Bone Density which is also called bone densitometry, uses specialized x-rays to measure the thickness and strength of your bones. Various scanners use different techniques. The one used most often is dual-energy x-ray absorptiometry (DXA or DEXA). Quantitative ultrasound, which does not involve x-rays, may also be used.
Bone density scans are very important for the study, diagnosis, and treatment of osteoporosis. When bones are somewhat thin, the condition is called osteopenia. When bones become very thin, the condition is called osteoporosis. Bone density tests provide a precise measure of whether you have osteopenia or osteoporosis.
A bone densitometry scan of identical twins.
Image credit: "Identical twins' bone scan." The Gale Encyclopedia of Medicine, edited by Jacqueline L. Longe, 5th ed., Gale, 2015. Gale OneFile: Health and Medicine, https://link.gale.com/apps/doc/PC4205141631/HRCA?u=nysl_me_sfc&sid=HRCA&xid=87abd1ba. Accessed 29 Aug. 2020.