Energy dependence of contrast-detail-dose and object-detectability-dose curves for CT scanners

The energy dependence of contrast-detail-dose (CdD) and object-detectability-dose (OdD) curves for computed tomographic scanners is investigated. The effects of changes in beam energy on perceptibility are shown to be due to changes in signal-to-noise ratio resulting from changes in contrast and photon statistics. Energy-dependence analysis of OdD curves is shown to depend on the atomic composition of the phantom used to generate the curves, while such an analysis of CdD curves is independent of the atomic composition of the phantom. It is also shown that any OdD curve can be generated from CdD curves and that use of this fact rectifies any potential energy-dependent interpretation of CdD curves.