DEXA Scan: A Vital Tool in Measuring Bone Health

Bones play a major role in the body in terms of protecting organs, providing structure , anchoring muscles and storing calcium. Without dense and healthy bones, individuals are at greater risk for pain and fractures that can lead to other serious physical conditions including limited mobility. Aging, in combination with intrinsic and extrinsic factors, accelerates the decline in bone mass that predispose individuals to fractures. Intrinsic factors include genetics, peak bone mass accrual in youth, hormonal, biochemical and vasculature status. As individuals age, a noticeable reduction in bone formation is witnessed. A key tool in assessing bone health is the DEXA scan, a non-invasive procedure that measures bone mineral density (BMD).


What is a DEXA Scan?


A DEXA scan, or dual-energy X-ray absorptiometry scan, is a non-invasive imaging test that uses low-dose X-rays to see the density and strength of the bones. It's also known as a bone densitometry scan.


They are fast, painless and more effective than standard X-rays in detecting low bone density. These scans are used to evaluate the risk of osteoporosis, a condition that weakens bones and makes them more likely to break. In addition, DEXA scans are also used to find out osteopenia (low bone mass), predict the risk of future fractures, and monitor the effectiveness of osteoporosis treatments. They can also register fat and lean mass distribution throughout the entire body, providing vital information regarding overall and regional assessment of fat mass, lean mass and bone mass. This comprehensive analysis helps individuals tracking weight loss, nutrition, exercise, rehabilitation, and overall health.


How DEXA scan works


The scan works by measuring the mineral content in certain bones, such as the hip, spine and/or wrist. It uses two X-ray beams with different energy levels to estimate bone density. The amount of X-rays that pass through the bone is measured for each beam, allowing the machine to calculate BMD. The results are typically reported as T-scores and Z-scores:


1. T-score: This metric compares the BMD of the patient to a healthy young adult.

2. Z-score: This metric compares a patient’s BMD with that of someone of the same age, sex, and body size. It is primarily used for premenopausal women, men under 50, and children.


Common uses of the procedure


The most common use of this scan is screen for, diagnose, and monitor health conditions involving osteopenia and osteoporosis. Osteopenia is a reduced amount of bone mass and worsening osteopenia can lead to osteoporosis. Factors such as age, body weight, history of prior fractures, family history of osteoporotic fractures, and lifestyle choices can raise the risk of a fracture.


Who should consider a DEXA scan?

Regardless of your sex or age, the doctor may recommend the scan if you’re:

Women aged 65 and older, and men over age 70


Women under age 65 and men aged 50-70 with risk factors such as:


  • Fracture after age 50
  • Rheumatoid arthritis or chronic kidney disease
  • Eating disorders
  • Early menopause (due to natural causes or surgery)
  • History of hormone treatment for prostate or breast cancer
  • Significant loss in height
  • Smoking
  • Family history of osteoporosis
  • Consuming three or more alcoholic drinks per day on most days


How is the scan performed?


During the scan, the individual will asked to lie on the back of a padded table. An x-ray generator is located below the table, with the imaging device attached above. The overhead scanner will move back and forth to measure your bone density or body composition.


To assess the spine, the legs will be supported on a padded box to flatten the pelvis and lower (lumbar) spine. To evaluate the hip, the foot will be placed in a brace that rotates the hip inward. A slowly moving detector then generates images on a computer monitor.


To prevent blurring, the individual may be asked to remain still and hold the breath for a few seconds. A thin, invisible beam of low-dose x-rays is sent by the machine with two distinct energy peaks through the bones being examined. While one peak is absorbed by soft tissue, the other by bone. By subtracting the soft tissue amount from the total, the machine calculates the patient's bone mineral density. The calculated results are then displayed on a computer monitor.



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