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StatPearls [Internet]. Treasure Island FL : StatPearls Publishing; Jan-. Show details Treasure Island FL : StatPearls Publishing ; Jan-. Search term. Dual-Energy X-Ray Absorptiometry Marissa Krugh ; Michelle D.

Author Information and Affiliations Authors Marissa Krugh 1 ; Michelle D. Affiliations 1 Campbell University. Continuing Education Activity Dual-energy x-ray absorptiometry DEXA has sustained a niche for measuring bone mineral density since its approval by the Food and Drug Administration FDA for clinical use in Introduction Dual-energy x-ray absorptiometry DEXA has sustained a niche for measuring bone mineral density since its approval by the Food and Drug Administration FDA for clinical use in Anatomy and Physiology Lumbar Spine To flatten the lordosis of the lumbar spine, the patient lays supine with their hips and knees flexed on a supportive cushion.

Hip The long axis of the femoral diaphysis is aligned with the scanner as the patient lies supine and a positioning device that internally rotates the femur to elongate the femoral neck on the PA image. Whole Body The patient is placed supine on the table with arms pronated and feet in dorsiflexion.

Choosing Site to Scan Two sites are routinely evaluated with DEXA: the lumbar spine and hip. Indications All women 65 years and older and men 70 years and older should be screened for asymptomatic osteoporosis.

Women younger than 65 years old at risk for osteoporosis: Estrogen deficiency. Conditions associated with secondary osteoporosis, such as gastrointestinal malabsorption or malnutrition, sprue, osteomalacia, vitamin D deficiency, endometriosis, acromegaly, chronic alcoholism or established cirrhosis, and multiple myeloma.

Individuals who have had a gastric bypass for obesity The accuracy of DEXA in these patients might be affected by obesity. Individuals with an endocrine disorder known to adversely affect BMD e. Individuals with bone dysplasias known to have excessive fracture risk osteogenesis imperfecta, osteopetrosis or high bone density.

Conditions associated with secondary osteoporosis, such as gastrointestinal malabsorption, sprue, inflammatory bowel disease, malnutrition, osteomalacia, vitamin D deficiency, acromegaly, cirrhosis, HIV infection, prolonged exposure to fluorides. Contraindications There are no absolute contraindications to performing DEXA.

Possibly of limited value or require modification of the technique or rescheduling of the examination in some situations, including: Recently administered gastrointestinal contrast or radionuclides. Extremes of high or low body mass index BMI may adversely affect the ability to obtain accurate and precise measurements.

Quantitative computed tomography QCT may be a desirable alternative in these individuals. Any condition that precludes proper positioning of the patient to be able to obtain accurate BMD values.

Equipment A C-arm with x-ray source allowing for variable photon energy levels, collimator, detector, and associated computer software. Preparation Pre-Scan Discussion Patients can tolerate laying on the back for up to 10 minutes. If the patient is greater than pounds, they will require alternative BMD testing.

Recent medical imaging with contrast, such as barium or gadolinium, will preclude imaging 2 weeks after contrast was administered. Premenopausal patients should be asked whether there is any possibility that they might be pregnant.

A pregnancy test may need to be administered before the examination. Patients should wear comfortable, loose-fitting clothes with the avoidance of metal components such as zippers.

For body composition studies, patients should be scanned in the morning after a hour overnight fast for consistency. The menopausal status should be re-checked and whether a pregnancy test or question relating to possible pregnancy has been administered.

Subjects should be dressed in a hospital gown or scrubs, wearing only underpants and, if necessary, thin socks. A thin sheet may be placed over subjects for warmth. Technique or Treatment Interpretation of Results Bone mineral density is the standard for measuring the diagnosis of osteoporosis and fracture risk assessment.

The World Health Organization WHO defines T-scores as: Greater than or equal to Complications No complications considered due to the procedure. Clinical Significance DEXA imaging serves a sentinel role in the evaluation of osteoporosis as the International Society of Clinical Densitometry, the United States Preventative Services Task Force, and the National Osteoporosis Foundation recommend all women over the age of 65 have their bone mineral density evaluated.

Enhancing Healthcare Team Outcomes It is important for the healthcare team to work together to ensure the appropriate DEXA test is ordered and that the test is done correctly. Review Questions Access free multiple choice questions on this topic.

Comment on this article. References 1. Expert Panel on Musculoskeletal Imaging: Ward RJ, Roberts CC, Bencardino JT, Arnold E, Baccei SJ, Cassidy RC, Chang EY, Fox MG, Greenspan BS, Gyftopoulos S, Hochman MG, Mintz DN, Newman JS, Reitman C, Rosenberg ZS, Shah NA, Small KM, Weissman BN.

ACR Appropriateness Criteria ® Osteoporosis and Bone Mineral Density. J Am Coll Radiol. Garg MK, Kharb S. Dual energy X-ray absorptiometry: Pitfalls in measurement and interpretation of bone mineral density.

Indian J Endocrinol Metab. Preidler KW, White LS, Tashkin J, McDaniel CO, Brossmann J, Andresen R, Sartoris D. Dual-energy X-ray absorptiometric densitometry in osteoarthritis of the hip. Influence of secondary bone remodeling of the femoral neck. Acta Radiol. Here are some of the other applications of DXA.

These tests are available at some but not all DXA facilities. Many tests other than DXA can be used to assess your bone health.

Some of them are not as widely used as DXA, but they may provide useful information beyond bone density, or help to determine who needs a DXA. QCT provides a 3-dimensional measurement of bone density and can generate numbers that can be used to diagnose osteoporosis and for input with FRAX.

Most types of QCT tests provide the same type of T-scores for bone mineral density at the hip as does DXA, but at the spine can provide a measurement of bone mineral density of just the spongy bone inside your vertebra. This type of spinal measurement may be preferred if your spinal bones have degenerative disease.

QCT is not as widely used as DXA due to limited availability, higher radiation dose, and being less practical to monitor treatment for most patients.

BCT is an advanced technology that uses data from a CT scan to measure bone mineral density. BCT also uses engineering analysis finite element analysis or FEA to estimate bone strength or measure the breaking strength of bone.

REMS is a portable method that does not use radiation that gives bone density measurements of the hip and spine.

These types of tests measure bone density or other parameters in the peripheral skeleton, namely the arm, leg, wrist, fingers, or heel. Examples include:. The results from these types of tests are not comparable to central DXA measurement and therefore difficult to interpret for diagnostic purposes and thus additional testing is often required.

Screening tests cannot accurately diagnose osteoporosis and should not be used to see how well an osteoporosis medicine is working. Most people need a prescription or referral from their healthcare provider to have a bone density test.

The ideal facility is one with staff that are trained and certified by an organization such as the ISCD, and better yet, one that has been accredited by the ISCD. Most hospital radiology departments, private radiology groups, and some medical practices offer bone density testing.

When you go for your appointment, be sure to take the prescription or referral with you. The testing center will send your bone density test results to your healthcare provider.

You may want to make an appointment to discuss your results with your healthcare provider. As with any medical test, bone density should be repeated when the results might influence treatment plans.

Sometimes spinal abnormalities or a previous spinal fracture can give a false result. A bone density scan will not show whether low bone mineral density is caused by too little bone osteoporosis or too little calcium in the bone, usually because of a lack of vitamin D osteomalacia.

Page last reviewed: 05 October Next review due: 05 October Home Health A to Z Bone density scan DEXA scan Back to Bone density scan DEXA scan. When it is used - Bone density scan DEXA scan Contents Overview When it is used How it is performed.

Identifying bone problems Unlike ordinary X-rays, DEXA scans can measure tiny reductions in bone density. This may include making lifestyle changes to help improve your bone health, such as: eating a healthy, balanced diet that's high in calcium spending more time in the sun to help increase your levels of vitamin D regularly doing weight-bearing exercise, such as walking or running When a bone density scan is recommended A DEXA scan may be recommended if you have an increased risk of developing a bone problem like osteoporosis.

Your risk is increased if you: have had a broken bone after a minor fall or injury have a health condition, such as arthritis, that can lead to low bone density have been taking medicines called oral glucocorticoids for 3 months or more — glucocorticoids are used to treat inflammation, but can also cause weakened bones are a woman who has had an early menopause , or you had your ovaries removed at a young age before 45 and have not had hormone replacement therapy HRT are a postmenopausal woman and you smoke or drink heavily, have a family history of hip fractures , or a body mass index BMI of less than 21 are a woman and have large gaps between periods more than a year Limitations A DEXA scan is not the only way of measuring bone strength.

gov website. Share sensitive information only on official, secure websites. A bone density scan, also known as a DEXA scan, is a type of low-dose x-ray test that measures calcium and other minerals in your bones.

The measurement helps show the strength and thickness known as bone density or mass of your bones. Most people's bones become thinner as they get older.

When bones become thinner than normal, it's known as osteopenia. Osteopenia puts you at risk for a more serious condition called osteoporosis. Osteoporosis is a progressive disease that causes bones to become very thin and brittle.

Osteoporosis usually affects older people and is most common in women over the age of People with osteoporosis are at higher risk for fractures broken bones , especially in their hips, spine, and wrists. Other names: bone mineral density test, BMD test, DEXA scan, DXA; Dual-energy x-ray absorptiometry.

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.

Locations for bone density testing Enlarge image Close. Locations for bone density testing Bone density tests are usually done on bones in the spine vertebrae , hip, forearm, wrist, fingers and heel. By Mayo Clinic Staff. Show references Osteoporosis overview. NIH Osteoporosis and Related Bone Diseases National Resource Center.

Accessed Nov. Lewiecki EM. Overview of dual-energy X-ray absorptiometry. Bone densitometry. Radiological Society of North America. Skeletal scintigraphy bone scan. National Osteoporosis Foundation. Office of Patient Education.

Bone mineral density BMD tests. Mayo Clinic; Bone mass measurement: What the numbers mean. Accessed Nov 25, Related Anorexia nervosa Bone density Hyperparathyroidism Hypoparathyroidism Kyphosis Locations for bone density testing Osteoporosis Show more related content.

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Show the heart some love! Give Today. Help us advance cardiovascular medicine. Find a doctor. Explore careers. Sign up for free e-newsletters. About Mayo Clinic. About this Site. Contact Us. Those who may not necessarily need a DEXA scan: Young Adults with No Risk Factors : Young adults with no known risk factors for osteoporosis and good health are unlikely to benefit significantly from DEXA scans.

In such cases, focusing on a healthy lifestyle, including a balanced diet and regular exercise, is key to building and maintaining strong bones. However, after pregnancy, it may be considered if necessary. Children : Children typically have developing bones, and DEXA scans are not a routine tool for assessing bone health in this age group.

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