A DEXA scan is the gold standard in clinical body composition analysis. A total body composition test is fast and easy and relatively inexpensive considering the wealth of accurate, reliable information it yields. Its results have been validated through repeated scientific study and are reproducible.
Results from alternatives to DEXA scanning are often misleading, as these measurements are not able to distinguish several factors: gender, age, and obesity or leanness of muscular individuals. Also, other instruments are not able to provide regional body fat values.
This information can serve as a tool for athletes whose aim is optimal body composition for the purpose of enhanced athletic performance. Since a DEXA scan is reproducible, any future scans will provide accurate fat and lean mass trending information. This is ideal for athletes or individuals in a weight management program who would like to gauge their progress or simply measure their body fat.
For more than three decades, the prevalence of obesity has increased rapidly among both adults and children. In 2008, 1.5 billion adults, 20 and older, were overweight. Of these, over 200 million men and nearly 300 million women were obese. The demand for accurate body composition analysis is growing as healthcare providers realize its value in identifying serious health risks that result from obesity, including heart disease and type 2 diabetes.
In as little as three minutes, the Advanced Body Composition assessment feature produces color images displaying the distribution of fat, lean tissue, and bone, translating the information into an easy to interpret report for improved patient management and counseling.
Hologic whole body DEXA systems are the only ones to incorporate the National Health and Nutrition Examination Survey (NHANES) whole body composition reference data. Combined with the recently released guidelines from the Endocrine Society which recommends annual bone mineral density and body composition exams for bariatric surgery patients, the Discovery DEXA system will enable you to improve patient management by not only offering bone mineral density tests, but by also calculating your patient’s body composition.
What is DEXA?
Dual Energy X-Ray Absorptiometry (DEXA)
Description: DEXA is a fairly new technology. It is based on the three component model of body composition. DEXA uses two X-ray energies to measure body fat, muscle, and bone mineral. When having the scan done, one must lay still in the supine position on what looks like an x-ray table. It takes approximately three minutes for the computer software to produce an image of the tissues. The results may be viewed as whole body estimates of body fat, muscle, and bone mineral as well as regional body estimates.
How accurate is it?: DEXA takes bone mineral content into consideration when estimating body fat and muscle, therefore it is considered to be more accurate and valid than a two component model of body composition such as underwater weighing.
- Radiation exposure is low
- DEXA is quick
- One does not have to wear a bathing suit or skimpy clothing
- There is no special preparation on the part of the participant
- Most insurances do not pay for this procedure but out of pocket expense is reasonable. Currently $75.00 at Quality of Life Medical and Research Center
Where Can I Have it Done?
- It can be done at universities and research facilities such as Quality of Life.
- It may be free for those participating in a research study
DEXA Bone Density Scan
- What is a Bone Density Scan (DXA)?
- 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 do I get them?
- What are the benefits vs. risks?
- What are the limitations of DXA Bone Densitometry?
- Can anyone have a DEXA exam?
- Is a DEXA scan safe?
- Are DEXA scans covered by insurance?
What is a Bone Density Scan (DXA)?
Bone density scanning, also called dual-energy x-ray absorptiometry (DXA) or bone densitometry, is an enhanced form of x-ray technology that is used to measure bone loss. DXA is today’s established standard for measuring bone mineral density (BMD).Read MoreAn x-ray (radiograph) is a noninvasive medical test that helps physicians diagnose and treat medical conditions. Imaging with x-rays involves exposing a part of the body to a small dose of ionizing radiation to produce pictures of the inside of the body. X-rays are the oldest and most frequently used form of medical imaging.
DXA is most often performed on the lower spine and hips. In children and some adults, the whole body is sometimes scanned. Peripheral devices that use x-ray or ultrasound are sometimes used to screen for low bone mass. In some communities, a CT scan with special software can also be used to diagnose or monitor low bone mass (QCT). This is accurate but less commonly used than DXA scanning.
What are some common uses of the procedure? DXA is most often used to diagnose osteoporosis, a condition that often affects women after menopause but may also be found in men. Osteoporosis involves a gradual loss of calcium, as well as structural changes, causing the bones to become thinner, more fragile and more likely to break.
DXA is also effective in tracking the effects of treatment for osteoporosis and other conditions that cause bone loss.
The DXA test can also assess an individual’s risk for developing fractures. The risk of fracture is affected by age, body weight, history of prior fracture, family history of osteoporotic fractures and life style issues such as cigarette smoking and excessive alcohol consumption. These factors are taken into consideration when deciding if a patient needs therapy.
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 125 pounds).
- are a man with clinical conditions associated with bone loss.
- 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 Lateral Vertebral Assessment (LVA), 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.
How should I prepare? On the day of the exam you may eat normally. You should not take calcium supplements for at least 24 hours before your exam.
You should wear loose, comfortable clothing, avoiding garments that have zippers, belts or buttons made of metal. Objects such as keys or wallets that would be in the area being scanned should be removed.
You may be asked to remove some or all of your clothes and to wear a gown during the exam. You may also be asked to remove jewelry, dentures, eye glasses and any metal objects or clothing that might interfere with the x-ray images.
Inform your physician if you recently had a barium examination or have been injected with a contrast material for a computed tomography (CT) scan or radioisotope scan. You may have to wait 10 to 14 days before undergoing a DXA test.
Women should always inform their physician and x-ray technologist if there is any possibility that they are pregnant. Many imaging tests are not performed during pregnancy so as not to expose the fetus to radiation. If an x-ray is necessary, precautions will be taken to minimize radiation exposure to the baby.
What does the equipment look like? There are two types of DXA equipment: a central device and a peripheral device.
Central DXA devices measure bone density in the hip and spine and are usually located in hospitals and medical offices. Central devices have a large, flat table and an “arm” suspended overhead.
Peripheral devices measure bone density in the wrist, heel or finger and are often available in drugstores and on mobile health vans in the community. The pDXA device is much smaller than the Central DXA device, weighing only about 60 pounds. It is a portable box-like structure with a space for the foot or forearm to be placed for imaging. Other portable technologies such as specially designed ultrasound machines, are also sometimes used for screening.
How does the procedure work?
The DXA machine sends a thin, invisible 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.
DXA machines feature special software that compute and display the bone density measurements on a computer monitor.
How is the procedure performed? This examination is usually done on an outpatient basis.
In the Central DXA examination, which measures bone density in the hip and spine, the patient lies on a padded table. An x-ray generator is located below the patient and an imaging device, or detector, is positioned above.
To assess the spine, the patient’s legs are supported on a padded box to flatten the pelvis and lower (lumbar) spine. To assess the hip, the patient’s foot is placed in a brace that rotates the hip inward. In both cases, the detector is slowly passed over the area, generating images on a computer monitor.
You must hold very still and may be asked to keep from breathing for a few seconds while the x-ray picture is taken to reduce the possibility of a blurred image. The technologist will walk behind a wall or into the next room to activate the x-ray machine.
The peripheral tests are simpler. The finger, hand, forearm or foot is placed in a small device that obtains a bone density reading within a few minutes.
An additional procedure called Lateral Vertebral Assessment (LVA) is now being done at many centers. LVA is a low-dose x-ray examination of the spine to screen for vertebral fractures that is performed on the DXA machine.
The LVA test adds only a few minutes to the DXA procedure.
The DXA bone density test is usually completed within 10 to 30 minutes, depending on the equipment used and the parts of the body being examined.
You will probably be asked to fill out a questionnaire that will help the doctor determine if you have medical conditions or take certain medications that either increase or decrease your risk of a fracture. The World Health Organization has recently released an online survey that combines the DXA results and a few basic questions and can be used to predict 10-year hip fracture risk for post-menopausal women. This will be coming into more use in the next few years.
What will I experience during and after the procedure? Bone density tests are a quick and painless procedure.
Routine evaluations every two years may be needed to see a significant change in bone mineral density, decrease or increase. Few patients, such as patients on high dose steroid medication, may need follow-up at six months.
Who interprets the results and how will I get them? A radiologist, a physician specifically trained to supervise and interpret radiology examinations, will analyze the images and send a signed report to your primary care or referring physician, who will discuss the results with you.
DXA scans are also interpreted by other physicians such as rheumatologists and endocrinologists.
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. A score above -1 is considered normal. A score between -1 and -2.5 is classified as osteopenia (low bone mass). A score below -2.5 is defined as osteoporosis. 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.
Small changes may normally be observed between scans due to differences in positioning and usually are not significant.
What are the benefits vs. risks?
- 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 the most accurate method available for the diagnosis of osteoporosis and is also considered an accurate estimator of fracture risk.
- DXA equipment is widely available making DXA bone densitometry testing convenient for patients and physicians alike.
- No radiation remains in a patient’s body after an x-ray examination.
- X-rays usually have no side effects in the diagnostic range.
- There is always a slight chance of cancer from excessive exposure to radiation. However, the benefit of an accurate diagnosis far outweighs the risk.
- Women should always inform their physician or x-ray technologist if there is any possibility that they are pregnant.
- The effective radiation dose for this procedure varies.
- No complications are expected with the DXA procedure.
A Word About Minimizing Radiation Exposure
Special care is taken during x-ray examinations to use the lowest radiation dose possible while producing the best images for evaluation. National and international radiology protection councils continually review and update the technique standards used by radiology professionals.
State-of-the-art x-ray systems have tightly controlled x-ray beams with significant filtration and dose control methods to minimize stray or scatter radiation. This ensures that those parts of a patient’s body not being imaged receive minimal radiation exposure.
What are the limitations of DXA Bone Densitometry?
- A DXA test cannot predict who will experience a fracture but can provide indications of relative risk.
- Despite its effectiveness as a method of measuring bone density, DXA is of limited use in people with a spinal deformity or those who have had previous spinal surgery. The presence of vertebral compression fractures or osteoarthritis may interfere with the accuracy of the test; in such instances, CT scans may be more useful.
- Central DXA devices are more sensitive than pDXA devices but they are also somewhat more expensive.
- A test done on a peripheral location, such as the heel or wrist, may help predict the risk of fracture in the spine or hip. These tests are not helpful in following response to treatment, however, and if they indicate that drug therapy is needed, a baseline central DXA scan should be obtained.
Exam costs: The costs for specific medical imaging tests and treatments vary widely across geographic regions. Many—but not all—imaging procedures are covered by insurance. Discuss the fees associated with your medical imaging procedure with your doctor and/or the medical facility staff to get a better understanding of the portions covered by insurance and the possible charges that you will incur.
Can anyone have a DEXA exam? If you are pregnant or have had an x-ray contrast, barium study, or nuclear medicine scan within the last 30 days, you must wait until cleared. If you have any metal implants, discuss this with your doctor or the technologist performing the exam.
Is a DEXA scan safe? DEXA scans are a form of x-ray which means they use some radiation. However, Dexa scans use a very low dose of radiation, about 1/30th of that used in a standard chest x-ray.
Are DXA screenings covered by insurance? Generally your insurance carrier will cover DXA screening when ordered by your referring physician or on an annual basis if you have been diagnosed with osteoporosis. DXA screening is also covered if risk factors are present, which are most females in menopause. For males screening is usually not covered unless they had some bone breakage. It is however recommended in all males 75 years of age and older.
Medicare and most other insurance carriers will pay for an exam every two years if you have osteopenia, a condition where the bone mineral density is lower than normal. Osteopenia is considered by many doctors a precursor to osteoporosis.
Any questions please call the service provider that scheduled this for you or contact Quality of Life Medical Center @ 520.733.2250
Dexa Scan (Bone Density Study)
Dexa Scan’s are scheduled at Quality of Life Medical Center. You should enter at the Diagnostic Center bldg. 5350 and register in the main lobby approximately 15 minutes before your appointment time. Read More
- On the day of the exam you may eat normally. You should not take calcium supplements for at least 24 hours before your exam.
- On the day of the exam you should wear loose, comfortable clothing, avoiding garments that have zippers, belts or buttons made of metal. Objects such as keys or wallets that would be in the area being scanned should be removed.
- You may be asked to remove some or all of your clothes and to wear a gown during the exam. You may also be asked to remove jewelry, dentures, eye glasses and any metal objects or clothing that might interfere with the x-ray images.
- Inform your physician if you recently had a barium examination or have been injected with a contrast material for a computed tomography (CT) scan or radioisotope scan. You may have to wait 10 to 14 days before undergoing a DXA test.
- Women should always inform their physician and x-ray technologist if there is any possibility that they are pregnant. Many imaging tests are not performed during pregnancy so as not to expose the fetus to radiation. If an x-ray is necessary, precautions will be taken to minimize radiation exposure to the baby.
- Please bring all insurance information with you.
- Please remember to bring the signed Physician’s order form with you.
- If you have metal in your hips or spine, let the technologist know.
- We suggest you leave valuables at home.