DEXAscanning

DEXAscanning, or dual-energy X-ray absorptiometry, is a medical imaging technique used to measure bone mineral density and, in many settings, body composition. It works by directing two X-ray beams at the body with different energy levels; the differing absorption by bone and soft tissue allows calculation of bone mineral content, bone mineral density, and estimates of lean mass and fat mass.

Commonly evaluated sites include the lumbar spine and the hip, with forearm measurements when spine or hip are not feasible. The exam is quick and involves relatively low radiation exposure. DEXA devices are typically fan-beam or pencil-beam systems and are widely available in hospitals, clinics, and some radiology centers.

Clinical uses include diagnosis and monitoring of osteoporosis and osteopenia, assessment of fracture risk often in conjunction with other tools, and evaluation of response to osteoporosis therapy. DEXA is also used to assess body composition for research and clinical purposes, such as estimating regional lean mass and fat mass.

Results are reported as T-scores and Z-scores. A T-score compares bone density with a young healthy reference population, while a Z-score compares with an age-matched population. The World Health Organization criteria classify osteoporosis as a T-score of −2.5 or lower and osteopenia as a T-score between −1.0 and −2.5. Measurements can be influenced by age, degenerative changes, implants, and body size, and accuracy depends on proper calibration and technique. Pregnancy is generally advised against for safety reasons.

Safety and accessibility: DEXA delivers a very low radiation dose and typically takes only a few minutes, but availability may vary by region. Limitations include weight or size limits of some scanners and reduced accuracy in certain populations.