Selection of fat-equivalent materials in postprocessing dual-energy quantitative CT

Postprocessing dual-energy QCT is supposed to be able to predict the bone mineral more accurately than single-energy QCT. In addition, the fat content in the vertebral body can be determined. To this aim, some methods include fat-equivalent materials in the calibration device. However, the choice of an appropriate fat-equivalent material is difficult. To solve this selection problem, a method has been developed in which the x-ray interactions of tissue are characterized by three energy-independent parameters. For five different known constituents of anatomical fat, fat-equivalent materials are evaluated. It is shown that it is not possible to find one fat-equivalent material for all anatomical fat compositions. For this reason, the influence of a mismatch between the characterization parameters of anatomical fat compositions and fat-equivalent materials has been evaluated. It is shown that a mismatch in tissue characterization parameters can result in deviations of 10% in the bone mineral content and more than 300% in the estimated fat contents.