Blurring artifacts in megavoltage radiography with a flat-panel imaging system: comparison of Monte Carlo simulations with measurements.

Originally designed for use at medical-imaging x-ray energies, imaging systems comprising scintillating screens and amorphous Si detectors are also used at the megavoltage photon energies typical of portal imaging and industrial radiography. While image blur at medical-imaging x-ray energies is strongly influenced both by K-shell fluorescence and by the transport of optical photons within the scintillator layer, at higher photon energies the image blur is dominated by radiation scattered from the detector housing and internal support structures. We use Monte Carlo methods to study the blurring in a notional detector: a series of semi-infinite layers with material compositions, thicknesses, and densities similar to those of a commercially available flat-panel amorphous Si detector system comprising a protective housing, a gadolinium oxysulfide scintillator screen, and associated electronics.