DEXA scan (bone density scan): who is it for and what happens?

In 2019, an estimated 681,000 people in Belgium had osteoporosis, or bone thinning. Worldwide, 1 in 3 women and 1 in 5 men over the age of 50 will break a bone because of osteoporosis at some point. The insidious part is that osteoporosis usually causes no pain until a bone breaks. A DEXA scan, also called a bone density scan, measures how strong your bones are.

What is a DEXA scan?

DEXA stands for dual-energy X-ray absorptiometry. The machine uses X-rays at two different energies: one is absorbed mainly by the soft tissues, the other mainly by the bone. This is how the computer calculates your bone density. The measurement is usually taken at the lower back and the hip. A DEXA scan is the standard method for measuring bone density and diagnosing osteoporosis.

Who is a bone density scan useful for?

Your GP (family doctor) or specialist assesses whether a bone density scan is useful for you. International guidelines recommend a scan for, among others:

• women aged 65 and over and men aged 70 and over;
• women after the menopause who are younger than 65 and men younger than 70, if they have risk factors, such as low body weight, a previous fracture, or a condition or medication that causes bone loss;
• adults who broke a bone in a minor fall or a light knock;
• anyone who is receiving or will receive treatment for osteoporosis, to monitor its effect.

Is a bone density scan reimbursed?

In Belgium, the health insurance fund contributes to the cost of a DEXA scan if you belong to one of these groups. Age alone is not enough.

• Women over 65 with a first- or second-degree relative, for example a parent, brother or sister, who had a hip fracture.
• Men and women of any age with at least one of these risk factors:
  • a vertebral fracture without a heavy impact that is not caused by cancer, or another fracture after a minor fall or knock (fractures of the fingers, toes, skull, face or neck do not count);
  • a prescribed treatment with cortisone for more than three consecutive months, at a dose of more than 7.5 mg prednisolone per day or an equivalent dose;
  • anti-hormonal treatment for cancer, or a menopause caused by cancer treatment;
  • one of these conditions: rheumatoid arthritis, an active, untreated overactive thyroid, a prolactin level that is too high, a long-term shortage of sex hormones, too much calcium in the urine due to a kidney problem, an overactive parathyroid gland, brittle bone disease (osteogenesis imperfecta), Cushing's disease or syndrome, anorexia nervosa with a BMI below 19, or a menopause before the age of 45.

A new reimbursed scan is possible after five years at the earliest, and only if you still belong to one of these groups at that time. Your GP or specialist can prescribe the examination. If you are unsure whether you qualify, ask your doctor.

How do you prepare?

• No special preparation: you can eat and drink as normal.
• Clothing: preferably wear clothes without metal, such as zips, buckles or buttons.
• Pregnant? If you are or could be pregnant, let us know in advance: a DEXA scan is not recommended during pregnancy.
• What to bring: your doctor's prescription and your identity card.

What happens during the scan?

You lie on your back on an open examination table. There is no tunnel and you do not get an injection. A measuring arm moves slowly above you, without touching you. It is important that you lie still for a moment. The measurement itself takes a few minutes; allow about a quarter of an hour for the whole examination. The examination does not hurt.

What about radiation?

A DEXA scan uses a very low dose of X-rays: about as much as you naturally receive from your surroundings in one to a few days.

What does the result mean?

The computer compares your bone density with reference values. The report contains two figures:

• The T-score compares your bone density with that of young, healthy adults. For women after the menopause and for men aged 50 and over: a T-score of -1 or higher is normal. If the score is between -1 and -2.5, this is called osteopenia, a reduced bone density. A T-score of -2.5 or lower indicates osteoporosis.
• The Z-score compares your bone density with that of people of your age and the same sex. For women before the menopause and for men under 50, this is the most important score.

Where possible, the radiologist also uses your measurement and the information from your referring doctor (such as age, weight, previous fractures and smoking) to calculate your risk of a fracture in the next ten years: the FRAX score. Whether this is possible depends, among other things, on your T-score. The radiologist writes a report for your referring doctor, who discusses the result with you. You also receive a code with which you can view your images and report online; how this works is explained on the Results page.

Where can you go?

Radiologie Antwerpen has its own DEXA machine at AZ Monica Campus Deurne, Florent Pauwelslei 1, 2100 Deurne. A bone density scan is done by appointment: call us on +32 3 320 57 70, on working days from 8 a.m. to 6 p.m.. More practical information can be found on our BMD / DEXA scan page.

Dr Cedric Bohyn, radiologist at Radiologie Antwerpen