Introduction

A DEXA scan is a special type of X-ray that measures bone mineral density (BMD).

DEXA stands for "dual energy X-ray absorptiometry".This type of scan may also be called:

• a DXA scan
• a bone density scan
• a bone densitometry scan

DEXA scans are often usedto diagnose or assess someone's risk of Osteoporosis , a conditionthat weakens bones and makes them more likely to break.

As well as being quick and painless, a DEXA scan is more effective than normal X-rays in identifying low bone mineral density.

Osteoporosis

You may need to have aDEXA scan if you're:

• over 50 years of agewith arisk of developing osteoporosis
• under 50 withother risk factors such as smoking or a previous fracture

The World Health Organization (WHO) has created a 10-year Fracture Risk Assessment Tool , which appliesto both men and women between 40 and 90 years of age. The tool can be used to assess if a DEXA scan is appropriate and calculates your risk of fracture in the next 10 years.

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 oestrogen declines, resulting in adecrease in bone mineraldensity (BMD).

Themore denseyour bones, the stronger and less likely they areto fracture (break). Osteoporosis doesn't cause any symptoms until a bone is broken.

It used to be difficult to measure bone density and identifythose at risk of developing osteoporosis until a fracture occurred. However, it's now possible to measure bone density before someone gets a fracture.

Some radiation is absorbedby thebone and soft tissue and some travels through yourbody.

Special detectors in the DEXA scanner measure how much radiation passes throughyour bones, and this information is sent to a computer.

Your bone density measurementswill be compared with the bone density ofa young healthy adult or an adult of your own age, gender and ethnicity.

.

Safety

DEXA scans use a much lower level of radiation than standard X-ray examinations, which means that the radiographer (the technical specialist carrying out the scan) can stayin the scanning room with you during the scan.

The amount of radiation used during a DEXA scan varies depending on the area of the body being examined, but is very low andless thantwo days' exposure to natural background radiation (NBR).

By comparison, a chest X-ray uses the equivalent ofaboutthree days' exposure to NBR, and a flight to North America is equivalent to approximately a week's exposure to NBR.

Despite being very safe procedures, DEXA scans and X-rays aren't recommended for pregnantwomen, as X-rays can damage an unborn child.

.