DEXA (DXA) Scan: Bone Density Test, What Is, How Performed

 What is a DEXA scan?

A DEXA scan is a type of medical imaging test. It uses very low levels of x-rays to measure how dense your bones are. DEXA stands for “dual-energy X-ray absorptiometry.”

A DEXA scan is an imaging test that measures bone density (strength). DEXA scan results can provide helpful details about your risk for osteoporosis (bone loss) and fractures (bone breaks). This test can also measure your body composition, such as body fat and muscle mass.

Medical experts consider DEXA scans to be the most useful, easy, and inexpensive test for helping to diagnose Osteopenia. The test is quick and painless.

What is Osteopenia?

Osteopenia is low bone density, a precursor to Osteoporosis. Often asymptomatic, it increases fracture risk. Lifestyle changes like exercise and diet, along with medication, can mitigate bone loss. Regular monitoring by healthcare providers is essential, particularly for individuals with risk factors.

How does a DEXA scan work?

DEXA scans measure the mineral content in certain bones, such as the hip, spine and/or wrist. It works this way:

• You will be asked to lie on a special DEXA x-ray table. The technologist will help position your correctly and use positioning devices such as foam blocks to help hold the desired position.

• As the arm of the DEXA machine passes over the body, IT uses two different x-ray beams. The beams use very little radiation to keep the test safer, and help to distinguish bone from other tissues.

• The scanner translates the bone density measurement data into pictures and graphs. Bone is most easily seen in white, while the, fat and muscle tissue look like shadows in the background on the technologist’s computer monitor.

• These results are then reviewed and interpreted by a radiologist or other physician trained in DEXA interpretation.

• Your healthcare provider is sent a copy of the written report to discuss with you and consider what treatment is most appropriate.

Who gets a DEXA scan?

Healthcare providers consider many factors when deciding who may benefit from a DEXA scan and how often. Healthcare providers often recommend a DEXA scan to assess your bone health for osteoporosis and fracture risk if you are older than 50, have had a broken bone, or other illnesses that put your bone health at risk.

Research shows women start losing bone mass earlier and faster than men. So healthcare providers usually recommend women get a DEXA scan to screen for osteoporosis at younger ages compared to men.

Your provider may recommend a DEXA scan if you have one or more risk factors for osteoporosis or fractures:

• Increased Age: Many individuals lose bone mass as they get older. The National Osteoporosis Foundation recommends people at average risk get a DEXA scan starting at 65 (women) and 70 (men).

• Family History: If one or more family members have had osteoporosis or more than one fracture, you could be at a higher risk for bone loss.

• Previous fracture injuries: Breaking a bone, especially after age 50, may be a sign that you’re at greater risk. Porous (less dense) bones break more easily.

• Medications: Some medications, such as the steroid prednisone, cancer drugs, and drugs used after an organ transplant can weaken your bones.

• Your overall health: Many chronic medical disorders can make your bones more likely to break. Risky conditions include rheumatoid arthritis, lupus, diabetes, liver disease and kidney disease.

What to expect from a DEXA scan?

A person does not need to prepare — they can eat and drink as usual on the day of the procedure. However, anyone taking a calcium supplement may need to stop taking it around 24 hours before the scan.

Before the scan

An X-ray technician performs the scan on an outpatient basis. A person may need to change into a hospital gown and remove any metal objects that they are wearing, such as jewelry and eyeglasses.

At the start of the scan, the person lies on their back on the exam table. The technician places the imaging device above them and the X-ray generator below them.

During the scan

During the procedure, the imaging arm moves slowly over the person’s body while a beam of low-dose energy passes through them. It is crucial to remain still throughout the scan.

When the purpose is to measure bone density, the technician tends to scan the hips and spine. These are common locations of fractures in people with osteoporosis.

In some cases, the technician scans the wrist, finger, and lower arm. At some locations, there may also be a vertebral fracture assessment Trusted Source during a DEXA scan. This checks the risk of a fracture in the spine.

When the purpose is to measure body composition, the machine scans the entire body to check skinfold thickness at specific sites. Using an equation, it is possible to use these measurements to calculate body fat percentage.

After the scan

Afterward, the person changes back into their clothes. The technician may ask them to complete a questionnaire about their medical history, as this can help a doctor determine their fracture risk. Then, the person can leave the facility.

How long does a DEXA scan take?

The scan is painless and relatively quick, usually taking 10–30 minutes, depending on the equipment and the areas being scanned. Some experts report that it can take just 6 minutes or 10–20 minutes.

How much does a DEXA scan cost?

The cost depends on many factors, such as where a person lives, where they have the scan, and whether they have health insurance that covers it. According to an older report a DEXA scan can cost about Rs 3600- Rs 6800.

Is a DEXA scan painful?

Not at all. You won’t feel a thing as the X-ray beams pass through your body.

You may feel slightly uncomfortable lying on the table, depending on how you’re positioned. But you’ll only need to stay in that position for a few minutes.

Results

The results of a DEXA scan for bone density involve a T-score. Calculating this involves comparing a person’s scan with the bone density of a healthy young adult of the same sex.

According to the World Health Organization (WHO):

• A T-score of -1.0 or higher is normal bone density.
• A T-score of -1.1 to -2.4 indicates osteopenia, or low bone density.
• A T-score of -2.5 or lower indicates osteoporosis.

A DEXA scan may also report results using a Z-score, which shows the amount of bone that a person has, compared with others of the same size, age, and sex. It can help determine whether something uncommon is leading to bone loss.

According to the International Society for Clinical Densitometry, a Z-score of over -2.0 is considered normal. Doctors consider a score below -2.0 as being below the normal range for the person’s age.

When the test also measures body composition, the results include total fat mass and total body fat percentage measurements.