The use of flat panels based on amorphous silicon technology (a-Si) for digital radiography has been accepted by the medical community as having advantages over film-based systems. Radiation treatment planning employs computed tomographic (CT) data sets and projection images to delineate tumor targets and normal structures that are to be spared from radiation treatment. The accuracy of CT numbers is crucial for radiotherapy dose calculations in general but is even more important for charged particle therapy. Conventional CT scanners operating at kilovoltage X-ray energies typically exhibit significant image reconstruction artifacts in the presence of metal implants in human body. We demonstrate a significant improvement in metal artifact reductions and electron density measurements using an amorphous silicon a-Si imager obtained with an X-ray source that can operate at energies up to 1 MeV. The data collected with the higher energy system will be compared and contrasted to CT results obtained at standard kilovoltage energies.