A dual energy X-ray absorptiometry, or DEXA, uses two low-dose X-ray beams and scans through bones to measure bone density, WebMD explains. One beam emits higher energy than the other beam, and the difference between how much of each X-ray passes through the bone helps determine its density.
There are two types of DEXA scans, central and peripheral, according to MedlinePlus. Central scans typically do not require the patient to remove clothing, and the procedure is commonly used to determine the risk for hip or spine fractures. A peripheral DEXA, also called a p-DEXA, uses a smaller machine to scan smaller appendages, such as wrists or arms. DEXA scans are useful for diagnosing and monitoring osteoporosis.