Image quality and dose of an accelerator-integrated kV CBCT systems

Abstract

The ability of an imaging modality to precisely determine patient anatomy and provide reliable information about tumor position is critical in the radiotherapy process. As image-guided radiotherapy (IGRT) becomes more popular in radiation treatment, its overall quality and performance, such as the image quality and amount of dose delivered, need to be assessed. The research described in this dissertation was focused on investigation of the image quality of the planar and cone-beam computed tomography (CBCT) images of two imaging systems commonly used in radiotherapy: Varian On-Board Imager (OBI) and Elekta X-ray Volumetric Imager (XVI). Several imaging quality tests were performed using current clinical imaging protocols provided with both systems and various types of image quality phantoms. CBCT imaging dose of each system was also estimated using standard CT dose index (CTDI) phantoms and several imaging protocols. Overall, the image quality between the OBI and XVI was fairly consistent with each other with the exception of high contrast resolution and Hounsfield Unit (HU) accuracy. CTDI of OBI was higher than that of XVI which was related to the different designs and imaging protocols between the two systems.