Small photon fields used in conventional radiotherapy differ in many aspects from the large 10 cm x 10 cm fields used for reference dosimetry (e.g. loss of lateral charged particle equilibrium or change of spectral fluence). Therefore, a dedicated Code of Practice for dosimetry of small fields in conventional radiotherapy has recently been published.
In this work package we will provide the necessary knowledge, recommendations, methodology and data to extend this existing Code of Practice for dosimetry of small fields in conventional radiotherapy to be applicable in MRgXT and investigate its adoption in MRgPT.
This requires analysis of measurements and simulation results on field characteristics including off-axis fields. In addition, it requires a proposal on how to combine changed field characteristics in MRgXT with determined correction factors.