Energy dependence of measured CT numbers on substituted materials used for CT number calibration of radiotherapy treatment planning systems

For accurate dose calculations, it is necessary to provide a correct relationship between the
CT numbers and electron density in radiotherapy treatment planning systems (TPSs). The
purpose of this study was to investigate the energy dependence of measured CT numbers
on substituted materials used for CT number calibration of radiotherapy TPSs and the
resulting errors in the treatment planning calculation doses