ESTRO 2024 - Abstract Book

S3315

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

The simulations of depth dose distributions with different physics lists have shown dose differences smaller than 2% , normalized on the QBBC physics list ,in the entry channel from the entrance surface up to 27.3 cm, where the reference dosimetry is usually performed. At larger depths, higher differences up to 50% can be observed especially at depths in the vicinity of the Bragg-peak. Additionally, the k Q factors of the PTW 30013 cylindrical chamber at 5cm depth calculated using the different physics lists show a maximum difference of 0.2%. Moreover, the individual perturbation factors p Q,i of the cylindrical ionization chamber are all comparable within their standard uncertainty. For the PTW 30013 chamber, the simulated k Q factors show a low energy dependence with a difference of 0.6% between 278.29 MeV/u and 429 MeV/u. Moreover, all p Q,i factors for 278.29 MeV/u and 429 MeV/u deviate from unity by 1% for the PTW 30013 chamber (see figure 1). Additionally, the differences between the individual perturbation factors for 278.29 MeV/u and 429 MeV/u are within their standard uncertainty except for p stem with a difference of 0.3%.

The simulated k Q factors for the cylindrical ionization chamber showed a deviation from values presented in the literature by 1.6% at 278.29 MeV/u and 1.2% at 429 MeV/u as shown in table 1. For the Roos chamber, the deviation is even higher, with about 3% at 429 MeV/u.