Quality Control and Standardisation of Absorptiometric and Computer Tomographic Measurements of Bone Mineral Mass and Density

A lack of standardisation has to be stated for quantitative assessment of bone mineral mass and density. While daily quality control is adequately provided by most manufacturers, there is a general lack of comparibility between different machines. Measurements of the same phantom or patient differ significantly. For dual X ray absorptiometry, differences of 10% or more are reported for the major manufacturers. In quantitative computer tomography, similar differences for measurements of spongiosa density have been found. While reproducibility appears adequate on both types of systems, the need for calibration standards is evident. National and international organisations have demanded standardisation efforts; an initiative started within the European Community (COMAC BME project ‘Quantitative Assessment of Osteoporosis’) appears promising. It provides anthropomorphic phantoms for spine and forearm measurements which are geometrically defined and provide definitions of the true values for all quantities to be measured. Densities and geometric dimensions span the ranges which are found in patients. These new phantoms are described in detail and compared with existing phantoms.