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A scanner used to measure bone density using dual energy X-ray absorptiometry. Bone density, or bone mineral density, is the amount of bone mineral in bone tissue.The concept is of mass of mineral per volume of bone (relating to density in the physics sense), although clinically it is measured by proxy according to optical density per square centimetre of bone surface upon imaging. [1]
Wolff's law, developed by the German anatomist and surgeon Julius Wolff (1836–1902) in the 19th century, states that bone in a healthy animal will adapt to the loads under which it is placed. [1] If loading on a particular bone increases, the bone will remodel itself over time to become stronger to resist that sort of loading.
Peak bone mass is the maximum amount of bone a person has during their life. [1] It typically occurs in the early 20s in females and late 20s in males. [ 2 ] Peak bone mass is typically lower in females than males, and is also lower in White people and Asians compared to black populations. [ 1 ]
Bone densities are often given to patients as a T score or a Z score. A T score tells the patient what their bone mineral density is in comparison to a young adult of the same gender with peak bone mineral density. A normal T score is -1.0 and above, low bone density is between -1.0 and -2.5, and osteoporosis is -2.5 and lower.
DXA is only able to provide the areal bone mineral density. High-resolution peripheral quantitative computed tomography (HR-pQCT) is better than DXA at detecting bone microarchitecture, modeling whole-bone geometry using 3-dimensional information from scans. This method allows estimation of bone strength and other mechanical properties. [20]
Irrespective of the location from which they are obtained, the fat cells in humans are composed almost entirely of pure triglycerides with an average density of about 0.9 kilograms per litre. Most modern body composition laboratories today use the value of 1.1 kilograms per litre for the density of the "fat free mass". [8]
A wide variety of body composition measurement methods exist. The gold standard measurement technique for the 4-compartment model consists of a weight measurement, body density measurement using hydrostatic weighing or air displacement plethysmography, total body water calculation using isotope dilution analysis, and mineral content measurement by dual-energy X-ray absorptiometry (DEXA). [1]
Digital X-ray radiogrammetry is a method for measuring bone mineral density (BMD). Digital X-ray radiogrammetry is based on the old technique of radiogrammetry.In DXR, the cortical thickness of the three middle metacarpal bones of the hand is measured in a digital X-ray image. [1]