Direct determination offor Farmer-type ionization chambers in a clinical scanned carbon-ion beam using water calorimetry.

Within two studies,factors for two Farmer-type ionization chambers have been experimentally determined by means of water calorimetry in the entrance channel (EC) of a monoenergetic carbon-ion beam (Osinga-Blättermann20172033-54) and for a passively modulated spread-out Bragg peak (SOBP) (Holm2021145012). Both studies were performed at the Heidelberg Ion Beam Therapy Center (HIT) using the PTB portable water calorimeter but applying different initial beam energies of 429 MeV ufor the EC and 278 MeV ufor the SOBP as well as different scanning patterns of the irradiated field. Comparing their results revealed differences between the experimentalfactors of up to 1.

Water calorimetry-basedfactors for Farmer-type ionization chambers in the SOBP of a carbon-ion beam.

The dosimetry of carbon-ion beams based on calibrated ionization chambers (ICs) still shows a significantly higher uncertainty compared to high-energy photon beams, a fact influenced mainly by the uncertainty of the correction factor for the beam quality. Due to a lack of experimental data,factors in carbon-ion beams used today are based on theoretical calculations whose standard uncertainty is three times higher than that of photon beams. To reduce their uncertainty, in this work,factors for two ICs were determined experimentally by means of water calorimetry for the spread-out Bragg peak of a carbon-ion beam, these factors are presented here for the first time.

Triple channel analysis of Gafchromic EBT3 irradiated with clinical carbon-ion beams.

Self-developing radiochromic film is widely used in radiotherapy QA procedures. To compensate for typical film inhomogeneities, the triple channel analysis method is commonly used for photon-irradiated film. We investigated the applicability of this method for GafchromicEBT3 (Ashland) film irradiated with a clinically used carbon-ion beam.

2D range modulator for high-precision water calorimetry in scanned carbon-ion beams.

Ionization chamber-based dosimetry for carbon-ion beams still shows a significantly higher standard uncertainty than high-energy photon dosimetry. This is mainly caused by the high standard uncertainty of the correction factor for beam quality [Formula: see text]. Due to a lack of experimental data, the given values for [Formula: see text] are based on theoretical calculations.