Evaluating CMR
Imaging Techniques
Others
- 1Key points (1 page)
- 2Evaluating CMR: Imaging Techniques (1 page)
- 3Dual-Energy X-Ray Absorptiometry (DEXA) (2 pages)
- 4Ultrasonography (2 pages)
- 5References (1 page)
Dual-Energy X-Ray Absorptiometry (DEXA)
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Figure 1: 
Figure 1: Dual-energy x-ray absorptiometry (DEXA) was originally designed to measure bone mineral content, but it is now commonly used to assess total and regional fat and fat-free mass (Figure 1) (1, 2). DEXA assesses body composition based on the attenuation of x-rays emitted at two energy levels as they traverse the body (1, 2). DEXA provides less radiation exposure than CT and costs significantly less. A whole body DEXA scan requires 15 to 35 minutes depending on the scanner and is relatively easy to use in most populations as it requires very little participant effort (3). Once the scan is complete, it can be manually subdivided into truncal and appendicular regions. Measures of total and regional lean mass (coefficient of variation=1 to 7%) (4-6) and fat mass (coefficient of variation=1 to 7%) (5) are highly repeatable, but results may differ depending on the scanner model (e.g., Lunar, Holigic, etc.) (7), the software used (algorithms), and the individual’s sagittal diameter and hydration status (3). Nevertheless, DEXA measures of total or appendicular fat and lean mass closely match the fat and skeletal muscle values obtained by CT or MRI (4, 6, 8-10). Accordingly, DEXA is often used to assess total and appendicular percent fat mass with relatively good accuracy.
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