Dose discrepancies between Monte Carlo calculations and measurements in the buildup region for a high‐energy photon beam

This study investigates a possible cause of reported significant dose discrepancies between Monte Carlo calculations and measurements in the buildup region for high-energy photon beams in large fields. A proposed hypothesis was that the discrepancy was caused by a source of electrons in the accelerator head that was not fully accounted for in the treatment head simulation. In this investigation, a lead foil is added just below the accelerator...