DEXA Scan

Dual-energy X-ray absorptiometry (DEXA) is the therapeutic standard for measuring bone mineral density⁽¹⁾.
DEXA has several diagnostic applications, including evaluation of bone mass measurement and diagnosis of osteoporosis⁽²⁾.
DEXA scans may be necessary for individuals with advanced age, family history of osteoporosis, previous bone fracture, specific medications, and risky conditions such as lupus and diabetes⁽³⁾.
DEXA is a low-cost screening test for those who meet the screening criteria. However, this procedure is not advisable for early post-menopausal women⁽⁴⁾.

What Is a DEXA Scan?

A DEXA scan is a medical imaging procedure for assessing bone density (strength). This test can also determine body composition, such as fat percentage and muscle mass.

The term DEXA stands for “dual-energy X-ray absorptiometry.”

DEXA Scan is also known as:

DXA Scan
Bone density scan
BMD (bone mineral density) test⁽⁵⁾
Bone densitometry⁽⁶⁾
Bone density testing

A DEXA scan can provide helpful information about an individual’s risk of osteoporosis (bone loss) and fractures (bone breaks)⁽⁷⁾. This bone density test uses a low dose of X-ray radiation to measure calcium and other minerals in the bone⁽⁸⁾.

Medical experts regard DEXA scans as one of the most useful, simple, and inexpensive tests for diagnosing osteoporosis⁽⁹⁾.

A DEXA scan can also help identify if an individual has osteopenia (low bone density)⁽¹⁰⁾. Osteopenia and osteoporosis are two categorically similar bone disorders.

Uses and Purposes of DEXA Scans

Bone densitometry has several diagnostic applications. These uses belong to two categories.

Firstly, healthcare professionals recommend bone mass measurement in patients with high-risk factors to assess fracture risk and treatment options. Patients with bone density above the treatment threshold may test every two to three years until the measurements discover the underlying issues⁽¹¹⁾.

Secondly, bone densitometry can confirm osteoporosis in patients with osteopenia or vertebral (spinal) deformity radiology findings. This use also applies to individuals who have had a fragility fracture at the wrist, hip, or spine⁽¹²⁾.

Total body bone density scans can also determine the amount of bone, fat, and muscle present⁽¹³⁾. These factors may indicate the patient’s bone health.

Benefits of a DEXA Scan

Several benefits of a DEXA scan include⁽¹⁴⁾:

Detecting weak or brittle bones to aid in the prediction of future fractures
Assessing whether bone density is improving, worsening, or stable
Can assist patients and their healthcare providers in developing strategies to improve bone strength and prevent deterioration of conditions

Risks of a DEXA Scan

There is a slight increase in the likelihood of future cancer, comparable to the risks associated with X-rays⁽¹⁵⁾.

For a spine plus femur DEXA scan, the amount of radiation may vary from less than one μSv to about 15 μSv⁽¹⁶⁾. Sv or sievert is the unit of measurement for the health impact of radiation exposure on the human body.

Types of DEXA Scan

There are two different classifications of DEXA scans⁽¹⁷⁾:

Peripheral DEXA scan: Also known as p-DEXA, this type of test determines the bone density in the leg, wrist, fingers, or foot.
Central DEXA scan: This test assesses bone density in the lower back and hips. A Central DEXA scan is the most common method for detecting osteoporosis.

The two standards for evaluating DEXA scans are the bone density of a healthy adult of the same age and gender (Z-score) and a healthy 30-year-old (T-score)⁽¹⁸⁾.

Tests and Procedures

A DEXA scan is an easy and painless procedure involving patients lying on their back on an X-ray table to scan a specific body area⁽¹⁹⁾.

Depending on the part of the body under examination, the patient may remain fully clothed.

Additionally, a DEXA scan does not require an individual to enter a tunnel or receive an injection. Instead, the patient may lie on their back on a padded table that is flat and open. They must also remain still during the procedure to avoid blurring the images.

A radiographer, a specialist in taking X-ray images, usually performs the scan⁽²⁰⁾.

A large scanning arm may pass over the patient’s body to measure bone density in the center of the skeleton during the scan.

As the scanning arm moves gradually, a narrow beam of low-dose X-rays may pass through the part of the patient’s body under observation.

Typically, the equipment examines the individual’s hip and lower spine to look for weak bones (osteoporosis)⁽²¹⁾. However, because bone density differs across the skeleton, the procedure may examine more than one body area.

Specific health problems, such as thyroid conditions, may require scanning the forearm if the hip or spine is not possible to scan.

Tissues, such as fat and bone, may absorb some X-rays passing through the body.

Inside the scanning arm, an X-ray detector counts the number of X-ray beams passed through the patient’s body. This data helps in generating an image of the scanned area.

The scan typically takes between 10 and 20 minutes. Individuals may go home once the procedure is over⁽²²⁾.

DEXA Scan Results and Outlook

A bone density test assesses bone mineral density (BMD). This procedure compares the patient’s BMD to healthy young adults (T-score) and the same age (Z-score)⁽²³⁾.

T-Scores

T-scores compare an individual’s BMD to the BMDs of healthy 25- to 35-year-old adults of the same sex and ethnicity. The standard deviation (SD) is the difference in BMD between the patient and healthy young adults.

Positive T-scores suggest that the bone is more robust than usual, while negative T-scores indicate weak bones⁽²⁴⁾.

The World Health Organization (WHO) defines osteoporosis based on specific bone density levels⁽²⁵⁾.

Classification	Bone Mineral Density	T-Score
Normal	One SD (+1 or -1) of the mean level for a young adult benchmark population	T-score at −1.0 and above
Low bone mass (Osteopenia)	Anywhere from 1 and 2.5 SD below the mean level for a young adult benchmark population	T-score between −1.0 and −2.5
Osteoporosis	2.5 or more SD below the mean level for a young adult benchmark population	T-score at or below −2.5
Severe or established osteoporosis	2.5 or more SD below that of the mean level for a young adult benchmark population with fractures	T-score of 2.5 or less with one or more fractures

Overall, for every SD below average, the risk of bone fracture doubles. An individual with a BMD that is one standard deviation below normal (T-score of -1) has twice the risk of bone fracture as someone with a normal BMD⁽²⁶⁾.

When this data above is available, people at high risk of bone fracture can find treatment to avoid future fractures.

Z-Scores

Z-scores compare a patient’s BMD to a same-age norm.

Z-scores calculation is similar to T-scores. However, the former standard uses a benchmark population of the same age, gender, race, height, and weight to compare⁽²⁷⁾.

In addition to a DEXA scan, a health professional may recommend blood tests to detect kidney disease, assess the function of the parathyroid gland, the effects of cortisol therapy, and the concentration of minerals in the body linked with bone strength.

A radiologist or another doctor trained in DEXA interpretation reviews and interprets the procedure results⁽²⁸⁾.

Who Is Qualified for a DEXA Scan?

Healthcare professionals consider many factors to determine who may benefit from a DEXA scan and how often these patients should get the procedure.

There are multiple osteoporosis risk factors and indications for densitometry testing. The following are some of the most common risk factors for osteoporosis⁽²⁹⁾:

Increasing age, women over 65, and men over 70
Hip fractures that run in the family
Smoking
Heavy drinking of alcohol
Long-term use of steroids and certain medications
Post-menopausal women who do not take estrogen
Low body mass index (BMI)
Specific diseases, including rheumatoid arthritis, type 1 diabetes mellitus, liver disease, kidney disease, hyperthyroidism, or hyperparathyroidism

The National Osteoporosis Foundation suggests that individuals at average risk get a DEXA scan, specifically adults beginning at 65 (women) and 70 (men)⁽³⁰⁾.

Furthermore, bone loss may occur due to aging and decreased estrogen and testosterone levels, especially after menopause⁽³¹⁾. This condition may also necessitate DEXA scans.

Clinical Appointments

Each country may vary in its protocols concerning the administration of DEXA scans.

In the United States, Medicare (US federal health insurance) allows individuals to undergo DEXA scans once every two years⁽³²⁾. There may be some exceptions to this policy if the patient has specific conditions.

The COVID-19 pandemic may have caused significant healthcare disruptions in recent years.

For example, one study showed that routine outpatient appointments and investigations had experienced delays in the United Kingdom due to the COVID-19 pandemic⁽³³⁾.

Individuals who require DEXA scans may check their selected clinics regarding how to schedule an appointment.

Preparations for the Procedure

Most individuals do not need to alter their daily routines in preparation for a DEXA scan⁽³⁴⁾. Unless the healthcare provider gives specific instructions, the patient may eat, drink, and take any medications as usual.

Patients may also have to complete a questionnaire about their present health, family history of bone fractures, smoking history, and medication lists⁽³⁵⁾.

Before the test, individuals may have to:

Refrain from taking calcium supplements, multivitamins, and antacids for 24 hours before the test.
Inform the doctor if they think they are pregnant because DEXA scans use minimal radiation. Medical experts advise avoiding radiation exposure during pregnancy to protect an unborn child⁽³⁶⁾.
Wear comfortable clothing, like loose-fitting clothes.
Choose items that do not contain metal (zippers, buttons, or buckles). Sweatpants and a casual top are also possible options.
Notify the doctor that they have recently had a barium exam or had a contrast agent infused for a CT scan or nuclear medicine procedure⁽³⁷⁾. Contrast materials may disrupt one’s bone density test.

Limitations

The DEXA scan is not the only way to assess bone density. Other risk factors, such as family history and the use of specific medications, can help decide whether or not an individual is at risk of breaking a bone⁽³⁸⁾.

Individuals must consider all risk factors before having a bone density scan or beginning treatment. A bone density scan may be necessary for some people to confirm that their risk of breaking a bone is high enough to warrant treatment.

Others, particularly older people over the age of 75, may not require a bone density scan before receiving treatment because the risk of breaking a bone is significantly high⁽³⁹⁾.

Moreover, it can be challenging to understand the results of a bone density scan. For example, when someone has a degenerative disorder like osteoarthritis of the spine, it may be difficult to interpret the results of a spine scan (spondylosis)⁽⁴⁰⁾.

Spinal abnormalities or a previous spinal fracture may also cause false results.

Furthermore, a bone density scan cannot reveal whether low bone mineral density is due to a severe lack of bone (osteoporosis) or a lack of calcium in the bone, typically due to a vitamin D deficiency (osteomalacia)⁽⁴¹⁾.

Costs

In the United States, a DEXA scan may cost around $125⁽⁴²⁾. Moreover, if the physician prescribes a drug for mild bone loss, the patient may have to spend more money.

Generic alendronate can cost up to $75 for a month’s supply. Fosamax, the brand name for the same medication, can be twice as expensive⁽⁴³⁾.

DEXA Scan Accuracy

DEXA scans are known for their precision and accuracy. Medical experts regard DEXA scans as accurate tests for diagnosing osteoporosis⁽⁴⁴⁾.

Unlike X-ray equipment, DEXA machines undergo regular inspection to measure bone minerals accurately. Additionally, no two DEXA machines are the same. This feature is why physicians usually insist on conducting a patient’s DEXA tests on the same machine.

How Long Will a DEXA Scan Take?

A DEXA scan can take about 25 minutes on average. Usually, patients enter and exit the examination room in less than 30 minutes⁽⁴⁵⁾.

What Happens After a DEXA Scan?

DEXA tests are painless and quick. Following the test, patients should be able to resume their normal activities.

Certified professionals may review the results to interpret DEXA images. Afterward, the patient’s healthcare provider may receive a written report regarding the procedure findings.

The healthcare provider may go over the test results with the patient and explain the report regarding the client’s health.

The physician can assist individuals in making choices about keeping their bones healthy. These healthcare professionals may also suggest dietary and lifestyle changes to reduce fracture risk.

What to Ask the Healthcare Provider

If the healthcare provider has recommended a DEXA scan, the patient may inquire about the following:

Why do you think I should take the DEXA test?
What should I do to get ready for the exam?
What can I do at home to maintain the health of my bones?
When can I expect to receive my test results?
Where should I go to get this test?

Individuals tend to lose bone density as they age. However, that does not mean individuals should accept brittle bones as a natural part of aging.

It is never too early to start thinking about bone health. Hence, concerned individuals may request a DEXA scan to help evaluate their present bone health.

Furthermore, they may discuss with their physicians the possible steps to take to slow down or prevent bone loss in the future.

What Is Osteoporosis?

Osteoporosis induces bones to become weak and brittle, making them susceptible to fractures from minor stresses like bending over or coughing. The wrist, spine, and hip are common sites for osteoporosis-related fractures⁽⁴⁶⁾.

Bone is a tissue that is constantly breaking down and replacing itself. When new bone formation fails to keep up with the loss of old bone, osteoporosis develops⁽⁴⁷⁾.

What Is Osteopenia?

The loss of bone mineral density is known as osteoporosis (BMD). Lower BMD suggests that an individual’s bones contain fewer minerals than necessary, making the bones weaker⁽⁴⁸⁾.

Osteopenia is not as bad as osteoporosis, which weakens bones to the point where they can break easily.

Osteoporosis does not develop in everyone with osteopenia. However, this development is possible.

Individuals with osteoporosis should work to strengthen and protect their bones. Their bone mineral density requires monitoring by relevant healthcare providers.

Qualifications for DEXA Technologists

According to one report, each state may vary in its requirements for DXA operators in the United States⁽⁴⁹⁾. This study showed⁽⁵⁰⁾:

That 17 states mandated registered technologists (RT) or authorized/licensed limited certification;
Sixteen states had no certification requirements;
Twelve states required RT certification;
Five states had state-specific requirements.

The study above indicated a lack of consistency among states regarding central DXA operator training requirements⁽⁵¹⁾. Furthermore, DXA operators in states with requirements were frequently unaware of the requirements.

Uniform national training requirements for central DXA operators may be necessary to ensure adequate DXA scan quality⁽⁵²⁾.

To scan or not to scan? DXA in postmenopausal women
https://www.ccjm.org/content/87/4/205
Bone Densitometry in Clinical Practice
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2549881/pdf/bmj00596-0033.pdf
DEXA (DXA) Scan: Bone Density Test
https://my.clevelandclinic.org/health/diagnostics/10683-dexa-dxa-scan-bone-density-test
To scan or not to scan? DXA in postmenopausal women
https://my.clevelandclinic.org/health/diagnostics/10683-dexa-dxa-scan-bone-density-test
Bone Density Scan
https://medlineplus.gov/lab-tests/bone-density-scan/
Bone Densitometry
https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/bone-densitometry
DEXA (DXA) Scan: Bone Density Test
https://my.clevelandclinic.org/health/diagnostics/10683-dexa-dxa-scan-bone-density-test
Ibid.
DEXA (DXA) Scan: Bone Density Test
https://my.clevelandclinic.org/health/diagnostics/10683-dexa-dxa-scan-bone-density-test
Osteopenia
https://my.clevelandclinic.org/health/diseases/21855-osteopenia
Bone Densitometry in Clinical Practice
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2549881/pdf/bmj00596-0033.pdf
Ibid.
When it is used: Bone density scan (DEXA scan)
https://www.nhs.uk/conditions/dexa-scan/why-its-done/
Radiation in Healthcare: Bone Density (DEXA Scan)
https://www.cdc.gov/nceh/radiation/dexa-scan.html
Ibid.
Radiation protection of patients during DXA
https://www.iaea.org/resources/rpop/health-professionals/other-specialities-and-imaging-modalities/dxa-bone-mineral-densitometry/patients
What’s a DEXA Scan?
https://www.mana.md/whats-a-dexa-scan/
Ibid.
How it is performed
https://www.nhs.uk/conditions/dexa-scan/what-happens/
Ibid.
Ibid.
Ibid.
Bone Densitometry
https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/bone-densitometry
Ibid.
Table 4
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5335887/table/t4-ejr-4-1-46/?report=objectonly
Bone Densitometry
https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/bone-densitometry
Ibid.
DEXA (DXA) Scan: Bone Density Test
https://my.clevelandclinic.org/health/diagnostics/10683-dexa-dxa-scan-bone-density-test
Bone Densitometry
https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/bone-densitometry
DEXA (DXA) Scan: Bone Density Test
https://my.clevelandclinic.org/health/diagnostics/10683-dexa-dxa-scan-bone-density-test
To scan or not to scan? DXA in postmenopausal women
https://www.ccjm.org/content/87/4/205
DEXA (DXA) Scan: Bone Density Test
https://my.clevelandclinic.org/health/diagnostics/10683-dexa-dxa-scan-bone-density-test
A pragmatic proposal for triaging DXA testing during the COVID-19 global pandemic
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7640538/
DEXA (DXA) Scan: Bone Density Test
https://my.clevelandclinic.org/health/diagnostics/10683-dexa-dxa-scan-bone-density-test
Ibid.
Ibid.
Bone density test
https://www.mayoclinic.org/tests-procedures/bone-density-test/about/pac-20385273
When it is used -Bone density scan (DEXA scan)
https://www.nhs.uk/conditions/dexa-scan/why-its-done/
Ibid.
Ibid.
Ibid.
Bone-Density Tests
https://www.choosingwisely.org/patient-resources/bone-density-tests/
Ibid.
DEXA (DXA) Scan: Bone Density Test
https://my.clevelandclinic.org/health/diagnostics/10683-dexa-dxa-scan-bone-density-test
Ibid.
Osteoporosis
https://www.mayoclinic.org/diseases-conditions/osteoporosis/symptoms-causes/syc-20351968
Ibid.
Osteopenia
https://my.clevelandclinic.org/health/diseases/21855-osteopenia
Training requirements for DXA technologists in the United States
https://pubmed.ncbi.nlm.nih.gov/16055953/
Ibid.
Ibid.
Ibid.