What is a bone density scan?
A bone density scan (DEXA scan) is an imaging test using minimal radiation to measure the calcium content of the bone or, perhaps more correctly, to measure reduced bone strength.

How does it work and why is it done?
Bone density scanning, also called dual-energy x-ray absorptiometry (DEXA), or bone densitometry, is an enhanced form of x-ray technology used to measure bone loss, or osteoporosis. It employs a DEXA scanner, uses a minimal radiation dose, and produces a report giving readings of bone density in relation to the average for a person of your size and weight.

What is osteoporosis?

Osteoporosis is a silent condition of bone loss without symptoms until a fracture occurs, affects both women and men, and can be effectively treated.

Osteoporosis is the weakening of bone, which may result in increased fracture risk. It affects both men and women. For some women this may be rapid and severe.

The consequences of osteoporosis include pain, disability, deformity and lost independence. The key to the treatment of osteoporosis is to measure your bone strength before you have a broken bone. As soon as you know you have lost some bone strength or "density", you and your doctor can discuss how you can minimise any further weakening.

A bone density test can:

• detect low bone density before a fracture occurs
• confirm a diagnosis of osteoporosis
• determine your rate of bone density change, if you have serial studies
• monitor the effect of any treatment you are having for osteoporosis.

			Pre Examination
	Please phone us to make an appointment for your scan. If you have a referral from your doctor please bring this with you. You are able to self refer for this test if you wish but we recoomend you send a copy of your report to your doctor to enable it to be added to your medical file..

			The Examination
	Please wear clothing without buckles, buttons or zips. When you have your bone density scan, you will be asked to lie on a table.The scan takes about 20 to 30 minutes, during which you will hear quiet machine noise, and a scanning arm will move above you, but it will not touch you. The technician will tell you when the scan is finished.

			Post Examination
	A report is generated by the radiologist, endocrinologist or rheumatologist and sent to your doctor.

Osteoporosis
Bones change throughout your life. After teenagers stop growing, bone density increases in the average person until around the age of 30 years. At this time, bone density may plateau, or bone loss will start to occur at around 1% per year. Osteoporosis occurs when not enough new bone is formed or when too much bone is lost. Accelerated bone loss may occur due to a number of lifestyle or physical factors - see below.

For women, the decrease in oestrogen production at menopause results in bone loss, which for some may be rapid and severe. Women tend to suffer more from osteoporosis than men for a variety of reasons, including the fact they usually have smaller, thinner frames than men and they go through menopause. Other factors such as diet, lack of exercise, smoking and alcohol intake contribute to bone fragility in both sexes.

Osteoporosis risk factors
In New Zealand osteoporosis is a majot health issue. It is estimated that 50 per cent of women and 29 per cent of menwill suffer a fracture caused by osteoporosis. Risk factors are helpful when identifying people more likely to develop osteoporosis, but the only way to know your bone density is to have it measured. Risk factors that increase your chances of developing osteoporosis are:

• being female
• a small, thin frame
• advancing age
• a family history of osteoporosis
• early menopause
• abnormal absence of periods (amenorrhea)
• anorexia nervosa or bulimia
• a diet low in calcium
• use of certain medications, (eg, steroids, anticonvulsants, thyroxine)
• low testosterone levels in men
• a sedentary lifestyle
• cigarette smoking
• excessive alcohol intake
• malabsorption problems.

What if I find out if I have osteoporosis?
There are treatment plans available that can slow the loss of bone density, and make bone fractures caused by osteoporosis less likely.

For both men and women already suffering from osteoporosis, doctors may prescribe medications. In addition, a calcium-rich diet, vitamin D, exercise and a healthy lifestyle are part of the osteoporosis treatment programme your doctor will discuss with you.

The image above is an example of a bone density scan for a hip. The measurement of bone density is shown by indicating with the small square on marked areas of the graph.