A DEXA scan is a special type of X-ray that measures bone density. DEXA stands for dual energy X-ray absorptiometry.
DEXA scans, also known as DXA scans, bone density scans or bone densitometry scans are most commonly used to diagnose osteoporosis (where the bones become weak and fragile and more likely to break). They can also be used to assess the risk of osteoporosis developing.
A DEXA bone scan can also help detect other bone-related conditions, such as osteopenia (very low bone mineral density) and osteomalacia (softening of the bones caused by a vitamin D deficiency). In children, osteomalacia is known as rickets.
You may need to have a DEXA scan if you are at risk of developing osteoporosis.
Osteoporosis can affect people of both sexes and all ages, although older, post-menopausal women are particularly at risk. This is because after the menopause the level of the hormone oestrogen falls, resulting in a decrease in bone density.
The denser your bones, the stronger and less likely they are to fracture (break). Osteoporosis does not cause any symptoms until a bone is broken.
In the past it was difficult to measure bone density and identify those at risk of developing osteoporosis, until a fracture occurred.
However, by using bone densitometry techniques, such as bone density scans, it is now possible to measure bone density before fractures occur.
When should I go for a DEXA scan?
A DEXA scan may be recommended if you have an increased risk of developing a bone condition such as osteoporosis. Your risk is increased if you:
- have had a fracture after a minor fall or injury
- are a woman who has experienced an early menopause
- are a post-menopausal woman
- are a man or a woman with a condition that leads to low bone density, such as rheumatoid arthritis (pain and swelling in the joints)
Measuring bone density
During a DEXA scan, X-rays will be passed through your body. Some radiation will be absorbed by the bone and soft tissue, and some will travel through your body.
Special detectors in the DEXA scanner measure how much radiation passes through your bones and this information is sent to a computer.
The measurements will be compared to the normal range for bone density in a healthy adult and someone of the same gender and ethnicity.