Bone Density Scan

A bone density scan, also known as dual-energy X-ray absorptiometry (DXA), is a non-invasive medical test used to measure the density of bones.

Purpose

The primary purpose of a bone density scan is to diagnose and monitor conditions such as osteoporosis, which can increase the risk of fractures. The test can also be used to assess the risk of fracture in individuals with a family history of osteoporosis or those who have experienced a fracture.

How it Works

A bone density scan uses low-level X-rays to measure the density of bones, typically in the hip and spine. The test involves lying on a table while a scanner passes over the body, emitting X-rays that are absorbed by the bones. The amount of X-ray energy absorbed by the bones is measured, and this information is used to calculate bone density.

Types of Bone Density Scans

There are two main types of bone density scans:

• Central DXA: This type of scan measures bone density in the hip and spine, which are common sites for osteoporotic fractures.
• Peripheral DXA (pDXA): This type of scan measures bone density in the peripheral skeleton, such as the heel or forearm.

Preparation

To prepare for a bone density scan, individuals should:

• Avoid wearing clothing with metal fasteners or accessories that may interfere with the X-ray beam.
• Remove any jewelry or other metal objects that may be worn on the body.
• Inform their doctor if they have had a barium study or taken any medications containing barium in the past few days, as this can affect the accuracy of the test.

Risks and Side Effects

The risks associated with bone density scans are minimal. The test uses low-level X-rays, which expose individuals to a small amount of radiation. However, the benefits of the test in diagnosing and monitoring osteoporosis outweigh the risks.

Results

The results of a bone density scan are typically reported as a T-score and a Z-score:

• T-score: This score compares the individual's bone density to that of a healthy young adult. A T-score of -1 or higher is considered normal, while a T-score between -1 and -2.5 indicates osteopenia (low bone mass). A T-score of -2.5 or lower indicates osteoporosis.
• Z-score: This score compares the individual's bone density to that of others of the same age, sex, and ethnicity. A Z-score of -2 or lower may indicate a need for further evaluation.

Follow-up

Based on the results of the bone density scan, individuals may be advised to undergo follow-up testing, make lifestyle changes, or start treatment to prevent or manage osteoporosis. Regular monitoring can help track changes in bone density over time and assess the effectiveness of treatment.