What is a "bone density test"?

What is a "bone density test"?

Frederick Singer (Director of the Endocrine/Bone Disease Program, John Wayne Cancer Institute ) gives expert video advice on: If my mother had a history of osteoporosis why would I get it too?; Can a doctor tell if I have osteoporosis just by looking at me? and more...

A bone density test is a test using x-rays to determine the density of the spine. By density, we mean the mass per unit volume. We're not weighing the spine, but we're getting an estimate of how much bone there is per size of the bone with that bone density test.