Dual energy X-ray absorptiometry (DXA, previously DEXA) is a means of measuring bone mineral density (BMD). Two X-ray beams with differing energy levels are aimed at the patient's bones. When soft tissue absorption is subtracted out, the BMD can be determined from the absorption of each beam by bone. Dual energy X-ray absorptiometry (DXA) is the most widely used and most thoroughly studied bone density measurement technology. A T-score of -2.5 or less is indicative of osteoporosis.