What is a bone density scan?
A bone density scan, also called dual energy X-ray absorptiometry or DEXA, uses X-ray equipment and a computer to measure bone loss. DEXA scans can help look for signs of fragile bones (osteoporosis) and help assess your risk of developing fractures. DEXA scans are also often used to monitor the effects of treatment for osteoporosis.
The procedure is quick and painless. It involves exposing your body to a small dose of ionising radiation (X-rays). The X-rays travel through your bones, usually the hip and lower spine, where they are absorbed at different levels depending on how dense the bones are. When the X-rays come out on the other side they are picked up by a detector. The detector measures the amount of X-rays passing through your bones and sends the information to a computer. The computer calculates a score of the average density of the bone. A low score indicates the bone is fragile and therefore more likely to fracture.
A woman may be advised to have a DEXA scan if she:
- has broken a bone after a minor bump or fall
- has family history of hip fracture on her mother’s side
- has a history of periods stopping for more than one year before the menopause
- has taken steroid tablets for three months or more
- is under 45 and has had a hysterectomy or early menopause
- is underweight
A man may be advised to have a DEXA scan if he has:
- low levels of testosterone
- a medical condition that is associated with osteoporosis such as rheumatoid arthritis or coeliac disease
- taken steroid tablets for three months or more
DEXA scans are routinely done as an out-patient procedure in the imaging or radiology department. The scan usually takes 10 to 15 minutes. It can take several minutes to scan each bone, and it’s important to lie very still.
DEXA scans are commonly performed and generally safe. You will be exposed to some X-ray radiation. Although the radiation dose being used is generally thought to be safe for adults, it may harm a developing fetus. Therefore, X-rays are not usually done on pregnant women unless there is an urgent medical reason. If you think you could be pregnant, please tell your doctor before your appointment day.
Your doctor will explain the benefits and risks of having a DEXA scan and will also discuss alternatives to the procedure.