Table 1.

Traits determined by non-invasive techniques

Non-invasive technique	Trait
Dual-energy X-ray absorptiometry (DXA)	Photon number passage (tissue level)
	X-ray attenuation coefficient from two energy levels
	Bone mineral content
	Bone mineral area
	Bone mineral density
	Soft tissue mass
	Lean tissue mass
	Fat tissue mass
	Whole-body and regional data
Computed tomography (CT)	Photon number passage (tissue level)
	X-ray attenuation in Hounsfield units (HU)
	Tissue areas or volumes depending on anatomical position and HU
	Regional and whole-body data
Magnetic resonance imaging (MRI)	Nuclear magnetic resonance pattern (atomic level)
	Energy level (net magnetization) of nuclei with uneven proton and neutron number
	Longitudinal and transversal relaxation times
	Proton density
	Tissue areas or volumes depending on anatomical position and (arbitrary) signal intensities
	Regional and whole-body data
Ultrasound imaging (US)	Speed of (ultra) sound (tissue level)
	Mechanical energy level v. electrical energy level
	Signal amplitude, signal brightness
	Regional distances, areas, volumes