Direct determination of < i > k < /i > < sub > Q < /sub > factors for cylindrical and plane-parallel ionization chambers in high-energy electron beams from 6 MeV to 20 MeV.
Direct determination of <i>k</i><sub>Q</sub> factors for cylindrical and plane-parallel ionization chambers in high-energy electron beams from 6 MeV to 20 MeV.
Phys Med Biol. 2018 Jan 12;:
Authors: Krauss A, Kapsch RP
Abstract
For the ionometric determination of the absorbed dose to water, Dw, in high-energy electron beams from a clinical accelerator, beam quality dependent correction factors, kQ, are required. By using a water calorimeter, these factors can be determined experimentally and potentially with lower standard uncertainties than those of the calculated kQ factors, which are tabulated in various dosimetry protocols. However, one of the challenges of water calorimetry in electron beams is the small measurement depths in water, together with the steep dose gradients present especially at lower energies. In this investigation, water calorimetry was implemented in electron beams to determine kQ factors for different types of cylindrical and plane-parallel ionization chambers (NE2561, NE2571, FC65-G, PTW34001) in 10 cm × 10 cm electron beams from 6 MeV to 20 MeV (corresponding beam quality index R50 ranging from 1.9 cm to 7.5 cm). The measurements were carried out using the linear accelerator facility of the Physikalisch-Technische Bundesanstalt (PTB). Relative standard uncertainties for the kQ factors between 0.50% for the 20 MeV beam and 0.75% for the 6 MeV beam were achieved. Within the uncertainties...
Source: Physics in Medicine and Biology - Category: Physics Authors: Krauss A, Kapsch RP Tags: Phys Med Biol Source Type: research