Mixed beams enhance radiotherapy

The sharp distal dose fall-off of electrons in tissue makes them ideal for treating superficial targets while sparing underlying organs-at-risk (OARs). However, electrons cannot deliver homogenous dose to deep-seated targets, and the broad penumbra of electron beams means that OARs located next to the target cannot be adequately spared. Photon beams can deliver dose conformally to targets at all depths and efficiently spare nearby OARs. But, in contrast to electrons, photons deliver a low-dose bath over a large volume of normal tissue. Mixed-beam radiotherapy (MBRT) could combine the best of both worlds.
Medical Physics Web