ESTRO 2024 - Abstract Book

S3379

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Energy MeV/u

in

This study

Holm et al. [4]

Difference in %

This study

Holm et al. [4]

Difference in %

278 429

1.029(17) 1.031(17) 1.041(17)

1.012(7) 1.022(8) 1.016(7)

1.7 0.9 2.4

1.030(17) 1.031(17) 1.038(17)

1.013(7) 1.020(8) 1.018(7)

1.6 1.1 2.0

SOBP

The investigation of dose fractions showed that, besides 12 C, especially 1 H, 4 He, 11 B and 11 C contribute to the dose at the measurement depth. In figure 1, the corresponding spectral fluences of these particles are shown.

Figure 1: Spectral fluences of 1 H, 4 He, 11 B and 11 C at the measurement depth in a 429 MeV/u carbon ion beam.

Conclusion:

k Q factors in clinical carbon ion beams for four cylindrical and six plane-parallel ionization chambers have been calculated with the Monte Carlo code FLUKA. The calculated factors agree with values from the literature within 2.4% or better for monoenergetic and modulated beams. At the measurement depth, 1 H, 4 He, 11 B and 11 C contribute significantly to the deposited dose.

Keywords: beam quality correction, carbon ion, Monte Carlo

References:

[1] Andreo, P. et al.: Absorbed dose determination in external beam radiotherapy: An international code of practice for dosimetry based on standards of absorbed dose to water, 2000, Technical Report Series TRS-398 (International Atomic Agency, Vienna)

[2] Palmans, H. et al.: Current best estimates of beam quality correction factors for reference dosimetry of clinical proton beams, 2022, Physics in Medicine & Biology 67

[3] Baumann, K.-S. et al.: Monte Carlo calculated ionization chamber correction factors in clinical proton beams – deriving uncertainties from published data, 2023, Physica Medica 113