As you probably know, there are a number of different ways to specify radiation dose. The most widely used quantity is the Sievert Sv. It takes into account the energy deposited by radiation as well as the part of the body irradiated to arrive at a unit that reflects overall potential for harm to cells in the body.

For radiation therapy we want to harm tumor cells and we use doses of the order of several Sv. In diagnostic radiology we use the smallest doses that allow us to make accurate images of the body with x rays. This requires much less radiation, in the range of thousandths of sieverts or millisieverts mSv.

Here are some effective doses associated with DEXA and a few other exams in diagnostic radiology for comparison:. We usually compare radiation doses with "natural background," the radiation we receive by living on Earth, through radioactive isotopes all around us in soil, air, building materials, etc.

We also receive some radiation from cosmic ray sources that exist in the universe, including the star closest to us, the sun. The average annual natural background radiation level in the United States is approximately 3 mSv. No study has ever shown that radiation from natural background sources over an entire lifetime is associated with higher risks of disease or death, anywhere on Earth even though actual background levels in some regions of the planet are five to ten times that of the United States.

It is assumed that any amount of radiation is associated with some risk, but levels associated with many years of natural background seem to have no discernable health effects. So, in terms of natural background in the United States, an abdomen and pelvis CT is about three years' worth of natural background, while the whole-body DEXA is equivalent to about nine hours.

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org Fukushima Information Other Useful Websites. Most women age 65 or older should have a bone density scan. Women in this age group are at high risk for losing bone density, which can lead to fractures.

You may also be at risk for low bone density if you:. There are different ways to measure bone density. The most common and accurate way uses a procedure called dual-energy x-ray absorptiometry, also known as a DEXA scan.

The scan is usually done in a radiologist's office. To measure bone density in the forearm, finger, hand, or foot, a provider may use a portable scanner known as a peripheral DEXA p-DEXA scan.

You may be told to stop taking calcium supplements 24 to 48 hours before your test. Also, you should avoid wearing metal jewelry or clothes with metal parts, such as buttons or buckles. A bone density scan uses very low doses of radiation. It is safe for most people.

But it is not recommended for pregnant woman. Even low doses of radiation could harm an unborn baby. Be sure to tell your provider if you are pregnant or think you may be pregnant. Bone density results are often given in the form of a T score. A T score is a measurement that compares your bone density measurement with the bone density of a healthy year-old.

A low T score means you probably have some bone loss. If your results show you have low bone density, your health care provider will recommend steps to prevent further bone loss. These may include:. Learn more about laboratory tests, reference ranges, and understanding results.

A DEXA scan is the most common way to measure bone density. But your health care provider may order more tests to confirm a diagnosis or to find out if bone loss treatment is working.

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health. Bone Density Scan. What is a bone density scan? What is it used for?

A bone density scan is used to: Diagnose osteopenia low bone mass Diagnose osteoporosis Predict risk of future fractures See if treatment for osteoporosis is working. Why do I need a bone density scan? You may also be at risk for low bone density if you: Have a very low body weight Have had one or more fractures after the age of 50 Have lost a half inch or more in height within one year Are a man over the age of 70 Have a family history of osteoporosis Other risk factors include: Lack of physical activity Smoking cigarettes Heavy drinking Not getting enough calcium and vitamin D in your diet.

What happens during a bone density scan? During a DEXA scan: You will lie on your back on a padded table. You will probably be able to leave your clothes on. You may need to lie with your legs straight, or you may be asked to rest your legs on a padded platform.

A scanning machine will pass over your lower spine and hip. At the same time, another scanning machine called a photon generator will pass beneath you. The images from the two machines will be combined and sent to a computer. A health care provider will view the images on the computer screen.

While the machines are scanning, you will need to stay very still. You may be asked to hold your breath. Will I need to do anything to prepare for the test?

Are there any risks to the test? What do the results mean? Your results may show one of the following: A T score of

This ensures that the areas of your body not being imaged receive minimal radiation exposure. Please type your comment or suggestion into the text box below.

Note: we are unable to answer specific questions or offer individual medical advice or opinions. org is not a medical facility.

Please contact your physician with specific medical questions or for a referral to a radiologist or other physician. To locate a medical imaging or radiation oncology provider in your community, you can search the ACR-accredited facilities database.

This website does not provide cost information. The costs for specific medical imaging tests, treatments and procedures may vary by geographic region. Web page review process: This Web page is reviewed regularly by a physician with expertise in the medical area presented and is further reviewed by committees from the Radiological Society of North America RSNA and the American College of Radiology ACR , comprising physicians with expertise in several radiologic areas.

Outside links: For the convenience of our users, RadiologyInfo. org provides links to relevant websites. org , RSNA and ACR are not responsible for the content contained on the web pages found at these links.

Toggle navigation. What is a bone density Scan? What are some common uses of the procedure? How should I prepare? What does the equipment look like? How does the procedure work? How is the procedure performed? What will I experience during and after the procedure?

Who interprets the results and how will I get them? What are the benefits vs. What are the limitations of a bone density scan?

Bone density testing is strongly recommended if you: are a post-menopausal woman and not taking estrogen. have a personal or maternal history of hip fracture or smoking. are a post-menopausal woman who is tall over 5 feet 7 inches or thin less than pounds.

are a man with clinical conditions associated with bone loss, such as rheumatoid arthritis, chronic kidney or liver disease. use medications that are known to cause bone loss, including corticosteroids such as Prednisone, various anti-seizure medications such as Dilantin and certain barbiturates, or high-dose thyroid replacement drugs.

have type 1 formerly called juvenile or insulin-dependent diabetes, liver disease, kidney disease or a family history of osteoporosis. have high bone turnover, which shows up in the form of excessive collagen in urine samples.

have a thyroid condition, such as hyperthyroidism. have a parathyroid condition, such as hyperparathyroidism. have experienced a fracture after only mild trauma.

have had x-ray evidence of vertebral fracture or other signs of osteoporosis. The Vertebral Fracture Assessment VFA , a low-dose x-ray examination of the spine to screen for vertebral fractures that is performed on the DXA machine, may be recommended for older patients, especially if: they have lost more than an inch of height.

have unexplained back pain. if a DXA scan gives borderline readings. the DXA images of the spine suggest a vertebral deformity or fracture. There are two types of DXA equipment: a central device and a peripheral device.

Your doctor will likely do this exam on an outpatient basis. The VFA test adds only a few minutes to the DXA procedure. Bone density tests are a quick and painless procedure.

A clinician should review your DXA scan while assessing the presence of clinical risk factors such as: rheumatoid arthritis chronic renal and liver disease respiratory disease inflammatory bowel disease 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.

Benefits DXA bone densitometry is a simple, quick and noninvasive procedure. No anesthesia is required. The amount of radiation used is extremely small—less than one-tenth the dose of a standard chest x-ray, and less than a day's exposure to natural radiation.

DXA bone density testing is currently the best standardized method available to diagnose osteoporosis and is also considered an accurate estimator of fracture risk. DXA is used to make a decision whether treatment is required and it can be used to monitor the effects of the treatment.

DXA equipment is widely available making DXA bone densitometry testing convenient for patients and physicians alike. No radiation stays in your body after an x-ray exam. X-rays usually have no side effects in the typical diagnostic range for this exam.

Risks There is always a slight chance of cancer from excessive exposure to radiation. However, given the small amount of radiation used in medical imaging, the benefit of an accurate diagnosis far outweighs the associated risk. label }}. Why a bone density scan is done. How a bone density scan is done.

You can eat normally but should not take calcium supplements for 24 hours before the test. Side effects. What the results mean. What happens if the results are abnormal. Special considerations for children. References American Society of Clinical Oncology.

British Columbia Ministry of Health. Bone Density. Bone Health. Fischbach FT, Fischbach MA. Fischbach's A Manual of Laboratory and Diagnostic Tests. Wolters Kluwer; Papaioannou A, Morin S, Cheung AM, et al. Radiological Society of North America.

Bone Densitometry DEXA. Siminoski, K. Recommendations for Bone Mineral Density Reporting in Canada. Canadian Association of Radiologists Journal. Ottawa: Canadian Medical Association; Quick Links HPS Website Home Feedback Forgot My Password Members Only Search hps.

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