DXA: Dual X-ray absorptometry. A technique for scanning bone and measuring bone mineral density (BMD). A DXA scanner is a large machine that produces 2 X-ray beams, each with different energy levels. One beam is high energy while the other is low energy. The amount of x-rays that pass through the bone is measured for each beam. This will vary depending on the thickness of the bone. Based on the difference between the 2 beams, the bone density can be measured. DXA is relatively easy to perform and the amount of radiation exposure is considered low. DXA is also called dual energy X-ray absorptometry or DEXA.