Dose calculation algorithms in commercial Treatment Planning Systems (TPS) rely heavily on the accuracy of the underlying beam model and of the measured dosimetrical input data that is fed into this beam model. Furthermore, in the commissioning and acceptance phase of new radiotherapy equipment, hospitals need to perform measurements to assess the accuracy of the dose algorithm in well-defined radiation fields. In addition, quality assurance (QA) of the linac facility is essential to ensure accurate dose delivery to the patient and to minimise the possibility of accidental exposure.
The overall aim of work package 2 is to develop methodologies for the accurate measurement of TPS input for MR guided radiotherapy (MRgRT) as well as for machine measurements for QA for wich both the geometrical and the dosimetrical uncertainties are relevant. Target uncertainties for both vary among the different types of measurement (Percentage Depth Dose (PDD), penumbra, etc.) and should at least be in line with the acceptability criteria for the determination of radiation beam characteristics, and TPS dose calculations published for conventional radiotherapy.
This includes the characterisation of the suitability of commercially available point detector systems for the measurement of input data in the presence of the magnetic field and the characterisation of 2D and 3D dose mapping systems for machine QA measurements. An essential aspect is input from WP3 based on highly accurate Monte Carlo calculations of dose distributions and detector response in combination with the measurements performed in WP2. A selection of detector systems for the measurements will be drafted on the basis of these findings.