ESTRO 2025 - Abstract Book

S2676

Physics - Detectors, dose measurement and phantoms

ESTRO 2025

calibrated with the primary standard at the PTB, Braunschweig. The measurements were performed using a Farmer chamber (30013, PTW Dosimetry).

Results The calculated k Q,Q0 for the alanine dosimeters at 5 cm depth for the 278 and 429 MeV/u monoenergetic beams are 1.109 ± 0.047 and 1.074 ± 0.031, respectively. The resulting dose values agree with the Farmer chamber’s measurements within 1.4% and 0.4%. In the modulated beam, k Q,Q0 increases by up to 30% within the SOBP (Figure 1).

Figure 1: Computed k Q,Q0 (black circles) of the modulated beam at 5 cm depth and every 1 cm within the SOBP. The percentage depth dose curve as obtained by monte carlo simulations (orange line) is shown alongside.

Conclusion The measurements of the ionization chamber and alanine agree within their associated uncertainties. In the modulated beam, k Q,Q0 was observed to increase with the depth, especially towards the distal end of the SOBP, due to the increased average LET of the particles. This study contributes to the establishment of alanine for dose measurements in particle beams.

Keywords: Alanine, 12C, Dosimetry

References [1] H. Palmans, “Effect of alanine energy response and phantom material on depth dose measurements in ocular proton beams,” Technology in cancer research & treatment , vol. 2, no. 6, pp. 579–586, 2003. [2] J. F. Ziegler, M. D. Ziegler, and J. P. Biersack, SRIM : The Stopping and Range of Ions in Matter , Ziegler, James F., 2013. [3] M. Anton, R.-P. Kapsch, A. Krauss et al., “Difference in the relative response of the alanine dosimeter to megavoltage x-ray and electron beams,” Physics in medicine and biology , vol. 58, no. 10, pp. 3259–3282, 2013.