DEXA Scan: Bone Density Testing Explained

DEXA (Dual-Energy X-ray Absorptiometry) is a specialised scan that measures bone mineral density (BMD). It's the gold standard test for diagnosing osteoporosis - a condition where bones become weak and brittle, increasing the risk of fractures.

DEXA uses two low-dose X-ray beams at different energy levels. The difference in absorption between bone and soft tissue allows the machine to calculate your bone density with high precision. The radiation dose is extremely low - about one-tenth of a standard chest X-ray.

Your doctor may recommend a DEXA scan if you:

• Are a woman aged 65+ or a man aged 70+ (routine screening) • Are postmenopausal and have risk factors for osteoporosis • Have had a fragility fracture (a fracture from minimal trauma) • Take medications that affect bone density (e.g., long-term corticosteroids) • Have conditions that affect bone health - rheumatoid arthritis, coeliac disease, thyroid disorders • Have a family history of osteoporosis or hip fracture • Are underweight (BMI < 20) • Are a smoker or heavy alcohol consumer

Early detection of low bone density allows treatment to begin before a fracture occurs.

DEXA scans require very little preparation:

• Wear comfortable clothing without metal zippers, buttons, or buckles. You may be given a gown. • Don't take calcium supplements for 24 hours before the scan • Tell the clinic if you've had a barium study or contrast CT in the past 7 days - residual contrast can affect results • Tell the clinic if you might be pregnant • No fasting required

Bring any previous DEXA results if you have them - comparison with earlier scans helps track changes in your bone density over time.

A DEXA scan is quick and painless - it typically takes 10 to 20 minutes.

You'll lie on your back on a padded table. The scanner arm passes over your body, usually measuring the lower spine and one or both hips - these are the sites most commonly affected by osteoporosis.

You won't feel anything during the scan. There's no tunnel or enclosed space. You just need to stay still while the measurements are taken.

Some clinics also offer whole-body DEXA for body composition analysis (measuring fat, muscle, and bone mass), which is popular with athletes and people tracking fitness goals.

Your DEXA results include a T-score, which compares your bone density to that of a healthy 30-year-old:

• T-score of -1.0 or above: Normal bone density • T-score between -1.0 and -2.5: Osteopenia (lower than normal bone density - increased fracture risk) • T-score of -2.5 or below: Osteoporosis (significantly low bone density - high fracture risk)

Your doctor will interpret your results along with your other risk factors to decide whether treatment is needed. Treatments may include calcium and vitamin D supplements, weight-bearing exercise, and in some cases, medication to strengthen bones.

• Medicare-covered (eligible patients): $0-$30 out-of-pocket. Medicare covers DEXA scans for patients meeting specific criteria - generally those over 70, people with a previous fracture, or those on bone-affecting medications. • Without Medicare eligibility: $80-$200 • Body composition DEXA: $50-$150 (usually not Medicare-covered)

Medicare eligibility for DEXA scans has specific criteria. Your GP can determine whether your scan qualifies for a rebate - see our full bone density scan cost and Medicare eligibility guide for the criteria and rebate intervals.