DEXA bone density study of multiple sites of axial skeleton
A DEXA scan, also known as a bone densitometry exam, is an imaging test that determines bone strength by measuring the mineral content of the bones. The results can tell if you are at risk of brittle bones (osteoporosis) or fractures. DEXA stands for Dual-Energy X-ray Absorptiometry and uses two different types of low-dose X-ray beams to measure bone health at multiple sites of your skeleton. The most common regions to scan are the hip, spine, heels, and forearm, but any body bone can be used, like fingers, wrists, toes, etc. It is a simple, non-invasive, and painless procedure that can also provide information about body composition related to body fat and muscle mass.
Why and when do you need this test?
This scan is usually done to determine the condition of your bones if you have risk factors that can predispose you to weak bones, for example, old age, menopause, excessive smoking or drinking, chronic medical illnesses, etc. It is recommended once in two years for people with risk factors. By evaluating your condition, you might be advised to change your lifestyle habits and add some complementary medicines to improve your bone health to mitigate your risk of fractures. You may need to undergo this test for any of the following reasons;
- Advanced age, for men over 70, for women over 65
- Excessive use of alcohol or smoking
- Lack of physical activity and bone pains
- Loss of more than an inch in height, pointing toward vertebral fractures
- Personal or family history of osteoporosis or fractures on minimal trauma
- A condition affecting the thyroid gland (hyperthyroidism)
- A condition affecting the parathyroid gland (hyperparathyroidism)
- Evidence of fracture or osteoporosis on X-ray
- Suffering from chronic medical diseases like rheumatoid arthritis, kidney disease, type 2 diabetes, liver disease, SLE, etc.
- Use of medicines that can affect bone health, like steroids, immunosuppressive drugs, chemotherapy, etc.
- Monitoring of your treatment for osteoporosis
Do you need to prepare for the test?
DXA scan requires the following preparation.
- Stay well hydrated and eat and take medicines normally unless mentioned otherwise by your doctor.
- Avoid taking calcium supplements 24 hours before the test
- Inform your doctor If you have recently had a contrast test (CT scan, MRI, etc.), as you may have to wait for 3-7 days for DXA in this case.
- You should not be wearing any metallic object, be it jewelry, a watch, or metallic zippers or buttons, as they can come in the way of X-rays and affect the results.
- Patients with prosthetic hip or metallic implants may need to inform their doctor.
- As the process uses X-rays, please inform your doctor if you are pregnant.
What can you expect?
- After entering the designated room, you will be asked to lie down on the table.
- The machine consists of a central part and an arm attached to it.
- Your hip joint or other desired places may be fixed using foams etc.
- The moveable arm will move over your body several times to generate images on the attached computer.
- The scan will take 25 minutes
- You may need to lie down still to prevent the images from getting blurry.
- You may return to your normal activities shortly after the test.
Are there any risks to this test?
This test uses a very low dose of radiation that are generally safe. However, it can harm a developing fetus, so it is unsafe for pregnant women.
What do the test results mean?
After the test, a signed report will be sent to your doctor by the radiologist. Your doctor would be able to guide you about your results. If the results show that you have osteoporosis and increased fracture chances, then your doctor will advise you to change your lifestyle and take medicines that can help you prevent fractures.
The DEXA scan results include two scores, a T-score and a Z-score.
The T-score compares your bone density with that of an adult who is younger than you. The difference is given in SD, standard deviation. Above minus 1 SD is considered normal, between minus 1 and 2.5 SD is minimally decreased bone density, and below minus 2.5 is confirmed osteoporosis.
The Z-score compares your bone density with a person of your age. A score of less than minus 2 warrants the need for more medical tests to rule out osteoporosis.
- Blood tests for calcium, magnesium, vitamin D
- computed X-ray tomography (CT) scan