This term applies to all changes in bone mineral density which (depending on severity) can be seen on x-rays as a change in density and or structure of the bone. Changes may affect all bones of the organism, just certain bones or only parts of bones and include decreased mineralisation as may be seen in osteoporosis or increased mineralisation and or ossification as in osteopetrosis, exostoses or any kind of atopic calicfications of different origin and distribution. The overall amount of mineralization of the bone-organ can be measured as the amount of matter per cubic centimeter of bones, usually measured by densitometry of the lumbar spine or hip. The measurements are usually reported as g/cm3 or as a Z-score (the number of standard deviations above or below the mean for the patient's age and sex). Note that measurement with this method does not reflect local changes in other bones, and as such might not be correct with regard the hole bone-organ.