Densitometry

Densitometry is a quantitative method of measuring the bone mineral density (BMD). It is a diagnostic tool that is used to identify osteoporosis, assess an individual's risk for developing fractures, and monitor responses to therapy.

Overview

Densitometry, also known as Dual-energy X-ray absorptiometry (DXA or DEXA), uses a small dose of ionizing radiation to produce images of the inside of the body (usually the lower spine and hips) to measure bone loss. It is the most commonly used and the most standard method for diagnosing osteoporosis.

Procedure

During a DXA procedure, the patient lies on a padded table. An x-ray generator is located below the patient and an imaging device, or detector, is positioned above. The detector passes slowly over the body, generating images on a computer monitor.

Interpretation

The results of a DXA scan are often reported as two scores: T-score and Z-score. The T-score is a comparison of a person's bone density with that of a healthy 30-year-old of the same sex. The Z-score is a comparison of a person's bone density with that of an average person of the same age and sex.

Risks and Limitations

While densitometry is a well-established and accurate method for the diagnosis of osteoporosis, it is not infallible. The test can overestimate bone density in patients with spinal osteoarthritis or aortic calcification and can underestimate bone density in patients with osteomalacia or hyperparathyroidism.

See Also

• Osteoporosis
• Bone mineral density
• Fracture
• Therapy
• Dual-energy X-ray absorptiometry
• Spinal osteoarthritis
• Aortic calcification
• Osteomalacia
• Hyperparathyroidism

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