Proton beams exhibit better dose characteristics than x-rays for radiotherapy. Proton therapy is not new but has become much cheaper in the last decade. Emerging new accelerator technologies such as laser induced beams, dielectric wall accelerators and fixed field alternating gradient accelerators promise lowering costs of proton therapy even further. Increasing support from NHS for proton therapy.

In order to make the most out of this modality (highest treatment outcome with minimal side effects) dosimetric accuracy similar as in x-ray therapy is required and improved reference dosimetry is needed.