Dual-Energy X-Ray Absorptiometry (DEXA) Scan

A DEXA scan, also known as a DXA scan, is a non-invasive medical test used to measure bone mineral density (BMD) and assess the risk of osteoporosis. The procedure uses two different energy levels of X-rays to distinguish between bone and soft tissue, allowing for accurate measurements of bone density.

How it Works

The DEXA scan machine sends two types of X-ray beams through the body: a high-energy beam and a low-energy beam. The high-energy beam is absorbed by dense materials like bone, while the low-energy beam is absorbed by softer tissues like fat and muscle. By comparing the absorption rates of the two beams, the machine can calculate the density of the bone.

Types of DEXA Scans

There are several types of DEXA scans, including:

• Central DEXA scan: Measures BMD in the hip and spine, which are common sites for osteoporotic fractures.
• Peripheral DEXA scan: Measures BMD in the heel, shinbone, or finger, often used for screening purposes.
• Total body DEXA scan: Measures BMD of the entire body, providing a comprehensive assessment of bone health.

Preparation and Procedure

To prepare for a DEXA scan:

• Avoid wearing clothing with metal fasteners or accessories that may interfere with the X-rays.
• Remove any jewelry, glasses, or other objects that may contain metal.
• Wear comfortable clothing and avoid eating a heavy meal before the test.

The procedure typically takes 10-30 minutes to complete, during which time you will lie on a table while the DEXA machine scans your body. You may be asked to hold still or change positions to ensure accurate measurements.

Risks and Side Effects

DEXA scans are generally safe and painless, with minimal risks and side effects. However:

• Radiation exposure: DEXA scans use low levels of X-ray radiation, which is considered safe for most people.
• Allergic reactions: Some people may experience an allergic reaction to the X-ray dye used in some DEXA scans.

Results and Interpretation

The results of a DEXA scan are typically reported as a T-score, which compares your BMD to that of a healthy young adult. The T-score is used to diagnose osteoporosis and assess the risk of fractures:

• Normal bone density: T-score above -1.
• Osteopenia (low bone mass): T-score between -1 and -2.5.
• Osteoporosis: T-score below -2.5.

Uses and Applications

DEXA scans are commonly used to:

• Diagnose osteoporosis: Identify individuals with low bone mass or osteoporosis.
• Monitor treatment effectiveness: Track changes in BMD over time to assess the efficacy of osteoporosis treatments.
• Assess fracture risk: Evaluate the likelihood of fractures in individuals with osteoporosis or low bone mass.