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Created July 9, 2024 08:55
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20240709T105534Z.md

Bone-density scans, also known as dual-energy X-ray absorptiometry (DEXA or DXA) scans, are a common method used to measure bone mineral density (BMD). These scans help diagnose conditions like osteoporosis and assess the risk of fractures. Here's how they generally work:

Technology

  1. Dual-Energy X-Ray Absorptiometry (DEXA/DXA):
    • X-rays: The DEXA scan uses two different X-ray beams with varying energy levels.
    • Absorption Measurement: As these X-rays pass through the body, they are absorbed by bones and soft tissues at different rates. The amount of absorption is measured.
    • Calculation: By comparing the absorption of each beam, the machine calculates bone density.

Procedure

  1. Preparation:

    • Minimal preparation is required. Patients may be advised to avoid calcium supplements for 24 hours before the test.
    • Wear loose, comfortable clothing without metal zippers or buttons.

  2. During the Scan:

    • The patient lies on a padded table.
    • A scanning arm passes over the body but does not enclose it, making it less claustrophobic than an MRI.
    • Common areas scanned include the hip and spine because these sites are most prone to fractures due to osteoporosis.

  3. Duration:

    • The scan typically takes about 10-30 minutes.

Results

  • T-score: Compares your bone density with that of a healthy young adult of your sex.

    • A T-score above −1 is considered normal.
    • A T-score between −1 and −2.5 indicates osteopenia (low bone mass).
    • A T-score below −2.5 indicates osteoporosis.

  • Z-score: Compares your bone density with what is expected in someone of your age, sex, weight, and ethnic or racial origin.

Advancements

  • Modern DEXA machines offer higher precision and lower radiation doses compared to older models.
  • Some newer systems can also provide additional information such as body composition analysis (fat vs muscle mass).

Safety

  • DEXA scans involve minimal radiation exposure—much less than a standard chest X-ray or CT scan—making them safe for repeated use if necessary.

Overall, DEXA scans remain a gold standard for assessing bone health due to their accuracy, speed, and low radiation exposure.

Tue 9 Jul 10:55:34 CEST 2024 - how do bone-density scans work these days?

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