test called Dual X-Ray Absoptiometry (DXA). DXA machines usually scan bone in the lower spine and one hip, two of the main areas at risk from osteoporotic fractures. The technique uses a radiation dose, which is similar to background radiation, less than one tenth of the dosage for a chest x-ray. It takes 10-20 minutes and is not in any way unpleasant. It involves lying on a firm couch and generally clothes do not need to be removed.
A DXA scan produces a score, which compares your bone density to a reference range of a healthy young adult with average bone density. The difference between this average and your bone density is calculated and expressed in terms of standard deviations (SD) and expressed as a T score. A score of 0 to –1 is normal, -1 to –2,5 is termed osteopenia and below –2.5 is classed as osteoporosis.
Osteopenia is the name for the category between normal and osteoporosis. Lifestyle changes such as a well balanced, calcium rish diet and regular weight bearing exercise should be considered by women with osteopenia.
A score is also calculated to compare your bone density with that of a reference range of people your own age. Although it is not used to diagnose osteoporosis, it is useful to assess the affect of treatment.
