Lag correction model and ghosting analysis for an indirect-conversion flat-panel imager.

Cone-beam digital tomosynthesis (CBDT) is a new approach that was recently proposed for rapid tomographic imaging of soft-tissue targets in the radiotherapy treatment room. One of the potential problems in implementing CBDT using, for example, megavoltage (MV) X rays is the possibility of artifacts caused by image lag and ghosting of the X-ray detector used. In the present work, we developed a model to correct for image lag with indirect-conversion flat-panel imagers (FPIs) used for MV-CBDT. This model is based on measurement and analysis of image lag in an indirect-conversion FPI irradiated with a 6-MV X-ray beam. Our results demonstrated that image lag is amenable to correction. In addition, we measured the ghosting effect for an indirect-conversion FPI and found it to be insignificant.