What is a DEXA Scan?
Dual-Energy X-ray Absorptiometry (DEXA) is an enhanced form of X-ray technology used to measure bone mineral density (BMD), particularly in the hip and spine. It is considered the primary method for evaluating bone health and is crucial in preventing and managing conditions like osteoporosis, especially in older adults. This quick, painless procedure uses a very low dose of radiation.
Key Reasons Doctors Order a DEXA Scan
Doctors recommend DEXA scans for several key reasons, focusing on assessing and managing bone health.
Screening for Osteoporosis and Osteopenia
A major reason for a DEXA scan is to screen for osteoporosis, which weakens bones and increases fracture risk, and osteopenia, a precursor to osteoporosis. Early detection is crucial. Screening is typically recommended for:
- Women aged 65 or older and men aged 70 or older.
- Postmenopausal women under 65 with risk factors.
- Adults who have experienced a fragility fracture.
Monitoring Bone Loss Treatment
DEXA scans help monitor the effectiveness of treatment for diagnosed osteoporosis or osteopenia, ensuring therapies maintain or improve bone density.
Evaluating Specific Risk Factors
Doctors may order a DEXA scan for individuals with risk factors such as long-term use of certain medications (e.g., corticosteroids), medical conditions like rheumatoid arthritis or kidney disease, lifestyle factors like smoking, and low body weight.
Investigating Unexplained Height Loss or Postural Changes
Significant height loss or changes in posture can indicate vertebral fractures due to osteoporosis, prompting a DEXA scan to evaluate bone health.
The DEXA Scan Procedure: What to Expect
A DEXA scan is a straightforward, non-invasive procedure. You'll need to avoid calcium supplements for 24 hours prior and wear comfortable clothing without metal. Inform your doctor if you are pregnant or have recently had an imaging exam with contrast dye. During the scan, you lie on a table while a scanner arm passes over your body. The scan is painless and takes about 10-20 minutes.
Deciphering the Results
DEXA reports use T-scores and Z-scores to interpret bone density. A T-score compares your BMD to a healthy young adult (normal > -1.0, osteopenia -1.0 to -2.5, osteoporosis < -2.5). A Z-score compares your BMD to others in your age and demographic group.
DEXA Scan vs. Other Bone Assessments
Here is a brief comparison of DEXA with other methods:
| Feature | DEXA Scan | Standard X-ray | Quantitative Computed Tomography (qCT) |
|---|---|---|---|
| Primary Use | Measures bone mineral density (BMD) to diagnose osteoporosis. | Identifies fractures, not accurate for density measurement. | Assesses 3D bone structure and density, sometimes used for complex cases. |
| Accuracy | High; gold standard for BMD. | Poor for density; detects osteoporosis only after significant loss. | Can be more accurate than DEXA with spine degeneration, but higher radiation. |
| Radiation | Very low dose. | Higher than DEXA, but still low. | Significantly higher than DEXA. |
| Procedure | Quick, painless, non-invasive. | Varies. | More involved and longer than DEXA. |
Using DEXA for Body Composition Analysis
Beyond bone density, some DEXA machines can analyze body composition, measuring body fat percentage, lean muscle mass, visceral fat, and fat distribution.
Conclusion: Taking Control of Your Bone Health
Understanding why would a doctor order a DEXA scan is crucial for proactive health. It's a valuable tool for identifying and managing bone density issues and tracking treatment effectiveness. Combined with a healthy lifestyle and regular check-ups, DEXA scans support strong bones as you age. For more information, visit the National Institute on Aging on Osteoporosis.
