Used to measure bone loss, bone density scanning - also called dual-energy X-ray absorptiometry (DEXA) or bone densitometry – is an enhanced form of X-ray technology. DEXA is the standard for measuring bone mineral density. Scans are most often performed on the lower spine and hip; in children and some adults, the whole body is scanned.
You should not take calcium supplements for at least 24 hours before your exam. The patient is fully clothed for the exam. Wear loose, comfortable clothing and avoid zippers, belts or buttons or any other objects made of metal that may interfere with the X-ray images.
Bones are solid, yet resilient; changing in density and dimension and continually renewing themselves throughout our lives. But bones can become thinner, more fragile and more likely to break. They can weaken from disease, smoking, lack of exercise, nutritional deficiencies, estrogen deficiency in women and low testosterone levels in men, medication, age and other causes.
Scans measure the density of the bones and can be use to:
- assess an individual’s risk of developing fractures
- assist in diagnosing osteoporosis
- track the effects of treatment for osteoporosis and other conditions that cause bone density loss
The bone density scan machine sends a thin beam of low-dose X-rays with two distinct energy peaks through the bones being examined. One peak is absorbed mainly by soft tissue and the other by bone. The soft tissue amount can be subtracted from the total and what remains is a patient’s bone mineral density.
A radiologist will analyze the images and send a signed report to your primary care or referring physician, who will discuss the results with you. Your test results will be in the form of two scores:
T score – This number shows the amount of bone you have compared with a young adult of the same gender with peak bone mass. The t score is used to estimate your risk of developing a fracture.
Z score – This number reflects the amount of bone you have compared with other people in your age group and of the same size and gender. If this score is unusually high or low, it may indicate a need for further medical tests.