ESTRO 2023 - Abstract Book

S1414

Digital Posters

ESTRO 2023

Results The comparison between Radcalc and QA measurement results show a good agreement for the patients considered except for a few points issue solved using Acuros XB, Figure 2. For the brain case, the comparison between RadCalc and QA measurement results show a good agreement for most of the patient. Radcalc DVHs dosimetric agreement between simulated Monte Carlo and baseline TPS measurements show a median dose percentage difference up to 7% for the target tumor and a maximum dose percentage difference up to 10% for the organs at risk (i.e., Spinal Cord 6%, Stomach 8%, Lungs 10%).

Conclusion Radcalc Monte Carlo, tuned as descripted, allows to independently verify treatment plans directly on patient CT scans with a dosimetric agreement similar to those achieved on phantom used for patient-specific QA and to find TPS algorithms inaccuracies due to tissue inhomogeneities, issue not estimable by QA measurements with uniform phantoms.

PO-1703 Impact of Gun Grid Voltage on beam characteristics for a 1.5T Unity MRLinac

T. Foppen 1 , S. Woodings 1 , W. de Vries 1 , A. Wopereis 1 , J. Wolthaus 1

1 UMC Utrecht, Radiotherapy, Utrecht, The Netherlands

Purpose or Objective A gun grid (GG) can be used in order to adjust the number of electrons that are released from an electron gun into the waveguide. Having a higher anode voltage means that more electrons are released. Changing GG voltage affects the beam energy and output as more electrons means a lower mean energy per electron. Therefore, the energy can be controlled