Bone density is simply the amount of bone tissue in a certain volume of bone. A bone density test is used to assess the strength of bones and the possibility of fracture in those who are at risk of osteoporosis. Bone density testing is also referred to as bone densitometry, a bone mineral density (BMD) scan or a dual energy X-ray absorption (DEXA) scan.
Measurements are most commonly made over the lumbar spine and the upper part of the hip. The forearm may be scanned if the hip and lumbar spine are not accessible. The bone density scan requires only about one-tenth of the radiation of a regular X-ray. It is a painless and noninvasive procedure performed by a radiologist that takes only a few minutes.
Women and Bone Density
In premenopausal women, estrogen produced in the body maintains bone density. Following the onset of menopause, bone loss increases each year and can result in total loss of 25%–30% of bone density in the first five to 10 years after menopause. In general, BMD testing is recommended for women age 65 and older and men age 70 and older.
Indications for BMD testing are also recommended in women under the age of 65 and men under the age of 70 who have clinical risk factors for fracture, including low body weight, prior fracture or high-risk medication use.
Osteoporosis means “porous bone.” If you look at healthy bone under a microscope, you will see that parts of it look like a honeycomb. If you have osteoporosis, the holes and spaces in the honeycomb are much bigger than in healthy bone. This means your bones have lost density or mass. It also means that the structure of your bone tissue has become abnormal. As your bones become less dense, they become weaker.
How Is the Procedure Performed?
BMD testing is used to evaluate your bone mass for osteoporosis. The test is performed while you are lying still on a table. A scanner will pass over your body, taking painless X-rays of your lower spine and hip. You will not need to remove your clothes, but be sure not to wear clothing with metal snaps, zippers or buttons.
Download the bone densitometry prep manual for complete preparation instructions.
T-scores and Z-scores
The results of your test are usually reported as a T-score and Z-score. The T-score compares your bone density to that of a healthy 30-year-old adult, the stage at which the average adult has his/her greatest bone density. The Z-score compares your bone density to the average value for other individuals sharing your age range, gender and ethnicity. In either score, a negative number means that you have thinner bones than the standard, which may predict future breaks or the chance of osteoporosis.
|Normal||T-score or Z-score of -1 or above|
|Osteopenia||T-score or Z-score lower than -1 and greater than -2.5|
|Osteoporosis||T-score or Z-score of -2.5 or lower|
Source: World Health Organization (WHO) Classification
Bone density testing can detect osteoporosis at its earliest stages so treatment can begin sooner. If you are already being tested for osteoporosis, bone density testing will assist your health care provider in monitoring your response to the treatment.
Gwinnett Medical Center Imaging has multiple convenient Atlanta-area locations in Lawrenceville, Hamilton Mill and Duluth. If you would like to schedule an appointment, please call 678-312-3444. To schedule your bone density exam, you must first obtain an order from your physician.