Bone mass density scan can determine bone density. Computed scan equipment useslow dose of radiation to test the bone density of hips and spine. The test takes about 15 – 20 minutes and is easy to operate. The results are often used to estimate the risks of having osteoporosis for males and females.

Healthy bones must meet the balance of producing new bones and absorbing old bones. Age of 30 is the peak of bone mass density and starts to decline afterwards.

If the production of new bone is too slow (such as insufficient calcium, calcium malabsorption) or the absorption of old bone is too fast (such as degeneration), bone mass density will continue to decline, making bones fragile with higher risk  of bone fracture, which is the so-called osteoporosis.

Examination Methods

There are two common methods for testing bone mass density. One is quantitative ultrasound (QUS) that measures the bone mass density in ankle, wrist, or finger. The other method is using low dose bone densitometry (DEXA) X-ray for spine or femur.

The former, suitable for primary screening, is a small portable device without radiation and may be done in no time. The latter requires patients to make an appointment with Radiology Department at the hospital. Patients lie on a soft mat and a particular body part, such as spine and hip, will be scanned. It takes 15-20 minutes for accurate measurement of bone mass density.

Normal Value Range

T score is interpreted based on the guidelines proposed by WHO and US Osteoporosis Foundation:

• When the difference of T score and mean is within 1 standard deviation (+1.0 - -1.0), the bone mass density is normal.
• When T score is below mean and standard deviation is between -1.0 – 2.5, the bone mass density is too low. Osteopenia occurs.
• When T score is below mean and standard deviation is below -2.5, osteoporosis occurs.
• When T score is below mean and standard deviation is below -2.5 with one fracture incident, severe osteoporosis occurs.